Lepidorhombus spp.: L. whiffiagonis and L. boscii

Method of production — Caught at sea
Capture method — Beam trawl
Capture area — North East Atlantic (FAO 27)
Stock area — Celtic Sea, west and southwest of Ireland, Bay of Biscay
Stock detail — 7b-k, 8a, 8b, 8d
Picture of Megrim

Sustainability rating three info

Sustainability overview

Updated: July 2020

Two species of megrim are landed to west of Britain and in the Bay of Biscay, megrim (Lepidorhombus whiffiagonis) and four-spot megrim (L. boscii). The former is more common and the only one assessed.

Megrim in the Celtic Sea, west of Ireland, and in the Bay of Biscay is in a very healthy state, at highest ever levels, and for the first-time fishing pressure is within sustainable limits. Megrim are mainly caught as part of the targeted fishery for hake, anglerfish, Nephrops and others, and as bycatch in fisheries for demersal species such as cod and haddock. Management measures are in place, but as catch limits apply to both species this hinders the ability to prevent overexploitation of either species. Trawling can have habitat impacts specifically on the seabed and contribute to high levels of bycatch. Beam trawling, especially using chain-mat gear, is more damaging to the seabed as it is a heavy gear that is designed for trawling over rough grounds. There are now several areas of deep water seabed on which all bottom trawling is banned to protect vulnerable deep water habitats within Celtic Sea and Biscay.


A common flatfish found in shelf seas throughout the northeast Atlantic. Megrim spawns in spring in deep water off Iceland, and between January and April along the edge of the continental shelf to the southwest and west of the British Isles. It is found at depths ranging from 50-800 m, but with the highest abundance around 100-300 m. For both sexes combined, 50% of individuals mature at about 20 cm at 2.5 years old. Males reach first maturity at a lower length and age than females. Megrim can attain a length of about 60 cm, although more usually 35-45 cm, and a maximum age of 14-15 years.

Stock information

Criterion score: 0 info

The stock is in a healthy state and fishing pressure is within sustainable limits.

The spawning-stock biomass (SSB) has been above MSY Btrigger (41,800 tonnes) since 2008 and continues to increase. SSB is now at its highest point in the time series (1984-2020) at 107,600 tonnes, in 2020. In 2020, the ratio of B:BMSY was 2.57. Fishing mortality (F) has decreased since 2005 and in 2019 it was 0.178, below Maximum Sustainable Yield (FMSY) (0.191) for the first time. In 2019, the ratio of F:FMSY was 0.93. Recruitment (R) has been relatively stable throughout the time series, since 2018 R has been above the time series average.

ICES advises that when the EU multiannual plan (MAP) for Western Waters and adjacent waters is applied, catches in 2021 that correspond to the F ranges in the MAP are between 12,706 tonnes and 27,748 tonnes. According to the MAP, catches higher than those corresponding to FMSY (19,184 tonnes) can only be taken under conditions specified in the MAP, whilst the entire range is considered precautionary when applying the ICES advice rule. The advice for 2021 is slightly lower than the advice for 2020 because the biomass estimates have been revised downwards in this assessment.

Two species of megrim are landed to the West of Britain and in the Bay of Biscay, megrim (Lepidorhombus whiffiagonis) and four-spot megrim (L. Boscii). The former is more common and the only one assessed.


Criterion score: 0.75 info

There are management measures in place, but, catch limits apply to both species of megrim which hinders the ability to prevent overexploitation of either species. Total catches have been equal to or below the advice.

The EU multiannual plan (MAP) for stocks in in the Western Waters and adjacent waters applies to this stock. The plan specifies conditions for setting fishing opportunities depending on stock status and making use of the FMSY range for the stock. ICES considers the FMSY range for this stock used in the MAP as precautionary. According to the MAP, for data-limited species such as four-spot megrim (L. boscii), fishing opportunities should be based on the best available scientific advice, but no ICES assessment has been requested and therefore there is no advice for this species.

Megrim species (Lepidorhombus spp.) are not totally separated within landings data, although, species-specific landings are estimated by ICES. Total Allowable Catch (TAC) limits apply to megrim species combined. Stock structure and even species identification/differentiation in landings is problematic for megrim. ICES considers that management of catches of the two megrim species, L. whiffiagonis and L. boscii, under a combined species TAC prevents effective control of the single-species exploitation rates, and could lead to overexploitation of either species. Currently L. whiffiagonis is in a healthy state and, as of 2019, is not being overfished, but, L. boscii is data deficient and the state of the stock is unknown.

The TAC covers the stock area, but also includes Divisions 7a and 8e which are not part of the assessment area. The 2015 and 2016 TAC was set 26% and 10% above advice, respectively. Between 2017 and 2020, the TAC has been set below (6-14%), and marginally above (3-5%) advice. The uptake of the 2019 TAC was undershot by 34%, and has been in line with or under the agreed TAC since 2015. Landings (total catch including discards) have not exceeded catch advice since 2015 and are generally below advice. In 2019, landings were just over 2/3 of the advised limit.

Beyond TACs, the fishery is managed by an EU minimum landing size (known as Minimum Conservation Reference Size) of 20 cm (25 cm in Skagerrak/Kattegat) for megrim, which was lowered from 25cm in 2000. Males reach the first maturity at a lower length and age than females. For both sexes combined, fifty percent of the individuals mature at about 20 cm and about 2.5-years. Although, dependant on distribution, length at first maturity can range between 19 and 28 cm, and consequently, megrim may be being caught before they have had chance to reproduce.

The average discard rate between 2015 and 2019 was 14%. In 2019, discards were 8% of the total weight of catch. Discarding of smaller megrim is substantial and also includes individuals above the minimum landing size of 20 cm.

Megrim is both a targeted and valuable bycatch species, in the mixed demersal trawl fishery in Divisions 7b-k, 8a-b and 8d. The reduction in fishing effort and fishing mortality on Megrim since the early 2000s may have contributed to the increase in biomass. A workplan began in 2019 under the Irish White Fish FIP, to improve the demersal trawl and seine fishery, for whitefish within division 7. The FIP objectives are to improve data for management decisions and to co-ordinate progress efforts towards MSY in whitefish fisheries.

Both the EU and UK have fishery management measures in place, which can include catch limits, targets for population sizes and fishing mortality, and controls on what fishing gear can be used and where. In the EU, compliance with regulations has been variable, and there are ongoing challenges with implementing some of them. There was a target for fishing to be at Maximum Sustainable Yield by 2020, but this was not achieved. The Landing Obligation (LO), an EU law that the UK has kept after Brexit, requires all fish and shellfish to be landed, even if they are unwanted (over-quota or below minimum size). It aims to promote more selective fishing methods, reduce bycatch, and improve recording of everything that is caught, not just what is wanted. Compliance with the LO is generally poor and actual levels of discards are difficult to quantify using the current fisheries observer programme.

In the UK, it is too early to tell how effective management is, as the Fisheries Act only came into force in January 2021. The Act requires the development of Fisheries Management Plans (FMPs) (replacing EU Multi-Annual Plans) but there are no details yet on how and when these will be developed. FMPs have the potential to be very important tools for managing UK fisheries, although data limitations may delay them for some stocks. MCS is keen to see FMPs for all commercially exploited stocks, especially where stocks are depleted, that include:
Targets for fishing pressure and biomass, and additional management when those targets are not being met
Timeframes for stock recovery
Technologies such as Remote Electronic Monitoring (REM) to support data collection and improve transparency and accountability
Consideration of wider environmental impacts of the fishery

Capture Information

Criterion score: 0.75 info

Megrim is caught by beam trawls in the Celtic Sea, West and southwest of Ireland, and Bay of Biscay, as bycatch in the mixed demersal trawl fishery, and in association with anglerfish (monkfish) by some fleets.

Megrim in the Celtic Sea, west of Ireland, and in the Bay of Biscay are caught in a mixed fishery predominantly by French followed by Spanish, UK and Irish demersal vessels. In 2019, the four countries together have reported around 95% of the total landings. Belgium also contributes to a small proportion of catch. Megrim are predominately taken by trawls (beam and otter trawls), which accounted for 97% of catch in 2018. 3% of catch was taken by other gears. Otter trawlers account for the majority of Spanish landings from ICES area 7. Most UK landings of megrim are made by beam trawlers fishing in the southwest of England and Wales. Irish megrim landings are largely made by multi-purpose vessels fishing in to the west and south of Ireland for gadoids such as cod and haddock, as well as plaice, sole and anglerfish. The majority of beam trawlers use meshes in the range of 80 to 89 mm.

Beam trawling is one of the least selective and high impact methods of fishing. Beam trawling, especially using chain-mat gear, is damaging to the seabed and known to have a significant impact on the benthic communities, although less so on soft substrates. Heavy gear tends to have a higher seabed impact than otter trawling. Seabed penetration depends on the sediment, and varies between 1 cm and 8 cm. In the Celtic Seas and Bay of Biscay, beam trawling causes abrasion (this pressure principally affects the seabed habitats and it is associated with bottom-contacting mobile fishing gear), and smothering, which can be caused by bottom trawling in soft sediment areas. In the Celtic seas beam trawlers operate on sandy grounds, where the seabed is suitable for beam trawling, and where sole, anglerfish, cuttlefish, and megrim are abundant. There are several areas of deep-water seabed on which all bottom trawling is banned to protect vulnerable deep-water habitats within the Celtic Seas and Bay of Biscay.

The common skate and spurdogs, are caught as bycatch in demersal trawl fisheries within these ecoregions. Therefore, interactions with Endangered, Threatened or Protected (ETP) species are considered within this fishery. Beam trawling is not a well-targeted fishing activity, with poor selectivity and the potential to catch a wide variety of non-target species including seabed dwelling organisms and invertebrates such as crabs, starfish and other shellfish. Megrim belongs to a very extended and diverse community of commercial species, some of the commercial species that exist in the same ecosystem are hake and anglerfish, however many other species are also found. Demersal species sharing the same habitat as megrim, may end up as incidental bycatch in mixed demersal fisheries.

Reduced feeding success and growth rates of benthivorous fish are potential secondary effects of trawling impacts, which has been observed for European plaice in gravel substrates in the Celtic Sea. Trawling in the Celtic Sea has also been associated with declining length-weight ratios for lemon sole, megrim and cod, implying that reduced prey availability imposed by trawling may lead to reduced carrying capacity, and these effects may compromise recovery of threatened stocks and ecosystems.

A number of areas are closed to fishing at certain times of the year, e.g. the Trevose box, an area of sea around 11,400 square miles extending from Trevose head in Cornwall to the Gower peninsular in South Wales from January to March. This is the spawning period for a number of demersal stocks, so while it is primarily intended to reduce catches of spawning cod, other stocks are likely to benefit. However, beam trawlers have been allowed to fish there since 2005.

Other potentially impacted species and habitats in the Southwest UK include the pink sea fan Eunicella verrucosa, which is listed as ‘vulnerable’ by the IUCN. However, EU vessels are required to report significant catches of corals and sponges to assist mapping these communities and move fishing operations at least 2 miles when they are encountered. There are now several areas of deep-water seabed on which all bottom trawling is banned to protect deep vulnerable deep-water habitats within Celtic Sea and Biscay.

Megrim (Lepidorhombus whiffiagonis) and four spot megrim (Lepidorhombus boscii), are both found together and are commercially exploited in the North eastern Atlantic waters. Both species can be found in similar depths: L. whiffiagonis range in depths of 50 to 800 m but more precisely around 100-300 m; L. boscii is found between 150-650 m, but mostly between 200-600 m. Although a comprehensive study on the role of megrim in the ecosystem of the complete sea area distribution has not been carried out, some general studies are available. Fisheries modify ecosystems through more impacts on the target resource itself, the species associated to or dependent on it (predators or preys), on the tropic relationships within the ecosystem in which the fishery operates, and on the habitat. At present, both the multi species aspect of the fishery and the ecological factors or environmental conditions affecting megrim population dynamics are not taken into account in assessment and management. This is due to the lack of knowledge of these issues.


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)


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