Grant: Discovery Grants Program - Individual

Water temperature is a strong predictor of the biogeographical distribution of fish. The current trend of warming of thermal regimes implies higher summer maximum temperatures, higher frequency and magnitude of warm temperature events, and decreased local thermal heterogeneity. When cold-water refuges are accessible, fish deal with thermal stress by moving to these alternative habitats for behavioural thermoregulation. However, the temperature that triggers displacement to cold-water refuges for behavioural thermoregulation is not static, and decreases with the frequency of warm temperature events. Moreover, social dynamics may influence populations' ability to shift to more favourable habitats in response to warming temperatures, through effects on individual stress levels. Thus, there is an increasing need to integrate knowledge about the physiological and behavioural responses of fish to current and projected temperature regimes to better predict the resilience of fish populations in a warming world. I will use Atlantic salmon (Salmo salar), three-spine stickleback (Gasterosteus aculeatus), and brook trout (Salvelinus fontinalis) to address fundamental knowledge gaps in our understanding of the abiotic and biotic drivers shaping within- and among-individual variation in thermal tolerance of fish, in the context of warming aquatic environments. As such, my team will focus on two fundamental research objectives investigating the effects of chronic and acute exposures to temperature fluctuations (Objective 1) and social dynamics (Objective 2) on individual thermal tolerance. For the first objective, my team will conduct experiments on juvenile Atlantic salmon to quantify the thermal tolerance traits of fish, mainly the critical thermal maximum (CTmax) and the agitation temperature (Tag), in thermal conditions reflecting current and projected natural temperature regimes, including daily fluctuations in temperature and warm temperature events. These experiments will inform on the ecological relevance of different thermal tolerance traits and on the current thermal safety margins of wild Atlantic salmon in Québec rivers. For the second objective, my team will conduct experiments on three-spine stickleback to assess how the social context may interact with the acclimation temperature regime to influence variation in thermal tolerance traits. My team will also investigate if individual behavioural phenotypes could covary with thermal tolerance and explain distinct life history trajectories in brook trout (i.e. resident or migrant ecotype). The studies proposed in this research program will contribute to bridging the gap between laboratory findings and ecological applications to better inform conservation efforts of fish populations in warming aquatic environments.