The dungeness crab (Cancer magister) is a large edible crab found in the coastal waters of the Pacific Ocean. It is native to the west coast of North America from California to Alaska and is an important species both ecologically and commercially. They are named for a specific region in Western Washington, Dungeness Spit, where they have been found in abundance.
The coloring of a dungeness crab is usually a light brown to beige with a blue or purple tinge on top of the shell (known as the carapace) while the underside is a light orange or tan. Mature dungeness crabs can grow to a size of over 10 inches across when the shell is measured length wise. The body is an oval shape and the legs and claws are short relative to its body size. As with other types of crabs, Dungeness crab possess one pair of claws and four pairs of walking legs which are used to walk in a sideways fashion with one side pulling and the other side pushing. The eyes of the dungeness crab are set on short stalks and are beady in appearance. The claws are usually tipped in white and are more pale when compared to the rest of the crab’s coloring. Each claw has saw marks on the outside and inside of each pincher and are used to grasp and tear off pieces of food or to defend off predators.
Dungeness crab are found primarily on the floor of the ocean in depths near the shore to 2,000 feet deep. They also frequent tide pools and can be found buried in the sand while the tide is going out. Dungeness crab are known as opportunistic carnivores and eat a wide variety of prey that usually consists of other shellfish such as shrimp, mollusks, and other crabs. They also eat small fish, worms and any other organisms that they find hidden in the sand.
Dungeness crab are also an important food source for many other organisms. When they are in their immature larval stage, dungeness crabs are eaten along with zooplankton and other tiny water organisms by salmon, halibut, sardines, herring, and rockfish. As the crabs mature, they are eaten by sea otters, octopus, and dogfish.
Sexual maturity is reached at 2-3 years of age. In this species of crab, males are typically larger than the females with mature males reaching a size of 7 inches across and females measuring at only 6 inches across. Mating of dungeness crab takes place in the spring or early summer. In order to mate, timing of molting for the female is crucial. Females can only mate immediately after they have molted as mating is impossible when her shell is hardened. A male can only mate with a newly molted female. After mating, the male stays with the female and defends her against predators and other threats until her shell has hardened. The female then carries the eggs with her for 3 months until the eggs hatch.
The newly hatched crab (called zoea) resemble nothing like their adult form and drift along in the water with other tiny water organisms while they grow. The zoea will go through five stages of growth before changing into a new form called a megalope. The megalope stage looks like a miniature version of the adult form and only measure a few millimeters in size. During this stage, the megalopes are still drifting in water currents and are frequently eaten by larger predators. Megalopes that survive then become juvenile dungeness crabs and take refuge in the sand from predators as they grow larger. Dungeness crab that make it to sexual maturity and are not eaten by predators can live up to 13 years.
Commercial fishing of dungeness crab is an economically valuable resource to the economies of Western North America. Dungeness crab are captured using crab pots, crab nets, and traps. Commercial harvesting of dungeness crab occurs during the winter months of the year and only crabs that are at least 6-7 inches when measured across are retained. Dungeness crab is delicious and can be prepared in many different ways from simply being steamed and dipped in butter to elaborate crab cakes and bisque.