Turbot (Caught at sea)

Scophthalmus maximus

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 Turbot (Caught at sea)

Sustainability rating three info

Sustainability overview

Updated: July 2020.

The latest stock assessment indicates that the stock of Turbot in the North Sea is in a healthy state with biomass above MSY Btrigger. Fishing mortality is estimated to be just above FMSY. Management of turbot and brill is under a combined species Total Allowable Catch (TAC) which prevents effective control of fishing pressure on either species. 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.


Turbot belongs to a small family of left-eyed flatfish (both eyes on the left of the body), known collectively as the Scophthalmidae. This family of fish is confined to the north Atlantic basin and includes megrim and brill. Turbot becomes sexually mature at an age of 3-5 years and in most parts of its range spawns in April to August, females each producing up to 10-15 million eggs. Turbot is one of the fastest growing flatfish, with females growing faster than males, in the North Sea reaching a length of around 30 cm (males) and 35 cm (females) in about 3 years. In the Baltic Sea growth is slower, and the males become sexually mature at a length of 15 cm, the females at 20 cm. By 10 years of age growth rates have reduced to 1-2 cm per year for females and less than 1 cm per year for males. Consequently, females are larger than males at any given age. Turbot can attain a length of 1m and a weight of 25 kg. Maximum reported age 25 years. For some reason males are generally more abundant than females. Turbot is distributed from Iceland, down the coast of western Europe and into the Mediterranean. Turbot are typically found at a depth range of 10 to 70 m, on sandy, rocky or mixed bottoms. It is one of the few marine fish species that inhabits brackish waters. Turbot appears to be a rather sedentary species, although some adult migration may occur.

Stock information

Criterion score: 0.25 info

The stock of turbot in the North Sea is in a healthy state. Spawning stock biomass (SSB) has been steadily increasing since 2005 and has been above MSY Btrigger (6353 tonnes) since 2013, no values for Bmsy are available. In 2019, SSB was estimated to be 8211 tonnes, an 8% decrease from 2018 which was estimated at 8939 tonnes. Recruitment has been variable, and the estimated recruitment for 2019 (8095 tonnes) is the second highest in the time-series.

Fishing mortality has been below Fmsy (0.36) since 2012. However, in 2018 and 2019 fishing mortality is estimated at 0.368 and 0.367 respectively, just above Fmsy. In 2019, landings were 3100 tonnes. ICES advises that when the MSY approach is applied, catches in 2021 should be no more than 3948 tonnes. This advice is a 13% decrease from 2020 due to a change in the basis for advice, from the precautionary approach to the MSY approach. In the last 3 years, the combined TAC for turbot and brill has not been fully utilised. In 2019, only 55% of the combined TAC (8122 tonnes) was taken of which turbot had the largest share (38%).

Catches consist predominantly of immature fish, which is having a negative impact on the potential yield from the stock. As turbot is a fast-growing species, reduction in the exploitation on younger ages would lead to an increase in maximum sustainable yield, supporting the need to reduce catching turbot under its length at maturity of between 30 and 35 cm for males and females respectively.

ICES note that a fisheries-independent survey, having both adequate catchability of large flatfish and covering the entire distribution area of the stock, is needed to improve the assessment. To address this issue in future assessments, a Dutch science-industry partnership initiated a new fisheries-independent beam trawl survey for turbot and brill in 2019. Once a period of 5 years is covered, the index of this new survey is a potential candidate to include in the turbot assessment.


Criterion score: 0.75 info

Management of turbot in the North Sea requires considerable improvement. Turbot is a high value bycatch species in fisheries for plaice and sole and is classed as a bycatch species under the EU North Sea Multiannual Management Plan (NSMAP) for demersal stocks which came into effect in 2018. 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 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. However, MCS has concerns that the NSMAP is not being adhered to for all bycatch stocks, especially where adequate advice is available, as is the case with turbot. This has resulted in catch advice for turbot being considerably higher and well above MSY which, if followed, is expected to reduce the biomass.

Turbot in the North Sea is managed under a combined total allowable catch (TAC) together with brill. ICES have indicated that management of brill and turbot under a combined species TAC prevents effective control of the single-species exploitation rates which can result in high-grading and discarding of the lesser value species and overexploitation of the high value one, turbot. Since 1 January 2019, turbot is entirely under the landing obligation.

Catches consist predominantly of immature fish, which is having a negative impact on the potential yield from the stock. As turbot is a fast-growing species, reduction in the exploitation on younger ages would lead to an increase in maximum sustainable yield, supporting the need to reduce catching turbot under its length at maturity of between 30 and 35 cm for males and females respectively. There is no official EU minimum conservation reference size (MCRS) for brill, although some regional authorities have applied their own but this is often under the size of maturity.

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

Turbot is a valuable bycatch species in beam (67%) and otter trawl (25%) and gillnet and trap (8%) fisheries for flatfish (plaice and sole) and other demersal species. Quota restrictions apply only to the North Sea, where around 90% of the catches in the Northeast Atlantic are taken.

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. 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.


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)
Sole, Dover sole, Common sole
Turbot (Farmed)


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].

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. 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 https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2018.327.01.0017.01.ENG [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 https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0973&from=EN [Accessed on 02.07.2019].

ICES, 2019. Turbot (Scophthalmus maximus) in Subarea 4 (North Sea). Available at http://ices.dk/sites/pub/Publication%20Reports/Advice/2019/2019/tur.27.4.pdf [Last accessed 15.09.2019].

ICES, 2018. ICES Advice: 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].

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].