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

Criterion score: 0.25 info

Stock Area

Western Channel

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 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 to the levels required to produce Maximum Sustainable Yield (males below, females above). The status of the stock has not changed since the last assessment in 2014 or since the assessment carried out in 2012.

Management

Criterion score: 0.25 info

In coastal waters out to 6 miles, potting is regulated by a number of Inshore Fishery Conservation Authority (IFCA) byelaws.

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 spill over spat to outside fished grounds.

Fishermen fishing within the IPA have developed a voluntary code of conduct to promote their best practice. A minimum conservation reference or landing size of 160 mm is in force for male (cock) crabs and 150 mm for female (hen) crabs. There is also a prohibition on the landing of crab parts e.g. claws; and taking or selling egg bearing or soft shelled edible crabs. Fishing is conducted in a way which minimises negative interactions with sensitive species and habitat. For example following entanglement avoidance guidance http://www.bdmlr.org.uk/uploads/documents/resources/Creel%20Entanglement%20booklet.pdf
There is also a prohibition on the landing of crab parts e.g. claws; and taking or selling egg bearing or soft shelled edible crabs.

Capture Information

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Edible or brown crabs have been harvested from the inshore waters of South Devon for hundreds of years and supports one of the largest brown crab potting fleets in the UK.

In Devon 40% of the crab is caught within 6nm of the coast. The offshore fleet comprises vivier-equipped (live storage facility) offshore boats, each setting up to 2000 pots, and smaller inshore boats that set from 200 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 because of modernisation of traditional inshore fleets, advent of large mobile vivier crabbers, extension of fisheries to offshore grounds, and more pots being fished.

Pots are a highly selective method of fishing. Undersized animals including ‘soft’ or moulting crabs can be returned to the sea alive. However, an increase in more efficient pots, known as parlour pots, combined with mechanical hauling and increasing numbers of pots, have contributed to the potential unsustainability of the crab fishery in some 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 and other species 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 150mm inside and still 140mm outside 6nm. The increase of MLS for females or hens in 2015, brought 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 stable over the years, is indicative of the sustainable exploitation of crab in this fishery. Crabs must be landed with their claws attached. Other marine species may, but rarely, become entangled in ropes used to buoy pots.

References

Bannister, R.C.A. 2009. On the management of brown crab fisheries. Shellfish Association of Great Britain
Blythe, R.E. et al. 2004. Implications of a zoned fishery management system for marine benthic communities. Journal of Applied Ecology 41, pp. 951-961
Blythe, R.E. et al. 2002. Voluntary management in an inshore fishery has conservation benefits. Env. Conserv. 29(4), pp. 493-508
Cefas. 2017. Edible crab (Cancer pagarus) Stock Status Report 2017.
Cefas. 2014. Edible crab (Cancer pagarus) Stock Status Report 2014. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/462265/2014_Crab_assessments.pdf (Accessed 6 November 2017)
Kaiser, M.J. et al. 2007. Evidence for greater reproductive output per unit area in areas protected from fishing. Can. J Fish. Aquat. Sci. 64, pp.1284-1289
Wilson, A. (2009). Shellfish Industry Development Strategy. A Best-Practice Guide of Sea Fisheries Committee Shellfish Byelaws. Seafish.