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
