Behaviour separates potential and realized effects of decapod crustaceans in salt marsh communities

Experimental and observational studies of foraging behaviour and the impact of decapods in marine communities have been rather narrowly focused either by design or necessity. Often, foraging responses are, measured relative to a very limited selection of prey (resource) types and environmental conditions. However, many decapods are opportunistic foragers, with their diets and impact on resources determined by a blend of behavioural responses sculpted by constraints imposed by ambient conditions. Measuring responses without regard for appropriate behavioural constraints may not adequately predict the magnitude of a species' impact, or its lack of impact, on a natural community. Examples, derived primarily from studies in salt marshes, illustrate several ways that predicted and realized effects of decapods on benthic and epibenthic prey assemblages may differ considerably. Although decapods have been excellent subjects for studies of foraging theory and predator-prey dynamics, experiments and sampling programs designed to assess their impacts within natural communities must include explicit consideration of the many biotic and abiotic elements that influence foraging behaviour at different temporal and spatial scales. Only through such a filter of behavioural constraints can realized impacts be separated from the many potential effects decapod crustaceans may have within natural communities.