Effect of Algal Cover on Size-Selective Predation of Gammarus mucronatus by the Striped Killifish, Fundulus majalis.

Abstract

Predation on Lysianopsis was lowest (15.4%) in Cladophora (Fig. 1, bottom), which forms a thick intertwining mat. The amphipod’s strategy for avoiding predation was to burrow deep into the algae, putting itself out of the reach of the predator. In the field, however, such behavior might be hindered by the anoxic conditions often found in the mat. The experimental methodology of this study allowed for a fairly complete exchange of the interstitial mat water, which resulted in aerobic conditions throughout the mat. Predation was high (73.8%) in the eelgrass, probably because crawling and burrowing amphipods cannot take advantage of the vertical structure of the plant. Predation was highest (93.3%) in the ‘no vegetation’ treatment because there was no substrate available to provide protection. Predation rate was analyzed in a one-factor ANOVA (P = 0.05). Differences among treatment means were evaluated using Fisher’s PLSD (P = 0.05). There were strong differences in predation rates between prey in different vegetation types (F = 227.6 15). All predation rates were different from each other except in the ‘no vegetation’ treatment. Many invertebrate species are highly dependent upon macrophyte structure and color for protection against predation (2). Alteration of the primary producer community due to eutrophication may change the structure of the habitat and may potentially have second-order effects on the invertebrate community. This study was supported by the Boston University Marine Program and the Cox Foundation.