• • Not to be cited without prior reference to the author International Council for the Exploration of the Sea
F I S H I N CULTURE AND
E~IR.C>~NT~ I~.A.CTS
FINLAND
TIMO MÄKINEN 1 C.M.
Ref.
1989/F:lO MEQC TABLE OF CONTENTS: 1.
Introduction 1.1. Production figures in Finland 1.1.1.
Production capacity of Farmed Fish 1.1.2
Production 1.1.2.1. Foodfish Production 1.
1.
1.
7 .
7.
1.1.2.2. Production of Fish for Stocking 2. General Legislation and Monitoring Practice 3.
Future Trends of Production and Development 8.
16.
17.
4.
Loading from F ish Farming 19.
4.1.
Nutrients 4.2. Environmental Loading through Other Substances: Chemicals and An ifouling Agents 19.
20.
5. New studies going on Concerning Environmental Impact of Fish Farming in Finland 5.1.
Sludge Collection Methodology 26.
26.
5.2. Feeding Practices and their Influence on Loading 5.3. Mitigation of the Environmental Impacts by Other Measures 5.4. Fish farming chemicals in the environment 6.
7.
Summary Literature 26.
27.
28.
2:1.
29.
1.
Introduction 1.1.
1.1.1.
Production Figures in Finland Production Capacity of Farmed Fish • Production in fish farming has progressed fast during last the decade in Finland. The total number of farms has almost tripled over 10 year period.
During the last years the increase of the number of net-cage farms has been most rapid (figure 1). The majority of these net-cage farms is located in the brackish water area along the lFinnish Game and Fisheries Research Institute Fish Farming Division P.O.Box 202 SF-00151 Helsinki Finland 1

coast-line.
f a r m s n u m b e r
800 ....._----------==_ 700 600 500 0 f 400 300 200 100 0 1978 1980 1982 YEAR 1984 1986 • ~ brackish water cage farms fresh water farms and hatcheries ~ "natural" rearing pond breeders -B total number 01 farms
number of farms 400 . . . . _ - - - - - - - - - - - 350 - 1 - - - - - - - - - - - - 1 - - .
300 - 1 - - - - - - - - - - 1 - 1 1 - 1 1 - - 1 250 -I------jl-I--I---t----I--.
200 -t-----I,--;; 150 -I----I--fl---fI-tI-clII-ffiIHflI-lU • 100 -I--+-.---liIHil--.l'.
50 o !
f I ~~
1978 1980 1982 YEAR 1984 1986 • t;::J ~ brackish water cage farms tresh water farms total ..
Figure 1. The Number of Fish Farms in Finland " Conventional pond farmers ("natural" ponds) ar all located in the inland lake areas.
growing numbers of hatcheries.
An increase of fresh water farms during recent years has mostly been with the Consequently the increase of rearing capacity has resulted in a growing (Figure
2) . . . .
In the glass cylinders are incubated mainly whitefishes , . , and on trays salmonids respectively.
for the norwegian market, years.
The remarkable high increase in tray incubation capacity is partly a response to the norwegian demand with the aim to produce smolts Today Norway is more or less independent from smolt imports and this has caused overproduction problems in Finland during last three ~ 2

• •
Incubatlon capacity In Flnland
3~housandS 999 I~ers 25 - f - - - - - - + 20 - t - - - - - - t - - t 15 -t-------: 10 _
5_ 0_ 19781960198219841988
YEAR ~ • glass incubation egg I~ers tray incubation egg liters Figure 2.
Incubation Capacity in Finland The increase of rearing capacity for fingerlings is clearly seen also in the sector of the industry employing land-based systems plastic and concrete tanks): this area of aquaculture has doubled du ring the last five years.
In part this increase occurred as a consequence of tank culture gained ground to fill the gap the reconstruction of earthen pondsystems, having less area availableof these has decreased (figure 3) .
3

Rearlng capaclly In Flnland
artilicial tanks lhousands m2 earth ponds lhousands 60 m2 50 800 -I--.-ti-&lIHl-"rlI 40 600 -IIlf-l-fHl-lH 30 20 10 o 'nn 1111
lQ7B
1980 198219841986
YEAR 1
19781980198219841986
YEAR
111
earthen ponds 1000 ITf Figure 3.
Rearing capacity in Finland, tanks and ponds the area of The area for net-cage farms in brackish water has increased very rapidly, enclosures employed in inland waters remained under 5 hectares policy of the authorities.
(Figure 4).
The decrease in area in 1987 is due to the restrictive licencing • 4

• •
nel cages thousands m2 450 400 350 300 250 200 150 100 ~ 50 I 0 1978 I tSl sea area 1980 1982 1984 1986
YEAR
• freshwater area I Figure 4.
The area of net-cages in brackish water and inland areas The number of net-cage farms has not increased in inland area (Figure 5) .
5

net-cage farms 200 180 160 140 120 100 80 60 40 20 o ~ fI 1978 • 11 • •• I I I I I 1980 1982 1984 1986 I I I year I ~ brackish water area liliiii fresh water area Figure 5. Number of net-cage farms in coastal and freshwater areas in Finland Compared to the large number of Lakes in Finland (over 180 thousands) run-off volumes.
30 net-cage farms with 5 hectares surface area is must be cinsidered as a surprising1y low involve ment of this type of aquaculture in freshwater lakes.
practice it is nowadays almost prohibited to establish a net-cage farm in the lake area.
The biggest net-cage In farms in inland waters are located in rivers with large Brackish water net-cage farms are mainly operated by those food fish producers which rear larger rainbow trout.
• The use of so called natural rearing ponds is an extensive culture method suitable for Finland with poten tial for expansion. There exist huge numbers of small stagnant ponds which are drained once a year.
The main product in these ponds is whitefish.
The natural rearing capacity has grown evenly over the last years(Figure 6).
6 •

•
9.
+ - - - - - - - I I - B - l i l 8.
+----_8_....
1i-l1J 7.
* ....._...........
6.
* - - - -.....
--111-.......
5.
+-_tl_R-II-III--U---II-it-ll-
4.
I1HHHHHlI-
3.
-fjIHII--IHHt-II~ • • 2.
"'~l!HIHlHHl--llf-II_" __ -II 1.....
~HI • • IR-JIHIHIHllHI 78 79 80 8' 82 83 e.c
85 88 87 YEAR Figure 6.
The area of natural rearing ponds in Finland 1.1.2
Production 1.1.2.1. Foodfish Production • The total food f sh production in Fin1and in 1987 was over welve million klograms (Figure 7)with large rainbow trout (99 %) as the ma n product. Only some hundred tons of salmon were produced .
7

production thousands tons/year 14 12 10 8 6 4 2 o , ~iJ ~ I i ~ 78 79 81 BQ 82 B3 YEAA B4 BS B6 87 • ~ 11 brackish water cage tanns !resh water !arms
total production Figure 7.
Food fish production in Finland In 1982 the share of production between brackish water and fresh water areas was still ven, however in 1987 only one third of all fish was produced in fresh water.
The share of production capacity of freshwater net-cage farms is nowadays under fifteen per cent of the total area of net-cages.
1.1.2.2. Production of fish for Stocking The production of fish for stocking purposes devided into can be two kinds of production: The first type produces newly hatched fry for stocking only. This produc tion strategy is maybe not considered as economically viable or biologically very effective, but it is large1y app1ied in Finland.
Regarding the stocking of salmonids the trend to release newly hatched larvae is probably more a sign of occasional overproduction than a well planned activity.
Trouts are stocked at the highest rate, excluding rainbow trout which is used outside the food fish production only occasio ~ ~ • 8

• • nally (Figure 8).
0 I i n s m i I 4 2 o 6 8
12 _ _ _ _ [[ffi •
.....
.......
_ ..........................
_ .....
_ ...................
_ .......
~ ~ [[]
.............................
.
0 11
m
~
~
1978 1980 1982 1984 1986
Figure 8.
Stockings of newly hatched salmonids in Finland Especially high is the number of coregonids stocked as newly hatched fry (Figure 9) into many water bodies. Coregonus layaretus and C oeled are most numerous and vendace and grayling are only marginal species in this connection .
9

.
.
0 n s i I
I
-
.
.
_........................... IIIJ] .
_..............
~ .................. • -"-" ~
0
Figure 9.
Stockings of newly hatched coregonids in Finland pike and pike-perch are incubated, hatched very often by fishermen and their organisations (Figure 10). Regarding pike, the natural reproduction is in general not endangered in Finland.
reared and stocked newly • • 10

• • m i I
20
i
o n 10 s 5
30
.
25
o
1978 1980 1982
1984 1986
Figure 10. Stockings of new1y hatched pike and pike perch in Finland Occasionally some other species have been stocked as newly hatched fry too and these activities are summarized in Figure 11 .
11

160 140
t h 0 U S a n d S
120 100 BO 60 40 20 .........................
0
1978 1980 1982
1984 1986
EJ ~
Bream Id •
l2l
Craylish American craylish
Figure 11. Stocking activity of reared species other than salmonids as newly hatched larvae Stocking of salmon smolts has more than doubled during the last five years (Figure 12). The main reason for this development has been the international contract concerning Baltic Sea fishery which is obliging Finland to stock a certain number of smolts annually. Nowadays Finland is overcompensating with its stocking programme the level of its own salmon fishery.
• 12

e 0 n s m i i I I 6 5 4 3 9 8 7
ITJ] • D
...................
..
..
...
• IR ~ [J]] ~ •
2 • O~ ....
Figure 12.
Stockings of salmonid species in Finland Other important salmonid species in aquaculture are trouts.
others than rainbow trout.
Brown trout is separated in three groups: sea migrating (so called Sea trout).
lake migrating (so called Lake trout) and non-migratory trout (dwarf-form); the latter one has also a special name in finnish.
Whitefish, years Peled and grayling are produced only in natural rearing ponds.
Stocking of fingerlings are mainly Coregonlls layaretlls and production has increased evenly over the past (Figure 13) as has also he area of natural rearing ponds (figure 6).
13

35
0 n s m i i I I
30 25 20 15 10 45
40
...
lIll ~
[]ll]
5 0
1978 1980 1982 1984 1986
Figure 13. Stockings of Coregonid fingerlings in Finland Demand for pike perch has been increasing in the end of June.
(Figure 14). Pike and pike-perch are also cultured in natural rearing ponds.
Pike is stocked already after some weeks of rearing usual1y • 14

• o n s i m i I I 5.0
4.5
4.0
3.5
3.0
2.5
2.0
Production of fish for stocking in Finland (number of Pike and Pike-perch) • ~ Pike Pike-perch 0.5
0.0
1978 lQ79 1980 1981 1982 1983 198-4 1985 1988 1981
Figure 14. Stockings of pike and pike-perch in Fin1and Stocking activities with other fish species have been rather occasiona1 (Figure 15). Crayfish cu1ture and stocking of crayfish is in its phase and shall in the future be fast growing branch in Finland .
15

1.1
1.0
0.9
t 0.8
u
s
a h 0.7
o
0.6
0.5
n
d
s 0.4
0.3
0.2
0.1
g m:m ~
B
0 . 0 . . w _ .
1978 1980 1982
1984 1986
Figure 15. Stockings of other species in Finland 2. General Legislation and Monitoring Practice According to water regulations practically all fish farms in Finland must have a licence issued by the Water Court. This licence specifies the maximum allow able capacity as weIl as the amount of feed to be used, the maximum allowable growth rate and the biomass of the fish.
The farmer is obliged to keep a diary for inspection by the authorities; all data concerning the use of water, feed, medication and other parameters specified in the licence must be recorded.
Farmers are also obliged to pay for control studies on their effluent quality and investigations of the environmental impacts on the recipients of the effluents.
16

• For land-based farms the sampling to document effluent water quality is done by collecting samp1es at least over 48 hours and this must be done 3-12 times annually depending on the size of the farm.
The environmenta1 impact in the recipient may be studied 3-6 times per season by measuring total phos phorus and chlorophyll content in trophogenic layer of the recipient-lake. Temperature, secchi-disc depth and (in the sea areal also the conductivity is determined.
The costs of the effluent and recipient monitoring studies have been on average at the level of 0.04 0.11 US Dollar per kilogram fish produced. In the marine area where only recipient monitoring is done the costs have been about 0.02 - 0.07 US Dollar per kilogram fish produced (Häkkilä 1988).
The Finnish National Board of Waters and Environment is represents common interests in the Water Courts. It is also the authority accepting the monitoring programs for fish farms. The attitude of the National Board of Waters and Environment is thus very decisive regarding the extent of fish farming.
For monitoring of net-cage farms the same programmes, used for freshwater land based farms have been app1ied.
The data for nutrient and chlorophyll concentrations have nevertheless only occasionally shown any detect able change in the marine environments. The biggest farms are therefore, obliged to include in the studies fishery-, benthos-, and sediment surveys as weIl.
The transfer, by the authorities, of the basic concepts from the freshwater areas to the brackish water has been misconception, since there is a lack of scientific understanding of the holding capacity of the coastal areas (e.g. such as the Vollenweider model for limnic areas).
.
The net cage farms have been seen as one case where industrial activities and the water protection measures demanded by the authorities has been the same. Because the net cage farms do not have any effluent pipes to which effluent treatment facilities could be attached some of the farmers are obliged to pay 'water protec tion charges' in the same way as other industrial operations, if they do not have any capacities to purify their effluents.
Instead of viewing them as industrial operations and thus a point source of effluents it would be better to consider marine fish farms as (aqua)culture installa 17

tions and oblige them to take care of their own environment through appropriate site selection and monitoring programmes. The monitoring programmes should be designed specifically for marine areas and not simply as application of fresh water monitoring proto cols.
3. Future Trends of Production and Development The Finnish Foundation for Development Areas forecasted the development in fish farming in Finland and provided the following evaluation (Hakanen et al.198?): The food fish production is expected to double in the early 1990's. Rainbow trout will again be the major species farmed, but also farming of other fish species will gain importance. The main market will be the domestic one. Production of young fish is not expected to limit the food fish production in the future. On the contrary, there may be occasional overproduction of smolts.
In the same study the authors could not anticipate any great increase in the production for stocking natural waters, but changes may occur in the relative numbers of fish species stocked in Finland.
The Finnish fish farming industry employs about two thousand persons directly (Partanen et al. 1988).
Indirect employment effects are estimated to be several times the above figures contributing to the economic growth of the society. Fish farming is seen as an area which still has some room for expansion and which may employ more people in the remote areas, especially in those developing in Finland.
Fish farming in Finland is now a common and weIl established trade. Out of the fish food production, about 98 % consists of large-sized, i.e. over 800 9 rainbow trout. The sales value of the production was ab out 55 million US dollars in 1986 (figure 16).
• 18

Value of fish production in Finland 80 million dollars / year ;:;l.===============::::;'1 70 60 50 40 30 I l,1------,.-I!I-IIlf-IIHlHI-11 1978 1980 1982 YEAR 1984 1986 • foodlish prod. million m Slocking-prod. million $ $$ Figure 16. The value of farmed fish production in Finland As a general trend in the Finnish fish farming there is now a relative increase of food fish production in marine areas, ing.
while the production of fingerlings is becoming relatively more prominent in freshwater farm • 4.
4.1.
Loading from Fish Farming Nutrients The production of fish to stocking size in Finland is now estimated to be about 600 tonnes annually.
about culture.
This means that an estimated amount of about 7 tons phosphorus and 45 tonnes nitrogen loading is derived from this The nutrient loading from food fish farming is esti 19

mated to be about 140 tonnes of phosphorus and 950 tonnes of nitrogen annua1ly.
is presented in Figure 17.
The contribution of fresh water and marine farming to this overall nutrient load (Mäkinen 1988b).
estimated phosphorus Ioad 180 160 140 120 100
tonneSia 80
60 40 20 o
...YL.&.....L.&.....L.&.. .
19791981198319851987 estimated nitrogen load 1.2
1.0
0.8
1000x 0.6
tonneSia 0.4
0.2
0.0
...LI1..lL,j1L&....
L.&.L&
1979 1982
1985
• §§l inland areas brackish water areas • ~ inland areas brackish water areas Figure 17. Estimated phosphorus and nitrogen load The contribution of the nutrient load from the fish farms to the total nutrient load derived from human activities is rather marginal in Finnish waters : under four percent for phophorus and under two percent for nitrogen (KOMITEANMIETINTÖ 1986) 4.2.
Environmental Loading through Other Substances: Chemieals and Antifouling Agents Other harmful substances than suspended solids and nutrients enter the environment through fish farming.
They are mainly comprised of (1) chemieals for desin feet ion of ponds, tanks and equipment and (2) chemieals used as therapeutic agents against diseases and (3) antifouling agents.
The following quantities of various substances were eompiled from da ta collected by the National Veterinary Adminis ration and by the National Board of Waters and 20

Environment in Finland. Overlap of data and missing data were corrected as far as possible. However, and describe only the scale of the consumption of medication and other chemicals in finnish fish farming.
the data presented here contain still some inconsistencies The therapeutics mostly used are bathing agents with the common marine salt as the major harmless substance.
It is used mainly against Chjlodonella parasite in production of fingerling in fresh water farms.
tons (Figure 18).
The total amount of salt presently used is about hundred Formaldehyde is another agent for treatments and is mainly used against Ichtyobodo and monogens. The amount used is about 4.5 tons annually (Figure 18).
The third comrnonly used agent is malachite green mainly against IchtyophtirjlJs and often employed together with formaldehyde.
The use of this chemieals amounts to about 300 kg annually (Figure 18). Small amounts of chloramine and benzalconchloride are also used in the country. The latter is used also for desinfection of equipment on farm sites.
21

k 9 5 5 a n d t h U ° The Use of chemicals in Rsh Farming desinlection agents. CaOH2 120 _.............
100 bathing agents, NaCI 90 100 80 60 5 a n d t h U ° 80 70 60 50 40 40 20 k 9 5 30 20 10
O......
=J......I...:...I-..I......;:l".
.
1985 1986 year 1987 1985 1986 year 1987 k 9 s t h U ° 5 a n d bathing agents. formaldehyde 5.0
.
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0 .....
~.Ioo-..L....;;;:~.I-....J. k 9 1985 1986 year 1987 other therapeutic agents 300 _ _ .
250 200 150 100 ··..····..········.. WI .~.
50
O .......__......
L....-I:;llI",..I.,;,.,II_
1985 1986 year GJ malach~e green • I!I
benzalconchlorid chloramin 1987 Figure 18. The use of chemicals in finnish fish farming, fresh water area Among the desinfection agents chalk is the one used at the largest amount: about 120 tons annually (Figure 18).
It is not only used for desinfection purposes in earthen ponds but also as a medium for pH adjustment in natural rearing ponds.
5mall amounts of other des in fectants are also used, such as iodophors for egg 22

• desinfection. With regard to anesthetics MS 222 the one used most commonly.
With regard to antibiotics in Finland, the use of oxytetracyclin in, has been growing when furunculosis was diagnosed more frequently in inland area.
The total use in fresh water was about 600 kg in 1986 19) .
(Figure oxytetracyclin. Ireshwaterarea 600 .
k 9 500 400 300 200 100 o 1985 1986 year 1987 5 a n d t h o U k 9 5 oxytetracyclin in brackish water area 1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
~"",""; ........
0.3
0.2
0.1
O.O .....
=J...-
1985 1986 year 1987 Figure 19. The use of antibiotics in fish farming in finland In marine areas the use of other chemicals than antifouling agents and antibiotics is rather small.
Oxytetracyclin is again the mainly used antibiotic in brackish water net-cage farms with a total amount of about 1050 kilograms annually (Figure 19).
The use of chemicals in food fish production has been rather marginal in Finland. The introduction of vibrio sis vaccination reduced greatly the application of antibiotics in the early 80s.
summer.
produced In
1988
the use of antibiotics was much higher due to the exceptional warm Figure 20 depicts the relative amount of all chemicals and antibiotics used per kilogram fish (antibiotics comprising mainly oxytetracyclin with terramycin at marginal levels).
The use of chemi cals seems to be very much higher in fresh water fingerling production and has also been growing during 23

last years. Also when the more harmless marine salt and chalk are not considered in fingerling production in 1987, this branch of the industry used about hundred times more chemieals than the food fish production sector (Figure 20). Not all of this amount was used for chemotherapy but also for desinfection of equipments and other purposes.
The use of antibiotics is more similar in fresh water and brackish water production. The summer 1987 was rather cold. Consequently the use of oxytetracyclin stayed at lower level.
24

9
I
k 9 The Use 01 chemicals in FlSh Farming all chemicals fresh water area 70 __ .
m all chemicals brackish water area 300 60 50 250 k 9 200 s i h r P o d 40 30 20 10 0 ...............
_1...-
1985 1986 year 1987 150 p r o d i s h 100 50 o 1985 1986 year 1987 • D glkgfish glkg fish CaOH2+NaCI • o mglkg rngIkg CaOH2+NaCI oxytetracyclin, freshwaterarea m 16Ö .
9
I
k 9 140 120 .,'.
I i s 100 80 h 60 I i s h
I
9 k 9 m oxytetracyclin in brackish water area 160 .
140 120 100 80 60 p r o d 40 20 P r 0 d 40 20 0 1985 1986 year 1987 1985 1986 year 1987 Figure 20. The Use of chemieals and antibiotics per kilogram of farmed fish in Finland The antifouling paints are applied mainly for mainte nance of brackish water net-cages.
The amount used is s t i l l now unknown and, here.
therefore, In fresh water farms, cannot be considered antifouling substances are 25

used only occasionally, mainly on outdoor plastic and concrete tanks. Organic tin substances (TBT) are not among those paints used by fish farmers in Finland. The most effective compound used in paints is usually based on copper.
5. New Studies going on Concerning Environmental Impact of Fish Farming in Finland 5.1. Sludge Collection Methodology Testing of a new innovative technique for sludge collection from earthen ponds is presently in progress in Finland (Karttunen et al. 1988). A prototype of a specially deviced unit, consisting of floating "whalebones" on the bottom for trapping and collecting of drifting sludge was tested. The aim is to develop an economic way to remove sludge from old fish farms employing very long earthen ponds. The particular intention is not to reconstruct the whole farm in accordance with modern criteria.
5.2. Feeding Practice and their Influence on Waste Load The quality of feed is decisive for loading figures.
The development of feed, especially the improvement of its nutritional value and feed conversion efficiency together with the lowering of excessive nutrient con tents, gives far better results on reducing the envi ronmental effects of aquaculture than any treatment method for effluents. The reduction of phosphorus and nitrogen contents in relation to the content of metabo lizable energy and the increase of digestibility to gether with feeding optimization can quite easily help to reduce the nutrient load by about two third when compared to earlier feed formulations (Mäkinen 1988a, Ruohonen & Mäkinen 1987).
Regarding net-cages, especially in marine areas, and rearing of larger fish there is still a need for research on feeding optimization, relating bioener getic studies and the use of markers for measuring ingestion, egestion and digestion rates. Also, indirect methods ~ ~ 1~ measure feed losses on full-scale net-cage farms are urgently needed. A new project aiming to measure the feed los ses in different ways has recently been implemented in Finlano.
26

5.3. Mitigation of Environmental Impact by Other Measures Besides internal measures to reduce the pollutional load from net-eage farms the selection of an appro priate site for plaeing of a farm is one of the most important ways to minimize harmful environmental effects.
In 1987 the Nordie Couneil of Ministries agreed to fund a three years projeet with the aim to develop an environment al impact assessment strategy for marine fish farms. This projeet will serve as a model to be utilized for planning purposes and for a better exploi tation of coastal areas.
The preliminary report of this projeet on "Basic Coneepts concerning assessments of environmental effects of marine fish farms" 1s already pub11shed (Hakansson et al. 1988).
The central part of this project was to develop a load diagram similar to the weIl known and widely applied Vollenweider diagram for limnic areas. The idea still is to develop an analogous diagram of the environmental risk assessments for the marine areas as the projeet progresses. The concept presupposes that the choiee of the most suitable parameter is made for describing the environmental sensitivity of an area, as weIl as the observed biological effect.
The sensitivity term shall be a quantitative index which includes different morphometrie parameters de scribing the size (shoreline length, maximum depth, water surface area, total area, section area, water volume), the form (mean coastal width, me an depth, mean slope) as weIl as the topographie openness and bottom dynamie conditions of a coastal area. The effect term shall be measured by some praetieal and simple para meters (i.e. secci-disc depth, chlorophyll-a content) In the diagram these two variables will be eombined with the knowledge of the "dose" (= BOD and/or nutrient 10ading or the size of the farms). The acceptable level of loading (size.of the farm) will thus be defined.
27

EFFECT
(E)
loadlng (0) BAD
GOOD
high low SENSITIVITY (w i)
Figure 24. The load diagram (see the text) With the assistance of this diagram which reflects an input-output-model, i t should be possible to compare the sensitivity of different areas and use the results in regional planning and for appropriate site selec tion.
It is hoped that the model will allow to to predict the impacts of a certain fish farm size in selected area.
5.4. Fish Farming Chemicals in the Environment The clearance time for chemotherapeutants such as oxytetracycline is 30 days in Finland and this time limit applies for the summer time. During winter this time is langer and lasts up to the 60 days. The exact time is determined for each operation by the veterina rians.
The residues and the persistence of oxytetracycline was studied in wild fish and sediments in 1987 in the finnish archipe1ago (Björklund et al. 1989). In wild fish residues cf oxytetracycline were detected up to 13 days after the medication. The half-life of oxytetracycline in fish farm sediments were 9 days on other and 419 days on other farm.
28 •

• 6. Summary Production
in
fish farming fast during the last
in
Finland has increased decade. The total number of farms has almost tripled over aperiod farms is located
in
the Finnish coast-line.
10 years.
Number of net-cage farms increased most rapidly during the last years. The majority of these cage the brackish water areas along The nutrient load from food fish farming in estimated to have contributed about 140 1987 tons of was phosphorus and input to the environment. The contribution of fresh water and marine farming to this overall nutrient load 950 tonnes of nitrogen to the total is presented. The relative contributions of this load to the total nutrient load derived from human activities is rather marginal
in
Finnish waters: inputs are under four percent for phosphorus and under two percent for nitrogen.
In marine areas, the use of other chemica1s than antifouling agents and antibiotics has been sma1l.
Oxytetracycline is the antibiotic substance mostly used
in
brackish water net-cage farms. The total amount has been about 1,050 ki10grammes annually.
7. Literature Björklund, H., Bondestam, J. & Bylund, G., 1989: Residues of Oxytetracycline in Wild Fish and Sediments from Fish Farms.-Aquaculture (submitted manuscript), 17 pp • Hakanen, M., Lindqvist, 0., Orpana, M.
& Vuorinen, P., Kalanvilje1yn elinkeinotutkimus (Fish farming as a source of livelihood, in finnish with english sum mary).- Kehitysa1uerahasto OY A 10: 84 pp.
1987: Hakansson, L., Ervik, A., Mäkinen, T.
& M~ller, B., 1988: Basic Concepts concerning assessments of environmental effects of marine fish farms.- Nord 1988:90, 106 pp.
Häkkilä, K., 1988: Ka1anviljelyn velvoitetarkkailu.- Esi telmä AEL:n kurssilla "kalanviljely ja vesilainsäädäntö 18. 2. 1988.
29

Karttunen, E., Ritola, O.
& Matinvesi, J., 1988: Ka1anviljelylietteen poistaminen maauoma-a1taista (The Removal of Fish Farm Sludge in Earthen Ponds, areport in finnish, 19 pp.) KOMITEANMIETINTÖ, 1986: Vesiensuoje1un tavoiteohjelma vuo teen 1995.- Komiteanmietintö 1986: 42, 191 s.
Mäkinen, T., farms in Finland.- in: Pursiainen, M.
contributions on suspended solids from land-based fish farms, 1988a: Report on suspended solids from fish (ed.), National Papers presented at the first session of the EIFAC working party on fish farm effluents, The Hague, Netherlands, 29-30 May and 1 June 1987: 17-28.
Mäkinen, T., 1988b: Ka1anvilje1yn vesistökuormitus ja sen vähentäminen (The loading from fish farming and its reduction; in finnish, swedish and english, compiled). University of Jyväskylä, thesis, 220 pp.
Licentiate of Phi1osophy Partanen, H., Vihervuori, A.
& production and processing, Hilden, M., 1988: Employment in the fishing industry and aquacu1ture, national fish and fishing fleets in Fin land 1985-87.- P.M., Finnish Game and Fisheries Research Institute, Fisheries Division, 4 pp.
Ruohonen, K.
& Mäkinen, T., 1987: Feeding optimization of rainbow trout as an app1ication of Amsterdam June 2-5 1987 (in print) .
a growth model with response to environmenta1 factors.- Aquacu1ture 87, • 30