Microhabitat of hatchery rainbow trout

Abstract

Hatchery rainbow trout, wild rainbow trout, or wild brown trout were introduced into a flume that simulated a natural stream. Fish were observed hourly and parameters of the selected microhabitat locations were measured. Fishes differed in water velocity of microhabitat areas selected, water strata utilized, and degree of thigmotaxis exhibited. Hatchery rainbow trout selected areas along side of the flume or above a structure and along side of the flume that had a water velocity of 0.9 ft/sec (27.4 cm/sec). They utilized the middle of the water column, were positive rheotactic, and were not thigmotactic. Wild rainbow trout utilized the same areas in the flume, but the water velocity was 0.7 ft/sec (21.0 cm/sec). They utilized the bottom of the water column, were positive rheotactic, and were thigmotactic. Resident trout affected only subtle changes in the parameters of the microhabitat selected by nonresident trout. Displacement of nonresident hatchery rainbow trout took place only after resident brown trout had been in the flume for 7 days. Resident hatchery trout displaced nonresident brown trout after 3 days in the flume; thus, indicating faster acclimation to flume.