Aquaculture - requires an understanding of how an
animal or plant grows and reproduces, ideally
throughout its life cycle.
selection of appropriate species – is a balance
between biological knowledge and economic
considerations.
biological knowledge – is needed for effective
culture of species and is extensive and it necessitates
careful consideration.
Objectives for the Selection of Culture Species
1. Increased supply/production of fish for
local/domestic consumption.
2. Employment/livelihood generation and improved
income levels.
3. Greater foreign exchange revenues, and
4. Socio-economic development and the expansion of
ancillary industries.
Criteria for Selection of Species for Culture
Not all fish species are suitable for aquaculture.
1. Availability of suitable sites for culture
2. Biological characteristics of the indigenous or exotic
species
3. Their suitability for culture
- Some species are best cultured using specific types
of enclosures
Example: Penaeid shrimps are best cultured in fish
ponds rather than in fish pens.
Carp and African catfish are commonly farmed in
freshwater rather in saltwater or
brackish water.
- Certain species are more acceptable in certain
countries than in others .
4. Their acceptability in the local or international
markets
5. Availability of technology and other requirements
for their culture.
6. Size of production or operations.
- Some cultivable species are better suited to largescale commercial aquaculture than to small-scale
aquaculture.
3 Stages of Aquaculture Operations
1. a hatchery operation which produces fertilized eggs,
larvae or fingerlings
2. a nursery operation which nurses small larvae to
fingerlings or juveniles
3. a grow-out operation which farms fingerlings or
juveniles to marketable size
Production Cycles of Selected Aquaculture Species
Reproduction is the biological process by which new
“offspring” or individual organisms are
produced from their “parents”.
2 Methods of Reproduction
1. Oviparous or Egg laying – is the fish produce eggs
that develop outside the maternal body (common for
many bony fishes). Examples: Salmon, milkfish
2. Live Bearing
A. Viviparous - the fertilization in this method is
internal and during gestation, there is maternalembryonic transfer of nutrients.
B. Ovoviviparous - the fertilization in this
method is internal, but during gestation there is
no maternal-embryonic exchange of nutrients
and developing embryo sustain on yolk reserve
of oocyte.
Example of live bearing fishes are:
- Aquarium fishes such as guppies, mollies, platies,
swordtail
- Seahorses, pipefish and angel shark
3 Reproduction Strategies
1. Non guarders - they do not guard their egg and
larvae.
Types of Non- Guarders
1. Open substrate spawners - lay
eggs in open places
2. Brood Hiders - lay eggs in
hidden places
2. Guarders - male or female or both the parents guard
the eggs and larvae after laying.
Types of Guarders
1. Substrate choosers
2. Nest spawners
3. Bearers
Types of Bearers
1. External Bearers
2. Internal Bearers
The cycles of egg laying fishes vary among species. In
general the life cycle of a fish contains the following
stages:
1. Egg
2. Larva
3. Fry
4. Fingerling
5. Juvenile
6. Adult
7. Spawning
1. Eggs Stage:
- Fertilized eggs evolve into fish. Even in ideal
conditions, the majority of eggs do not survive to
maturity. Changes in water temperature and oxygen
levels, floods or sedimentation, predators, and disease are
all threats to eggs.
2. Larval Stage :
Larval fish live off a yolk sac attached to their
bodies. When the yolk sac is fully absorbed, the young
fish are called fry.
3. Fry Stage:
Fry are now able to feed on their own. As fry
mature into adults, they go through many more
developmental stages that differ by species. During their
first few months, young fish are usually referred to as fry
(during their first few months to just less than one year in
some species).
4. Fingerling:
When the fry grow up to 10–15 cm size or
roughly equal the size of a finger it is known as
fingerling. It takes about 30–60 days for the fry to grow
up to fingerling size.
5. Juvenile Stage:
The length of time it takes for fish to mature
from fry to reproductively mature adults varies by
species.
6. Adult:
If a fish is able to reproduce, it is known as an
adult. Fish with shorter life cycles grow more rapidly.
7. Spawning:
Male fish fertilize the eggs that were released by
the female fish into the water (either into the water column
or into a nest). Not every egg is fertilized. Some fish spawn
every year after reaching maturity, others spawn at
irregular intervals (every four years, for example), while
others only spawn once and then die.
fin with 3 spines and 10-11 rays. Caudal fin truncated.
Colour in spawning season, pectoral, dorsal and caudal
fins becoming reddish; caudal fin with numerous black
bars.
- The breeding process starts when the male establishes
a territory, digs a craterlike spawning nest and guards his
territory. The ripe female spawns in the nest, and
immediately after fertilization by the male, collects the
eggs into her mouth and moves off. The female incubates
the eggs in her mouth and broods the fry after hatching
until the yolk sac is absorbed. Incubating and brooding is
accomplished in 1 to 2 weeks, depending on temperature.
After fry are released, they may swim back into her mouth
if danger threatens. The male remains in his territory,
guarding the nest, and is able to fertilize eggs from a
succession of females. If there is no cold period, during
which spawning is suppressed, the female may spawn
continuously. While the female is brooding, she eats little
or nothing.
2. Blue tilapia (Oreochromis aureus)
- is a freshwater fish native to North Africa and the Middle
East. Adults are grey-blue shading lighter towards the
belly. There may be dark broken lines running vertically
along the body. The borders of the dorsal and caudal fins
are red to pink. The spiny dorsal fin and the soft dorsal fin
are joined. The males are usually larger and reach up to 20
in. (50.8 cm) in length.
1. Tilapia - common name for cichlids
- Blue Tilapia can breed in freshwater or brackish water
with a minimum temperature of 68° F (20° C). Females
deposit eggs in single clutches and then take the eggs into
their mouth after fertilization. The females protect the eggs
until they hatch about 3 days later. Young O. aureus remain
protected in their mother’s mouth until they are about 0.4
in. (1 cm) long after which they remain near their mother’s
requirements for reproduction, so introduced populations
can take up all available habitat for breeding sites.

3. Mozambique tilapia (Oreochromis mossambicus)
Biology, characteristics and Production Cycles of
Selected Aquaculture Species



Tilapia are mouth breeding species where
parents carry the fertilized eggs and young fish
in their mouths for several days after the yolk sac
is absorbed.
Mainly freshwater fish and less commonly
found living in brackish water
Inhabits shallow streams, ponds, rivers and
lakes.
Omnivorous grazer that feeds on
phytoplankton, benthic algae, insect larvae and
artificial feeds.
3 Commercial Species of Tilapia
1. Nile Tilapia (Oreochromis niloticus)
- Body compressed; caudal peduncle depth equal to length.
Dorsal fin with 16 - 17 spines and 11 to 15 soft rays. Anal
- The Mozambique tilapia varies in its appearance due to
its ability to interbreed with related species of cichlids.
Generally, both sexes have a long, continuous dorsal
(upper) fin that starts from above the gills and continues
along the majority of the upper body. The dorsal and anal
fins are elongated towards the end of the fish and easily
reach to the tail fin when depressed against the body. The
tail fin is rounded and often has a red margin in adult fish.
- Once a female has chosen a male, she will swim over his
nest where courtship and spawning take place. Females
lay their eggs into the males’ nest before picking them up
in their mouth. The male then immediately releases milt
(sperm) over the nest, which the female gulps at to
fertilise her eggs. The female then abandons the male to
set up her own territory where she broods the embryos in
larvae). After hatching, the larvae are ideally kept
at 50/litre in hatchery tanks (either concrete,
fibreglass, canvas or polypropylene-covered
earthen tanks) maintained with Chlorella and fed
with rotifers during the early stages and later with
copepods or brine shrimp for a total of 3-4 weeks.
Following this, their size ranges between 2-3 cm
and they are ready for transport to nurseries.
her mouth for a period of 20–22 days . Once the fry are
free swimming, they will leave the female for brief periods
but return to her mouth if threatened. Females
aggressively defend eggs and fry from predators during
this time.
2. Milkfish (Chanos Chanos) - the only species in the
Family Chanidae.

The body of milkfish is elongated, moderately
compressed, smooth and streamlined. It is silvery
on belly and sides grading to olive-green or blue
on back. The Single dorsal fin, the short anal fin
and the large and deeply pork caudal fins are pale
or yellowish with dark margins. The Pectoral fins
are low on body with axillary (inner basal) scales.
The scales are cycloid, small and smooth. No
scutes (modified pointed scales) along belly.

As traditionally practiced in the Philippines,
nursery rearing is carried out in hapa type
suspended nylon nets installed in Brackish water
ponds or lagoons and in freshwater lakes within
the grow-out compartments. When natural food is
becoming depleted, artificial feeds such as rice
bran, corn bran, and stale bread or formulated
feeds are provided. In about 4-6 weeks, the fry
grow to 5-8 cm juveniles, which is the ideal size
for releasing into grow-out ponds or pens .

Milkfish may be on-grown in ponds, pens or
cages. Culture of milkfish in ponds can be
conducted in shallow or deep water systems.
 Milkfish only spawn in fully saline waters. In the
natural environment, spawning takes place near
coral reefs during the warm months of the year,
and populations near the equator spawn yearround. Milkfish eggs and larvae are pelagic and
stay in the plankton for up to 2-3 weeks. In the
wild, eggs are probably released in deeper
oceanic waters and in the outer reef region. Older
larvae migrate onshore and settle in coastal
wetlands (mangroves, estuaries) during the
juvenile stage, or occasionally enter freshwater
lakes. The larvae eat zooplankton and can thrive
and grow in water as warm as 32 °C. Juveniles
and adults eat a wide variety of relatively soft and
small food items, from microbial mats to detritus,
epiphytes and zooplankton. In the wild, juveniles
are found in mangrove areas and coastal lagoons,
and even travel upriver into lakes; they go back to
sea when they get too large for the nursery habitat,
or when they are about to mature sexually.

3. Giant Tiger Prawn (Penaeus monodon)

The giant tiger prawn inhabits the coasts of
Australia, South East Asia, South Asia and East
Africa.

The most distinct features for identification of
this species are: fifth pereiopods without
exopod; hepatic carina horizontally straight; and
gastroorbital carina occupying the posterior half
of the distance between hepatic spine and
postorbital margin of carapace. Depending on
substratum, feed and water turbidity, body
colours vary from green, brown, red, grey, blue
and transverse band colours on abdomen and
carapace are alternated between blue or black
and yellow. Adults may reach 33 cm in length
and females are commonly larger than males.
The Giant Tiger Prawn mature and breed only in
tropical marine habitats and spend their larval,
juvenile, adolescent and sub-adult stages in
coastal estuaries, lagoons or mangrove
areas. Spawning occurs at night and fertilization
is external with females suddenly extruding
sperm from the thelycum as eggs are laid in
offshore waters. Hatching occurs 12-15 hours
after fertilization. The larvae, termed nauplii,
are free swimming and resemble tiny aquatic
spiders. This first stage in larval development
does not feed but lives on its yolk reserve and
passes rapidly through six moults. The next
larval stages namely protozoea, mysis and
early postlarvae (PL) respectively remain
planktonic for some time and are carried towards
The milkfish fisheries is highly commercial,
especially in aquaculture. It is especially valued
as a food fish in Southeast asian countries.
Production System (Refer to Figure 2-1.10)

Broodstocks reach maturity in five years in large
floating cages, but may take 8-10 years in ponds
and concrete tanks. First-spawning broodstocks
tend to be smaller than adults caught from the
wild. As a result, first-time spawners produce
fewer eggs than wild adults, but larger and older
broodstocks produce as many eggs as wild adults
of similar size. Broodstocks of about 8 years old
and averaging 6 kg produce 3-4 million eggs.
Spawning usually takes place around midnight
but daytime spawning sometimes occurs.

Hatchery operations utilise either intensive or
semi-intensive systems, with an average survival
rate of 30 percent (from stocked newly-hatched

the shore by tidal currents. Protozoea, which
have feathery appendages and elongated bodies,
moult three times and then metamorphose into
the mysis stage. Mysis, which have segmented
bodies, eyestalk and tails characteristic of adult
shrimp, also moult three times before
metamorphosing into postlarvae with similar
characteristics to adult shrimp.
and supplemented by pumping. The shrimp
feed on natural foods enhanced by pond
fertilization, supplemented by artificial
diets. Production yields range from 500 to
4 000 kg/ha/yr.

Production System (Refer to Figure 2-1.12)

Healthy females (25-30 cm body length and
200-320 g weight) and males (20-25 cm; 100170 g) captured from the wild are preferably
used as broodstock in the induced ovarian
maturation process. Once the shrimp have
recovered from transport stress for a few days,
they are stocked in a circular maturation tank
that is normally covered and kept in a dark room.
After mating has occurred, which is easily
determined by the presence of a spermatophore
in the thelycum and hardening of the shell, the
eyestalk of females is unilaterally ablated for
endocrine stimulation.

The early stage of ovarian development can be
first observed within a week after ablation.
Later, gravid females with ripe stage eggs, which
can be observed by the opaque diamond-shaped
ovary under torchlight, are collected and
transferred into spawning tanks. After
spawning, these females can be re-used in the
maturation process a few times, while males can
be further used for several months, depending on
prawn health and tank conditions.

After spawning, eggs are generally kept in the
same tank for fertilization until hatching.
Nauplii are then collected and cleaned for
transfer to larval rearing tanks or for
transportation to other remote hatcheries.

There are three on-growing culture practices
namely extensive, semi-intensive and intensive
which represent low, medium, and high stocking
densities respectively.


Extensive grow-out of shrimp is
commonly practiced in Bangladesh, India,
Indonesia, Myanmar, Philippines and Viet
Nam. It is conducted in tidal areas where
water pumping is unnecessary. Shrimp feed
on natural foods that enter the pond
regularly on the tide and are subsequently
enhanced by organic or chemical fertilizers.
If available, fresh fish or molluscs may be
used as supplementary feed.
Semi-intensive ponds (1-5 ha) are
commonly stocked with hatchery-produced
seeds at the rate of 5 to 20 PL/m². Water
exchange is regularly carried out by tide

Intensive farms are commonly located in
non-tidal areas where ponds can be
completely drained and dried before each
stocking. This culture system is found in
all Penaeus monodon producing countries
and is commonly practiced in Thailand, the
Philippines, Malaysia and Australia. Ponds
are generally small (0.1 to 1.0 ha) with a
square or rectangular shape. Stocking
density ranges from 20 to 60 PL/m². Heavy
aeration, either powered by diesel engines
or electric motors, is necessary for internal
water circulation and oxygen supply for
both animals and phytoplankton. Feeding
with artificial diets is carried out 4-5 times
per day followed by feed tray checking.
In extensive culture, bamboo traps are
traditionally used for the partial harvest of
selected large shrimp. In semi-intensive ponds,
shrimps are commonly harvested by draining the
pond by tide through a bag net installed at the
outlet sluice gate. In intensive ponds, shrimps
are normally harvested similarly to semiintensive ponds. If the tide does not allow
harvesting, the drainage canal can be blocked to
allow the water to be pumped out to reduce the
water level.
4. African Catfish (Clarias gariepinus)
 The body of African Catfish elongate with
large, depressed and bony head and small eyes.
It has a large mouth terminal. Four pairs of
barbels are present. It has a long dorsal and anal
fins; without dorsal fin spine and adipose fin.
The anterior edge of pectoral spine is serrated.
The caudal fin is rounded. It’s colour varies from
sandy-yellow through gray to olive with dark
greenish-brown markings, belly white.
 African Catfish lives in lakes, streams, rivers,
swamps and floodplains, many of which are
subject to seasonal drying. The most common
habitats are floodplain swamps and pools where
they can survive during the dry season(s) due to
their accessory air breathing organs.

Clarias gariepinus undertake lateral migrations
from the larger water bodies, in which they feed
and mature at about the age of 12 months, to
temporarily flooded marginal areas in order to
breed. Prior to mating, males compete
aggressively for females with which they mate
in single pairs, the female swishing her tail
vigorously to mix the eggs and sperm and
distribute the fertilized eggs. The adhesive eggs
stick to submerged vegetation and hatch in 20–
60 hours, depending on temperature. The yolk
sac is absorbed within 3–4 days and the stomach
is fully functional within 5–6 days after onset of
exogenous feeding. Sexual differentiation
begins between 10 and 15 days after hatching.
Larvae feed and grow rapidly in the warm
(usually >24 °C) nutrient rich floodplains,
reaching 3-7 g within 30 days. As flooded
marginal areas dry up with the end of the rains,
juveniles and adults make their way back to
deeper water.
Production System (Refer to Figure 2-1.14)

Hormone treatment is employed in the
reproduction of African Catfish in captivity to
ensure large-scale production of catfish
fingerlings.

In extensive hatcheries, larvae are fed with a
mixture of cow brain plus egg yolk just after
vitelline resorption for 4-6 days before being
stocked at 50-80/m2 in nursery ponds fertilised
beforehand (usually with chicken manure) to
enhance zooplankton development.

Postlarvae are fed with single ingredients or
compounded feed. Harvesting is carried out after
24-28 days and fingerlings are graded; the
average weight at this stage is 5-7 g. Since the
recommended size at transfer to production
ponds should be >10 g, additional pre-fattening
may be carried out except when the volume of
immediate demand drives hatchery operators to
sell the fingerlings at 6 g.
There are different systems used for ongrowing
African Catfish. These include Polyculture
ponds in earthen ponds, Tanks and Water
Recirculating Systems and Cages.



African catfish fingerlings, preferably
homogenous batches with individual
weights of >10 g, are stocked into mixedsex Nile tilapia grow-out ponds. The
stocking density that allows good predation
of tilapia offspring is 0.5-1 catfish: 2
tilapia. Production in tilapia- catfish
polyculture ponds varies from 3-4
tonnes/ha/yr in rural low input level ponds
to 10-25 tonnes/ha/yr in peri-urban areas
with higher input loading and follow-up
capabilities.
In water recirculation systems, which
consist of an electric pump and a plastic
substrate biological filter, fingerlings are
stocked at 80-200/m3 and the recirculation
rate is 2-10 litres/second. Production rates
of >1 000 kg/m3/yr have been recorded in
these systems.

In some Asian countries, African catfish are
reared in cages using balanced feed. In this
case, tilapias are often stocked in the open
waterbodies to prevent eutrophication.

African catfish ponds are partially harvested
using hauling seines. At this time fish are
manually sorted; those that appear significantly
larger than average are separated and stocked
separately to prevent cannibalism. At the end of
the rearing cycle ponds are completely drained
and the pond bottom cleaned in order to catch all
the fish hidden in the mud. Partial harvests of
tanks, raceways and recirculation systems are
accomplished with grader bars to remove the
largest fish.

Harvested fish are loaded live into hauling pickups and taken to city markets. The fish are either
sold directly to consumers or most frequently to
female retailers. A minority of producers process
the fish before they are sold. Depending on fish
size and market demand, the fish may be
steaked; filleted; or sold headed, gutted, and
skinned. Smoked African catfish are also in high
demand be because they can be stored for longer
periods without power while retaining
nutritional quality.
5. Mudfish or Striped Snakehead (Channa striata) locally known as “dalag”

Channa striata is native to east and southeast
Asia. It can be found in most types of slowmoving freshwater habitat, including rivers,
lakes, ponds, canals, creeks, flooded rice
paddies, irrigation reservoirs, and swamps. It is
quite tolerant of turbid conditions and low
oxygen levels compared to most freshwater fish.

It has a long body characterized with dark blackbrown on the upper section of its body, and
bands of a white on its belly. The female is larger
than the male. It has a long dorsal fin, a pectoral
fin, a pelvic fin that is almost directly under the
pectoral fin, and a long anal fin. They also have
large mouths with sharp visible teeth with 4-7
canines, located on the bottom row of their
mouths.
Reproduction
 The striped snakehead is a monogamous fish,
because it keeps the same mate throughout the
year. It reproduces up to two times per year.
Once the eggs have been produced, if vegetation
is present, parents will use this to build a nest for
the fertilized eggs.

From the point of fertilization until the time the
young reach the fingerling stage (15-20cm), the
striped snakehead behaves aggressively to
protect their young. The striped snakehead
invests a great amount of care for their young but
when food becomes scarce the parents will eat
their young in order to survive.
6. Anguillid Eels - Japanese Eel (Anguilla japonica)
 Japanese eel is one of the 16 known species of
the genus Anguilla.

Anguillid eels are catadromous, spawning in
marine environments with the young migrating
to fresh water. Eels breed in marine waters, with
the eggs first hatching into leptocephalus larvae
(Figure
2-1.17),
which
eventually
metamorphose into glass eels (Figure 2-1.18).
The glass eels, depending on species, travel
hundreds to even thousand kilometers to reach
the mouth of rivers to start their inland migration
to fresh waters. The glass eels upon arrival in
fresh water further develop up until dorsolateral
pigmentation across the top of the body is
complete, by which time they are now
considered elvers (Figure 2-1.19). The yellow
eel stage follows the elver stage once brownish
yellow pigmentation develops at the lateral and
ventral part of the body. The yellow eels sexually
mature into silver eels, characterized by the
gray/silver lateral pigmentation, while the
ventral part is whitish. The silver eels migrate
downstream in rivers to estuaries until they
reach their spawning grounds in marine waters.
Figure 2-1.20 shows a schematic representation
of the life cycle of anguillids.
Production System (Refer to Figure 2-1.21)
 The production of eels is based on wild catches
of glass eels (elvers) that are used for further ongrowing. Glass eels and elvers are best cultured
in indoor tanks before being moved into growout facilities. Grow-out of elvers to market size
can be achieved in either tank systems or earthen
ponds.

At first the glass eels (~0.2 g each) are kept in
smaller tanks of 80-100 m3 for quarantine
purposes. Water temperature is kept stable at 2529 ºC. They are weaned onto artificial diets with
bloodworm and, later on, dry starter feed. When
the eels reach approximately 5 g they are
transferred to a juvenile production unit with
larger tanks (300-600 m3) at stocking densities
of 0.8-1.0 kg/m3. When eels reach marketable
size, they are transferred to larger ponds (5 00010 000 m2).

Eels are harvested at a weight varying from 150
g to several kilograms, depending on the target
market. Feeding is stopped a minimum of 1-2
days before harvesting. Harvesting can be
carried out by draining the pond, using a seine
net or (at feeding time) using a scoop net. The
eels are then sorted into different sizes using a
grading system. Eels that have not reached
market size are returned to the rearing tanks for
further on-growing.
LESSON 2
Aquaculture - can have a number of negative
environmental consequences, especially when practiced
intensively.
-
Aquaculture is classified in three major
environments namely freshwater, brackishwater,
marine water.
construction of aquaculture – may lead to water quality
issues, widespread destruction of mangrove forests as a
result of excessive discharged of nutrient loads from fish
ponds and other rearing facilities.
Fresh water – is defined when the salt content in it is
less than 0.5 ppt.
Brackish water - a mixture of fresh and saltwater is
defined when the salt content in it is in the range of 0.50
– 30 ppt.
Marine water - is defined when the salt content in it is
more than 30-35 ppt.
Water - the environment of all aquatic life, has some
peculiar physical and chemical properties owing to its
unique molecular structure. volume of a water mass
increases by 11% to 12% upon freezing.
1. Water temperature