17 May
Dave Beauchamp
Associate Professor, UW Aquatic & Fishery Sciences/Washington Cooperative Fish & Wildlife Research Unit
Interannual variation in energetics, growth, and survival of pink salmon in the Gulf of Alaska: responses to climate change
Abstract
Marine survival is positively correlated to size and growth rate during juvenile and subsequent life stages of salmon, but a mechanistic understanding of the processes that regulate growth and survival has been elusive. Growth can change in response to thermal regime, food availability, food quality, and activity, but determining which of these factors exert the most influence has been challenging. Climate can influence the quantity and quality of food available for salmon at various seasons and life stages, and directly affect metabolic efficiencies. My objective was to examine the relationships between marine survival and stage-specific size and growth of pink salmon, and to quantify the importance of thermal regime, food supply, and food quality in this relationship. During 2001-2004, juvenile pink salmon in Prince William Sound and the coastal Gulf of Alaska exhibited a 3-fold difference in marine survival. Based on back-calculated size and growth at different life stages, significant size selective mortality occurred after the summer growing season, and size-selective mortality was more severe during years with lower overall marine survival. Bioenergetics simulations were used to examine feeding and growth performance between years while explicitly accounting for significant variability in stage-specific distribution, diet, growth, and consumption. From these simulations, we determined that direct effects of thermal regime on growth among years were minor, compared to the effects of prey availability, expressed as higher feeding rates. Higher growth and survival were also associated with larger contributions of non-crustacean zooplankton (larvaceans and pteropods) to the energy budget of salmon. Higher feeding rates on larvaceans and pteropods more than compensated for the slightly lower energy density of these prey. In general, higher marine survival of pink salmon was associated with broader dispersal of juveniles by the “critical period” in August, greater feeding rates, faster growth and larger size for juveniles at the end of the first summer of ocean feeding. Climatic drivers that initiate and support an epi-pelagic food web dominated by cast-net feeding zooplankton improves trophic transfer efficiency by reducing the number of links between primary producers and salmon.
Bio
Dave Beauchamp is an Associate Professor at UW School of Aquatic and Fisheries Sciences and Assistant Unit Leader for the USGS Washington Cooperative Fish & Wildlife Research Unit. He earned a Ph.D. in Fisheries at University of Washington in 1987. He was a staff scientist at UW and private consultant for Northwest Native American Tribes for 3 years, then held post-doc and faculty positions at Utah State University before returning to UW in 1999.
His research program focuses on quantitative food web dynamics of freshwater, estuarine, and marine systems. He and his group have been developing and applying visual foraging models and bioenergetics models that link individual physiology and behavior to environmentally-mediated processes that determine structure and function of aquatic systems. He has worked on many of the large coldwater lakes in the western US, Puget Sound, and the Gulf of Alaska.
Dave lives with his wife Geetha and daughters Saritha and Meera. He enjoys outdoor activities, reading, music, and playing jazz or blues saxophone.
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