Capture method — Pulse trawl
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea, Skagerrak
Stock detail — 4, 3a.20
Updated: July 2019
Default red rating: The plaice stock in this area is classified as healthy and fishing mortality is at a sustainable level, however the large scale use of electro pulse trawling in the southern North Sea without a better understanding of the ecological impacts of this experimental fishing method is concerning. At the time of assessment over 80 large pulse trawlers were operating in the region under experimental derogations to an EU ban. However, as these derogations will not be renewed, 42 licences are expected to be withdrawn in 2019, and a further 42 by 2021. A recent review from the International Council for Exploration of the Sea (ICES) suggests that pulse trawling likely has fewer environmental impacts than traditional beam trawling due to less physical disturbance of the gear. However, there remain several outstanding issues of concern in relation to non-physical impacts, such as delayed mortality and long-term population effects as well as sub-lethal and reproductive effects of electric trawls. A four-year scientific research programme is expected to be completed in 2019 and whilst these uncertainties remain, MCS does not believe the current scale of pulse trawling is justified and does not reflect precautionary management. A critical fail to this capture method currently applies resulting in a default red rating.
Please see the ‘Capture info’ TAB for more info about pulse trawling.
Plaice is a bottom-dwelling flatfish. It spawns in the early months of the year (January to March) and sometimes makes long spawning migrations. North Sea plaice reach between 35 and 45 cm in their 6th year. It is a long-lived species, becoming sexually mature at 3-7 years (females) 2-6 (males) and living 30 years or more. Maximum reported age 50 years.
North Sea, Skagerrak
The stock is in a very good state, and fishing pressure is at sustainable levels.
From 1957 to 2007, the spawning-stock biomass (SSB) was below sustainable levels (MSY Btrigger, 564,599 tonnes). However, it has markedly increased since then, reaching 967,508t in 2018 - well above sustainable limits. This follows a substantial reduction in fishing mortality (F) since 1999. Fishing mortality reached sustainable levels (i.e. below FMSY, 0.21) for the first time in 2009, and has stayed just below this limit ever since, being at 0.187 in 2018. Recruitment has been fluctuating around the long-term average since the mid-1990s. There is some uncertainty in assessing the abundance of older fish (10+), and therefore some uncertainty in the estimates of SSB.
ICES advises that when the MSY approach is applied, catches in 2020 should be no more than 131 439 tonnes. This is a 7.6% decrease from the year before owing to recruitment fluctuations. Recent Total Allowable Catches (TACs) have been in line with scientific advice, and catches have been in line with TACs.
Survey data implies that older fish are likely migrating to the north-western part of the North Sea, where the targeted fishing effort is low, and this has partly resulted in reduced fishing mortality at older ages, and an upward trend of SSB in recent years (in 2018, plaice aged five and older contributed to 85% of the SSB). Plaice in the Skagerrak (area 3a.20) is considered to have an Eastern and a Western component, with the Western component missing with plaice migrating in from the North Sea. Most of the catches are on summer feeding aggregations in the Western Skagerrak. North Sea plaice also migrates into the eastern English Channel (area 7d) during January-March, so 50% of the mature animals from that area during Q1 are included in the North Sea plaice assessment.
It is possible that the high population of plaice could have other ecosystem impacts, for example the ability of benthic prey populations to support such a high plaice population. This, and warming North Sea waters, could be the causes of slower growth rates seen in the stock recently.
The 2007 recovery plan successfully brought fishing pressure down to sustainable levels, and the stock has since dramatically increased in size. However, discards are high, at 50%, and landings of small fish are below what monitoring programmes suggest they should be, indicating better monitoring and enforcement of the Landings Obligation might be needed.
This stock is covered by the EU’s North Sea Multi Annual management Plan (MAP), and although the MAP has not been adopted by Norway, joint TACs are agreed through the EU-Norway Agreement. Rather than holding strictly to MSY-based reference points, the MAP includes upper and lower ranges for fishing pressure (F). This is to allow for the multi-species nature of the fishery - a number of demersal species are caught together in the North Sea, and if catch limits are reached for one species, this will limit the ability to catch others even when quotas are not filled. Therefore, the MAP allows some species to be caught at levels above MSY ‘when needed’, as long as the stock is in a healthy state. Total Allowable Catches (TACs) currently follow ICES’ MSY-based approach and are at sustainable levels.
Since 2016, large mesh trawlers have been under the landing obligation in the North Sea. In 2019 the fleets that contribute most to the total discards will also fall under landing obligation in the North Sea, with de minimis and high survival exemptions in certain fisheries. In 2018, 52% of the total catch in the North Sea and 19% in the Skagerrak was discarded. There is a Minimum Conservation Reference Size (MCRS) for plaice in the North Sea of 27cm, although average size at maturity is between 35 and 45 cm for males and females respectively. Reported Below Minimum Size (BMS) landings for fleets that are under the landing obligation in the North Sea are currently much lower than would be suggested by information from catch monitoring programmes.
Surveillance activities on fisheries for demersal stocks in North Sea, Skagerrak, and West of Scotland include the use of vessel monitoring systems (VMS) on vessels over 12m; direct observation by patrol vessels and aerial patrols; inspections of vessels, gear, catches at sea and on shore and requirements to record data in electronic logbooks (although vessels under 10m do not have to keep logbooks).
Criterion score: Default red rating info
Pulse trawling in the North Sea is an experimental type of beam trawling which uses electrical pulses to shock and immobilise fish, making it easy for them to be captured in the trailing trawl net as opposed to traditional heavy tickler chains used to startle the fish. The use of electricity in the marine environment is generally forbidden under European Union law, but a series of derogations have been granted, primarily to the Dutch fleet, allowing the experimental use of pulse trawling in the southern North Sea. In 2016 there were approximately 90 active pulse trawl vessels mainly targeting flatfish.
The method uses up to 50% less fuel than traditional beam trawling and there is evidence that it can reduce unwanted catches and physical disturbance to the sea floor, yet there is a lack of knowledge on whether the electric pulses can negatively impact on other species found near the seafloor and the ecological processes of the seafloor community, and concern has been raised over the widespread use of the gear before more comprehensive research has been undertaken. ICES have indicated that the current scale of use is above what would normally be associated with scientific research and that any expansion outside of what is currently permitted without a comprehensive environmental impact assessment would not be considered precautionary.
Research indicates that electric pulse trawling can cause spinal fractures and haemorrhaging in cod and whiting (mainly in larger fish) and can increase the vulnerability of shrimp to viral infection. Initial research on impacts to dab, dogfish and sole suggest there is little impact on these species. Laboratory experiments have investigated behavioural responses from a range of other seafloor species likely encountered by pulse trawling including a collection of molluscs, echinoderms, crustaceans and polychaetes. Whilst several species have not shown any significant behavioural difference to electric pulses, the green crab has shown a change in feeding behaviour and reduced survivability has been observed in a few species. ICES (2016) stated that there is no reason to assume that the effects of electrical stimulation on invertebrates has a larger impact than that from conventional beam trawling yet note that research questions remain for target and non-target species regarding delayed mortality and long-term population effects as well as sub-lethal and reproductive effects of electric trawls. More recently, ICES have suggested that pulse trawling likely has fewer environmental impacts than traditional beam trawling due to less physical disturbance of the gear, however, there remain several outstanding issues of concern in relation to non-physical impacts, such as delayed mortality and long-term population effects as well as sub-lethal and reproductive effects of electric trawls. A four-year scientific research programme is expected to be completed in 2019 and whilst these uncertainties remain, MCS does not believe the current scale of pulse trawling is justified and does not reflect precautionary management. A critical fail to this capture method currently applies resulting in a default red rating.
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.Dab
Halibut, Atlantic (Farmed)
Sole, Dover sole, Common sole
Turbot (Caught at sea)
ReferencesEU, 2019. Technical measures regulation. EU 2019/1241. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32019R1241&from=EN [Last accessed 13.09.2019].
EU, 2019. Bilateral Agreements: Norway Northern Agreement. Available at https://ec.europa.eu/fisheries/cfp/international/agreements/norway [Accessed on 02.07.2019].
EU, 2018. Regulation 2018/973 establishing a multiannual plan for demersal stocks in the North Sea and the fisheries exploiting those stocks. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0973&from=EN [Accessed on 02.07.2019].
ICES. 2019. Plaice (Pleuronectes platessa) in Subarea 4 (North Sea) and Subdivision 20 (Skagerrak). In Report of the ICES Advisory Committee, 2019. ICES Advice 2019, ple.27.420, doi: 10.17895/ices.advice.4870. Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/ple.27.420.pdf [Accessed on 03.07.2019].
ICES, 2018. Report of the Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK), 24 April - 3 May 2018, Oostende, Belgium. ICES CM 2018/ACOM: 22pp. Available at http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/acom/2018/WGNSSK/01-WGNSSK%20Report%202018.pdf [Accessed on 02.07.2019].
ICES, 2018. The Netherlands request on the comparison of the ecological and environmental effects of pulse trawls and traditional beam trawls when exploiting the North Sea sole TAC. Available at http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2018/Special_requests/nl.2018.08.pdf [Accessed Sept 2018].
ICES, 2016. Request from France for updated advice on the ecosystem effects of pulse trawl. Available at http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2016/Special_Requests/France_Effects_of_pulse_trawl.pdf [Accessed Aug 2016].
NSAC, 2015. Advice on the: Use of pulse trawls in the North Sea. Available at http://www.nsrac.org/wp-content/uploads/2014/12/7-1415-20150923-Use-of-Pulse-Trawls-in-the-North-Sea.pdf [Accessed August 2016]
Soetaert, M., Decostere, A., Polet, H., Verschueren, B., Chiers, K., 2015. Electrotrawling: a promising alternative fishing technique warranting further exploration. Fish , 16: 104-124. doi:10.1111/faf.12047. Available at http://onlinelibrary.wiley.com/doi/10.1111/faf.12047/full [Accessed Sept 2016].
Van Marlen, B., de Haan, D., Van Gool, A. and Burggraaf, D., 2009. The effect of pulse stimulation on marine biota - Research in relation to ICES advice - Progress report on the effects on benthic invertebrates, IMARES C103/09, 53 pp.