The juvenile and adult blue crab has been described as a opportunistic benthic detritivore, omnivore, primary carnivore, cannibal, and general scavenger. Food habit studies have shown that predominant food items vary greatly, depending upon availability. The blue crab is well known for its cannibalistic habits. Blue crabs in poor health, missing important appendages, heavily fouled with other organisms, and those within or immediately following ecdysis are more likely to be cannibalized. Papershell crabs regularly consume their own molted exoskeletons.
Blue crabs feed in three different ways.
Blue crabs are a crucial factor in the estuarine food web because of their opportunistic feeding habits, high abundance levels, and their great tolerance of salinity. Blue crabs also dig into sediments to both forage and hide, thus killing more organisms than they consume. Blue crabs may have detrimental effects on commercial invertebrate species such as oysters, hard clams, and soft clams and have been documented to influence the distribution and abundance of other invertebrate species. Larval blue crabs are fed upon by other plankters, small fish, filter feeding fish, jellyfish, and comb jellies. At least 60 species of fish have been identified as blue crab predators.