Some effects of acclimation, acute temperature experience, and size, on the sustained swimming speed of juvenile Coho salmon (Oncorhynchus kisutch)
Date
1969
Authors
Griffiths, John Stephen
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Abstract
Swimming speeds of coho salmon juveniles have been investigated with respect to acclimation temperature and acute (test) temperature experience. Sustained swimming speed were approximated in terms of critical swimming speeds; the latter is related to the time to fatigue in samples of fish exposed to incremental increases in water velocity in an experimental water tunnel. Three series of tests were conducted between September, 1968 and May, 1969 on coho ranging between approximately 7½ and 9½ cm. total length.
Regression relations between critical velocities and acclimation and test temperatures were developed by response surface analysis using a non-linear second degree polynomial as a model.
Maximum performance (5.8 lengths/second) occurred at acclimation and test temperatures near 20° C. At lower acclimation temperatures, maximal performance was found at temperatures greater than those of acclimation, defining a ridge of near-maximal performance. Thus, maximal performance over a range of test temperatures is not necessarily found at a test temperature equal to that of acclimation. In addition, maximum performance over a range of acclimation temperatures is not necessarily found at an acclimation temperature equal to that of testing. This lack of correspondence over the performance surface changes progressively, attenuating at acclimation and test temperatures in the vicinity of 20° C.
Seasonal differences in performance were observed, although not clearly defined. These involved a change in the shape of the performance surface. In addition, a dependence of swimming performance on size was recognized, although the relation could not be defined quantitatively.
Comparison of performance of the coho with that of the sockeye salmon juveniles suggested that the former may be better equipped to perform in warm environments.
A hypothesis is advanced suggesting that a relation, in terms of temperature, may exist between the performance optimum, those for metabolic scope and growth on excess rations, and for the final temperature preferendum.