Spider crab

This stock is data limited and the status of spider crabs around the UK is currently unknown. There is concern for biomass but no concern for fishing pressure.Route 2 (data limited) scoring has been applied to this rating owing to the lack of data about the species biomass and catch limits. There is no available data on spider crab resilience to fishing pressure, but they are considered to have low (0.12) vulnerability to fishing.No assessment of biomass is undertaken across this spider crab fishing area and stock status reports are not regularly produced for the species. Therefore, there is concern for the biomass.There are no reference points to determine fishing pressure. In 2023, MMO landings from UK vessels operating in the UK EEZs were estimated at just over 424 tonnes. This is an increase from 2022, when landings were around 410 tonnes, but remains below the four-year average (2019-2022) of over 481 tonnes. Although there is no clear trend and the data is limited, there is currently no concern for fishing pressure.Given the lack of biomass data and the likely influence of market value on landings, it is difficult to determine the overall status of spider crabs. To better assess and understand the stock, fisheries-independent data and more accurate evaluations of bycatch levels are needed.

Few appropriate management measures are in place, and their effectiveness cannot be fully assessed due to limited data. UK minimum landing sizes are enforced, but these are below estimates for maturity.Due to a lack of data about the species biomass, it is not possible to assess whether current fishing levels are sustainable. Considerable improvements are needed including regular stock assessments for spider crab to guide management.There is a Minimum Conservation Reference Size (MCRS) of 130 mm carapace length for males, and 120 mm for females, with spider crabs required to be landed whole. This is below maturity estimates of 136.5 mm for males, and 130.3 mm for females. Also, it is likely that this standard size does not optimise reproduction and landings as some stocks mature smaller and some larger than this size.In UK pot and trap fisheries, general management measures provide some protection to spider crabs. For example, under the Western Waters Regime, effort in the brown crab fishery – where spider crabs are often bycaught – is restricted. Vessels of 15 m and above are limited to 220 days at sea in ICES area 7 between 1 January and 31 December.Additional protection may exist in inshore areas, where local byelaws and regulations apply. There may also be overlap with Marine Protected Areas (MPAs), which impose further restrictions on fishing effort, gear, and landings to support habitats and commercial species. Gear modifications, such as escape gaps on pots, can allow undersized crabs to escape, as well as non-target finfish and other invertebrates.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.The Marine Conservation Society views Remote Electronic Monitoring (REM) with cameras is one of the most cost-effective tools for providing reliable fisheries data and aiding informed management decisions. Fully monitored fisheries enhance collaboration, data accuracy, stock recovery, and reduce impacts on marine wildlife and habitats. However, the full potential of REM may only be achieved when it tracks fishing location and documents catch and bycatch, particularly where vulnerable species and habitats are at risk. As of January 2024, the EU is introducing a Remote Electronic Monitoring (REM) mandate for EU vessels, including CCTV cameras on vessels 18m or more that pose a potential risk of non-compliance, within the next 4 years. Across the UK, different approaches to REM are being taken and legislation is expected to be in place across all 4 countries within the next few years.The Fisheries Act (2020) requires the development of Fisheries Management Plans (FMPs) (replacing EU Multi-Annual Plans) in the UK. 43 FMPs have been proposed and are at various stages of development and implementation, these should all be published by the end of 2028. FMPs have the potential to be very important tools for managing UK fisheries, although data limitations may delay them for some stocks. It is also essential the UK governments define and adopt a standardised approach or model across the four nations to a universally defined FMP design, to ensure the consistence, quality and coherence of all the proposal FMPs.The Marine Conservation Society is keen to see publicly available Fishery Management Plans for all commercially exploited stocks, especially where stocks are depleted, that include:An overview of the fishery including current stock status, spatial coverage, current fishing methods and impactsTargets for fishing pressure and biomass, and additional management when those targets are not being met, based on the best scientific evidenceTimeframes for stock recoveryImproved data collection, transparency, and accountability, supported by technologies such as Remote Electronic Monitoring (REM)Consideration of wider environmental impacts of the fishery, including habitat impacts and minimising bycatchStakeholder engagementA Crab and Lobster FMP has been proposed, coordinated by Defra, which incorporates this species. At the time of writing, it is too soon to know whether proposed management measures will be effective in managing the stock. For more information about this FMP and expected progress and timelines, see https://www.gov.uk/government/publications/joint-fisheries-statement-jfs/list-of-fisheries-management-plans

Spider crabs are usually caught as bycatch in the potting fishery for brown crab and lobster. Crab pots have low seabed impacts when deployed and retrieved correctly.Spider crabs are a common bycatch species in the mixed fishery for brown crab and European lobster. 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.In 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. Studies of Irish Sea potting fisheries shown that common bycatch species are small-spotted catsharks and squat lobsters. While more than half of the bycatch is predicted to survive, there is little research available to support this. Measures to further reduce bycatch include the use of escape panels to allow undersize animals and bycatch to escape pots.Habitat impacts from potting are low but can occur during deployment, soak time or hauling of the pot, impacting the benthic habitat and associated species through contact with the pot or end weight, or by scouring from ropes. Research that has taken place suggests that while some damage does occur, it is unlikely to be significant unless potting intensity is high (defined as approximately 30 pots per 500 square metres). The most damage occurs when traps are set in sensitive habitats such as rocky reefs, seagrass beds, and maerl beds. These ecosystems play a crucial role in supporting marine biodiversity by providing nursery grounds, shelter from predators, and settlement areas for invertebrate spat.Lost pots can pose an additional risk to marine life through ‘ghost fishing’, where abandoned gear continues to trap and entangle species. As fishing gear is a financial investment, there is incentive to maintain and recover lost pots. The occurrence of ghost fishing can also be reduced by the use of appropriate gear designs and release devices.To improve monitoring and reporting of fishing activity, The Marine Conservation Society would like to see remote electronic monitoring (REM) with cameras implemented, used and enforced.

Corgos, A. and Freire, J., 2006. Morphometric and gonad maturity in the spider crab Maja brachydactyla: a comparison of methods for estimating size at maturity in species with determinate growth. ICES Journal of Marine Science, 63(5), pp.851-859. 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, Volume 162, 105134, https://doi.org/10.1016/j.marenvres.2020.105134.GOV.UK, 2025. Guidance: Record your catch. Available at: Record your catch - GOV.UK [Accessed on 20.11.2025]GOV.UK. 2025. Manage your fishing effort: Western Waters crabs and scallops. Available at https://www.gov.uk/guidance/manage-your-fishing-effort-western-waters-crabs [Accessed on 24.11.2025].MMO, 2025. Minimum Conservation Reference Sizes (MCRS) in UK waters. Available at: Minimum Conservation Reference Sizes (MCRS) in UK waters - GOV.UK [Accessed 19.11.2025]MMO, 2023. UK sea fisheries annual statistics report 2023. Available at: UK sea fisheries annual statistics report 2023 - GOV.UK [Accessed on 24.11.2025]Öndes, F., Kaiser, M., & Murray, L. 2018. Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea. Journal of the Marine Biological Association of the United Kingdom, 98(8), 2099-2111. doi:10.1017/S0025315417001643Palomares, M.L.D. and D. Pauly. Editors. 2025. SeaLifeBase. Maja squinado, spinous spider crab, World Wide Web electronic publication. www.sealifebase.org, version (04/2025) [Accessed on 03.12.2025].Seafish. Pots and Traps – General. Available at: seafish.org/responsible-sourcing/fishing-gear-database/gear/pots-and-traps-general/#target-species [Accessed on 18.11.2025]