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Blue Crab

Callinectes sapidus

Although they are called
Although they are called "blue" crabs, these crustaceans may vary in color from blue to olive green. (Tonya Lane Rucker/Flickr)

The blue crab is a swimming crustacean with bright blue claws and an olive green shell. It is one of the most recognizable species in the Chesapeake Bay.

Appearance:

  • Carapace (shell) varies in color from bluish to olive green, and can reach up to 9 inches across
  • Carapace has nine marginal teeth on each side. The ninth teeth are strong spines
  • Claws are bright blue. Those on mature females feature red tips 
  • Three pairs of walking legs
  • Paddle-shaped rear swimming legs
  • Males have a strongly tapered abdomen, or "apron," that resembles an inverted T. Mature females have a broad, rounded abdomen. Immature females have a triangular abdomen

Habitat:

  • Bottom-dwelling crustacean uses all of the Chesapeake Bay's habitats during the course of its life
  • Distribution varies based on age, sex and season
  • Abundant in shallow waters and bay grass beds during warm weather. Hibernates in the deep trenches of the Bay in winter
  • Males spend more time in the fresher waters of the Bay and its rivers, while females congregate in saltier waters

Bay 101: Blue Crabs from Chesapeake Bay Program on Vimeo.

Range:

  • Found in the Chesapeake Bay and its tidal rivers year-round
  • Range spreads from Nova Scotia to Argentina in the western Atlantic Ocean

Feeding:

  • Will feed on nearly anything it can find, including clams, oysters, mussels, smaller crustaceans, freshly dead fish, and plant and animal detritus
  • Will even eat smaller and soft-shelled blue crabs

Predators:

  • Predators include large fish like croakers and red drum; fish-eating birds like great blue herons; and sea turtles

Reproduction and Life Cycle:

  • Mate from May through October in the brackish waters of the middle Chesapeake Bay
  • Before mating, males cradle a soft-shelled female in their legs, carrying her for several days while he searches for a protected area for her final molt. Once she molts, the pair mates. After mating, the male continues to cradle the female until her shell hardens
  • Males eventually leave to search for another mate, while females migrate to the saltier waters of the lower Bay. Females develop an external egg mass, or sponge, beneath their aprons
  • Each bright orange egg mass may contain between 750,000 and two million eggs. The egg mass darkens as the developing larvae consume the orange yolk. In about two weeks, larvae are released into the salty waters near the mouth of the Bay
  • Currents transport blue crab larvae, called zoea, to the ocean, where they molt several times as they grow. Eventually, zoea return to the Bay and other estuaries
  • During their last larval molt, zoea metamorphose into a post-larval form called the megalops. Megalops crawl over the Bay’s bottom to reach the upper Bay and its rivers
  • Megalops eventually metamorphose into immature crabs, which look like tiny adults. Immature crabs molt several times before they reach maturity, about 12 to 18 months after hatching
  • Few blue crabs live longer than three years

Other Facts:

  • The blue crab’s scientific name comes from the Greek words for “beautiful” and “swimmer.”
  • Male blue crabs are known as “jimmies,” while mature females are called "sooks."
  • Blue crabs are one of the most important commercial and recreational catches in the Chesapeake Bay.

Sources and Additional Information:




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