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 — Southern North Sea
Stock detail — 4c: Eastern IFCA District (0-6nm)
Picture of Crab, brown or edible

Sustainability rating four info

Sustainability overview

Updated: November 2020.

In the Southern North Sea, fishing mortality is high and above the maximum reference point for both males and females. Spawning stock biomass has been increasing in recent years but remains below the MSY target for both sexes. CEFAS reports that there has been an increase in fishing activity in the Southern North Sea and the increase in spawning stock must be treated with caution. Management measures in place include a ban on the landing of berried and soft crabs, and a minimum conservation reference size of 115mm carapace width, but there are no catch or effort limitations in place. Management measures are considered insufficient to recover the stock. Each year, Eastern IFCA produce stock assessments and are currently carrying out research into the impacts of fishing on the Cromer Shoal Chalk Bed MCZ. In general, pot fishing is considered sustainable as it is selective for larger individuals and has minimal impact on surrounding environment.

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: 1 info

Brown crab is widely distributed in coastal waters of the Mediterranean, Atlantic, English Channel and North Sea. CEFAS defines five Crab Fishery Units for England and publishes stock status reports for each area every 2 years.

In the latest stock assessment (2019), fishing mortality (F) of brown crab in the Southern North Sea is high for both males and females and, although stable, is above both the level required for maximum sustainable yield (MSY) and the maximum reference point limit.

Spawning stock biomass (SSB) has been increasing in recent years for both males and females and is now above the minimum reference point for both sexes, however, it remains below the MSY target for biomass. CEFAS suggest that there has been a recent expansion in fishing activity in the Southern North Sea, both in terms of pot numbers and distribution. This may be partly responsible for an increase in landings in the area which the biomass model interprets as an increase in spawning stock. Therefore, the spawning stock data must be treated with caution.

Management

Criterion score: 0.75 info

This assessment is for the brown crab fishery in the Eastern Inshore Fisheries and Conservation Authority (IFCA) district. Management measures in place for this fishery are currently not effective in managing the stock. EIFCA initiated a Crustacean stock assessment project in 2013 and every year, EIFCA produces stock assessments for the brown crab population in their district. In 2020, EIFCA have also taken an Adaptive Risk Management approach to manage potting in the Cromer Shoal Marine Conservation Zone which may lead to future improvements in management.

All vessels registered in the UK must have a domestic fishing vessel license to fish within the UK EEZ for sea fish that will be sold. No new licenses are being issued. All commercial vessels under 10m, with a shellfish license, are required to complete Monthly Shellfish Activity Return (MSAR) forms for the Marine Management Organisation (MMO). These must include the catch and retained weight each day along with the date, name of the vessel, vessel registration number, gear type, area and port of landing. All vessels over 10m do not need to complete MSAR as they will be completing an EU logbook of catches. For all vessels, effort is reported as days fished, and not as pots fished. In the Eastern IFCA district, there are no vessel length restrictions in place and you do not need a permit to fish commercially for crabs and lobsters. Eastern IFCA are planning to introduce a permit byelaw to allow them to better understand fishing activity.

Crab and lobster fisheries are not limited by EU Total Allowable Catch (TAC) regulations or national regulations, and therefore are not limited in the number of crabs they can take. Eastern IFCA has also not introduced a pot limit for crab and lobster fisheries.

In this area, there is a Minimum Conservation Reference Size (MCRS) of 115mm carapace width. Population studies have revealed a smaller average size of crab and lobster in North Norfolk when compared to adjacent areas. It is believed to be because of migration patterns and recruitment regimes in crabs, however no recent research is available. MCS would like to see a review of the MCRS in this area. According to CEFAS, in the Southern North Sea, around 96-99% of males and 60-86% of females should be sexually mature at this size. National legislation in England and Wales also prohibits the landing of berried and soft crabs. Byelaws in EIFCA also prohibit the landing of ‘whitefooted’ (not fully hardened) crab between 1st November and 30th June. In addition, when using pots or creels, a maximum of 1% by weight of the total catch of brown crabs landed may consist of detached claws. For all other gear types, a maximum of 75kg of detached claws may be landed. In many areas, market preference can also have influence on the crabs which are landed, as those having an unclean appearance, due to disease or discolouration, or those missing both claws can be seen as unmarketable.


The UK Fisheries Act came into force in January 2021 and requires the development of Fisheries Management Plans (FMPs). There are no details yet on how and when these will be developed. FMPs have the potential to be very important tools for managing UK fisheries, although data limitations may delay them for some stocks. MCS is keen to see FMPs for all commercially exploited stocks, especially where stocks are depleted, that include:
Targets for fishing pressure and biomass, and additional management when those targets are not being met
Timeframes for stock recovery
Technologies such as Remote Electronic Monitoring (REM) to support data collection and improve transparency and accountability
Consideration of wider environmental impacts of the fishery

Capture Information

Criterion score: 0 info

In the UK, brown crab and European lobster are fished together in a mixed fishery with seasonal and regional variation of target species taking place. The key fishing season for brown crab in the UK takes place from May to December. Crabs are caught in pots, also known as creels, and can be fished individually or as part of a fleet of up to 100 pots, depending on the size of the boat and crew. Pots are portable traps made 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 becomes trapped.

Pot fishing is considered sustainable as it is selective for larger individuals and has minimal impact on the surrounding environment. In brown crab fisheries, there is no legislation or regulation to standardise the type of pot used. They tend to be highly selective as undersized animals can be returned to the sea alive and survival rates for non-target organisms are thought to be high. More than half of the bycatch caught are predicted to survive, although there is little available research to prove this. Measures to further reduce bycatch include the use of escape panels to allow undersize animals and bycatch to escape pots.

In the Eastern IFCA district, pot fishing takes place in the Cromer Shoal Marine Conservation Zone (MCZ) and in 2020, research was carried out into the impact of potting on the chalk bed. Results from this research show that permanent damage is occurring to the chalk bed as a result of human activity and crab and lobster potting. Although each individual occurrence of damage was small-scale, the additive effect of these small-scale impacts over time could be altering the chalk bed on a larger scale in a more rapid and focused way than natural change would be. The survey found that some of the chalk damage can be attributed to active crab and lobster pots, however, some damage is also occurring from submerged pots that are not actively used (i.e. lost, stored, or territory marking). Much of the damage caused was by rope, rather than the pots themselves.

References

Cefas. 2020. Edible crab (Cancer pagurus). Cefas Stock Status Report 2019 18 pp. Available at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/928793/Crab_assessments_2019..pdf [Accessed on 01.12.2020].

CBI. 2020. Entering the European market for crab. Available at https://www.cbi.eu/market-information/fish-seafood/crab/market-entry [Accessed on 01.12.2020].

Eastern Inshore Fisheries and Conservation Authority. 2018. Crab and Lobster Stock Assessment. Available at https://www.eastern-ifca.gov.uk/wp-content/uploads/2019/09/2019_04_25_Crustacean_Stock_Assessment_report_2018.pdf [Accessed on 01.12.2020].

Eastern Inshore Fisheries and Conservation Authority. Byelaws. Available at https://www.eastern-ifca.gov.uk/byelaws/ [Accessed on 01.12.2020].

Gall, S.C., Rodwell, L.D., Clark, S., Robbins, T., Attrill, M.J., Holmes, L.A. and Sheehan, E.V. 2020. The impact of potting for crustaceans on temperate rocky reef habitats: Implications for management. Marine Environmental Research, 162, p.105134. Available at https://www.sciencedirect.com/science/article/abs/pii/S0141113619308657 [Accessed on 08.12.2020].

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. Available at http://www.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 on 01.12.2020].

ICES. 2018. Interim Report of the Working Group on the Biology and Life History of Crabs (WGCRAB), 6–8 November 2018, Jersey. ICES CM 2018/EPDSG:09. 13 pp. Available at http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/EPDSG/2018/WGCRAB%20-%20Report%20of%20the%20Working%20Group%20on%20the%20Biology%20and%20Life%20History%20of%20Crabs.pdf [Accessed on 01.12.2020].

ICES. 2018. Interim Report of the Working Group on the Biology and Life History of Crabs (WGCRAB), 8–10 November 2017, Brest, France. ICES CM 2017/SSGEPD:09. 30 pp. Available at https://www.ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/SSGEPD/2017/01%20WGCRAB%20-%20Report%20of%20the%20Working%20Group%20on%20the%20Biology%20and%20Life%20History%20of%20Crabs.pdf [Accessed on 01.12.2020].

Marine Management Organisation. 2018. Statutory guidance: Minimum Conservation Reference Sizes (MCRS) in UK waters. Available at https://www.gov.uk/government/publications/minimum-conservation-reference-sizes-mcrs/minimum-conservation-reference-sizes-mcrs-in-uk-waters#crustaceans [Accessed on 01.12.2020].

Mesquita, C., Dobby, H., Pierce, G.J., Jones, C.S., Fernandes, P.G. 2020. Abundance and spatial distribution of brown crab (Cancer pagurus) from fishery-independent dredge and trawl surveys in the North Sea. ICES Journal of Marine Science, fsaa105. Available at https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsaa105/5880823 [Accessed on 01.12.2020].

Moffat, C., Richardson, H. and Roberts, G. 2020. Natural England marine chalk characterisation project. Natural England Report NERR080. Available at http://publications.naturalengland.org.uk/publication/5385776319954944#:~:text=Natural%20England%20Marine%20Chalk%20Characterisation%20Project%20(NERR080),England%20on%202%20March%202020%20.&text=Marine%20chalk%20is%20protected%20within,marine%20chalk%20as%20a%20feature [Accessed on 01.12.2020].

Nautilus Consultants. 2009. Final Report: Future Management of Brown Crab in UK and Ireland. Available at https://www.sff.co.uk/wp-content/uploads/2015/09/Nautilus-Brown-Crab-Management-FinRep.pdf [Accessed on 01.12.2020].

Palomares, M.L.D. and Pauly, D. Editors. 2020. SeaLife Base. Cancer pagurus, edible crab. Available at https://www.sealifebase.ca/summary/Cancer-pagurus.html [Accessed on 01.12.2020].

Seafish. Pots and traps – Brown Crab. Available at https://www.seafish.org/responsible-sourcing/fishing-gear-database/gear/pots-and-traps-brown-crab/ [Accessed on 07.12.2020].

Stevens, B. G. 2020. The ups and downs of traps: environmental impacts, entanglement, mitigation, and the future of trap fishing for crustaceans and fish, ICES Journal of Marine Science. Available at https://doi.org/10.1093/icesjms/fsaa135 [Accessed on 08.12.2020].

Tibbitt, F., Love, J., Wright, J., Chamberlain, J. 2020. Human Impacts on Cromer Shoal Chalk Beds MCZ: Chalk complexity and population dynamics of commercial crustaceans. Natural England Research Report number 04412. Available at https://www.eastern-ifca.gov.uk/wp-content/uploads/2020/10/D2020-00111615-NERR-Human-Impacts-on-the-Cromer-Shoal-Chalk-Beds-MCZ.pdf [Accessed on 01.12.2020[.

UK Government. 2020. UK sea fisheries annual statistics report 2019. Available at https://www.gov.uk/government/statistics/uk-sea-fisheries-annual-statistics-report-2019 [Accessed on 07.12.2020].