Sole, Lemon

Microstomus kitt

Method of production — Caught at sea
Capture method — Gill or fixed net
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea, Skagerrak and Kattegat, Eastern English Channel
Stock detail — 4, 3a, 7d
Picture of Sole, Lemon

Sustainability rating three info

Sustainability overview

Updated: February 2020.

Lemon sole is a valuable bycatch species in mixed demersal trawl fisheries and this stock is classed as data limited. The latest stock assessment undertaken in 2019 indicated that fishing mortality was not of concern and was below the proxy for maximum sustainable yield (FMSY). The state of the biomass is unknown in relation to reference points and whilst there is no evidence of overexploitation, there is also no evidence that the stock is increasing. The index of relative population size in this assessment decreased in comparison to previous years, but by less than 20%. Considering this and the likely significant reductions in fishing pressure on the stock in the last decade, the biomass has not been assessed as ‘of concern’ by MCS. The stock is currently managed under a combined total allowable catch (TAC) with witch flounder and whilst this is considered insufficient to manage catches, the International Council for Exploration of the Sea (ICES) have advised that the removal of the TAC for lemon sole would present a low risk of the stock being exploited unsustainably. Whilst gill net fisheries can be very selective with regards to targeted fish species, they can encounter bycatch of vulnerable species including porpoise, sharks and seabirds. Bycatch of harbour porpoise in the North Sea is not considered to be a threat to the population, but localised depletion may be an issue in some areas.

Biology

Lemon sole is a widely distributed flatfish which is found in shelf waters of the North Atlantic, from the White Sea and Iceland southward to the Bay of Biscay. Lemon sole appears to prefer sandy and gravelly substrates, living deeper and at higher salinity and lower temperature than plaice or sole. Sexual maturity occurs in males at 3-4 years and at 4-6 years in females and between 20-30 cm. Lemon sole may live for about 17 years and can attain lengths of over 60 cm. They spawn in spring and summer, April to August.

Stock information

Criterion score: 0.25 info

Stock Area

North Sea, Skagerrak and Kattegat, Eastern English Channel

Stock information

The latest stock assessment undertaken by the International Council for Exploration of the Sea (ICES) in 2019 indicated that fishing mortality was not of concern and was below the proxy for maximum sustainable yield (FMSY). The state of the biomass is unknown in relation to reference points and whilst there is no evidence of overexploitation, there is also no evidence that the stock is increasing. The index of relative population size in this assessment decreased in comparison to previous years, but by less than 20%. Considering this and the likely significant reductions in fishing pressure on the stock in the last decade, the biomass has not been assessed as ‘of concern’ by MCS. ICES advises that when the precautionary approach is applied, catches should be no more than 4279 tonnes in each of the years 2020 and 2021.

The stock is considered data limited (ICES category 3) and so the assessment of biomass has drawn on a combination of survey data and catch data to provide an index of relative abundance. The fishing pressure has been estimated using a length-based indicator. ICES indicate that improved information on age and length distributions in landings and discards, from most countries participating in the fishery, would be required in order to conduct a fully analytical assessment. A fishery-independent index covering the entire distribution area of the stock and targeting all length classes of lemon sole could also improve the assessment.

Management

Criterion score: 0.5 info

Lemon sole is considered a valuable bycatch species and there are no specific management objectives for this species in this region. The stock is currently managed under a European Union (EU) combined total allowable catch (TAC) with witch flounder and the International Council for Exploration of the Sea (ICES) have indicated that should TAC management still continue, it should be under single TACs for each stock/species that correspond with the stock areas. The current TAC only covers ICES Division 2.a and Subarea 4 and so no does not cover catches in 3.a and 7.d. In 2018 though, ICES advised that the removal of the TAC for lemon sole would present a low risk of the stock being exploited unsustainably. This was because there was no indication of a targeted fishery for lemon sole - unlike witch in some areas. Catches of lemon sole in recent years have been below those recommended by ICES.

As a bycatch species, management under the EU North Sea Multiannual Management Plan (NSMAP) for demersal stocks (2018) applies. The NSMAP aims to ensure that exploitation of living marine biological resources restores and maintains populations of harvested species above levels which can produce the Maximum Sustainable Yield (MSY) and that the precautionary approach to fisheries management is applied. Bycatch stocks do not have specific targets and limits under the NSMAP but are supposed to be managed in accordance with the best available scientific advice and the precautionary approach when no adequate scientific information is available.

There is no minimum conservation reference size for lemon sole, meaning it can be landed at any size and it is currently subject the EU landing obligation, meaning it should be legally retained by fisheries in this region and not discarded.

General EU fisheries management.

In the 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 was supposed to be achieved by 2020, but this seems very unlikely to happen for all fisheries.
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 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

Lemon sole are generally taken as bycatch in mixed fisheries by otter trawlers (73%), beam trawlers (22%), demersal seines (2%), and gillnets (2%). Gillnets and fixed nets can be very size selective, but can encounter bycatch species such as birds, sharks and marine mammals. Reports indicate that there is concern regarding the bycatch of cetaceans, particularly harbour porpoise, by gillnets. In the North Sea, catch rates are not considered to be a threat to the population, but localised depletion may be an issue in some areas. 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 the durability of gillnets (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)
Megrim
Plaice
Sole, Dover sole, Common sole
Turbot (Caught at sea)
Turbot (Farmed)

References

ASCOBANS, 2009. Conservation Plan for Harbour Porpoises in the North Sea as adopted at the 6th Meeting of the Parties to ASCOBANS, Bonn, Germany. 16 - 18 September 2009. Available at https://www.ascobans.org/sites/default/files/document/ASCOBANS_NorthSeaPlan_MOP6.pdf [Accessed on 31.07.2019].

Calderan, S. and Leaper, R., 2019. Review of harbour porpoise bycatch in UK waters and recommendations for management. January 2019, WWF. Available at https://www.wwf.org.uk/sites/default/files/2019-04/Review_of_harbour_porpoise_in_UK_waters_2019.pdf [Accessed on 31.07.2019].

Eigaard, O.R., Bastardie, F., Breen, M., Dinesen, G.E., Hintzen, N.T., Laffargue, P., Mortensen, L.O., Nielsen, J.R., Nilsson, H.C., O'Neill, F.G., Polet, H., Reid, D.G., Sala, A., SkOld, M., Smith, C., Sorensen, T.K., Tully, O., Zengin, M., Rijnsdorp, A.D., 2016. Estimating seabed pressure from demersal trawls, seines, and dredges based on gear design and dimensions. ICES Journal of Marine Science, Volume 73, Issue suppl 1. Pages i27-i43. Available at https://academic.oup.com/icesjms/article/73/suppl_1/i27/2573989 [Accessed 9.12.2019].

EU, 2019. Technical measures regulation. EU 2019/1241. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32019R1241 [Last accessed 13.09.2019].

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].

FAO, 2001. Fishing gear types; bottom trawls. Available at http://www.fao.org/fishery/geartype/205/en [Last accessed 23.09.2019].

Hiddink, J., Jennings, S., Kaiser, M., Queiros, A., Duplisea, D. and Piet, Gerjan. 2006. Cumulative impacts of seabed trawl disturbance on benthic biomass, production, and species richness in different habitats. Canadian Journal of Fisheries and Aquatic Sciences 63 (2006) 4. 63. 10.1139/f05-266.

ICES, 2019. Bycatch of protected and potentially vulnerable marine vertebrates - review of national reports under Council Regulation (EC) No. 812/2004 and other information. Published 30 August 2019. Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/byc.eu.pdf [Last accessed 24.2.2020].

ICES, 2019. Greater North Sea Ecoregion - Ecosystem overview. Published 12 December 2019. Available at http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/EcosystemOverview_GreaterNorthSea_2019.pdf [Last accessed 24.2.2020].

ICES, 2019. Lemon sole (Microstomus kitt) in Subarea 4 and divisions 3.a and 7.d (North Sea, Skagerrak and Kattegat, eastern English Channel). ICES Advice on fishing opportunities, catch, and effort Greater North Sea ecoregion. Published 28 June 2019 Version 2: 3 September 2019. Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/lem.27.3a47d.pdf [Last accessed 27.02.2020].

ICES, 2018. Bycatch of small cetaceans and other marine animals - review of national reports under Council Regulation (EC) No. 812/2004 and other information. Published 11 September 2018. Available at https://www.ices.dk/sites/pub/Publication%20Reports/Advice/2018/2018/byc.eu.pdf [Accessed on 31.07.2019].

ICES, 2018. EU request for ICES to provide advice on a revision of the contribution of TACs to fisheries management and stock conservation. ICES Special Request Advice Northeast Atlantic ecoregions. Available at http://www.ices.dk/sites/pub/Publication%20Reports/Advice/2018/Special_requests/eu.2018.15.pdf [Last accessed 27.02.2020].

Lakkeborg, S. 2005. Impacts of trawling and scallop dredging on benthic habitats and communities. FAO Fisheries Technical Paper. No. 472. Rome, FAO. 2005. 58p.

OSPAR, 2017. Intermediate Assessment 2017: Harbour Porpoise Bycatch. Available at https://oap.ospar.org/en/ospar-assessments/intermediate-assessment-2017/biodiversity-status/marine-mammals/harbour-porpoise-bycatch/ [Accessed on 31.07.2019].

Tillin, H.M., Hiddink, J.G., Jennings, S. and Kaiser, M. J., 2006. Chronic bottom trawling alters the functional composition of benthic invertebrate communities on a sea-basin scale. Marine Ecology Progress Series. Vol. 318. 31-45.