How to Distinguish
The most similar-appearing local species is Metacarcinus
gracilis, which has similar coloration
and white claw tips
as does this species. However, it has a distinct tooth behind
widest point of the carapace
and has no spiny ridges on the carpus,
of the chelae.
It also does not grow as large.
productus, also often found intertidally and
subtidally in the
Pacific Northwest, has black tips to the dactyls
of the chelae.
Geographical Range: Occurs from Alaska to Santa Barbara, California.
Depth Range: Lives from intertidal to a depth of 230 m.
Habitat: Most common in sand or muddy-sand bottoms in subtidal regions, often in or near eelgrass beds. Often partly buries itself in the sand.
Biology/Natural History: This crab is the largest edible crab from Alaska to California, making this species important for fisheries commercially and economically. There appear to be five subspecies in California alone. The female Dungeness crab can lay up to 2.5 million eggs and can live up to at least 6 years. Females can store sperm received during one mating season and use it during the next season. This species is a carnivore that feeds on more than 40 different species including small clams, oysters, fish, shrimp, worms and according to recent studies even feeds on Velella velella nematocysts. The larvae of this species is often attached to the bells of jelly fishes and to their tentacles; these larvae feed on the gonozooids, and by doing so gain protection from pelagic fish predators and are transported to juvenile crab habitats nearshore as long as associated with the cnidarian. Dungeness crab larvae feed primarily on zooplankton, however phytoplankton are also eaten. The larvae are crepuscular migrators, being found near the surface at dawn and dusk but deeper in midday and midnight. The stage 1 zoeae are nearest the surface with later zoeal stages in deeper water. In spring, larvae of this species may be advected north along the coast as far as Alaska (Park et al., 2007). In springtime, adults of this crab can be found buried in sand or in tidepools, where it can hide and wait for its new shell to harden. On average, males will cover more ground in an hour than females, and ovigerous females move less than nonovigerous females or males. Near Vancouver Island, adults have more epibionts than do juveniles (McGraw, 2006). Common epibionts include barnacles (especially Balanus crenatus) on the dorsal surface, green, red, and brown algae (especially on the antennae), tube-dwelling polychaetes (mainly on the ventral surfaces), hydrozoans (mainly on ventral surfaces and limbs), bryozoans (especially Membranipora membranacea) on any region of the carapace. A few had sponge, tunicate, or mollusk epibionts.
Feeding in ovigerous females is greatly reduced below that of non-ovigerous females. Females are able to survive an entire winter without feeding, at least in the laboratory. Both juvenile and adult crabs may sometimes be cannibalistic.
Dudas et al. (2005) found that the common local cancer crabs Metacarcinus magister and Cancer productus (red rock crab) preferred the thin-shelled introduced varnish clam Nuttallia obscurata to the thicker-shelled clams Leukoma staminea and Venerupis philippinarum if access to all was equally easy. However, Nuttallia obscurata typically lives deeper in the sediment than do Leukoma staminea or Venerupis philippinarum. If they had to dig for them, Metacarcinus magister still ate more Nuttallia obscurata than it did of the other clam species, but C. productus' preference switched to Leukoma staminea and Venerupis philippinarum.
Jensen and Bentzen (2012) found that the egg clutches of females frequently have multiple paternity. Adult females molt once a year and mate with one male per molt. They can store sperm for up to 2.5 years.
The hoplonemertean worm Carcinonemertes errans, an ectosymbiont and egg parasite in Metacarcinus magister, is in turn eaten by a Riserius sp nemertean whose larvae have previously been classified as pilidium recurvatum (Hiebert et al., 2013)
Flora and Fairbanks, 1966
Kozloff, 1987, 1996
Smith and Carlton, 1975
Airriess, C., and McMahon, B., 1994. Cardiovascular Adaptations Enhance Tolerance of Environmental Hypoxia in the crab Cancer magister. Journal of Experimental Biology 190: 23-41
Bernatis, J., Gerstenberger, S., McGaw, I., 2007. Behavioural responses of the Dungeness crab, Cancer magister, during feeding and digestion in hypoxic conditions. Marine Biology, Vol. 150, pp. 941-951
Curtis, D. L. and I. J. McGaw, 2008. A year in the life of the Dungeness crab: methodology for determining microhabitat conditions experienced by large decapod crustaceans in estuaries. Journal of Zoology 274:4 pp. 375-385
Curtis, Daniel L. and Iain J. McGaw, 2011. A possible feeding control mechanism in Dungeness crabs during hyposaline exposure. Journal of Crustacean Biology 31:2 pp. 313-316
Dudas, Sarah E., Iain J. McGaw, and John F. Dower, 2005. Selective crab predation on native and introduced bivalves in British Columbia. Journal of Experimental Marine Biology and Ecology 325:1 pp 8-17
Graham, R., 1985. A model for L-lactate binding to Cancer magister hemocyanin. Comp . Biochem. Phys., Vol. 81, pp. 885-887
Hankin, D.G., N. Diamond, M.S. Mohr, and J. Ianelli, 1989. Growth and reproductive dynamics of adult female Dungeness crabs, Cancer magister in northern California. Journal du Conseil Permanent International pour l'Exploration de la Mer 46: 94-108
Hobbs, R.C. and L.W. Botsford, 1992. Diel vertical migration and timing of metamorphosis of larvae of the Dungeness crab, Cancer magister. Marine Biology 112: 417-428
Jensen, Pamela C. and Paul Bentzen, 2012. A molecular dissection of the mating system of the Dungeness crab, Metacarcinus magister (Brachyura: Cancridae). Journal of Crustacean Biology 32:3 pp 443-456
Jensen, P.C., J.M. Orensanz, and D. Armstrong, 1996. Structure of the female reproductive tract in the Dungeness crab (Cancer magister) and implications for the mating system. Biological Bulletin 190: 336-349
Lough, R.G., 1976. Larval dynamics of the Dungeness crab, Cancer magister off the central Oregon coast, 1970-71. Fish. Bull. 74: 353-375
Losey, Robert J., Sylvia Behrens Yamada, and Leah Largaespada, 2004. Late-Holocene Dungeness crab (Cancer magister) harvest at an Oregon coast estuary. Journal of Archaeological Science 31: pp. 1603-1612
McConnaughey, R.A., D.A. Armstrong, B.M. Hickey, and D.R. Gunderson, 1994. Interannual variability in coastal Washington Dungeness crab (Cancer magister) populations: Larval advection and the coastal landing strip. Fish. Oceanogr. 3: 22-38
McGaw, I., 2005. Burying behavior of two sympatric crab species: Cancer magister and Cancer productus. Scientia Marina, Vol 69, pp. 375-381
Iain J., 2006. Epibionts of sympatric species of Cancer
crabs in Barkley Sound, British Columbia. J. Crustacean
Park, Wongyu, David C. Douglas, and Thomas C. Shirley, 2007. North to Alaska: Evidence for conveyor belt transport of Dungeness crab larvae along the west coast of the United States and Canada. Limnology and Oceanography 52:1 248-256
Frederick R. and Peter K.L. Ng, 2012. What is Cancer?
Journal of Crustacean Biology 32:4 pp. 665-672
Stillman, Jonathon H., John K. Colbourne, Carol E. Lee, Nipam H. Patel, Michelle R. Phillips, David W. Towle, Brian D. Eads, Greg W. Gelembuik, Raymond P. Henry, Eric A. Johnson, Michael E. Pfrender, and Nora B. Terwilliger, 2008. Advances in crustacean genomics. Integrative and Comparative Biology 48:6 pp 852-868
Thomton, Jamie D., Sherry L. Tamone, and Shannon Atkinson, 2006. Circulating ecdysteroid concentrations in Alaskan dungeness crab (Cancer magister). Journal of Crustacean Biology 26:2 pp 176-181
Sulkin, S. and G.L. McKeen, 1989. Laboratory
and duration of individual zoeal stages as a function of temperature in
the brachyuran crab Cancer magister.
Marine Biology 103: 31-37
General Notes and Observations: Locations, abundances, unusual behaviors, etc.:
Distinguishing Characteristics of Metacarcinus
The many epibiont
barnacles encrusting this individual, found in a tidepool at Kalaloch
2009, implies that it has been some time since the animal has
These crabs spend a significant amount of time buried in the sand with
only their face projecting. This fact can be seen in this
by noting that the barnacles do not encrust the back end, which is
buried and without access to oxygen or food, but do encrust the front
which projects from the sand. Photo by Dave Cowles, July 2009
Regardless of how it may look, this is NOT a crab! See below for why.
Even though the exoskeleton looks perfect, the occupant has backed out and left! This is just a molt or exuvium. Crabs molt the entire exoskeleton, including the lining of the gills (visible above), parts of the gut lining, the covering of the eyes, etc.
Crabs are quite vulnerable when they molt because not only are they struggling to get out of their old exuvium but their new exoskeleton is extremely soft and vulnerable. This crab died halfway through a molt because it was attacked by another crab when it was defenseless. Note the soft folds in the new exoskeleton, which is as soft as warm butter..
Here is another photo of the underside of a male.
Authors and Editors of Page:
Janisse Maxwell (2002): Created original page..
Edited by Dave Cowles 2002, 2005, 2006, 2010, 2011
Edited by Hans Helmstetler 10-2002