Daytime Responses of Brown Trout (Salmo trutta) to Cover Stimuli in Stream Channels

Experiments were conducted to identify stimuli to which stream-dwelling brown trout responded in selecting concealment or “cover.” The trout were 25-30 cm in total length. In each experiment, a group of five trout had choice of two types of cover in a channel 27 m long and 3.4 m wide with water 20-30 cm deep, flowing 22-37 cm/s. The fish preferred overhead cover 10 cm rather than 15 or 20 cm above streambed (P < 0.001), as well as cover with tactual features (P < 0.03). There was no apprent increased response to overhead cover that offered added visual reference features or lateral concealment.