Thermal ecology of freshwater fishes: the effects of variability in water temperature

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Water temperature is a major environmental factor affecting the physiology and ecology of freshwater fishes a group of organisms that are economically, culturally and ecologically important in Canada and beyond. The long-term objective of my research program is to elucidate how water temperature and its interaction with other abiotic and biotic factors influence the organismal (behaviour, survival and reproduction) and population (abundance and distribution) ecology of freshwater fishes. Recently, it has become clear that to fully understand how temperature influences the ecology of freshwater fishes (and any other organism) it is necessary to investigate their responses to variability in ambient temperature. Therefore, over the next five years, my objective is to characterize the spatio-temporal variability in temperature of freshwater environments and determine the ecological responses of freshwater fishes to that variability. To address this short-term objective, I propose four projects that will focus on the Fraser River watershed (British Columbia) and will use adult salmonids (sockeye salmon, bull trout and rainbow trout) as model species. Project 1 will use historical water temperature data (collected since 1950) and spectral analyses to quantify spatio-temporal variability in water temperature in the Fraser River watershed and assess the potential consequences of changes in variability patterns for adult migrating sockeye salmon. Project 2 will use the historical water temperature data and existing radio-telemetry data on adult migrating sockeye salmon (~3,250 fish since 2002) to test the hypothesis that variable thermal conditions encountered during migration have a greater impact on survival of individuals from populations that exhibit narrow curves of cardiorespiratory capacity by temperature. Project 3 will use field and laboratory experiments on sockeye salmon to test the hypothesis that how effectively an individual thermoregulates depends on its internal state (e.g. reproductive maturation, pathogen load, available somatic energy). The project will also test the hypothesis that effective thermoregulation enhances reproductive success. Project 4 will use field and laboratory experiments on bull trout and rainbow trout to investigate the relationship between water temperature and activity and test the hypothesis that the energetic costs of behavioural thermoregulation are minimized in more heterogeneous thermal habitats. These projects will improve our knowledge on and predictive capacity of the responses of freshwater fishes to temperature and will inform their management and conservation in a warming and more thermally variable world. The projects will also train a new generation of HQP (5 UG, 3 MSc, 1 PhD) and equip them with the knowledge and skills needed to further advance research and conservation of freshwater fishes in Canada.