Product Code Database
The Dungeness crab ( Metacarcinus magister)the naming convention recognised by WoRMS makes up one of the most important seafood industries along the west coast of North America. Its typical range extends from Alaska's Aleutian Islands to Point Conception, near Santa Barbara, California. Dungeness typically grow at their widest point and inhabit eelgrass beds and sandy bottoms. Its common name comes from the Dungeness Spit in the Strait of Juan de Fuca, Washington state, United States, which shelters a shallow bay inhabited by the crabs.
Crabs must periodically molt to grow; this process is called ecdysis. Molting has the ability to regenerate lost limbs, although they will be smaller the first molt after loss. During a molt, the shell will separate where the carapace and abdomen meet. This allows the crab to exit the old shell. Once outside the old shell the soft new shell will fill with water and the crab will become 15-25% bigger than its original size. During the first few weeks after molting, the crab is very vulnerable due to the softness of its shell; the shell will not fully harden for two months after molting. For the first two years of a crab's life, it will molt six times a year. In the third year, males molt twice and females molt once. After that, all crabs will molt once a year, with females molting in the spring and males molting in the summer. Dungeness typically live five years and measure at the end of their life. However, the crabs can live up to eight years on the west coast of the US and have been seen to reach 13 years in the northern reaches of their range. At these ages, maximum female size can be up to and maximum male size up to .
M. magister prefers to eat clams, other , and small fish, but is also an effective scavenger. Their scavenging habits can even lead them to eat other Dungeness.
A genetic analysis of adult Dungeness crabs indicated that there is one population across the California Current System, but it is likely that interannual variation in physical oceanographic conditions (such as Ocean current) influence larval recruitment among regions, causing genetic diversity to change through time.
Young crabs are free-swimming after hatching and are diel vertical migrators that can be found at depths up to during the day. The crabs go through five zoeal larval stages and one megalops stage before settling to the bottom in their first juvenile stage. The free-swimming stages typically take three months to four months, although in Alaska crabs may remain larvae for up to a year. Sexual maturity is reached after about 12 molts or two years. The crab's typical lifespan is 8-13 years.
The typical range of the Dungeness extends from Alaska's Aleutian Islands to Point Conception, near Santa Barbara, California. Occasionally, the crab can be found as far south as Magdalena Bay, Baja California Sur, Mexico.
In all areas where Dungeness are fished a license is required for harvest whether it is commercial or recreational. Commercially in Oregon and Washington, a logbook that is to be turned in at the end of the season is additionally required. Trip limits (how many crabs someone can take in one day) and pot limits (how many pots someone can have in the water at once) are set for both commercial and recreational crabbing in all areas. In Washington state, bi-weekly crab condition testing occurs and if the crabs are found to be too soft shelled, the limits will be reduced. The crabbing season is generally open from November or December to late August or early September. Crabbing is closed in the fall to protect soft-shelled crabs.
Some recreational fishermen use Crab trap or hoops to harvest Dungeness. These hoops sit flat on the bottom and are pulled up periodically, trapping any crabs in the hoop at the moment. Most crabs, however, are caught in Crab trap attached to a small buoy. Pots are baited in the center and have one way door flaps for the crabs to enter through. Crab pots in all regions are required to have Biodegradation rot cord attaching the pot and the buoy in case they are lost. Pots in Alaska are additionally required to be made with biodegradable twine so that the pot will fall apart if lost. In pots of all regions, escape rings are required to allow the escape of undersized and female crabs. In California, Oregon, and Washington these are required to be ; in Alaska rings are required to be ; in Canada they are required to be . Pots are typically set in waters deep.
The legal size of crabs is in California, Oregon, and Washington for commercial fisheries and in Alaska and Canada. In recreational fisheries, the minimum size in California and Oregon is , while Washington is . In Alaska, Washington, Oregon, and California (commercial) fisheries, only male crabs are allowed to be harvested. Crabs typically reach legal size at three to five years depending on location (Alaska has much slower growth).
The Dungeness fishery has been closed in the Cook Inlet, Alaska, since 1991; Yakutat, Alaska, and the Prince William Sound, Alaska since 2000;; and the southern region of the Puget Sound, Washington since 2018.Friedrich, Ed (2023-06-22). " State keeps South Sound closed to crabbing for sixth summer". Gig Harbor Now. In Alaska, these closures are due to population decreases likely caused by increased otter predation and environmental shifts. In Washington state, the closures are due to population decreases caused by unknown factors.
Due to catch averages staying consistent, it is assumed populations are healthy, but in reality very little is known about Dungeness crab populations. In California, Alaska, and Washington, research is minimal and information about populations is assumed from catch records. In Canada, two out of seven crabbing areas are examined twice every year. The other areas are studied inconsistently and usually in relation to specific research questions. In Oregon, monitoring programs are in place for mating success, genetic structure, population structure, and discard mortality.
The effect of the fishery on other species is variable. The effects on benthic species and bycatch are relatively unknown, although the effects are assumed to be negligible for both. In Alaska and Canada there is no known effect on any other species. In Washington, Oregon, and California, humpback whales are known to be highly affected with a high of 19 humpbacks entangled in crabbing line in 2016. In California, leatherback turtles, orcas, and blue whales have also been known to be impacted. In recent years entanglements of all species have increased; this is attributed to increased reporting and changes in these species' migration due to changes in prey abundance as a result of climate change. It is important to note that entanglements are lower than they could be due to the timing of the crabbing season: the first six weeks of the crabbing season (when most fishing occurs) happens before the migration of many species. The high seen in 2016 was likely due to a late opening of the season because of toxic algal blooms.
Ghost net from lost equipment is a problem in the industry, the scale of which is generally unknown. It is estimated that 10-20% of gear is lost each year with 7.5-32.5% of that ghost fishing. Ghost fishing can entangle marine mammals, cause crab death, and harm the ecosystem. Additionally, lost gear may ghost fish in places far from their original spots due to currents and tides; buoys from lost pots in Oregon were recovered four years later in the Hawaiian islands.
Overall, Seafood Watch has given the Dungeness crab a sustainable seafood rating of "Good Alternative" meaning they are okay to buy but be sure to be aware of potential concerns.
About one-quarter of the crab's weight is meat. Dungeness crabs can typically be purchased either live or cooked. A humane way to kill a live crab is to: 1) stun the crab by submerging it in ice water for several minutes, 2) flip the crab onto its back, and 3) drive the tip of a small pick about an inch below the center of its mouth. However, many cook live crabs by simply dropping them into boiling salt water. The crab then is allowed to cook for 15 minutes, after which time the crabs are removed and placed into cold water to cool and then cleaned. Cleaning the crab consists of removing the shell, scooping out the gills and intestines, and separating the legs and claws from the body. When removing the shell there will be a yellow substance, called crab fat or crab mustard (which is not fat, but actually the Tomalley) and is used in many dishes. Another method of preparing crab is called half-backing. Half-backing is done by flipping the crab upside down and chopping it in half (from head to "tail"), after which the guts and gills can be scooped or hosed out. Many consider half-backing to be superior to cooking the entire crab, because the meat is not contaminated by the flavor or toxins of the guts. Half-backed crabs boil faster or can be quickly steamed instead of boiled. Some common tools for removing crab meat from the shell are a crab cracker and a shrimp fork.
A 2020 study funded by NOAA showed that larval crabs are being affected by ocean acidification." Another potential harm related to Climate change is red tides.
Another threat to the Dungeness crab is an invasive species called the Carcinus maenas ( Carcinus maenas..) The green crab outcompetes the Dungeness Crab for food and habitat.
The annual Dungeness Crab Festival is held in Port Angeles, Washington, each October.
Notes
Further reading
|
|
