Sole, Dover sole, Common sole

Solea solea

Method of production — Caught at sea
Capture method — Pulse trawl
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea
Stock detail — 4
Picture of Sole, Dover sole, Common sole

Sustainability rating five info

Sustainability overview

Updated: July 2019

Default red rating: The Dover sole biomass in the North Sea is in a good state, although fishing pressure remains a bit too high and is above the maximum sustainable yield. Fishing pressure has reduced due to past management measures. However, discarding could still be taking place, despite the Landing Obligation being fully in force since 2016. 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. Over 80 large pulse trawlers are 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 However, as these derogations will not be renewed, 42 licences are expected to be withdrawn in 2019, and a further 42 by 2021.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 the 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 scale of pulse trawling reflects precautionary management and applies a critical fail to this capture method as a result.


Sole is a right-eyed flatfish (eyes on the right hand side of the body) and belongs to the family of flatfishes known as Soleidae. It spawns in spring and early summer in shallow coastal water, from April to June in the southern North Sea, from May-June off the coast of Ireland and southern England, and as early as February in the Mediterranean. Common sole become sexually mature at 3-5 years, when 25-35cm long, the males being somewhat smaller than the females. It can attain lengths of 60-70cm and weigh 3kg.The maximum reported age is 26 years. Sole is a nocturnal predator and therefore more susceptible to capture by fisheries at night than in daylight.

Stock information

Stock Area

North Sea

Stock information

The stock is in a good state, and fishing pressure has declined to just above sustainable levels.

The spawning-stock biomass (SSB) has increased since 2007 and has been estimated above MSY Btrigger (37,000t) since 2012. In 2018 it was at 51,459t. Fishing mortality (F) has declined since 1999 and the 2018 level (0.22) is close to FMSY (0.202) and the lowest since 1958. Recruitment (R) has fluctuated without trend since the early 1990s.

ICES advises that when the EU multiannual plan (MAP) for the North Sea is applied, catches in 2020 that correspond to the F ranges in the MAP should be between 7,170 tonnes and 20,820 tonnes. According to the MAP, catches higher than those corresponding to FMSY (12,317 tonnes) can only be taken under conditions specified in the MAP (see management tab for MAP details), whilst the entire range is considered precautionary when applying the ICES advice rule. This is a 3.80% reduction compared to last year, owing to the downwards revision of SSB in the update assessment, as well as low recent recruitment. Between 1997 and 2008 TACs were set above scientific advice, sometimes significantly so, and catches often exceeded them. TACs and catches have come closer to the advice since then. In 2019 - the first year of managing this stock according to the North Sea MAP - ranges were set at 7451t - 21,644t and the TAC was agreed at 12,555t, which was below FMSY.

Survey data from 2000-2017 shows that the stock is expanding north of 56 degrees N, up to the west coast of Denmark, particularly for sole larger than 24 cm.


The 2007 recovery plan successfully reduced fishing pressure, which has now almost reached sustainable levels, and the stock is now in a good state. Observer reports suggest that unreported discarding is still occurring, despite the Landing Obligation.

This stock is covered by the EU’s North Sea Multi Annual management Plan (MAP). 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 under specific conditions: SSB must be greater than MSY Btrigger, and: a) if it is necessary for the achievement of objectives of mixed fisheries; or b) if is necessary to avoid serious harm to a stock caused by intra- or inter-species stock dynamics; or c) in order to limit variations in fishing opportunities between consecutive years to not more than 20 %. ICES considers that the FMSY range for this stock used in the MAP is precautionary.

Between 2014 and 2018 the use of pulse trawls in the main fishery operating in the North Sea has increased and fewer vessels are operating with traditional beam trawls. The pulse gear allows fishing of softer grounds and as a result the spatial distribution of the main fisheries has changed to the southern part of the Division 4.c. As a consequence, a larger proportion of the sole catch is now taken in this area. Following the EU decision in February 2019 to revise the technical measures regulations, the pulse gear will be prohibited from 30th of June 2021 and it is now being phased out. It is expected that the fleets will revert to the traditional gears and fishing grounds.

Sole in Subarea 4 has been fully under the landing obligation since 2016, with de minimis and high survivability exemptions in place for certain fleets. It would be expected that this would result in an increase of below minimum size (BMS) fish that would formerly have been discarded now being reported in landings in logbooks. However, BMS landings are currently much lower than the would be expected, which in 2018 would be 8.6% of the total catch based on 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). Observer coverage in the UK is poor, at less than 1%.

Capture Information

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.

Halibut, Atlantic (Farmed)
Halibut, Pacific
Sole, Dover sole, Common sole
Sole, Lemon
Turbot (Caught at sea)
Turbot (Farmed)


EU, 2019. Technical measures regulation. EU 2019/1241. Available at [Last accessed 13.09.2019].

EU, 2018. Commission Delegated Regulation (EU) 2018/2035 of 18 October 2018 specifying details of implementation of the landing obligation for certain demersal fisheries in the North Sea for the period 2019-2021. Available at [Last accessed 13.09.19].

EU, 2018. Regulation 2018/973 establishing a multiannual plan for demersal stocks in the North Sea and the fisheries exploiting those stocks. Available at [Accessed on 02.07.2019].

ICES, 2019. Sole (Solea solea) in Subarea 4 (North Sea). In Report of the ICES Advisory Committee, 2019. ICES Advice 2019, sol.27.4, Available at [Accessed on 3.07.2019].

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 [Accessed Sept 2018].

ICES, 2018. Sole (Solea solea) in Subarea 4 (North Sea). Available at [Accessed Sept 2018].

ICES, 2016. Request from France for updated advice on the ecosystem effects of pulse trawl. Available at [Accessed Aug 2016].

NSAC, 2015. Advice on the: Use of pulse trawls in the North Sea. Available at [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 [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.