Riverscape scale analysis of fish/habitat relationships

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To successfully complete their life-cycle, fish need to access different habitats whose characteristics fulfill the requirements associated to specific life functions or life stages. The term riverscape describes the mosaic of physical habitats comprised within a river system. As such, the riverscape constitutes the physical template available for fish to realize their life-cycle. My long-term research program is structured around the hypothesis that the nature and spatial structure of habitats found within riverscapes play a fundamental role on the dynamics of stream fish populations. ***In a recent study conducted in my laboratory, telemetry tracking of adult Atlantic salmon in the Sainte-Marguerite river (Québec) using temperature sensing acoustic tags revealed the crucial role of deep pool-bottom thermal refuges for the thermoregulation of adult salmon during warm water episodes (Frechette et al, submitted). ***Despite these observations, several important questions remain to be elucidated concerning the dynamics of pool-bottom thermal refuges (How common are they? What are the processes responsible for their presence and dynamics? Is it possible to predict their occurrence from pool characteristics?) and their biological significance for salmon (How widespread is this thermoregulation behaviour? Is the water temperature triggering thermoregulation behavior constant across rivers or is local adaptation to warm temperatures observed? What is the role of pool thermal refuge location on the movement patterns of adult salmon in rivers?).***Taking Atlantic salmon (Salmo salar) as an ecological model, the general scientific approach of the proposed research is mainly based on the quantitative analysis of empirical field data. In the first project, detailed field measurements of river pool physical characteristics will be conducted in pools of various river systems to decipher the processes leading to thermal refuge presence and develop predictive models of pool-bottom thermal refuge formation, persistence and dismantling. In the second project, snorkeling counts and acoustic telemetry tracking of adult Atlantic salmon with temperature sensing tags and dense arrays of hydrophones will be used to 1) monitor large-scale movement of fish in relation to pool-bottom thermal refuge locations and river temperature, and 2) document the fine-scale spatial and temporal use of refuges. ***In the currently observed context of climate change, understanding the dynamics and role of pool-bottom thermal refuges appears critical to the management of salmon population. The proposed research will provide stream ecologist and stream managers with highly novel tools and information concerning the dynamics of riverine ecosystems that will help assess, predict and mitigate the impact of anthropogenic disturbances and climate change on river ecosystems.