Stream size, temperature, and density explain body sizes of freshwater salmonids across a range of climate conditions

Climate change and anthropogenic activities are altering the body sizes of fishes, yet our understanding factors influencing size for many taxa remains incomplete. We evaluated relationships between climate, environmental, landscape attributes different freshwater trout (Salmonidae) in USA. Hierarchical spatial modeling across a gradient habitats (5221 sites) illustrated importance watershed effects, which explained 17%–45% variation taxa. Stream had strong, positive relationship with size, there was approximately tenfold difference strength Trout consistently declined increasing density Despite reliance on cold water, we found summer stream temperature most Our results highlight how providing access to larger, productive rivers expression growth life-history would promote diversity within populations.