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Crab, brown or edible

Cancer pagurus

Method of production - Caught at sea
Capture method - Pot
Capture area - North East Atlantic (FAO 27)
Stock area - Wales
Stock detail - Pembrokeshire
Certification -
Fish type - Shellfish

Sustainability rating Click for explaination of rating

This fish, caught by the methods and in the area listed above, is a good sustainable fish to eat. Click on the rating icon above to read more and on the alternatives tab below to find similar fish to eat.


Sustainability overview

The status of the stock in the Celtic Sea is good, approaching the level associated with Maximum Sustainable Yield. Exploitation levels are moderate for females and likely to be sustainable but above the target MSY level. Avoid eating crabs below the minimum landing size (140 mm in Wales) and crab claws, unless it is certain they have been removed from the crab body after landing. Egg-bearing or "berried" females should be avoided at all times to allow them to spawn.

Biology

The brown crab is commonly found in the North Atlantic Ocean, North Sea, less so in the Mediterranean. It is the heaviest British crab and easily identified by a characteristic pie-crust edge to the carapace or shell. They are found in waters down to 100 m. Brown crabs are highly fecund. Mating activity peaks in the summer when the female has moulted with spawning occurring in the late autumn or winter. Egg carrying females are largely inactive over the winter brooding period before the eggs hatch in the spring and summer. Between 250,00 to 3,000,000 eggs are held by the female for 8 months until they hatch into planktonic larvae. After around five weeks in the plankton, the crab larvae settle on the seabed. Juvenile crabs settle in the intertidal zone and remain in these habitats for 3 years, until they reach 6-7 cm carapace width, at which time they migrate to subtidal habitats. The crab is encased in a hard, rigid shell, which, like other crustaceans, has to be shed at intervals to permit growth. Moulting takes place at frequent intervals during the first years of a crab's life, but only every two years after it is grown and this is mirrored by a slowing of growth rate. Growth is dependent on the frequency of moulting as well as the increase in size on each moulting occasion and it typically takes about four or five years for a juvenile crab to grow to commercial size. They can grow up to about 25 cm carapace width, with the larger specimens inhabiting deeper water. Growth rate varies between areas, and animals will typically reach a minimum landing size of 140mm carapace width at 4 to 6 years old. Environmental variables e.g. sea temperature related to geographical area and fishing pressure affect the size of maturity with animals in more northerly latitudes growing and maturing more slowly. Minimum landing sizes vary around the British coast from 150mm in the Western Channel to 115 mm in Norfolk for example. Edible crabs can live for up to 100 years but average age is around 25 to 30 years, and sexual maturity is reached after approximately 10 years, but can be as early as 3 to 4 years. Female brown crabs in Scottish waters typically mature between 130 and 150 mm CW. In Orkney research has shown that sexual maturity can be reached at 115 to 120 mm. The sex of a brown crab can be determined by the shape of the abdomen; the males being narrow and the females being broad and rounded for carrying eggs. Stock boundaries for edible crab remain poorly understood and both sexes move quite widely at times; females in particular have been shown to travel large distances in relation to spawning activity.

Stock information

Stock area
Wales

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Stock information
There is no assessment of Brown crab stocks by ICES in the North East Atlantic. Stock assessments in England and Wales are carried out by Cefas. For these assessments scientists advise an optimum exploitation rate (fishing mortality rate or FMSY) that will produce a spawning stock biomass of 35% of the virgin stock. This is considered to correspond to Maximum Sustained Yield (MSY). To avoid risk of depletion the stock should not be fished at a rate (Fishing mortality limit or Flimit) which would result in a stock below 15% of its virgin stock biomass. The most recent stock assessment for the Celtic Sea (Area VIIg) in 2011 concludes that fishing mortality and spawning stock biomass have been inside safe biological limits for the past 3-4 years and appear stable, though above the level that will produce MSY. Landings are at an all-time high. Crabs will have 1-2 spawning opportunities before legal removal.

Management

In April 2010 Welsh Government assumed full responsibility for inshore fisheries management in Wales. Prior to this the inshore fisheries were regulated by two separate Sea Fisheries Committees (SFC) established under the Sea Fisheries Regulation Act 1966, each with their own geographically relevant set of byelaws. Crustacean fisheries are the mainstay of the Welsh fishing industry. A review of all fisheries legislation in Wales commenced in January 2012 with the remit to review all items to ensure they are fit for purpose. Given the importance of the crustacean fishery, this was one of the first fisheries to be considered, and a review of their management provisions is currently taking place.

Fisheries in Wales are managed by various sectors of the Welsh Fishermen's Association, who decide upon Sea Fisheries Legislation, or 'by-laws', which are then implemented by the Welsh Assembly Government. In Wales, unlike the rest of the UK, fisheries regulations are able to extend out to the 12 mile limit which allows for any management measures adopted to be more effective.

Crab stocks are managed primarily through fishing effort limitation and technical conservation measures. Measures include a Minimum Landing Size (MLS) for crabs of 140mm and a ban on the landing of crab claws.

The practice of "harvesting" crab claws - that is removing either one or both claws then returning the live animal to the sea - has previously been considered justifiable due to crabs ability to naturally autonomise (lose) and then regenerate lost or harvested claws. Tissue damage however is much greater in a crab when a claw is deliberately removed through harvesting compared to when a limb is shed via autotomy. The practice of harvesting crab claws has been legal in the United Kingdom since the revocation of the Crab Claws (Prohibition of Landing) Order (1986) in 2002.

Capture information

Most crabs and lobsters are captured in baited pots (also known as traps or creels), but they can also be taken in trawls and static nets such as gill nets or tangle nets. Pots are either top opening (inkwell pot) or side-opening with a retaining chamber (parlour pot). In European waters, pots are fished individually or in strings (fleets) of up to 100 pots, at each end of which is an anchor and buoy. Both brown crabs and spider crabs are taken as bycatch in static gear such as gill nets with the latter being most common. As it is difficult to remove the animal's whole from the nets they are often de-clawed with only the claws are retained. In some areas net fishermen employ 'crab smashers' to simply crush the crabs out of the nets.tissue damage, which is much greater than when a limb is shed via autotomy. Both brown crabs and spider crabs are taken as bycatch in static gear such as gill nets with the latter being most common. As it is difficult to remove the animal's whole from the nets they are often de-clawed with only the claws are retained. In some areas net fishermen employ 'crab smashers' to simply crush the crabs out of the nets. Crab claws are commonly landed by mobile gear vessels where they are captured as bycatch. Under EU legislation (EC Technical Conservation Regulation No 850/1998) a maximum of 75kg of detached crab claws may be retained on board a fishing vessel and landed. Crab claws of the Brown crab account for up to 20% of total body weight and therefore 75kg of claws equates to 375 kg of whole crabs.

Read more about capture methods


References
ICES. 2014. Interim Report of the Working Group on the Biology and Life History of Crabs (WGCRAB), 22-24 April 2014, Tromso, Norway. ICES CM 2014/SSGEF:12. 35 pp. http://www.ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/SSGEF/2014/01%20WGCRAB%20-%20Report%20of%20the%20Working%20Group%20on%20the%20Biology%20and%20Life%20History%20of%20Crabs.pdf; http://fisheries-conservation.bangor.ac.uk/documents/CrustaceanBylawReviewEvidenceReportFinal.pdf; http://www.seafish.org/media/publications/SeafishResponsibleSourcingGuide_CrabsLobsters_201309.pdf

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