Local Prey Use by Invasive European Green Crabs in a New England Salt-Marsh Estuary

Abstract Impacts of generalist invaders are often discussed as species-level effects, but the trophic interactions that produce those effects are local. We dissected and visually examined stomach contents from 271 European green crabs ( Carcinus maenas ) collected from 21 sampling groups in the Plum Island estuary, Massachusetts, during June–July 2025. We compared the occurrence of foods across marsh-associated primary creeks, main-stem channels, and the open sound. Algal or plant material occurred in 85.2% of crabs, bivalves in 28.0%, crustaceans in 27.3%, and polychaetes in 23.6%. Habitat explained 15.9% of site-level variation in food occurrence, but the overall three-habitat test was not significant ( p = 0.068). The primary-creek–sound contrast was significant after adjustment for multiple comparisons ( p = 0.021). Soft-shell clam ( Mya arenaria ) was identified in 12 crabs, although most bivalve remains could not be identified to species. These results show a generalist consumer using foods from several parts of the local food web, with spatial differences in the balance of foods consumed. The survey extends the history of green-crab diet observations in Plum Island and identifies local trophic interactions that may contribute to habitat differences in impact. Determining those impacts requires measurements of consumption, assimilation, and prey populations in addition to stomach contents.