Predation of Atlantic Sea Scallops On the Northeast United States Continental Shelf – Are Commercial Scallop Discards Contributing to Groundfish Diets?

The Atlantic sea scallop, Placopecten magellanicus, is currently the most valuable U.S. fishery.  Many groundfishes are known to consume sea scallops.  We examined 31 years of fish diet data for the top ten sea scallop feeders by percent frequency of prey occurrence. The main objectives were to describe scallop predation by groundfishes and examine spatial and decadal trends in viscera consumption for the northeast U.S. continental shelf.  Scallops appear in the diet either whole, indicating live predation, or as viscera from scallop discards.  Scallop feeding primarily occurred on commercial scalloping grounds in the Mid-Atlantic Bight and Georges Bank regions of the shelf.  Diet indices (percent mass and percent frequency of occurrence) and population indices (kg tow^-1) of sea scallops  increased concurrently over the three decades sampled, demonstrating the commercial and trophic importance of these resources.  Although other studies find negative effects of chronic bottom fishing on shelf habitats and fish diets, and whole sea scallop frequency of occurrence in stomachs (1-8%) and diet composition by mass (1-15%) is generally low, increased availability of scallop viscera may be beneficial for opportunistic fish predators.  Whether scallop discards are simply maintaining fish populations or actually contributing to population growth remains an interesting question.