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 — Scotland
Stock detail

Shetland


Certification

Marine Stewardship Council (MSC)


Picture of Crab, brown or edible

Sustainability rating three info

Sustainability overview

The SSMO Shetland inshore brown crab fishery is certified as a responsible fishery by the Marine Stewardship Council (MSC). 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 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

Scotland

Stock information

The principal fishing areas for brown crab in Scotland are the Hebrides, Orkney, Sule, East Coast, Papa and South Minch; landings from these areas accounted for around 80% of the total in recent years.

For assessment purposes, the Scottish creel fishing grounds are divided into 12 assessment areas. Regional assessments of crab stocks around Scotland are currently based on length cohort analyses (LCA) and use reported landings data and market sampling length frequencies collected by Marine Scotland Science.
In Shetland, fishing mortality for male crabs was estimated to be above FMSY too high, while assessment results for Shetland females were inconclusive.
In many of the assessment areas, a higher yield and biomass per recruit in the long term could potentially be obtained by reducing the level of fishing mortality (effort).

Management

Criterion score: 0.25 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 (150 mm) 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.
The Shetland crab fishery is managed by a regional Regulating Order for Shetland and this is administered through a distinct management body, the Shetland Shellfish Managment Organisation. The body has the powers to enforce submission of catch and specific area for landings; Minimum Landing Sizes; Real time closures of areas; marking of gear; maximum vessel size. Additional powers can be excercised by the group if necessary e.g. fishery closure. Since April 2012 the fishery has been fully certified as a Marine Stewardship Council (MSC) fishery. Certificate expires 30th November 2017. Re-assessment of the fishery began in 2016.

Capture Information

Criterion score: 0 info

Pots are a highly selective method of fishing. Undersized animals can be returned to the sea alive.

References

ICES. 2017. Report of the Working Group on the Biology and Life History of Crabs (WGCRAB), 1-3 November 2016, Aberdeen, Scotland, UK. ICES CM 2016/SSGEPD:10. 78 pp. http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/SSGEPD/2016/01%20WGCRAB%20-%20Report%20of%20the%20Working%20Group%20on%20the%20Biology%20and%20Life%20History%20of%20Crabs.pdf (Accessed 13 November 2017)
Jones, G. et al. 2010. Brown crab (cancer pagarus) migrations off the Northern Scottish Coast. Scottish Industry Science Partnership Report 02/10
MSC. 2012. The SSMO Shetland inshore brown and velvet crab, lobster and scallop report - Public Certification Report
Scottish Statutory Instruments 2009. No. 443. Sea Fisheries. The Shetland Islands Regulated Fishery (Scotland) Order 2009
http://www.gov.scot/Publications/2016/03/2385/3 (Accessed 6 November 2017)
The Specified Crustaceans (Prohibition on Landing, Sale and Carriage) (Scotland) Order 2017 http://www.legislation.gov.uk/ssi/2017/455/contents/made (Accessed 28 February 2018)
C Mesquita, T Miethe, H Dobby and A McLay (2017). Crab and Lobster Fisheries in Scotland: Results of Stock Assessments 2013-2015 Scottish Marine and Freshwater Science Vol 8 No 14 https://data.marine.gov.scot/dataset/crab-and-lobster-fisheries-scotland-results-stock-assessments-2013-2015/resource/80511417 (Accessed June 2018)