Annual variation in stream flow is associated with dramatic fluctuations in invertebrate abundance and the density of juvenile cyprinid and centrarchid fishes. In the absence of centrarchid predation, small fishes depress invertebrate abundance in pool habitats but not riffles, and centrarchid predators restrict juvenile fishes to shallow riffle refugia while engaging in species- and size-selective predation. This research is a logical extension of these findings. Experiments will quantify the simultaneous influence of stream flow, centrarchid predation, and juvenile fish density on invertebrate resources and juvenile cyprinid and centrarchid fishes below a beaver pond. Hypotheses will be tested related to the following four questions: 1. How sensitive is the growth and survivorship of juvenile cyprinid and centrarchid fishes to changes in fish density and what, if any, effect does interspecific use of invertebrate resources have on the growth and survivorship of these fishes? 2. Do changes in flow regime below beaver ponds shift the intensity and outcome of resource use by juvenile cyprinid and centrarchid fishes? 3. What effect do centrarchid predators have on the intensity and outcome of resource use by juvenile cyprinids and centrarchids? 4. How do changes in flow regime below beaver ponds effect predator-prey interactions and the outcome of invertebrate resource use by juvenile cyprinid and centrarchid fishes? This research will greatly enhance our understanding of the regulation of growth and survival in stream fishes. It will also increase our ability to incorporate the effect of hydrologic regime on trophic interactions into emerging conceptual models of north-temperate aquatic landscapes.
