Early stages of the Asian shore crab Hemigrapsus sanguineus as potential prey for the striped killifish Fundulus majalis

The Asian shore crab Hemigrapsus sanguineus is a recent invader of rocky intertidal shores along the U.S. Atlantic coast whose predators have not been well identified. One potential predator of settling larvae (megalopae) and small juvenile crabs is the striped killifish, Fundulus majalis, which forages on small benthic animals. Laboratory experiments were conducted with and without sediment, consisting of sand and rocks to mimic the rocky intertidal, in order to determine whether F. majalis can consume H. sanguineus and if habitat structure reduces predation success. F. majalis juveniles (< 60 mm total length and lacking signs of sexual differentiation) and male and female F. majalis 60–80 mm, 80–100 mm, and > 100 mm in total length were individually offered megalopae, 1st stage crabs, and crabs 3–5 mm and 5–7 mm in carapace width (CW). Megalopae and 1st stage crabs were consumed more readily than crabs ≥ 3 mm CW by all size classes and both sexes of F. majalis. Megalopae were eaten regardless of whether or not sediment was present, but predation of 1st stage crabs was less in the presence of sediment. Gut content analyses were performed on F. majalis collected from rocky intertidal shores to determine whether results from laboratory experiments were indicative of H. sanguineus consumption by F. majalis in the wild. No H. sanguineus or other crabs were found in the guts of 37 F. majalis analyzed. Common prey items included small blue mussels (Mytilus edulis), hard-shelled clams (Mercenaria mercenaria), and unidentified crustaceans. Although F. majalis readily preyed on Asian shore crab megalopae and newly-settled crabs in the laboratory, it might not utilize H. sanguineus as prey in nature.