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

Orkney


Picture of Crab, brown or edible

Sustainability rating three info

Sustainability overview

Pots or creels have a low habitat impact. They are also a highly selective method of fishing as undersized animals can be returned to the sea alive. Brown crab from fisheries managed by Orkney Sustainable Fisheries (OSF) are a good choice. Their Code of Practice prohibits landing of pre or post moult and berried or egg-bearing female crabs. The predicted date by which the assessment is expected to be completed and certification awarded if the assessment result is positive is May 2018.

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. Although some assessment has been carried out on brown crab in the UK and Scottish waters, the status of stocks (e.g. populations, seasonal distributions, etc.) in some areas is unclear.

Reference points do not exist for the Orkney brown crab creel fishery. Precautionary reference point values for crustacean fisheries are often derived by analogy with finfish, such that F at 35% of unexploited spawning potential is considered a reasonable proxy for an FMSY target. This is assumed to be precautionary, given that crustacean stocks are often considered to be relatively robust to depletion of spawning potential. For the Orkney brown crab fishery, this lack of area-specific information is currently being addressed as part of a Fishery Improvement Project (FIP) working towards meeting the Marine Stewardship Council’s sustainable fisheries standard.

Stock assessments carried out by Marine Scotland for the period 2013-2015 showed that most brown crab assessment areas in Scotland were fished close to or above the FMSY proxy. Fishing mortality was estimated to be above FMSY for both males and females in Orkney. Preliminary assessment of the stock for the period 2013 to 2015 suggests fishing mortality is too high and above FMSY for both males and females.

Management

Criterion score: 0.25 info

In Scotland, vessels fishing for brown, velvet, spider, or green crab, lobster or crawfish must have a licence with a shellfish entitlement. Crab and lobster fisheries are not subject to EU TAC regulations or national quotas although there are measures in place to restrict the fishing effort through kW days at sea for boats over 15m. The quantities that are permitted to be landed are not restricted.
Owners of vessels of length 10 m and under with a shellfish entitlement are required to complete the FISH1 form for all landings of lobsters and crabs and submit it on a weekly basis to the Fishery Office at which the vessel is administered.
For vessels of length over 10 m, data on fishing activity by trip must be recorded in a EU logbook and submitted to the Fishery Office within 48 hours of landing.
Licensed fishing vessels which do not hold a shellfish entitlement can land a maximum of 5 lobsters and 25 crabs per day. New regulations, effective from April 2017, restrict the numbers of certain shellfish species that can be taken by unlicensed fishing boats. The restrictions are set daily per vessel as, 1 lobster, 5 crabs (any species), 10 Nephrops and 6 scallops.

There is currently a restrictive licensing system, whereby no new licenses and entitlements are being granted. There are, however, non-active (latent) licence entitlements which mean that there is the potential for the number of vessels fishing for crab and lobster to increase. It became clear that in the UK and Ireland there is significant latent capacity (part of the fleet that is currently inactive but continues to hold fishing entitlements) that could potentially target brown crab, but the likelihood of currently unused shellfish entitlements becoming active could not be estimated at the time (Mesquita et al., 2015).

EU technical conservation measures include geographically varying minimum (150 mm) landing sizes (MLS) and restrictions on the amount of crab claws that can be landed. Orkney Sustainable Fisheries (OSF) Ltd was established some 8 years ago to take over the running of the local lobster hatchery and carry out shellfish research. The fishery currently employs 4 shellfish researchers and has a number of management projects underway alongside a major 4-year shellfish research project looking at inshore fishing activity in a marine spatial planning context, as well as running the UK’s first Fishery Improvement Plan (FIP) for local crustacean species. The FIP for the Orkney brown crab fishery is the only recognised FIP for brown crab in the world. The fishery is in the 4-year FIP to enable it to obtain Marine Stewardship Council (MSC) certification. All processing is done in co-operatively owned factories on the islands and only brown crab that is caught by the boats owned and registered in Orkney, fishing out of and landing into Orkney ports are processed. Recently the fishery announced that they are applying for EU Product Designation of Origin (PDO). Benefits to the consumer are fish of known origin from a monitored and sustainable fishery. To demonstrate OSF’s commitment to sustainable fishing a Fishermen’s Code of Practice is in place, specifying best practice for fishing, handling and storage of shellfish. The legal limit of 140 mm carapace width ensures that females can spawn at least once before entering the fishery. OSF applies further precaution by applying a larger MLS of 153 mm. The Code of Practice also requires that only hard shelled, heavy and crabs in good condition are landed. Under the Code landing of pre or post moult crabs; berried or egg-bearing female crabs; crabs exhibiting “black spot”; cripple or one-clawed crabs; or other visibly diseased crab is prohibited. The predicted date by which the assessment is expected to be completed and certification awarded if the assessment result is positive is May 2018.

Capture Information

Criterion score: 0 info

A crab pot is a portable trap made up of wood or steel wire and plastic. The crab is baited into the initial part (the chamber) and moves into the secondary part (the parlour) where it is trapped. Pots or creels have a low habitat impact. They are also a highly selective method of fishing as undersized animals can be returned to the sea alive. The fishery have notified that undersized orout of condition target species are returned alive. The fishery also has very little bycatch, starfish and hermit crabs, are returned to the sea alive. Measures to further reduce bycatch and environmental impact is the trial of escape panels to allow undersize animals and bycatch to escape creels. The fishery harvests 25-30% of the total Scottish brown crab catch.

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)
http://assets.wwf.org.uk/downloads/orkney_brown_crab_fip_action_plan_2013.pdf?_ga=1.217609366.1415573881.1445252840
http://www.gov.scot/Topics/marine/marine-environment/species/fish/shellfish/BrownCrab
http://www.orkneycrab.co.uk/index.php
http://www.arkive.org/edible-crab/cancer-pagurus/#text=All
http://producerexchange.marksandspencer.com/news/ms-support-ground-breaking-shellfish-research-project-orkney
Http://www.wwf.org.uk/what_we_do/changing_the_way_we_live/food/seafood__responsibility_and_stewardship/orkney_brown_crab_fip/
Http://assets.wwf.org.uk/downloads/orkney_fip_annual_review_reprt_2014.pdf?_ga=1.223752667.1738140489.1446129726
Http://www.orkneysustainablefisheries.co.uk/wp-content/uploads/2014/12/Orkney_FIP-2014.pdf
https://fisheries.msc.org/en/fisheries/osf-orkney-brown-crab-creel-fishery/@@assessments (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)