Atlantic blue crab

Blue crabs eat almost anything they can find.

They eat clams, mussels, little fish and plants.

Blue crabs are not picky. They eat clams, oysters and mussels, smaller crustaceans, fish that have just died, and bits of dead plants and animals.

Blue crabs are also food for many animals. Big fish such as striped bass and red drum eat them, and herons and sea turtles catch smaller crabs.

The Chesapeake Bay Program describes blue crabs as feeding on nearly anything they can find: clams, oysters, mussels, smaller crustaceans, freshly dead fish, and plant and animal detritus, including vulnerable soft-shelled blue crabs and small juveniles of their own species.

They are in turn prey for large fish such as striped bass, Atlantic croaker and red drum, and smaller crabs are eaten by predatory birds such as blue herons and by sea turtles. The 2026 Blue Crab Advisory Report lists predation by red drum and blue catfish among factors researchers are investigating for low crab numbers.

Blue crabs can walk and swim.

They paddle with their flat back legs. In winter they dig into the mud and rest.

Blue crabs can walk on the bottom, but they can also swim, paddling with their flat back legs. That is why their name means "beautiful swimmer."

They move with the seasons. In summer they spread through shallow water and seagrass beds. In winter they bury themselves in the mud in deeper water. Males often stay in fresher water, while females travel to saltier water to release their eggs.

Blue crabs combine bottom-walking with active swimming on their paddle legs. In the Chesapeake Bay their distribution shifts seasonally: summer in shallows and seagrass, winter buried in deeper sediment, with the sexes partly separated by salinity.

Overwintering is risky. The 2026 Blue Crab Advisory Report notes that although crabs overwinter buried in the mud, cold water can still kill them; overwintering mortality in winter 2025–26 was 5.17 percent of the population, above the 4.19 percent average, after extended cold snaps.

Lots of people catch blue crabs to eat.

Scientists count the crabs every winter. Rules help keep enough crabs in the bay.

Blue crabs are one of the most important catches in the Chesapeake Bay. Every winter, scientists count crabs to help set fishing rules. In 2026 they found that the crabs are not overfished, but there are fewer grown-up females than they would like, so they asked for careful limits.

Far from home, blue crabs can cause problems. People have carried them to Europe, and in Spain's Ebro Delta they have spread quickly. Scientists there found that several other animals declined as blue crabs took over.

There is no IUCN Red List assessment. In the Chesapeake Bay, the Chesapeake Bay Program reports that the population has not been overfished since female-specific management began in 2008. The Chesapeake Bay Stock Assessment Committee's 2026 Blue Crab Advisory Report found the stock not overfished, but the total population of 349 million was below the 1990–2025 average and adult females (81 million) were below the 196 million target, so it recommended that Maryland, Virginia and the Potomac River managers stay cautious.

As an invader the species is serious. Clavero and colleagues (2022) report that in Spain's Ebro Delta it was first recorded in 2012, expanded from about 2016 and increased exponentially in 2017–2018, as several species, including threatened and commercially exploited ones, declined steeply; they describe it as becoming a keystone species in invaded systems.