This dissertation improvement award is for a project to test effects of fish predation on the structure of benthic invertebrate communities in streams. Direct and indirect effects of predatory fish on invertebrate behavior and on dispersal are the major components of this research. Field sampling will provide background information on relationships between the distributions of fish, drifting and benthic invertebrates. Field manipulation of fish density in enclosed sections of stream will test effects of fish on drift behaviour and dispersal. A further manipulation will test the effect of fish on benthic community composition in the absence of replenishment by drift from upstream. Experiments in a laboratory stream will test hypotheses about behavioural interactions between fish and invertebrates. These interactions will be filmed and recorded on video cassette for analysis. Researchers will investigate details of the predatory behaviour of fishes in the context of their effect on invertebrate behaviour. In addition, the research will test behavioural responses of invertebrates in the benthos and drift to fish and the cues used by invertebrates to detest the presence of fish. The research will contribute to the conceptual basis of stream ecology and to the information base useful in stream fisheries management.
