Energetic factors influencing foraging tactics of juvenile steelhead trout, Salmo gairdneri
Increases in water temperature and fish size should increase standard metabolism and food demand. Stream-dwelling trout may then, despite the increased cost of swimming, seek faster water where food is more abundant. We tested these predictions with juvenile steelhead trout, Salmo gairdneri, in a California stream and found that increased fish size and water temperatures did result in the increased selection of microhabitats with high water velocities. Faster water provided proportionally larger amounts of drifting invertebrate food. Higher velocity, shallower, and coarser substrate microhabitats also enabled fish to capture prey from portions of the water column substantially faster and more productive than at their resting positions. Velocities selected in this stream were similar to those which would result in a doubling of metabolic rate. Models evaluating trout habitat and effects of modifications should take energetic factors into account.
KeywordsDrift Flow Growth Metabolism Microhabitat Satiation Substrate Swimming Temperature Velocity
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