Dungeness Crab
(Metacarcinus magister)
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Did You Know?
Female Dungeness crab in Alaskan waters starve themselves during the six or more months during which they carry eggs. Perhaps because of this extended starvation period, Dungeness in Alaska produce eggs only every other year.
General Description
The Dungeness crab, Cancer magister/ syn. Metacarcinus magister, inhabits bays, estuaries, and the nearshore coast of Alaska. The species is named after one of its representative habitats––a shallow, sandy bay inside of Dungeness Spit on the south shore of the Straits of Juan de Fuca. It is widely distributed, and can be found as far north as the Aleutian Islands and as far south as Magdalena Bay, Mexico. This crab supports commercial personal use and sport fisheries in Alaska. The Dungeness crab is a decapod, related to shrimp, lobster, and other crab. It has a broad, oval body covered by a hard chitinous shell, four pairs of walking legs and a pair of claws. This species can be distinguished from other commercially important crab (king and Tanner crab) because its legs are much smaller and shorter in relation to its body size and because the dorsal surface of its carapace is smooth and spineless.
Size and Sex Determination
The legal measurement for Dungeness crab in Alaska is shoulder width, measured across the back of the carapace between the two notches immediately anterior to the tenth anterolateral spine, also known as "notch to notch". Only male Dungeness crab may be taken and sex can be determined from the shape of the crab’s abdomen. Females have a slightly rounded abdomen while males have a triangle-shaped abdomen. This becomes very pronounced when females mature into their egg-bearing developmental stage but is slightly less obvious for younger stages. The legal size for Dungeness crab in Alaska is 6.5 inches notch to notch.
Similar Species
There are eight congeners (same genus) to the Dungeness crab. Several of these, the European edible crab, Cancer pagurus, Jonah crab, Cancer borealis, and Atlantic rock crab, Cancer irroratus, are commercially harvested. The red rock crab, Cancer productus, is harvested by sport fishermen in Oregon.
Life History
Growth and Reproduction
Dungeness crab mate from spring through fall. Males are polygamous––each male crab may mate with more than one female. This may be an important factor in maintaining the reproductive viability of this species because only male crab can be harvested. Male crab only mate with female crab that have just molted (shed their old exoskeleton). Fertilization of eggs occurs about a month after mating when the female’s shell has hardened; until this time, the female crab stores the sperm in internal pouches especially designed for this purpose. Females can store sperm for as long as 2 years and old, large females will often use stored sperm to fertilize their eggs rather than molting and mating. The female extrudes eggs through pores on her ventral surface; they are fertilized as they pass through the stored sperm and adhere to hairs on the abdominal appendages where they are carried until hatching. A large female Dungeness crab can carry 2.5 million eggs.
After hatching, crab zoea larvae are planktonic and swim away freely. Larval development takes from 4 months to as long as a year in Alaska. Six successive larval stages (5 zoea and 1 megalopa) occur before the crab molts into the first juvenile stage. Crabs grow each time they molt. During the first two years both sexes grow at similar rates, but after two years males grow more quickly than females. Sexual maturity may be reached at three years. The legal size of 6.5 inches in shell width can be reached at four to five years of age, at which time the crab will weigh between 2 and 3 pounds. A large male Dungeness crab can exceed 10 inches in shell width. The estimated maximum life span is from 8 to 13 years.
Dungeness crab are widely distributed subtidally and prefer a sandy or muddy bottom in marine waters. However, they are tolerant of salinity changes and can be found in estuarine environments. They are most abundant in waters shallower than 30 meters, but have been found as deep as 200 meters.
Feeding Ecology
Dungeness crab foraging behavior coincides with their habitat. These crab scavenge along the sea floor for organisms that live partly or completely buried in the sand. They are both scavengers and predators, and their diet can include bivalves, worms, shrimp, fish, and small crab.
Range and Habitat
Dungeness crab are distributed from the Aleutian Islands to Magdalena Bay, Mexico.
Status, Trends, and Threats
Status
Commercial fisheries for Dungeness crab are currently prosecuted in waters offshore Kodiak Island and in Southeast Alaska.
Trends
Historical harvest of Dungeness crab in Alaskan waters peaked at 15.79 million pounds in 1982. The long-term average harvest for 1966–2011calendar years is 6.48 million pounds, and the 40, 30, 20, and 10-year averages are 6.47, 6.98, 5.49, and 5.31 million pounds respectively.
Threats
The primary threats to this species include predation by sea otters, ocean acidification, habitat damage (from activities such as log transfer facilities and intertidal development), and overfishing.
Fast Facts
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Size
A legal-sized male Dungeness crab is 6 ½ inches in carapace width (shoulder width) and weighs approximately 2 pounds. -
Range
Dungeness crab are distributed from the Aleutian Islands to Magdalena Bay, Mexico. -
Diet
Dungeness crabs actively prey on small clams, worms, shrimp, and fish, but will also scavenge dead fish and invertebrates. -
Predators
Species which prey upon hard-shelled Dungeness crab include humans, sea otter, octopus and Pacific halibut; larger Dungeness crabs and staghorn sculpin are important predators on juvenile Dungeness crabs in some areas. In the soft-shell state, they are preyed upon by many additional species. -
Reproduction
Although Dungeness crabs are annual spawners throughout most of their range, females produce eggs biennially in Southeast Alaska. Mating between a hard-shelled male and a soft-shelled female occurs in late summer and sperm are stored internally in the female's 'spermathecae'. Egg masses are extruded from October through December and eggs are fertilized when they pass through the sperm mass as they exit through the genital pore. Egg clutch size increases with female size up to a maximum of about 2.5 million eggs. Eggs attach to specialized hairs on the females abdominal appendages and the female broods them while buried in the sediment in a quiescent state from December through June. Females do not eat during this period and consequently experience high post-hatching mortality. -
Fisheries
Dungeness crabs are caught commercially with pots or ring nets, and by subsistence, personal use, and sport fishermen with pots, ring nets, or snares.
Did You Know?
- Female Dungeness crab in Alaskan waters starve themselves during the six or more months during which they carry eggs. Perhaps because of this extended starvation period, Dungeness in Alaska produce eggs only every other year.
- Dungeness crab females can store viable sperm for as long as 2 years and reproduce without mating in the current season.
Uses
Subsistence fishery
Subsistence harvest of Dungeness crabs by Alaska residents is permitted in some Alaska state waters. Bag limits and seasons are generally more liberal and gear requirements less restrictive than for personal use or sport fisheries and vary by area. Crabs may be harvested by hand, dip net, using hooked or hook less hand lines, or with pots, ring nets or dive gear. Subsistence fishery catch may be shared with all members of the community.
Commercial fishery
Major commercial fisheries for this species occur in California, Oregon, Washington, British Columbia and Southeast Alaska. The Alaska Fishery and Fur Seal Industries publication made the first historical reference to the Alaska Dungeness crab fishery in 1916. This crab was first commercially canned at Seldovia in 1920. Today, Dungeness crab is processed by shore based processors, catcher processors, and floating processors. Crab product type varies; where processors are well-established and air service unreliable, crab are generally sold whole or in sections as a fresh or frozen product. However, where air service is reliable and processing capacity less so, crab are often shipped live to specialty markets where they can fetch a premium price.
Dungeness crab are caught by commercial fishers using circular pots typically baited with herring, squid, or clams. Pots are usually about 40 inches in diameter and 14 inches high. They are constructed of 3/4-inch round, steel frames wrapped in rubber tubing then covered with stainless steel wire mesh woven in 2-inch squares. Two 4-3/8" diameter escape rings are required to be built in each pot to keep the pot from filling with undersize crab.
The number of pots that can be set by a vessel and the fishing season varies by management area in Alaska.
Personal use fishery
Residents of Alaska may harvest Dungeness crab for personal use. This fishery is often incidental to recreational boat outings. Crab pots similar to those used in the commercial fishery, ring nets, diving gear, dip nets, and hooked or hookless handlines can all be used to harvest crab for personal use. Dungeness crab are sometimes stranded by minus tides and can be picked up by an observant beachcomber. Be forewarned, the mighty pincers of this crab can move quickly and catch you unaware!
Personal use anglers fish at depths between 3 and 20 fathoms where more legal sized male crab can be found. They usually bait their pots with fresh fish carcasses, the most convenient bait. The number of crab that can be kept varies, depending on the area fished. To take more than you can use is a waste and a shame, because the Dungeness crab is one of the great fringe benefits of living in coastal Alaska.
Dungeness crab are usually boiled for approximately 20 minutes. As a cautionary note, paralytic shellfish poisoning (PSP) has been found in the internal organs of Dungeness crab, therefore, butcher the crab before cooking and do not eat the internal organs including the "crab butter" (hepatopancreas). Where or when the toxin is found is unpredictable, but high levels have been found in Dungeness crab throughout Alaska. Take this one precaution and continue to enjoy one of Alaska's tastiest seafoods!
Management
The Dungeness crab fishery in Alaska has historically been managed by size, sex, and season or 3-S management. The size limit is 6.5 inches (165 mm), only males are harvested, and the fishery is closed during the female molt and mating period from mid-August to the end of September, and during most of the male molt period.
Research
While there is no active Dungeness crab stock assessment program as the species is managed by size, sex, and season, ADF&G has conducted Dungeness crab research projects in Kodiak, Central, and Southeast regions. Some more recent findings are summarized as follows.
Kodiak
Southeast
A Dungeness crab survey was conducted from 2000 through 2004. Primary survey goals were to develop a method to index crab populations and to describe variability in life history timing. A total of 3,309 commercial pots were set during March/April, June, August/September, and November/December survey periods in nine survey areas: Stikine Flats, Duncan Canal, Kah Sheets Bay, Port Camden, Berners Bay, Peril Strait, Tenakee Inlet, St. James Bay, and Seymour Canal. Depth-stratified clusters of three or four pots were set in depths from 5.5–73.2 m. Clusters had alternately open then closed escape rings, and cluster locations were selected using a systematic sampling design with random start.
Survey catch per unit effort (CPUE) was regressed against commercial harvest. Effects of depth, survey period, and year on CPUE and mean carapace width were investigated using ANOVA. Effects of survey period on female reproductive stage, shell hardness, and leg loss were investigated using contingency analyses.
The only significant predictor of harvest was June legal CPUE for Duncan Canal. Female CPUE was generally highest in deep, August/September pots, and legal male CPUE in shallow, June pots. Egg hatch was complete by June for Duncan Canal and Stikine Flats, but later elsewhere. Soft shell peaked in August/September for females but from March/April through August/September for males. Leg loss increased between June and August/September survey periods. Bycatch species composition is described.
June legal CPUE has only limited ability in indexing population, as crabs in most areas are either not completely catchable or have not yet molted into the fishery at this time. The summer season overlaps male molt period.
Get Involved
Alaska Board of Fisheries
Management of fisheries in state waters is achieved through regulations promulgated by the Alaska Board of Fisheries (BOF). The BOF holds regular meetings to revise old regulations and promulgate new ones, and takes input from stakeholders at these meetings. For BOF meeting schedules, agendas, proposals, forms, and contact information please visit our Alaska Board of Fisheries webpage.
More Resources
Alaska Board of Fisheries
Management of Dungeness crab fisheries is achieved through regulations promulgated by the Alaska Board of Fisheries (BOF). The BOF holds regular meetings to revise old regulations or promulgate new ones and takes input from stakeholders at these meetings. For BOF meeting schedules, agendas, proposals, forms, and contact information please visit our Alaska Board of Fisheries webpage
Licenses and Permits
For commercial fishing licenses and permits including crewmember, catcher-seller, direct marketers, buyers, exporters, processors, transporters, reporting, please visit our Licenses and Permits webpage.
For commercial fishing entry permits, intent to transfer forms please visit the Commercial Fisheries Entry Commission (CFEC) web site.
Fishery Openings/Updates
For commercial fishing regulation announcements, news releases, and emergency orders, please visit our ADF&G News Release page.
General Information
- Dungeness Crab — Wildlife Notebook Series (PDF 74 kB)