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Evidence for appetite rhythms in Atlantic salmon (Salmo salar L.)
Abstracts /Aquaculture 124 (1994) 359-363
363
performance was compared with that of fish fed JSM. In the coho salmon study, the lowest value for apparent protein digestibility (APD) was found with fish fed the indirectly dried ordinary meal of horse mackerel, and the highest APD value was achieved by fish fed JSM. APD values of about 80% were observed for fish fed the other Chilean fish meals either dried directly or indirectly. The protein digestibility (PD) of 5 out of 6 fish meals determined in rainbow trout were about 90% and the drying method made no apparent difference in PD. There was no appreciable relationship between PD and growth of fish because of their high PD. However, growth rate and feed efficiency were lowest in fish fed the anchovy meal dried directly, coinciding with its low PD, but the PD of the other 4 fish meals were almost the same value (90%) in spite of different growth performances by fish fed these meals. For evaluation of fish meal quality, determination of protein digestibility may be important even though we could not detect any clear difference in PD of the fish meals made by various drying methods. Thus, growth tests for comparison of the quality of fish meal having a similar PD value may be essential. Also we failed to find any obvious difference in amino acid digestibility of the fish meals which resulted in the highest and intermediate growth performances.
Evidence for appetite rhythms in Atlantic salmon (Salmo salar L. ) John E. Thorpe SOAFD Freshwater Fisheries Laboratory, Pitlochty, PHI6
5L& UK
Annual and die1 appetite and feeding rhythms occur in Atlantic salmon, both in fresh water and in the sea. Direct evidence has been obtained for die1 rhythms, in both fresh and sea water over much of the year, and evidence for annual rhythms is both direct and indirect (inferred from annual growth rhythms). Peak appetite in freshwater in early summer has probably evolved in response to peak availability of appropriate insect prey at that time. Minimal appetite (anorexia) occurs between September and March in the non-smolting fraction in fresh water. Such adaptive annual patterns are unlikely to be modified easily in culture. By contrast, die1 rhythms in sea water vary considerably from month to month, and apparently from site to site, suggesting complex external control of these patterns, and opportunistic responses from the fish. Consequently, it is probable that die1 feeding rhythms can be manipulated to suit the convenience of the cultivator, but the relative efficiency of feeding under different regimes needs testing.
363
performance was compared with that of fish fed JSM. In the coho salmon study, the lowest value for apparent protein digestibility (APD) was found with fish fed the indirectly dried ordinary meal of horse mackerel, and the highest APD value was achieved by fish fed JSM. APD values of about 80% were observed for fish fed the other Chilean fish meals either dried directly or indirectly. The protein digestibility (PD) of 5 out of 6 fish meals determined in rainbow trout were about 90% and the drying method made no apparent difference in PD. There was no appreciable relationship between PD and growth of fish because of their high PD. However, growth rate and feed efficiency were lowest in fish fed the anchovy meal dried directly, coinciding with its low PD, but the PD of the other 4 fish meals were almost the same value (90%) in spite of different growth performances by fish fed these meals. For evaluation of fish meal quality, determination of protein digestibility may be important even though we could not detect any clear difference in PD of the fish meals made by various drying methods. Thus, growth tests for comparison of the quality of fish meal having a similar PD value may be essential. Also we failed to find any obvious difference in amino acid digestibility of the fish meals which resulted in the highest and intermediate growth performances.
Evidence for appetite rhythms in Atlantic salmon (Salmo salar L. ) John E. Thorpe SOAFD Freshwater Fisheries Laboratory, Pitlochty, PHI6
5L& UK
Annual and die1 appetite and feeding rhythms occur in Atlantic salmon, both in fresh water and in the sea. Direct evidence has been obtained for die1 rhythms, in both fresh and sea water over much of the year, and evidence for annual rhythms is both direct and indirect (inferred from annual growth rhythms). Peak appetite in freshwater in early summer has probably evolved in response to peak availability of appropriate insect prey at that time. Minimal appetite (anorexia) occurs between September and March in the non-smolting fraction in fresh water. Such adaptive annual patterns are unlikely to be modified easily in culture. By contrast, die1 rhythms in sea water vary considerably from month to month, and apparently from site to site, suggesting complex external control of these patterns, and opportunistic responses from the fish. Consequently, it is probable that die1 feeding rhythms can be manipulated to suit the convenience of the cultivator, but the relative efficiency of feeding under different regimes needs testing.