The influence of fish predation in an experienced prey community

The impact of predaceous fish on littoral macroarthropod abundances was examined during a 1-year predator density manipulation experiment in a central Texas reservoir. Six sites were selected to receive experimental units. Each site consisted of two 8-m2 plots. One plot at each site was inaccessible to fish predators, the other plot was freely accessible to fish. Fifty-four artificial substrates which simulated natural vegetation were placed in each plot to provide homogeneity in habitat structure and allow quantitative sampling of macrophyte-dwelling invertebrates. Total macroarthropod density in predator-exclusion plots exceeded densities in control plots on 10 of 12 dates examined, but this difference was significant on only 3 dates. Chironomids, the most abundant taxon in samples, were unaffected by predator manipulation. Abundances of two common species, Orthotrichia sp. (Trichoptera) and Hyalella azteca (Amphipoda), were generally enhanced by predator exclusion. Numerically minor taxa showed little ...