Crab Fishery - Pacific Region

Dungeness Crab Biology

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.

ECOLOGICAL DATA

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.

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.
 

MANAGING THE CRAB FISHERY - TIME FOR A CHANGE?

The primary management tool for all Dungeness crab fishing is size limits. No Dungeness crab smaller than 165mm (measured in a straight line through the widest part of the carapace, from outside the points) can be retained by any harvester (regulation in place since 1914). The minimum size limit ensures that crabs are protected until they become sexually mature and have an opportunity to spawn at least once prior to being harvested. Other regulations exist to support conservation, including limited licensing (e.g., 222 commercial licences and tidal water sport fishing licences ); use of biological escape mechanisms (e.g., rot cord); release of female and soft-shell crab, and gear restrictions (e.g., limits on the number of commercial trap licences). Also, there are seasonal commercial fishery closures to allow access by First Nations for FSC purposes, and recreational harvesters.

While the current approach meets basic conservation needs, other Department of Fisheries and Ocean’s objectives and the desires of harvesters may not always be met. There continue to be several issues of concern. At times, excessive handling of undersized, female and soft-shell crab occurs, resulting in mortality that may reduce abundance. Many First Nations report difficulty catching legal size crab for FSC purposes, and recreational harvesters are dissatisfied with the lack of available legal size crab. Commercial harvesters can experience low catch rates and poor economic returns in some areas and need ways to adapt.

CRAB MANAGEMENT REVIEW AND REFORM

DFO has launched a consultation process to develop a new management framework in response to these challenges and to improve management of the crab fishery. Conservation remains the overall objective. However, through consultations with stakeholders, a new management framework can help to improve crab abundance and provide stable access to the resource, while meeting the needs of First Nations as well as commercial and recreational harvesters.

Consultation began with the release of a discussion paper in June 2007 and will continue through 2008. The consultation will involve First Nations, recreational and commercial harvesters, and others with an interest in the crab resource.

FOR FURTHER INFORMATION:

More information on the review and reform process is available on the following website.
www-comm.pac.dfo-mpo.gc.ca/pages/consultations/consult_e.htm

The website will be updated with additional information (e.g., meeting dates, reports) as they become available. It also includes a vehicle to send your questions, comments, and suggestions to the Department.

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.