Effects of injury, pathogens and climate warming on migration and spawning success of Pacific salmon that have escaped from fishing gear

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Abundant and sustainable Pacific salmon stocks are important economically, culturally, ecologically and politically to Canada. Most Pacific salmon are now encountering warmer rivers during spawning migration. Riverine harvest methods result in 'escapees' (e.g., fish that escape from nets) whose chance of survival is reduced in warm freshwater. Fish often escape from the dominant in-river fishing gears, beach seines and gillnets. In some years in the Fraser River, a remarkable 30-60% of sockeye sampled from spawning grounds suffer skin damage consistent with having struggled free of a net. Escaping from nets causes injury, stress and pathogen development which can lead to disease and mortality during the migration and while spawning but this has never been directly assessed with adult Pacific salmon. Without the empirical studies we propose, it is difficult to predict interactive effects of fishing approach, initial pathogen state, initial physiological condition, escape related injury, stress, disease development, and warming temperatures on migration and spawning success. Our objective is to broaden our understanding of migrating and spawning adult salmon physiology and disease in wild populations of Fraser River sockeye salmon experiencing climate warming and to provide resource managers and stakeholders with knowledge to guide adaptation strategies. To achieve this, we will combine rigorous natural science experimentation with targeted social science surveys given our recognition that the fisheries in the Fraser River represent coupled socio-ecological systems. These integrated studies will collectively provide the evidence base needed to support decision-making and ensure that the science generated is mobilized in an effective manner. Our work will directly benefit our partners (Fisheries and Oceans Canada, the Pacific Salmon Commission, and the Pacific Salmon Foundation) who manage the salmon resource on behalf of Canadians. Our research results can lead to rapid changes in harvest policy, which will have significant and positive economic and environmental consequences.******