Turbot (Caught at sea)

Scophthalmus maximus

Method of production — Caught at sea
Capture method — Beam trawl
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea
Stock detail — 4
Picture of Turbot (Caught at sea)

Sustainability rating four 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. Beam trawls disturb seabed habitats in the North Sea and reduce the biomass and production of bottom-dwelling organisms. Beam trawls can also encounter relatively high levels of bycatch including Endangered, Threatened and Protected (ETP) species. Beam trawling, especially using chain-mat gear, is more damaging to the seabed than otter trawling as it is a heavy gear that is designed for trawling over rough grounds.

Biology

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.

Management

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: 0.75 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.

Beam trawls have the potential to take relatively high quantities of bycatch (> 50% of catch weight) including sharks, skates and rays and occasionally endangered, threatened and protected (ETP) species.

Beam trawls disturb seabed habitats in the North Sea and reduce the biomass and production of bottom-dwelling organisms. Sustained fishing within the core areas for this fishery are in relatively shallow areas of fine sand and sandy mud which are heavily fished. This has resulted in a shift from communities dominated by relatively sessile, emergent and high biomass species to communities dominated by infaunal, smaller bodied and faster growing organisms. The penetration depth of a beam trawl depends on sediment characteristics and varies between 1 cm and 8 cm. Trawls leave detectable marks on the seabed and the pressure exerted on the sea floor is strongly related to the towing speed, which is very high in flatfish fisheries as the gear itself is very heavy. The habitat risks are related to the types of seabed communities and other sources of seabed disturbance such as wave and tidal action. Within the North Sea, one of the more sensitive habitats that may be impacted by beam trawl is slow growing Sabellaria reef, frequently found in shallower areas of the southern North Sea. Further north, the large and very long-lived bivalve Arctica islandica (Ocean quahog), can also suffer damage in trawls. Some spatial management is in place but there remains a need to implement management measures in many designated marine protected areas to allow for the protection and recovery of these areas and sensitive designated features.

There are MPAs designated to protect seabed features from damaging activities in this region. The fishery overlaps with parts of these MPAs, but the proportion of the catch coming from these areas is expected to be relatively low in relation to the unit of assessment (i.e. less than 20% of the catch) and so these impacts have not been assessed within the scale of this rating. Given the important role that MPAs have in recovering the health and function of our seas, MCS encourages the supply chain to identify if their specific sources are being caught from within MPAs. If sources are suspected of coming from within designated and managed MPAs, MCS advises businesses to: establish if the fishing activity is operating legally inside a designated and managed MPA; and to request evidence from the fishery or managing authority to demonstrate that the activity is not damaging to protected features or a threat to the conservation objectives of the site[s].

The overall capacity and effort of the North Sea beam trawl fleet has been substantially reduced since 1995, likely due to a number of reasons, including effort limitations between 2008 and 2016 for the recovery of the cod stock. Fishing effort of the beam trawl fleet has shifted towards the southern North Sea to target sole over the past decade.

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 (Farmed)

References

Engelhard, G.H., Lynam, C.P., Garcia-Carreras, B., Dolder, P.J., Mackinson, S. 2015. Effort reduction and the large fish indicator: spatial trends reveal positive impacts of recent European fleet reduction schemes. Environmental Conservation, 42, 227-236.

EU, 2019. Technical measures regulation. EU 2019/1241. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32019R1241 [Accessed on 06.07.2020].

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 06.07.2020].

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 [Accessed on 06.07.2020].

FAO, 2001. Fishing gear types; beam trawls. Available at http://www.fao.org/fishery/geartype/305/en [Accessed on 06.07.2020].

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. 2020. Brill (Scophthalmus rhombus) in Subarea 4 and divisions 3.a and 7.d-e (North Sea, Skagerrak and Kattegat, English Channel). In Report of the ICES Advisory Committee, 2020. ICES Advice 2020, bll.27.3a47de Advice provided in 2020, https://doi.org/10.17895/ices.advice.5832.

ICES. 2020. Turbot (Scophthalmus maximus) in Subarea 4 (North Sea). In Report of the ICES Advisory Committee, 2020. ICES Advice 2020, tur.27.4. https://doi.org/10.17895/ices.advice.5914.

ICES. 2020. Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK). ICES Scientific Reports. 2:61. 1140 pp. http://doi.org/10.17895/ices.pub.6092.

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

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.