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 B.C.
coast.
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.
FISHERY
Supports valuable commercial, Native and sport crab fisheries;
minimum legal size is 165 mm carapace width; 1986 total crab commercial
catch was 1,321 t valued at $5.7 million.
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.
|
