Complex Predator-Prey Interactions in Marine Soft-Bottom Communities: Crabs, Clams and Patch Dynamics

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The overall goal of this research is to determine quantitatively, the interactive regulatory factors and underlying mechanisms of predator-prey dynamics in a marine soft-bottom community. The researchers have extensive background knowledge as well as an innovative ultrasonic biotelemetry techniques to examine the predator-prey complex in a small sub-estuary (the Rhode River) of Chesapeake Bay. The researchers will measure the components of predator behavior which lead to changes in the functional and aggregative responses. The predator-prey complex includes large blue crabs (Callinectes sapidus) which feed on two common species of infaunal clams (Macoma balthica and Mya arenaria) as well as cannibalizing small blue crabs. Demersal fish are also abundant predators which feed extensively on clam siphons and other benthic invertebrates which live in the sediments, but not on large whole clams. Earlier work focused on the interactive effects of prey species, sediment type, and prey density on the persistence of prey encountering intense predation, with emphasis on the functional response of blue crabs foraging on clams. Biotelemetry has been used to determine the scales of variation in predator behavior and movement between key prey patches. Thus, these investigatins focus on the blue crab's aggregative response with prey patches, which links the regulatory factors, underlying mechanisms, and resulting dynamics of this predator-prey system. This research will: 1) determine the interactive factors (prey species, prey density, and predator density) regulating the aggregative response of the main predator (large blue crabs); 2) determine the interactive factors (density and distribution of prey, habitat refugia, and predator density) regulating predation rates upon two alternate prey (clams and small crabs); and 3) investigate the behavioral/physiological mechanisms of large blue crabs aggregating in prey patches and switching between small crabs and clams.