Changes in foraging as a response to predation risk in two gobiid fish species, Pomatoschistus minutus and Gobius niger

Abstract

The influence of predation risk and hunger level on the foraging rate and swimming activity in the sand goby Pomatoschistus minutus and the black goby Gobius niger was tested in aquarium experiments. The fish were given a choice of 2 habitats, viz, vegetation uithout food, and open sediment with natural prey density. Both species had a lower food consumption in the presence of predators than without predators, but starved fish had a higher consumption rate than fed fish both in the presence and in the absence of predators. Starved fish thus took higher risks of being eaten than did fed fish. P. minutus decreased their swimming activity in the presence of predators, which may have caused the lower food intake. However, G. niger did not change their activity with predator presence. Habitat choice must also be of importance for the foraging rate in gobies. G. niger were mostly found in the vegetation, which 1s their natural habitat. P. minutus to a greater extent inhabit open areas in the field and therefore might gain more from decreasing their activity than seeking cover at high predation risk.