Role of predatory infauna in structuring marine soft-bottom communities

Present characterizations of interactions in marine soft-bottom communities classify fishes, crabs and birds (epibenthic predators) as predators, and infaunal species as prey. Many infaunal species, however, are themselves predators and - as prey for epibenthic predators and predators on other infauna - may function as intermediate predators. Data from 7 studies which employed cages to exclude epibenthic predators were used to test the hypothesis that predatory infauna do not become proportionally more abundant following exclusion of epibenthic predators. Predatory infauna became proportionally more abundant after epibenthic predators were excluded from muddy-sand and seagrass habitats. This increase could be a consequence of preferential predation on predatory infauna by epibenthic predators, preferential predation on predatory infauna and predation by predatory infauna on other infauna, or equal predation on all infauna with additional predation by predatory infauna on other infauna. The result suggests that predatory infauna should be considered separatly from non-predatory infauna when modeling interactions in soft-bottom communities and allows the prediction that prey species of predatory infauna may be less abundant in the absence than in the presence of epibenthic predators.