Do Brown Trout Choose Locations with Reduced Turbulence?

Abstract

The physical habitat requirements of cover, depth, and current speed for brown trout Salmo trutta are associated with high shear zones in stream flows, which in turn result in high turbulence. Observations were made on current speeds and turbulence intensity (TI) in a sand-bed trout stream. Exemplary transects showed that current speeds ranged from 0 to 60 cm/s and that TI ranged from 0 to 0.7. Turbulence intensity was inversely related to current speed. Brown trout were usually found in the lower 5 cm of the stream, where shear forces result in high turbulence. Locations occupied by brown trout had lower TI than similar locations without brown trout but higher TI than is typical of an average stream.