4. Fishing methods and equipment
Fisheries and Aquaculture
Stündl, László
Created by XMLmind XSL-FO Converter .
Fisheries and Aquaculture
Stündl, László
TÁMOP-4.1.2.A/1-11/1-2011-0009
University of Debrecen, Service Sciences Methodology Centre
Debrecen, 2013.
Created by XMLmind XSL-FO Converter .
Tartalom
1.1. 6.1.1. Reconstruction/development of spawning grounds ...................................... 47
iii
Created by XMLmind XSL-FO Converter .
Fisheries and Aquaculture
iv
Created by XMLmind XSL-FO Converter .
Fisheries and Aquaculture
3. 13.3. „Aranyponty” Fish Farm as an example of multifunctional pond fish farms ........... 120
v
Created by XMLmind XSL-FO Converter .
Az ábrák listája
5.4. Picture 5.6: John Day Dam fish ladder on the Columbia River, North America(Source: US Army
6.4. Figure 6.4: Example of an integrated runoff management project (comlex habitat development) 50
vi
Created by XMLmind XSL-FO Converter .
Fisheries and Aquaculture
90
12.3. Figure 12.3: Various seeweed grown in bi-culture to mitigate negative environmental impact 108
vii
Created by XMLmind XSL-FO Converter .
A táblázatok listája
9.1. Table 9.1: Recommended Protein Levels in Percent of Practical Fish Diets (As-Fed Basis) .... 76
viii
Created by XMLmind XSL-FO Converter .
Tárgymutató
1
Created by XMLmind XSL-FO Converter .
1. fejezet - 1. Current status and tendencies in fisheries and aquaculture
1. 1.1. Significance of aquaculture and fisheries
Capture fisheries and aquaculture supplied the world with about 142 million tonnesof fish in 2008. Ofthis, 115 million tonnes was used as human food, providing an estimated apparent percapita supply of about 17 kg (live weight equivalent), which is an all-time high. Aquaculture accounted for 46 percent of total food fish supply, a slightlylower proportion than reported in The State of World Fisheries and Aquaculture 2008owing to a major downward revision of aquaculture and capture fishery productionstatistics by China.Fish and other aquatic products account for 17% of the total protein consumption of the World, so this can be considered as basic foodstuff, moreover it is the major protein source for several regions. There are huge variations in per capita consumption, in some countries is very high: e.g. Japan ~70 kg, or Portugal ~60kg.
One reasons for the increasing consumption inthe developed countries that fish can fit well into the healthy lifestyle, having high biological value, easy digestibility due to high water content and being rich in unsaturated fatty acids (PUFA).
The main forms of fish production are fisheries and aquaculture, both are producing in marine-brackish- or inland (freshwater) circumstances.
1.1. ábra - Table 1.1: Fish production and use
2. 1.2. Fish consumption and use
2
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
2.1. 1.2.1. Human consumption
In 2007, fish accounted for15.7 percent of the global population’s intake of animal protein and 6.1 percent ofall protein consumed. Globally, fish provides more than 1.5 billion people with almost20 percent of their average per capita intake of animal protein, and 3.0 billion peoplewith at least 15 percent of such protein. In 2007, the average annual per capita apparent fish supply in developing countries was 15.1 kg, and 14.4 kg in lowincomefood-deficit countries (LIFDCs). In LIFDCs, which have a relatively low consumption ofanimal protein, the contribution of fish to total animal protein intake was significant –at 20.1 percent – and is probably higher than that indicated by official statistics in viewof the underrecorded contribution of small-scale and subsistence fisheries.
The fishery sector plays a key role in food security, not only for subsistence and smallscale fishers who rely directly on fishery for food, incomes and services, but also for consumers who profit from an excellent source of affordable high-quality animal protein. A portion of 150 g of fish12 provides about 50–60 percent of the daily protein requirements for an adult. Fish is also a source of essential micronutrients, including various vitamins and minerals. With a few exceptions for selected species, fish is usually low in saturated fats, carbohydrates and cholesterol.
In terms of a world average, the contribution of fish to calories is rather low at 30.5 calories per capita per day
(2007 data). However, it can reach 170 calories per capita per day in countries where there is a lack of alternative protein food and where a preference for fish has been developed and maintained (e.g. Iceland, Japan and several small island states).
1.2. ábra - Figure 1.1: Relative contribution of aquaculture and capture fisheries to food fish consumption
Total and per capita fish food supplies have expanded significantly in the last five decades. Total food fish supply has increased at an annual rate of 3.1 percent since 1961, while the world population has increased by 1.7 percent per year in the same period. Annual per capita fish consumption grew from an average of 9.9 kg in the
1960s to 11.5 kg in the 1970s, 12.6 kg in the 1980s, 14.4 kg in the 1990s and reached 17.0 kg in 2007.
Preliminary estimates for 2008 indicate a further increase in annual per capita consumption to about 17.1 kg. In
2009, as a consequence of uncertain economic conditions, demand remained rather sluggish and per capita consumption is expected to have remained stable.
2.2. 1.2.2. Use for feeding
Fishmeal: Catches for reduction purposes have been declining continuously in recent years. However, fishmeal production has remained stable as more fishmeal is produced from offal derived from the fish processing industry. Demand for fishmeal was strong in 2009, leading to sharply higher fishmeal prices in that year. China remains the main market for fishmeal.
Fish oil: In 2009, total fish oil production by the five main exporting countries (Peru, Chile, Iceland, Norway and Denmark) was 530 000 tonnes, a decline of 100 000 tonnes compared with 2008. Fish-oil prices reached
3
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
US$950/tonne in March 2010, which was 50 percent higher than a year earlier (Figure 31). For fish oil, the share going to aquaculture is even greater than for fishmeal, with almost 85 percent of production being used as an ingredient in fish and shrimp feeds.
1.3. ábra - Figure 1.2:Total fish production by species groups
3. 1.3. Fisheries production
3.1. 1.3.1. Marine fisheries
The dominant species in marine fishery catches have been the same since 2003 and only a few changes in the ranking have occurred in the last six years, another sign of a relative stability. The share of the top ten species in global marine catches has varied little, oscillating between 29 and 33 percent. However, there are differences among the trend trajectories of the various species groups and the most striking are described below.
3.2. 1.3.2. Inland fisheries
Global inland capture fisheries production was fairly stable between 2000 and 2004 at about 8.6 million tonnes, but in the following four years it showed an overall increase of 1.6 million tonnes, reaching 10.2 million tonnes in 2008. Asia accounted for two-thirds of the world production.
Inland water fishing is often a subsistence or recreational activity with fishing sites geographically scattered, making gathering information very difficult. In many countries, national administrations do not manage to secure adequate funding for the collection of reliable inland catch statistics. About one-third of the countries do not submit any information on inland waters catch statistics, forcing FAO to estimate the national production.
1.4. ábra - Figure 1.3: Catch statistics of major fisheries species
4
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
Currently, too many fish stocks are still exploited at levels in excess of their maximum sustainable yield, in other words the optimal volume of catches that can be taken each year without threatening the future reproductive capacity of a fish stock.
4. 1.4. Aquaculture production
Aquaculture remains a growing, vibrant and important production sector for highprotein food. The reported global production of food fish from aquaculture, including finfishes, crustaceans, molluscs and other aquatic animals for human consumption, reached 52.5 million tonnes in 2008. The contribution of aquaculture to the total production of capture fisheries and aquaculture continued to grow, rising from 34.5 percent in 2006 to 36.9 percent in 2008. In the period 1970–2008, the production of food fish from aquaculture increased at an average annual rate of 8.3 percent, while the world population grew at an average of 1.6 percent per year. The combined result of development in aquaculture worldwide and the expansion in global population is that the average annual per capita supply of food fish from aquaculture for human consumption has increased by ten times, from
0.7 kg in 1970 to 7.8 kg in 2008, at an average rate of 6.6 percent per year.
1.5. ábra - Figure 1.4: Aquaculture production
5
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
Growth rates for aquaculture production are slowing, reflecting the impacts of a wide range of factors, and vary greatly among regions. Latin America and the Caribbean showed the highest average annual growth in the period 1970–2008 (21.1 percent), followed by the Near East (14.1 percent) and Africa (12.6 percent). China’s aquaculture production increased at an average annual growth rate of 10.4 percent in the period 1970–2008, but in the new millennium it has declined to 5.4 percent, which is significantly lower than in the 1980s (17.3 percent) and 1990s (12.7 percent). The average annual growth in aquaculture production in Europe and North
America since 2000 has also slowed substantially to 1.7 percent and 1.2 percent, respectively. The once-leading countries in aquaculture development such as France, Japan and Spain have shown falling production in the past decade. It is expected that, while world aquaculture production will continue to grow in the coming decade, the rate of increase in most regions will slow.
1.6. ábra - Figure 1.5: Trend sin aquaculture and fisheries production
6
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
Most common types of aquaculture are:
Extensive fresh water aquaculture: Ponds are maintained in such a way as to promote the development of aquatic fauna at a yield greater than that found in the natural ecosystem. Density is low and fish feed naturally.
Certain producers provide additional feed. These ponds play an important and positive role in the landscape, water management and biodiversity. Examples – Carp, in mixed farming with other species (whitefish, zander, pike, catfish, etc.).
Aquaculture of marine species in shore-based installations: Marine fishes (particularly flatfishes) can also be bred in artificial shore-based tanks supplied with seawater. Recirculation of the water creates a closed and controlled environment that is necessary for optimal production in hatcheries and nurseries for marine species.
Examples – Turbot, common sole, Senegalese sole, sea perch, gilt-head sea bream.
Extensive brackish water aquaculture: The animals (often brought in by the marine flow) are kept in lagoons developed for this purpose (ex.: Italian valliculture, Spanish esteros). The semi-extensive nature of this breeding is reinforced by introducing hatchery fry and providing additional feed. This type of aquaculture plays an important role in conservation of the natural coastal heritage. Examples – Sea perch, eel, common sole,
Senegalese sole, sea bream, mullet, sturgeon, shrimps and shellfish.
1.7. ábra - Figure 1.6: Production statistics of major aquaculture species
7
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
Intensive fresh water aquaculture: In intensive systems, fish are bred in tanks until they reach marketable size. There are two techniques: continuous flow (river water enters tanks upstream and leaves downstream) and recirculation (the water remains in a closed circuit and is recycled and ‘recirculated’ in the tanks). Recirculation systems are more costly (energy), but offer better control of breeding conditions (temperature and oxygen) and water quality. Examples – Rainbow trout, eel, catfish, sturgeon, tilapia, etc.
Marine cage aquaculture: The fish are kept in cages anchored to the seabed and maintained on the surface by means of a floating plastic framework. This form of breeding is practiced mainly in sheltered zones near shore, but more sophisticated techniques (submersible cages, remote monitoring, automatic feeding, etc.) may make it possible to move further from shore. Examples – Atlantic salmon, sea perch, sea bream, meagre, etc.
Shellfish farming: Shellfish farming is based on the collection of wild or hatchery spat, which feed on natural nutrients found in the environment (filter-feeding animals). Oyster and mussel farming account for 90 % of
European production and use a wide range of techniques: bottom-farming, on tables, wooden posts, ropes, etc.
Examples – Oysters (oyster farming), mussels (mussel farming), clams and abalones.
5. 1.5. Fish production in Europe
EU fish production (2010) is approximately 6,6 million tons/year, of which 5.3 mill. tons capture fisheries
(TOP5: Spain, Denmark, France, UK, The Netherlands) and 1.3 mill. tons aquaculture. The market demand is app. 10 milion tons per year, so Europe is net importer from fish and other quatic commodities.
1.8. ábra - Figure 1.7: The European fish production
8
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
The European Union accounts for just under 6 % of total fisheries production worldwide, with a reduction in volume compared to previous years. Although the European fleet operates worldwide, EU catches are taken primarily in the Eastern Atlantic and the Mediterranean. They are mainly made up of sprat, herring and mackerel. The leading fishing countries are Denmark, Spain, the United Kingdom and France, which together account for around half the catches.
Aquaculture is a major activity in many European regions. Aquaculture production in the European Union is in the region of 1.3 million tonnes, while its value amounts to € 3.2 billion. This represents 20.4 % of the total volume of EU fisheries production. Its share of total world aquaculture production is 2.3 % in terms of volume and 4 % in terms of value.
The European Union represents about 4.4 % of global fisheries and aquaculture production, which makes it the fifth producer worldwide. As has been the case each year for the last 20 years, total European Union production decreased slightly compared to previous years. Within the EU, the three largest producers in terms of volume are Spain, Denmark and the United Kingdom.
1.9. ábra - Figure 1.8: The European aquaculture production
9
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
The EU is net importer, from 2002 to 2007: deficit grew from 2,5 million tons to 3,5 million tons. EU highest dependency of imports ever!EU (27) import from fisheries and aquaculture products: 8,9 million tons, over 5 million tons import from 3. countries, Major countries of import: Norway, China and Vietnam (Vietnam export grew from 32 t tons to 256 t tons between 2002-2007) Market expansion overgrew the price increase in the past years, the average import prices grew by 50% during the past 5 years
The Common Fisheries Policy aims to reduce the negative impacts of fisheries on the environment and develop an integrated approach for the protection of the ecological balance of our oceans as a sustainable source of wealth and well-being for future generations. Various actions have been taken, particularly to protect endangered species such as sharks, cetaceans and essential elements of marine ecosystems, such as certain seabed habitats.
These actions contribute to the objectives of European environmental policy, particularly in the context of the
Marine Strategy Framework Directive, the environmental pillar of the European Union’s maritime policy. They are complemented by protection measures put in place under regional fisheries or environmental agreements applicable in European waters.
Fishery and aquaculture products play a significant role in human diet, both in Europe and worldwide, as a source of protein-rich healthy food. Worldwide, the consumption of these products represents 17.8 kg/person/year or 15.7 % of animal protein intake. Within the European Union, the average consumption of fish is 23.3 kg/person/year. Consumption varies from 4.6 kg/person/year in Bulgaria to 61.6 kg/person/year in
Portugal.
1.10. ábra - Figure 1.9: Per capita fish consumption in the EU
10
Created by XMLmind XSL-FO Converter .
1. Current status and tendencies in fisheries and aquaculture
General consumption trends for the EU-15 countries reflect an increase in consumption ofseafood products. This rise is supported by a rise in consumption of convenience products asconsumers have less and less time to spare for meal preparation. Frozen products tend to beon a downward trend whilst the consumption of fresh fish stagnates or decreases. The risingshare of supermarkets in the retail of seafood products also increases their availability, whichleads to increased consumption. Healthy eating, triggered by various food crises (e.g.
BSE,dioxin, etc.) is another determinant of the positive trend of seafood consumption.Future trends: species consumed in 2030 will be more or less the same as today since all the importantstocks of fish in the world are already exploited. Some marine species may be produced byaquaculture, for example cod or other demersal species, but it will be more a shift in theproduction system than an introduction of new species. Deep-sea fishing, where a lot of hopesresided, has already shown its limitations.
Overall, the main group of species consumed in 2030 will be the same as in 1998.Furthermore, these groups will compose about the same share of the total species consumed.Demersal marine fish such as cod, Alaska pollock and hake will dominate white fishconsumption. Groundfish will represent about 40 percent of the total fish consumed in EUR-28 (taking into account other marine fish, which are mainly demersal fish used as rawmaterial in prepared commodities). EUR-28 consumers will eat about 9 kg/c/yr of demersalfish in 2030.
11
Created by XMLmind XSL-FO Converter .
2. fejezet - 2. Aquatic resources and aquatic species
An aquatic ecosystem is an ecosystem located in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic eco-systems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.
1. 2.1. Aquatic ecosystems and biomes
Marine ecosystems account for71% of the Earth's surface and contain app. 97% of the planet's water, where
32% of the world's net primary production takes place. The typical zones of this ecosystem are: oceanic (incl. continental shelf); profundal (bottom or deep water); benthic (bottom substrates); intertidal (the area between high and low tides); estuaries; salt marshes; coral reefs; and hydrothermal vents (where chemosynthetic sulphur bacteria form the food base).
2.1. ábra - Picture 2.1: Examples of marine ecosystems (from left to right: coral reefs,intertidal, salt marshes, estuaries and hydrothermal vents)
Freshwater ecosystems are significantly smaller than marine, only 0.80% of the Earth's surface and 0.009% of total water, with only 3% of its net primary production. However they are significant for fish production because they contain 41% of the world's known fish species. The basic types Lentic (pools, ponds, lakes) Lotic (streams, rivers) Wetlands (saturated or inundated soil).
2.2. ábra - Picture 2.2: Examples of freshwater ecosystems (from left to right: ponds/lakes, streams, wetlands and water reservoirs)
Zones: pelagic (open offshore waters); profundal; littoral (nearshore shallow waters); and riparian (the area of land bordering a body of water). Two important subclasses of lakes are ponds, which typically are small lakes intergrade with wetlands, and water reservoirs.
2.3. ábra - Picture 2.3: Zones of a freshwater lake
12
Created by XMLmind XSL-FO Converter .
2. Aquatic resources and aquatic species
2. 2.2. Aquatic habitats and communities
Plant and animal organisms living in the water have a strong metabolism in relation to their surroundings. The habitat and its environment create a unit, which is in a dynamic balance. The environment can be divided into living and inert parts. For the autotroph organisms the inert and for the heterotroph organisms the living and the inert surroundings together provide the conditions necessary to stay alive. The living environment for a certain organism consists of all the other living organisms together. The living organisms take up nutrients from their environment and they void their excrements to there, and after their death their bodies are decomposed at that place, too. Therefore, creatures have a specific reaction on their environment.
Different areas in the water body provide survival conditions for different organisms and groups of organisms.
Parts in the body of water with the same environmental conditions are called habitats, and all the creatures living there are called associations of the living organisms. Stagnant water has three basic habitats:
• inshore zone
• open water
• pond bottom
Characteristics of the inshore zone are the flat water and the floral vegetation, which is often closed. In the shores, water damages the dams against the prevailing wind, whereas the sheltered inshore zone banked up by alluvial deposits. In fish ponds the flora of the inshore zone is chiefly made up of reeds, sedges, bulrushes and reed-grasses. The fauna of this habitat is composed by variable species. Single-celled organisms, Rotifers, as well as different water-beetles, reptiles, amphibians and fishes can be found here. The bed of the inshore zone is full of shellfish, snails and larvae.
Characteristics of the open water are the greater water depth and the lack of floral vegetation. Many communities in this area are formed by plankton, other words living organisms that float in the water. This specific group of organisms contains algae (phytoplankton) and mainly lower-level crustaceans and Rotifers
(zooplankton) provide the greater part of the whole aquatic production. The quantity and quality of plankton essentially affect the success of fish meat production. The communities involve the swimming (nektonic) organisms, above all the open water fish.
The open water habitat that is most favourable for production biology can only be sustained artificially in the
0.8-1.5 m deep water of fish ponds. On the other hand, in the flat water the floral vegetation quickly spreads and without controlling the swamp vegetation will become dominant in the ponds in a few years. At the same time conditions for fish meat production will get worse.According to the level/intensity of production, the pelagic region of the aquatic biome can be divided into two basic layers (also referred to as stratification):
• photic zone - light sufficient for photosynthesis
13
Created by XMLmind XSL-FO Converter .
2. Aquatic resources and aquatic species
• aphotic zone - light insufficient for photosynthesis
The third basic habitat, which provides specific environmental conditions is the lake/pond bottom. Its circumstances are influenced by the geological, structural and chemical characteristics of the sediment as well as its interactions with water and the dissolved materials in the water. The community in this habitat is called benthos, which is created by algae, bacteria, single-celled organisms, worms, crustaceans, shellfish and insect larvae.
In a longer period a silt layer is created from the organic and non-organic materials on the lake bottom. Much of this originates from the decomposition of the dead organisms in the pond. The breaking down process of organic matter in the silt deprives much of the oxygen from the water. If the oxygen supply is not regular, anaerobic breaking down processes starts functioning and producing harmful gases, the deposition of the silt increases and the living organisms on the lake bottom get in danger.
2.4. ábra - Picture 2.4: Zones of a freshwater lake
The habitat and the niche form a self-supporting higher-level biological organisation, which operates by its own principles. The survival of the whole system as well as the organisms in this system is dependent upon the undisturbed operation of the life forms. If the survival conditions do not change significantly, the niche is biologically balanced. However, the survival conditions often change and they can be altered by human interactions. In this case the quantity and the quality of the niche are changed and a new biological balance keeping with the changed circumstances will be created. In the point of view of production management this can be advantageous and disadvantageous, too.
3. 2.3. Applied hydrobiology - production biology
Niches in different habitats in the fishpond are connected with each other and they together form the niche of the whole pond. One of the disciplines of biology, the recently developed production biology deals with the principals of material- and energy-circulation in such huge systems. According to production biology creatures can be divided into three groups:
• constructive organisms(producers)
• storing organisms (consumers)
• decomposing organisms (decomposers)
Constructive organisms (producers) - in other words plants - build up organic matter by combining water, carbon dioxide and other inorganic materials with the energy from sunlight. In the course of this process oxygen is released. Plants, as they are autotrophic organisms, transform the energy of sunlight into chemical energy when building up organic materials. The most important plants in the water are the single-celled algae, which build up the greater amount of organic matter. The floral aquatic plants build up smaller amount of organic
14
Created by XMLmind XSL-FO Converter .
2. Aquatic resources and aquatic species matter, and, on the other hand it can be utilized on a lower degree. The amount of the production by plants is affected by the environmental conditions, and primarily by the amount of the useful nutrients.
Organic matter produced by plants provides the basis for the heterotrophic animal kingdom. Animals are called storing organisms (consumers). In the point of view of production biology their role is to store the organic matter produced by plants as the material of their own body. Animals can be divided into the groups of herbivorous and carnivorous animals. The latter indirectly obtain the organic materials built up by plants.
An important group of storing organisms is formed by animals mainly living on the bottom of the pond, which feed on the remains of dead organisms. These animals safe back the organic matter before decomposition and make it alive again for the niche. The amount and composition of the aquatic species are primarily dependent upon the available nutrients from plants.
The group of the decomposing organisms (decomposers) contain bacteria and fungi. They break down the perished organic matter, which is not eaten by the saving back organisms into water, carbon dioxide and mineral substances while releasing oxygen. These materials take part in the process of building up organic matter by plants again.Due to the function of the decomposing organisms the material-circulation becomes complete.
Aquatic biomes can be subdivided by productivity to three categories:
• oligotrophic - deep, nutrient poor, water very clear
• eutrophic - shallower, nutrient rich, murky with phytoplankton
• mesotrophic - in between the above two classifications
2.5. ábra - Picture 2.5: Example of an oligotrophic (left) and an eutrophic (rignt) biome
Groups of creatures, which implement the material- and energy-circulation are in a connection in their feeding, so they jointly form the food chainor– since the interconnections are more complicated – a food web. Groups of organisms, which serve as food, and other groups of organisms, which eat these groups form the direct elements of the food chain.Plants produce living organic matter from sun light energy and dissolved materials. This is fed on by plant-eating animals, which serve as nutrients for other groups of animals. At the end of the food chain there are the greatest predators.
2.6. ábra - Picture 2.6: Typical groups of aquatic organisms
15
Created by XMLmind XSL-FO Converter .
2. Aquatic resources and aquatic species
According to the production biology groups of animals built on top of the other m such way can be classed into feeding levels. Each level covers a certain quantity and quality of energy, so that we can speak about feeding and energy levels at the same time.Starting with plants producing organic matter, the higher the level, the lower the number of individuals in a given species as well as the amount of the organic material contained by the level.
This is because the amount of the organisms on a given level cannot be totally fed on by the creatures on the next level.
2.7. ábra - Picture 2.7: Example of a food web
Meanwhile a part of them dies, and the amount from this the so called saving back organisms cannot reutilize is broken down into inorganic materials.The higher the level, the lower the amount of energy. This is because it is built up into the creatures of the next level as potential energy. The remaining part of the energy is used up in the metabolism of the living organisms or wasted in the decomposition of dead organic matter.The principles of the material- and energy-circulation can be most easily demonstrated by the Elton's pyramid.
On the basis of the above mentioned facts it can be stated that circulation of the organic material and its energy content among the groups of organisms can be carried out only at the expense of the high level of losses.Materials necessary to build up organic matter are in a continuous circulation, and, on the other hand the energy fixed in the process of photosynthesis goes along the food chain only once.The whole niche of the pond is a continuously operating biological system. The intensity of the operation, the composition of the niche, the amount of the circulating materials and energy are dependent upon the environmental conditions.
2.8. ábra - Picture 2.8: Elton’s pyramidin a freshwater lake
16
Created by XMLmind XSL-FO Converter .
2. Aquatic resources and aquatic species
According to human purposes the environment can be changed more or less. Minimum factors can be determined, which decrease the biological production. These factors can have physical, chemical, biological and climatic origins. Nowadays in the practice of fish farming the physical factors (e.g. the structure of the sediment) and the climatic factors (e.g. temperature and light) can only be hardly changed.
There are more possibilities to intervene in the chemical and biological factors with success. Artificially filling in the gaps of chemical materials can significantly increase plant production and through this the amount of organisations on the higher level. Better feeding conditions cause changes in the rate between taxonomic groups of the aquatic life world.It can be achieved that the increased biological production to be utilised on an optimum level by controlling the quantity and the quality of fish stock keeping with the available natural nutrients.
Suitable fish stocking significantly affect the whole aquatic niche. By feeding the fish stock continuously decreases the populations of the organisation-groups below, and by this, it provides better conditions for the survival groups. For this, the survival population reacts with an increasing gam in weight and a more intensive reproduction. Consequently, the material- and energy circulation become faster and the efficiency of the production of the biological system is improved.
17
Created by XMLmind XSL-FO Converter .
3. fejezet - 3. Fish population ecology, stock assessment and management
1. 3.1. Inland fisheries management
Conventionally the objective for fisheries management has been just to maintain the sustainable yield by preventing resource deterioration and decline of yields from the achieved average level. Management is viewed as a holding action against the forces of resource depletion. Most resource management in this century has been based on the implicit assumption that regulation and enhancement of biological harvest will also lead to economic well-being. In practice, fisheries management and fisheries development in particular often aim at increased fish yields and enhanced availability of products for the consumption, although the more productive current regime may result in some unexpected ecological and economical disasters in the future. In this chapter we discuss the multidisciplinary view in fisheries management that considers both environmental and ecological as well as the economic goals in the individual harvester's and the entire fisher community point of view. We emphasise the means to take into account the short-term and long-term perspectives in this process and the expectations of various target groups that play role in today's fishery society.
Definitions of fisheries management:
A) Manipulation of aquatic organisms, aquatic environments, and their human users to produce sustained and ever-increasing benefitsfor people (Nielsen)
B) The integration of ecological, economic, political, and socio-cultural information into decision making that result in the implementation of actions to achieve goals established for fish resources (Krueger and Decker)
3.1. ábra - Figure 3.1: Fisheries landings by area and species groups
2. 3.2. The need for management
In most fisheries, the need to control exploitation through management has become clear over time for several principal reasons: a.
fish stocks are depletable, but have the potential to be driven to extinction if exploitation is uncontrolled.
This is typically the risk in open-access fisheries where the fishery resources are not restricted to certain owner group but are regarded as common property. Today, signs of depleted fish stocks due to over-
18
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management exploitation can be found almost in every major marine fishery (FAO statistics) and the fare of reduced future yields is usually the first concern in any local conflict be it in the open sea, coastal zones or inland waters.
b.
conflicting biological, social, economic and cultural goals inherent in most fisheries must be balanced through management, c.
controls are needed over the rate of fish stock exploitation, to balance present-day needs with maintenance of the resource at suitable levels for future use.
3. 3.3. Objectives of the management
3.1. 3.3.1. Ecological sustainability
The most crucial component of ecological sustainability involves (a) maintaining individual stocks and species at level that do not foreclose future options, and (b) maintaining or enhancing the capacity and quality of the ecosystem.
Key criteria:
• will the exploitation levels on the impacted species remain sustainable
• are indirect biological impacts understood and recognised
The basic fact behind the managerial decisions, which one cannot deny, is that fish stocks are not infinitely renewable. Therefore the fundamental question usually is: How much fish can be harvested from the sea or lake without being detrimental to fishing in future years? This question has been addressed over the past several centuries, and has been developed into the concept of the "sustainable yield" as the first attempt to formulate the scientific basis for fisheries management. Sustainable yield is an allowable annual harvest which, even if repeated indefinitely into the future, would not lead to excessive depletion of the fish stock.
To support the managerial decisions, the fisheries scientists have developed a wide variety of tools to determine sustainable yields, and the corresponding level of fishing effort that can be allowed without over-harvesting the stocks. The simplest, and most-used graph to illustrate this relationship showing how any given annual level of constant fishing effort, will produce a certain sustainable yield from the fishery
In practice, the most commonly set goal for fisheries is the level of fishing effort that gives the "Maximum
Sustainable Yield" (MSY), the largest annual catch that can be taken while maintaining resource sustainability.
The basic model itself is based on a single fish species, an aggregated (anonymous) fishing effort, a lack of uncertainty and a static equilibrium.
3.2. ábra - Figure 3.2: Concept of sustainable fisheries (MSY)
19
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management
The traditional, open access dynamics will result to the situation where the fishermen increase their effort (and investment) attempting to gain a greater share of the above-normal profits and this extra effort causes aggregate opportunity costs of fishing to increase until at the level of revenues, at which point rents are completely dissipated. This means resource rents will be unsustainable.
3.2. 3.3.2. Economic sustainability
This component of sustainability focuses on socio-economic welfare, measured at the level of individuals, and aggregated across the resource system. It blends together economic criteria (such as the level of resource rent) and social criteria (such as overall distribution of equity), at the policy level. Socio-economic sustainability pertains to the generation, distribution, and maintenance of benefits amongst individual actors or ‘players’ in a fishery arena. Criteria for assessing sustainability in this connection thus include, for example, the extent to which a fishery provides employment, income, and food security advantages to small-scale harvesters and traders, the extent to which different players share in these advantages, and the extent to which they will remain a viable basis of livelihood.
Economic efficiency is the ultimate goal of every individual fishermen and industrial unit. In a well developing fishery, profits and high wages attract new harvesters and investments in better equipment. If the economic development proceeds, the limited yield is shared among progressively more harvesters. Far more labour and capital than are needed are employed in utilising the resources. This, in turn, leads into management authority to employ tactics such as closed seasons and restricted harvest areas. As their response, the individual fishermen start applying new innovations and advanced technology in order to cope with the increased competition.
Fishery with larger harvesting units becomes capital intensive with larger debts to be serviced. In the long run, the whole sector is dominated by fewer units with shorter economic views.
This development makes the managerial actions by the governmental bodies very demanding and complex as these organisations should carry out the policy that maintains the economic sustainability of the whole fishery society. A general hypothesis in economics is that maximization of a society's welfare requires at least that the basic factors of the production (labour, capital, resources) be "efficiently employed". According to this hypothesis, governments as resource owners should restrict entry to resource harvesting by introducing high licence fees, direct tax on the harvest, or individual or vessel quotas. The economic stability in fishing sector requires, however, some sort of trust in the long-term sustainability of yields, markets and the policy environment. Similarly, the secondary sectors such as processing industry and fishery tourism are highly dependent on long-term stability of the production (yields in captured fishery, aquaculture) and the working opportunities of the producers.
3.3. 3.3.3. Community sustainability
Community sustainability pertains to the issues of wider collective identity and welfare. It is measured with reference to such criteria as the extent to which a fishery: a) contributes to community stability in the long run;
20
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management b) allows local group access to the resource base and community involvement in resource management and development decision-making; and c) affects the fortunes of various community sub-groups such as women, youth, etc.
Key criteria:
• will long-term stability of affected communities be maintained
• does the local population have access to the resource base
• is the local population integrated into resource management and development practices, with traditional management approaches utilised to the extent possible
• are the local socio-cultural concerns incorporated
3.4. 3.3.4. Institutional sustainability
This level of sustainability is a prerequisite for each of the above three fundamental components of the sustainability. The institutional sustainability refers to suitable financial, administrative and organisational capabilities of the fishery society but also those of the managerial organisations.
Obtaining valid information on the key stock and population parameters requires long-term scientific inputs, personnel and organisations to conduct such studies. Similarly monitoring the major parameters of fishery, e.g. fishing effort, gear types, fish markets and prices, and the whole socio-economics of fishery needs logistical and personnel capacity in the field and central administration. The lack of field personnel, their insufficient professional capacity or limited access to the fishery is often the major constraint in such data collection or fishery follow-up particularly in the inland waters and remote areas of the Third World countries. The estimations of fishing effort (mortality) and fish yields, the crucial parameters of bio-economic fishery models, are at the same time the most difficult ones to obtain or control in the field conditions. In consequence, the application of such models based on accurate data collection and long-term time series is proven inefficient and useless in practice. The new concepts and terms have been called for in the management procedures:
• risk assessment
• management under complexity
• coping with uncertainty
These terms are difficult to interpret and more difficult to apply, since the character of the uncertainty is difficult to define. Uncertainty in fisheries management decision-making can arise from diverse causes:
• difficulty in defining a lower critical level to which a stock could be allowed
• to fall due to heavy exploitation
• observation and reporting errors in catch and in resource assessment
• lack of adequate knowledge in functional relationships in the ecosystem
• the stochastic nature of the dynamics of the resources
• the effects of exogenous variables, e.g. environmental factors, on the resources
• the difficulty of establishing life history parameters precisely.
4. 3.4. Stock management
Stock management deals with management measures that promote the sustainable use of fish stocks. Stock management includes stock and population studies, stock enhancement through stockings and introductions, and control of the fishing effort which are briefly introduced in the following.
21
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management
4.1. 3.4.1. Stock studies
Modelling the stock needs quantitative data of age distribution and individual growth which then can be turned into estimations of stock size, mortality, relationship between the parental stock and reproductive output as well as fecundity. These factors affect the dynamics and production of the stock.
One can obtain data for these population parameters either from population samples or catch samples. The former samples describe the age and growth structure of the entire population whereas the latter provide data of those individuals caught by the fishermen. Usually the non-biased samples of fish growth are obtained from the population samples. The population analyses in turn are based on catch samples which often are subject to selectivity. The final goals of the study affect the sampling design, and quite often both types of samples are needed.
If fishing is very intensive, catch and population samples lead into more or less similar results of fish growth in age groups that are fully recruited to fishery.
Stock size assessment
Tagged and released fish can be used to assess the initial population size (N) in the lake. The mark-andrecapture method is based on Petersen estimation that assumes the tagged fish behave in the similar way as their natural siblings and their catchability is also not affected by the tagging.
N = m x T / n
, where
T = number of harvested fish to be tagged n = number of recaptured fish m = number of tagged in recaptured fish
Electric fishing
Electric fishing is a method to study population size and structure, stock biomass and their spatial and temporal changes. One can also collect fish samples for further analyses. Sampling the fish populations with electric device works best in small water bodies, rivers and rapid falls with currents less than 15 m3/s and depth below 1 m. Electric fishing is suitable also to study bigger lakes and rivers but only in their stony littoral and vegetation zone. In this environment, the method is used to assess impacts of water level regulations, bottom dredging, random pollutant releases, restoration of the bottom or water shed area.
The equipment consists of a generator or battery releasing pulsed direct current, a negative electrode (cathode) that is usually a metal cable or net, and a positive electrode (anode) that is a dip net. The electric field between the two electrodes causes a voltage in the fish body tissues when fish goes in a longitudinal position in the field.
The field is strongest close to the anode where circular zones appear effecting the fish. Depending on the distance fish can become driven away, directed or knocked out. The depth range of electric fishing is limited by the size of the electric field created by the cathode and the last two zones in which fish can be collected may vary between 1-4 meters. The strength of internal electric voltage correlates with the length of fish: the method is at best for fish of 3-25 cm standing still on the bottom or in shallow water.
Test fishing
Test fishing with gill-net series is a conventional method to study changes in stock size, composition, species ratios and population structure. Often the method is regarded labour intensive, time consuming, expensive and inaccurate and the outcomes less useful due to great variations in the unit catches. Recently the gear itself and the sampling strategies have been improved to avoid these problems. In consequence the test fishing with standardised gill-net series may provide adequate information on spatial and temporal changes of the above mentioned parameters. Also one can obtain non-biased fish samples for closer ecological studies.
22
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management
Acoustic surveys
Acoustic surveys give means to study fish stock dynamics and fish movements in environments that are less known through other investigations or on species that are short lived and therefore difficult to catch otherwise.
In fisheries, the term 'echo sounding' (or vertical sounding) is usually restricted to sound transmitted from a vessel and returned to it along a line straight down to the sea bed (or bottom). The equipment employing this technique is called an 'echo sounder'. Sonar is equipment based on the same principle but capable of transmitting and receiving in more or less horizontal directions. Thirdly, a 'netsonde' is equipment which collects information with sensors at the trawl net and transmits it for display in the wheel house. An echo sounder consists of four main components:
• transmitter to produce energy in the form of pulses of electrical oscillations.
• transducer to convert the electrical energy to sound in the water and conversely, the sound waves of the returning echoes are converted back to electrical energy.
• receiver to amplify the weak electrical oscillations produced in the transducer by the echo so that they can be recorded or displayed
• recorder to display echoes on a paper or as an audible signal.
The results of acoustic surveys are thus a combination of echo sounder survey, analyses of sampled fish, and previous information on environment, stock history, and the likely spatial and temporal variations of the stock.
To obtain necessary information for fish biology and fishery research, a proper sampling strategy has to be designed not only for the acoustic survey but also for the complementary studies.
4.2. 3.4.2. Population studies
Population studies indicate the effects of environmental factors and fishing operations on the fish stocks. Studies can also be used in short-term predictions on future changes of the stocks, their structure and production. The major parameters of population dynamics are mortality (natural and fishing mortality), yield per recruit model, and length-age ratio.
Population samples are taken with non-selective gear in seasons when both sexes and all age groups, mature and immature fish, are randomly present and equally subject to sampling. Gill nets are hardly suitable for this purpose. The minimum of 300 individuals for population analyses are collected. The coefficient of variation is calculated to assess the quality of data set.
Intrinsic total mortality (Z) consists of fishing mortality (F) and natural mortality (M). Fishing mortality is caused by fishing operations and natural mortality by other factors like predation, diseases, parasites and reproductive effort. The latter one is hard to assess and values are therefore kept constant and obtained from literature. Mortality can also be estimated with the log-regression method in catch curve.
4.3. 3.4.3. Growth studies
Fish growth indicates changes in the fish populations' living conditions in general and in temperature and feed conditions in particular. These changes can be seen in fish even afterwards by studying the formations in fish scale or other bony appearances. Growth studies are also important in assessing the fish production and catchability which is of great practical importance in fisheries management. Further fish growth rate and size affect in accumulation of toxins and their metabolic substances in fish.
Basically fish growth depends only on two environmental correlates: 1) ambient temperature that can be measured directly in water and is often described as the index of day-degrees (number of days multiplied with the average temperature), and 2) food availability which in turn is dependent on physical, chemical and biological factors. Individual fish growth rate and the average production level of the population is therefore the outcome of multiple factors. Though often measured as basic variable, fish growth is seldom used in routine environmental monitoring but more often as major tool in assessing the population structure, age distribution and population dynamics.
23
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management
Common formula for length and weight measurements are the following (Ricker, 1975): absolute growth l
2
- l
1
or w
2
- w
1 relative growth (%): l
2
- l
1
/l
1
or w
2
- w
1
/w
1 instantaneous growth lnl
2
- ln l
1
or lnw
2
- lnw
1 instantaneous growth G= b( ln l
2
- ln l
1
), where b = coefficient of the following length-weight relationship W = a L b , or ln W = ln a + b ln L condition factor K = W/ L 3 von Bertalanffy lt = l∞ (1 - e -K(t-to) )
Yield per Recruit Analysis
The models of yield per recruit (= cohort entering the fishery) were developed to help in advising and controlling the fishing effort in fisheries management. The model gives estimations of expected yield as the function of fishing mortality, fish growth rate and natural mortality.
The Y/R model uses the average weight of each age group. These figures are calculated from age-length data using von Bertalanffy growth formula. Including the length-weight regression to the formula, we can calculate age-specific weights. The Y/R curve is produced by plotting the expected yield (in numbers) per 1000 recruiting individuals if the fishing mortality is changed e.g. between 0.05 - 2.0, and the natural mortality is assumed to be constant. With the average individual weight the number of caught fish is turned into respective yield in kilos.
Virtual Population Analysis
The assessment method most commonly used is virtual population analysis (VPA). It relies on parameters measured on catch and estimate of unknown parameters, such as natural mortality. Catch analyses should cover both commercial and recreational fishing. Furthermore, the terminal fishing mortality is difficult to estimate and must be tuned with other independent estimates, which can also be an error. There are changes throughout the year such as fishing intensity, stock abundance and availability, and gear selectivity. However, VPA emphasises the aggregate catch, which could be achieved if many unknowns could be accounted for. VPA model can be applied in fisheries research if the fishing intensity is high (fishing mortality >0.4) and natural mortality low
(<0.3). Usually the analysis requires a long-term monitoring, e.g. 5-10 years, in fisheries, or alternatively, a weekly analysis of total catch and age distribution that is available in a limited target.
Catch per Unit of Effort analysis
Catch per Unit of Effort (CPUE) indicates the yield harvested with a given fishing effort. The effort can be measured with fishing time, number of harvests, area or volume of the gear, or any related parameter that describes and standardises the effort of certain gear or fishing operation. The respective catch indicates then the stock sizes in a given time or place and when collected in standardised way, CPUE is a suitable indicator of possible changes of total catch or species-specific catch within a time frame.
CPUE analysis is therefore a better indicator of stock size than a total catch figure which is subject to possible changes in fishing effort. CPUE is often replacing the demanding and expensive VPA analyses in routine fishery research.
The relationship between catch and effort:
C/ E = qN,
24
Created by XMLmind XSL-FO Converter .
3. Fish population ecology, stock assessment and management where: C = catch
E = effort q = catchability coefficient
N= population size
The CPUE (C/E) is directly proportional to population size (N) and the catchability (q) is often neglected. By assuming the q being constant, age specific CPUE's can be obtained by dividing respective catch with the effort.
CPUE data can be obtained from 1. Test fishing, 2. Book keeping and 3. Fishery statistics.
Fishermen keeping records on their catch and fishing effort are subject to errors due to insufficient recording of bycatch and commercially less important species, and low motivation to record small quantities of fish particularly in lake and recreational fisheries. Book keeping has been most successful in marine salmon, herring,
Baltic herring, white fish and pike perch fishery. Data of commercial fishermen may also include important information on the fishing costs. Data collection for the statistical purposes is often hampered by poor design of sample design, inappropriate personnel and physical capacity, low motivation and insufficient training amongst the institutions responsible for the national statistics. This is one of the constraints for sustainable fisheries development and management planning in major parts of the world. To estimate the catch and effort data of non-commercial, sports and recreational fishery or amongst fishermen fishing only for the subsistence is difficult also in the developed world.
25
Created by XMLmind XSL-FO Converter .
4. fejezet - 4. Fishing methods and equipment
The fish production of the world takes place basically in two systems. Fisheries in its classical sense make use of the natural progeny of the fish stocks of waters, while aquaculture effectuates more or less expenditure for the sake of increasing the safety and intensity of production. So the success of fishing and the ability to plan it economically depends on a number of factors which cannot or can only hardly be influenced, so the view that production should be transferred to the fresh-water systems that can be controlled better, mainly to the freshwater aquaculture. Besides all these tendencies, a significant share of the fish production of the world is still given by the fishery of the oceans and the seas – as a result of their large area.
These tendencies show stagnation in fisheries landings, so the quantity of the production of cannot be increased in a significant degree, because it is a sensitive system, which can collapse any time, without any serious antecedents. This is reinforced by the fact that all over the world, only fish-meal remained in use for animal protein source, so the fluctuation of the production of marine fishing (which is the major source of fish-meal) can become easily a key factor in world economy.
1. 4.1. Main types/classes of gear and methods used in fisheries
There are a wide range of gears in use depending on the species targeted. These can be classified as active or passive gears (fixed/set or moving gears) in relation to the equiplent and the target specie(s). Anyway, in order to be successful the one must account for fish behaviour when selecting and using gar adequate for the targetedcatch. The choice of gear also depends on intended market as it regards quantity, geareffectivity and selection.
The differentiation between passive and active gear is done as follows (parallely to that in land would be the difference between the trapping of and hunting for animals):
• Based on the relative behaviour of the target species and the fishing gear
• Passive gears: the capture generally based on movement of the target species towards the gear (e.g. traps),
• Active gears: capture is generally based on an aimed chase of the target species (e.g. trawls, dredges).
2. 4.2. Characteristics of meshes and nets
Almost all gears (except longlining and pole-fishing) use some kind of netting as active part. Thus the main characterisitics of the netting (mesh size, hanging ratio, thread diameter) fundamentally influence the effectivity and selectivity of the equipment in question:
•
Mesh size: size of fish to be caught/retained by the gear
• Hanging ratio: shape of the fish (round, flat,etc.) caught more effectively
• Thread diameter: stherngth of the netting and visibility to fish
4.1. ábra - Figure 4.1: Main measures of a mesh
26
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment a = Stretched Mesh, OM = Mesh Opening, b = mesh size
Mesh sizes are either given in bar length (i.e. measured from knot-to-knot) or as stretched mesh (i.e. the sum of two bars). The hanging ratio is depending on the making of the net (fixing the netting to the lead and floatline).
A net may be rigged with varying degrees of slack, which is primarily regulated by the hanging ratio. The hanging ratio measures how tightly the net is stretched along the head and foot rope. The hanging ratio may theoretically vary between the value 0 (all meshes mounted at the same point on the ropes, so the net has no length dimension) and a value of 1.0 (the netting is fully stretched out, so the net has no height dimension. In commercial fisheries hanging ratios are normally found between 0.25 and 0.65.
4.2. ábra - Figure 4.2: Common Hanging Ratios
2.1. 4.2.1. Gear Bias
27
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
Every gear has bias, that means the catch by each equipnment differ from the ideal that can be calculated from the physical characteristics. Certain species, sizes, or habitats are caught more or less often than their frequency in the population. The goal is to get least biased sample possible, especially in sampling to get the most accurate result as possible in order to make the management decision precise. The best way to avoid gear bias is to USE
MULTIPLE GEARS, so the biase of one type of gear would mitigate that of the other.
2.2. 4.2.2. Gear selectivity
Each gear has a specific or wide range of selectivity that has to be conideded in the catch estimatiom. A good catch index depends on consistent (precise) and accurate catch estimates andcatch rates depend on sampling gear used. The factors to consider when choosing a gear:
• fish girth vs. mesh size
• gear avoidance capabilities
• recruitment size
• fish behavior (schooling, habitat use, activity rhythm)
• day vs. night gear deployment
• random sample?
Tha catch by a gear can be plotted by length against number and displayed as selectivity curve.
4.3. ábra - Figure 4.3: Examples of a selectivity curves
28
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
3. 4.3. Major gear types
The major gear types used in freshwater fishreries are shown next. They are classified by FAO nomenclature, first the active than the passive gear types.
3.1. 4.3.1. Surrounding nets
Purse seine
A purse seine is made of a long wall of netting framed with a lead line of equal or longer length than the float line. They are so effective that they can catch over 100 tons of fishin marine fisheries in single haul. To improve effectiveness the fish are located with sonar or helicopter.
4.4. ábra - Figure 4.4: Purse seine
Seine nets
A seine is a large fishing net that hangs vertically in the water by attaching weights along the botton edge and floats along the top.They consists basically of a conical netting body, two relatively long wings and a bag. An important component for the capture efficiency of boat seines is the long ropes extending from the wings, which are used to encircle a large area. The bags are responsible for retaining the cach at the end of the opration.
4.5. ábra - Figure 4.5: Seine
29
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
3.2. 4.3.2. Towed nets and dredges
Trawl nets
Trawling is a method of fishing that involves actively pulling fishing net through the water behind one or more boats. The towed net is kept in the edesired depth and horizontally opens by otter boards. The vertical opening of a trawl net is created using flotation on the upper edge ("floatline") or a beam (beam trawl) and weight on the lower edge ("footrope") of the net mouth. There are 2 basic types: bottom trawlingandmidwater trawling, depending on the position in thewater column. Bottom trawling is towing the trawl along (benthic trawling) or close to (demersal trawling) the sea floor. Midwater (pelagic) trawling is towing the trawl through free water above the bottom of the ocean or benthic zone.
4.6. ábra - Figure 4.6: Otter trawl
Dredges
These are gears which are dragged along the bottom to catch shellfish and other bottom dwelling species. They consist of a mouth frame to which a holding bag constructed of metal rings or meshes is attached. Dredges are having a significant ecologicaleeffects e.g. on food chains and bottom habitats, moreover they cause physical damage by preventing settlement of benthos.
4.7. ábra - Figure 4.7: Otter trawl
30
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
3.3. 4.3.3. Lift nets
Lift nets are horizontal netting panels or bag shaped like a parallelepiped, pyramid or cone with the opening facing upwards either fixed ont he bank or operatedfrom a boat. These are submerged at a certain depth, left for a while, the time necessary for light or bait to attract fish over the opening, then lifted out of the water. In order to be more effective, lift netting is practiced using an aggregating device (i.e. things that attracting the targe species such as light), The use of these are banned in many places.
4.8. ábra - Figure 4.8: Lift net
3.4. 4.3.4. Falling gears
4.9. ábra - Figure 4.9: Cast net
31
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
3.5. 4.3.5. Gillnets and entangling nets
A gillnet is a wall of netting set in a straight line, equipped with weights at the bottom and floats at the top, and is usually anchored at each end. Fish swim through the virtually invisible netting, and are gilled when their gills are caught in the webbing, hence the name gillnetting. Fish may also be wedged – held by the mesh around the body, or tangled – held by teeth, spines, maxillaries, or other protrusions without the body penetrating the mesh.
The size-selectivity of the gill nets is the best among all fishing gears, since the circumference of the gill are proportional to the body size of a fish. For this reason these gears can effectively be used to remove a particular size (age group) of fish without harming the other age classes (e.g. spaners or young – undersize ones).
Trammel nets are typically 3-layer nets, a small mesh net sandwiched loosely between 2 panels of larger-mesh net, kept more or less vertical by floats on the headrope and mostly by weights on the groundrope. Trammel nets are most common as stationary gear, but they can also be used drifting. The fish entangle themselves in a pocket of small mesh webbing between the two layers and large meshed walls. Afterwards, the trammel nets are hauled back to the surface for extracting the entangling fish from the netting.
4.10. ábra - Figure 4.10: Gill nets (drifting and bottom-set)
32
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
4.11. ábra - Figure 4.11: Gill net selectivity (length frequencies)
4.12. ábra - Figure 4.12: Trammel net
3.6. 4.3.6. Traps
Trap nets, fyke nets
Traps, large stationary nets or barrages or pots, are gears in which the fish enter voluntarily but retained from escaping, because the entrance is a non-return device, allowing the fish to enter the trap but making it impossible to leave. In order to imporve effectiveness, guiding panels made from netting are used to lead the fish into the catching chamber.
A fyke net consists of cylindrical or cone-shaped netting bags (non-return device) mounted on rings or other rigid structures. It has wings or leaders which guide the fish towards the entrance of the bags. The fyke nets are fixed on the bottom by anchors, ballast or stakes.
4.13. ábra - Figure 4.13: Trap net
33
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
4.14. ábra - Figure 4.14: Fyke net
Fish weirs
Weirs is a group of gears made of various materials (stakes, branches, reeds, netting, etc.), and they are usually installed in tidal waters. They generally have a narrow slit leading to an enclosed catching chamber. The gears set in the same place for several days or months. These gears are generally operated in coastal zones and shallow waters and also in inland waters, usually set from the bottom to the surface.
4.15. ábra - Figure 4.15: Fish weirs
34
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
3.7. 4.3.7. Hooks and lines
Longlining
Fish are caught with a fishing line by encouraging a fish to bit upon a fish hook or a gorge that is buried in the bait. Long line fishing is a commercial fishing technique that uses hundreds or even thousands of baited hooks hanging from a single line. A drifting longline for pelagic fishing, or a bottom-set longline for bottom speceis are consist of a mainline kept near the surface or at a certain depth by means of regularly spaced floats and with relatively long snoods with baited hooks, evenly spaced on the mainline.
Angling
A pole and line consists of a hooked line attached to a pole. This method is common to sport fisheries (angling) but it is also used in commercial fisheries. Fishing rods/poles are made of wood (including bamboo, also constructed of split cane) and increasingly of artificial materilas for being lighter but stronger.
4.16. ábra - Figure 4.16: Longline(drifting and bottom-set)
4.17. ábra - Figure 4.17: Fyke net
3.8. 4.3.8. Electrofishing
This method uses electricity to stun fish before they are caught. A high-voltage difference causes a current to flow from the anodeto the cathode, when a fish encounters a large enough potential gradient on this path, it becomes affected by the electricity. Usually pulsed direct current (DC) is applied, which causes galvanotaxis in the fish. Galvanotaxis is uncontrolled muscular convulsion that results in the fish swimming toward the anode.
35
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment
4.18. ábra - Figure 4.18: Electrofishing operated on foot or from a boat
3.9. 4.3.9. Auxiliary equipment
Fish aggregation devices (FADs)
They take advantage of congregation behaviour od fish to improve effectiveness of a fishing operation. They might be floating rafts anchored offshore to attract pelagic fish, or light by night to attract pelagic fishes. Their main advantage is the reduced search time. Among the disadvantages are higher costs and shorter lifespan is mentioned. There are negative concerns against these devices being too effective in pelagic fisheries but the fish caught is smaller and comes with relatively large bycatch.
Hydroacoustics
The most simple hydroacoustic equipment is the echosounder which acts in a vertical sense sending an echo pulse directly downwards to the seabed and recording the returned echo. The sound pulse is generated by a
36
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment transducer on the bottom of the vessel. They are used for the detection and identification of fish and the determination of depth of water and nature of the seabed.
Netsounder is merely an echosounder with a transducer mounted on the headline of the net rather than on the bottom of the vessel. They are used either for directing the trawl-net to the exact vertical and horizontal position of the desired fish school, or to find out the amount of fish already caught in the cod-end to determine the time of hauling.
4.19. ábra - Figure 4.20: Hydroacoustics equipment in use
4.20. ábra - Figure 4.21: Hydroacoustic display
4. 4.4. Fisheries management problems and solutions
There are several problems to be faced by fisheries. These are:
Maximum sustainable yield& overfishing: maximum amount of fish that can be harvested without depleting future stocks is estimated at 100 to 135 million metric tons in the World, and the present harvests are at about
100 million metric tons. This seems all right, but for fisheries where numbers available, estimated that 45% are currently over-fished, and a number of fisheries have already collapsed (Anchovy fishery off Peru, Cod fishery in the N. Atlantic)
Bycatch& discards: Bycatch are animals unintentionally killed during harvest of the target species. Bycatch in shrimp trawling is very high (125 to 830% of the catch is discarded as bycatch), turtles often caught in trawls.
Tuna known to hang out under pods of dolphins, nets set aroundpods of dolphins would result in many drowning. Driftnets are indiscriminate entangling of many sorts of marine animals. When longlining, many albatross drown trying to snatch bait from long lines being deployed, snagged on hooks and pulled under.
There are solutions for these problems: trawls with trap doors to let turtles escape, nets not set around dolphin pods and/or employ — “backing down”, a technique that lowers upper edge of net letting dolphins escape, banned driftnets in oceanic fisheries (but some countries still using them), or deploy longlining in the dark or with special rig to let line out under water. The technology development is going on to apply techniques and technologies safer to the environment and having little or no impact on the non-target species.
As it regard discards, it is a problem in all fisheries. It is a must, to eturn the fish which are over qota, undersize or non-licensed for a vessel. Nowwadays, many countriesd ban discards, since the fish that are discarded have a
37
Created by XMLmind XSL-FO Converter .
4. Fishing methods and equipment negligible chance of survival, so it is better from a management perspective that they are included in the fishing induced mortality figures on which allowable catch estimates are based.
Fisheries mismanagementis various forms of non sustainable exploitation of aquatic resources. These are overfishing, commercial extinction of a specie from a fishing groud, excessive bycatch (estiemted to be 27 million metric tons annually) or targeting smaller species on the low end of the food chain.
38
Created by XMLmind XSL-FO Converter .
5. fejezet - 5. Fisheres and aquaculture engineering and construction
1. 5.1. The definition of fish pond and its operation
Pond fish is a farm unit containing ponds with different functions, where a planned and intensive fish breeding is operated. The basic conditions for proper operation of fishponds are the suitable water supply and the controlled water management. When planning, the available amount of water, its periodical distribution and its quality must be taken into consideration. These factors determine the size of the pond fish as well as the way of its water management and operation.
In most cases, ditches of irrigation systems provide the required amount of water. The mam periods of water requirements of irrigation and fish culture are not the same, so they complement each other and make the exploitation of the establishments more economic. Other fishpond farms cover their water requirements directly from rivers or partly from cooling water of power stations. In case of any water source, an important requirement is the economic water management. This is because facilities must pay for the water usage, and on the other hand, water having a good quality is an increasing and highly usable value for the national economic system.
1.1. 5.1.1. Types and elements of fishponds
The fishponds are constructed so that all conditions can be provided for fish meat production: when needed, it can be flooded; the suitable water level can be sustained and totally drained.
The basic pond types are:
Embankment ponds: ponds that are constructed with a dam to hold back water. These are constructed on sites with steeper topography, forming an earth embankment or dam across a watercourse. These ponds are generally suited to areas where land slopes range from mild to steep and the watercourse is deep enough to impound water at least 6 feet deep at the embankment.
Building dams at right angles to the flow direction can create ponds. The number of the ponds depends on the amount of the usable water and the configuration of the terrain. As water inlet and outlet happens ponds by ponds only one sluice per pond is necessary. In times of flood surplus water is led through flow decrease built in dams. The construction costs of this type of ponds are the smallest. On the other hand the amount and movement of the water cannot be controlled in advance, so the risk of production is significant. Water flowing through the ponds helps the pathogens in spreading; transports silt from the upper ponds into the down ponds and has a harmful affect on the survival conditions of food organisms.
39
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
Excavated ponds: ponds that are constructed all below ground. These ponds are constructed on sites with little or no ground slope by excavating a pit below the normal ground level. These ponds work well in areas which have naturally high water tables. These types of ponds generally require more earth to be moved than embankment ponds for comparable storage. Therefore they are generally used when embankment ponds will not work.
These ponds are a characteristic of fishponds in flatlands. Artificial weirs border each side of the pond. Water management of these ponds is absolutely individual and planned in advance. Water inlet is carried out by using shallow intake canals, while the outlet is let through deep drainage canals. Each pond has an intake and a drainage sluice concurrently. The size of the ponds is not determined by the configuration of the terrain, but depends on the economic view of the fish meat production.
Advantages: this makes the planned and safe fish breeding possible, much more easy to prevent diseases, better affects of fertilizing ponds, constant water covering. The disadvantage of this type of ponds is that construction and maintenance costs are the highest.
The main complementary elements of a pond are:
Canals: water is led through water intake canals into the pond. The size of these canals is dependent upon the number and size of the connecting ponds. Their water level should be higher than the ponds have, because the water intake is carried out by gravitation. When discharging water, water is led through outlet canals from the ponds. Their capacity should be measured out not to cause any problem in the autumn cropping period. The bottom of these outlet canals is minimum 50-60 cm deeper than the bottom of the outlet sluice.
Dams: ponds depending on their area conditions are partly or wholly bordered with artificial dams (weirs). Their function is to provide the water level suitable for proper operation of fishponds. The top width of the dams is usually 3-4 m. Its height is 0.5-1 meter above the water level. The slope on the waterside is slighter (I: 1.5-3) than on the other side (I: 1-1.5/. The way of their construction is primarily dependent upon soil conditions and the heaviness of their load. In case of loose soils seeping can be reduced by slight slopes, as well as with clay built in the weir. If the bottom of the pond slopes to one given direction, on the deep water side the increased pressure is compensated with a stronger weir and a supporting shoulder. On the top of the dams a dusted road or a narrow-gauge railway system can be built. This makes the tasks of working processes and haulage related to fish breeding much more easily and faster.
5.1. ábra - Picture 5.3:Cross section and elements of a dam
40
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
Sluices: Most commonly sluices are used for controlling water inlet and outlet. This is made of reinforced concrete, and it has a lying pipe crossing the dam of the pond, and a tower connecting to the pipe on the pond side. The diameter of the pipe is 30-100 centimetres depending on the size of the pond. The tower is usually equipped with 3 pairs of perpendicular grooves. In the outside grooves there is a fish screen, and in the inside ones there are closing boards. The role of the fish screen is to prevent useful fish from escaping as well as weed fish from getting into the pond. The water level is controlled by closing boards. The rarely used opened sluices are applied to water inlet.
5.2. ábra - Picture 5.4: Cross section of a sluice
Emergency sluices: The amount of the water cannot be totally controlled in all kinds of ponds with sluices.
Where the flow of the inlet water is expected, an emergency sluice is built into the dam of the pond. Its role is to lead the extra amount of water from the pond, which is cannot be drained by ordinary sluices. The bottom of the structure is at the same height as the water level of the pond, or it can be 50 centimeter deeper. It is advisable to build its foundation and sides from concrete. In the countersunk emergency sluices up to the expected water level there are closing boards and in front of these there is a fish barrier. The whole width of the emergency sluice is dependent upon the size of the pond and the possibility for a flood.
5.3. ábra - Picture 5.5: Emergency sluice
41
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
Harvesting pit: This is necessary for cropping. There are two types of it: the inside and the outside ones. The first is an artificial basin applied in front of the drainage sluice. When cropping, fish accumulate here. Ditches are used to lead the water from the depression of the pond soil to the harvesting pit. In order to dram the water perfectly, the bottom of the drainage sluice must be deeper than the bottom of the harvesting pit. The outside harvesting pit is built behind the drainage sluice outside the pond. This is more expensive, but is more up-todate than the inside harvesting pit. It is very common to build it from concrete, and if it is possible more than one pond are connected to it. It is much more easier to crop the fish from the outside harvesting pit as well as automating the working processes is cheaper.
Constructive works in the fishpond are continuously exposed to the power of the water, so they need a permanent maintenance. These services are extraordinary costly, when they are applied late. Small gaps, breaks and holes let the water damage these constructive works and in a few years they become useless. The most important task is to save the dams technologically. A reed zone edging the dams can provide an effective safe against surf. The width of the reed zone is 3-8 m depending on the size of the pond and the prevailing wind. The best but most expensive way of saving dams is to cover them with concrete or stones.
It is advisable to keep an eye on the technical situation of the sluices and their accessories. In case of recognizing deficiencies in the production period, that cannot be repaired immediately, but they do not cause any problem in the operation, they must be noticed. Such deficiencies must be repaired after cropping the fish.
Constructive works made of stones and concrete can be damaged by ice. In order to prevent this, constructive works and their surroundings must be defrosted. Depositions of silt must be regularly taken away from different canals and harvesting pits. Much of the maintenance works can be carried out after cropping and drying out of the ponds.
1.2. 5.1.2. Classification of fishponds by use
Ponds according to their purpose of operation can be 1) hatching/breeding, 2) nursing, 3) rearing/outgrowing, 4) finishing and 5) storage ponds.
Hatching/breeding ponds have been almost exclusively built natural-like propagation of fish. These are small pools with an area of 200-1,000 m2. Their water level is 40-50 cm on average. The bottom slopes towards the drainage sluice, where the water depth is up to 70-80 cm. Many freshwater fish prefer just inundated ponds with grass-covered bottom without egg- and fry-eaters for spawning, so these conditions must be provided. At the beginning of the breeding season hatching ponds are inundated by water carefully filtered through screens, and females are stocked there. These ponds operate until the egg-laying finishes; fries hatch and the advanced fries find a suitable amount of food. The stock of the advanced fries is harvested at the age of 10-15 days, and the pond is dried out. The lost grass-cover is replaced and cultivated until the next breeding season and the constructive works are under maintenance.
Nursing ponds have become necessary because of the wide spread of the artificial fish breeding. They are usually built close to the hatchery building and they are to rear safely the artificially hatched advanced fries. For this purpose ponds with an area of 0.5-1 ha are usually built. By the beginning of rearing fries ponds are dry and they are inundated only 2-5 days before stocking. The average water depth is 60-80 cm. An important requirement that the filling water must be of a good quality and contain no hatchling-eaters. The fast reproduction and the maintenance of the population of natural food organisms can be achieved by applying fertilizers. The period of rearing fries is usually 25-30 days. Larvae harvested from the hatching and the nursing ponds get into the fingerling ponds, where they develop by the annual age.
Ponds with an area of 5-20 ha are suitable for rearing/outgrowing. Their average water depth is 80-100 cm. The amount of the natural foodstuffs is increased with applying fertilizers. Finishing ponds are the largest in fish farms. In technology point of view there is no significant difference between them. Depending on terrain conditions, in rolling country there are smaller (10-100 ha) and in flat areas there are bigger (50-200 ha) ponds.
Their water level is 100-120 cm.
Storage ponds involve wintering, ordinary storing and brood keeping ponds. Wintering ponds are primarily used for storing commercial fish that is unmarketable in the autumn period. They are usually built by digging into the ground. The most common sizes of wintering ponds: 12 x 25 m (small sized wintering pond) 20 x 50 m (large sized wintering ponds). Their water depth is 160-180 cm. An important requirement for wintering ponds is that they must be easy to approach by means of transportation. From spring time till autumn wintering ponds can be used for: breeding carnivorous fishes, storing females, rearing fries. Deep ponds that have bigger size than the average wintering pond has, and have a perfect water management as well as primarily used for storing fishes
42
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction for a longer period, are called storing ponds. Brood keeping ponds have an area of 0.5-1 ha. The female stock is kept there except the egg-laying period.
2. 5.2. Engeneering on inland waters
2.1. 5.2.1. Fish passes and ladders
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial barriers (such as dams and locks) to facilitate diadromous fishes' natural migration. First recrord on fish passes was found from
17th Century, France where long side canals were constructed on canals to bypass high slope. The Ballisorade ladder was made 1852-1854 in Ireland, to draw salmon into a river that had not supported a fishery. The first
USA fish ladder was built in 1880 at Pawtuxet, Rhode Island. As the industrial development advanced, dams and other river obstructions became larger and more common, leading to the need for effective fish by-passes
5.4. ábra - Picture 5.6: John Day Dam fish ladder on the Columbia River, North
America(Source: US Army Corps of Engineers)
There are five main types of fishway:
1.
A pool and weir is one of the oldest styles of fish ladders. It uses a series of small dams and pools of regular length to create a long, sloping channel for fish to travel around the obstruction. The channel acts as a fixed lock to gradually step down the water level; to head upstream, fish must jump over from box to box in the ladder.
2.
A baffle fishway uses a series of symmetrical close-spaced baffles in a channel to redirect the flow of water, allowing fish to swim around the barrier. Baffle fishways need not have resting areas, although pools can be included to provide a resting area or to reduce the velocity of the flow. Such fishways can be built with switchbacks to minimize the space needed for their construction. Baffles come in variety of designs.
The original design for a Denil fishway was developed in 1909 by a Belgian scientist, G. Denil; it has since been adjusted and adapted in many ways. The Alaskan Steeppass, for example, is a modular prefabricated
Denil-fishway variant originally designed for remote areas of Alaska
3.
A fish elevator or fish lift, as its name implies, breaks with the ladder design by providing a sort of elevator to carry fish over a barrier. It is well suited to tall barriers. With a fish elevator, fish swim into a collection area at the base of the obstruction. When enough fish accumulate in the collection area, they are nudged into a hopper that carries them into a flume that empties into the river above the barrier.
4.
A rock-ramp fishway uses large rocks and timbers to create pools and small falls that mimic natural structures. Because of the length of the channel needed for the ladder, such structures are most appropriate for relatively short barriers. They have a significant advantage in that they can provide fish spawning habitat.
5.
A vertical-slot fish passage is similar to a pool-and-weir system, except that each "dam" has a narrow slot in it near the channel wall. This allows fish to swim upstream without leaping over an obstacle. Vertical-slot fish passages also tend to handle reasonably well the seasonal fluctuation in water levels on each side of the barrier.
43
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
2.2. 5.2.2. Water habitat reconstruction
44
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
Notches in the water regime of rivers
The notches can be described as artificial channels - penetrating through the downstream end of the natural banks (dunes) built by the river sedimentation - that collect and guide back the water from the runoff area, starting from the deepest points and connecting them with each-other and also with the river-bed. The consequence of this the water-flow in the notches was two directional: inwards (towards the runoff area) when floods occurred, and outwards (towards the river-bed) after the floods.
5.5. ábra - Picture 5.12: Asketch of a notch system
The main concept behind the notch system is to connect the water bodies of the runoff areas into one unit enabling the water to move slowly but continuously into two directions (one at a time): to and from the riverbed. This water system is based on the natural "breathing" (i.e. flood and shrinkage), of the river. The main ways of floodplain management were: fishing, extensive animal husbandry, forestry, horticulture (tolerant orchards), crop production.
Wetland reconstruction
In recent decades human activities have hadmany negative impacts on the various water
(eco)systemswithinEUregions. These negativeimpacts include increased pressure on existingwater systems, such as poor water quality,pollution,water shortage and lack of availabledrinking water, exhaustion of flora and faunaand generally a reduction of the environmentalquality of the area.In addition a lot of regions face challenges todealwithwater quantitywhich require them toenlarge the water retention capacity due toanticipated climate change.
The development of new lakes andwetlands significantlyincreasewater quality in thewatersystem, and at making thewatersystem moreflexible in terms of quantity.
5.6. ábra - Picture 5.13: Example of a wetland rehabilitation project
45
Created by XMLmind XSL-FO Converter .
5. Fisheres and aquaculture engineering and construction
46
Created by XMLmind XSL-FO Converter .
6. fejezet - 6. Water management
1. 6.1. Water management in inland natural waters
Fish yields on the global scale have been stable on their present level, i.e. 95-100 million tonnes but there are signs that major part of the main fish stocks are either depleted, over fished or heavily fished due to increasing international fishing pressure, and only a few stocks in the southern hemisphere are regarded. Thus, the common concern on the future status of world fisheries resources is more than justified, and all the efforts to manage the fishing operations (regulate, control, follow-up, direct) on a sustainable basis are given highest priority in the coastal nations.
Today, the oceans that once seemed a bottomless source of high-protein, low-fat food are rapidly being depleted in the way which soon leads into global crisis in the fishing industry. The national fleets with technological and economic over-capacity in Europe, US and SE- Asia are those who suffer most from the situation. The excess capacity of the off-shore technology has to be cut off by selling the gear, vessels and processing facilities or alternatively by transferring it to other continents which in turn adds to the pressure in the Third World waters
(EU-ACP Fishing Agreements have opened the EU fleet an access to these grounds even within the coastal nation's EEZ's; fishing rights are being compensated financially or through other development inputs). In every case, the individual fishermen, owner companies and the whole fishing society are bearing locally the consequences of such global and policy- based decisions.
Fish stocks of various types of inland waters, such as lakes with their floodplains, reservoirs, rivers, wetlands and coastal lagoons are exploited for a range of fishery related purposes. The same waters are used for a number of human activities other than fisheries including power generation, agriculture, navigation, tourism, urban and industrial water supply and waste disposal. These compete with fisheries by modifying the structure of the environment and the quality and quantity of water. In so doing they threaten the sustainability of aquatic ecosystems and the fisheries that depend on them.
1.1. 6.1.1. Reconstruction/development of spawning grounds
In order to overcome the negative tendencies detailed above we need to develop the fish stocks regarding quantity and species composition. One effective way is to (re)construct breeding and nursery grounds to enable natural propagation processes.
Problems associated with breeding grounds are related with reduced access to the grounds, non sufficient amounts of spawning individuals, weakened quality of spawned eggs, poor water and habitat quality and other physical factors that often are due to pollution, eutrophication, siltation or excess fishing pressure. Similarly the hatching eggs failing to develop and pass through larval stages may suffer from these environmental damages and more often from interactions with predators and competitors. The hatching and early larval stages are commonly regarded as critical periods of fish life-cycle that affect the degree of recruitment and production of fish ensembles.
The studies on breeding grounds include interviews of fishermen knowing exact locations or having learnt the migration routes of mature fish, direct observations of the spawning individuals or studying the eggs on the grounds. The spawned eggs can be studied quantitatively by SCUBA diving using specific samplers, dredges or pumps. The survival of the eggs on the bottom or vegetation (fytophiles) can also be followed with certain time intervals. This is not possible with pelagophil species releasing their eggs into open water. Fish eggs can also indicate the water and sediment quality and cage experiments have been designed to follow the environmental impacts on egg quality, survival and hatching.
6.1. ábra - Figure 6.1: Elements of fish migration and habitat use
47
Created by XMLmind XSL-FO Converter .
6. Water management
1.2. 6.1.2. Actions in the runoff area
Assessing the status, physical, chemical and biological quality of the target runoff area is an essential part of the fisheries management procedure. These studies provide basis for planning the restoration, compensation for destruction, and other measures to maintain the environment, fish communities and fishery, or, respectively, to improve the conditions for future fishery. These assessments rely on the knowledge of the optimal living conditions of fish species and the critical parameters affecting them at various life stages. Often this knowledge is insufficient and not available as species or site specific. Therefore the information has to be obtained from published literature on fish, plankton or macrozoobenthos, etc.
The assessments should provide quantitative data on physical and chemical parameters known to be critical for fish production or fishery development. In consequence the environmental and fishery authorities can plan for their common actions to manage both the environment and fishery as livelihood. Such actions may become necessary in lakes subject to eutrophication and pollution, in rivers regulated or built for hydro-electric or irrigation purposes, or in any inland, coastal or marine areas where the multiple use of waters has to be managed jointly.Available solutions in the runoff area are shown on Figures 6.2 and 6.3.
6.2. ábra - Figure 6.2: Example of a notch system reconstruction on the runoff area
6.3. ábra - Figure 6.3: Example of a habitat and spawning ground reconstruction
48
Created by XMLmind XSL-FO Converter .
6. Water management
1.3. 6.1.3. Habitat development
The occurrence of fish stocks and their productivity depend greatly on environmental status. The requirements on environmental quality in water or habitat vary during the life-cycle of fish, which brings additional requirements for the studies too. If one has the lake bathymetric map digitised, habitat and bottom descriptions as well as the types of bottom vegetation, the GIS system will provide graphically provide the areas of suitable breeding and nursery grounds of carp of any species for which the living requirements are known. The effects of water level adjustments can easily be simulated too. In forestry and aquaculture GIS has been also used in economic feasibility analyses as one can also include non-biological environmental variabilities in the model.
The GIS information system can be used together with Habitat Evaluation Procedure (HEP). The HEP system describes the environment first with Habitat Suitability Index (HSI) that varies between 0.0- 1.0 (species' preference for feeding, hiding, reproduction is considered), and second, with area of the habitat (A). Bovee
(1982) gave a relationship:
HU = HSI * A, where
HU=habitat unit of the target species; HSI=habitat suitability index; A = area
The Instream Flow Incremental Methodology (IFIM) was developed particularly for the riverine environments in which the parameters of water quality, temperature, flow and bathymetrics are being combined with speciesspecific data on macro- and micro- habitat levels. This method and all related tools need such specific data on target species and considerable amounts of the environmental measurements in order to submit estimations of areas suitable for e.g. stocking programmes or to lead into areal restrictions in fishing. Any methods used for environmental mapping can, however, be used to assess only the potential areas for breeding and nursery grounds, but the actual production of the fish community is then dependent on other regulation mechanisms, such as predation and competition. The possible solutions and areas of action are:
•
Flood-drain paths: - construction of natural-like spawning grounds (natural, or with waterretention/supply)
• Small (temporary dams): - water retention/supply at areas behind the dams - use of construction pit
• Main dam-line: - use of construction pits (with water retention/supply
• Drainage path/runoff area: - formulation of natural-like spawning grounds with water retention/supply
49
Created by XMLmind XSL-FO Converter .
6. Water management
6.4. ábra - Figure 6.4: Example of an integrated runoff management project (comlex habitat development)
6.1. táblázat - Table 6.1: Analysis of possible conflicts with stakeholders in case of habitat reconstruction on runoff areas
Interest groups: Interests/conflicts:
Construction/engineering Neutral / Supportive
Forestry
Nature conservation
Agriculture/arable production
Neutral / Supportive
Supportive
Neutral
Population Supportive
2. 6.2. Water management by intensity
50
Created by XMLmind XSL-FO Converter .
6. Water management
As alternative goals, the management are to improve the value of harvested and processed fish, and to increase the availability and value of the services in the industry. The value is always a relative issue and it can be evaluated against the consumers' demands and possibilities to fulfil the needs. The value in fisheries can be regarded as materialistic (monetary) issues or non-material value that promote genetic biodiversity and nature conservation, or deal with human and social issues.
Amongst the fishermen, one can find various forms of value setting, e.g. those by professional fishermen, land and water owners, or aquaculturists who regard the fishing and fishery resources as the source of income and employment, whereas the recreational and sports fishermen put more emphasis on the experiences gained, services available and social contacts. The latter group of fishermen are also interested in the number of fish caught but they do not make their decisions with similar economic criteria as the former ones. Different expectations of the fishermen groups request various managerial measures and outputs that also depend on the efficiency of the management organisations. The levels of management by intensity:
• Extensive management – no control of water quality
•
Semi-intensive management – partial control of water quality
• Intensive management – complete control of water quality
Entering the fishery during peak seasons or years with encouraging yields is easy particularly in small-scale, low investment fishing, but on the other hand, leaving the occupation is always difficult if not impossible as the society is unlikely able to purchase the gear, boats and other excess technological capacity if the yields are reduced dramatically. Together with the improved harvesting technology the increased number of fishermen has forced the managerial bodies to introduce various controls over the exploitation, and consequently altered legislation that favoured private or community ownership. In most cases non-ownership gave way to state property.
Now there is a tendency to move towards "optimal" harvesting dynamics that achieve a socially desirable balance between current and future benefits. The concern for the state of the fish stocks led to the dominance in fishery management with a great "conservation" attitude. This view of "balance of nature" and limited fish resources has in a remarkable way affected both the development of managerial concept as whole and the related research strategy. Similarly, the need to assess the current stock sizes as the main part of management procedure has supported the dominant role of the biological scientists in the process, regardless of humanoriented fishery objectives. The fishery economists in particular complain the imbalance of concerns between ecological and socio-economic events in the management procedure. For example in support to resource oriented approach, stated that "biological models lie at the heart of fishery management". Considering that most resource scientists are trained as ecologists, this attitude is unlikely going to change very soon.
6.5. ábra - Figure 6.5: Commercial aquaculture
6.6. ábra - Figure 6.6: Subsistence aquaculture
51
Created by XMLmind XSL-FO Converter .
6. Water management
3. 6.3. Management procedure
The following consequent steps can be seen in the management process:
1.
Assessing the managerial needs among all the fishermen groups and their associated bodies, as follows:
• expected gains of the fishing: food, income, leisure
• associated activities (gear, boat, processing, marketing) and their goals
2.
Selection of development objectives
With reference to the various level sustainability stated before, the management should address the questions of achieving the respective objectives and seek means to prevent possible conflicts between different interests
• biological objectives: catch level, food, species
• economic objectives: catch value, income, employment, market value
• social objectives: employment, income distribution, health, education, social status, etc.
3.
Data collection
• fishery dependent biological data: yield, cpue, stock size, recruitment, age and size distribution, fishing mortality, etc.
• fishery non-dependent biological data: ecosystem assessment, food web studies, larval and egg studies,
• scientific surveys: gear selectivity, unit stocks, recruitment studies,
• economic data: cost analyses, incomes, markets, processing,
4.
Editing
Editing the data and report serves the communication between the scientists and the administrative personnel.
The studies have to include mutual understanding of the terms and survey objectives. Two-way information flow is important from the administration to the field (fishery) via scientific research and investigations.
Scientists have to take responsibility to make the final statements and conclusions on the study results and outcomes. This requires:
Data processing, testing and editing
• testing the spatial and temporal variations
• assessing the short-term and long-term trends
• environmental correlation
• effects of fishing
Data storage and reporting
52
Created by XMLmind XSL-FO Converter .
6. Water management
• value of the data
• summary of the main results
• spatial and temporal distributions
• trends and correlation
• graphs, figures, maps and tables
• main conclusions
5.
Management implementation
Managerial measures are selected with the following criteria: a.
Possible to execute b.
Flexible decisions c.
Conflicts prevented d.
Fishery outputs distributed in the society e.
Impacts on fish price f.
Labour need g.
Sustainable stock h.
Improved technology i.
Individual freedom j.
Managerial costs
6.
Legislation
• Effects on national fishing laws have to be studied.
•
Local and regional regulations can be altered and modified.
7.
Evaluation
Continuous feed-back system during the process: effects of the managerial decisions on the ecological, economic, and socio-economic status to be assessed locally, regionally and nationally.
There are two types of effects of management: short-term (stock size, population structure, species composition, gear technology, catch size and composition, economic value, etc.) and long-term impacts (stock size, population structure, species composition catch levels, income, employment, social status). The internal or external evaluation can be focused on the (1) management process itself, (2) institutional structure and action, and (3) fishery society.
53
Created by XMLmind XSL-FO Converter .
7. fejezet - 7. Applied hydrobiology – plankton dynamics
1. 7.1. Applied hydrobiology in fish farming
The way of operation the pond farms can be different depending on the aims of production, local conditions and possibilities. Fish farms can be grouped according to the operation cycle, intensity of breeding and the temperature of the water in the pond.
According to the operation cycle, there are: full cycle and partial cycle pond fish farms. The fishpond farm is full cycle, if it provides suitable conditions for each age group of the brood species. In these farms there is a breeding stock and experts deal with propagation, fry rearing as well as producing commercial fish. The partial cycle pond fish farms deal with propagation and fry rearing or producing commercial fish.
According to the intensity of breeding, there are two-year and three-year operation. In two-year operation, by exploiting the maximum growing capacity of fishes, commercial fish is produced in two years. Nowadays this can be only achieved by lengthen the breeding period with applying early spawning and providing quite favorable feeding conditions for fishes. In three-year operation, fishes become commercial ones by the age of three years. In this case the maximum growing capacity is not exploited, but on the other hand, utilization of natural feed is more favorable. In three-year operation a higher density of stock is applied and higher yields per unit area can be achieved.
7.1. ábra - Figure 7.1: Fish pond as complex ecosystem
In course of proper operation of fishponds it is very common that the fish meat production capacity of the pond decreases. The most common reasons for this:
• increased deposition of silt in the ponds
• increased amount of unfavorable anaerobe breaking down processes
• reproduction of pathogens
• decrease in the productivity of the pond ground
• unfavorable changes in the aquatic community, etc.
54
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
In these cases it is necessary to dry out the pond and cultivate its soil for a shorter or longer period of time.
There are two methods of this in practice. One of them is keeping the land dry wintertime and the other is drycultivation for one or more years. In the first case the pond is dry from harvesting in the autumn till the next spring. During this time the silt quickly decomposes, much of the pathogens die, the soil of the pond is totally frosted, aired and its structure becomes more favorable. Land cultivation usually involves 1 or 2 operations with discs. The method of keeping the land in wintertime does not meet the requirements in each type of fishponds.
In these cases it is necessary to let the pond out of the fish meat production and utilized in crop production for one or more years.
During the years of fish meat production organic matter covers the surface of the bottom, and in the period of dry-cultivation it is mixed into the soil and decomposed. This provides suitable conditions for crops. On the basis of experiments the dried bottom is suitable for most crops and often provides high yields. Dry-cultivation is applied until soil conditions favorable for fish meat production are the same again. To achieve this, a period of
1-3 years is often needed. During the time of plant cultivation, deficiencies of the constructive works of the pond can be repaired, or if needed, the whole reconstruction of the pond can be carried out.
2. 7.2. Main physical and chemical factors affecting productivity
2.1. 7.2.1. Temperature
According to the temperature of water in ponds there are:
1.
Cold-watered
2.
Hot-watered
3.
Tempered-watered fish farms.
The characteristic of cold-watered fishpond farms is that the temperature of water is below 20 °C in summer time. These are primarily trout breeding farms. The temperature of water in hot-watered fishpond farms is permanently above 20 C° in summer time. These farms primarily deal with carp breeding, and recently, an increasing amount of grass carp, big head carp and other species preferring hot water is reared. In temperedwatered fishpond farms according to the requirements of brood species, temperature of the water is controlled artificially. These pond farms are built in order to achieve a more efficient propagation and fry rearing.
7.2. ábra - Figure 7.2: Density of water according to temperature
The most importat effects/features of the water temperature are: 1) the metabolic rate doubles for every 8°C increase; 2) it influences spawning, growth and also the affect of pathogens. We can differentiate between fish species according to optimum water. These are warmwater, coolwater and coldwater species.
55
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
It is the most influential biological factor (see above) but it can also be an economic factor (i.e. energy requirement -> feed & growth rate), it also affects oxygen solubility and Q10 (i.e., metabolism), O2 consumption. As one result, it can be impractical to maintain in outdoor cultures or very large-scale. The physiological processes affected are:
• Respiratory rate (metabolic rate, it increases with temperature; fish consume oxygen 2-3x faster at 30°C vs.
20°C)
• Efficiency of feeding/assimilation -> growth rate
• Growth -> time required
•
Behavior -> activities
• Reproduction -> spawning
Each species has a characteristic growth curve with an optimum range, and also have upper and lower temperature limits (lower lethal limit, upper lethal limit).Outside tolerable temperature range, disease and stress become more prevalent.
7.3. ábra - Picture 7.3: Temperature growth and mortality
2.2. 7.2.2. Dissolved Oxygen (D.O.)
D.O. consumption are affected by water temperature (2-3x growth for every 10oC incrase), environmental
(medium) D.O. concentration (determines lower limit), fish size (respiration greater for small vs. large), level of activity (resting vs. forced) and post-feeding period, etc. (2x, 1-6 hrs post feeding). The oxygen and temperature are interacting with each other:
• Oxygen consumption increases with temperature until a maximum is achieved.
•
Peak consumption rate is maintained over a small temp range.
• Consumption rate decreases rapidly as temp increases.
• Lethal temperature finally achieved.
7.4. ábra - Figure 7.4: Oxigen consumption vs temperature
56
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
One can observe fluctuations in the diel dissolved oxygen concentrations:
• Typical pattern = oxygen max during late afternoon.
• Difference in surface vs. benthic for stratified ponds.
• Dry season = faster heating at surface and less variation.
7.5. ábra - Figure 7.5: DO fluctuation
Inadequate DO can cause mortality and contribute to chronic stress and ill health. The solubility is dependent of temperature, stratification and water salinity. The safe levels for fish are: greater than 5 mg/L for salmonidsgreater than 3 mg/L for warm water fish. Uptake influenced by condition of gills, where the partial pressures of O2 and CO2are important, and the demand may not be met if lamellae are not healthy. Water DO levels below saturation can adequately provide saturation of hemoglobin, however a safety margin should be maintained.
DO levels are also dependent on the water temperature, because the metabolic increases with temperature, and dependent on demands of organisms, taking into consideration the energetic demands: swimming, digestion, etc., energetic costs of ventilation and the efficiency of uptake varies in species. Stratification can cause dissolved oxygen and temperature to vary at different depths in the same pond.
7.6. ábra - Figure 7.6: Dissolved oxygen and water temperature
57
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
2.3. 7.2.3. pH pH is a measure of acidity (hydrogen ion concentration) in water or soil. We can measure of the hydrogen ion concentration: 1-14 scale, where less than 7 is acidic and greater than 7 is basic. The safe range for fish is generally 6.5-9.0, but it is variable according to species.The risk factor is mainly the increase of free ammonia in alkaline conditions, which is more poisonous than ammonium.
2.4. 7.2.4. Carbon dioxide
Unlike oxygen carbon dioxide is highly soluble in water. The solubility being higher at low temperature (a sin case of other gases). CO2 stays in free (dissolved) or bound from (bicarborate and carbonate) in water depending on the pH of the water. The biological role of CO2 is source for carbon fixation (photosynthesis), coming from by-product of respiration of fish and phytoplankton, or from wells (carboniferous rock i.e. black shale, coal. As obvious, low pH waters will have high dissolved CO2 and waters above pH 8.36, are free from dissolved CO2. The removal can happen with intense aeration or by buffers, such as calcium carbonate and/or sodium bicarbonate.
2.5. 7.2.5. Alkalinity and Hardness
Alkalinity is divisible into bicarbonate alkalinity and carbonate alkalinity and in some cases hydroxide alkalinity. In most waters bicarbonates (HCO-3) and carbonates (CO=3) are the major bases, but others can also be important under particular conditions. Total alkalinity of natural waters may range from 5 mg to several hundreds per litre (as CaCO3). The alkalinity often reflects the carbonate contents of the rocks and soils of the water shed and bottom muds. Water of arid regions may also have highly alkaline waters. For biological purposes a total alkalinity over 40 mg of CaCO3/litre is considered to indicate hard waters The form alkalinity takes is linked to pH of the system. Alkalinity buffers against diurnal variations in pH.
7.7. ábra - Figure 7.7: Main factors of alkalinity and hardness
58
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
2.6. 7.2.6. Nitrogen forms
Nitrogen forms are the key to all aquatic food webs. The types in water can be dissolved gas, ammonia (ionized
- NH4+ or un-ionized - NH3), nitrite (NO2-) and nitrate (NO3-).
7.8. ábra - Figure 7.8: The nitrogen cycle
Ammonia (NH3) results from the breakdown of fish feed, and waste un-ionized ammonia concentration is a function of pH and temperature. Chronic exposure (unionized form) are lethal to fish: 0.06 mg/L is toxic to warm water fish and 0.03 mg/L is toxic to salmonids. Total ammonia nitrogen (TAN ) is a measure of the unionized-ammonia (NH3) and ammonium levels (NH4+) in the water. The ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature. To convert one mole of ammonia to nitrate requires 3 moles oxygen, moreover, nitrification is an acidifying reaction.
Nitrite (NO2-) is the intermediate product in the breakdown of ammonia to nitrate (nitrification). Nitrite levels greater than 0.5 to 0.6 mg/L or 10 times higher than the toxic threshold for unionized ammonia are toxic to fish.
Catfish will tolerate 13 mg/L, Salmonids will tolerate <0.3 mg/L. Decreasing pH increases toxicity, and the main cause of Brown blood disease (Methemoglobinemia). It means that iron in the heme molecule is reduced and cannot transport oxygen, and blood appears dark in color and fish cannot meet oxygen demands. The treatment can be done with salt, because the chloride ions out-compete nitrite. The recommended 10:1 ratio.
Another cause is the hypertrophy and hyperplasia in the gill lamellae and lesions/hemorrhaging in thymus.
Nitrate (NO3-) is the final breakdown product in the oxidation of ammonia. Nitrate is relatively nontoxic to fish at concentrations up to 3.0 mg/L, but may be problem in embryo development.
7.9. ábra - Figure 7.9: Process of nitrification
59
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
2.7. 7.2.7. Hydrogen Sulfide
The source of HS can be from well water, or in ponds the shift from aerobic to anaerobic breakdown of wastes.
It can also develop under net pens. HS is extremely toxic to fish, so its removal is crucial, and can be done via intense aeration, and, in the long run by draining and drying of ponds.
2.8. 7.2.8. Solids
The solods, especially suspended solids are potential problems. They are source of irritation/nutrients on gills, inflammation and damage to gills, give way to bacterial or fungal colonization on gill surface, reduce oxygen transport. The most sensitive are salmonids, but 80 - 100 ppm TSS reasonable. TSS can also cause environmental load when draining the ponds at total harvest. Technologies are required to avoid solids exposure to inland waters, because they are the primary vectors of diseases.
Fish farms ponds silted up are dried out and used for crop production for 1-3 years, whereas the silt is decomposed and utilised. The silt deposition can be decreased by sub aquatic bottom cultivation and by the increase of fish population, which can utilise the nutrients in the lake in several ways.
3. 7.3. Biological factors
In fish farms the application of natural and artificial fertilisers, protection of the habitats and controlling the composition of the fish population contribute to create such environmental conditions, which provide the increase of biological production. However, the interventions might have disadvantageous results too, so it can be carried out by only an expert, who has the knowledge of the principals of aquatic life, of the life of different organisms and their requirements for their environment.
3.1. 7.3.1 Freshwater plankton
7.10. ábra - Figure 7.10: Phytoplankton
7.11. ábra - Figure 7.11: Zoooplankton (Cladocera&Copepoda)
60
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
Fish breeders regularly follow the changes in the quality and quantity of plankton with attention. For taking a sample of plankton, it is common to use a plankton-net made of 50-100 micron mesh sieve. Considering that the number and the composition of species in the plankton in different water depth change in each part of the day, a proper sample can be taken by a waterspout sampler, invented by Woynarovich. In different sectors of the pond experts take samples of the water with ladles and they strain this samples through the plankton-net. The strained sample of 50 litres of pond water is enough for comparison and evaluation.
When examining the sample of the plankton the quantity, the dominant species and the ratio of their age group must be determined. The results show not only the situation at that time, but also let the expert come to a conclusion about the plankton dynamic system expected in the coming 1-2 weeks. For examining the benthos organisms a silt excavator is applied. The grasped silt is strained a 1mm mesh sieve and the plankton organisms remaining on the sieve are collected with tweezers. It is enough to collect this sample from 10 different places.
The examination focuses on the determination of the quantity and the composition.
If the living world of the fishpond is examined regularly in every 1 or 2 weeks, the result is a quite valuable database. On the basis of this information the fish meat production capacity of the ponds can be suitably characterized and plans for production development m the coming years can be established on a higher degree.
3.2. 7.3.2. Plankton enhancement by fertilisation
The quantity and quality of the natural source of feed highly determines the yield. In case of intensive pond fanning the producer has to do everything to secure proper quantity and quality of plankton for fishes. The most important intervention to increase natural source of feed is fertilising ponds. This is the way, which provides most access to the biological life of the fishpond. It can supplement those elements, which' shortfall slows the natural cycle of materials and hinders the farmer in achieving higher yields.
In ponds with low natural feed capacity it would be useless trying to improve yields economically only with feeding. In such cases the only solution is to first improve natural feed by fertilising the pond and only then adding feed as needed. Farmers may use artificial fertilisers and manure as well. The effect of different kinds of manure is diverse, because they contain all the elements, which help the development of water organisms. For pond fertilising pig and poultry manure is used commonly. The efficiency of apportioned manure is highly dependent from the fertilising technology. In the pond culture practice technologies developed out in the 1960es. Formerly - as in plant cultivation - manure was dispersed over the bottom of drained ponds.
Maucha and Woynarovich created the new and up to date method of pond fertilising with manure. According to this method organic fertilisers should be sprayed into the water of the pond, in several portions. In this way organic material decomposes faster and continuously ensures the nutrients needed for building up organic material. In the case of fry rearing ponds 10-20 t organic fertiliser should be used, in finishing and fattening ponds 4-5 t will do.
3.3. 7.3.3. Plankton enhancement by duck farming
Practically the best solution is to dissolve the manure in water near the pond and spray it over the water evenly in the proper concentration. That is the basis of the method when fertilisation is achieved by rearing water birds
(mainly duck) on the pond and using their manure as fertiliser. The widespread of broiler duck keeping made the use of this method common. The big advantage of this method not only that ducks reach 2.3-2.5 kg body weight at the age of 47-50 days, but because of the fertilising effect fish yields may significantly increase.
61
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
Ducks are hardened for 18-20 days and then placed over the ponds. On the ponds either Kellermann-platforms or artificial islands -according to the method of Fish Culture Institute Szarvas- are built. That is where the feeding of ducks takes place and where they can rest. If the platforms or islands scattered over the pond, the ducks will swim around the whole pond and this secures the even distribution of manure. One duck produces 2 kg dry material of manure over the 1 month period of pond rearing. As an effect fish yield will be increased with
0.3-0.4 kg after each duck,
Stock density should be 200-300 duck/ha. During the season (from April to September) 4 groups can be reared on finishing and fattening ponds. This means an average of 1000 duck/ha, which result in a 300-400 kg/ha excess fish production. On the basis of the above written the consequence is that the most economic method of organic fertilisation of fishponds is pond duck rearing.
However not every fish farm and not every pond is suitable for duck rearing. Thus there is a growing attention on artificial fertilisers. The use of these materials is more favourable because of several aspects:
• the agent is in high concentration,
• quantity and the balance of components can be harmonised with the needs,
• transporting, storing and dosing is cheaper and more simple,
• have better effect on the oxygen supply of ponds.
3.4. 7.3.4. Use of artificial fertilisers
Pond fertilisation can sometimes are dependent on artificial fertilisers. However, in fisheries bibliography - despite of the use of phosphorous fertilisers for a long time - there is no consistent opinion about the dose of portions, frequency and conditions of use. This is also true in the aspect of nitrogen fertilisers, which use in pond culture is in the beginning phase.
Some general advice can be established from results of researches. Firstly, that nitrogen and phosphorous fertilisers have the best effect if applied combined. If there is a minimum of either nitrogen or phosphorous the other can not be utilised either. Theoretically if every condition -that has an effect on production- is proper, then keeping a balance between the dissolved nitrogen and phosphorous in the water, would make possible to reach extreme high yields. Yet, keeping the right balance is very hard, because utilisation of fertilisers depends from many factors, apart from synchronised application.
In case of using artificial fertilisers the water chemistry should be checked regularly, but in itself do not have an effect on the quantity and distribution of fertilisers. The examination should be extended over the whole niche of water, because this is the only way to get answers on arising problems. Biological monitoring gives information on the needed quantity and time distribution, while chemical examination of water on the proper N:P balance.
An important factor of fertiliser utilisation is proper portioning. The best effect can be achieved with several applications of the dissolved fertiliser. From the view of work organisation and fertiliser utilisation one application weekly is advisable. Theoretically daily application would have the best effect, but the results are not in direct ratio to the costs of application.
3.5. 7.3.5. Nutrient management in practice
The most serious problem of pond fertilisation is the distribution in time. During different parts of the season securing the high biological production needs different levels of fertilisers. Generally applies, that in fishponds after abundance of plankton organisms in spring, there is a lack of natural source of feed (from June to August in moderate climate).
At the same time, the need of fishes for feed and the intensity of metabolism is the highest in the latter time period. If there is not enough natural feed, then feed conversion and flesh quality (fish became fatty) decreases while production costs increases. If with proper timing this lack of natural feed is ceased, the fanner made big efforts to increase production efficiently. But there is not a given formula for this, because the proper timing depends on many factors. The most important are the following:
• the phisical, chemical and biological qualities of the pond,
62
Created by XMLmind XSL-FO Converter .
7. Applied hydrobiology – plankton dynamics
• the stocking,
• the time of filling up with water,
• meteorological factors.
The most commonly used fertilisers in fish pond culture are ammoniumnitrate, carbamide and superphosphate.
Dose per hectare:
• fry rearing ponds: 100-200 kg
• finishing and fattening ponds: 200-300 kg
The right balance of nitrogen and phosphorous is determined after chemical analysis of pond water. In some cases there might be a need for liming also.
On one hand lime is a nutrient, on the other hand is a antiseptic. Especially in waters which poor in calcium and has a low pH value, lime increases productivity. It increases the utilisation of nitrogen, phosphorous and carbon compounds and enhances the physique-chemical living conditions of water organisms. It is also used to fight the negative effects of algal bloom. The dose is established after examining conditions on the pond. Usually 0.2-0.3 t/ha lime is applied. It is applied on the dry bottom or after flooding sprayed over the surface.
63
Created by XMLmind XSL-FO Converter .
8. fejezet - 8. Fish biology, propagation larval/fry rearing and broodstock management
Fishing is one of the oldest trades of the humanity. The people caught more fish as their needs were and they started to keep fish in storage ponds for later using. Then they observed that some species could produce propagation in storage ponds. The oldest history of fish breeding is came from China (BC 2400) and Japan (BC
1900) where the common carp was bred directly. In first case Jacobi fertilised trout eggs with artificial method between 1763 and 1765. After this Remi and Gehin produced the biological and technical background for professional trout breeding.Vranskiy worked out the methodology of dry fertilisation which method is used in our time also.In Europe Tamás Dubics established the modern breeding of common carp. He observed the natural reproduction of carp and modelled it in small ponds with grass on the bottom of pond.
Fundamental changes in carp breeding have taken place in the last few decades. More and more emphasis has been placed on large scale operations, industry production security, centralisation of breeding conditions, economical use of manpower.Increasing technical knowledge and technical capability created incentives for industrial development. The incentives were also promoted by the increasing demand for fry for market fish production; foundations of these new methods were laid in the 1930’s. The fundamental laws for reproductive system of fish were discovered by the Russian scientist Gerbilski and his research team and are the basis for induced ovulation for propagation of fish used today. The main principle is that fish ready for ovulation and spawning and in the resting stage can be treated with gonadotropic hormones and induced to spawn. As a result of this process, egg separation and release from the ovaries and accumulation of sperm can take place without the presence of external “spawning environment” conditions. Natural stimulation by the spawning environment to condition the fish became unnecessary. This “natural” spawning environment for some fish species has been very difficult or even impossible to create.
The first hormone-simulated breeding of carp was initiated in the 1940’s. A method for eliminating the stickiness the eggs had not been found at that time and the hormone treatment was used only to accelerate the spawning in small ponds. As expected the results were not always favourable. The advantage lies in the eggs ripening and induced fertilisation and larval rearing but the protected environment was not developed at that time. These experiments were temporarily suspended during the war years and were reinitiated in the early
1950’s.Research workers tried to eliminate the sticky quality of eggs to allow them to be incubated in jars or in containers similar to trout or pike eggs where the larvae could be kept under protected conditions.
Woynarovich in 1961 reported a simple and safe salt carbamide method for carp egg incubation. Today his method is practised.The next step for effective propagation was the safe rearing of the feeding larvae, the end product of hatchery efforts and which caused great difficulties in the beginning.A complex breeding and fry rearing method described can be used in both small and large hatcheries. It should be noted that these were developed for application by large-scale operations.
In this syllabi there were used several publications from different book because this material was not written for lecture notes, it is only a short information about the reproduction mechanism in fish. For writing of this syllabi was used the Fish biology lecture notes from Prof. Dr. C.J.J. Richter, Fish physiology volume IX. (Fish gamete preservation and spermatozoan physiology by Joachim Stoss), Fish physiology volume III. (Development: eggs and larvae by J.H.S. Blaxter) and Special methods in pond fish husbandry from L. Horváth, G. Tamás and I.
Tölg.
1. 8.1. Reproduction biology
1.1. 8.1.1. General aspects of fish reproduction
Teleost display a variety of reproductive behaviors. At one extreme, breeding individuals within a school simply release gametes freely into the water. In other species, breeding may involve preparation of a nest of a territory, and elaborate pair formation and mating ceremonies. This may be followed by extended care of the eggs and young by one or both sexes.In generally the fish has two sexes in different individual. The gonads produce the
64
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management gametes in ovary and testis. The production of gametes is harmonised with other vital process by blood. The hyphophysis regulates the gonads with hormones through the blood. The fish can not feed their progeny like the mammals so the maturated eggs is very large because they include lots of yolk for the early stage of life.
The fish release the eggs into the water freely so there is some special thinks. The female releases the eggs into the water through their genital opening and the males admit the sperm to them at the same time. The sperm cells find the eggs with active moving and they are directed to the micropyle by a chemical, namely gamons. The sperm cells are inactivated in the testis and they will be activated for moving by the water. After fertilisation the eggs will start to swell and after few minutes the micropyle will be closed and cell division will start.
Next phase when the embryo or larvae hatch from the egg. In first stage of larval period the fish use their yolk and later the exogen and endogen nutrition happen together at short time. In second phase the larvae use only exogen nutrition and at the end of larval period the fish will be same with the adults of given species.
1.2. 8.1.2. Larval development
Before the hatching the oxygen-diffusion is impeded so the embryo wants to come out from the low oxygen egg inside. Some enzyme also helps for hatching and the wart on the head start to also produce enzymes, which help the hatching. After hatching there are two phases, first is the non-feeding; second is the feeding larvae state.
Non-feeding larval period
At the hatching larva is usually transparent with some pigment spots of unknown function. Notochord and myotomes are clear with usually little development of cartilage or ossification in the skeleton. A full complement of fins is rarely present, but a primordial fin fold is well developed in the sagittal plane. The mouth and jaws may not yet have appeared, and the gut is a straight tube. Although the heart functions for a considerable period before hatching, the blood is colourless in the majority of species and the circulation and respiratory systems poorly developed. The yolk sac is relatively enormous with, presumably, hydrodynamic disadvantages. Pigmentation of the eyes is very variable, but where the eye is not functioning at hatching it very soon develops. The kidney is usually pronephric with very few glomeruli. Very little is known about the endocrine gland, gonads, and other organs of the body cavity at such an early stage. As the yolk is resorbed, he mouth begins to function, the gut and the eyes develop further, and the larva becomes fitted for transfer to sources of external food. One of the earlier systems to develop is that responsible for locomotion and support the primordial fin being fairly soon replaced be median fins and the skeleton laid down. This is one of the better known aspects of later development because it is a system less easily damaged in such delicate organisms and because of the importance of meristic characters in racial studies of fish. Branchial replaces cutaneous respiration as the gill aches and filaments appear. The swim bladder may or may not be present during the larval phase. It is possible that this and the eyes, which are potentially dangerous in making the transparent larva visible, are silvered in such a why as to render the inconspicuous.
Feeding larval period
A clear change or metamorphosis from the larval to adult form is to be found in many species. In others there may be a number of less marked metamorphoses, e.g., in salmonids and eels. The most obvious signs are the laying down of scales and other pigmentation and often the first appearance of haemoglobin in the circulation.
The swim bladder and lateral line may also developed first at this stage. In flatfish there is rotation of the optic region of the skull and the change in the normal orientation of the body so that they eventually come to lie on one side. There are often concomitant changes in distribution and behaviour such as schooling. The time to reach metamorphosis may be a matter of days in tropical species, a few weeks or months in the majority of fish from temperate latitudes, or periods of years in the sturgeon and eel. It is controlled not only genetically but also be temperature and food supply which may affects the rate of growth, and possibly be social factors as well.
1.3. 8.1.3. Brain and neurohumoral regulation of reproduction
Environmental stimuli together with an endogenous rhythm regulate vitellogenesis with concomitant growth of the ovary. The reception of the stimuli is mediated by the nervous system and involves the passage of information from sensory organs to the brain. This neural information upon reaching the hypothalamus determines the activity of the pituitary gland by of chemical messengers termed releasing hormones. The gonadotropin – releasing hormone (GnRH) regulated the secretion of gonadotropin. The target cells for gonadotropin appear to be the granulosa or special thecal cells and the sex steroid produced there in its turn triggers the production of vitellogenin by the liver cells. Vitellogenin is transported by the blood to the ovaries
65
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management there it is incorporated into the yolk granules of vitellogenic oocytes. A direct action of gonadotropin on the vitellogenic oocyte is needed to make his incorporation possible. Recent research with chum salmon has revealed that two distinct gonatropins (GTH-I and GTH-oestradiol production by mid-vitellogenic ovarian follicles. GTH-I maybe considered to be involved in sex differentiation, vitellogenesis and spermatogenesis and GTH-I. GTH-II appears to differ from GTH-I, showing a high specif
-progesterone production during oocyte maturation. In addition also two types of GnRH have been found.
Gonadal growth can, in principle, be stimulated by hormonal treatment and by improving environmental conditions including feeding. The administration of sex steroids resulted in positive and negative effects. For stimulation of vitellogenesis, positive results were obtained by administration of pituitary extracts in the blood circulation.
The timing of spawning in fish is often triggered by the presence of conspecific of both sexes and a number of environmental factors such as a suitable spawning substrate, rainfall, temperature and changes in electrolyte concentration of the water. The reception of these stimuli is mediated by the sensory organs, hypothalamus, pituitary and gonad. Gonadotropin secretion by the pituitary probably mainly GTH-II is regulated by gonadotropin-releasing hormone (GnRH) and by dopamine acting as a gonadotropin- releasing inhibitory factor.
The effect of the releasing hormone is to stimulate the production of GTH in the pituitary and its subsequent release into the vascular system of the pituitary. GTH is then transported by the blood circulation to the target organ the gonad, where it initiates the production of sex steroids. In males of some species, 11-ketotosterone or
-hydroxytestosterone is produced. In the ovary, the steroidogenic tissue of the postvitellogenic follicle produces the steroid. This steroid is probably the most common mediator for oocyte maturation. It induces the germinal vesicle migration followed by the germinal vesicle breakdown. Ovulation is the subsequent event and involves the excursion of oocytes from the follicles into the ovarian cavity. This process consists or hydration of the oocyte and contraction of the smooth muscles of the follicular envelope. Ovulation appears to be independent of pituitary control. Prostaglandins have been suggested as mediators for ovulation and they are possibly produced by prostaglandogenic extrafollicular tissue of the mature ovary. Ovulation of eggs occurs during spawning. The ovulated eggs, arrested in the metaphase of the second meiotic division, can be retained for some time in the ovarian cavity before they are oviposited. The role of pheromones of male and female conspecific in relation to growth, maturation, ovulation and oviposition of eggs is presently under investigation.
2. 8.2. Environmental effects
The natural reproductive cycles of some freshwater fish species from tropical and temperate regions are described. The endogenous rhythms in reproduction and their synchronisation with the environment appeared to be influenced by climatic factors such as light, temperature and rainfall. The mediation of these factors, governing the reproduction of fish, is under the control of the neuroendocrine system. The reproductive hormones involved influence the subsequent steps of gametogenesis e.g. proliferation of the initial germ cells and growth and maturation of the ultimate sex cells. The interest of fish culturists to extend the natural spawning season of commercial fish species has stimulated research on manipulation of the reproductive system.
Experiments on the environmental control of reproduction, including the effects of photoperiod and temperature on the reproductive performance of fish, are described. Particular attention is given to influencing the reproductive cycles in order to induce precocious recrudescence and to postpone regression of the gonads.
Reproduction of common carp in temperate climates is naturally controlled by the season of the year. In the tropics, carp spawning is mainly influenced by rainfall; hence spawning occurs during the rainy season.Only sexually ripe fish are able to reproduce. Sexual ripening is a long and slow process. The development of the gametes is fundamentally influenced by environmental temperature. Consequently the ripening of the eggs and sperm under tropical conditions is faster than in the temperate zone, where yolk formation almost stops during the cold winter season.
Most important environmental factors of the carp are next:
• constant temperature of water of 16 – 18 oC
• a spawn area should contain places overgrown with grass or rich in aquatic weeds
• flooding water
• both sexes must contact one another near likely spawning site.
66
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management
If any of the prerequisite conditions for spawning fail, if toxic factors appear in the water from pollution or low oxygen levels occur, the fish will not spawn.
8.1. ábra - Figure 8.1: Environmental factors of breeding
To understand the phisiological conditions of spawning we must understand that the gonads of sexually mature fish gametes are waiting for proper spawning conditions and in some cases it may not occur for several months.
This dormant stage of development occurs to enhance the survival ability of the species since it enables the ripe spawners to wait or delay spawning until optimum spawning conditions occurs. During this period of waiting the fish are also in a comparatively stagnant or resting state and a balanced hormone activity is maintained.
When proper spawning conditions develop, essential and sudden hormone changes take place in the healthy mature fish. Sense organs in the fish active the central nervous system and pituitary glands to stimulate the flow of gonadotropic hormones into the blood stream. This stimulates the separation of eggs and the discharge of the sperm, and produces the physiological conditions required for spawning. Group fertilisation often occurs during crowded spawning activity since eggs and sperm are released into the water at the same time. Sperm cells are stimulated by the water and attempt to find the opening on the chorion, where the first sperm cell penetrates and completes fertilisation. Water is then absorbed between the eggshell and the fertile cell, the egg swells and mitosis begins. Embryogenesis lasts for 4 – 5 days with carp and then the larva is hatched. The larva hangs motionless on plants without feeding for several days. After 4- 5 days the swim bladder is filled with air and the larva starts to feed on tiny plankton organisms. Final development of internal organs occurs after approximately one month and then a fully developed carp fry swims throughout the water column. Under natural conditions only a small percent of the progeny will survive.
3. 8.3. Propagation of common carp
3.1. 8.3.1. Reproduction in nature
The common carp is a termophyle species and its reproduction is controlled naturally by the season of the year.
The reproduction of common carp in tropics mainly influenced by rainfall, when the reproduction occurs during the rainy season.Carp can reproduce in any place where the water temperature reaches 20 OC at least 3 – 4 months and the environment is also adequate for reproduction.
The following conditions are necessary for carp spawning:
• water warming in spring is slow and is often interrupted. For successful carp spawning constant temperature of water of 16 – 18 OC. is necessary for a period of time.
• gradual increase of water temperature
67
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock
• places overgrown with grass for the sticky eggs management
• both sexes present on same place and same time
• flooding water also has a beneficial effect
3.2. 8.3.2. Semi-natural breeding
The natural breeding is when the created environmental conditions in artificial pond are produced to produce the natural environmental conditions. This environment will induce spawning of carp under controlled conditions.
The bottom of the spawning ponds are overgrowth with grass when the fry will grown under natural but controlled conditions. Later the pond is flooded with water and the broodstocks are stocked into the pond. In the next period, when the environmental factors are adequate for reproduction, the spawning will started. When the spawning is finished the spawners are removed from the pond and the larvae will grow up on this place. This method gives more protection for the offspring than the natural reproduction.
8.2. ábra - Figure 8.2: Steps of semi-natural breeding
3.3. 8.3.3 Hatchery induced breeding
Keeping spawners
The holding or keeping of spawners is one of the key requirements of successful propagation. The common carp’s sexual maturation depends on the water temperature, so in Southern Europe it will be maturated in 2 – 4 years, in Central Europe in 4 – 5 years and under tropical conditions within the first year.
The general rules of broodstock keeping are the next:
1.
select healthy fish with good physical characteristics for breeding,
2.
animal protein in their food, because it provides the amino acids for the growth,
3.
holding ripe spawners together for development of sexual products (both males and females),
4.
optimal environmental and nutritional conditions will be guaranteed,
5.
low stocking density of broodstock,
68
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management
6.
before stocking held them for a few days either in tanks with good water and food supply,
7.
during the spawning the fish will lose 10-20 % of their body weight in sexual products
8.
post spawning ponds with adequate feed for reproduction new eggs and to promote renewed yolk,
9.
energy rich feed for reproduction of new eggs (starch and fat),
10.
best protein is the organisms living in the holding ponds,
11.
100-200 spawner/ha stocking density,
12.
13.
14.
15.
16.
2-5 % feed/body weight which rich in energy and protein, fertilisation with 150 kg carbamide and 100 kg phosphate/ha or 200-300 kg animal manure/ha, the storage will be in deep pond for the wintering season, continuous water supply during the whole year, predator fish is stocked to eat trash fish (few hundred),
17.
ones, if the new spawners are kept with old spawners, it has a good effect for the sexual maturation of young
18.
the broodstock will produce for the next breeding season a new developed eggs at 10-15 % of body weight
Preparation for propagation
Before the propagation spawners need to be separated by sexes. The optimal time for the separation is when the water temperature reaches up to 12 – 15 OC, because on this temperature they will start the natural reproduction and the sexual products will be lost for the induced and controlled propagation.In this time the female has medium soft, swollen belly which is caused by the developed ovary. The male produces white milt after slight pressure of belly.In this time the feeding should be increased with fed which is reach in animal protein and vitamins. This feeding is different from the normal summer time feeding regime. The hatchery induced propagation will start when the spawners are moved into the hatchery and put into tanks. The environmental effects have a very important role in this period. The hatchery can be quiet because the stress which is caused by the big noise and continuous disturbing can cause some trouble. The water exchange in the tank is 4-6 l water/min per spawner. If the oxygen level of the water is not enough high the aeration of the tank is also needed. During the induced propagation the used sex ratio is 2 female for 1 male
Anaesthetisation
The mechanical stress can also cause a wrong result of propagation, so it is need to anaesthetise the fish before the different treatments. For the anaesthetisation mainly used chemical the MS 222, in 1:10,000 concentration.
Fish should remain anaesthetised for a minimum time period and only as deep as needed. The gill cover movement should be monitored the level of anaesthesia. When too much fish are in the water the oxygen deficiency will be occurred. When this occurs oxygen should be provided. After the anaesthetisation and treatment of spawners they can be put into an other tank which is filled with normal water. If the fish are stocked back to the storage tank use of a marking is needed for identification of treated fish from the others. The fin clipping (dorsal fin) is a rapid method and it will be regenerated after a short period. During the first treatment and anaesthetisation the fish will be weighted because this data will be the basis of calculation the dose of hormone.During the second period is important to close the genital opening before second injection and the ovulated cells can not be released into the tank. The method of closing of genital opening is showed on figure 5.1.
Hormone treatment
The used hormone prepared from the pituitary glands of identical species. The maturated individuals have the best pituitary gland for the propagation. Large scale collection may be accomplished with a low voltage electric drill and a special indented pipe drill-head to penetrate the part of the skull in which the gland is seated. The extracted plug is removed from the head and the bone and tissue can also removed from the drill. The pituitary
69
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management gland can remove with a dentist’s curette. The gland is full with fat and water so it is need to remove them.
After the collection the glands are placed into acetone for 24 hours. During this time the fat and water will be removed and the glands are dried at room temperature. When the glands are dry they are sorted according to size and placed into desiccator over calcium chloride until used.
The common carp has a good effect if the total hormone dose is used in two doses. The first injection is the 10
% of total dose (bring the eggs into stage pre-ovulation). The second dose is 90 % which induces ovulation. The dose of dry pituitary gland is 4,0 –4,5 mg per kg of body weight, when only one injection is used the dose is a little less (3,5 – 4,0 mg/kg of body weight.When two injections are used the first will happen 24 hours before the planned stripping and the second 12 hours before planned stripping.
Preparation of pituitary solution starts with the calculation of necessary amount on the basis of body weight. In the second step the glands are pulverised with a mortar and pestle. After this step the power of the glands is dissolved in fish physiological solution (0.65 % NaCl). This solution is taken up in a syringe from the mortar.
The injection can be placed into the dorsal muscle or under the dorsal fin into the body cavity.
During the propagation uses of broodstocks, which have same weight is better and easier. The general weight of one pituitary gland is 3-4 mg, which is dissolved in 0.2 ml solution. During the treatment of glands it is needed to save 10 % reserve. The first dose is approximated in generally (5-6 kg spawner/one (3-4 mg) pituitary gland in 1 ml solution).The male is treated only once with 2-3.5 mg of pituitary for 1 kg of body weight at the time of first treatment of the female.
8.3. ábra - Figure 8.3: Closing the cloaka and hormone induction
Ripening of spawners
Time of ovulation depend on the number of treatment. When only one treatment is used the ovulation would take 16-18 hours in water 21-22 OC (360-340 hour temperature degrees) after the injection.When two treatments are used the ovulation may be expected 12-13 hours after second treatment (240-260 hour-degree).
Important to keep undisturbed environment during the hatchery treatment until restocking of the broodstocks to the storage pond, because the stress frustrates ovulation. The main factors are the next:
• quiet
• constant temperature
• constant high oxygen level
• constant water exchange
Generally early morning on the day of stripping a male is placed with female, and he will choose the ripest female from the tank. As the discharge of eggs is prevented by the suture, stripping should be started only after
20-30 min of vigorous spawning activity.When the carps are ready for stripping (ovulated) remove them from the tank to complete ovulation and should be anaesthetised again.After stripping spawners should be placed back into recovery ponds.
70
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management
Stripping and fertilisation
The most important rule of the artificial propagation is “no water is mixed with the sexual products”. Spawners therefore, aredried with a cloth before stripping. The eggs are collected separate containers/spawners and weight of eggs is measured after stripping. The number of eggs is calculated which calculation is based on the body weight of the spawners.
8.4. ábra - Figure 8.4: Steps of hatchery induced breeding
For the sure fertilisation two or more males’ milt are used for one female eggs. The collection of milt will be free of water also (see earlier). The milt and eggs are mixed in plastic bowl with the next ratio: 100 eggs: 1 milt.
After the mixing the fertilising solution is added. There are two different types of solution, solution I is 10 l of pond water with 40 g salt and 30 g carbamide. The time of treatment is 5-15 min when changed 8 - 10 times.
During this time eggs stickiness is eliminated and the sperms are activated. Fertilisation of eggs takes place and it begin to swell.
During the swelling period the fertilisation solution is added slowly in small quantities and stirred slowly. Extra sperm and protein dissolved gradually from the surface and eggs is poured out and is replaced by fresh solution.
Swelling of eggs
It becomes visible to the naked eye in 10-20 min after fertilisation and the second solution is added after this treatment. This solution includes 40 g salt and 160 g carbamide in 10 l of pond water. It is used continuously for
20 min when changed 5-7 times and it is stirred with plastic spoon. After these the eggs are replaced into bigger bowl and change the second solution in first 20min 4-5 times. The 20 min period start again other 2 times change of solution. After one hour eggs grow 3-6 times. If the eggs seem soft further swelling is needed but it is elastic and hard the desired stage is reached. This generally occurs after 1-1.1 hrs.
After this treatment tannic acid solution is added to eliminate completely the residual stickiness. Composition of tannic acid is: 5-7 g tannic acid in 10 l of water. 0.5-0.8 l of this solution is added to 10 l of swollen eggs in a container 20 l. Than the eggs are kept in this solution for 20 sec. and clean water is added to the eggs. This procedure is repeated max. 3 times if it is need. The dose of tannic acid can decrease when in the second step
71
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management only 0.5 l solution is added to 10 l swollen eggs. Tannic acid can kill the eggs if the treatment is longer than the described time.
After this treatment the eggs can put into the hatching glasses
8.5. ábra - Figure 8.5: “Dry fertilisation”
Ripening of eggs
The swollen eggs cleared from adhering protein will sink to the bottom of the hatching glasses, where they should be moved and turned constantly by a water flow. More than 100,000 eggs suitable in 7-9 l Zuger jar. At the beginning the oxygen requirement of eggs is low, 0.5-0.7 l/min and after blastula stage starts, the oxygen requirement of eggs grows rapidly. Immediately before hatching the oxygen requirements is very high. at this stage 1.5-2.5 l/min water flow must be provided (depend on the size of glass).Colour is changed during incubation, first is yellowish, greyish-brown, becoming darker, becoming dark brown or black before hatching.
Malachite green is used once per day to prevent the Saprolegnia infection. The used concentration of malachite green is 1:200,000 for 5 min, but the fish farmer can monitor the treatment by the colour of the water in the
Zuger jar. The concentration is good when the water has light blue colour.Optimum temperature for incubation is 20-24 OC and another temperature causes high mortality, deformation and more Saprolegnia infection.
Hatching of eggs
The eggs are ready to hatch when the firs swimming larvae appear into the jar. In this stage the water flow is stopped so the low oxygen levels promote the movement of the embryo to escape from poor oxygen place. The enzyme production of the gland on the head is accelerated also. These synchronise the hatching in one glass. As soon as the normal water flow is restored after such a restriction, the mass hatching of eggs will begin and if eggs are ready the process will be finished in a few minutes.
8.6. ábra - Figure 8.6: Hatching of eggs in „Zuger” jars
72
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management
Holding non-feeding larvae
The hatched larvae are transferred to holding tanks after the siphoning from the hatching glasses hatched and partly hatched larvae to bowls. After the complete hatching the larvae are placed into 50-200 l keeping tanks when in 50 l tank 100,000 larvae can keep. In a 200 l capacity tank more than 500,000 larvae can keep. This stage is 3-3.5 days on 20 OC when the larva can fill its swim bladders with air, its mouth organ will be ready for exogenous feeding and its gills will be ready for breathing.
First feeding
The best first food of the larvae is suitable only in ponds, complete starter feed for common carp never has same result on growth than the natural food (zooplankton), and the cost of artificial food is very high.If the weather is not suitable for stocking boiled eggs can also used for feeding of larvae. Sometimes the encapsulated eggs and collected zooplankton are also good. The best method when the larvae are transferred to a small well-prepared nursery pond after the 3 days non-feeding period. The feeding is used when the stocking is impeded (cold water, strong winds, technical reasons). During any extended stay in the hatchery, the larvae must be fed every twothree hours but the larvae will die after a week of egg feeding. The best results in mass nursing are always achieved by stocking the larvae into the prepared ponds as soon as possible.
4. 8.4. Propagation of European catfish (Silurus glanis
L.)
4.1. 8.4.1. Reproduction in natural water
Catfish likes the shallow, muddy places which is rich in root. Before the reproduction male dig a nest in the mud among the roots of trees and the female will lay eggs to the roots. The time of reproduction is May – June.
Females reach sexual maturity later than the male which depend on the water temperature. Males reach sexual maturity at age of 4 – 5 and females at 5 – 6 years. Catfish mate in pairs. The reproduction starts when water temperature reaches 22 – 24 OC and does not go under 18 – 19 OC during the night. Males start digging nest and clean the root with vigorous movement of tail fins. It happens a few days before spawning which occurs generally during the night. Ovulation followed by a mating dance. One part of eggs stick to the plant roots in the nest and other part sink into the bottom. The male stays above the nest and supplies the with oxygen rich water by the movement of its tail. The eggs lost its stickiness on the second day and the embryo starts to move and the next day its will hatch. The hatched larvae will stay on the roots with help of their gland on the head. After 3 – 4
73
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management days they will start swimming and the male abandons the nest. The larvae stay in the dark corner of the nest and insure oxygen rich water with vigorous fanning of their tails. The fry start feeding 5 – 7 days after hatching. In the first time move little and stay in groups.
4.2. 8.4.2. Artificial propagation
Broodstock keeping
In a small pond several hundred spawners can be kept and the feeding is 3 – 5 % of body weight per day. The breeders are selected during the autumn harvest and kept in wintering ponds with a 200 – 300 fish/ 1,000 m2 density and 100 – 200 l water/min. The catfish does not eat during the winter but it has a good effect if 200 –
300 kg trash fish are stocked into the wintering pond as a food on the warmer days. In spring the overwintered stocks are selected by sexes what is difficult because the sexual dimorphism become visible only in the mating season.
Different markers can use to identify the sexes. The size and shape of genital papilla of the females is big, broad and protruding with the tip often red, while the papilla of male is pointed and flat. The shape and size of papilla depends on the age, maturation status, health condition and stage of vitello and spermatogenesis. The feeding is also very important during the pre-spawning period.
Treatment of breeders in the hatchery
The artificial propagation can be started when the temperature of water reached to 20 OC. Before the transportation into the hatchery the mouth of spawners must be closed with a wire after anaesthetisation and it will prevent the injuries. For hormone treatment generally acetone dried common carp pituitary gland is used.
The dosage of female is 4 – 4.5 mg/kg body weight and 3 – 4 mg/kg for males. The procedure is same with the common carp. Within 21 – 22 hours after injection the ovulation will happen on 23 – 24 OC water temperature.
It has a good effect if the stripping and ovulation is planned for the early morning hours.
Stripping and fertilisation
The catfish produce smaller numbers of eggs than the common carp, because the mass of ovary is only 10 – 15
% of total body mass. The eggs are not sensitive for the over-maturation and it is easy to strip from the anaesthetised female. The collection of milt is more difficult than the common carp. In the first step the 2/3 part of testis is operated from the body cavity. Later the male is closed with syringe and desinfected locally. The collected testis is cut for small parts. The eggs are distributed for small (100 – 150 g) part and fertilised each portion (2 – 3 ml) immediately after tripping. If the milt is not enough it can press through net fabric onto the egg portions. The used solution for fertilisation is 0.3 % NaCl when 20 – 30 ml is added to 100 g of eggs. The dry stripped eggs and milt are mixed and solution is added to them, when mixing happens by vigorous movement of the bowl. The spoon stile mixing (like common carp treatment) breaks the very sensitive eggs.
After few minutes the fertilised eggs can mix with a plastic spoon together with the continuous adding the fertilisation solution.
8.7. ábra - Figure 8.7: Removal of testes
74
Created by XMLmind XSL-FO Converter .
8. Fish biology, propagation larval/fry rearing and broodstock management
Incubation of eggs
The eggs do not swell and not sticky in the solution so after mixing for 4 – 5 min it can be transferred into the
Zuger jar. There will attach the eggs either to the glass surface or to each other. The oxygen demand during the firs 12 – 15 hours is very low, only 1 l/min water exchange is enough. From the 16 – 20 hours the fungi infection will spread rapidly. In he first step the Saprolegnia will exist on the unfertilised eggs only and from there will spread to the fertilised eggs. The oxygen demand will grow.
After morula stage it needs to remove the eggs from glass surface. Generally it happens with glass tube which is covered by a soft fabric. Other method when an proteolitic enzyme solution is added to the eggs and the water flow is closed for 5 min. During this time the eggs are stirred with a plastic stick and the enzyme solution can rich every eggs and dissolve the characteristic protein-layer responsible for stickiness. After the procedure the eggs will be floating freely in the water.
The eggs will start to swell 8 – 10 hours before hatching in Zuger glass to double of original size. It is reasonable to treat the eggs with Malachite green solution 3 – 4 times during the 2.5 – 3 days of embryogenesis.
Nursing larvae
After the hatching the larvae try to find a stabile attachment surface. It is not possible in the jar so he hatchet and non-hatched larvae are float together with the water and some larvae are not tolerate this position so it is a very important stage of the artificial propagation. When the first larvae can be observed it is need to reduce the water flow to 0.1 – 0.2 l/min. The unfertilised eggs weight is heavier than the fertilised so they will be go to the bottom of jar. They can collect from the bottom. Majority of eggs will hatch after few minutes and this time it must to remove to the larval tanks. The water exchange is low so the hatching enzyme concentration will be higher and the hatching will be complete.
The hatched larvae will be distributed into boxes with 0.5 mm mesh (30 x 40 x 60 cm) and water flow rate of 2
– 4 l/min. In each box 10,000 – 20,000 larvae can kept. The larvae are very sensitive so during the first day they will be kept without disturbance.The larvae will be grey on 2nd day and will fill their swimming-bladder with oxygen on 4th day. This time they swim up to the surface and search feed. They still have yolk-sac but they are ready to collect the suitable exogenous food.
75
Created by XMLmind XSL-FO Converter .
9. fejezet - 9. Fish nutrition and feeds
1. 9.1 Nutrient requirement of fish
Nutrient requirement studies with fish - both for specific nutrients and for gross feed evaluation - involves special short-term or long-therm feeding experiments. In such experiment a given feed (test diets or practical fish feeds) is offered to the fish and various responses, such as growth, feed efficiency, absorption, nutrient accumulation, are studied during and at the end of the experiment. At the same time special physiological or biochemical studies can be conducted at various organisation levels of the body, such as whole body, whole organs, tissues for some specific compounds. For the studies at cellular or subcellular levels, several parts or fractions of the cell can be regarded. The generalized structure of a cell and a mitochondrion is shown on the following graphs. Methods for fractionation of the cell component is also shown below.
In such experiment special care should be taken to avoid other effects than the effect of the varying level of the given nutrient.To ensure this healthy, well adapted fish has to be stocked into the experimental basins. Well aerated, oxygenated water should be supplied to the fish, and accurate distribution of the suitable feed/diet has to be applied.For such feeding experiments, special rearing systems, and special feeding devices (or accurate hand feeding) have to be applied for replicate groups of fish in specially designed feeding regimens.
For gross feed efficiency food conversion rate (FCR= feed offered/weight gain of fish) or fish conversion efficiency (EFF= Weight gain/feed intake) are used. In case of specific nutrient requirement studies special dose-response experiments are carried out. In such experiment graded levels of the specific nutrient are mixed into test diets and the gradually changing response is evaluated. The required nutrient concentrations (minimum, optimum, etc. values) are determined by plotting the growth or other responses against of the concentration (or doses) of the nutrients in the diet.
2. 9.2. Proteins and amino acids
Proteins are major constituent of the animal body, and a liberal and continuous supply is needed throughout life.
The primary aim of fish culture is to transform such dietary protein into fish tissue protein efficiently, which are available and sufficient for the fish, but not suitable for direct human consumption.Natural diets of fish are rich in protein. Genrally, fish require a higher percentage of protein in diet than birds and mammals. This may be because fishes utilize carbohydrates less efficiently. Therefore, some dietary protein may be metabolized for energy.
The amount of dietary protein required by fishes is directly influenced by the indispensible amino acid pattern in the diet. The minimum amount of protein needed to produce maximum growth has been investigated with purified test diets in several species of warmwater fishes. (Such test diets, shown in the Appendix 2 was e.g. the
H440 diet, which is still applicable with some modifications in the composition to most of the related dietary studies.)
The amount of protein that should be provided in practical diets depends largely upon digestibility and amino acid composition. Nonprotein energy of the ration and the quantity of diet consumed by fish also affects the percent of protein that must be present in the diet.
2.1. 9.2.1. Proteins requirments
There are so many variables that affect optimum protein percentage in fish rations that there is difficulty recommending an appropriate protein level for each species of fish at various environmental conditions.
However, the ranges of protein level found in practical diets are summarized for channel catfish, eel, carp, ayu fish, and red sea bream in next table.
9.1. táblázat - Table 9.1: Recommended Protein Levels in Percent of Practical Fish Diets
(As-Fed Basis)
Species Fry to Fingerlings Adults and
76
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
Channel catfish
Fingerlings
35-40 to Subadults
25-36
Brood Fish
28-32
Eel
Carp
Ayu fish
50-56
43-47
44-51
45-50
37-42
45-48
-
28-32
-
Red sea bream 45-54 43-48 -
More exact protein levels, found in requirement studies usind various test diets are shown in the table below.
9.2. táblázat - Table 9.2: Protein requirement of some warmwater fishes
Species of Fish Protein Used in Test Diet Water
Temperature (°C)
Carp
Eel
Casein
Casein+Arg+Cys
23.0
25.0
Crude Protein Level in diet for maximum growth
(%)
38.0
44.5
Channel catfish Casein
Whole egg protein
24.4
26.7
35.0
36.0a
24.0b
Red sea bream Casein+Gelatin 25.0
55.0
a3.410 kcal/kg of diet.
b2.750 kcal/kg of diet.
2.2. 9.2.2. Amino Acid Requirements
Ten essential amino acids have been idendified as indispesible for growth of catfish, carp, red sea bream, two species of eel, and two species of prawns. Diets deficient in any of the indispensible amino acids result in depression of appetite and reduced weight gain. Replacement of the amino acid results in the recovery of appetite and growth.
The high protein requirement of fish is directly related to a relatively high indispensible amino acid requirement when compared with pigs, chicks, and rats (see table on the next page). The requirement for arginine in the eel and carp is considerably higher than that of the young pig and the rat but is only about two-thirds of that of chinook salmon and chicks. Carp require 3.1 percent methionine in their dietary protein in the absence of cystine and 2.3 percent in the presence of 5.2 percent cystine in the diertary protein (or 2 percent cystine in the diet).
77
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
Channel catfish have a methionine requirement of 2.3 percent in the absence of cystine, indicating that a half of the methionine requirement can be replaced by cystine. Methionine requirement for eel was determined to be
3.7 percent in the presence of 1.6 percent cystine, whereas chinook salmon require 1.5 percent of methionine in the presence of 2.5 percent cystine in the dietary protein. Methionine requirement of carp is higher than that of chinook salmon and lower than that of eel. The tryptophan, threonine, and isoleucine requirements of eel are noticeably higher than chinook salmon. The valine, histidine, and leucine requirements of eel are almost the same as that of salmonids.
The isoleucine and leucine requirements of young carp are quite similar to those of chinook salmon. The lysine requirement of catfish is higher than that of eel and chinook salmon. More research needs to bo done on amino acid requirements for important fishes raised in production facilities to formulate practical diets with the least cost and improved efficiency.
A test diet composed of crystalline amino acids results in satisfactory growth for eel, red sea bream, and shrimp.
Supplementation of the most limiting amino acids to a protein diet stumulates growth. Certain other warmwater rishes do not utilize crystalline amino acids efficiently. For example, inferior growth occurs when feeding typical amino acid test diets to carp, catfish, and prawns. This same poor growth is also observed when the protein component is made up of hydrolysates of casein, gelatin, or other proteins. Supplementation with methionine, cystine, and lysine to diets containing soybean meal does not improve growth in channel catfish.
Enrichment of protein with supplemental crystalline amino acid(s) may not be effective for growth improvement of carp, catfish, and some species of prawn. However, one species of shrimp shows significant improvement in growth when the soybean meal pprotein is supplemented with synthetic methionine.
The growth curves of a typical amino acid requirement determination study are shown on the next page. The graph presents the growth of sockeye salmon on a complete and on a tryptophan deficient diet. The growth of the fish in the 'recovery test' is also shown on this figure.
2.3. 9.2.3. Nutritive quality of dietary protein
Protein quality is regulated principally by amino acid composition. A ration with the highest protein quality is the one that supplies the indispensible amino acids in optimal amounts and proportions needed for fish protein synthesis.
Animal proteins, in general, have higher nutritive quality for warmwater fishes than plant protein. Replacement of one-third of the protein in all-plant protein diets with fish meal protein improves growth rate and food conversion in channel catfish. Fish meal generally satisfies the demand for indispesible amino acids to most fishe. Soybean meal, the most widely used plant protein, is deficient in sulfurcontaining amino acids and is less efficient for growth of fish than fish meal. Wheat germ protein results in a higher
9.3. táblázat - Table 9.3: Amino acid requirements of some animals
Amino Acid Eel Fingerling Carp Fry Channel
Catfish
Chinook
Salmon
Fingerling
Chick Young
Pig
Rat
Arginine 3.9 (1.7/42) 4.3 (1.65/38.5) 6.0 (2.4/4
0)
6.1
(1.1/18)
1.5
(0.2/13)
1.0 (0.2
/19)
Histidine 1.9 (0.8/42) 1.8
(0.7/40)
1.7
(0.3/18)
1.5
(0.2//13)
2.1
(0.4/19)
Isoleucine 3.6 (1.5/42) 2.6 (1.0/38.5) 2.2
(0.9/41)
4.4
(0.8/18)
4.6
(0.6//13)
3.9
(0.5/13)
Leucine 4.1 (1.7/42) 3.9 (1.5/38.5) 3.9
(1.6/41)
6.7
(1.2/18)
4.6
(0.6//13)
4.5
(0.9/19)
Lysine 4.8 (2.0/42) 5.1 5.0 6.1 4.7 5.4
78
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
(1.23/24.0) (2.0/40) (1.1/18) (0.65//13) (1.0/19)
Methionineb
Phenylalanind
Threonine
Tryptophan
Valine
4.5 (2.1/42)
3.6 (1.5/42)
1.0 (0.4/42)
3.6 (1.5/42)
3.1 (1.2/38.5) 2.3
(0.56/24.0)
4.0
(1.6/40)
4.4
(0.8/18)
3.0
(0.6//20)
3.0
(0.6/20)
5.1
(2.1/41)
7.2
(1.3//18)
3.6
(0.45/13)
5.3
(0.9/17)
2.2
(0.9/40)
3.3
(0.6/18)
3.0
(0.4//13)
3.1
(0.2/19)
0.5
(0.2/40)
1.1
(0.2//18)
0.8
(0.2/25)
1.0
(0.2/19)
3.2
(1.3/40)
4.4
(0.8/18)
3.1
(0.4//13)
3.1
(0.4/13)
3. 9.3. Requirements for essential fatty acid, EFAdeficiency
3.1. 9.3.1. Fatty acids
Lipids - are those chemical compounds which are readily dissolved in orgnic solvents such as ether, chloroform, petroleum ether, etc. No simple structural relationship among these compounds. Each of them contain hydrophobic part.Fats (in general) are those food materials which are composed mainly of lipids and have high food value to animals.
Fats, oils, tallow, waxes/High energy content - 8 - 10 kcal/g /33 - 42 kJ/g/
Occurence of lipids in the body: Tissues, cells, subcellular organelles /all/
phospholipids /PL/ 1-3 %/dry weight basic/
cholesterol /CH/ 0.3-1%
free fatty acids /FFA/. 05-0.1%
other lipids 0.1-0.5%
/brain, nervous system are rich in PL/
MEMBRANES are built up bylayer of lipids with embedded (integrated) and attached (peripheral) proteins
(mainly enzymes )
fluid mosaic model of membranes
ice-berg modell (SINGER AND NICOLSON,1972)
activity of membrane-bound enzymes
membrane fluidity, controlled by: FA - composition
exchange
CH -PL molar ratio (0.1 - 1)
Main series /families/
palmitoleic /n-7/ /16 :1/n-7// / 7-series/
79
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
oleic /n-9/ /18 :1/n-9// / 9-series/
linoleic /n-6/ /18 :2/n-6// / 6-series/
linolenic /n-3/ /18 :3/n-3// / 3-series/
3.2. 9.3.2. Essential fatty acid /EFA/ requirments, deficiencies
For fish mainly /n-3/ type fatty acids /linolenic acid family/ are required at 5-20 g/kg feed level. The deficiency symptoms are no growth, mortality, fin erosion, etc. The requirement depends on the growth temperature. EFArequirement can be estimated from the fatty acid composition (rancidity of feed should be checked). The sources of EFA can be fish oils in general, fresh /or well-preserved / plant oils having /n-3/ fatty acids. High level of unsaturated fatty acids requires antioxidants to avoid poor growth and low feed efficiency. Tocopherols
/vitamin-E/ should be supplied with the diet.
Fish fats in human nutrition are also important, because
• fish fats have usually low melting point and are easily digested / and oxidized/
• extracted fats cannot be used / bed smell/ - hydrogenetion
• low cholesterol content;high level of polyenoic acid / e.g. eicosapentaenoic acid, docosahexaenoic acid/:less danger of atherosclerosis and ischemic heart diseases/prevention of the cardiac infarction - Eskimos in
Greenland - in Denmark/
• high vitamin contents/E,A, D-vitamins/
• delicious taste and color in some fishes, high digestibility and food value
4. 9.4. Carbohydrate requirement
4.1. 9.4.1 Energy production from carbohydrates
Food glucose is produced from glycogen glucose - 6 – p.hosphate; glycerol - aldehyde – phosphate; pyruvate; acetate -- TCA /Krebs/ - cycle. Oxydation of acetate yields CO2, H2Oreduced pyridine nuclectida and ATP /38 moles per mole glucose/oxidation occurs in mitochondria requires several enzymes and cofactors
4.2. 9.4.2 Requirement of fish carbohydrates
No specific deficiency symptoms of deficiency in fish, but the excess dietary carbohydrate can be harmful in some species. The energy supply is obtained from proteins - fats – carbohydrates, so the protein to energy ratio is to be set. The natural food is deficient in energy, but the relative deficiency occurs with the excess protein. It is also important to consider the digestibility of carbohydrates by sugar - cellulose /gut bacteria/ or starch. The digestibility is improvedby cooking or by heat treatmentduring pelleting.
5. 9.5. Vitamin requirements and deficiences
Vitamin requirement studies using fish started around 1941 by Schneberger, when he demonstrated that paralysis in rainbow trout fed fresh carp offals could be cured by injection of crystalline thiamin. The fact that the enzyme thiaminase, which hydrolyzes thiamin, is widely present in fresh fish tissue, especially in herring, is nowadays common knowledge and the risk of a thiamin deficiency through feeding of fish-offals or offall-fish can easily be counteracted by adding thiamin prior to feeding.
Since then research in fish for vitamin requirements, has developed, be it that only a limited number of fish has been researched, especially salmonids. The present status of the art indicates that fish require 11 water-soluble and 4 fat-soluable vitamins.Since most vitamins of the B-complex play a specific role in the respective metabolic pathways (acetylation, (de)carboxylation, hydroxylation, see Table I), others in maintaining membrane functions (vitamin A), in the synthesis of blood clotting proteins (vitamin K) or in maintaining stable
80
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds metabolites in the cell as an intracellular anti-oxidant (vitamin E). Typical avitaminosis symptoms are many and of varying character, such as paralysis, scoliosis, anaemia, cataract, hemorrhage or poor growth.
With respect to te vitamin requirements as given in Table 9.4, it must be noted that, especially in the case of water-soluble vitamins, these requirements must be merely considered as recommended dietary levels (as fed basis), rather than as requirements in strict sense. Because of the possible demage of vitamins during the feed manufacturing and because of the high surface/weight ratio of pelleted fish feed, there are some losses after the preparation of the mixture of the feed component till the ingestion by the fish.
It should be mentioned that hypervitaminosis syndromes are rare. Negative effects have been reported only in the case of fat-soluble vitamins (reduced growth, liver enlargement, fin erosion, skeleton deformation, color darkening). Table 9.4. gives an overview on both the qualitative and the quantitative requirements.Typical avitaminosis syndromes have been listed for different fish species in Table 9.5.
9.4. táblázat - Table 9.4:Vitamin requirements for growth
Vitamin (mg/kg dry diet) Rainbow trout Brook trout Atlantic salmon
Carp Channel catfish
Thiamine
Riboflavin
Pyridoxine
Pantothenate
Niacin
Folacin
Cyanocobalamin myo-Inositol
Choline
Biotin
Ascorbate
Vitamin A
Vitamin E2
Vitamim K
10-12
20-30
10-15
40-50
120-150
6-10 x
200-300 x
1-1.5
100-150
2000-2500
I.U.
x x x x x x
1-1.5
x x
10-12
20-30
10-15
40-50
120-150
6-10 x
-
-
x x x
-
10-15
5-10
10-15 x x
5-10 x
2-3
7-10
5-10
-
-
30-40
30-50
200-300
500-600
1-15
30-50
100-2000 I.U.
x x x x
30-50
1-3 x x x x
25-30 x
80-100 x x x
6. 9.6. Requirements for minerals, mineral deficiencies
Minerals play an important role in living organisms. They are constituents of teeth, scales and bones. As ions they may maintain acid-base equilibria as well as the osmotic equilibrium with the aquatic environment: They are involved in stimulus transmitting functions in the nerves. They play important functions in a variety of metabolic processes. The minerals important to fish are Ca, P, Na, K, Fe, Co, I, Cl, SO4etc. can be obtained
81
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds from food and water. Their function are: bone formation, osmoregulation. Micro-mineral deficiencies cause goiter /sodine/ and anemia /cobalt/.
Since sea water is also rich in calcium the dietary requirements for calcium of marine fish is lower than that of freshwater fish. Calcium and phosphorus requirements are usually considered together because they mostly occur in the body in combination (99% of the calcium and 80% of the phosphorus are present in the fish's bones, teeth, scales!). In view of their environment marine fish require a dietary calcium/phosphorus ratio much lower than one, while in freshwater fish this ratio is close to one.
9.5. táblázat - Table 9.5:Vitamin deficiency symptoms in fish
VITAMIN DEFICIENCY SYMPTOMES thiamine riboflavin niacin pantothemic acid pyridoxine cobalamin folic acid biotin convulsions, neuritis, poor appetite cataracts, anemia, dark coloration,photophobia, poor appetite swollen gills, anemia, gill exudate, poor coordination. flexing of opercles clubbed gills, anemia, gill exudate, sluggish behavior, prostration anemia, hyperirritability, erratic swimming anemia, rfagmented and immature erythrocytes anemia, fragility of cadual fin, lathergy,pale gills, dark cloration anorexia, pale gills, high glycogen in liver,colonic lesions ascorbic acid inosital choline
Vitamin A spinal deformities, anemia lethargy, prostration,eye lisions anorexia, poor feed efficiency, skin lesions hemorrhages, fatty livers, colonic lesions,poor feed efficiency cataracts, photophobia, anemia, dim vision
Vitamin D
Vitamin K lethargy, increased lipid content of liver, muscle hemorrhages, pale gills, increased prothrombin time
Vitamin E anemia, exudative diathesis, dermaldepigmentation
.
Also magnesium is interrelated with the calcium and phosphorus requirements since some 60% of the total magnesium is presoent in the skeleton.The role ot trace elements is not (yet) clearly defined in fish in contrast to terrestrial animals. This is not surprising because fish as an aquatic animal may be the "most adequately adapted animal" to meet its mineral requirements. However with recent intensification of culture practices, more and more nutritional requirements are to be met solely by (artificial) feed input, which necessitates research in this field. The metabolic role of some minerals is summarized in Table 9.6.and Table 9.7. summarise the mineral deficiecy syndromes for some fishes.
In this context a remark must be made on another "element", e.g. the water (be it that this is hardly present in traces in the aquatic environment). Still, a water deficiency (desiccation) is known in cases where fishes are transferred from freshwater into sea water, which is common practice in cage culture of salmonids in the
82
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds sea.Due to "acute" desiccation, trout, for instance, may loose 11-12% of fresh body weight over 2 days after being transferred to the marine environment. The use of "moist pellets" (moisture content up to 30-40%) during the initial adaptation period is sometimes advocated under such circumstances.
9.6. táblázat - Table 9.5: Mineral deficiency symptoms in certain Finfish
Mineral
Calcium
Deficiency symptoms
Poor growth and feed efficiency, high mortality
Phosphorus
Magnesium
Skeletal abnormalities, poor growth feed efficiency and bone mineralization
Iron
Copper
Manganese
Iodine
Zinc
Selenium
Renal calcinosis, loss of appetite, poor growth high mortality, skeletal abnormalities, sluggishness
Hypochromic microcytic anemia
Poor growth
Poor growth, short and compact body, abnormal tail growth
Thyroid gyperplasia
Cataract, caudal fin and skin erosion, growth depression
Muscular dystrophy, exudative diathesis
7. 9.7. Basics of feeding
For nutrient requirements required for feed formulation some basic idea can be obtained from chemical analyses of the natural food of wild fish, or from the chemical composition of empirical fish feeds proved to be efficient for rearing. Other data can be calculated when complementary feeds and natural food is accounted.
An example of feed development can be taken from the history of salmonid culture:
slaughter house by-products
semimoist pellets
dry pellets or from carp culture:
cereals
(pellets)
(semimoist pellets)
For other species, such as catfish, eel, Tilapia, sea bream, the practice started similarly, but differences were also visible.
When feeding of a new species is started, usually deficiencies of nutrients occurs and low growth and mortality occur among the fish. In such cases, diet quality can be improved by using mixed diets (mixed feeds), by using special feed additives, such as,
83
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
supplements (vitamin, mineral mixtures)
concentrates
preservatives
flavours
More complex approach is required, however, for rational feed design. Step by step collection of required scientific data is needed along with gradual development of manufacturing techniques and feeding practice, too.
The Figure9.1 outlines the main elements of this complex activity.
The final goal of the feed formulation is to match the nutrient levels in the feed mixture with the requirements of the given fish for these nutrients. The simple approach, as mentioned before, could be the evaluation of an empirical formula, then, when chemical data are computed, a mixture of different available materials, giving the same chemical composition, can be prepared. Preliminary knowledge on the chemical composition and the applicability of commonly available or used feed ingredients is very much helpful in this. Other approach is the matching simply the protein content of the final feed, when the protein requirement is known from practice, or from laboratory experiments.
When the nutrient requirement data are known from laboratory experiments, and the chemical composition of the feedstuffs is also known, fish feeds can be formulated by computer calculation using the so called linear programming. On the following few pages, these methods will be introduced.
NUTRITIONAL RESEARCH
9.1. ábra - Figure 9.1: Structure of nutritional research
8. 9.8. Evaluation of empirical formulas
Knowledge on feeding habit helps to generate empirical formulas. Grouping of fishes by nutritional habit: by way of preying: by food quality:
- Lentic fish (most of
Cyprinids)
- Carnivors -Fish Eaters
84
Created by XMLmind XSL-FO Converter .
9. Fish nutrition and feeds
- Predators
Percidae (Pike)
-
Mollusics
-Crustacea,
Salmonidae
(Trout)
- Omnyvores - Small Animals
Scombridae
(Tuna)
- Suspended
Plant Particles
- Herbivorous fishes -
Macrophyta
Phytoplankton
-
Epiphyton
-
Empirical formulas can be designed by approching chemical composition of the feed to the chemical composition of natural food.
9.7. táblázat - Table 9.6: Evaluation of a typical formula
component fish meal meat meal percentage
20
10 wheat meal corn
40
20 yeast 5 bone meal 5
The following the aspects can be used in the evaluation:
Feeding experiments for 10-fold weight increase had not given deleterious effects in fish when using such ingredients. The compositionof feddstuffs are to be set by nutrient requirements, limitingnutrients and first limiting nutrient. The components (Protein, fat, ash, fibre, NFE) can be measured by Wendee analyses. Another grouping of feedstuffs is by frotein / energy ratio, energy requirement (GE, ME, NEg) and fiber tolerance.
85
Created by XMLmind XSL-FO Converter .
10. fejezet - 10. Fish feeding in aquaculture
A prerequisite of intensified pond fish culture is an up to date feeding technology. Today, in many countries
(USA, Japan, Germany) fish are successfully kept among industrial conditions, breeding and nutrition do not cause a problem. In such technology, fish do not get natural feed, but the whole feeding is based on concentrates. These technologies will widespread in the near future because of the predictability and safety issues and environmental sustainability.
There are two areas in feeding: one is the production of feedstuffs (live food) and the other is the aquaulture basedcompletely on formulated feed.
1. 10.1. Enhancement of natural food production
10.1. ábra - Figure 10.1: Fertilisation method
The unique significance of our pond fish culture precisely is that the valuable, protein rich flesh is produced from the natural feed organisms of the pond. If - like in the case of warm-blooded domestic animals- the protein needs of the animals was to be based on the protein rich feed basis, aquaculture would become a deficient industry.
Organic fertilizers decompose and release nitrogen, phosphorous and potassium which areused by phytoplankton for growth and reproduction. In this way more natural food organismsare produced for fish to eat.Especially animal manures, provide nutrients and attachment sites forbacteria and other microscopic organisms. Many "green manures" and the undigested food in animal manures are digestible andprovide direct nutrition when eaten by fish. This is in addition to their effect as fertilizers andattachment sites for fish food organisms as described above. The result is enhanced fishproduction.
This is done via fertilisation of the ponds. Fertilisation promotes algal growth, but High P levels – especially with low NO3 or NH4 - result in excessive growth of blue-green algae (Cyanobacteria). The application of manure recommended for moderate climate: 1-5 t/ha/year org.manure (according to stocking density and water quality parameters), or10-20 kg/ha/year Pand 40-80 kg/ha/year N art. fertilizer (distributed during the season)
86
Created by XMLmind XSL-FO Converter .
10. Fish feeding in aquaculture
A traditional way is the manual portioning. The prepared feed is transported on boat on the pond and shovelled out besides the feeding poles. The number of poles depends on the size of the pond and the stocking density. On smaller ponds on every 1-2 ha, on bigger ones on every 3-4ha there is one feeding place. Fish are fed once a day
(in one portion) in the morning hours. The consumption is checked after 4-6 hours. If there is significant feed left at the feeding place, the next day the portion should be reduced, but if all consumed the portion should be increased.
10.2. ábra - Figure 10.2: Zooplankton taxons: Copepods and Cladocerans
According to the rule of thumb 100 kg fish require approximately 4000 kg plant. This is calculated by 100kg fish harvested removes16,8 kg carbon, 5,4 kg nitrogen, 0,3 kg phosphorus, and 1kg carp needs ->7-10 kg zooplankton -> 1 kg zooplankton needs ->6-7 kg phytoplankton.
The main differences in farmyard manure and artificial fertilisers are:
Farmyard manure (organic)
• Complex effect
•
Fast, full load
• High water content
• Expensive transport
• Env. friendly
•
Double effect
Fertilisation (artificial)
•
•
One-sided
Single nutrient
• Overdosing
• Env. Load significant
• Complementing necessary (organig)
•
Small nutrient loads possible
• Known nutrient contant
Plankton selection is the process when we alter the zooplankton species composition in a pond to favour
Rotifers. Insecticides are used to kill crayfish and leave Rotifers intact, however it is not suggested because of the significant environmental impact. For this reason one can use timed fill-up instead. Some insects can be controlled by sunflower-seed oil (15 l /ha).
10.1. táblázat - Table 10.1: Made-up of some manure
87
Created by XMLmind XSL-FO Converter .
10. Fish feeding in aquaculture
Type
Swine (liquid)
Dry matter %
17
Nitrogen %
0,9
P2O5 %
0,7
Cattle (straw)
Manure leakage
Duck
25
5
20
1,3
2,1
1,9
1,0
1,8
1,4
As it regards quantity and qualiy, fry needs 3-5 ml Rotifers per100 liter pond water, and fingerling stocking require 10-20 ml planktonper 100 liter pond water, wowever at the latter case one should consider species composition, and their age (young, egg-carrying or aqult).
10.3. ábra - Figure 10.3: Zooplankton and zoobenthos
2. 10.2. Feeding / complementary feeding
The main aim of fish feeding is to secure high protein feed from the biological production of ponds and besides, feed fish with feed containing cheap starch. The needs of the youngest age group and the breeding stock can not be satisfied this way, so they should be fed also with high protein value feed. Most of the fish feed made of plants. These are the following: cereals, leguminous plants, extracted and ground oil seeds, bran, industrial byproducts and green plants. The seed of cereals are the most commonly used (80-90 %).
The amount of animal origin feed used in pond culture is relatively small (meat, fish meal and crackling), but lately in fry rearing manufactured mixed- feed are fed. The value of feeds is analysed by the starch and protein content. Data in the feeding tables for the nutrition of warm-blooded animals are used. On the other hand the digestion of fishes is somehow different of the warm-blooded animals, so these data should be used only for rough calculations.
Factors affecting feeding:
1. Physiological factors
• Fish apetite, and food/feed uptake ability
2. Economic factors
• Utilisation of natural growth of foodstuffs
88
Created by XMLmind XSL-FO Converter .
10. Fish feeding in aquaculture
• Nutrient requirement for self-sustaining
• Effect of sunshine,
• Natural food production in the ponds (food biomass)
• Conditions for the use of feeds – incl. Losses
• Price of fish vs. price of feed
Many spoiled, mouldy or in other ways damaged -in other words defected- feed used in fish nutrition. This is because, generally people think that fishes less susceptible for the quality of feed than other domesticated animals and it can utilise these damaged feeds also. Although there is some truth in this statement, the reality is not this.
The nutritional value of defected feeds is low and it is obvious that high production can not be expected by the use of these materials. Spoiled feeds may also damage the health of fishes. Low value feed should be fed only in low volumes and only with fish older than one year. The real nutritional values can be measured in laboratory and these data can be used to count the conversion rates.
10.2. táblázat - Table 10.2: Fish growth: genetic vs. optimum
Specie
Carp
Carp
Age
Y1.
Y2.
Genetic
0,25-0,75
1-2
Optimum
0,03-0,05
0,25-0,35
Carp Y3.
2-3,5 1,2-1,8
Previously, feed conversion was counted with the help of an efficiency factor, which was calculated on the basis of practical observations. This efficiency factor shows the volume of a specific feed that should be fed to the fish to gain one kg weight. The standard deviation of these data is so high that the use of them causes false results.
The different feeds should be prepared to meet the requirements of the different species and age groups of fishes. The following methods are used:
• grinding
• wetting
• mixing (flavouring, supplementing)
• granulation
Feeding is also to complement protein requirement of fish that can not be satisfied from zooplankton. This need usually occur at summertime, because of relaive higher feed intake of fish, and the FCR of live food (plankton).
Need for protein complementation shoud consider daily feed quantity, zooplankton quantity, water depth, number of fish and protein concentration in plankton and feed. When compiling the feeding plan we must calculate with the following issues:
• Length of growing season
• Feeding days
• Water temperature & fish feed intake
• Quantity of natural food
• Feed quality (nutrient compounds)
89
Created by XMLmind XSL-FO Converter .
10. Fish feeding in aquaculture
• Fish age (size)
• Daily ration
The carp can grind grains with its pharingeal teeth, but it prefers ground feed. It is easier to eat the ground feed and the intake is faster. In some cases the utilisation of ground meal is worse than whole grains, because the digestive tract can burst to the seams and digestive fluids can not reach the feed. This way the digestion and absorption will not be proper. When feeding ground meal the leeching of nutritive agents is significant (2025 percent). Grindig the feed is only favourable in case of fries and fish stocked for finishing.
The most common preparation procedure is wetting. Wetted feed sediments on the bottom, easier to chew and digest and there is little loss by leeching. Pre-soaking is done in feeding boat or in wetting basin near the pond.
Mixing the feed is needed for setting the right protein concentration or adding flavouring agents, minerals, vitamins, and medication. Hajba and Mitterstiller created a preparation method, which allows to soak any kind of effective agent with hulled gram (for example, treating feed with medicines). Granulating increases the conversion of feed and minimises leeching. It is important to properly portion feeds for better conversion efficiency. Feeding started in spring, when fish starts eat the feed and along with the rise of temperature quantities are increased. In autumn, feeding is finished, when the harvesting started or the feed consumption decreases significantly.
10.4. ábra - Figure 10.4: Interactions of water temperature, fish growth, enrgy need and zooplankton production
90
Created by XMLmind XSL-FO Converter .
10. Fish feeding in aquaculture
It should be taken into account that the appetite of fish and the feed conversion is in close relation with the change of water temperature. Therefore feeding can not be done mechanically, but fish physiological, environmental and efficiency factors have to be taken into account.
The data on feed use (Table 10.2.) are calculated on the basis of practical experiences.
The farmer may depart from these average numbers, if it is reasoned by environmental, stocking, medical or efficiency factors. The values of relative conversion efficiency are the most favourable in spring and later it decreases. Nowadays the technology of feeding rapidly develops.
There are two types of mechanised feeding technology are widespread. The first uses feeding automata, the other uses complex feeding system. The self-feeders are used in practice, a big advantage of it is that after presoaking it continuously serves the feed for fishes. Increases feed conversion and results in significant labour savings. One self-feeder is used on a 4-5 ha area. The use of it is especially efficient on small ponds.
The complex feeding system contains elements from the primary storing bins feed is let into special tank wagons. The wagons transport it to the pond and pneumatically fill up the secondary silos built at the embankment of the pond. From here the feed gets into self- dumping boats with the help of gravity. The boats can be emptied by an adjusting mechanism at the feeding poles. With the use of this system feeding costs can be reduced to the half, heavy human labour can be substituted and one less labourer needed per 100-150 hectares.
10.3. táblázat - Table 10.3: Comparison of feeding methods
1-Hand feeding: 2-Automatic feeding: 3-Demand feeders:
Fish can obtain food on demand by depressing a trigger.
Advantages: Advantages: Advantages:
Operator can note feeding behavior
Þguage the feed required
Reducing labour cost
Operator can ensure that feed is dispersed over wide area.
Fish can obtain much food as require
Known quantity of feed dispersed to fish
91
Created by XMLmind XSL-FO Converter .
Disadvantages:
High labour cost
Disadvantages:
Less observation of the fish
Increased handling of the feed.
10. Fish feeding in aquaculture
Disadvantages:
Trigger happy -> feed wastage & water pollution
92
Created by XMLmind XSL-FO Converter .
11. fejezet - 11. Pond management
Pond based extensive fish culture is widely applied in Central-Eastern Europe. The basic features of this technology are the use of relatively large (20-200 hectares) and shallow (1.4-1.5 m) ponds with low stocking densities (250-300 kg/ha) and supplementary grain-based feeding (wheat, corn, triticale). Natural foodstuffs
(e.g. plankton) are of special importance in these systems, accounting for around 50% of the total yield. The production of these natural foodstuffs are enhanced by the administration of farmyard manure originating form various animal production farms. The production of table-size fish (mainly common carp, silver- and bighead carps and European catfish) generally takes 3 years. The average gross yield is 0.7-1.2 tons/hectare (equal to
0.04-0.07 kg/m3) if it is calculated with 1.8 m of water column (depth) taking also into account evaporation and seepage losses. The other major feature of the traditional fish pond systems is that the harvesting is done with the total drainage of the ponds and then the ponds should be filled up again for the next production cycle.
1. 11.1. Key management issues of pond culture
Fish form an especially important group in the aquatic ecosystem. As organisms being in the top of the material flows, fish have an important role in the determination of the characteristics of the aquatic environment. This means the features of a water body – geography, hydrology, physical-chemical and biological – are on one hand determine the structure of fish populations, and, on the other hand fish are able to influence the parameters of their environment, so as the result of this different material flow paths may develop due to their activities.
Consequently fish can influence the features of their habitat. This fact provide ecological basis for inland fisheries as well as pond aquaculture, and it also provides the opportunity for the production of cheap and healthy protein that has an increasing importance for human nutrition taking into consideration also the sustainability of environmental resources.
1.1. 11.1.1. Factors that influence water quality
There are many factors that influence water quality in aquaculture. The oxygen content parallel to the food producttion are driven by photosynthesis and respiration. This process is happening along the following equation:
Photosythesys: 6CO
2
+ 6H
2
Respiration: C
6
H
12
O
6
+ 6O
2
6
H
12
O
6
+ 6O
2
2
+ 6H
2
O + heat energy
Other factors deteremining the production are water temperature, fertilisation, feeding and water exchange.
These are detailed below and in Chapter 7.
1.2. 11.1.2. Classification of aquaculture systems
Aquacutlre systms can be classified by salinity. Fresh water has a low salinity (i.e. streams, rivers, ponds and lakes), salt water has a high salinity (ocean waters), and brackish water has a salinity between fresh water and salt water (estuaries). In order to provide the optimum environment, one should test regularly the water quality.
Daily or weekly tests are made up of basic tests which are relatively quick and inexpensive (i.e. temperature,
DO, Cl, etc.). Semi-annual or annual tests are extensive and more precise but expensive and time consuming
(i.e. heavy metals).
11.1. táblázat - Table 11.1:Basic daily or weekly tests in aquaculture
• Temperature
• Dissolved oxygen
• Nitrogen compounds
• Ammonia (NH3)
• Alkalinity
• Carbon Dioxide
• Hardness
• Hydrogen sulfide
93
Created by XMLmind XSL-FO Converter .
11. Pond management
• Nitrite (NO2-)
• Nitrate (NO3-)
• pH
• Total suspended solids
• Chlorine
1.3. 11.1.3. Pond Water Quality for Fish
The temperature is one of the most impartant factors for fish production. All fish have temperature preferences and lethal thresholds, but the optimum range is difficult to control to match fish to temperature regime. It is also used to determine fish spawning times. Dissolved oxygen (DO) is the other influencing factors, and very closely related to water temperature. The normal concentration is 10-15 mg/L, warmwater fish like D.O. > 3 mg/L and coldwater fish like D.O. > 5 mg/L. The oxygen depletion is caused by decay of organic matter, this is the most common cause of fish kills in ponds pHcan be kept in the safe range with occasional chemical additions for warmwater fish (pH 6 to 9) and coldwater species (pH 5 to 9). Low pH may cause stunted growth of fish.
Herbicides are the most common risk factor. Aquatic herbicides can be toxic to fish (especially young fish) due to herbicide runoff. Some very toxic to fishespecially high following first rain after application.
Among physical issues are pond leaks that can be avoided with proper design and construction. The sealing products can be Bentonite disc into soil 3 or 4 inches, because it swells when wet. It is better for coarse textured soils. Sodium polyphosphate is white granular form, mix to 8” then compact, it breaks soil into fine particles.
The third mean is the blanket of clay 6 inches in depth and compact, but this case the pond should be refilled quickly.
1.4. 11.1.4. Aquatic Plant and Algae Control
Physical/Mechanical Control means cutting, raking, mowing, digging, pulling. This is the most effective for small quantities near shore and usually need to repeat several times per year. The plants and algae needed to be harvest if possible by mechanical harvesters for larger lakes. Biological control can be made with triploid grass carp (white amur), which prefer submerged aquatic plants (pondweeds, naiads, elodea, coontail, muskgrass) but it has little control of algae and other plants. Chemical control are done with copper compounds that are very effective at 0.25 to 0.5 ppm. They disrupts cell membrane and more toxic in soft and acidic water but may kill sensitive fish (trout, catfish, carp).
1.5. 11.1.5. Pond Maintenance
It is alvays better to conduct a routine inspection of the pond instead of repairing the accidental engineering problems. The tasks are: checking dam structure to ensure complete grass cover, fix any signs of erosion, cut grass and keep weeds, brush, and trees from growing on the dam and check for signs of minor leaks before they get really problematic. It is also necessary to remove floating debris, check overflow inlet and outlet for debris, check for and repair erosion on spillway, inspect and repair any fences around pond and maintain roads for vehicle access (fire).
11.1. ábra - Figure 11.1: Heterogenity of pond water
94
Created by XMLmind XSL-FO Converter .
11. Pond management
2. 11.2. Pond culture management
2.1. 11.2.1. Calculation of stocking rates of fishponds
Stocking means calculating the amount and determining the species and age of fish that will be put in the pond.
One needs to know the following determinations for planning the stock.
1.
Monoculture: If one places the same age and species of fish in a single pond.
2.
Poly culture: If in a pond there are different age groups of the same species.
3.
Combined stock: If several age groups of different species are living in one fishpond.
4.
Whole yield: The whole amount of fish-catch on a pond, (amount transferred m the pond + whole production)
5.
Net yield: whole yield minus the amount stocked in the pond (i.e. the net fish growth)
6.
Feeding yield: The part of whole production that is due to feeding,
7.
Natural yield: The part of whole production that is due to natural feed, (calculation: whole production - feeding production). Natural production can only be calculated. Accurate data can be obtained only, if the stocking rate is in accordance with natural feed, proper quality and quantity of feed given, the fish stock is healthy and has good genetic background.
For calculating stocking rate one need to know the nutrition physiology and usually the ecological requirements of the cultivated fish species and on the other hand, how the pond can fulfil these needs. When selecting species and calculating composition number of each species the main guiding principle should be the following. Besides maximally exploiting the condition s in the pond, one has to reach the highest yield and decrease per-unit costs.
Under favourable conditions 40-50 percent of the whole yield originates from natural feed. During the planning phase besides the aforesaid the technician has to consider market situation and economic factors and future production plans. The planned average fishing weight of the different species can be regulated by population density and with the percentage of species in the whole population. If one need lesser average fishing weight, then he should increase density, in contrary situation should decrease it.
11.2. táblázat - Table 11.1:Guiding numbers for stocking rate per hectare
95
Created by XMLmind XSL-FO Converter .
11. Pond management
Species
Carp
Silver carp
Big head carp
Grass carp
Tench
Pike perch
European catfish
Pike
Eel
Black perch
-
-
Fingerling Yearling
(1st phase, prenursing)
(2nd phase, grow-out)
Fingerling
(one stage,
Outgrowing Market size no nursing) pre-
2-3 million 100-200 thousand 30-100 thousand
2000-5000 500-1000
2-3 million 100-200 thousand 30-100 thousand
2000-4000 500-1000
2-3 million 100-200 thousand 30-100 thousand
1000-3000 400-800
2-3 million 100-200 thousand 1000-3000 400-800
-
-
30-100 thousand
-
100-200 thousand
200-300
50-100
100-150
20-50
100-200 thousand
50-100 20-50
100-200 thousand
50-100 20-50
100-200 thousand
50-100 20-50
100-200 thousand
50-100 20-50
The production of fish for human consumption today mostly still happens m 3-year setup. For this 0,02-0,03 kg weight yearling with high population density and in the second year 0,2-0,4 kg weight two-year-old also with high density is produced. By the end of the third year expected average fishing weight is about 1,7-1,8 kg per fish. On the other hand, in 2-year setup, by the end of the first breeding season 0,1-0,15 kg, by the end of the second year 1,2-1,5 kg weight has to be reached by the lines suitable for this type of production setup. This result can only be reached only with relatively scarce population even by firms with the best production conditions.
The above show, that there is not a general purpose data for filling up fishponds. Only the interval of population numbers can be established for different species and the local circumstances and the aim of breeding can specify the exact numbers. In the table the stocking rate is presented on carp and herbivore fish in case of combined population (except from young progeny). In case of outgrowing and fish for consumption, if herbivores not stocked in the pond, the number of carp population has to be doubled.
The stocking rate of carnivorous fish depends on the number of wild fish getting in the pond from outside.
Although one also has to consider that how the pond in which one intend to stock can fulfil for the requirements of carnivorous fishes (including oxygen, fishing possibilities, etc.). Fish size and age should be adjusted not to cause damage in useful fish population.
2.2. 11.2.2. Transporting fish to ponds
96
Created by XMLmind XSL-FO Converter .
11. Pond management
The farmer has to secure living conditions that enhances the potential in growth rate in young age and helps the survival of fishes. Preparing ponds includes the checking of banks and structures, repairing flaws and filling up ponds with water. Transferring may began when reaching the 60-70 percent of the planned water level. In case of transferring egg, fry or fingerling he time of the placing out depends on the spawning season of the species.
Yearlings and two-year-old fishes transferred in autumn or spring.
The autumn transfer is more favourable in respect of breeding, animal health and business organisation. (More fish survive in winter, weight loss, and need for transportation and wintering pond capacity is smaller.) But proper technical and farming conditions of the pond are proviso for this. If banks are weak, the bottom of the lake silted and infected by pathogens, than after leaving the pond dry for the winter the spring transfer is better.
When transferring yearlings and two-year-old fishes it is important to calculate the total amount, total weight and mean weight. The place of transfer should be sheltered from the wind, clean of water plants, and accessible for transport vehicles. Fish should be transferred into the pond with close-meshed net or should be slipped into the water on a plastic tray. A general rule, that the temperature of the transport and pond water should be the same. If there is a difference it should be equalised gradually.
After stocking behaviour of fishes should be monitored. If the transport was carried out properly, the fishes swim away after a short time. If not, many fishes stay at the place of transfer suffering from hypoxia and much of them may die. Dead fish, from the whole area of the pond, should be collected and counted. The number of dead fishes helps to estimate losses.
2.3. 11.2.3. Harvesting
Test harvest
The growth, feed conversion and health of fishes are checked with the help of test harvest. This important operation should be carried out once in a fortnight over the whole season, although in practice only one is carried out monthly.
The fishing method depends on the age and species of the fish. Fries caught with dripping-net, fmgerlings with drag-net and when fishes are older than one year a casting net is used. When from a combined stock only few herbivorous fish can be caught with casting net, use a drag-net for sampling.
11.3. táblázat - Table 11.2:Size of net-mesh related to the size of fish
Age or size
Fry
Fingerling
Fingerling bigger than 10g
Mesh size
0.2-0.3 mm
2-3 mm
5-10 mm
Two and three year old fish 20-30 mm
The success of test harvest greatly depends on the intensity of feed intake. A stock fed at the same place has good appetite and when feeding begins they hurry to that place in great numbers. Where, with proper gear, they soon can be caught in the adequate number. One needs 500-1000 pieces from fries and fingerlings, 100-300 from two and three year old for reliable average results. If possible catch fish from several points of the pond, because the growth of fish is differs with the place.
Besides measuring average weight, the health and condition of fishes can be evaluated. During the following test harvests the next parameters should be evaluated:
• growth rate
• feed conversion
97
Created by XMLmind XSL-FO Converter .
11. Pond management
• full quantity estimate
• health state
The results and experiences make it possible for the experts to evaluate the previous production period and to take efforts to secure high production until the next test harvest. (For example, determine the intensity of feeding on the basis of food conversion efficiency or prepares medication if the state of the fishes health.) The last fish harvest is done in the end of September - beginning of October, when feeding stopped.
This must be carried out with great attention, because the results serve data for yield estimation. At that time all data is collected from test harvests to evaluate the whole production period and estimate the whole harvestable amount and quality. Preparations for the harvest, fish transportation, fish evaluation and the planning of wintering capacity are done on the basis of the previous results. Yield estimation of fry rearing and finishing ponds serves the planning of the next year's stocking. Accurate results can be achieved by test harvests and yield estimations, if done by experts who are monitoring the ponds and the stocks over the whole year regularly.
Main harvest
The exploitation of the full stock in the pond is called harvesting. Operations carried out during the harvest are the most difficult and labour demanding activities. Proper job requires accurate planning, labour management and expertise. When planning harvesting and when carrying it out in practice, the age, amount and species of fishes should be taken into consideration. Other factors are the type, condition and size of the ponds, the time of harvesting and degree of automation.
The task of harvesting can be usually divided as follows:
• planning
• preparations
• actual harvesting
The harvesting plan is in close relation with the stocking plan. The approximate time of harvest and the further tasks are already decided when determining stocking. In the harvesting plan the time of harvest, the order of ponds and the treatment of fishes are determined in details. Preparation of the harvest requires proper labour management. The conditions of drainage are agreed with the competent authority. The needed fishing gear and their proper maintenance should be provided on time. Means of transportation, wintering ponds are prepared and ponds -in which fish for further rearing are transferred- are filled with water. During the direct preparation ponds are drained, the needed equipment is carried to the site and harvesting crew is fielded.
The time needed for drainage is dependent upon the size of the pond, water outlet and holes of the fish barriers.
Draining huge sized ponds take even 2-3 weeks. Drainage is timed to avoid stoppage in the harvest. The fish - with the help of its swimming-bladder -can feel the decrease of water level and hides at the deepest places. In the end much of the stock is clustered in the fish collecting pool and the inner mam ditch.
For harvesting the following devices should be provided:
• Nets, poles, rods, ropes, sacks, boats, baskets, bins, scale, selecting desk, vats, pumps, scale book, transport note, transport vehicles and protective clothing for the workers.
•
The number of the harvesting crew varies between 6-24 people depending on the size of the ponds.
• Harvesting methods of different age groups and species are varied from each other.
• Harvesting fries: in case of natural spawning of carp, fries are harvested from the hatchery pond at the age of
10-15 days. Water can be drained from small ponds within a few hours.
• Fries escaping with the discharged water are collected in the catching box behind the drainage sluice, where they are placed into bins filled with water and carried to the rearing pond.
Harvesting fingerlings: in this case the method of escaping harvesting is used. The point of this method is that at the beginning the water level is decreased with upper drainage and fmgerlings are collected in front of the discharge sluice. The planks of the sluice are replaced by a close meshed net, which avoid the fishes from
98
Created by XMLmind XSL-FO Converter .
11. Pond management escaping. After this the pond is drained by only a slight lower drainage method and fmgerlings going away with water are retained with a catching box or a net. The catching gear should be big enough, so that fmgerlings can find peaceful places without fast currents. Clustered fish is picked out continuously and transferred into nets placed in water rich in oxygen. A general rule is that before transportation fingerlings should not be fed for a few hours in order to help the digestive tract to empty as much as possible.
Harvesting of yearlings, two- and three-year old fishes. In the Hungarian fish farms this task is carried out mainly at autumn and spring. The autumn harvest starts in the second half of September with cropping fish for consumption. The proper time for harvesting yearlings is the end of October. After this, until the first frosts the harvest of fish for consumption can be continued. In spring harvest starts with cropping yearlings and finishes with fish for consumption.
Before the autumn and spring harvests ponds are drained by the gradual decrease of water level. When much of the water is discharged, and most of the stock is clustered in the fish-collecting pool, the exploitation begins.
The net is released into the water from the boat and the enclosed stock is pulled to the bank. In case of proper drawn the amount of caught fish can be exploited over one day. Fishes should not be crowded extremely, because the oxygen content of the muddied water decreases and fishes hardly tolerate the treatment over the whole process. Especially when the weather is warm, oxygen should be supplemented by adding or spraying fresh water.
Species that require higher concentration of oxygen should be collected firs and placed in oxygen rich water.
This is followed by the continuous exploitation of the bulk of the stock. Fishes in the net are collected with sacks and transferred into baskets or directly onto sorting tables. Sorting fishes according to their size, species and quality requires skill and experience. Sorting should be done quickly and tenderly, in order to avoid the damage of fishes.
Sorted fishes are placed in tubs filled with water or right after weighting and counting they are taken into the tanks of transporting vehicles. There is a record kept of the caught fish, in which the number of individuals in a given species, the total weight, and the number and average weight of categories are recorded.
The harvest on ponds that were badly constructed or not maintained properly is hard. The uneven bottom and the silting of drainage ditch system causes serious problems. Fishes hidden in the pits stay in the pond and it is hard to collect them. In such cases with the help of ditches created after harvesting water and fish from the pits are led to the water collecting pool.
The summer harvest is much more difficult and costly than autumn or spring harvest. The metabolism of fishes is intensive; the need for oxygen is higher and more susceptible for handling when the water is warm. Thus, the summer harvest requires good management, plentiful water, proper skills, equipment and speed. Summer harvest can be only partial or full. In case of partial harvest the water is not drained but the stock is thinned by open water harvest. Fish are attracted with luring feed to a harder part of the bottom, where there are no water plants and roots. At that time there is no feeding in other parts of the pond.
Right before cropping, feed is scattered into the water and clustered fishes before eating too much nutrition are caught with a net and quickly harvested. Using this method we can effectively catch fish for 3-4 days, as fishes go away from the harvesting places because of the permanent disturbance.
In case of full harvest, there are two phases of the working process. The first one is similar to the method of thinning fishery. In course of this the water level is decreased gradually. In the second phase the pond is drained and fishes are cropped from the fish collecting pool.
The main factors of summer harvest can be summarized as follows:
• each operation must be carried out quickly
• in case of hot weather the early morning and the late afternoon hours are suitable for fishing
• prevent fishes from being crowded in the net.
• continuously take care of freshening and enriching the water with
• oxygen
99
Created by XMLmind XSL-FO Converter .
11. Pond management
• selection of fishes /if needed/ must be done in a fish net
• containers of the transporting machines are refilled with fresh water before each trip
It is advisable to harvest continuously in large-scale farms, where the production is in fall operation, the suitable amount of inlet water is provided and the number of ponds differing in their function makes such harvesting and stocking rotation possible, that means only the minimum lost of breeding period. Ponds that have been previously harvested in summertime are filled in with water again, and fish population taken from other ponds is stocked there quickly. Under the present price system the profitability of the summer time fishery can be maintained only m case of these conditions.
Winter harvest
Quite rare, but a special and hard operation is the harvesting of wintering ponds under the ice. This is carried out, when there are difficulties in feeding or fishes stored in wintering ponds are in poor health. In crowded wintering ponds different lands of moulds can cause huge losses. Harvesting under the ice is usually partly, does not cover the whole stock. Beside the usual harvesting gear, axes, special poles, and pole holders are used in wintertime.
The method of harvesting is the following: The ice is stroke out at two opposite comer of the pond and triangleshaped ice holes are cut in each 2-3 m along the dam. At the corner opposite to the drawing place the net is let under the ice. The upper rope of the net is led along the ice holes by the help of poles and pole holders, and then fishes are pulled to the place where the net is drawn out of the water. So the way of harvesting is almost the same as the method used in other periods of time.
The lack of labor and the need for eliminating the hard physical work press for the automation of the most difficult working processes, as well as the update of harvesting methods. The most important task is to solve the problem of fish lifting. The annual production of a pond is lifted to the selection board in 25-30 kg amounts, and this means a serious physical load as well as it cannot be called to be a productive method. In order to solve this problem there are two Hungarian makes: the HK-2 and the Zs-8 fish lifters. These machines lift the fish from the net onto the selection board or into the containers of the transporting means. By the application of these machines harvesting costs decrease with 30-50 %.
2.4. 11.2.4. Overwintering the fish
A part of commercial fish harvested in the autumn goes to the market, the other part as well as the breeding stock is left in the farm. Wintering these groups of fish is a serious task. Before harvesting the wintering plan must be created, in which the wintering place, the species and the age and amount of fish is determined.
Wintering can be carried out in productive and wintering ponds.
Much of the one- or two-year old breeding fish is placed to its final place, the productive ponds right after harvesting. Until the winter begins they find there enough natural feeding stuffs, then they hibernate and start feeding in early of spring. In some cases they do not lose weight during the winter but they even grow in weight.
Although. Wintering can be successful only in such productive ponds, which are technologically excellent, can be covered with water continuously, and can provide suitable and healthy environmental conditions for the fish.
Primarily commercial fish and females from the breeding stock are placed into wintering ponds. These ponds must be tided before usage. Grass and the marsh vegetation are cut, silt is taken away, the soil is smoothed, the possible deficiencies of the constructive works are repaired, ditches are cleaned and the sterilization is done.
After all of these the sluices are fitted and then, ponds are filled in with water containing only a small amount of organic matter and no contamination.
An important requirement is to enrich the water with oxygen. This is usually carried out by leading the water flowing through the inlet sluice into a concrete or plank trough, in which there is a sheave of reed and brushwood and the water running along the single reed and brushwood becomes rich in oxygen. The efficiency of the method can be increased by allowing the water at the end of the trough to fall onto a round-shaped concrete block and get into the pond in the form of droplets.
Fish come to winter is taken over by manager responsible for the wintering pond. He examines the fish, the parasite-situation and takes care of the necessary therapy. He manages the intake of the fish into the wintering pond and regularly writes the important information into the wintering diary. It is advisable to take only one
100
Created by XMLmind XSL-FO Converter .
11. Pond management species and one weight group into a given pond. Wintering ponds are signed with numbers on the sluice towers.
Fishes in the wintering pond move too much in water hotter than 8°C, which causes weight losses. In colder water the health stock easily becomes calm and hibernates in small groups on the bottom till springtime.
11.4. táblázat - Table 11.3:Data on stocking density in wintering ponds(kg/m2)
Age group Carp, Big head carp Grass carp Silver carp
Yearling
Two year old
Three year old
8-12
15-20
18-22
10-14
18-25
20-30
8-10
10-12
12-15
A continuous, slow water circulation provides the oxygen requirement of fishes. One 1/s intake water, enriched in oxygen, is counted on 1 t of fish. The temperature of inlet water must be between 1 and 4 °C. The surroundings of the sluices and the water inlet place must be defrosted m cold temperature.
The body weight of species except carnivorous fishes decreases. The rate of weight decrease is mainly dependent upon the temperature and the oxygen content of the water, the age and condition of fishes. The smallest weight loss can be realized in case of three-year old fishes being in good conditions. The weight loss per month is 2 per cent in winter and 5 per cent in spring and late autumn. Broods before taking into the wintering pond are bathed in a parasite- killing solution, and each species is placed into separated wintering ponds.
Carnivorous fishes feed in winter, too, so weed species are also taken into the wintering ponds in order to provide a suitable amount of feed for carnivorous species. Until the winter begins as well as from the time the spring begins, carp and plant-eating broods are fed on protein-rich diet. Wintering is a highly responsible task, because it affects much of the gross production. For these reason the discipline of work, the expertise, order and cleanness is of a high importance.
2.5. 11.2.5. Transporting fishes
The task of carrying the stock inside the fish farm as well as transporting commercial fishes to a long distance requires special equipment and skills. As a result of the fastening specialization of farms, the volume of transporting breeding materials has become significantly high. Transporting methods of each age group are different as well as the needed devices.
Transporting eggs: the pike and pike perch eggs are most commonly transported, but the eggs of carp, European catfish and plant-eating species can be transferred, too. Eggs are transported at an early stage of development, until they reach the 16-celled stage. After this stage, eggs become quite sensitive to shakes. Pikeperch eggs on the nests are packed in boxes right before transportation. Nests are cut into stripes and are covered with wet moss or cotton wool. The most suitable box is that of divided into cells on top of each other, because upper stripes do not press the lower ones. On top of the box, ice slices are placed to cool the box and to keep the eggs under wet conditions.
The properly packed and chilled pike perch eggs are not damaged during even a 2-3 days of transportation. The eggs of the pike can be transported up to 10-12 hours in bins filled up with 2-6°C water. 50-70 thousand eggs can be put in 10-liter water. Transporting fries and fingerlmgs: Each age group sould be transported in double plastic bags or in air tight plastic storage bins.
The bag is filled half full with water, and the spawns should be put in it. The opening of the bag is closed with a pressing shackles in such a way that the rubber pipe should stay open. The air is pushed out of the bag through the pipe and the bag is filled with oxygen. When the inner pressure makes the bag full, the bag should be closed air-tightly. In a 60 1 storage bin 100-150 fries or 5-10 thousand fingerlmgs of carp or herbivorous fish can be transported depending on the water temperature. For carnivorous fish these numbers should be divided by three, except European catfish for which the above apply.
101
Created by XMLmind XSL-FO Converter .
11. Pond management
When transporting to long distances -because of the sensitivity of plastic bag- storage bin, which can be closed air-tightly is safer. The procedure is the same as the above. For the transportation of fries 1000-2000 liter capacity tank with diffused oxygen source is also used. These -closed tightly with a lid, filled up fully with water- are used mainly for transporting on vehicles. Oxygen added at the bottom of the tank, and aeration is provided at the top of the lid, trough a small opening.
Transporting one to three year old fishes: In volumes the transportation of these age groups is the most difficult, but the methods and gears are the simplest. This derives from that the bigger and older the fish, the smaller its relative oxygen consumption, and the more it tolerates handling ( except from the brood stock).
Transportation for short distances ( in the area of the farm) is carried out with the help of tubs placed on trucks or on trailers. For longer distances an artificial oxygen source must be provided. If fish is transported on a truck, fill the tanks fully with water and provide oxygen with a continuously operating diffuser. Figure 4 contains data on the amount of fish that can be transported.
11.5. táblázat - Table 11.4: Data on transportable number of fishes with an average weight of 0.1-0.2 kg
Species Amount (kg) of fish can be transported in 100 liter water
15 20 25 5 10
°C water temperature
Carp, Tench 50
Grass carp 60
Big head carp 50
45
50
50
40
40
45
35
30
40
30
20
40
Silver carp 20
European catfish 60
Pike perch, Pike 20
20
50
20
15
45
15
10
40
10
10
40
10
102
Created by XMLmind XSL-FO Converter .
12. fejezet - 12. Intensive fish production
1. 12.1. Need for aquaculture in the World fish supply
Aquaculture - the growing of aquatic animals and plants - covers a wide range of species and methods. It is practised from the cold waters of the far north and south, where fish like salmon, Arctic char and sturgeon are grown in ponds, flowing raceways and cages in the sea, down through the latitudes to the tropics, where carp and tilapia flourish in freshwater and shrimp and sea bass are farmed along the coasts.
2. 12.2. Types of aquaculture systems
The terms intensive, semi-intensive and extensive are commonly used to define culture methods. In practice, the distinction between them is often less than clear. They are, however, generally linked to the level of inputs of feed and/or fertiliser and to the stocking density of the fish that can be supported. In intensive culture systems there is a decreased dependence on the availability of natural food and greater dependency on the use of commercial feeds. Densities of fish kept within such holding areas are limited by species tolerance, ability to grow at raised stocking densities and maintenance of environmental parameters rather than the production of a natural food supply.
12.1. ábra - Figure 12.1: Major types of aquaculture systems
By contrast, fish production in extensive systems is based on the use of organic and inorganic fertilisers.
Fertilisation of ponds promotes the growth of simple plants which form the base of the food chain in the pond.
Fish stocked in these ponds feed on phytoplankton, zooplankton, bottom-dwelling invertebrates and smaller fish. At its most effective, this type of production can be integrated with other types of crop or livestock production, using animal manure and agricultural by-products as sources to stimulate primary production.
Aquaculture systems range from very extensive, through semi-intensive and highly intensive to hyper-intensive.
When using this terminology the specific characterization of each system must be defined, as there are no clear distinctions and levels of intensification represent a continuum.
12.1. táblázat - Table 12.1:Classification of aquaculture systems
By intensity By species produced
103
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
• Water-based systems (cages and pens, inshore/offshore).
• Fish (ponds, polishing ponds, integrated pond systems).
• Land-based systems (rainfed ponds, irrigated or flow-through systems, tanks and raceways).
• Seaweeds and macrophytes (floating/suspended culture, onshore pond/tank culture).
• Recycling systems (high control enclosed systems, more open pond based recirculation).
• Molluscs (bottom, pole, rack, raft, long-line systems also culture based fisheries)
• Integratedfarming systems (e.g. livestock-fish, agriculture and fish dual use aquaculture and irrigation ponds).
• Crustaceans (pond, tank, raceway, culture based fisheries).
• Other minor invertebrates, such as echinoderms, coelenterates, seahorses, etc (tanks, ponds, culture based fisheries)
The phases of aquaculture include broodstock holding, hatchery production of seed, nursing systems, grow-out systems, and quarantining. Together, this mix of intensity, culture systems, species, farming systems and different phase of culture create an extreme diverse collection of aquaculture systems and technologies.
12.2. táblázat - Table 12.2:Comparison of different aquaculture systems
System Space/location Local environmental impact
Conservation resources of Energy use
Integrated trophic systems multiUnits are located in Reduced env. impact concentrated zones due to recylcing
Increased ecol. Potential for efficiency (multiple economy of scale reuse) may be limited
Closed continment systems
Reuire relatively Solid wastes capsheltred sites tured and used elswhere, limited risk of escapes
Potential for Increased energy alternative use of over cage farming solid watses (pumping)
Onshore sites using
RAS technology
Removes aquaculture
Eliminates from environmental sensitive locations impacts local Conserves resources water Slightly and requirements nutrients if additional processes added higher
12.3. táblázat - Table 12.3:Major production parameters of various intensity aquaculture systems
Stocking (kg/m3) FCR
(kg/kg)
Feed protein
Prod. cost content
(%) (USD
/kg)
Prod. cost Gr. revenue
(USD/m3)
(USD/m3)
1,0-2,0 (a) Bass production in
RAS
15-60 (a)
Intensive prod.
tilapia 60-120 (e) 1,7-2,0 (f)
40-55
(b)
1,9-6,9
(a)
70-160 110-150
33-64
(u)
0,55-0,65
(e)
40-70 110-180
African catfish prod. 700-1000 (h) in RAS / water
1,5-20,0 (i) 37-56
(u)
1,0-2,5
(h)
440-870 1100-1200
104
Created by XMLmind XSL-FO Converter .
12. Intensive fish production crossflow
Trout prod. in RAS / water crossflow
30-40 (j)
Sea bass cage culture 20-35 (l)
Salmon cage culture max. 20 (o)
1,0-1,2 (j)
1,2-1,4 (m)
1,0-1,2 (o)
42-64
(u)
1,2-20,0
(j)
50-65 140-160
42-64
(u)
3-5 (l) 80-140 160-180
38-48
(u)
1-2,5 (o) 25-35 80-160
Carp pond fish culture
0,15-0,2 (v) 1,3-5,4 ( w)2-3 (v) ~ 10
(u)
1,8-2,7
(v)
0,2-0,21 0,2-0,25
Források(17): (a) FAO (2011a); (b) Fish.Wa, (2011); (c) Katersky és Carter, (2007); (d) Pearson et al., (2003);
(e) FAO (2011b); (f) Asraf Mohamed et al. (2007); (g) Abdalla és McNabb (1998); (h) FAO (2011c);
(i) Isyagi, et al. (2009); (j) FAO (2011d); (k) Russo et al., (1974); (l) FAO (2011e); (m) Robles et al. (2007); (n)
Person-Le Ruyet et al. (1995); (o) FAO (2011f); (p) Hellawell, (1986); (r) Globefish (2011); (s) Seafood Source
(2011); (t) FAO (2011g); (u) Aller-Aqua (2011); (v) MAHAL (2011); (w) Coche et al. (1998); (x) Gela et al.
(2003); (y) Biswas et al. (2006); (z) Einen et al. (1999); (aa) Peruzzi et al. (2004); (ab) Samuelsen, et al. (2001);
(ac) Hoffman et al. (1993); (ad) Rutten, et al. (2004); (ae) Bársony et al. ( 2011);
3. 12.3. Diversification of pond farming
Since the fishponds require significant fixed assets and a large initial investment, the profitability of extensive fish production is a critical issue taking into account the low yield, and the low prices of extensively produces fish and also that environmental services are not fully acknowledged and damages caused by protected animals are not compensated. In order to improve profitability of extensive ponds without compromising the advantages offered by such ponds, two complementary technologies were elaborated and tested in Hungary which can be fitted well to the conventional pond aquaculture systems. These new type of systems are: the “pond water recirculation” (PwR) and the “pond-in-pond” (PiP) systems, which systems basically are combined extensiveintensive systems. These two systems can increase the productivity and profitability of the pond fish culture significantly. The intensive component of both technologies can be integrated into extensive pond systems where those are parts of the common water management system together with the fish ponds. The complex system allow the simultaneous production of various fish species, age groups at different intensity level:
• Level 1: use of multifunctionality complementary activities (e.g. angling, ecotourism, etc.)
• Level 2: technological diversification:
• “pond water recirculation” (PwR) system
• “pond-in-pond” (PiP) system
• Level 3: species diversification
• Hybrid Stripped Bass, African catfish, etc.
3.1. 12.3.1. Pond water recirculation” (PwR) system
The “pond water recirculation” (PwR) system is a unit made up of several small and one large extensive pond.
The key concept is that the feed-based production of high value species is carried out in the small ponds under intensive conditions. The effluent water of the ponds are supplied continuously to the extensive pond where the nutrient load is utilised by the natural biological processes. Then, the “purified” water is pumped back to the intensive ponds, thus closing the water recirculation. Proper ratio between intensive and extensive ponds and also proper water flow control are key issues when combining the intensive/extensive ponds. Using the excess nutrient from the intensive ponds as nutrient input to the extensive ponds, less external nutrients (e.g. organic manure) is required for extensive fish production saving cost this way.. Key elements of the small (intensive) pond technology are: high stocking density, application of complete formulated feed, permanent aeration and
105
Created by XMLmind XSL-FO Converter .
12. Intensive fish production continuous removal of wastes. Significantly higher yields and gross revenue per unit area can be reached comparing to conventional farming. Due to the controlled environment in the small ponds it is possible to reach the yield of 8-10 tons/hectare, that is about 10 times higher than that of the extensive pond.
The “pond water recirculation” (PwR) system is operating now at pilot scale in a commercial farm. It is established by connecting the intensive and extensive ponds thus creating one common water systems in which the water is circulated between the extensive and the intensive units. In this case the intensive ponds are of several sizes, totally 1.6 hectares with 1.5 m depth. The extensive pond is around 20 hectares with 1 m average water depth. The ratio of intensive and extensive pond area is 1:10, which – according to the preliminary results
– adequate for the water treatment. Water is recirculated between the ponds by high capacity and low head pumps.
3.2. 12.3.2. Pond-in-Pond (PIP) system
The basic concept behind the “pond-in-pond” (PiP) system is very similar to the PwR system being also a
“combined extensive intensive” system. The main principle is that the effluent water from the intensive unit
(floating raceways) rich in nutrientsis purified in an extensive large pond utilizing its “biological self-cleaning” capacity. The basic difference between the two systems is that in case of PwR the water bodies of the ponds separated, but the intensive units of the PiP system are actually situated in the water body of the extensive pond.
Low head pumps are used for supplying water to the raceways. The water of the extensive pond is flowing through the raceways continuously, thus the PiP system can be considered as a flow-trough system, having the main advantages of such systems namely the continuous supply of oxygen rich water and continuous removal of fish excreta. The water removed from the system is high in organic matter, which is not wasted but utilized in the extensive pond directly by the fish (unconsumed feed) and as organic fertiliser.
The experimental system is made up of 4 raceways, 30 m3 each and a high capacity low head pump with connecting pipelines. The units are equipped with elements necessary for the operation of the floating system
(grills, locks, walk paths, automatic feeders, aerators/oxygen suppliers).
12.4. táblázat - Table 12.4: Comparison of various
Common carp, table size Extensive pond PwR PiP
Stocking density (kg/m3)
Ind. stocked bodyweight (g)
Stock at harvesting (kg/m3)
Ind. harvested bodywgt (g)
Production value (EUR/m3)
Net yield (kg/m3)
Feed cost (EUR/kg)
Predation (%)
0,025
300
0,09
0,13
0,07
0,86
40
1800
0,125
300
0,96
2000
1,81
0,83
1,00
2
4,5
300
30,00
2000
56,79
25,50
0,87
2
Applied feeds w.wheat + fmy.manure
Aller Master (36/9) Aller Master (36/9)
SGR (g/day) 11,1 12,6 15,5
The advantages of these technologies are: relatively low investment required (pump for water circulation, feeders, aerators, etc.), easy operation (extra cost for pumping, labour, feed, etc.), water saving technology –
106
Created by XMLmind XSL-FO Converter .
12. Intensive fish production farm (wintering ponds, canals, extensive pond – already existing), so lower average fixed cost and no extra cost for water required. Another issue is the safer fingerling production due to low bird predation (easier prevention) and continuous sale opportunity.
Among constraints, there are only two concerns, one is disease risk due to higher stocking density and environmental impact because of the intensive use of feeds. Some more in this field are, that the establishment of a PwR and PiP needs complementary investment and the management of the complex farm (extensive and intensive parts) requires special skills.
After all, we can consider these new technologies to be excellent opportunity for the diversification, because of they contribute to the better economic stability due to diverse farm activities, and provide additional income especially in summer. It is also a water saving technology and result in a more controlled growth thus an economically more viable operation.
4. 12.4. Intensive production technologies
The development of intensive aquaculture technologies has been accelerating recently because of the cumulative effect of competition for the use of resources with other stakeholders (e.g. agriculture, industry, transportation, tourism etc.), growing input prices and increasing need for fish and other aquatic products. The tendency nowadays is towards a complex, integrated technology that is causing the less effect on the environment and, at the same time yields the highest output by sharing the resource use and the output (byproduct) of one serving as input for the other in a chain.
4.1. 12.4.1. Cage culture
12.2. ábra - Figure 12.2: Different cage culture technologies (top: conventional, middle:
“low cost”, bottom: high-tech)
107
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
Cage culture, the practice of rearing fish in cages, can be applied in existing bodies of water that cannot be drained or seined and would otherwise not be suitable for aquaculture. These include lakes, large reservoirs, farm ponds, rivers, cooling water discharge canals, estuaries and coastal embayments. Due to the relatively low investment cost and high productivity, this is the most economic way of intensive fish production, although it is onsidered to have the highest impact on the environment.
The spread of intensive floating cage fish farms along the coastal zones creates serious problems with respect to the effects of pollution. After the feeding of fish, excreta and solid sediments (uneaten food and faeces) fall into the sea and are deposited on the sea bottom, so the chemical water characteristics (oxygen, ammonia, nitrite, nitrate, BOD) are often modified under the cages. However, significant esearch has been focused on several methods to reduce the environmental impact of fish cages: rearing detritivorous fish under the cages to reduce the sediments, use of artificial barriers, planting and growing seaweeds etc. to reduce the environmental impact.
Farm escapees and invasives are also risk factors. Escapees can adversely impact local ecosystems through hybridization and loss of genetic diversity in native stocks, increase negative interactions within an ecosystem
(such as predation and competition), disease transmission and habitat changes. The accidental introduction of invasive species is also of concern. Aquaculture is one of the main vectors for invasives following accidental releases of farmed stocks into the wild.
One of the primary concerns with mariculture is the potential for disease and parasite transfer. Farmed stocks are often selectively bred to increase disease and parasite resistance, as well as improving growth rates and quality of products. As a consequence, the genetic diversity within reared stocks decreases with every generation - meaning they can potentially reduce the genetic diversity within wild populations if they escape into those wild populations
12.3. ábra - Figure 12.3: Various seeweed grown in bi-culture to mitigate negative environmental impact
4.2. 12.4.2. Water crossflow systems
These systems are the land-based version of cage culture. The first freshwater ones were constructed for rainbow trout production in Europe, and there are several still running in a profitable way. There are examples also in the tropics for fish, crayfish and other aquatic species. The systems are made up of two basic components: culture unit, and setting/sedimentation unit, the latter being responsible for limiting the environmental impact. Water enters the culture unit, flows through the setting/sedimentation unit and then moves back to the water outlet. The range of species to be cultured are limites in cold and moderate climate because of the water temperature of these systems are similar to the environment. In contrary, a wide range can be reared in the tropics. Nowadays, due to the increasing environmental concerns, these systems are turned into recirculation systems.
12.4. ábra - Figure 12.4: Operation scheme of water crossflow systems
108
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
12.5. ábra - Figure 12.5:Outdoor (left) and indoor (right) water crossflow systems
4.3. 12.4.3. Recirculation systems
A Recirculating Aquaculture System (RAS) can be defined as an aquaculture system that incorporates the treatment and reuse of water with less than 10% of total water volume replaced per day. The concept of RAS is to reuse a volume of water through continual treatment and delivery to the organisms being cultured. Water treatment components used in RAS need to accommodate the input of high amounts of feed required to sustain high rates of growth and stocking densities typically required to meet financial outcomes. Generally, RAS consist of mechanical and biological filtration components, pumps and holding tanks and may include a number of additional water treatment elements that improve water quality and provide disease control within the system.
12.6. ábra - Figure 12.6: General operation scheme of a Recirculating Aquaculture
System (RAS) (arrows indicating the direction of water-flow)
The uses of recirculation vary widely, from broodstock management, hatchery and nursery rearing, grow-out and quarantine holding. It is likely that use of recirculation systems in intensified commercial aquaculture will increase in future. There are many possible solutions, adaptable to specific local situations. These include minimum water demand, limited space demand, reduced water discharges, controlled conditions to optimise productivity, tight control of feeding to maximise feed conversion efficiency, fairly site-independent, exclusion of predators and climatic events, and necessarily little use of chemicals. But such systems often involve high capital costs, are more complex, and failures can result in serious crop loss. Such systems place greater demands on management control, feed design, health management, and demand professionalism in their use. A welldesigned recirculation system must be readily managed and competitive in terms of cost-efficiency, as such
109
Created by XMLmind XSL-FO Converter .
12. Intensive fish production current applications are principally targeted at high value intensive aquaculture. The most recent systems require a limited amount of energy tor un because the water levels are quite similar all over the culture and cleaning systems. These are called „Low Head systems”.
12.7. ábra - Figure 12.7: Low Head system
The more difficult considerations for aquaculture should relate to the RAS being able to provide for the unique biological and behavioural characteristics of the animals cultured and the operational and management processes required, whilst maintaining viable production costs. Potentially, RAS offer a number of potential advantages for aquaculture, including:
• Control of all parameters that influence growth so that the fish farmer can better manage economic and production performance,
• Production in locations where limited water is available,
•
An ability to manage waste production to provide greater environmental sustainability than traditional aquaculture systems,
• Bio-security,
• Ability to locate the operation close to markets to reduce product transport time and costs,
• Reduction in land area required when compared to pond-based systems, and
• Ability to integrate with agricultural activities (e.g. use of water effluent for hydroponics, horticulture or preuse of irrigation water).
Technology elements
The section below introduces the typical elements of an intensive fish production facility.
Tanks: Raceways appear to have great utilization of floor space. The rectangular shapes and long straight sides lend themselves to close packing with common walls. Normally they are approximately 10 times longer than they are wide. Typical dimensions are 10-20ft (3-6m) wide, 100 to 200 ft (30-60m) long, and 3 to 4 ft (0.9-
1.2m) deep. Raceways can require 1.5 to 3 times the wall area of a circular tank of similar volume. Although they can be fabricated out of fiberglass, plastic or metal, the typical construction material is reinforced concrete.
12.8. ábra - Figure 12.8: Circular tanks
110
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
12.9. ábra - Figure 12.9: Raceways
Removal of particulate matter: Solids resulting from fish waste and uneaten feed conribute a portion of the oxygen demand and toxic ammonia in the system and should be concentrated for removal. This can be accomplished in a settling basin with reduced water turbulence, or by mechanical filtration through porous material such as sponge, screen, sand or gravel.
12.10. ábra - Figure 12.10: Gravel filter
12.11. ábra - Figure 12.11: Drum filter
111
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
12.12. ábra - Figure 12.12: Function of the drum filter
12.13. ábra - Figure 12.13: Function of the Vortex filter
12.14. ábra - Figure 12.14: Function of protein skimmer
Biological filtration: Fish and other aquatic organisms release their nitrogenous wastes primarily as ammonia
(NH3) excreted across the gill membranes. Urine, solid wastes, and excess feed also have undigested nitrogen fractions, and are additional sources of ammonia. Ammonia is toxic to fish and can exert sublethal stress at concentrations of less than 0.05 mg/l ammonia nitrogen (NH3-N), resulting in poor growth and lower resistance to disease.
12.15. ábra - Figure 12.15: Cheramic filter media
112
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
12.16. ábra - Figure 12.16: Plastic filter media
12.17. ábra - Figure 12.17: Optimum bacteria film on media
Aeration: Water must be aerated to maintain adequate dissolved oxygen concentrations for fish and for proper functioning of the biological filter. Aeration is usually applied in the fish culture tank and again prior to or within the biological filter, that portion of the recirculating system where organic waste products are broken down through bacterial decomposition. Dissolved oxygen should be sustained above 60% of saturation and periodically verified.
Figure 12.18: Paddle-wheel aerator) Figure 12.19: Airstone Figure 12.20: AeroTube
Feeders: Feeders are widely used in intensive systems, because fish are need to be fed frequently. As the rule of thumb 75-80% of the dalyration is spreaded by feeders, while the remaining 20-25% is fed by hand. This wway the farmer can closely monitor the feed uptake by fish without significant over- or underfeeding.
Recirculating systems, however, can be costly to operate, as they are highly dependent on electricity or other power sources. Pumps must be used in order to maintain the constant flow of water and often water must be heated or cooled to the desired temperature. Backup systems must be in place in case of a power failure. A less
113
Created by XMLmind XSL-FO Converter .
12. Intensive fish production expensive and more environmentally friendly option would be to take advantage of alternative energy and heating sources. Solar, wind and geothermal power are being considered as is heated water obtained from the waste products of manufacturing, electricity production, and composting.
12.18. ábra - Figure 12.21: Pendulum feeder
12.19. ábra - Figure 12.22: Clockwork feeder
12.20. ábra - Figure 12.23: Automatic feeder
Fish production involving the above technological elements can be very productive, the output reaching up to
150 kg/m3/year with permanent harvest, depending on the species and age group concerned. Intensification is also meaning continuous supply of uniform fish that is now basic requirement of the consumers and the processing industry as well.
12.21. ábra - Figure 12.24: Fish production yields
114
Created by XMLmind XSL-FO Converter .
12. Intensive fish production
Annex
12.5. táblázat - SWOT analysis of intensive systems
Strengths Weaknesses Opportunities Threats
Legal and Clear regulations administrative issues
Current controls are generally in place for often based on this type aquaculture of limited factors which may not encourage best practice in all areas
Promote regulations Implementation of for improved welfare more stringent water and water treatment quality criteria could technology close some farms if they do not have the financial resources to invest in new water treatment technologies
Availability production sites of Good output to land Waste output from Technology High competition for area use Sometimes flow-through fish upgrades to existing sites and water from linked with fisheries farms likely to be farms could raise other potential users enhancement and further restricted in provision of fish for angling the future output without and constraints on development of new development in rural sites areas
Technological issues Focus of much R&D over last 10-20 years
Limited investment funding innovation for
Improved technologies address
Lack of technology to development could lead to many of these environmental issues farms breaching and efficiency robustness improve tightening and environmental regulations
Fish oil and fishmeal availability
Opportunities for Variable, but Potential close control over generally significant significant feed composition and reliance on fish meal use and oil at present reductions for Rising prices could impact on output if in production becomes fishmeal and oil use unprofitable due to per unit of high essential feed production through ingredients (if
115
Created by XMLmind XSL-FO Converter .
12. Intensive fish production diet development substitutes found) not
Environmental aspects
Technology options for reducing impacts
Discharge of nutrients, dissolved are available with and solid waste if not
Potential improved for Strict environmental water regulation without utilisation efficiency support for significant use in captured and treated with many areas on-farm output increased technology upgrade could close many farms
Food safety and Generally good Flow-though systems Development and Environmental other aspects related control to consumption environment feed especially over potentially at risk implementation of pollution and feed and from water pollution inputs, and feed improved screening technologies in contamination contamination recirculated aquaculture system
Animal health and welfare
Management and Intensive systems technology options more likely to suffer more easily major disease
Improved systems based on welfare research
Emergence of new disease problems implemented to deal outbreak Welfare with disease and welfare issues concerns higher
Third competition countries Potentially close to Limited options for and market economies of scale market issues in most current systems
Potential for Vulnerable to marketing as local competition on price production from third countries
Production costs Relatively robust Environmental limits Further development Rising feed costs and with respect to on scale economies labour costs for systems flow-though of recirculated tighter aquaculture systems environmental to reduce costs regulations
116
Created by XMLmind XSL-FO Converter .
13. fejezet - 13. Multifunctional aquaculture
The recognition of th multifunctional character of agriculture appeared in the documents of the Rio Earth
Summit in 1992 (United Nations Conference on Environment and Development, UNCED 1992). The declaration from the agricultural ministers committee in 1998 further defined the term multifunctionality as follows: ‘‘Beyond its primary function of producing food and fibre, agricultural activity can also shape the landscape, provide environmental benefits such as land conservation, the sustainable management of renewable natural resources and the preservation of biodiversity, and contribute to the socioeconomic viability of many rural areas’’ (OECD 1998). Although this concept includes the aspects of preservation policies that support farmers and rural communities from attack under international trade agreements, some trade bodies criticise the concept as an attempt to avoid or limit the objectives of fundamental reform in world trade (DeVris 2000;
Swinbank 2001). The multifunctionality debate, however, focuses on the alleged positive effects associated with agriculture.
1. 13.1. Sustainable fish farming
The term ‘sustainable development’ was first used by Brown in 1981, which became a directive since then.
There are several ways to interpret sustainable development regarding terminology and field, of which one of the most popular and expressive is:”To develop while maintaining the prevailingcircumstances of existence”. In vider context these mean the economic, social and environmental circumstances
13.1. ábra - Figure 13.1:Diversification of pond fish culture
The key elements of sustainable pond farming (pond fish culture) are:
1.
In sustainable production the economic goal harmonise with the regeneration of natural (environmental) resources and the buffering capacity of the environment under impact.
2.
It is characteristic for the sustainable sectoral production (enterprise economy) to be input-saving (materials, energy, etc.) and to operate under a management that is already environmental, focusing on quality production and being environmentally aware.
117
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
3.
The sustainable farm in economic sense is the one which is continuously liquid, incomes cover all expenses, the profit covers the needs for the farmer and the family and ensure the basic for extended re-production
4.
Pond farming is situated in rural areas, interlocking with the natural environment. It is important to sustain the population in physiological, economic and social sense without damaging the environment.
13.2. ábra - Figure 13.2: System of sustainable pond farming
Pond fish farming is a very complex activity which includes three main elements according to the followings: food production; environment protection; nature conservation and recreation. Rural areas and within this the arable lands and fish ponds are locations of production, and, at the same time, biological and social habitats. So, the agriculture, forestry, pond fish farming, environment- and nature protection are important components of the rural life. A pond fish farm, which is a part of the rural economy also functioning as valuable aquatic habitat, plays important role in regional water- and landscape management, provides services for various recreational activities and contributes to the preservation of cultural heritage. It is important to underline the fact that pond fish farming is an activity that is not wear up the resources, in contrary it enriches the environmental capital, enhances biodiversity and promote the climate protection.
2. 13.2. Bases of the multifunctional pond fish farming
Aquaculture has never been a separate issue within the concept of multifunctional agriculture, although there are some notable differences between the two sectors when multifunctionality aspects are analysed. In spite of the long tradition of pond fish production, mainly in Asia, aquaculture is a relatively young industry in food production. Aquaculture, in particular extensive pond aquaculture, is still a natural-like food production activity, which is based on the utilisation of natural resources by traditional methods and tools (like the fishing net).
Many fish ponds are the remains of once-extensive wetlands, while others were built on areas with limited potential for other agricultural activities. The elements of multifunctionality of pond fish farms are shown in
Table 1. The positive effects of fish ponds have been recognised, however these are seldom rewarded in the marketplace or by society. Better understanding of the principle of multifunctional aquaculture and the more systematic application of the various elements of multifunctionality by farmers may contribute to the better placement of pond fish farms in an agroecosystem and also to the improvement of their viability in the long term.
13.3. ábra - Figure 13.3: Functional elements of pond farming
118
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
Elements of multifunctionality of pond fish farms :
Extensive pond fish production: The majority of pond fish farms apply extensive technologies basedon the utilisation of natural food available in the pond water. Pondfish farms can supply healthy and fresh fish to local markets. Theimpact on the environment is minimal or zero and fish are reared innatural-like conditions.
Extensive fish pond production can easilybe converted into organic farming.
Maintenance of biodiversity: Fish ponds have been recognised as valuable wetlands thatcontributed to the maintenance of biodiversity in a specific region.Fish ponds support large bird populations (usually without anycompensation).
Improvement of water management: There is scientific evidence that fish ponds contribute to theimprovement of soil and air humidity, besides storing water inotherwise dry regions. Fishponds in many cases improve thequality of inflow water by processing and trapping nutrients.
Landscape management: Fish ponds with their water surface and surrounding vegetationincreases the aesthetic value of a region, which otherwise would bea less attractive rural area. Many ponds have been built on areaswhere soil quality is less or not suitable for agricultural production.
Contribution to the socioeconomic viability of rural area: Many pond fish farms operate in rural areas where employmentopportunities are limited. Fish farms offer various jobs for the ruralpopulation in a specific region, which has great importance inremote areas, where fish farms often located.
Preservation of cultural heritage : Extensive pond fish farms still apply traditional methods and gears(simple boats, nets, etc.) like hundreds of years ago. Many fishfarms uses natural materials (reeds, bullrushes etc.) for variouspurposes. Some of the farms collect old tools and equipment,which are slowly being replaced by modern ones.
Services for tourism : Services for anglers have recently been a typical side-activity ofnumerous fish farms, but natural-like fish pond systems offeropportunities for bird watching and other nature-related touristprograms.
13.4. ábra - Figure 13.4: Multifunctional Fish Farm
119
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
3. 13.3. „Aranyponty” Fish Farm as an example of multifunctional pond fish farms
This farm is situated in Europe, in Hungary, and has been re-organised to be multifunctional.
13.1. táblázat - Table 13.1: Main features
Total area:
Rented area:
1000 ha
600 ha fish 1600 tons Total annual production:
Main species:
Total staff:
Annual turnover:
Common carp (75%), Chinese carps, Carnivores, Tench and Ornamental fish
55 (full time)
2 million EUR
3.1. 13.3.1. Fish production
As fundamental function, the farm produces good quality fish for local and export markets, as well as stocking material for angling clubs. The enterprise was the first in organising the organic production in Hungary, so the first steps were taken with the help of a project with national support. This unique feature has been dove via the following steps:
• The preparation of the criteria-system for bio-fish production
• Adaptation of international qualification systems to Hungary and for carp production
• Criteria are related to:
120
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
• Conditions of fish hatching and rearing
• Transportation and storage conditions
• Stocking density
• The attributes of the pond-system
• Feeding and fertilization
•
Allowed and prohibited chemicals
• Water quality criteria and control
• Processing and sales
3.2. 13.3.2. Nature reserve and environment protection
In everyday farming the requirements (propagation, feeding, etc.) of the fauna living nearby the ponds is taken into consideration within a reasonable level (e.g. the repelling of Cormorants is necessary). There is a successful and mutual co-operation with the personnel at the nature conservation authority, who are also involved in the management of the eco-tourism.
The pond farm is a permanent bird migration path, tens of thousands of bird species arrive late Fall and rest here during the migration. Theis observation and photographing provide unparalleled experiences for the visitors.
The farm has an advantage to have thermal water well nearby the centre. The new wellness centre is based on this feature, and the option to provide Winter angling possibility in a nearby pond with the hot outlet water. This is a special appeal in Winter. The thermal water (30 °C, 400 m) is used for heating, temperate water angling as well.
The reed by the ponds is also utilised, it is sold as traditional roofing material or decoration in the local market.
Some 40-70.000 sheaf yearly is used for roof, reed-drape, other ornamental purposes.
Wind andwater energy at present it is not in operation, but the use of water and wind energy is also planned, first of all for water pumping. On the other hand a windmill might not be a desirable landscape element in the farm.
A miniature hydroelectric station and usage of windmills for water pumps, water aeration, production of electricity is planned.
3.3. 13.3.3. Services for anglers
The angling center in Örspuszta has been formed by the construction of special ponds and a recreational park, playground, camping. They provide complex service (buffet, bait shop, bathrooms, closed parking, accommodation, bicycle rental, etc.) and the angling centre of the farm provides various options for the visiting anglers. Several recreational facilities are also available for visitors, and they are organizing angling competitions too.
3.4. 13.3.4. Services for tourism
The fourth pillar is to meet the requirements of tourism, of which one part (angling) has already been detailed.
Beyond conventional tourism there is also eco-tourism, where at present the main activity is bird watching. The available infrastructure, such as wine cellar, traditional fishermen's inn, hotel and guest houses and wellness centre are all to serve the active leisure time for the guests. Main features:
• Bird watching (220 species, among them 181 are protected)
• Excursions in the area
• Fishermen’s inn and wine cellar
• Small hotel and guest houses
121
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
• Recreational facilities
• Spa with medicated hot water
• Wellness centre
Ecotourism - Photo tourism andbird watching: A special path with information boards and observation towers was made for bird watching. Besides the conventional ponds, bird feeding bonds are also in operation to attract fish feeding birds from the other ponds that are primarily for fish production. On these special ponds the birds can feed without disturbance thus it is easy to observe or photograph them. Photo tourism and bird watching services include scouting routes, information boards, watchtowers and bird feeding pond.
To show the heritage is also the part of the nature conservation and fish production, as well. To meet this a fisheries museum is established where, beyond the traditional fishing equipment and methods the aquatic flora and fauna is also presented. There is a conference centre is situated by the centre building, where meetings, trainings, workshops can be organised in natural environment. This option is significant off-season.Training, demonstration, meetings are:
• Fisheries heritage (fisheries museum)
• Conference and social events
• Training programs
• on wildlife and nature
• on fisheries and aquaculture
• on the use of natural materials (bulrush, reed etc.)
Two times each year several hundred guests are invited to the farm: the seasons opening festival and the Saint
Peter’s day festival. The guests can visit the museum, participate on the fish cooking competition.
3.5. 13.3.5.Summary and evaluation of the operation
The main advantages and benefits of multifunctional pond farming are: better economical stability due to diverse farm activities, additional incomes from various services (for tourists and anglers), access to financial support for environmental-friendly farming, opportunity for organic farming and consequently improved image of the farm.
13.5. ábra - Figure 13.5: Structure of the revenue of a conventional and multifunctional farm
122
Created by XMLmind XSL-FO Converter .
13. Multifunctional aquaculture
The main constraints and difficulties of multifunctional pond farming are: the establishment of a multifunctional farm needs supplementary/complementary investment, the management of the complex farm requires special skills, service providing is completely different from farming, the farm size should be relatively large and the farm should be located in an attractive and valuable natural area.
The future trends for multifunctional pond farming: the value of nature will further increase (Sensitive area, wetland habitats, agri-environment program), angling continues to be popular, and offers good business opportunities, organic fish market is growing, though remains limited, the environment-friendly production is entitledfor /subject to financial support, and the environmental regulations on farming will be more strict.
The main characteristics of the sustainable pond fish farming model:
1.
Competitive aquaculture, which can meet challenges of global trade without being over-subsidized
2.
Well controlled and environment-friendly food production activity, which provides nutritious, healthy and safe food
3.
Activity, which may not focus only on fish farming but may include various services for recreation, environment-, water-, and landscape management
4.
Fish production activity, of which type and intensity are always adapted to the given environmental conditions;
5.
Aquaculture, which still contains traditional elements of food production (e.g. netting) and having rich cultural traditions and heritage
6.
Food production, which is based on the utilization of renewable (energy) resources
7.
Environment conscious farming practice, which also concerns the proper working conditions and health of the employees and those living in the surrounding
The examples of fish farms clearly show the business opportunities that lie in the diversification of farm activities. The development of multifunctional fish farms should be based on careful market surveys on the demand for various products and services, however, environmental and water quality regulations should also be taken into account. There is also a need for realistic assessment of local conditions and capacities that may be improved through collaboration with research and development institutions. The role of pond fish farms in the complex agricultural ecosystem requires more study, which also emphasises the need for collaboration between pond fish farms and research institutions. The success of multifunctional pond fish farms is beneficial not only for the farms but also contributes to the improvement of the image of pond fish farming.
123
Created by XMLmind XSL-FO Converter .
14. fejezet - 14. Fish processing
Fish is a food of excellent nutritional value providing high quality of protiens, fats and a wide variety of vitamins and minerals. Its protien is easily digestable and contains more essential aminoacids and essential fatty acids than in cereals and legumes. People in developed countries are much more dependent on fish as part of their daily diet. It reveals the importance of fish as food material. In this unit an attempt has been made to make the students aware of different biochemical components in the fish muscle. In addition, this unit deals with the nutritional value and the importance of fish in human diet.
14.1. táblázat - Table 14.1:Chemical composition of fish & other flesh (indicative data)
Fish & other flesh Water
(%)
Protein
(%)
Fat/oil
(%)
Energy
(kJ)
Common carp
Catfish (lean)
78.9
80,0
Pike-perch (Zander) 78,9
Trout 76,3
16,0
17,5
19,0
19,5
4,0 (20)
0,8
0,8
2,7
418
326
351
Pork (lean)
Chicken (lean)
Beef (lean)
71,9
74,6
74,3
20,3
21,5
20,6
6,8
2,5
3,5
602
460
485
Fish Processing is a way of preserving fish and at the same time improving their quality. In the process, the properties of the fish change. There are many ways to process fish. Some methods such as salting and drying have been used since the ancient times, long before modern technology was introduced. Others involved the use of chemicals and electrical devices. But whatever process is used, the fish to be processed should always be fresh.
1. 14.1. Salting
Salting is the process that lowers the moisture or water content of fish and other fishery products to a point where microorganisms cannot live and grow. Sodium chloride, or salt, improves fish texture because it firms up the fish. Salt partially dehydrates the fish and kills the bacteria.
Three Basic Methods of Applying Salt to Preserve Fish
• Pickle Salting - cover the fish with salt and pack them in layers in watertight containers. This forms the pickle that serves as the saturated brine solution that covers the fish completely.
• Brine Salting - immerse the fish in a saturated solution made up of 25 parts of salt and 100 parts of water.
Brine salting is done only as a temporary way to preserve fish before they are dried, smoked, or processed.
• Dry Salting - run granular salt on the fish. The proportion of salt to fish varies from 10% to 35% of the fish weight.
Steps in Salting
1.
Place the fish either in crushed ice or frozen brine.
2.
Remove the fins
124
Created by XMLmind XSL-FO Converter .
14. Fish processing
3.
Remove the head (optional).
4.
Split the fish along the dorsal section. Spread it open.
5.
Remove the internal organs such as the intestines.
6.
Take out the black membrane of the fish.
7.
Wash the fish thoroughly and drain it a little.
8.
Rub the fish well with salt.
9.
Arrange the fish in a container. Place the container inside a refrigerator.
2. 14.2. Smoking
This method combines with salting, precooking, and drying. The final process is smoking, which dehydrates the fish further. The smokes gives color and flavor to the fish.
Steps in Smoking
1.
Clean the fish by removing the gills and make 1/2 inch slit in the fish belly. Wash the fish thoroughly with clean water.
2.
Soak the fish in a brine solution (1 part of salt to 10 parts of water) for 20 or more minutes, depending on the size of the fish.
3.
Place the fish in the immersion basket made of woven bamboo strips or wire netting. The basket will be suspended during the immersion in boiling brine. Cook for 2-4 minutes or more, depending on the size of the fish.
4.
Drain the fish. Allow them to cool after being cooked in brine solution. Place it in a layer of wire screen
(rattan or bamboo) and have it dried in a coll and shady place.
5.
Smoke the fish in tin cans for 1 to 2 hours until it gets golden brown. the length of smoking actually differs, depending on the size of the fish and the smoke produced.
6.
Packed the smoked fish in coarsely woven bamboo baskets. Line the sides and bottom of the baskets with old newspaper. Cool the fish completely before packing them to allow moisture to escape and prevent the attack of mold and bacteria.
3. 14.3. Drying
This method is also known as natural dehydration. Like the salting method, it lowers the water content of the fish to a point where microorganisms, bacteria, enzymes, and yeasts cannot grow and multiply. The most popular fish preservation method is solar drying. It is done in combination with salting. Fish dried under the sun look and taste better.
Steps in Drying
1.
Wash the fish thoroughly.
2.
Soak the fish in 10% brine solution for 1/2 hour to draw out the blood.
3.
Squeeze or open the belly cavity. Remove the visceral or internal organs.
4.
Soak the fish for 3-6 hours in a concentrated brine solution to partially draw out the moisture or water content of the fish.
5.
Place the salted fish in drying trays and dry it under the sun.
6.
When the fish are thoroughly dried, pack them and store them in a clean, dry place.
125
Created by XMLmind XSL-FO Converter .
14. Fish processing
4. 14.4. Curing
This method uses chemical preservatives (including vinegar and salt), smoke, and other physical factors to reduce the moisture or water content of the fish. Cured fish or fishery products possess flavor and texture completely from those of the fresh fish.
5. 14.5. Dehydration
Dehydration is an artificial process of drying because it is done with the use of mechanical devices, such as an oven, that produce artificial heat for drying.
6. 14.6. Pickling
Pickling is a method of preserving food in brine or vinegar. It can be done with or without bacterial fermentation.
7. 14.7. Cooking
Cooking is the best way to prevent wastage or spoilage of fish. Cooking fish with vinegar, like in paksiw, prolonged the period of preservation.
8. 14.8. Canning
Canning is the packing of fish in airtight containers such as tin cans and glass jars, which prevent air and microorganisms from entering. Through the heat processing, microbes inside the can are destroyed, thus preventing spoilage under normal condition and allowing the fish to be stored for longer periods. Sardines and salmon are the most commonly canned fish in the market.
Steps in Canning
1.
Remove the scales of the fish.
2.
Remove the internal organs. Cut off the head and the tail of the fish.
3.
Cut the cleaned fish to fit the size of the can to be used.
4.
For 30 minutes, soak the fish in 20% brine solution.
5.
Half-fry the fish in oil.
6.
Fill each can with half-fried fish. Leave about 1/4 inch space. Add a tablespoonful of corn oil and tomato sauce. Do not add salt because the fish has been brined.
7.
Sealed the filled cans temporarily. Use the first roll operation of the can sealer.
8.
For 10 minutes, stem the clinched cans without pressure to exhaust the air inside the cans. Then, seal the can completely.
9.
For 45 minutes, process the sealed cans at a 15 lb. pressure using the can sealer.
10.
Immediately, coll the processed cans in running water.
9. 14.9. Fermentation
Fermentation is a fish preservation method in which fish in brine solution undergo chemical reaction. Bagoong is the most popular fermented product in the Philippines.
Steps in Fermentation
126
Created by XMLmind XSL-FO Converter .
14. Fish processing
1.
Clean the fresh alamang well. Remove sticks, shells, seaweeds, and other materials.
2.
Wash the alamang in a weak brine solution (1 part of salt to 9 parts of water). Drain it well. Cover the container while draining the alamang to keep flies away.
3.
Mix alamang thoroughly with salt ( 1 part of salt to 3 parts of alamang).
4.
Place the alamang-salt mixture in a clean container.
5.
Store the bagoong in a clean, warm place.
127
Created by XMLmind XSL-FO Converter .
15. fejezet - 15. Fisheries and aquaculture economics
Similarly to the European tendencies, inland fisheries are having a decreasing share in the domestic inland landings. In contrary, its role is beyond its decreasing economic effect has to be stressed: the Hungarian inland fisheries are unique for their environmental, economic and cultural complexity in Europe. This is and has basically been formulated continuously by the traditions, equipment, present practice and the limitations borne from the domestic and European nature conservational legislation. Hungarian inland fisheries has far more important cultural and social role than economic. Inland fisheries based on the basis environmental scientific basis have significant role in the maintenance/rehabilitation of ever shrinking environmental resources and the structure of natural fish stocks and, so the maintenance of aquatic ecosystems is becoming its dominant task.
Preservation of the fishing traditions unique in Europe is also an eminent responsibility from cultural point of view, while its social role is key issue in the employment of rural populations with low level education, as well as supplying the people in the countryside with healthy fish.
Aquaculture is a link between plant production and animal husbandry, because it involves features of both.
Climatic and soil conditions have great impact on yields. Similarly to soil quality, cultural and technical state, quality and potential fertility (natural and artificial) of each ponds are different, therefore it differentiates producers of fishery industry. Production has several advantages and disadvantages concerning efficiency and national economy. Here, the circumstances of husbandry are considered from the aspect of entrepreneurs.
Pond fish culture, which is predominantly done in man-made ponds, is based on natural processes characteristic for natural inland habitats; the fish here are produced with the interactions of natural processes and their integrated and complex management. As the result of this pond fish culture as its present status can be considered as a natural resource renewing technology, for this reason it has an increased nature-conservational, water management and social importance. Fish ponds in Hungary sustain an exceptionally high natural value.
The most important are that they provide nesting, resting and feeding habitat for the European avifauna that is connected to water. Potential of fish ponds maintaining natural values is based on the operation practice. They are also having importance in the retention of surface waters: due to the special features of the production, the ponds – to a certain extent – are capable of storing inland inundations or even floods, thus contributing the solving of these problems is a cost-effective way. Existence of fish ponds has also social values. Natural environment and angling and/or eco-touristic attractions connected to this recently are having an increasing share in the domestic tourism activities. Of course the fact that pond farms are significant employers in areas otherwise high unemployment rates.
1. 15.1. Evaluation of aquaculture from farm business management view
Aquacultue needs certain basic resources (land, pond, fixed assets, current assets, labour, etc.). One part of these resources are objective, while other part of them can be interpreted as subjective inputs. Objective inputs are the fishpond, the water and the fingerling, subjective inputs are the feed and the manure, besides professional skills.
(Of course, the choice of proper stocking ratio is a subjective input.)
1.1. 15.1.1. Organisational constraints
Forms of operation can be distinguished on the base of the following: size; stocking scheme complexity of production; duration of production; production method
128
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
Small-scale plants are up to 30 haor 150 m3, middle-scale plants are between 30 and 300 ha or 150-500 m3, large-scale plants are over 300 ha or 500 m3. It is typical for small- and middle-scale plants that they are semiscale plants, and are well harmonised with the system of agricultural activities (fishing is only one industry within the agricultural sector). Large pond fish cultures are planned as a separate fishing plant, where the special requirements of this special industry can be realised more easily.
On the basis of the scale of working, full-scale and semi-scale pond fish culture is distinguished. It means that their activity starts at rearing till producing market fish. Semi-scale pond fish cultures mainly involve the separated, smaller ponds, which are lack of the technical and agronomic conditions of the production. Small and middle-scale plants, the majority of mixed profile co-operations of pond fish culture, are semi-scale in general.
Consequently, they are dealing with rearing or market fish production. In the former case, fingerling is sold at the end of production period, in the latter case, purchased fingerling is grown to market fish.
1.2. 15.1.2. Tangible assets in production
Tangible assets are assets, which save their physical features permanently, participate in several production cycles with their total value of use (capacity). According to accounting, tangible assets are means, which serve permanently –more than one year - the activity of the enterprise in a direct or indirect way. Tangible assets involve estates, equipment, machines, other equipment, apparatus and the investments. The most important tangible asset in fish production is the fishpond, which belongs to estates. Estates are the land and every other means, which have been established in connection with the land.
Volume of investment costs depend on several factors, within which the most important ones are the following:
• Configurations of the soil, the quantity of movable soil;
• Type of the pond (barrier pond, water reservoir, etc.);
• Size of the pond (the more bigger, the less specific costs);
• Quantity and type of supplementary, ancillary equipment, canals, structures;
• Method of the construction (own or outside);
• Other factors.
When someone wants to start fish production and own fishpond is not available, it seems to be obvious to by or rent a fishpond. Proprietors wanted to sell mainly the ponds, which had bad cultural state and were degraded. In the early 90`s, for 20-40 % of the cost of establishment, ponds were available. At present (1998), the rent is about 15-30 thousand HUF/ha. It is worth to make a lease for a few years in advance. It is worth to set the dates of payment to the dates of revenues, because they are not continuous.
1.3. 15.1.3. Current assets in a aquaculture
Current assets are resources, which serves the production in a period that is not longer than a year. Current assets are stock, outstanding, securities, and cash. The role of livestock must be emphasised, because they belong to current assets, despite the fact that, e.g. breeding animals are tangible assets.
Stocks, within current assets, will be discussed in more details. Stocks serve the enterprise activities directly or indirectly, which participates in one activity process, generally, they lost their original shape during production and become the part of the new product. On the base of origin, the most important two groups are purchased stock (raw materials and commodities, fuel and combustible, maintenance and other materials) and own produced stock (animals, unfinished products and intermediate goods, finished products). Purchased stock is every stock, which was not produced by the enterprise, and got to its property or use by purchase in general. The followings are different costs, which may emerge in connection with purchased stocks:
• Purchase price and costs, closely related to purchase (e.g. cost of transport);
•
Accidental loss of value (e.g. because of decrease of market price, damage of the stock or it becomes unnecessary);
• Costs connected with storage (e.g. costs of keeping fish in over-wintering and storage ponds).
129
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
The value, which is calculated on purchase price of utilised materials in the process of production is an essential part of the Average cost, however, the accidental loss of value and storage costs are direct costs, i.e. they are not part of the Average cost.
The requirement of current assets is about 25-70 % of the total asset requirement in fish production in ponds.
Typical current assets in the area of fishing are the following:
Water, power; Manure; Expendable (nets, rubber-clothes, baskets etc.);
Lime, medicines; Feeds; Breeding and fattening animals.
1.4. 15.2.4. Human resource management
Features of human resource management of fishery, which partially are the same with that of agriculture, can be summarised as it follows:
• Connected with nature, extended in space, be exposed to weather;
• Different labour requirement in each periods of a year;
• Increased danger of accidents;
• Actual working operations and the results are separated in time;
• Changing tasks during working operations;
•
Skilled stuff is becoming older;
• Certain information on fish can be obtained only directly and the knowledge of them need many experience;
• Fishermen have to be a security man as well, because property protective problems are especially typical for the sector.
It is typical for fishery that its live labour requirement is average, therefore indexes of labour efficiency are relatively favourable comparing to other sectors. The major part of jobs have to be completed are seasonal
(spring and fall peaks) and cause job peaks. In order to compensate them, seasonal employment is generally accepted, and the payments are received as a “dinner fish”, i.e. in product.
2. 15.2. Yields, revenue and production cost
2.1. 15.2.1. Yields of aquaculture
When calculating the yield, it has to be taken into consideration the fact, in which production stage is the operation (e.g. market, growing-out, etc.), because the yields are different in rearing and producing market fish.
Domestic production takes place mainly in the three-year business form, thus the market fish is finished by the fall of the third year. A part of market fish is sold in fall, the rest can be sold continuously from over-winteringponds. A loss emerges during winter, which is called “weight loss”. Its quantity influences the final yield considered when sales are calculated.
When determining average yield level needed for economically efficient fishmeat production, it has to be considered, that fish can be produced profitably only above critical production level. Critical production level is determined by the following:
• Fixed costs for one hectare (or m3) per a year (EUR/ha(or m3)/year)
• Average sale price of fish (EUR/kg)
•
Variable cost for one kg fish (EUR/ha(or m3)/year)
130
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
Taken into consideration the above mentioned factors, critical yield level for fish, the yield where production costs come back, but there is no profit, can be calculated with the help of the following formula:
X = critical yield level for fish having zero profit or loss (kg/ha/year)
AFC = (Average Fix Costs) fix cost for one hectare (EUR/ha/year)
M = returns besides fish (HUF/ha/year)
AVC = (Average Variable Costs) variable cost for one kg fish (HUF)
PA = Average Price for fish (HUF/kg)
15.1. ábra - Figure 15.1: The most important factors influencing yields
The formula shows, that the higher is the fix cost per hectare and variable cost of production of one-kg fish, and the less is the sale price, the more yield of fish is needed for profitable production.
2.2. 15.2.2. Production value in aquacultures
In most cases, production value is equal to sales, the product of multiplication of the yield of production sold and the unit price of the product. Analysis of production value can be approached from three directions. The first, in connection with yields, the second, related to other revenues (e.g. subsidy, insurance refund), which does not increase production value, and the third, connected with sale prices.
It is worth to increase yields of fishing rationally, but only up to the point, where it results in the increase of net income as well. It is also true here, that the maximum of the net income does not belong to the maximal yield.
Increasing yields have tools, which require and others do not require additional costs. These tools need to be separated during analysis. The effect of the increase of yield requiring additional costs (feeding, manuring, water supply, etc.) on income, must be always analysed and have to be taken into consideration when making
131
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics decision about its usage. The increase of yield without additional costs (proper ratio of stocking, adequate system of interests, expertise, etc.) basically is an issue of professional intelligence and attitude, besides natural risk factors of production.
The trend of current sale price is one of the most important among factors influencing production value. Major part of domestic fish production gets to the trade as live-fish. Large-scale sale price of common carp and herbivores is lower, while it shows higher deviations for predators. Price of more valuable predator species
(pike-perch, trout) is formed as a result of bargains. It is very common that predator species rarely and in small amounts available are used for switching products in trade. The price of live-fish is seasonally fluctuating in the function of demand and supply and shows high deviations among regions. Fishmeat consumption per capita per year can be three or four times more than the average in each parts of the country (Baja, Paks, Győr, etc.), therefore there are markets having different value judgement and degree of supply. Consumer prices are generally 30-35 % higher than large-scale sale prices. In case of carp, the price of one-year old fish exceeds sale prices of edible fish with about 30-40 %, the two-year old fish with 20-30 %.
15.2. ábra - Figure 15.2: System of factors determining production value in fish-pond cultures
• species, breed, hybrid
• age group
• quality, quantity of fish
• overall evaluation of market
• linked selling
• time of selling
• informal connections
•
• state subsidy
• insurance reimbursement
• hunting, angling results of financial actions
• other incomes
• production technology
• feeding technology
• stocking
• manure application
• genetic basis
• animal health and fish loss
• human factors
• climatic factors
• situation, …
• pond soil, water quality
Pricing is one of the most important determining factor of profitability of the enterprise in the short run, and of success of products and/or services in the long run. When the price it too high, the volume of sale falls, in the ratio, how does the market react elastically to price changes. The base of pricing is that, the value of products represented for consumers, or market bearing capacity. The most common pricing methods are the cost based and market based pricing. In cost based pricing the price structure differs according to producer, service or trader activity is run by the enterprise. When making price calculations for products or services, the profit is formed according to the total cost product or service unit. Basic sale price in production and commercial activities can be determined with the help of the following equations:
132
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
When making price calculations, we must ascertain that every cost is taken into consideration and it is stressed that own salary also has to be calculated into costs in small-scale enterprises and family farms. The pricing method mentioned above can be used, when producers, services, and trades do not have to follow unconditional price accepting manner. The smaller is the market share of the given market participant, the smaller impact on market price is possible and visa versa. (E.g. A competitive organisation having low market share reduces prices significantly, its product/service is removed from the market without changing the price level for the product or the service. Consequently, when it rises the prices, it will not be able to sell its products and its action will also be ineffective for established average price level.) In market based pricing, the established market price is the standard when determining our prices, therefore margin is calculated backwards.
2.3. 15.2.3. Production cost
The volume, structure of production costsequals to the value expressed in cash of inputs used in the favour of production.It differs in each enterprises and years. Production cost depends on technology applied, production level and intensity, local conditions, supply of assets, labour supply, price of inputs, human and other factors.
During the analysis of production costs, separating fixed and variable costs 1 is needed, which is not an easy task in many cases. Volume of fixed costs per unit of product decreases with the increase of the volume of the production. To consider this fact is important especially in intensive systems having high asset requirement. In intensive systems fixed costs are relatively high.
15.3. ábra - Figure 15.3: System of factors determining production cost of fish production
•
• materials energy (electric, gas, coal, fuel)
• price level of inputs of own • interests production (e.g. self produced feed, fingerlings,)
• costs of financial actions
•
• fingerling breeders
• work time
• price level of purchased inputs
(e.g. feed, energy)
• membership fees
• extension fees
• time of purchase or storage
• insurance fees
1 It is worth to approach the analysis of production cost through three aspects. The first is in connection with natural inputs, the second with unit prices of inputs, the third with other expenses increasing production cost (these are expenses, which can be expressed as cash, but they do not involve natural inputs).
133
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
• machinery input
• running-out, low value assets
• other inputs of overheads
• dues, other expenses
Similarly to other enterprises of animal husbandry, the major part of costs are material costs (55-65 %), of which the most important are the following:
Feed; Energy;
Bases of breeding and fattening;
Water-charges;
Lime chemicals;
Medicine;
Manure and artificial fertiliser; Other materials
Materials used in fish production are products partially purchased, partially products produced in the enterprise.
Purchased products are evaluated on purchase price, but it is not the same with own produced products.
Feeding is primarily based on the use of cereals. The most important feeds are corn, wheat, barley, triticale, peas, lupine and mixed feeds made for different fishes. Besides the above mentioned feeds, others (soybean, bean, horse-bean, rye, oat) and certain by-products of the food industry and agricultural production (marc, oil seed coarse meal, oil-meal, seed clearing wastes, wheat bran) can also be fed mainly as compound of nourishment. Feed costs of a year are determined by the current prices of feeds.
Intensive systems primarily use prefabricated mixed nourishment, which meet the requirements of fish. These nourishment can not be stored for a long-time, consequently, it must be bought continuously. Higher quantities are produced only in Szarvas today, but producers usually claim about its quality. The majority of intensive systems need to base its management on import nourishment. The utilisation of different feeds is not steady in time, because feeds need to be given to fish only in certain periods.
When stocking the ponds, quantity of fish and the composition according to species and age are determined.
Developing the stocking structure determines the yields achievable in the future in a great extent. (Its role and importance is similar to setting final stand per hectare in plant cultivation). Under-stocking is a mistake likewise over-stocking. In former case, the opportunities hidden in the pond and technology are not exploited adequately, while in the latter case, the average body weight of fish to be harvested come to danger.
Concerning the water management of ponds, costs of application and costs connected with the water as a material have to be distinguished. The latter is about 10 % within material costs. Water is an objective input, production can not be imagined without it. The sector is exposed to water conservancy authorities, which are in monopoly position.
The quantity and quality of natural food determines the achievable fishmeat yield. During management everything has to be done in the favour of creating as favourable quantity and composition of plankton as it is possible. Fertilisation 2 is the most important among interventions increasing the yield. Professional fertilisation is the cheapest method of cost efficient increase of yields. Artificial fertilisers and manure can be used, but today manuring (solid and liquid) is more widely applied, forcing back artificial fertilisers (ammonium nitrate, urea, super-phosphate). The applicable quantity of manure is 1-2 tons per hectare to fry rearing ponds, 3-5 t/ha to growing-out and fattening ponds in the period of production. The quantities for artificial fertiliser are 0.1-0.2 t/ha active agent to fry rearing ponds, 0.2-0.3 to growing-out and fattening ponds per a year. Method and schedule of distribution differs enterprise by enterprise, therefore it is not discussed in more details here. It must be taken into consideration, however, that applying small rations more frequently and aiming equal application results in higher efficiency, but also in this case spreading and administrative costs are the highest. Despite of this, biologically optimal fertilisation here equals to the economic optimum. Material cost of the fertiliser is only
2 Natural yields of ponds can be increased by fertilisation and thus the yield achieved by fertilisation can be distinguished within the natural yield. Fertilisation emerges as an additional input, therefore its influences definitely have to be analysed. The phenomenon, that ponds having better natural fertility shows better reaction for additional inputs, that is the efficiency of inputs is better, is true.
134
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
5-8 % that of total material costs. In most cases slurry does not have to be paid for, only for its management, transport and spreading.
Relatively high amount of electricity is used in fish production, the major part of which serves the pumps, the rest is mainly for lighting.
Labour costs may emerge in connection with employed labour in the aspect of the enterprise (plant, business), which are: costs of obtaining the labour (recruitment, job-interview; training, retraining) and costs directly connected to employment (wages, social security charges, social benefits, etc.). Labour costs are 15-20 % of production costs. It is important to take into consideration that these expenses are emerging continuously in time, while the revenues are seasonal. Labour costsare seemed to be as fixed costs in prosperative enterprises. A part of these costs can be reduced with more machines in most fishing plants. Establishment and equipment basically determines the number and structure of employee, and work organisation. Domestic enterprises have higher average labour utilisation than their American or West-European partners (about twice), for instance.
(Because average labour requirement has been discussed earlier, we do not detail it more.)
15.1. táblázat - Table 15.1: Annual cost structure of a full-scale aquaculture farm
55-65 % MATERIALS
of which: - feed breeders
25-30 %
- 50-55 % water fertilisers
8-10 %
-
4-5 %
-
5-10 % others
-
LABOUR COSTS 15-20 %
DIVIDED COSTS
DEPRECIATION
MAINTENANCE
OTHER DIRECT COSTS
AND
5-10 %
5-6 %
2-4 %
OVERHEADS 10-15 %
Average cost is a cost per unit of product. Average costs of products are very important concerning the results of the sector and the plant. Average cost characterises the summed volume of the costs of live and dead labour assigned for the product. Average cost can be calculated with the help of the following equation:
Average cost is distinguished for staple, twin products and by-products. Depending on from what is it calculated, there are average costs calculated on the base of total product and on the base of indirect costs. When it is calculated on the base of total cost, overhead is also involved in the calculation, while in the other case it is not. Average cost calculated on the base of direct costs is more favourable because it shows better the volume of costs spent directly for the activity, but in practice, the calculation based on total cost is more often used.
135
Created by XMLmind XSL-FO Converter .
15. Fisheries and aquaculture economics
When analysing production costs, cost level is an important index. Cost level indicates, the production cost is how many percent of the total production value in a given production. Its calculation takes place with the help of the following equation:
Net income, 3 that is the profit has special role, because it shows the success of the activity and thus determines the manner of producer. Achievement or the exceed of net income expected by the producer, indicates the efficiency of the activity and encourage for additional work or innovation. Low level of net income or the loss shows the failure of the activity and raises the possibility of reduction. The final decisions influenced by other factors as well, but permanent losses force producers to give up the activity.
Profitability of farming is developed by the interrelationship of several factors. The development of income is reasonable to follow through the simultaneous analysis of factors influencing production value and production cost. Of course the aim is the maximisation of net income, but the production need to be run without causing damages in the environment, in the attitude, that the conditions of farming do not worse in the next few years.
Increasing the profit at any price often leads to robber economy, which assumes a short-run attitude in every case. Principles of sustainable development and agriculture should be treated more highlighted especially n this industry.
3 Net Income (NI) = Net Production Value (NPV) – Production Cost (PC)
136
Created by XMLmind XSL-FO Converter .
