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 — Celtic Sea
Stock detail

VIIg


Picture of Crab, brown or edible

Sustainability rating three info

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 (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

Criterion score: 0.75 info

Stock Area

Celtic Sea

Stock information

The brown crab (Cancer pagurus) and the European lobster (Homarus gammarus) are both highly valuable shellfish species in the North eastern Atlantic. Both species are typically caught using baited traps.

Brown crab is widely distributed in coastal waters of the Mediterranean, Atlantic, English Channel and North Sea.

Availability of fishing activity data and the similarity of their respective biological attributes has led to fisheries scientists using the same or similar stock assessment methodologies for both species. Furthermore, the same fisheries scientists within each fisheries institute are often responsible for both crab and lobster stock status assessments.

The Centre for Environment Fisheries and Aquaculture Science (Cefas) provides management advice on the stocks of Cancer pagurus and Homarus gammarus in English and Welsh waters based upon the assessments performed every two years.

Cefas use three datasets to assess brown crab and lobster fisheries in England and Wales: landings, fishing effort and size distribution of landings. The landings and fishing effort data for over 10-meter vessels come from mandatory EU logbooks. For under 10-meter vessels the landings data are collected from first sales notes and the fishing effort from Monthly Shellfish activity returns (MSARs). Scientific officers visit ports frequently to collect size data. Additional size data have also been incorporated from local Inshore Fisheries and Conservation Authorities (IFCAs) since 2013.

The status of the stock of female Edible Crab in the Celtic Sea is 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. The status of the stock has not changed since the last assessment in 2014.

Management

Criterion score: 0.5 info

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 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 several Inshore Fishery Conservation Authority (IFCA) byelaws. This stock represents just one of five Crab Fishery Units (CFU) that have been defined for England. Cornwall IFCA bylaws apply between the southern limit of this CFU and Marsland Mouth (part of their area) and Devon and Severn IFCA on the north Devon and Somerset coasts (part of their region). There is no regional byelaw for limiting the number of pots used in the Celtic Sea crab fisheries. Pots in use are fitted with escape gaps. The use of crab as bait is permitted. A permit scheme is in operation in the Cornwall IFCA area.

Capture Information

Criterion score: 0 info

Pots are a highly selective method of fishing. Undersized animals including ‘soft’ or moulting crabs 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.

References

Cefas. 2017. Edible crab (Cancer pagarus) Stock Status Report 2017.
Cefas. 2014. Edible crab (Cancer pagarus) Stock Status Report. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/462265/2014_Crab_assessments.pdf (Accessed 6 November 2017)