Projected impacts of climate-induced changes in water temperature and stream discharge on Henderson Lake sockeye salmon

Multiple regression and delta change factor methods were used to downscale simulated climate data from global climate models to regional air temperature and precipitation variables affecting sockeye salmon in the Henderson Lake watershed on the west coast of Vancouver Island, British Columbia. Exceedance analyses of downscaled data were performed for three climate and freshwater life history interactions: water temperature and upstream adult migration in Henderson River; low flows and spawn timing in Clemens Creek; and peak flows and freshwater survival from egg to fall fry stages. Though the weight of evidence indicates upcoming challenges to the sustainability of the sockeye population due to climate change, net cumulative climatic impacts are uncertain due to a lack of empirical relationships linking climate variation to salmon productivity for all salmonid life stages. The development of a comprehensive population viability model is recommended for assessing climate impacts on salmon populations.