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Survival and growth rates of whitefish (Coregonus lavaretus L.) larvae after experimentally delayed hatching
51 (1986)
Aquaculture, Elsevier
Science
207-210
Publishers
B.V.,
207 Amsterdam
-
Printed
in The Netherlands
SURVIVAL AND GROWTH RATES OF WHITEFISH (COREGONUS LAVARETUS L.) LARVAE AFTER EXPERIMENTALLY DELAYED HATCHING
R. KOLMAN’
and M. LUCZYNSKIZ,’
’ Inland Fisheries Institute (ZFI), 1 O-957 Olsztyn-Kortowo (Poland) ’ Department of Basic Fishery Sciences, Academy of Agriculture and Technology, Olsztyn-Kortowo, Bl.. 37 (Poland) ’ To whom all correspondence should (Accepted
27 October
1 O-957
be addressed.
1985)
ABSTRACT Kolman,
R. and Luczynski,
M.,
1986.
lauaretus L.) larvae after experimentally
Survival and growth rates of whitefish (Coregonus delayed hatching. Aquaculture, 51: 207-210.
The time of hatching of whitefish (Coregonus Zauaretus) embryos was artificially delayed so that it coincided with suitable thermal and food conditions in stocked lakes. By cooling the hatchery water to l-2”C, successive batches of whitefish embryos were obtained on 21 and 28 April and 7 May. Then the batches of larvae were reared in tanks for 15 days at a constant temperature of 14.0 i O.l”C. Survival of the corresponding batches of fish during the whole rearing period was 89, 88, and 86%, respectively. Mean instantaneous rate of net biomass gain of the successive batches of fish was 11.71, 10.78, and 11.27% day-‘. Thus, delaying hatching time did not reduce either survival or growth rate of whitefish larvae.
INTRODUCTION
To improve the effectiveness of stocking lakes with vendace (Coregonus albulu) larvae, a technique for delaying egg hatching was developed (Luczynski, 1984). Hatching can be delayed by cooling the circulation water in the hatchery (to 1 or 2°C) until the beginning of May, when lake conditions are optimal for stocking. It has been proved that delaying hatching time until May does not reduce either survival or growth rate of vendace larvae (Luczynski and Kolman, 1985). The present trial was designed to check whether delaying hatching of whitefish (Coregonus luuaretus) embryos influences their survival and growth rate. As mass hatching of whitefish embryos usually occurs about one week later than in vendace (Luczynski, 1986) the first (control) batch of embryos was hatched correspondingly later than in the case of vendace (Luczynski and Kolman, 1985).
0044-8486/86/$03.50
o 1986
Elsevier
Science
Publishers
B.V.
208 MATERIALS
AND METHODS
On 15 March, eggs of C. luuaretus were taken from a commercial coregonid hatchery and incubated in the laboratory of IF1 in Olsztyn at a mean temperature of 1.5%. Water thermoregulation, the chemical characteristics of the water, and egg hatching procedure were identical to those described for the C. albula experiment (Luczynski and Kolman, 1985). On 21 April, when mass hatching of whitefish eggs in the commercial hatchery began, three batches of 50 laboratory-incubated eggs were acclimated to 10°C and hatched. This was repeated on 28 April and 7 May with further triplicate egg samples (Table 1). All embryos hatching from a given batch of eggs were placed into a 5-l chamber and reared for 15 days. Fish were fed ad libitum with sieved zooplankton, collected from different small water bodies. The day on which ingested food was seen in the guts of 50% or more larvae was considered as day 0 of the given triplicate rearing trial. Detailed descriptions of water supply, thermoregulation, etc. are given in our previous paper (Luczynski and Kolman, 1985). After the rearing trial, all fish were removed from the test chambers in the morning, fasted for an additional 6 h, then killed, preserved in Lam-Roff solution (Dabrowski and Bardega, 1982), counted, weighed (* 0.1 mg) and measured (? 0.01 mm). Instantaneous rates of growth, mortality and net biomass gain were calculated between day 0 and day 15 on a percentage day- ’ basis (Ricker, 1958). Net biomass gain is the weight gained by all members of a test batch minus weight loss incurred through mortality within the batch. Triplicate batches differing in hatching delay were treated together as single groups in calculating the above parameters. RESULTS
AND DISCUSSION
Newly hatched embryos were 12.05 + 0.59 mm in body length, 12.47 f 0.55 mm in total length, and 5.9 mg mean wet weight. Rates of survival and of growth in length and in weight of reared fish were similar in all batches differing in hatching delay (Table 1). Small differences in growth rate were not correlated with hatching delay, and they resulted mainly from differences in the quality of food supplied to the larvae (the source of zooplankton had to be changed several times). Also, due to the periodic chlorination of the city water, we had to change several times to lake water, in which higher levels of total ammonia (up to 0.3 mg 1-l) were observed. After 15 days of rearing, whitefish larvae achieved a mean total length of 20.86 to 21.39 mm (Table 1). Apparently, at this size, Coregoninae larvae pass through a so-called “metamorphosis” (Fliichter, 1980), becoming juveniles (Balon, 1975). Thus, in our trial, we have compared the growth and the survival of whitefish in the period between hatching and the juvenile
209 TABLE
I
Survival and growth of C. lauaretus larvae delayed in hatching for 0 (control), 7, and 16 days, as measured after 15 days of rearing at 14.0 ? O.l”C. Data are given as the mean values of the triplicate test chambers (standard deviation in brackets) Date of hatching
Days of hatching
Survival and mean size of larvae after 15 days of rearing at 14°C
Mean net biomass gain (% day-‘)
delay Survival (%)
21 April 28 April 7May
0 7 16
89 88 86
Body length
Total length
(mm)
(mm)
18.95 19.08 19.21
(1.82) (1.28) (1.25)
20.86 21.13 21.39
Wet weight (mg)
(1.85) (1.51) (1.41)
38.4 33.8 37.2
(13.46) ( 8.63) ( 9.30)
11.71 10.78 11.27
stage, which is the most important interval in ontogeny from the viewpoint of the effectiveness of a whitefish stocking program. Whitefish larvae reared at 14.O”C grew very fast - their net rates of biomass gain (about 11% day- ‘, Table 1) closely resembled the maximum instantaneous net biomass gain of Coregonus artedii, which amounted to of 15.6% (McCormick et al., 1971). This 11.11% day-’ at a temperature could suggest that 14.O”C was quite close to the temperature for maximal growth of C. lavaretus larvae. Also, in this case, differences in net rates of biomass gain were not correlated with hatching delay. In conclusion, delaying the hatching time from April till May does not change either the survival or the growth rate of young Coregonus lavare tus during their larval phase. ACKNOWLEDGEMENTS
The investigation Poland.
was financed
by the Inland Fisheries Institute,
Olsztyn,
REFERENCES Balon, E.K., 1975. Terminology of intervals in fish development. J. Fish. Res. Board Can., 32: 1663-1670. Dabrowski, K. and Bardega, R., 1982. The changes of fish larvae dimensions due to fixation in different preservatives; Zool. Jahrb. Anat., 108: 509-516. Fliichter, J., 1980. Review of the present knowledge of rearing whitefish (Coregonidae) larvae. Aquaculture, 19: 191-208. Luczynski, M., 1984. A technique for delaying embryogenesis of vendace (Coregonus albula L.) eggs in order to synchronize mass hatching with optimal conditions for lake stocking. Aquaculture, 41: 113-117. Luczynski, M,, 1986. Review on the biology, exploitation, rearing and management of coregonid fishes in Poland. Arch. Hydrobiol. (in press).
210 Luczynski, M. and Kolman, R., 1985. Survival and growth rates of vendace (Coregonus albula L.) larvae after experimentally delayed hatching. Aquaculture, 50: 13-21. McCormick, J.H., Jones, B.R. and Syrett, R.F., 1971. Temperature requirements for growth and survival of larval ciscos (Coregonus artedii). J. Fish. Res. Board Can., 28: 924-927. Ricker, W.E., 1958. Handbook of computations for biological statistics of fish populations. Fish. Res. Board Can. Bull., No. 119, 300 pp.
Aquaculture, Elsevier
Science
207-210
Publishers
B.V.,
207 Amsterdam
-
Printed
in The Netherlands
SURVIVAL AND GROWTH RATES OF WHITEFISH (COREGONUS LAVARETUS L.) LARVAE AFTER EXPERIMENTALLY DELAYED HATCHING
R. KOLMAN’
and M. LUCZYNSKIZ,’
’ Inland Fisheries Institute (ZFI), 1 O-957 Olsztyn-Kortowo (Poland) ’ Department of Basic Fishery Sciences, Academy of Agriculture and Technology, Olsztyn-Kortowo, Bl.. 37 (Poland) ’ To whom all correspondence should (Accepted
27 October
1 O-957
be addressed.
1985)
ABSTRACT Kolman,
R. and Luczynski,
M.,
1986.
lauaretus L.) larvae after experimentally
Survival and growth rates of whitefish (Coregonus delayed hatching. Aquaculture, 51: 207-210.
The time of hatching of whitefish (Coregonus Zauaretus) embryos was artificially delayed so that it coincided with suitable thermal and food conditions in stocked lakes. By cooling the hatchery water to l-2”C, successive batches of whitefish embryos were obtained on 21 and 28 April and 7 May. Then the batches of larvae were reared in tanks for 15 days at a constant temperature of 14.0 i O.l”C. Survival of the corresponding batches of fish during the whole rearing period was 89, 88, and 86%, respectively. Mean instantaneous rate of net biomass gain of the successive batches of fish was 11.71, 10.78, and 11.27% day-‘. Thus, delaying hatching time did not reduce either survival or growth rate of whitefish larvae.
INTRODUCTION
To improve the effectiveness of stocking lakes with vendace (Coregonus albulu) larvae, a technique for delaying egg hatching was developed (Luczynski, 1984). Hatching can be delayed by cooling the circulation water in the hatchery (to 1 or 2°C) until the beginning of May, when lake conditions are optimal for stocking. It has been proved that delaying hatching time until May does not reduce either survival or growth rate of vendace larvae (Luczynski and Kolman, 1985). The present trial was designed to check whether delaying hatching of whitefish (Coregonus luuaretus) embryos influences their survival and growth rate. As mass hatching of whitefish embryos usually occurs about one week later than in vendace (Luczynski, 1986) the first (control) batch of embryos was hatched correspondingly later than in the case of vendace (Luczynski and Kolman, 1985).
0044-8486/86/$03.50
o 1986
Elsevier
Science
Publishers
B.V.
208 MATERIALS
AND METHODS
On 15 March, eggs of C. luuaretus were taken from a commercial coregonid hatchery and incubated in the laboratory of IF1 in Olsztyn at a mean temperature of 1.5%. Water thermoregulation, the chemical characteristics of the water, and egg hatching procedure were identical to those described for the C. albula experiment (Luczynski and Kolman, 1985). On 21 April, when mass hatching of whitefish eggs in the commercial hatchery began, three batches of 50 laboratory-incubated eggs were acclimated to 10°C and hatched. This was repeated on 28 April and 7 May with further triplicate egg samples (Table 1). All embryos hatching from a given batch of eggs were placed into a 5-l chamber and reared for 15 days. Fish were fed ad libitum with sieved zooplankton, collected from different small water bodies. The day on which ingested food was seen in the guts of 50% or more larvae was considered as day 0 of the given triplicate rearing trial. Detailed descriptions of water supply, thermoregulation, etc. are given in our previous paper (Luczynski and Kolman, 1985). After the rearing trial, all fish were removed from the test chambers in the morning, fasted for an additional 6 h, then killed, preserved in Lam-Roff solution (Dabrowski and Bardega, 1982), counted, weighed (* 0.1 mg) and measured (? 0.01 mm). Instantaneous rates of growth, mortality and net biomass gain were calculated between day 0 and day 15 on a percentage day- ’ basis (Ricker, 1958). Net biomass gain is the weight gained by all members of a test batch minus weight loss incurred through mortality within the batch. Triplicate batches differing in hatching delay were treated together as single groups in calculating the above parameters. RESULTS
AND DISCUSSION
Newly hatched embryos were 12.05 + 0.59 mm in body length, 12.47 f 0.55 mm in total length, and 5.9 mg mean wet weight. Rates of survival and of growth in length and in weight of reared fish were similar in all batches differing in hatching delay (Table 1). Small differences in growth rate were not correlated with hatching delay, and they resulted mainly from differences in the quality of food supplied to the larvae (the source of zooplankton had to be changed several times). Also, due to the periodic chlorination of the city water, we had to change several times to lake water, in which higher levels of total ammonia (up to 0.3 mg 1-l) were observed. After 15 days of rearing, whitefish larvae achieved a mean total length of 20.86 to 21.39 mm (Table 1). Apparently, at this size, Coregoninae larvae pass through a so-called “metamorphosis” (Fliichter, 1980), becoming juveniles (Balon, 1975). Thus, in our trial, we have compared the growth and the survival of whitefish in the period between hatching and the juvenile
209 TABLE
I
Survival and growth of C. lauaretus larvae delayed in hatching for 0 (control), 7, and 16 days, as measured after 15 days of rearing at 14.0 ? O.l”C. Data are given as the mean values of the triplicate test chambers (standard deviation in brackets) Date of hatching
Days of hatching
Survival and mean size of larvae after 15 days of rearing at 14°C
Mean net biomass gain (% day-‘)
delay Survival (%)
21 April 28 April 7May
0 7 16
89 88 86
Body length
Total length
(mm)
(mm)
18.95 19.08 19.21
(1.82) (1.28) (1.25)
20.86 21.13 21.39
Wet weight (mg)
(1.85) (1.51) (1.41)
38.4 33.8 37.2
(13.46) ( 8.63) ( 9.30)
11.71 10.78 11.27
stage, which is the most important interval in ontogeny from the viewpoint of the effectiveness of a whitefish stocking program. Whitefish larvae reared at 14.O”C grew very fast - their net rates of biomass gain (about 11% day- ‘, Table 1) closely resembled the maximum instantaneous net biomass gain of Coregonus artedii, which amounted to of 15.6% (McCormick et al., 1971). This 11.11% day-’ at a temperature could suggest that 14.O”C was quite close to the temperature for maximal growth of C. lavaretus larvae. Also, in this case, differences in net rates of biomass gain were not correlated with hatching delay. In conclusion, delaying the hatching time from April till May does not change either the survival or the growth rate of young Coregonus lavare tus during their larval phase. ACKNOWLEDGEMENTS
The investigation Poland.
was financed
by the Inland Fisheries Institute,
Olsztyn,
REFERENCES Balon, E.K., 1975. Terminology of intervals in fish development. J. Fish. Res. Board Can., 32: 1663-1670. Dabrowski, K. and Bardega, R., 1982. The changes of fish larvae dimensions due to fixation in different preservatives; Zool. Jahrb. Anat., 108: 509-516. Fliichter, J., 1980. Review of the present knowledge of rearing whitefish (Coregonidae) larvae. Aquaculture, 19: 191-208. Luczynski, M., 1984. A technique for delaying embryogenesis of vendace (Coregonus albula L.) eggs in order to synchronize mass hatching with optimal conditions for lake stocking. Aquaculture, 41: 113-117. Luczynski, M,, 1986. Review on the biology, exploitation, rearing and management of coregonid fishes in Poland. Arch. Hydrobiol. (in press).
210 Luczynski, M. and Kolman, R., 1985. Survival and growth rates of vendace (Coregonus albula L.) larvae after experimentally delayed hatching. Aquaculture, 50: 13-21. McCormick, J.H., Jones, B.R. and Syrett, R.F., 1971. Temperature requirements for growth and survival of larval ciscos (Coregonus artedii). J. Fish. Res. Board Can., 28: 924-927. Ricker, W.E., 1958. Handbook of computations for biological statistics of fish populations. Fish. Res. Board Can. Bull., No. 119, 300 pp.