Gulf of Alaska | Fishes and Fish Habitats
Consequences of variation in body size, condition, physiological state, and in-river conditions for spawning migration success by Alaskan salmon: A three-year telemetry study of Copper River sockeye Presenter: Kristen Gorman , kbgorman@alaska.edu, University of Alaska Fairbanks Pete Rand , prand@pwssc.org, Prince William Sound Science Center Karia Kaukinen , Karia.Kaukinen@dfo-mpo.gc.ca, Department of Fisheries and Oceans Canada Nearly all species of Pacific salmon ( Oncorhynchus spp. ) in Alaska have been returning to spawn at smaller body sizes in recent years. Studies suggest that the combined effects of a changing ocean climate and competition at-sea due to higher salmon abundance are key factors influencing the body size of adult Pacific salmon at return. Environmental conditions are also changing within freshwater systems, creating more variable and challenging migratory conditions for returning salmon. We present results from a three-year radio telemetry study (including NPRB project 1902) that evaluated potential biological and environmental factors shaping spawning migration success by sockeye salmon of the Copper River, in southcentral Alaska – a highly glaciated watershed that supports commercial, subsistence, and personal- use sockeye fisheries. Over three field seasons (2019-2021), we radio tagged over 800 adult sockeye salmon in the lower Copper River and evaluated the effects of body size and condition, transcriptomic response, and pathogen diversity and loads on migration success. We detected a positive relationship across all years between sockeye body size and energy density and the likelihood of successful passage through Wood Canyon, suggesting that long-term declines in sockeye body size and energetic condition may translate into lower migratory success in-river. During 2019, air temperatures were very high, and accelerated glacial melting resulted in a high rate of water discharge. Preliminary analysis suggests that Sockeye radio tagged during 2019 had elevated transcriptomic responses for hypoxia stress (possibly resulting from physical exertion), viral disease development (apparently associated with Infectious Hematopoietic Necrosis Virus, IHNV, infection), a lower elevated transcriptomic response for thermal stress, and a low rate of passage through Wood Canyon. Several pathogens detected in our study are known to be associated with premature mortality in other salmon systems. We hypothesize that migration could be impeded and enroute mortality possibly elevated in years with high rates of glacial melting, causing greater stress and potential for disease in migratory salmon. Understanding the interplay of how ocean and in-river conditions are simultaneously affecting salmon fitness is important for future management of this fishery and others that experience significant glacial input. Tobi Ming , Tobi.Ming@dfo-mpo.gc.ca, Department of Fisheries and Oceans Canada Shaorong Li , Shaorong.Li@dfo-mpo.gc.ca, Department of Fisheries and Oceans Canada Kristi Miller , Kristi.Saunders@dfo-mpo.gc.ca, Department of Fisheries and Oceans Canada
Alaska Marine Science Symposium 2023 18
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