Sole, Dover sole, Common sole

Solea solea

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

Sustainability rating two info

Sustainability overview

Updated: July 2019.

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. Gill netting here can encounter bycatch of harbour porpoise. Catch rates are not considered to be a threat to the population in the North Sea, but localised depletion may be an issue in some areas.

A number of MSC certified sole fisheries operate in the North Sea.

Biology

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

Criterion score: 0.25 info

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.

Management

Criterion score: 0.25 info

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 Landings 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 increased and fewer vessels were 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 exemptions in certain fisheries. 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.

A number of Marine Stewardship Council certifications are available for North Sea sole.


In the European Union (EU), EU fishing vessels can fish up to 12 nautical miles of any Member State coast, and closer by agreement. There is overarching fisheries legislation for all Member States, but implementation varies between fisheries, Member States and sea basins.
The EU Common Fisheries Policy (CFP) is the primary overarching policy. Its key environmental objectives are to restore and maintain harvested species at healthy levels (above BMSY), and apply the precautionary and ecosystem-based approaches to fisheries management. To achieve the MSY objective, the MSY exploitation rate is supposed to be achieved by 2020, but this seems unlikely to happen.
The CFP also introduced a Landing Obligation (LO) which bans the discarding at sea of species which are subject to catch limits. Some exemptions apply to species with high post-capture survival, and where avoiding unwanted catches is very difficult. These exemptions are outlined in regional discard plans. Despite quota ‘uplift’ being granted to fleets under the LO, available evidence suggests there has been widespread non-compliance with the policy, and illegal and unreported discarding is likely occurring.
Multi-Annual Plans (MAPs) are a tool for implementing the CFP regionally, with one in place or being developed for each sea basin. They specify fishing mortality targets and ranges for the main targeted species, as well as lower biomass reference points. If populations drop below these points it should trigger a management response. The MAPs also empower Member States to jointly apply measures such as closures, gear or capacity limits, and bycatch limits. There is concern however that the MAPs do not provide adequate safeguards to maintain all stocks at healthy levels.
The EU Technical Measures regulation addresses how, where and when fishing can take place in order to limit unwanted catches and ecosystem impacts. There are common measures that apply to all EU sea basins, and regional measures that vary between sea basins. Measures include Minimum Conservation Reference Sizes (MCRS, previously Minimum Landing Sizes, MLS), gear specifications, mesh sizes, closed areas, and bycatch limits.
The Control Regulation, which is being revised in 2019, addresses application of and compliance with the above, e.g. keeping catches within limits, recording and sharing data, and satellite tracking of vessels over 12 metres (VMS).

Capture Information

Criterion score: 0.5 info

Gillnets can be very size selective for the target fish but can be unselective at the species level for both non-target fish and for mammals, birds and turtles. Bycatch of harbour porpoise is known to occur in North Sea gillnets and can have implications for populations there.

In 2018, 90% of the catch was taken by beam trawling, 4.1% by gillnets, and 4.3% by trammel nets. Gillnets and fixed nets can be very size selective, but can bycatch species such as sharks, cetaceans and other marine mammals. Reports indicate that there is concern regarding the bycatch of cetaceans, particularly harbour porpoise, by gillnets. One of the areas of most concern is off the South West of England, where areas of higher gillnet fishing effort coincide with areas of larger harbour porpoise populations. However, these reports are based on highly uncertain data which cannot indicate the likelihood of bycatch either causing populations to decline or preventing populations from recovering. Progress on this issue is being made in some areas, with Defra leading work to improve monitoring and mitigation of cetacean bycatch (“Hauling Up Solutions”). A pilot project trialling self-reporting of bycatch is taking place in Cornwall, potentially backed up by electronic monitoring and VMS in time, and trialling the use of pingers and other mitigation technologies, which are known to deter harbour porpoise from entanglement in nets. MCS is pleased to see this progress, but notes that if catch rates of harbour porpoise do not show a decrease then scoring of this capture method may be affected. Because of gillnets’ durability (they are made of nylon), if lost, they can continue to fish for several weeks before becoming tangled and bundled up, a phenomenon known as ‘ghost fishing’. However, static nets, as with all gear, represent an investment by fishermen, and therefore there are incentives to avoid losing or damaging gear.

Alternatives

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

References

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, 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. 2019. Sole (Solea solea) in Subarea 4 (North Sea). In Report of the ICES Advisory Committee, 2019. ICES Advice 2019, sol.27.4, https://doi.org/10.17895/ices.advice.4873. Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/sol.27.4.pdf [Accessed on 03.07.2019].

Seafish, 2019. RASS Profile: Sole in the Southern North Sea (ICES Sub Area 4), Beam trawl. Available at https://www.seafish.org/risk-assessment-for-sourcing-seafood/profile/sole-in-the-southern-north-sea-ices-sub-area-4-beam-trawl [Accessed on 03.07.2019].

WWF, 2019. Remote Electronic Monitoring in UK Fisheries Management 2017. Available at https://www.wwf.org.uk/sites/default/files/2017-10/Remote%20Electronic%20Monitoring%20in%20UK%20Fisheries%20Management_WWF.pdf [Accessed on 02.07.2019].