Collaborative Research: Direct and Indirect Effects of Fish Predation of the Freshwater Littoral Benthos

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Many ecological communities are structured in ways considerably more subtle and complex than can be expressed in the standard trophic hierarchy, with its superimposed layers of predators, potentially cross-linked by competition. Drawing upon nine years of research on the littoral biota of Bays Mountain Lake (Kingsport, TN), this project will identify and measure the critical biotic interactions among the dominant vertebrate predator (redear sunfish, Lepomis microlophus), the dominant invertebrate predator (larvae of the dragonfly Tetragoneuria cynosura), and their prey community. The three component experiments examining these interactions will be conducted: (1) large-enclosure experiment manipulating two size-classes of fish; (2) a small-enclosure experiment manipulating small fish and two-year classes of dragonflies; and (3) laboratory experiments designed to identify the behavioral mechanisms underlying the field results and strengthen their interpretation. Concepts emerging from each component will be integrated by the research team to provide a realistic model of forces structuring littoral communities. These studies are designed to measure the direct effects of predation, which may result in either increased mortality or reduced growth or both. Indirect effects of predation will also be assessed and may be either stimulatory or inhibitory to particular prey. Interference and exploitation competition is the final aspect which may be either within or between species. The results will help change our fundamental assumptions about community organization, and will provide a comprehensive understanding of one community's structure, including how that structure arises from underlying behavioral and ecological mechanism. Understanding gained through this collaborative effort will provide a valuable information base for fisheries biologists and lake managers.