The influence of fish predation in an experienced prey community

Abstract

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 or no response to the exclusion of fish. Overall, our study indicates that fish predation can reduce macroarthropod abundances, but this effect is not dramatic. Results of similar studies conducted in aquatic macroarthropod communities that have historically experienced fish predation support these findings. We suggest that experienced prey (i.e, those that naturally co-occur with fish) are likely to possess antipredator defense characteristics that greatly reduce susceptibility to predaceous fish. Therefore, removal of fish-induced mortality has a minor impact on prey survivorship.

Complex interactions between the zebra mussel, Dreissena polymorpha, and the harmful phytoplankter, Microcystis aeruginosa

“…The phytoplankton in Gull Lake were exposed to mussel grazing for 6 yr prior to our first enclosure experiment, which may have fostered the development of an assemblage of relatively grazing-resistant forms, including M. aeruginosa. As a consequence, we might expect such a phytoplankton assemblage to be less responsive as a whole to changes in mussel-grazing pressure relative to a naive assemblage (Wellborn and Robinson 1991). In addition, TP concentrations in both enclosure experiments were low, and herbivore effects on total phytoplankton biomass are expected to be weak at low TP (Sarnelle 1992).…”

Mechanisms Creating Community Structure Across a Freshwater Habitat Gradient

“…Similar conclusions are drawn from studies comparing the fauna of fishless and fish-containing habitats (27,55,95,123,163,184). In contrast, manipulations of fish density in habitats normally containing fish often produce only minor changes in prey density (14,43,58,173,174,190). Some studies of this sort have indicated more substantial effects of predatory fish (100, 103); however, only prey abundance, not species composition, is affected in these studies.…”

“…That strong predator-prey interactions across the predator transition act as a sieve for community organization (Figure 2) is apparent when one compares studies that manipulate predator density within a single community type, where relatively weak interactions are expected, to studies that introduce a predator into a community type that does not normally contain that predator, a manipulation expected to produce pronounced changes in community composition (172,190). When introduced into a previously fishless habitat, fish precipitate major changes in the community by substantially reducing the density of some prey species, sometimes to the point of local extinction (17,30,47,57,101,124,195).…”

"Cryptic" direct benefits of mate choice: choosy females experience reduced predation risk while in precopula

“…Surveys of bluegill stomachs have shown that 52 to 79% of fish have consumed Hyalella, and this percentage increases to 95% when the smallest fish (<30 mm) are excluded (Wellborn 1994;Wellborn and Cothran 2007a). Moreover, excluding these predators results in an increase in Hyalella abundance (Wellborn and Robinson 1991). Bluegill prefer pairs over single individuals; however, we do not know if the size of a female's mate affects her risk of being consumed by these predators (Cothran 2004).…”