Dungeness Crab Biology

Drawing of dungeness crab

Dungeness Crab

Taxonomy

  • Phylum: Arthropoda
  • Class: Crustacea
  • Order: Decapoda
  • Family: Cancridae

Life cycle

Generalized life cycle of the Dungeness crab: Mature female crabs generally molt between May-August, and mating occurs immediately after the female has molted and before the new exoskeleton hardens. In October or November, eggs are fully developed and the eggs are extruded and fertilized. Eggs remain attached to the female's abdomen until hatching in late winter. Females are often buried in sand as the eggs develop. The larval phase, lasting about 4 months, consists of five zoeal and one megalopa stages. From May to September, megalopae settle and metamorphise into the first post-larval instar. Juvenile crabs remain in lower intertidal or shallow subtidal waters and overwinter as less than 70 mm crabs, sometimes in shallow water. As one year olds, they may grow to about 120 mm. As they grow, they tend to move into progressively deeper water. Adult crabs may live to over 10 years and reach a maximum carapace width of 230 mm and maximum weight of 2 kg.

Distribution

Common and widespread in sandy areas along British Columbia coast; range from Alaska to Mexico.

Habitat

Sandy substrate; may occur on mud and gravel; often buried just below surface of sand or in vegetation; planktonic larvae dispersed by currents; juveniles remain in intertidal and shallow subtidal hiding beneath or among plants, rocks and shell debris until 2nd summer; breeding occurs in inshore waters and females may move to deeper water to hatch eggs.

Tidal elevation

Intertidal to over 180 m subtidal depth.

Food

Bivalves, crustaceans, marine worms and fish.

Predators

Octopus, halibut, dogfish, sculpins, rockfish, birds, and larger crabs.

Growth rate

Must molt to grow; females and males sexually mature at 100 and 150 mm, respectively (2-3 yr); males reach legal size (165 mm) at 3-4 yr; females seldom reach legal size.

Drawing of female and male crabs showing the abdomen

Female and male crabs

Photo: female and male crabs showing abdomen

Female and male crabs

People living along North America’s west coast are familiar with the number of species of crab that inhabit the local waters. The crab fishery includes several species, but the primary focus is on the Dungeness crab, also known as Cancer magister.

Dungeness crab fishing has considerable importance to First Nations for food, social and ceremonial (FSC) purposes and to recreational and commercial harvesters. In 2005, the commercial fishery had a landed value of $28.8 million for 222 licensed vessels. This represented the sixth most valuable commercial fishery on the west coast of Canada (after groundfish trawl, halibut, prawn by trap, salmon, and geoduck).

Crab fishing occurs in the Fraser River delta, the Gulf Islands and inside waters of the Strait of Georgia, west of Vancouver Island (such as in the waters near Tofino), the Skeena River estuary, and Hecate Strait/McIntyre Bay.

References

Butler, T.H. 1986. Crabs, p. 54-58. In G.S. Jamieson and K. Fransis. [ed.] Invertebrate and marine plant resources of British Columbia. Can. Spec. Publ. Fish. Aquat. Sci. 91.

Dinnel, P.A., D.A. Armstrong, and O. McMillan. 1986. Dungeness crab, Cancer magister, distribution, recruitment, growth and habitat use in Lumni Bay, Washington. Univ. Wash. School Fish. Fish. Res. Inst. FRI-UW-8612, Seattle: 61 p.

Hart, J.F.L. 1982. Crabs and their relatives of British Columbia. B.C. Prov. Mus. Handb. 40: 212-213.

Jamieson, G.S. 1985. The Dungeness crab fisheries of British Columbia. Proc. Sym. Dungeness Crab Biol. and Manage. Lowell Wakefield Fish. Sym. Ser. Alas. Sea Grant Rep. 85-3: 37-60.

Jamieson, G.S., A.C. Phillips, and W.S. Huggett. 1989. Effects of ocean variability on the abundance of Dungeness crab megalopae. Can. Spec. Publ. Fish. Aquat. Sci. (in press).

Waddell, B.J. 1986. Roberts Bank crab habitat loss response study final report (1981-1985). Prep. for Roberts Bank Environ. Rev. Com., Dep. Fish. Oceans and Port of Vancouver: 53 p.

Wild, P. W., and R. N. Tasto. 1983. Life history, environment, and mariculture studies of the Dungeness crab, Cancer magister, with emphasis on the central California fishery resource. Calif. Dep. Fish Game Fish Bull. 172: 352 p.