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Hydroacoustics describe the role of food web structure as a modifier of Lake Trout (Salvelinus namaycush) activity
Activity is a substantial energetic cost in bioenergetic models of fish growth. However, generating accurate estimates of activity in wild, free-swimming fish is still a major challenge because of the logistical and technical constraints of acquiring these data. Using a novel stationary and up-looking hydroacoustic method across lakes ranging in food web complexity, I demonstrate that a coarse consideration of pelagic food web structure successfully predicts lake trout activity metrics (i.e., swimming speed and path), active metabolic costs, and exposure to stressful habitats. The methodological approach presented here provides a way forward for quantifying in situ fine-scale behaviour of free-swimming fish, while the results provide useful context to the life history and management of a cold-water predator facing an uncertain future in warming and more productive environments.