Dover sole

Stock Status Score: 0.75

Irish Sea sole is considered fully fished, with concern for the fishing level.

Stock assessments are carried out by the International Council for Exploration of the Sea (ICES). This rating is based on the assessment published in 2026.

The stock assessment defines reference points for fishing pressure (F) and biomass (B). For fishing pressure, there is a target to keep F at or below Maximum Sustainable Yield (MSY). For biomass, there is no target. However, there is a trigger point (MSY Btrigger). Below this level, F should be reduced to allow the stock to increase. Because BMSY is not defined, the Good Fish Guide applies its own definition of 1.4 x MSY Btrigger. Also, as Flim is not defined, the Good Fish Guide applies its own definition of 1.4 x FMSY.

Spawning stock biomass (SSB) of sole declined from a peak of 11,938 tonnes in 1970, and fell below MSY Btrigger (3,129 tonnes) in 1996, and again in 2006. With ongoing high fishing pressure and low recruitment years, SSB declined further and fell below Blim (2,235 tonnes) from 2007 until 2016. SSB has recovered to above MSY Btrigger in 2018, and fluctuates above this threshold. In 2026, SSB is estimated at 4,231 tonnes, which is above MSY Btrigger but below BMSY proxy (4,381 tonnes). Therefore, the stock is considered to be fully fished.

Fishing mortality (F) has exceeded both FMSY (0.164) and Fpa (0.183) for much of the time between 1970 and 2009. After which, fishing pressure declined, dropping below FMSY in 2010, and remaining below this threshold until recently, as in 2025, fishing pressure was 0.197 which is above FMSY and Fpa, but below the Flim proxy (0.230). Therefore, there is concern for the fishing level.

ICES advises that when the MSY approach is applied, catches in 2027 should be no more than 548 tonnes. This is a 0.55% increase in advice from the previous year.

Management of the Target Stock Score: 0.5

Alignment with Scientific Advice Score: 0.5

Monitoring, Control and Surveillance Score: 0.25

Despite being managed through a combination of the Landing Obligation, minimum conservation reference sizes (MCRS), and technical measures, fishing pressure on sole in in the Irish Sea is concerningly high. Catches and TACs have remained in line with advice in the past five years, but there is little consideration for the mixed fishery with zero-catch plaice in the area. The fishery benefits from a well-developed Monitoring, Control and Surveillance (MCS) system, with effective enforcement and low levels of illegal, unreported and unregulated (IUU) fishing.

The sole fishery in the Irish Sea is managed through Total Allowable Catches (TACs) and a range of technical measures.

Sole is caught in a mixed fishery with plaice in this area. Fishing mortality for both species is affected by technical management measures, including gear selectivity requirements and mesh size regulations. The current UK technical gear measures are as follows:

• Beam Trawls: 80 mm mesh cod-end, with a headline panel of at least 180 mm mesh.
• Otter Trawls:
  • 12m and Under: 80mm mesh cod-end, and 80mm square mesh (if low catches of gadoids).
  • Over 12m: 100mm mesh cod end, and 100mm square mesh panel (if low catches of gadoids, skates, and rays).

Sole in this area has been subject to the Landing Obligation (LO) since 2020. The LO was introduced to improve catch reporting, reduce unwanted catches, and encourage more selective fishing practices. However, some exemptions apply to this fishery, including de minimis exemptions for beam trawls fitted with Flemish panels, allowing certain catches to be returned to sea. A minimum conservation reference size (MCRS) of 24 cm applies throughout the fishery. Discard rates have increased in recent years, rising from an average of 6% during 2003–2017 to 14.3% during 2018–2024, before increasing further to 19.1% in 2025. This increase occurred despite a reduction in MCRS for Belgian vessels (25cm to 24cm) in 2025, a change that would be expected to reduce the proportion of undersized fish being discarded.

The stock is managed through a Total Allowable Catch (TAC) system. Between 2020 and 2026, TACs were set in line with, or below, ICES catch advice each year. Catches have remained below advice and TACs over the past five years, reaching 54.7-95.1% of the advised level. In 2025, the TAC was set equal to advice at 609 tonnes, with estimated catches totalling 579 tonnes, equivalent to 95.1% of both the TAC and advised limit.

The Irish Sea sole fishery operates within the Celtic Seas ecoregion. While no mixed-fisheries analysis was available for the Irish Sea in 2025, sole is caught as part of a mixed demersal trawl fishery and therefore could overlap with some of the choke species identified elsewhere in the region, including cod, haddock, and whiting, all of which are currently subject to zero-catch advice. It not possible to achieve all advised single-stock catches simultaneously, and therefore choke species are largely overlooked. However, evidence from other Celtic Seas sole fisheries suggests that interactions between sole and these species are generally limited. Additional protection for cod is provided through a seasonal spawning closure in the western Irish Sea.

Sole is more commonly caught alongside plaice. Given that the plaice stock in this area is currently subject to zero-catch advice, having declined substantially over the past decade and remained below MSY Btrigger since 2022, any changes in sole fishery management or increases in fishing effort could affect plaice catches and potentially hinder stock recovery.

Monitoring, control and surveillance of UK fisheries are delivered through licensing, vessel tracking, statutory reporting, observer coverage, inspections and other monitoring systems. All commercial fishing vessels must hold a valid UK fishing licence to operate in UK waters, although exemptions may apply to some unpowered vessels under 10 metres. Depending on the area, target species and activity, additional permits or authorisations may also be required.

Vessel tracking requirements vary by vessel size, area and administration through Vessel Monitoring Systems (VMS) and, where applicable, inshore VMS (iVMS).

• Vessels 12 m and over must report their position every two hours via VMS.
• Vessels under 12 m report their position continuously where iVMS applies, or may operate full VMS where required by licence conditions or when fishing offshore.

Reporting of fishing activity, catches, landings, discards and port movements is mandatory, with logbooks supporting traceability:

• Vessels 12 m and over submit electronic logbooks under Council Regulation 1224/2009.
• Vessels 10–12 m (and under 10 m Producer Organisation vessels) use paper logbooks, updated daily and submitted within 48 hours of landing.
• Non-PO vessels under 10 m are generally exempt unless required by licence conditions.

UK vessels must also carry fishery observers when directed, providing independent verification of activity and catch. Remote Electronic Monitoring (REM), using cameras, sensors and positional data, is being increasingly deployed to improve data quality and support enforcement. Its rollout is supported by the Fisheries Act 2020 and the Joint Fisheries Statement.

Together, these measures help prevent illegal, unreported and unregulated (IUU) fishing through vessel licensing, catch documentation, positional monitoring, statutory reporting and compliance checks. Enforcement action may include financial penalties, prosecution, licence suspension or other sanctions. The UK has committed to reducing IUU fishing and maintains a blacklist of vessels involved in such activities. This rating reflects full compliance with UK monitoring, control and surveillance requirements.

The Marine Conservation Society views Remote Electronic Monitoring (REM) with cameras as one of the most cost-effective tools for providing reliable fisheries data and aiding informed management decisions. Fully monitored fisheries enhance collaboration, data accuracy, stock recovery, and reduce impacts on marine wildlife and habitats. However, the full potential of REM may only be achieved when it tracks fishing location and documents catch and bycatch, particularly where vulnerable species and habitats are at risk. 

The Fisheries Act (2020) requires the development of Fisheries Management Plans (FMPs) (replacing EU Multi-Annual Plans) in the UK. 43 FMPs have been proposed and are at various stages of development and implementation, these should all be published by the end of 2028. FMPs have the potential to be very important tools for managing UK fisheries, although data limitations may delay them for some stocks. It is also essential the UK governments define and adopt a standardised approach or model across the four nations to a universally defined FMP design, to ensure the consistence, quality and coherence of all the proposal FMPs. 

The Marine Conservation Society is keen to see publicly available Fishery Management Plans for all commercially exploited stocks, especially where stocks are depleted, that include: 

• An overview of the fishery including current stock status, spatial coverage, current fishing methods and impacts 

• Targets for fishing pressure and biomass, and additional management when those targets are not being met, based on the best scientific evidence 

• Timeframes for stock recovery 

• Improved data collection, transparency, and accountability, supported by technologies such as Remote Electronic Monitoring (REM) 

• Consideration of wider environmental impacts of the fishery, including habitat impacts and minimising bycatch 

• Stakeholder engagement 

An Irish Sea demersal FMP has been proposed, coordinated by DAERA, Defra, and the Welsh Government which incorporates this stock. At the time of writing, it is too soon to know whether proposed management measures will be effective in managing the stock. For more information about this FMP and expected progress and timelines, see [https://www.gov.uk/government/collections/fisheries-management-plans#published-fmps]. 

Capture Method Score: 0.5

Habitat Impacts: 0.5

Bycatch Impacts: 0.5

Vulnerable and ETP Species: 0.5

Ecosystems and Trophic Webs: 0.25

Otter trawls are likely to cause some damage to the seabed, including damage to benthic communities and vulnerable marine habitats. Although interactions with zero-catch gadoid stocks are limited in this mixed demersal fishery, bycatch of plaice may be affecting the stock's recovery. This gear type can also interact with ETP species. While sole landings have remained stable, beam trawling may continue to exert pressure on an ecosystem already affected by historic fishing and climate change.

The majority of Irish Sea sole landings come from beam trawls (93%), followed by otter trawls (6.4%), and other gears (<1%). In 2025, total catches were 469 tonnes.

Otter trawls make direct contact with the seabed, causing penetration and abrasion of habitat features. The extent of seabed impact depends on gear type, sediment composition, and the area's natural resilience. For instance, regions that are used to tidal and wave disturbances are less sensitive, whereas areas untrawled areas may be more vulnerable.

In the Celtic Seas ecoregion, impacts from bottom trawling are variable. Most fishing grounds consist of sand, which is less susceptible to damage than habitats like reefs and seagrass beds. In 2022, it was estimated that 61% of the Celtic Seas seabed shallower than 800m was trawled, consisting of 66% of 0-200m zone, and 59% of the 200-800m zone.

There are several Marine Protected Areas (MPAs) within the Celtic Sea and Bristol Channel, which are designated to protect sensitive benthic habitats and species that may be vulnerable to bottom-towed fishing gears. Restrictions on bottom-towed gears are already in place in some areas, including parts of Haig Fras SAC, East of Haig Fras MCZ, and South of Celtic Deep MCZ. However, protection across the MPA network remains incomplete, with several sites only recently being considered through the MMO's Stage 3 byelaw process. As such, some designated features may remain exposed to disturbance from bottom trawling, potentially limiting habitat recovery and the achievement of conservation objectives. Given the critical role MPAs play in recovering marine health and supporting ecosystem function, the Marine Conservation Society urges supply chain actors to verify whether their sources originate from within MPAs. If so, businesses should confirm that fishing operations are legally conducted and request evidence from the fishery or managing authority to ensure activities do not harm protected features or compromise conservation objectives.

Demersal otter trawls have the potential to take relatively high quantities of bycatch, including those of conservation concern. Bycatch data is limited in many UK and EU fisheries as they are generally not well monitored. In the Celtic Sea, trawl fisheries are known to interact with several elasmobranch species of conservation concern, including the prohibited common skate complex, an endangered, threatened, or protected (ETP) species. Otter trawls are also associated with some of the highest bycatch rates of common dolphins in the region. Although the sole fishery is likely responsible for only a small proportion of these interactions, they demonstrate that otter trawl gear can affect vulnerable and protected species, and therefore its impacts cannot be considered negligible.

The Irish Sea sole fishery operates within the Celtic Seas ecoregion. While no mixed-fisheries analysis was available for the Irish Sea in 2025, sole is caught as part of a mixed demersal trawl fishery and therefore could overlap with some of the choke species identified elsewhere in the Celtic Seas region, including cod, haddock, and whiting, all of which are currently subject to zero-catch advice. That said, catches of these species have declined steadily over the past decade, but otter trawls remain responsible for the majority of landings (54–78%). Also, evidence from other Celtic Seas sole fisheries suggests that interactions between the Irish Sea sole fishery and cod, haddock, and whiting are considered low, and therefore the fishery's contribution to bycatch and any associated impacts on stock recovery is likely to be limited. Additional protection for cod is provided through a seasonal spawning closure in the western Irish Sea. However, because the sole fishery is concentrated in the eastern Irish Sea, this closure is not expected to provide protection to sole stocks or reduce the benthic impacts associated with the sole fishery in the area.

More common bycatch species in this fishery include anglerfish, plaice, lemon sole, and cuttlefish. Plaice discard rates in the Irish Sea are very high, with the majority of catches discarded, but the stock assessment does assume a 40% survival rate for discarded fish. Plaice biomass has declined steadily in past decades and has remained below MSY Btrigger since 2022. This combination of reduced stock size and poor recruitment has resulted in zero-catch advice for the stock. Otter trawls account for some plaice landings (14%) and discards (28%) in the area, indicating that the sole otter trawl fishery has some influence on plaice stock stability. Consequently, any increase in fishing effort or changes in management measures within the sole fishery could affect plaice mortality and potentially hinder stock recovery.

Sole occupy a mid-trophic-level position in the food web, feeding mainly on benthic invertebrates and serving as prey for larger fish and marine mammals. The Celtic Seas ecosystem has changed considerably over the past century, driven primarily by fishing and, more recently, climate change. From the mid- to late 20^th century, high fishing pressure depleted many commercial stocks, including cod, whiting, sole, plaice, and herring, as well as large elasmobranchs such as the previously abundant common skate complex. These declines altered trophic interactions and coincided with reductions in several seabird populations linked to changes in prey availability. Although some stocks have since recovered, others remain depleted. More recently, climate-driven changes in oceanographic conditions have altered plankton communities, shifted species distributions, and increased the prevalence of warm-water species. Together, changes in temperature, predation pressure, and food availability are thought to have reduced the productivity of commercial finfish stocks and slowed their recovery.

Alongside these ecosystem-wide changes, catches of sole in the Irish Sea have gradually declined since the 1980s, suggesting that the fishery's overall influence on the wider environment may also have lessened over time. However, sole is primarily caught using bottom trawls, which can disturb seabed habitats and generate multi-species bycatch. As a result, habitat disturbance and incidental catches may continue to exert pressure on an ecosystem that has already been substantially altered by fishing and environmental change.