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 — Devon Inshore Potting Area
Picture of Crab, brown or edible

Sustainability rating two info

Sustainability overview

Potting is a low impact method of fishing - avoid eating brown crab caught by other methods such as by dredge, net or beam trawl. The Inshore Potting Agreement area crab fishery has stable levels of effort, strong and effective harvest controls, and is managed in a manner which is consistent with objectives of sustainable exploitation. The IPA also provides a unique opportunity for fisheries management in that the No Trawl Area has created a de facto Marine Protected Area (MPA). The designation of the area, within the Skerries Marine Conservation Zone (MCZ), is acknowledgement of it's conservation importance. Protection of the grounds from trawling over the years has resulted in healthy and diverse reefs. Choose crab pot-caught from the Inshore Potting Agreement Area in Devon. 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. EC 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 which is detached claws caught by pots or creels to less than 1% by weight of total catch. A by-catch 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 EC 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. Measures to cap fishing effort include freezing existing pot numbers for each vessel and reducing pot efficiency for example. The view is that a ban on parlour pots would significantly reduce potting effort. There are no official management measures relating to brown crab except for those imposed by the Inshore Fishery Conservation Associations (IFCAs) within 6 miles of the coast. These measures include a limit on boat size to under 15 metres, Minimum Landing Size (MLS) and escape gaps in all soft eyed pots. Within the Devon and Severn IFCA an Inshore Potting Agreement prohibits trawling in a designated static-gear area off Start Point. Implemented in 1978 to restrict the use of towed gears in inshore areas that had traditionally been used by static-gear (pot and net) fishers the IPA is a zoned fishery management system covering some 500 square kms. Since 2002 the previous voluntary agreement is now enforced by Government legislation. Although established to reduce conflict between mobile and static fishing gears the closure has created positive environmental benefits such as increased biodiversity and abundance of benthic (bottom dwelling) species. Benefits to other fisheries are also well documented. For example increased fecundity of scallops in the no-trawl area provide more spillover spat to outside fished grounds. Fishermen fishing within the IPA are developing a voluntary code of conduct to promote their best practice.

Capture Information

Edible or brown crabs have been harvested from the inshore waters of South Devon for hundreds of years. The South Devon coastline supports one of the largest brown crab potting fleets in the UK. The highest number of potting vessels is deployed in the Western Channel. Also the highest landings of brown crab are from this area. In Devon 40% of the crab is caught within 6nm of the coast. The fleet comprises vivier-equipped (live storage facility) offshore boats, each setting up to 2000 pots, and smaller inshore boats that set from 350 to 1200 pots each. It also includes seasonal open boats setting between 50 and 100 pots each. There are approximately 25-30 full-time static-gear boats that work within the Inshore Potting Agreement (IPA) area. Landings of brown crab from the Western Channel have increased markedly since the start of the fishery in the 1970s and 80s. Potting effort has increased as a result of modernisation of traditional inshore fleets, advent of large mobile vivier crabbers, extension of fisheries to offshore grounds, and more pots being fished. In 2011 there were 501 UK vessels fishing for crabs and lobsters in the Western Channel (VII) area. 4,445 tonnes of crabs were taken worth 6.8 m. Of this around 2,000 tonnes were from within the IPA. 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. Within the IPA parlour pots are rarely used in favour of the less-efficient inkwell pot. Where parlour pots or creels with soft eyes are used there is a byelaw unique to the area that requires escape gaps are fitted to increase their sustainability by allowing undersize or immature crustaceans to escape, reach sexual maturity and contribute to the stock before they are landed. The legal minimum landing size for brown crab in European waters ranges from 14cm (north of 56 degrees North) to 11.5cm (Eastern Sea Fisheries District) depending on area of capture. In Devon, the MLS (now called minimum conservation reference size) for males or cocks is 160mm both inside and outside 6nm. Hens are still 140mm outside 6nm. The increase of MLS for females or hens brings Devon in line with Cornwall, who increased the MCRS for their inshore waters some time ago. Devon and Cornwall therefore have the largest minimum landing size for hens of 150mm. The landing of berried or egg bearing hens is also prohibited in Devon and nationally. The size of both male and female crabs found in the IPA has been found to be consistently high (an average of 150 mm+ for females and 170 mm for males). This, combined with the fact that fishing effort in the area has remained fairly stable over the years, is indicative of the sustainable exploitation of crab in this fishery. Crabs must be landed with their claws attached. Turtles may, but rarely, become entangled in ropes used to buoy pots.

References

On the management of brown crab fisheries. Dr RCA Bannister (2009) SAGB;
Shellfish Industry Development Strategy. A Best-Practice Guide of Sea Fisheries Committee Shellfish Byelaws. A Wilson (2009). Seafish;
Cefas (2009); Evidence for greater reproductive output per unit area in areas protected from fishing. MJ Kaiser et al. Can. J Fish. Aquat. Sci. 64:1284-1289 (2007);
Implications of a zoned fishery management system for marine benthic communities. RE Blythe et al. Journal of Applied Ecology (2004) 41:951-961;
Voluntary management in an inshore fishery has conservation benefits. RE Blythe et al. Env. Conserv.(2002) 29(4):493-508
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