UBC Theses and Dissertations
Thermal behaviour, survival, and reproductive success of adult Gates Creek sockeye salmon (Oncorhynchus nerka) Minke-Martin, Vanessa
Water temperature affects every aspect of the physiology of ectothermic fishes. Heterothermic stenotherms, like Pacific salmon, use behavioural thermoregulation to swim into more optimal water temperatures and out of less optimal ones. The range of preferred temperatures can coincide with the thermal optima of important physiological processes. During the reproductive migration, adult Pacific salmon partition limited endogenous energy and aerobic scope for activity to multiple activities, including swimming, recovery from physiological stress, maturation, and immune function. Although much is known about the effect of temperature on aspects of salmonid physiology from laboratory experiments, how free-swimming fish use thermal habitats to manipulate physiological processes is not well understood. Radio telemetry, archival temperature loggers, blood biopsy, and spawning assessments were used to evaluate the relative importance of physiology and migratory experience to thermal behaviour and metrics of fitness in the Gates Creek population of sockeye salmon in the Fraser River, British Columbia. A framework was developed, using relationships between temperature and routine oxygen consumption and aerobic scope for activity, to determine whether the thermal experience of tagged fish reflected minimization of energetic cost or maximization of aerobic scope. Nearly all male and female fish preferred temperatures several degrees below the optimum for aerobic scope (ToptAS; i.e. 16.4 ºC), but two groups of fish benefitted from use of temperatures near ToptAS. Later migrants used these temperatures, where the cost of transport is minimized, to swim quickly through one lake, and female sockeye salmon that spent a greater proportion of the migration within a ToptAS window (13.4-19.5 ºC) lived longer on spawning grounds and had a lower probability of egg retention at death. In contrast, migrants that spent longer in the lakes occupied the cool water temperatures that I hypothesized would limit energy expenditure. Temperature preference was also related to the flow dynamics and water temperature that fish experienced during passage at the Seton Dam, which suggests that migrants use thermal habitats for recovery from anaerobic swimming. Future research can use existing relationships between temperature and physiological processes for greater insight into the ecological importance of fish temperature selection in thermally heterogeneous environments.
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