Effects of Climate Change on Oregon Coast Coho Salmon: Habitat and Life-Cycle Interactions

Effects of climate change on salmon stocks are of interest from both harvest management and conservation perspectives. Coho salmon (Oncorhynchus kisutch) populations that spawn in the coastal rivers of Oregon are listed as a 'threatened species' under the U.S. Endangered Species Act, and are thus of particular interest. We assess the effects of climate change on sustainability of this population group. Four distinct habitats are important to different life-history stages of coho salmon: terrestrial forests, freshwater rivers and lakes, estuaries, and the North Pacific Ocean. Each of these systems is affected by multiple aspects of climate change, resulting in a complex web of pathways influencing sustainability. We summarize regional climate change studies to predict physical changes affecting these habitats, identify the ecological pathways by which these changes will affect coho salmon, and review coho salmon ecology to assess the likely direction and magnitude of population response. Despite substantial uncertainties, the preponderance of negative effects throughout the life cycle indicates a significant climate-driven risk to sustainability of these populations. We recommend that management policies for all four habitats focus on maximizing resilience to the effects of climate change as it interacts with other natural and anthropogenic changes.