Laboratory and Field Studies of the Effect of Predation Risk On Foraging in Three-Spined Sticklebacks (Gasterosteus Aculeatus)

This article describes a series of experiments carried out in both field and laboratory on the effects of predators on foraging in threespined sticklebacks (Gasterosteus aculeatus). In a field experiment on habitat use, predation risk did not cause the fish to abandon their preference for vegetated habitat, but led them to increase the use of the lake bed. However, in the presence of a predator, the fish still fed mainly on zooplankton rather than on benthos. In a field experiment on diet choice, predation risk suppressed the amount of food eaten and caused a shift to different prey species and smaller prey. In a laboratory experiment, predation risk slowed the response to the food and caused the fish to cease discrimination in favour of the more profitable food items. The number of feeding attempts was not affected, which could mean that the fish were compensating for their slow start by a higher subsequent rate of bites once feeding began. Thus, predation risk affected the foraging behaviour in such a way that energetic intake was reduced in the interest of predator avoidance.