Zebra mussel colonies and yellow perch foraging: Spatial complexity, refuges, and resource enhancement

Throughout the Great Lakes basin, the invasion of zebra mussels has led to substantial increases in benthic invertebrate densities around zebra mussel colonies. This research focused on whether the enhanced benthic community associated with zebra mussel colonies is available to yellow perch, a bottom-foraging fish. In a series of laboratory trials, perch foraging success was examined under conditions of continuous and patchy zebra mussel coverage using gammarid amphipods and the midge Chironomus tentans as prey. Perch were less successful foraging for amphipods when Zebra mussel coverage was continuous and marginally less successful foraging for chironomids when zebra mussel coverage was patchy. In a second laboratory series of videotaped trials with patch), coverage and amphipod prey, the use of space by both amphipods and foraging perch was examined. In these trials, perch actively foraged on the zebra mussel colonies even though their strikes g,ere less likely to be successful there than on bare sand. Perch tended to take amphipods in exposed areas first, but because many more amphipods located themselves in zebra mussel colonies, many prey were taken in this habitat too. These results suggest that yellow perch are able to exploit the extra prey resources in zebra mussel colonies, although it may require slightly, more effort to do so.