Brill

Stock Status Score: 0

Brill in this region is considered underfished and harvested sustainably.

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.

The relative exploitable biomass (B/BMSY) of this stock has declined in recent years but has remained above MSY Btrigger (0.5) since the start of the time series. In 2026, relative exploitable biomass is 1.49. Therefore, the stock is considered under fished.

Relative fishing pressure (F/FMSY) has declined after a peak in 2001 but has remained below FMSY (1) throughout the time series. In 2025, relative fishing pressure was estimated at 0.32, and therefore the stock is harvested sustainably.

ICES advises that when the MSY approach is applied, catches in 2027 should be no more than 3,254 tonnes. This is an increase of 5.4% from the previous year, which reflects an increase in the estimated biomass.

Management of the Target Stock Score: 0.25

Alignment with Scientific Advice Score: 0.25

Monitoring, Control and Surveillance Score: 0.25

Few management measures in the North Sea and English Channel are specifically designed for brill. Nevertheless, the stock is currently abundant and appears to be harvested sustainably. Although a species-specific TAC was only introduced in 2024, catch limits have been set in line with scientific advice and have effectively controlled fishing mortality. The fishery has a well‑developed and effective Monitoring, Control, and Surveillance (MCS) system with reliable enforcement and low levels of IUU activity.

As a predominantly bycatch species, North Sea brill is managed largely through measures designed for mixed demersal fisheries. The stock falls within the EU North Sea Multiannual Plan (MAP) and is taken primarily by trawl fisheries targeting sole and plaice, with smaller catches from trammel and gillnet fisheries. Consequently, fishing mortality is controlled mainly through technical measures applied to these fisheries, including gear selectivity requirements, cod-end mesh size regulations, and restrictions on beam length. In UK waters, minimum mesh size requirements apply to bottom trawls and nets operating in the North Sea and English Channel.

An 80 mm mesh size is commonly used in the North Sea sole fishery and is effective at retaining marketable sole, but it is also likely to capture immature brill. In UK waters of the English Channel (ICES Divisions 7d and 7e), a minimum conservation reference size (MCRS) of 30cm is in place. However, there is no MCRS in the North Sea. This increases the risk of recruitment overfishing, as immature fish may be removed before contributing to spawning biomass and reproductive output. Dutch Producer Organisations have applied a voluntary minimum market size for brill. However, this was reduced from 32 cm to 25 cm between 2017 and 2026. Although increasing mesh sizes would likely reduce catches of juvenile brill and improve stock resilience, such measures would also reduce catches of marketable sole.

Additional protection is offered by the Plaice Box in the North Sea - a closed area established in 1989. It restricts vessels using towed gear with engine power over 300 horsepower and enforces a maximum aggregated beam length of 9m. This 9m limit is also in place within the UK’s 12 nautical mile zone. Although established to protect juvenile plaice, the closure could provide some indirect benefits for brill.

Brill falls under the Landing Obligation (LO), which aims to improve catch reporting, reduce unwanted catches and encourage more selective fishing practices. As a result, brill caught in North Sea otter trawl and net fisheries, and in beam trawl fisheries in the English Channel, must generally be landed. However, survivability exemptions apply to some beam trawl fisheries in Scottish and EU waters of the North Sea, allowing certain catches to be returned to the sea. Despite the LO, average discard rates between 2023 and 2025 were estimated at around 5.1% of total catches.

Historically, brill and turbot were managed under a combined TAC covering ICES Subarea 4 and UK waters of Division 2a. This management did not align with ICES stock areas, limiting effective control of species-specific exploitation rates and potentially encouraging high-grading and overexploitation of the higher-value brill stock. Since 2024, a specific TAC for brill has been implemented, improving species-specific management. Brill TACs have been set below ICES advice since 2024, as they account for third-country catches (approximately 0.55% of removals). Catches in 2024 were below both the TAC and advised catch level. Catches also remained below advised levels under the previous combined TAC system.

Despite these measures, brill remains largely managed within a mixed-fishery context. ICES notes that, under current fishing patterns, it is not possible to simultaneously achieve all single stock catch advice within the North Sea demersal fishery, primarily due to the zero-catch advice on cod making it a choke species. However, interactions between brill and cod are considered limited, as fisheries catching brill generally record negligible cod landings.

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.

Similar monitoring, control and surveillance requirements apply to EU vessels under the EU Fisheries Control Regulation, including vessel tracking, electronic catch reporting, landing declarations, inspections and traceability requirements. The revised Regulation entered into force in January 2024 and introduces a phased requirement for REM with onboard cameras on EU vessels over 18 m identified as high risk for Landing Obligation non-compliance, alongside wider increases in digital reporting and traceability. Implementation and enforcement are undertaken by individual Member States, so observer coverage, inspection activity, enforcement effort and REM deployment can vary between countries and fisheries.

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 

A Southern North Sea and Eastern Channel mixed flatfish FMP has been proposed, coordinated by Defra that 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: 0.75

Habitat Impacts: 0

Bycatch Impacts: 0.25

Vulnerable and ETP Species: 0.75

Ecosystems and Trophic Webs: 0.5

Gillnets have minimal impacts on benthic habitats because they cause little disturbance to the seabed. However, their non-selective nature can result in relatively high levels of bycatch, including ETP species such as harbour porpoise. In some areas, current harbour porpoise bycatch rates are considered unsustainable and are hindering population recovery. While current levels of brill removal are unlikely to have a significant effect on food-web dynamics, the bycatch associated with net fisheries has the potential to affect ecosystem function and alter trophic structure.

Landings of brill in the North Sea and English Channel are from beam trawls (50.3%), otter trawls (34.7%), trammel and gillnets (11.3%), and other gear types (3.7%). In 2025, a discard rate of 5.1% was recorded, an increase from 2024 (3.1%).

Fixed nets, consisting of vertical net(s) suspended between a float line and a weighted ground line, have minimal impact on benthic habitats as they cause little disturbance to the seabed. However, their non-selective nature means they can be associated with relatively high levels of bycatch. Brill is caught as a bycatch species in mixed flatfish fisheries. Consequently, the direct contribution of brill to the bycatch of other non-target species is considered limited, but not negligible.

There are several Marine Protected Areas (MPAs) within the western English Channel that are designated to protect sensitive benthic habitats and vulnerable species. However, static-net fishing remains permitted in most offshore MPAs overlapping this fishery. In inshore waters, additional restrictions on static-net fisheries may apply through local IFCA byelaws. As some MPAs encompass important nursery grounds for commercial and vulnerable species, restrictions on all fishing gears, including static nets, can provide additional conservation benefits to mobile species.

Fixed nets are associated with bycatch of marine mammals, seabirds, fish, elasmobranchs and endangered, threatened and protected (ETP) species. Globally, gillnet fisheries are recognised as posing one of the greatest threats to cetaceans, particularly small coastal species. Within the Celtic Seas ecoregion, harbour porpoises are the cetacean species most frequently affected by net bycatch. Available evidence suggests that current bycatch levels are unsustainable, exceeding potential biological removal thresholds, and contributing to population declines in the region. Harbour porpoises are listed by OSPAR as threatened and/or declining in the Greater North Sea and Celtic Seas and are protected under UK and EU legislation, which includes requirements to minimise bycatch. Other species commonly caught in fixed nets include grey seals, and guillemots.  While brill is only a bycatch species in fixed-net fisheries, there is evidence that these gears can have significant impacts on ETP species, including unsustainable bycatch rates of harbour porpoise.

Nylon nets, if lost, 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.

Brill occupies a mid- to upper-trophic-level position in the marine food web, feeding primarily on crustaceans and small fish while also serving as prey for marine mammals and larger predatory fish. The North Sea and English Channel ecosystems have undergone substantial change in recent decades due to climate change and fishing pressure. In the North Sea, rising sea temperatures have altered trophic pathways through declines in zooplankton abundance, while reductions in key forage species such as sandeels have affected energy transfer through the food web. While in the English Channel, many higher-trophic-level species, including gadoids and elasmobranchs, have declined, while lower-trophic-level invertebrates have become increasingly prominent in landings. The loss of top predators can trigger cascading effects on ecosystem structure and functioning.

However, the relatively high bycatch rates associated with this gear type, including the incidental capture of ETP species, have the potential to place additional pressure on ecosystems that are already subject to multiple environmental and anthropogenic stressors. This is of particular concern in areas where cetacean bycatch is occurring at levels capable of affecting population stability. Declines in species such as harbour porpoise could result in changes in trophic webs and ecosystem functioning.