Crab, brown or edible

Cancer pagurus

Method of production — Caught at sea
Capture method — Pot or creel
Capture area — North East Atlantic (FAO 27)
Stock area — Western Channel
Stock detail — VIIe
Picture of Crab, brown or edible

Sustainability rating two info

Sustainability overview

The status of the stock in the Western English Channel is good with spawning stocks around the level required to produce Maximum Sustainable Yield. Exploitation levels are moderate to low and around the levels required to produce Maximum Sustainable Yield. Avoid eating crabs below the minimum landing size (13-14cm in most areas of the UK) 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

Western Channel

Stock information

Brown crab is widely distributed in coastal waters of the Mediterranean, Atlantic, English Channel and North Sea. There are five Crab Fishery Units (CFU) defined for England. Cefas publishes stock status reports for each of the areas every 2 years. The status of the stock of edible crab in the Western English Channel is good with spawning stocks around the level required to produce Maximum Sustainable Yield. The exploitation levels are close (males below, females above) to the levels required to produce Maximum Sustainable Yield. The large minimum landing size ensures that multiple spawning events are possible before the individuals can be removed by the fishery. The status of the stock has not changed since the last assessment in 2012.

Management

There are a range of measures available for the management of crab stocks including but not limited to: licensing; limited entry; closed seasons and areas; minimum and maximum landing sizes; prohibitions on landing of berried crabs, soft crabs or crab parts; use of crabs as bait; trap limits and size; use of escape vents; biodegradable panels; vessel size and power; and use of VMS or vessel monitoring systems, which may be introduced at the EU or national and regional or local level. A restrictive licensing scheme for shellfish was introduced in UK waters in 2004, and increased monitoring of landings and effort was introduced in 2006 for boats under 10m in length in all areas of the UK. EU legislation sets a minimum landing size of 130mm for crabs in the North Sea south of 56 degrees N. It also restricts the proportion of the crab landings that is detached claws, caught by pots or creels, to less than 1% by weight of total catch. A bycatch limit of no more than 75kg per day of crab claws taken by other gear types can be landed. National legislation restricts the number of shellfish licences available (in England and Wales) and also prohibits landing of berried and soft crabs. A derogation to the EU legislation sets an MLS of 115mm in the Eastern IFCA area. In coastal waters out to 6 miles, potting is regulated by a number of Inshore Fishery Conseration Authority (IFCA) byelaws. This stock represents just one of six Crab Fishery Units (CFU) that have been defined for England and Wales. Southern IFCA bylaws apply from Hayling Island to Lyme Regis, Devon and Severn IFCA between Lyme Regis and Rame Head and Cornwall IFCA from Rame Head to the border of this CFU (part of their region). The Isles of Scilly IFCA are responsible for the coastal area around the Scilly Isles and out to 6nm. There is no regional byelaw for limiting the number of pots used in the Western English Channel crab fisheries. The use of towed gear is restricted in S Devon and mid-Channel Potting Boxes. There are more stringent minimum landing sizes (MLSs) - off Cornwall, Devon and the Scilly Isles the UK law is for an MLS of 160mm for males and 140mm for females. Cornwall IFCA applies an MLS of 150mm for females. Pot in use are fitted with escape gaps. The use of crab as bait is permitted.

Capture Information

Brown (or edible) crab is the most valuable crab species exploited around the coasts of England and Wales with landings in 2011 of around 12,000t worth in excess of 19 million pounds at first sale. Pots are a highly selective method of fishing. Undersized animals can be returned to the sea alive. However, many pots in use now (known as parlour pots), combined with mechanical hauling and increasing numbers of pots, have contributed to the potential unsustainability of the fishery in many areas. The legal minimum landing size for brown crab in European waters ranges from 14cm (north of 56 degrees North) to 11.5cm (Eastern IFCA District) depending on area of capture. Turtles may, but rarely, become entangled in ropes used to buoy pots.

References

Edible crab (Cancer pagarus) Cefas Stock Status Report 2014 https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/462265/2014_Crab_assessments.pdf