Range expansion of the tropical predatory crab <i>Eurytium limosum</i> (Say, 1818) (Decapoda: Brachyura: Panopeidae) into temperate salt marshes along the eastern coast of the United States

Abstract We document the range expansion of Eurytium limosum (Say, 1818), a panopeid, mud crab commonly found in Florida mangroves and in southeastern US salt marshes, from its historically known northern range limit in southern South Carolina to newly observed range in central North Carolina (NC) salt marshes. Through field surveys conducted in 2024, we recorded E. limosum populations in two salt marshes on Bogue Banks-Atlantic Beach, NC. Field surveys conducted in two salt marshes showed that this predatory crab is very abundant in both marshes, and its densities vary by marsh zone, with the highest abundance occurring in the low marsh. Compilation and analysis of published and unpublished data on mud-crab density in these same marshes reveal that E. limosum was not present in these marshes in the mid-1990’s but were at low densities in 2016, 88% lower than they were in 2024. Combined, these findings indicate a significant northward expansion (at least ~400 km) of E. limosum likely influenced by rising sea temperatures in NC. Given their current abundances and past studies that show this mesopedatory crab preys on two key salt marsh consumers, fiddler crabs and plant-grazing snails, and that it is an aggressive competitor, E. limosum will likely alter top-down forcing of marsh structure and function and/or competitive interactions with other infaunal marsh predators. We document what is likely the beginning of the tropicalization of the predator assemblage of temperate salt marshes, underscoring the importance of monitoring the distribution of marine species in response to climate change, and suggests potential impacts on local ecosystems and biodiversity that warrant future investigations.