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 — Baltic Sea (West), Skagerrak and Kattegat
Stock detail — 3a.20, 3a.21, 3c.22, 3b.23, 3d.24
Picture of Sole, Dover sole, Common sole

Sustainability rating three info

Sustainability overview

Updated: July 2019.

Since 2016 this stock has been in a good state (i.e. not overfished) and overfishing has not occurred since 2010, with an exception in 2017. Total Allowable Catches (TACs) have been reduced over the years, successfully reducing fishing pressure. In recent years TACs have matched the scientific advice, and catches from 2016-2018 averaged 93% of the TAC. Discards of sole are low, at 4%, but bycatch and discarding of other species could be a concern. In the trawl fisheries, the Kattegat cod stock may be bycaught, which has a recommendation for zero catch owing to its very overfished state. Gill netting in the Baltic Sea is likely to be adversely affecting the critically endangered central Baltic Sea harbour porpoise population.

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

Baltic Sea (West), Skagerrak and Kattegat

Stock information

Spawning-stock biomass (SSB) shows an increasing trend from 2015 and was above MSY Btrigger (2,600 tonnes) in 2018 (2,850t) and 2019 (2,802t). Fishing mortality (F) has increased in recent years and is at FMSY in 2018 (0.23). Recruitment has fluctuated below the average since 2004.

ICES advises that when the EU multiannual plan (MAP) is applied, catches in 2020 that correspond to F ranges in the plan are between 452 tonnes and 600 tonnes. According to the MAP, catches higher than those corresponding to FMSY (539 tonnes) can only be taken under conditions specified in the MAP, whilst the entire range is considered precautionary when applying the ICES advice rule. This is a 7.4% increase on the advice from 2018 because of increased recruitment.

As maturity-at-age is not determined for the species but set to age 3+, the true SSB for the stock is uncertain. Work is ongoing to improve the biological parameters for sole in the assessment. Work is also needed on understanding the connection of this stock to the North Sea stock and locations of nursery grounds.

Management

Criterion score: 0.25 info

Although this stock straddles the Baltic and the North Sea, it is managed under the EU multiannual plan (MAP) for stocks in North Sea and adjacent waters. 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 have been reduced over time, from the low 1000s in the 1990s, to 800-900 tonnes until 2011, to 200-500 tonnes since. In recent years TACs have matched the scientific advice, and catches from 2016-2018 averaged 93% of the TAC. Fishing pressure has generally decreased to sustainable levels.

The average discard ratio from 2014-2018 was 4%. Danish discard sampling at sea is carried out within EU programmes that began in 1995 in both Kattegat and Skagerrak.


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: 0.75 info

There is a directed gillnet fishery, mainly in Skagerrak, in spring and summer. 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. Gillnets cannot be specifically targeted to give clean catches of cod and a wide range of other species can become enmeshed, particularly in demersal set gillnets. In the Baltic Sea there are concerns about the bycatch rates of flatfish and juvenile cod. Harbour porpoise are highly prone to bycatch in bottom-set gillnets, due largely to their feeding habits on or near the seabed. Dead harbour porpoises exhibiting evidence of gillnet entanglements are found and reported regularly, so it is likely that bycatch in gillnets is adversely affecting the critically endangered central Baltic Sea population. Studies conducted between 1980 and 2005 indicated that at least 76 000 birds, mostly sea ducks, were killed annually in Baltic Sea gillnets. This number may have declined in more recent years, probably due to the consequential decline in sea duck populations. Because of their durability (gillnets are made of nylon), if lost the net can continue to fish, a phenomenon known as ‘ghost fishing’.

Drifting gillnets have been banned in the Baltic Sea since 2008.

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, 2016. Regulation (EU) 2016/1139 of the European Parliament and of the Council of 6 July 2016 establishing a multiannual plan for the stocks of cod, herring and sprat in the Baltic Sea and the fisheries exploiting those stocks. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32016R1139 [Accessed on 11.07.2019].

ICES. 2019. Baltic Fisheries Assessment Working Group (WGBFAS). ICES Scientific Reports. 1:20. 651 pp. doi: 10.17895/ices.pub.5256. Available at http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/Fisheries%20Resources%20Steering%20Group/2019/WGBFAS/1%20WGBFAS%202019.pdf [Accessed on 11.07.2019].

ICES. 2019. Sole (Solea solea) in subdivisions 20-24 (Skagerrak and Kattegat, western Baltic Sea). In Report of the ICES Advisory Committee, 2019. ICES Advice 2019, sol.27.20-24, doi: 10.17895/ices.advice.4753. Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/sol.27.20-24.pdf [Accessed on 25.07.2019].

Seafish, 2019. RASS Profile: Sole in Skagerrak, Kattegat and the Belts, Demersal trawls. Available at https://www.seafish.org/risk-assessment-for-sourcing-seafood/profile/sole-in-skagerrak-kattegat-and-the-belts-demersal-trawls [Accessed on 25.07.2019]