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Quantitative estimation of stamina of wild and hatchery-reared Atlantic salmon (Salmo salar L.)
Aquaculture, 71 (1988) 81-87 Elsevier Science Publishers B.V., Amsterdam -
81 Printed in The Netherlands
Quantitative Estimation of Stamina of Wild and Hatchery-Reared Atlantic Salmon (Salmo salar L.) Yu.A. SHISTOV
and I.L. SHCHUROV
Institute of Biology, Karelian Branch, U.S.S.R. Academy of Sciences, Petrozauodsk Karelia (U S.S.R.)
185610,
(Accepted 16 December 1987)
ABSTRAC!T Shustov, Yu.A. and Shchurov, I.L., 1988. Quantitative estimation ofstamina of wildand hatcheryreared Atlantic salmon (Salmo salar L.). Aquaculture, 71: 81-87. Evidence for stamina of wild Atlantic salmon (Salmo salar L.) in the river habitats of the Kola peninsula and hatchery-reared parr from fish-rearing farms of the Murmansk region is presented. Fish stamina was assessed by measuring the maximum swimming force developed by fish in special devices at the moment of their escape response from a strong electric stimulus. Data on true stamina of hatchery-reared young salmon may be useful both for assessing the degree of fish adaptability before their release into natural water basins and for prognoses of the percentage recapture of adult hatchery fish.
INTRODUCTION
At the present time many countries, including the Soviet Union, have turned to the artificial rearing of Atlantic salmon (Salmo salar L. ) . To realize the full potential, it is the task of scientists and fishery managers to develop methods of increasing the quality of reared salmon, to improve the system of fish release into natural waters, and to take measures to improve the spawning and rearing areas of salmon rivers (Netboy, 1969; Loftus, 1976; Harris, 1978; Brunet; 1980; Mills, 1980; Bakshtansky et al., 1981; Kazakov, 1982; Shustov, 1983; Enderlein, 1984; Vibert, 1984). It is known that the ecological conditions for hatchery-reared Atlantic salmon differ from natural ones. In rivers wild salmon live in the fastest rapids and shallows, constantly being affected by strong water currents of 0.3-0.8 m/s (Kalleberg, 1958; Keenleyside, 1962; Saunders and Gee, 1964; Mitans, 1975; Shustov et al., 1980). Hatchery-reared salmon parr are kept in devices such as concrete and plastic tanks, trout flumes and rearing ponds. The flow rates are generally lower than in a river. It is therefore understandable that the stamina of fishes reared in such different ecological conditions is also different.
0044-8486/88/$03.50
0 1988 Elsevier Science Publishers B.V.
82
We have found earlier that the rate of adaptation of hatchery-reared Atlantic salmon to river conditions depends on their stamina. If the fish are kept in hatchery tanks with a current speed of 0.4-0.6 m/s for 1.5 months, the swimming performance of such trained parr is twice that of normal hatchery fish (Shchurov et al., 1986a). On release, the trained fish were less subject to displacement by the current flow, were more successfully distributed in the fastest rapids and shallows and had better feeding rates (Shchurov et al., 1986b). Similar results were found for hatchery-reared brown trout, Salmo trutta L. (Cresswell and Williams, 1983). The present report is based on the results of our experiments carried out in August 1985 and July 1986 at the fish-rearing farms and in the rivers of the Kola peninsula in the northern U.S.S.R. The stamina of wild and hatcheryreared Atlantic salmon was determined by a method similar to that used by Nashimoto (1980) who studied the stamina of rainbow trout, Salmo gairdneri. This involves registering the maximum swimming forces developed by fish at the moment of their escape response from a strong stimulus, using a dynamometer. The method is simple, reliable and, with the use of SI units like the gram, it allows easy comparison with other workers’ results. The results of our studies are based on six series of experiments in which the stamina of 98 wild parr (age 2 + to 4 + ) and 189 hatchery-reared fish (age 2 + to 3 + ) was investigated. Since the swimming performance of fish (Pavlov, 1979 ) , including young Atlantic salmon (Rimmer et al., 1985 ), depends on the season and environmental temperature, this paper presents the results of experiments conducted only in mid-summer within a narrow range of water temperatures, 13-15 “C. METHODS
Wild salmon parr from the spawning rivers were caught in the fastest rapids and shallows at a depth of 0.7 m with a small fry net (mesh size 6 mm). The fish were immediately placed in plastic tanks filled with water, which were laid on the river bank near the device. Similar methods were used to catch hatchery-reared salmon parr from trout channels and rearing ponds. This procedure produced no traumatic effect on the fish, and the experiment could begin 0.51 h after the fish recovered. The device for registering fish swimming forces consisted of two parts: a 50cm-long plastic box with a water volume of 5 1 and a dynamometer with calibration up to 250 g. A thin fish line from the dynamometer lever was attached to the dorsal fin of a fish with a small clutch which exerted no traumatic effect on the fish. The fish escape response was provoked by two-three momentary electric stimuli from portable batteries, whose tension current was not more than 1 V/ cm of the device length, or by finger tapping on the device. The maximum
83
swimming force was registered by the maximum throw of the point of the dynamometer, and the fish length was measured before release. The experiment with each individual lasted for 20-30 s, and the measurement of the maximum force took 1-3 s. RESULTS
The results showed that the stamina of wild and hatchery young salmon depends mainly on their size (Figs. l-2; Table 1). The longer the fish is, the larger are the values of the swimming force recorded with the dynamometer. At the same time, both wild and hatchery salmon parr are characterized by a significant spread of individual data, so that different individuals of the same size may have stamina values which differ by a factor of two (Figs. 1, 2). For force(g)
Swimming
*
B
.
120
.*. .
i
-
c
t
.
100 -
eu
. .
IIr./
. .
l
”
”
l
60 -
y
.
_-
“.
.-
40
-0 t
l
. 20
Length km)
i13
$1
3
11
1n
11
12
13
z l’(
I
81
7
8
1
I
II
9
m
11
12
12
* *
e
3
I
10 11
II
12
I
13 74
Fig. 1. Stamina of young Atlantic salmon in river conditions. Abscissa - fish sizes (cm); ordinate - swimming force (g). Results of experiments A, B, C are given in Table 1.
E
/
DL-i-7
a
9
10 11
12
7
. e L. .. . . .
F
. a.. . . . -0. _. . b.
. l . *
3
IO
11 12
7
. /
. .. ./ . . .
l
.
/ . n
. l
. .
.
.
Length 8
3
10 11
12
(cm)
13
Fig. 2. Stamina of hatchery-reared young Atlantic salmon. Abscissa - fish sizes (cm); ordinate swimming force (g). Results of experiments D, E, F are given in Table 1.
Fish-rearing farms Taibolsky
Knjazhegubsky
Kandalkshsky
D
E
F
Kitsa
Umba
Rivers Pechenga
trout channel (0.05-0.1) trout channel (0.05-0.1) rearing pond (0.0)
smooth ridge (0.3-0.5) high rapid (0.8-1.5) ridge (0.3-0.5)
50 50
Y= -145+26.0X-0.689p Y= -20.3+2.91x+0.380x~ Y= -35.2+5.23X+O.l74p
0.867 0.924
hatchery hatchery
50
49
Y=47.3-
11.6X+ 1.15x
40
48
Number of fish in experiment
Y=19.7-8.95X3+1.27x2
Y=93.7-17.1X+1.3oX
Equation of regression, where: Y = fish length (cm) X=swimming force (g)
0.864
hatchery
0.869
0.844
wild hatchery fish 1 month after release
0.157
Coefficient of correlation between fish length and swimming force
August 1985 and July 1986)
wild
Origin of juveniles
salmon (Kola peninsula,
(flow
Ecological conditions rate, m/s)
Numbering of experiments (see Figs. 1,2)
Place of experiment
young Atlantic
Stamina of wild and hatchery-reared
TABLE 1
85
example, in the Pechenga river, wild fish 12 cm long had a minimum force of 50 g and a maximum force of 100 g (Fig. 1A). Hatchery-reared salmon parr grown in the trout channels of the Knjazhegubsky Fish-Rearing Farm whose length was 10 cm had a spread of data for swimming force from 30 to 60 g (Fig. 2E). As expected, the stamina of fish living in different ecological conditions differed considerably. Wild salmon parr from the Umba river caught in shallows with a swift current of 0.8-1.5 m/s were especially strong (Fig. 1B). Lower values for stamina were characteristic of wild and hatchery-reared salmon living in conditions with a current speed of 0.3-0.5 m/s (Fig. lA, C). Of all the hatchery fish, the weakest were those grown in rearing ponds where there was practically no current (Fig. 2F). If the stamina of wild young salmon is taken as the norm, then the fish originating from the ponds will be 1.5-2 times weaker than the ,wild fish. DISCUSSION
Similar results to ours were found by Green (1964)) using a test for swimming performance: wild young brook trout, Salmo truttczfario L., had greater swimming force than “domestic” fish. Similar data were obtained by Barns ( 1967) for young sockeye salmon, Oncorhynchus nerlza (W. ) . Hatchery-reared juveniles are adversely affected by sharp changes of conditions from the hatchery to the natural environment, especially because of stress during transport, and most of them die in the first few days after release (Kamyshnaya and Tsepkin, 1973; Bakshtansky et al., 1981). We have no reliable evidence on which individuals are most vulnerable. Individuals with low stamina are presumably not strong enough to resist the flow, cannot escape from predatory fish and birds, and cannot pursue food items and get sufficient amounts of drifting food. These possibilities are supported by our work on training hatchery salmon parr before their release into rivers (Shchurov et al., 1986a). We have found that the trained fish with higher stamina values adapt considerably more successfully to river habitats (Shchurov et al., 1986b). The general practice of salmon rearing shows that larger hatchery salmon stand a better chance of survival under natural conditions. Thus, Carlin (1968) found that increase in size of hatchery smolts led to a 2.3% per cm increase in the rate of fish return. This seems to be achieved only if high-stamina fish are released. There are several methods for increasing fish stamina in the conditions of fish-rearing farms. Thus Kol’gaev (1978) suggests growing salmon juveniles in long, narrow flumes providing an increase of the flow rate. Thorpe and Wankowski (1979) suggest substituting circular for radial flow in standard tanks. We think that training of fish is also required. Thus the 1.5-month training of hatchery Atlantic salmon parr resulted in a 2-fold increase of their swimming performance (Shchurov et al., 1986a).
86
REFERENCES Bakshtansky, E.L., Nesterov, V.D. and Chernitsky, A.G., 1981. Recommendations for release of young Atlantic salmon and sea trout. M., V.N.I.I. Mor. Ryb. Hoz-va i Okeanogr., 29 pp. (in Russian). Barns, R.A., 1967. Differences in performance of naturally and artificially propagated sockeye salmon migrant fry as measured with swimming and predation tests. J. Fish. Res. Board Can., 24 (5): 1117-1153. Brunet, A.R., 1980. Present status of the Atlantic salmon stocks in France and environmental constraints on their extension. In: A.E.J. Wont (Editor), Atlantic Salmon: its Future. Proc. 2nd Int. Atlantic Salmon Symp., Edinburgh, 1978. Fishing News Books, Farnham, pp. 128134. Carlin, B., 1968. Salmon tagging experiments. In: Atlantic Salmon Assoc. Centennial Award Fund. Series of Lectures. Montreal, Que., Canada, lecture 2, pp. 8-13. Cresswell, R.C. and Williams, R., 1983. Post-stocking movements and recapture of hatchery-reared trout released into flowing waters - effect of prior acclimation to flow. J. Fish Biol., 23 (3): 265-276. Enderlein, O., 1984. Stocking of fish in Sweden from the perspective of tagging. EIFAC Tech. Pap., 42, suppl. 1: 269-281. Green, D.M.I., 1964. A comparison of stamina of brook trout from wild and domestic parents. Trans. Am. Fish. Sot., 93 (1): 96-100. Harris, G.S., 1978. Salmon propagation. The final reports? Water (G.B.), 20: 7-8. Kalleberg, H., 1958. Observations in a stream tank of territoriality and competition in juvenile salmon and trout (Salmo salar L. and Salmo trutta L.). Rep. Inst. Freshwater Res., Drottningholm, 39: 55-98. Kamyshnaya, M.S. and Tsepkin, E.A., 1973. Materials on ecology of pike Esox lucius L. in the lower reaches of Umba river. Vopr. Ihtiol., 13 (6): 1105-1111 (in Russian). Kazakov, R.V., 1982. Biological bases for Atlantic salmon production. M., Legkaya i Pishchevaya promyshlennost, 144 pp. (in Russian). Keenleyside, M.N.A., 1962. Skin-diving observations of Atlantic salmon and brook trout in the Miramichi River, New Brunswick. J. Fish. Res. Board Can., 19 (4): 625-634. Kol’gaev, A.M., 1978. Some peculiarities in estimation of water supply of salmon-rearing farms. Ryb. Hoz-vo, 5: 44 (in Russian). Loftus, K.H., 1976. Science for Canada’s fisheries rehabilitation needs. J. Fish. Res. Board Can., 33 (8): 1822-1857. Mills, D.H., 1980. Scottish salmon rivers and their future management. In: A.E.J. Wont (Editor), Atlantic Salmon: its Future. Proc. 2nd Int. Atlantic Salmon Symp., Edinburgh, 1978. Fishing News Books, Farnham, pp. 70-81. Mitans, A.R., 1975. Efficiency of natural and artificial reproduction of Baltic sea salmon as the result of its freshwater period of life. In: Rybokhozyaistvennye Issledovaniya v Basseine Baltiiskogo Morya. No. 11. Zvaygzne Press, Riga, pp. 110-152 (in Russian). Nashimoto, K., 1980. The maximum swimming force of rainbow trout. Bull. Jpn. Sot. Sci. Fish., 46 (8): 949-954. Netboy, A., 1969. Salmon biology and problems of management - Can the salmon be saved? In: Atlantic Salmon Assoc., Centennial Award Fund. Series of Lectures. Montreal, Que., Canada, lecture 2, pp. 11-15. Pavlov, D.S., 1979. Fundamentals of biological control of fish behaviour in water stream. Nauka, Moscow, 319 pp. (in Russian). Rimmer, D.M., Saunders, R.L. and Paim, U., 1985. Effects of temperature and season on the position holding performance of juvenile Atlantic salmon (Salmo salar L.). Can. J. Zool., 63 (1): 92-96.
87 Saunders, R.L. and Gee, J.H., 1964. Movements of young Atlantic salmon in a small stream. J. Fish. Ree. Board Can., 21 (1): 27-36. Shchurov, I.L., Smirnov, Yu.A. and Shustov, Yu.A., 1986a. Period of adaptation for hatchery young sal.mon Salmo salar L. to river conditions after the improvement of fish stamina prior to the release of fish. 1. Possibility of training young fish in hatcheries. J. Ichthyol., 26 (2): 317-320 (in Russian), Shchurov, IL., Smirnov, Yu.A. and Shustov, Yu.A., 1986b. Period of adaptation for hatchery young salmon Salmo salar L. to river conditions after the improvement of fish stamina prior to the rel.ease of fish. 2. Behaviour and feeding of trained young Salmo salar L. in a river. J. Ichthyol., 26 (5): 871-874 (in Russian). Shustov, Yu.A., 1983. Ecology of young Atlantic salmon. Karelia, Petrozavodsk, 152 pp. (in Russian). Shustov, Yu.A., Shchurov, I.L. and Smirnov, Yu.A., 1980. Conditions of existence, behaviour and distribution of young Salmo salar in a river. J. Ichthyol., 20 (1): 119-123 (in Russian). Thorpe, J.R. and Wankowski, I.W.I., 1979. Feed presentation and food particle size for juvenile Atlantic salmon, Scdmo salur L. In: Finfish Nutrition and Fishfeed Technology. Proc. World Symp., Hamburg, 1978. Heenemann, Berlin, vol. 1, pp. 501-513. Vibert, R., 1984. Les saumons: espece manatee ou d’avenir? Peche Mar., 63 (1277): 444-449.
81 Printed in The Netherlands
Quantitative Estimation of Stamina of Wild and Hatchery-Reared Atlantic Salmon (Salmo salar L.) Yu.A. SHISTOV
and I.L. SHCHUROV
Institute of Biology, Karelian Branch, U.S.S.R. Academy of Sciences, Petrozauodsk Karelia (U S.S.R.)
185610,
(Accepted 16 December 1987)
ABSTRAC!T Shustov, Yu.A. and Shchurov, I.L., 1988. Quantitative estimation ofstamina of wildand hatcheryreared Atlantic salmon (Salmo salar L.). Aquaculture, 71: 81-87. Evidence for stamina of wild Atlantic salmon (Salmo salar L.) in the river habitats of the Kola peninsula and hatchery-reared parr from fish-rearing farms of the Murmansk region is presented. Fish stamina was assessed by measuring the maximum swimming force developed by fish in special devices at the moment of their escape response from a strong electric stimulus. Data on true stamina of hatchery-reared young salmon may be useful both for assessing the degree of fish adaptability before their release into natural water basins and for prognoses of the percentage recapture of adult hatchery fish.
INTRODUCTION
At the present time many countries, including the Soviet Union, have turned to the artificial rearing of Atlantic salmon (Salmo salar L. ) . To realize the full potential, it is the task of scientists and fishery managers to develop methods of increasing the quality of reared salmon, to improve the system of fish release into natural waters, and to take measures to improve the spawning and rearing areas of salmon rivers (Netboy, 1969; Loftus, 1976; Harris, 1978; Brunet; 1980; Mills, 1980; Bakshtansky et al., 1981; Kazakov, 1982; Shustov, 1983; Enderlein, 1984; Vibert, 1984). It is known that the ecological conditions for hatchery-reared Atlantic salmon differ from natural ones. In rivers wild salmon live in the fastest rapids and shallows, constantly being affected by strong water currents of 0.3-0.8 m/s (Kalleberg, 1958; Keenleyside, 1962; Saunders and Gee, 1964; Mitans, 1975; Shustov et al., 1980). Hatchery-reared salmon parr are kept in devices such as concrete and plastic tanks, trout flumes and rearing ponds. The flow rates are generally lower than in a river. It is therefore understandable that the stamina of fishes reared in such different ecological conditions is also different.
0044-8486/88/$03.50
0 1988 Elsevier Science Publishers B.V.
82
We have found earlier that the rate of adaptation of hatchery-reared Atlantic salmon to river conditions depends on their stamina. If the fish are kept in hatchery tanks with a current speed of 0.4-0.6 m/s for 1.5 months, the swimming performance of such trained parr is twice that of normal hatchery fish (Shchurov et al., 1986a). On release, the trained fish were less subject to displacement by the current flow, were more successfully distributed in the fastest rapids and shallows and had better feeding rates (Shchurov et al., 1986b). Similar results were found for hatchery-reared brown trout, Salmo trutta L. (Cresswell and Williams, 1983). The present report is based on the results of our experiments carried out in August 1985 and July 1986 at the fish-rearing farms and in the rivers of the Kola peninsula in the northern U.S.S.R. The stamina of wild and hatcheryreared Atlantic salmon was determined by a method similar to that used by Nashimoto (1980) who studied the stamina of rainbow trout, Salmo gairdneri. This involves registering the maximum swimming forces developed by fish at the moment of their escape response from a strong stimulus, using a dynamometer. The method is simple, reliable and, with the use of SI units like the gram, it allows easy comparison with other workers’ results. The results of our studies are based on six series of experiments in which the stamina of 98 wild parr (age 2 + to 4 + ) and 189 hatchery-reared fish (age 2 + to 3 + ) was investigated. Since the swimming performance of fish (Pavlov, 1979 ) , including young Atlantic salmon (Rimmer et al., 1985 ), depends on the season and environmental temperature, this paper presents the results of experiments conducted only in mid-summer within a narrow range of water temperatures, 13-15 “C. METHODS
Wild salmon parr from the spawning rivers were caught in the fastest rapids and shallows at a depth of 0.7 m with a small fry net (mesh size 6 mm). The fish were immediately placed in plastic tanks filled with water, which were laid on the river bank near the device. Similar methods were used to catch hatchery-reared salmon parr from trout channels and rearing ponds. This procedure produced no traumatic effect on the fish, and the experiment could begin 0.51 h after the fish recovered. The device for registering fish swimming forces consisted of two parts: a 50cm-long plastic box with a water volume of 5 1 and a dynamometer with calibration up to 250 g. A thin fish line from the dynamometer lever was attached to the dorsal fin of a fish with a small clutch which exerted no traumatic effect on the fish. The fish escape response was provoked by two-three momentary electric stimuli from portable batteries, whose tension current was not more than 1 V/ cm of the device length, or by finger tapping on the device. The maximum
83
swimming force was registered by the maximum throw of the point of the dynamometer, and the fish length was measured before release. The experiment with each individual lasted for 20-30 s, and the measurement of the maximum force took 1-3 s. RESULTS
The results showed that the stamina of wild and hatchery young salmon depends mainly on their size (Figs. l-2; Table 1). The longer the fish is, the larger are the values of the swimming force recorded with the dynamometer. At the same time, both wild and hatchery salmon parr are characterized by a significant spread of individual data, so that different individuals of the same size may have stamina values which differ by a factor of two (Figs. 1, 2). For force(g)
Swimming
*
B
.
120
.*. .
i
-
c
t
.
100 -
eu
. .
IIr./
. .
l
”
”
l
60 -
y
.
_-
“.
.-
40
-0 t
l
. 20
Length km)
i13
$1
3
11
1n
11
12
13
z l’(
I
81
7
8
1
I
II
9
m
11
12
12
* *
e
3
I
10 11
II
12
I
13 74
Fig. 1. Stamina of young Atlantic salmon in river conditions. Abscissa - fish sizes (cm); ordinate - swimming force (g). Results of experiments A, B, C are given in Table 1.
E
/
DL-i-7
a
9
10 11
12
7
. e L. .. . . .
F
. a.. . . . -0. _. . b.
. l . *
3
IO
11 12
7
. /
. .. ./ . . .
l
.
/ . n
. l
. .
.
.
Length 8
3
10 11
12
(cm)
13
Fig. 2. Stamina of hatchery-reared young Atlantic salmon. Abscissa - fish sizes (cm); ordinate swimming force (g). Results of experiments D, E, F are given in Table 1.
Fish-rearing farms Taibolsky
Knjazhegubsky
Kandalkshsky
D
E
F
Kitsa
Umba
Rivers Pechenga
trout channel (0.05-0.1) trout channel (0.05-0.1) rearing pond (0.0)
smooth ridge (0.3-0.5) high rapid (0.8-1.5) ridge (0.3-0.5)
50 50
Y= -145+26.0X-0.689p Y= -20.3+2.91x+0.380x~ Y= -35.2+5.23X+O.l74p
0.867 0.924
hatchery hatchery
50
49
Y=47.3-
11.6X+ 1.15x
40
48
Number of fish in experiment
Y=19.7-8.95X3+1.27x2
Y=93.7-17.1X+1.3oX
Equation of regression, where: Y = fish length (cm) X=swimming force (g)
0.864
hatchery
0.869
0.844
wild hatchery fish 1 month after release
0.157
Coefficient of correlation between fish length and swimming force
August 1985 and July 1986)
wild
Origin of juveniles
salmon (Kola peninsula,
(flow
Ecological conditions rate, m/s)
Numbering of experiments (see Figs. 1,2)
Place of experiment
young Atlantic
Stamina of wild and hatchery-reared
TABLE 1
85
example, in the Pechenga river, wild fish 12 cm long had a minimum force of 50 g and a maximum force of 100 g (Fig. 1A). Hatchery-reared salmon parr grown in the trout channels of the Knjazhegubsky Fish-Rearing Farm whose length was 10 cm had a spread of data for swimming force from 30 to 60 g (Fig. 2E). As expected, the stamina of fish living in different ecological conditions differed considerably. Wild salmon parr from the Umba river caught in shallows with a swift current of 0.8-1.5 m/s were especially strong (Fig. 1B). Lower values for stamina were characteristic of wild and hatchery-reared salmon living in conditions with a current speed of 0.3-0.5 m/s (Fig. lA, C). Of all the hatchery fish, the weakest were those grown in rearing ponds where there was practically no current (Fig. 2F). If the stamina of wild young salmon is taken as the norm, then the fish originating from the ponds will be 1.5-2 times weaker than the ,wild fish. DISCUSSION
Similar results to ours were found by Green (1964)) using a test for swimming performance: wild young brook trout, Salmo truttczfario L., had greater swimming force than “domestic” fish. Similar data were obtained by Barns ( 1967) for young sockeye salmon, Oncorhynchus nerlza (W. ) . Hatchery-reared juveniles are adversely affected by sharp changes of conditions from the hatchery to the natural environment, especially because of stress during transport, and most of them die in the first few days after release (Kamyshnaya and Tsepkin, 1973; Bakshtansky et al., 1981). We have no reliable evidence on which individuals are most vulnerable. Individuals with low stamina are presumably not strong enough to resist the flow, cannot escape from predatory fish and birds, and cannot pursue food items and get sufficient amounts of drifting food. These possibilities are supported by our work on training hatchery salmon parr before their release into rivers (Shchurov et al., 1986a). We have found that the trained fish with higher stamina values adapt considerably more successfully to river habitats (Shchurov et al., 1986b). The general practice of salmon rearing shows that larger hatchery salmon stand a better chance of survival under natural conditions. Thus, Carlin (1968) found that increase in size of hatchery smolts led to a 2.3% per cm increase in the rate of fish return. This seems to be achieved only if high-stamina fish are released. There are several methods for increasing fish stamina in the conditions of fish-rearing farms. Thus Kol’gaev (1978) suggests growing salmon juveniles in long, narrow flumes providing an increase of the flow rate. Thorpe and Wankowski (1979) suggest substituting circular for radial flow in standard tanks. We think that training of fish is also required. Thus the 1.5-month training of hatchery Atlantic salmon parr resulted in a 2-fold increase of their swimming performance (Shchurov et al., 1986a).
86
REFERENCES Bakshtansky, E.L., Nesterov, V.D. and Chernitsky, A.G., 1981. Recommendations for release of young Atlantic salmon and sea trout. M., V.N.I.I. Mor. Ryb. Hoz-va i Okeanogr., 29 pp. (in Russian). Barns, R.A., 1967. Differences in performance of naturally and artificially propagated sockeye salmon migrant fry as measured with swimming and predation tests. J. Fish. Res. Board Can., 24 (5): 1117-1153. Brunet, A.R., 1980. Present status of the Atlantic salmon stocks in France and environmental constraints on their extension. In: A.E.J. Wont (Editor), Atlantic Salmon: its Future. Proc. 2nd Int. Atlantic Salmon Symp., Edinburgh, 1978. Fishing News Books, Farnham, pp. 128134. Carlin, B., 1968. Salmon tagging experiments. In: Atlantic Salmon Assoc. Centennial Award Fund. Series of Lectures. Montreal, Que., Canada, lecture 2, pp. 8-13. Cresswell, R.C. and Williams, R., 1983. Post-stocking movements and recapture of hatchery-reared trout released into flowing waters - effect of prior acclimation to flow. J. Fish Biol., 23 (3): 265-276. Enderlein, O., 1984. Stocking of fish in Sweden from the perspective of tagging. EIFAC Tech. Pap., 42, suppl. 1: 269-281. Green, D.M.I., 1964. A comparison of stamina of brook trout from wild and domestic parents. Trans. Am. Fish. Sot., 93 (1): 96-100. Harris, G.S., 1978. Salmon propagation. The final reports? Water (G.B.), 20: 7-8. Kalleberg, H., 1958. Observations in a stream tank of territoriality and competition in juvenile salmon and trout (Salmo salar L. and Salmo trutta L.). Rep. Inst. Freshwater Res., Drottningholm, 39: 55-98. Kamyshnaya, M.S. and Tsepkin, E.A., 1973. Materials on ecology of pike Esox lucius L. in the lower reaches of Umba river. Vopr. Ihtiol., 13 (6): 1105-1111 (in Russian). Kazakov, R.V., 1982. Biological bases for Atlantic salmon production. M., Legkaya i Pishchevaya promyshlennost, 144 pp. (in Russian). Keenleyside, M.N.A., 1962. Skin-diving observations of Atlantic salmon and brook trout in the Miramichi River, New Brunswick. J. Fish. Res. Board Can., 19 (4): 625-634. Kol’gaev, A.M., 1978. Some peculiarities in estimation of water supply of salmon-rearing farms. Ryb. Hoz-vo, 5: 44 (in Russian). Loftus, K.H., 1976. Science for Canada’s fisheries rehabilitation needs. J. Fish. Res. Board Can., 33 (8): 1822-1857. Mills, D.H., 1980. Scottish salmon rivers and their future management. In: A.E.J. Wont (Editor), Atlantic Salmon: its Future. Proc. 2nd Int. Atlantic Salmon Symp., Edinburgh, 1978. Fishing News Books, Farnham, pp. 70-81. Mitans, A.R., 1975. Efficiency of natural and artificial reproduction of Baltic sea salmon as the result of its freshwater period of life. In: Rybokhozyaistvennye Issledovaniya v Basseine Baltiiskogo Morya. No. 11. Zvaygzne Press, Riga, pp. 110-152 (in Russian). Nashimoto, K., 1980. The maximum swimming force of rainbow trout. Bull. Jpn. Sot. Sci. Fish., 46 (8): 949-954. Netboy, A., 1969. Salmon biology and problems of management - Can the salmon be saved? In: Atlantic Salmon Assoc., Centennial Award Fund. Series of Lectures. Montreal, Que., Canada, lecture 2, pp. 11-15. Pavlov, D.S., 1979. Fundamentals of biological control of fish behaviour in water stream. Nauka, Moscow, 319 pp. (in Russian). Rimmer, D.M., Saunders, R.L. and Paim, U., 1985. Effects of temperature and season on the position holding performance of juvenile Atlantic salmon (Salmo salar L.). Can. J. Zool., 63 (1): 92-96.
87 Saunders, R.L. and Gee, J.H., 1964. Movements of young Atlantic salmon in a small stream. J. Fish. Ree. Board Can., 21 (1): 27-36. Shchurov, I.L., Smirnov, Yu.A. and Shustov, Yu.A., 1986a. Period of adaptation for hatchery young sal.mon Salmo salar L. to river conditions after the improvement of fish stamina prior to the release of fish. 1. Possibility of training young fish in hatcheries. J. Ichthyol., 26 (2): 317-320 (in Russian), Shchurov, IL., Smirnov, Yu.A. and Shustov, Yu.A., 1986b. Period of adaptation for hatchery young salmon Salmo salar L. to river conditions after the improvement of fish stamina prior to the rel.ease of fish. 2. Behaviour and feeding of trained young Salmo salar L. in a river. J. Ichthyol., 26 (5): 871-874 (in Russian). Shustov, Yu.A., 1983. Ecology of young Atlantic salmon. Karelia, Petrozavodsk, 152 pp. (in Russian). Shustov, Yu.A., Shchurov, I.L. and Smirnov, Yu.A., 1980. Conditions of existence, behaviour and distribution of young Salmo salar in a river. J. Ichthyol., 20 (1): 119-123 (in Russian). Thorpe, J.R. and Wankowski, I.W.I., 1979. Feed presentation and food particle size for juvenile Atlantic salmon, Scdmo salur L. In: Finfish Nutrition and Fishfeed Technology. Proc. World Symp., Hamburg, 1978. Heenemann, Berlin, vol. 1, pp. 501-513. Vibert, R., 1984. Les saumons: espece manatee ou d’avenir? Peche Mar., 63 (1277): 444-449.