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DUNGENESS CRAB

DID YOU KNOW? Male dungeness crab find females with the use of pheromones (chemical scents) and after mating the male may remain with the soft-shelled female for two days to insure her protection.

SCIENTIFIC NAME: Cancer magister, cancer is Latin for crab.

COMMON NAMES: Pacific edible crab, dungeness crab, market crab, commercial crab, and edible crab.

DESCRIPTION: Beige to light brown with blue trim; often light orange below. Short eyestalks with small orbits. Broadly oval carapace; uneven, but not highly sculptured.

LIFECYCLE: Mating occurs outside of estuaries in near-shore coastal locations. Eggs hatch in two to three months. Larvae are planktonic using tidal currents to self propel and "hitch-hike" on jellyfish in order to travel into estuaries. Juveniles settle in shallow coastal waters, tidal flats, and estuaries, living on beds of eelgrass and other aquatic vegetation. Growing through a series of molts to adulthood, the Dungeness crab is common in coastal waters offshore and in estuaries. Studies suggest that growth rates vary along the Pacific coast and that higher water temperatures in estuaries (> 6 degrees Celsius) and abundant food can accelerate growth.

HABITAT AND ECOLOGY: The Dungeness crab plays an important role in the food chain as predator and prey in estuarine and marine environments. Early in life, Dungeness crab fall prey to nemerteans (marine worms) that feed on their eggs. Dungeness crab larvae are important food for Pacific herring, Pacific sardines, rockfish, and chinook salmon. Juvenile Dungeness crabs are eaten by starry flounder, English, and rock sole, lingcod, rockfish, sturgeon, sharks, and skates. As juveniles living in estuaries, Dungeness crab feed primarily on fish, shrimp, molluscs, and crustaceans. During this life-stage, estuaries are especially important; thus any action, such as dredging or habitat modification projects, should be considered in light of their impacts on Dungeness crab. Adults feed on shrimp and bivalves and are eaten by humans, harbor seals, and sea lions.

Dungeness crab are intolerant of low dissolved oxygen conditions, and even low concentrations of ammonia are toxic. The insecticide sevin (carbaryl) which is sometimes used to control ghost shrimp in Pacific oyster beds is also very toxic to Dungeness crab. Dungeness crab larvae are highly sensitive to other insecticides and fungicides as well. They are also impacted by urban pollutants such as heavy metals, PCBs, and hydrocarbons. Concentrations of these contaminants presently exist in San Francisco Bay and sublethal impacts have been observed. The control of non-point source pollution -- pollution resulting from the runoff of pesticides and herbicides from our yards and farmland, as well as heavy metals and hydrocarbons from our streets -- is important to the health of Dungeness crab populations.

RANGE: Found in coastal waters from Santa Barbara, California, to the Pribilof Islands, Alaska. Dungeness crab probably inhabit all estuaries from Morro Bay, California to Puget Sound, Washington. Two important juvenile crab production estuaries are Willapa Bay and Grays Harbor in Washington state.

ECONOMIC VALUE: An important commercial shellfish harvested along the coast from California to Alaska, Dungeness crab are usually caught in nearshore marine waters under 120 feet deep with baited crab pots. An average of 17,000 tons, worth tens of millions of dollars, are caught annually, usually in the first two months of an average nine month season. Recreationally, Dungeness crab are also important, and are caught intertidally by hand or subtidally by crabpots, nets, or even hook-and-line.


Revised 12/16/96