Seasonal Variation in the Bioenergetic Cost of Migration in Snake River Spring/Summer Chinook Salmon and Potential Selection for Earlier Migration in Response to Climate Change

Life-history diversity contributes substantially to resilience in the face of environmental variability. In salmon, variation in migration and spawn timing play a crucial role in regional biocomplexity. Salmon migrate up the Columbia River to spawning grounds every month of the year. Individual populations, however, have very restricted migration timing, reflecting local adaptation to diverse constraints associated with specific spawning grounds. I here explore how the bioenergetic cost of migration plus holding near the spawning grounds varies with migration date for particular populations. Detailed records of individual migration times and energy usage through dams and reservoirs provide a very rich picture of these costs. I test the hypothesis that current migration timing reflects the optimal timing predicted by bioenergetic constraints and thermal tolerances. I assess how changing hydrological conditions with global warming will shift the optimal phenology. By incorporating potential evolutionary and plastic responses to this shift in optimal phenology into population-specific life cycle models, I assess the impact of climate change on the diversity of life histories currently exhibited in the Columbia River Basin.