Post-settlement predation by sea stars and crabs on the sea scallop in the Mid-Atlantic Bight

Abstract

Year-class strength of benthic invertebrates is generally determined during early life-history stages. However, the contribution of different biotic and abiotic factors to the resulting abundance and spatial distribution of recruits is poorly understood. We infer the effect of postsettlement mortality by benthic invertebrate predators on recruitment of sea scallops Placopecten magellanicus based on an 11 yr time series of survey data from the east coast of the United States. We reconstructed predator densities at different life-history stages for scallops and identified the stages when scallop recruitment dynamics are best explained by predator densities. Based on spatial associations and temporal dynamics, we found evidence that sea stars Astro pecten americanus and crabs Cancer spp. are causing localized depletion of sea scallop recruits. Both predator groups appear to be affecting scallop recruitment primarily in the first year post-settlement. The spatial and temporal coherence in predator−prey fluctuations partially ex plains the most dramatic recruitment events in the past 3 decades and suggests that predation on recruits may also limit the geographic distribution of sea scallops in this region.