Predation by Rainbow Trout (Salmo gairdneri): the Influence of Hunger, Prey Density, and Prey Size

Abstract

The feeding behavior of rainbow trout (Salmo gairdneri) was investigated by exposing fish to several densities and sizes of prey over a range of four substrates of varying complexity. Within substrate treatments the rate of predation could be stimulated by increasing either prey density, prey size, or predator hunger. Between treatments, however, both the intensity of predation and total food consumption proved to be inversely related to the complexity of the substrate because a number of prey were able to find cover and thus escape detection.The results further indicate that the nature of foraging behavior may be controlled by a critical rate of food capture. If trout did not exceed an average of.058 captures sec,⁻¹ substrate-oriented search proceeded to wane.