Clam, Razor, clams
Capture method — Electrical fishing
Capture area — North East Atlantic (FAO 27)
Stock area — Scotland
Stock detail — All Areas
Updated: November 2019.
The stock status of razor clams in Scotland is unknown, but there are concerns that the stocks may be too low and fishing pressure may be too high.
In Scotland, there is currently a trial for electrical fishing of razor clams. For the lifetime of this trial (from 1st February 2018 onwards), all other forms of razor clam fishing are prohibited except for traditional hand gathering from the shore. The electrofishing trial was introduced to tackle widespread illegal electrical fishing for razor clams, which was difficult to catch ‘in the act’ and therefore not well policed prior to the trial. However, there are significant concerns about the approach to the trial: it is on a relatively large scale, without being informed by stock assessments, and so could lead to significant overfishing of a poorly-understood stock. It follows a period of wide-scale and significant stock exploitation through the illegal fishery, and so it is not known if the stock is able to withstand continued exploitation. In line with MCS’s wider approach to electrical fishing and pulse trawling, the fishing method in itself is not necessarily of concern, but it is currently very poorly understood. More research is needed, and trials should be on a smaller scale, to improve data on long-term impacts to the target stock and wider ecosystem. This fishery therefore receives a default red-rating and is a Fish to Avoid.
Hand gatherers may legally take up to 30 clams per day. As this level of hand gathering is unlikely to sustain a large commercial fishery, and given the historical high levels of illegal razor clam fishing, MCS urges buyers to carefully check the sources of their razor clams.
Razor clams are bivalve molluscs. There are 6 species found in British intertidal waters. 2 are of commercial importance: Ensis siliqua and E arcuatus. Spawning occurs in summer, and fertilised eggs develop into mobile larvae hours after fertilisation. The larval phase includes several stages and lasts for about 3-4 weeks, during which time they drift with the current. They then settle, attaching themselves to sand or shell by byssal threads. At around 0.5cm length juveniles burrow into sand. Relative to other commercially important bivalves, Ensis are long-lived, slow growing, and attain sexual maturity late in life. They may survive to 10-15 years and an average adult can reach a size of 12.5cm, although growth will cease by age 10. They can live in excess of 20 years. E. arcuatus reaches sexual maturity between 73 and 130 mm and E. siliqua mature between 118 - 140 mm in Scotland. They are filter feeders and normally lie vertically in the sediment with 2 small siphons, through which they feed, visible on the surface. Razor clams burrow into the sediment around the extreme low water mark and in the shallow subtidal and are capable of rapid burrowing if disturbed.
Two razor clam species are of commercial importance in the UK: Ensis siliqua and Ensis arcuatus (also known as Ensis magnus). Neither species has a stock assessment. The vulnerability of razor clams to fishing is low (10 out of 100), but the size of their populations and current and historical levels of fishing mortality are completely unknown, and there is concern for biomass and fishing mortality.
Razor clams around Scotland have, in the past, been subject to significant levels of illegal electrofishing. To tackle this, an electrofishing trial is now being conducted in the area. However, it is on a relatively large scale, and therefore could be continuing to allow high levels of exploitation on a potentially already depleted stock. Vessels in the trial are subject to a daily catch limit (450kg) and a maximum of 110 days at sea. With 24 vessels licensed by the end of January 2019, this amounts to 1,188 tonnes of clams being removed annually from Scottish waters. Razor clams have slow growth rates and their populations take a long time to recover. Intense harvesting has been shown to impact community structure, resulting in very slow rebuilding timeframes. Once fished, razor clam beds can be re-colonised, but only if there are sufficient clams in surrounding areas.
The electrofishing trial is collecting data that will in future be used for stock assessments, including length-weight relationships, size at maturity, landings, spawning times and locations of different populations.
In Scotland, there is currently a trial for electrical fishing of razor clams. For the lifetime of this trial (1st February 2018 onwards - there is no end date), all other forms of razor clam fishing are prohibited except for traditional hand gathering from the shore. The electrofishing trial was introduced to tackle widespread illegal electrical fishing for razor clams, which was difficult to catch ‘in the act’ and therefore not well policed prior to the trial. At its peak, the criminal fishery was believed to be making upwards of 65,000 pounds a day - more lucrative than the illegal drugs trade. However, there are concerns about the approach to the trial, as it is not considered to sufficiently reduce illegal fishing. In addition, the trial is on a large scale but is not informed by stock assessments of razor clams. There is a high risk that the trial could lead to overfishing of the stock. It therefore receives a default red-rating.
Vessels within the electrofishing trial are quite closely regulated: they must apply for a derogation from the EU prohibition on electrofishing, and must therefore have gear inspections by Marine Scotland before being authorised to fish. Health and safety inspections are also required, as this method involves passing an electric current over the seabed to induce clams to come out of their burrows, which are then hand-harvested by divers. The vessels must have remote electronic monitoring (REM) which must be on at all times, and indicates where the vessel is (every 10 seconds), what speed it is travelling and when gear is being deployed. Vessels in the trial are subject to a daily catch limit (450kg) and a maximum of 110 days at sea. With 24 vessels licensed by the end of January 2019, this amounts to up to 1,188 tonnes of clams being removed annually from Scottish waters. Based on REM data and 65 inspections on land and at sea, compliance by participants in the first year of the trial has been high. However, it is unclear if and how illegal electrofishing by vessels outside of the trial has been reduced.
There is a minimum landing size (MLS) of 100 mm applied to the Ensis species for all European stocks, but this is often lower than the size at which they mature. Undersize clams are left by the divers, which it is hoped will then return to their burrows, although the after-effects of the electric current can slow this process down, making them more vulnerable to predation. It is important that sufficient juvenile clams survive the harvesting process to maintain the population.
Prior to this trial, illegal electrofishing of razor clams was widely reported in Scottish seas, with an estimated 40 vessels fishing illegally in 2014. In 2014, the Scottish Government introduced Razor Fish Licences and deployed Marine Protection Vessels into inshore areas to deter illegal activity, but in 2017 enforcement was declared insufficient: the fishery was too profitable, there were important data gaps, and it was very difficult to convict fishers who illegally dumped fishing equipment when patrol vessels were nearby. Marine Scotland Compliance works with other authorities to target illegal fishers: there has been one manslaughter conviction, one 1 criminal investigation of tax fraud, 50 civil tax evasion investigations and 14 cases reported to prosecutor for fishing violations. The expansion of enforcement activity was proven to have some success: in 2016, when the Marine Protection Vessel Minaa was monitoring razor clam fisheries, landings of razor clams fell significantly, resuming when the vessel departed.
Criterion score: Critical Fail info
Electrical fishing was banned in the EU in 1998 to prevent irresponsible and dangerous fishing practices, but Scotland has received a derogation from the EU to allow a trial electrical fishery for razor clams, beginning 1st February 2018. Given the scale of the trial, there is a high risk that it could lead to overfishing of the stock. It therefore receives a default red-rating.
Electrofishing involves small boats trailing live electrical cables to pass an electric current over the seabed, stunning razor clams and causing them to come out of their burrows. The clams are then hand-harvested by divers. Electrofishing is more popular than other harvest methods because it is far more efficient than hand pulling and salting, and yields a higher quality, more valuable product than dredging. It presents limited impacts to the habitat and is very selective, but long-term impacts on the ecosystem are unknown.
In a 2014 study, electrofishing for razor clams was considered a relatively benign harvesting method (environmentally-speaking) compared to more conventional methods, such as dredging. The survey concluded that the electrofishing did not impact short-term survival (5 days) in razor clams, surf clams, starfish or hermit crab. However, the fishing method stunned sandeels (which recovered within 10 minutes) and may have increased the organisms’ susceptibility to predation (particularly from shore crabs and squat lobsters). It was also noted that juvenile razor clams, which are left by the divers to return to their burrows, may also be slow to recover from being stunned, delaying their return to the burrow and increasing their susceptibility to predation. Electrofishing-induced predation may be lower than that caused by mechanical dredge methods. However the study did not assess the long-term effects of electrofishing, the razor clam stock, nor consider appropriate harvesting levels of razor clams. The trial electro-fishery will allow these wider impacts to be studied but there is currently insufficient information to determine the true impact of electrofishing on the ecosystem.
Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.Abalone
Clam, Manila (Farmed)
Crab, brown or edible
Lobster, Norway, Langoustine, Dublin Bay prawn or scampi
Mussel, Chilean (Farmed)
Mussel, mussels (Farmed)
Oyster, Native, oysters
Oyster, Pacific, oysters
Oyster, Pacific, oysters (Caught at sea)
Oyster, Pacific, oysters (Farmed)
Prawn, King (whiteleg), prawns
Prawn, Northern prawns, Northern shrimp
Prawn, Tiger prawns (Farmed)
Scallop, King, scallops
Scallop, Queen, scallops
Squid, Japanese flying
ReferencesConstantino, R., Gaspar, M. B., Pereira, F., Carvalho, S., Cardia, J., Matias, D. and Monteiro, C. C. (2009), Environmental impact of razor clam harvesting using salt in Ria Formosa lagoon (Southern Portugal) and subsequent recovery of associated benthic communities. Aquatic Conserv: Mar. Freshw. Ecosyst., 19: 542-553. doi:10.1002/aqc.995.
Fishing News. 2017. Electrofishing Razor Clam Trials in Scotland. 10.04. 2017. Available at: http://fishingnews.co.uk/news/electrofishing-razor-clam-trials-in-scotland [Accessed on 27.02.2020].
Fox, C. 2017. To Develop the Methodology to Undertake Stock Assessments on Razor Fish Using Combinations of Video Monitoring and Electrofishing Gear. Fishing Industry Science Alliance (FISA) Project 09/15. Scottish Marine and Freshwater Science 8, 6. Marine Scotland Science, Aberdeen.
Fraser, S., Shelmerdine, R.L., and Mouat, B. (2018). Razor clam biology, ecology, stock assessment, and exploitation: a review of Ensis spp. in Wales. NAFC Marine Centre report for the Welsh Government. Contract number C243/2012/2013. pp 52. Available at https://www.nafc.uhi.ac.uk/t4-media/one-web/nafc/research/document/Fraser-et-al-2018-Razor-clams-in-Wales-report.pdf [Accessed on 27.02.2019].
Marine Scotland, 2019. Update: Electrofishing for razor clams trial (1 February 2018 - 31 January 2019). Available at https://www2.gov.scot/Resource/0054/00548864.pdf [Accessed on 27.02.2019].
Murray F, Copland P, Boulcott P, Rovertson M, Bailey N., 2014. Electrofishing for razor clams (Ensis siliqua and E. arquatus): Effects on survival and recovery of target and non-target species. Scottish Marine and Freshwater Science 5:14, Marine Scotland Science, Aberdeen, 50 pp. Available at https://www.gov.scot/publications/scottish-marine-freshwater-science-volume-5-number-14-electrofishing-razor/pages/5/ [Accessed on 27.02.2020].
Palomares, M.L.D. and Pauly, D. (Editors), 2019. SeaLifeBase. Ensis magnus: arched razor shell. Available at https://www.sealifebase.ca/summary/Ensis-magnus.html [Accessed on 07.11.2019].
Palomares, M.L.D. and Pauly, D. (Editors), 2019. SeaLifeBase. Ensis siliqua: sword razor shell. Available at https://www.sealifebase.ca/summary/Ensis-siliqua.html [Accessed on 07.11.2-19].
Scottish Environment Link, 2016. Consultation Response to electrofishing for razor clams in Scotland by the Scottish Environment LINK Marine Group: September 2016. Available at https://www.scotlink.org/publication/response-to-scottish-government-consultation-on-electrofishing-for-razor-clams-in-scotland/ [Accessed on 07.11.2019].
Scottish Government, 2019. Electrofishing for Razor Clams. Available at https://www2.gov.scot/Topics/marine/Sea-Fisheries/management/razors [Accessed on 07.11.2019].
Seafood Source. 2015. Illegal razor clam fishers caught in the act. 21.09.2015. Available at: https://www.seafoodsource.com/news/food-safety-health/illegal-razor-clam-fishers-caught-in-the-act [Accessed on 27.02.2020].
UK Government, 2017. The Razor Clams (Prohibition on Fishing and Landing) (Scotland) Order 2017. 2017. SSI 2017/419. Available at: http://www.legislation.gov.uk/ssi/2017/419/contents/made [Accessed on 27.02.109].