Mullet, Grey, Thicklip

Chelon labrosus

Method of production — Caught at sea
Capture method — Gill or fixed net
Capture area — North East Atlantic (FAO 27)
Stock area — North Sea, English Channel
Stock detail — 4, 7d, 7e
Picture of Mullet, Grey, Thicklip

Sustainability rating five info

Sustainability overview

Updated: November 2019.

There is no formal stock assessment of grey mullet and the status of the stock is unknown relative to reference points. There is little information available on mullet abundance in UK waters as there is a lack of data collection on the species. There is concern for biomass and concern for fishing pressure. Considering their vulnerable life history attributes, there is a lack of general management for grey mullet. There is no minimum conservation reference sizes (MCRS) for any species of grey mullet, but in England the IFCAs may set MCRS for fish caught within their six nautical mile limit. Grey mullet tend not to be a major commercial species but when fished commercially, they are a target or bycatch species which are mostly caught with gill nets, set close to the shore. Gillnets can entangle harbour porpoise and small sharks and may cause habitat impacts when lost or anchored to the sea floor.


Grey mullet belong to a large family, which comprises some 80 species of marine fish, known as Muglidae, and is a common inhabitant of marine coastal waters in Europe. The thick-lipped grey mullet is the most common of three species which occur in northern European waters. They are slow-growing, long-lived and late-maturing fish, which makes them susceptible to overfishing. They live to around 25 years old and mature around 9 years old (42 cm) for males and 11 years (47 cm) for females. Thicklipped mullet are thought to spawn on alternate years. Grey Mullet spawn in the English Channel and Irish Sea and potentially in estuaries in Eastern England. They spawn in open water and after around two to six weeks, the then juvenile fish move into inshore waters, especially estuaries. Their occurrence is impacted by temperature and they are often observed near the surface (0-10 m depth). Because of this, their large size, and east to capture, they can be popular with anglers.

Grey Mullet are catadromous (which means that they migrate from freshwater to seawater to spawn) and can be found in brackish lagoons and at the heads of estuaries because they can tolerate very low salinity levels. Grey Mullet are grazers, the scrape the surface off mudflats to eat diatoms and other algae off surfaces.

Stock information

Criterion score: 1 info

There is no formal stock assessment of grey mullet stocks and the status of the stock is unknown relative to reference points. There is little information available on mullet abundance in UK waters as there is a lack of data collection on the species. Grey mullet have a medium resilience to fishing pressure. A slow growth rate, late maturity, biannual spawning and high site fidelity makes them highly vulnerable to over-exploitation. Grey mullet are experiencing increased commercial pressure especially as a result of the limitations imposed on the bass fishery following their population crash. Therefore, there is concern for biomass and concern for fishing pressure.

There is conflicting evidence in biomass trends: Project Inshore stated in 2018 that the stock is considered stable or increasing and the current catch may be precautionary compared to previous exploitation levels. Also in 2018, the National Mullet Club suggested that mullet stocks have declined in recent years and commercial landings of grey mullet have been in decline since 2010.


Criterion score: 0.75 info

Considering their vulnerable life history attributes, there is a lack of general management for grey mullet. The Marine Management Organisation (MMO) has no minimum conservation reference sizes (MCRS) for any species of grey mullet, but in England the IFCAS may set MCRS for fish caught within their six nautical mile limit. Currently this is set at 30 cm in Southern and Kent & Essex IFCA’s. Northumberland IFCA has no byelaw size limit but recommends a minimum retention size of 47cm. No other IFCAs have set a MCRS. There are measures in place for bass which may inadvertently protect the grey mullet but there is also a lack of monitoring and catch reporting for the species, which limits the efficacy of management.

Management of grey mullet is more associated with managing the nursey areas, rather than the stock. For example, in the Eastern IFCA, most of the estuaries, and a high proportion of the shallow near shore areas, are covered by some form of Marine Protected Area designation. However, these designations do not necessarily account for the food habits of the species, particularly in its juvenile phase. There can be management including catch limits, closed areas and seasons, however these are not necessarily effective as catches appear to be poorly recorded and adequate catch levels are unknown.

There is no specific management plan for this stock, and it is not covered by the EU Multi Annual Management Plans, which focus on demersal and deep sea fisheries.

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.

Capture Information

Criterion score: 0.5 info

Gillnets and fixed nets can be very size selective, but can catch 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. MCS is pleased to see this progress, but notes that if catch rates of harbour porpoise do not show a decrease then scoring of this capture method may be affected. 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.

Basa, Tra, Catfish or Vietnamese River Cobbler
Cod, Atlantic Cod
Cod, Pacific Cod
Coley, Saithe
Hake, European
Monkfish, Anglerfish, White
Pollock, Alaska, Walleye
Spurdog, Spiny Dogfish, Dogfish, Rock Salmon or Flake
Sturgeon (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 [Accessed on 06.11.2019].

ASCOBANS. 2017. Cetacean Bycatch Monitoring and Mitigation Under EC Regulation 812/2004 in the Northeast Atlantic, North Sea and Baltic Sea - Interim Report Cetacean. 23rd ASCOBANS Advisory Committee Meeting: Le Conquet, 5 - 7 September 2017. Available at [Accessed on 06.11.2019].

Butterworth, A. and Burt, A. 2018. Vulnerability and Over-Exploitation of Grey Mullet in UK Waters. National Mullet Club. Available at [Accessed on 06.11.2019].

Calderan, S. and Leaper, R., 2019. Review of harbour porpoise bycatch in UK waters and recommendations for management. January 2019, WWF. Available at [Accessed on 06.11.2019].

Cook, R. and Heath, M. 2018. Population trends of bycatch species reflect improving status of target species. DOI: 10.1111/faf.12265. Fish and Fisheries. 19: 455-470. Available at [Accessed on 06.11.2019].

Froese R. and Pauly D. (Editors), 2016. Chelon labrosus, Thicklip grey mullet. Available at: [Accessed on 07.11.2019].

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 [Accessed on 06.11.2019].

Northridge, S., Kingston, A., Mackay, A. and Lonergan, M. (2011). Bycatch of Vulnerable Species: Understanding the Process and Mitigating the Impacts. Final Report to Defra Marine and Fisheries Science Unit, Project no MF1003. University of St Andrews. Defra, London, 99pp. Available at [Accessed on 06.11.2019].

Project Inshore MSC Pre-Assessment Database. 2013. Channel and North Sea (IV VII d-f): Grey mullet: Gill net. Available at [Accessed on 06.11.2019].

Save Our Seabass. 2018. Response to Sussex IFCA review of Nearshore Trawling and Netting Management. Available at [Accessed on 06.11.2019].

The National Mullet Club. 2013. The Value of Recreational Angling For Grey Mullet and the Case for Recreational-Priority Status. Available at [Accessed on 06.11.2019].

Tindall, C., Hetherington, S., Bell, C., Deaville, R., Barker, J., Borrow, K., Oakley, M., Bendall, V., Engelhard, G. (Eds), 2019. Hauling Up Solutions: Reducing Cetacean Bycatch in UK Fisheries. Final Workshop Report. 31 pp. Available at [Accessed on 06.11.2019].