Regimes of river temperature and flow in an interior watershed, and their implications for Chinook salmon

Climate change and human activities are altering river flows and temperatures, with potentially large consequences for aquatic life. I investigated how changing river flows affect salmon productivity, and how climate sensitivity varies across a watershed. First, I tested the effects of shifting river conditions on Chinook salmon productivity in a river where average August river discharge decreased by 26% in the last century. Summer low flows had the greatest negative impact on productivity: cohorts that experienced 50% below average flow in the August of spawning and rearing had 40% lower productivity. Second, I examined whether watershed characteristics could predict which streams were warmest and most sensitive to regional climate. Streams with more riparian forest cover were cooler overall and less sensitive to warmer air temperatures. Overall, this research shows that restoring river flows and watershed-scale forest management are essential parts of salmon conservation.