Grey mullet

There is limited data on the thick-lipped grey mullet population (or stock) in this region. There is some evidence that populations have been in recent decline due to over-fishing.Route 2 scoring has been applied to this rating owing to the lack of reference points for fishing pressure and biomass. Thick-lipped grey mullet has a medium resilience to fishing pressure.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. A slow growth rate, late maturity, biannual spawning and high site fidelity makes them highly vulnerable to over-exploitation. 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, alongside the average weight of fish captured, which has been shown to be an indicator of over-exploitation. Therefore, there is concern for stock biomass and fishing pressure.Grey mullet are likely experiencing increased commercial pressure as a result of the limitations imposed on the bass fishery following their population crash.There are three species of grey mullet in UK waters; thick-lipped grey mullet, thin-lipped grey mullet and golden-grey mullet.

There is a lack of general management for grey mullet, which can be fished without limit and caught before having had the chance to reproduce.  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. Grey mullet is not subject to Total Allowable Catch (TAC) and quotas.  The Marine Management Organisation (MMO) has no minimum conservation reference sizes (MCRS) for any species of grey mullet, but in England the Inshore Fisheries and Conservation Authorities (IFCAs) may set MCRS for fish caught within their six nautical mile limit. Currently this is set at 42 cm in Southern IFCA, and 20 cm in Cornwall and North Western IFCAs. No other IFCAs have set a MCRS. This provides some protection to immature fish, however, length at fist maturity is documented at 29.5 cm for thick-lip grey mullet. Fish caught below this length would likely not have had the chance to reproduce. There are measures in place for bass which may inadvertently protect 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 generally associated with managing the nursey areas, rather than the stock. For example, in 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. In the EU, compliance with regulations has been variable, and there are ongoing challenges with implementing some of them. In the UK, 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). FMPs have the potential to be very important tools for managing UK fisheries. They will set out the policies to secure the long-term sustainability of our fish stocks for current and future generations and can include (data allowing): Targets for fishing pressure and biomass, with effective management to meet them; Timeframes for stock recovery; Use of technologies such as Remote Electronic Monitoring (REM) to support data collection, improve transparency and accountability; Consideration of wider environmental impacts of the fishery.

Gillnets in this area can encounter bycatch of non-target fish, mammals and birds. This includes the harbour porpoise which is vulnerable in Europe.Thick-lipped grey mullet is a coastal benthic fish found mostly on sandy bottoms.Fixed gillnets consist of a single vertical netting wall hanging between a float line and a weighted ground line which have little to no impact on the habitat, and very low levels of disturbance to the seabed. They are, however, recognised as the highest risk type of fishery for cetaceans globally, especially for small cetaceans in coastal areas. In the UK, the species most affected is the harbour porpoise, but a number of other species have been reported, and it should be assumed that most cetaceans are vulnerable to gill net bycatch. Gillnets pose serious risk to harbour porpoise wherever they are used around the UK and other cetaceans where their distribution overlaps with gill net use.Harbour porpoises are listed as Vulnerable in Europe by IUCN. They are on OSPAR’s List of Threatened and/or Declining Species and Habitats for the Greater North Sea and Celtic Seas, owing to evidence of a decline in populations, their sensitivity and the threat of incidental capture and drowning in fishing nets. They are also a priority species in UK and EU law (under which there are explicit bycatch requirements). Consequently, the UK designated seven Special Areas for Conservation for harbour porpoises, but these areas are not yet managed.The UK Dolphin and Porpoise Conservation Strategy lists harbour porpoise as having medium vulnerability to gillnetting for the UK as a whole. This is based on the species having a high sensitivity to gillnetting and medium exposure. The area of most concern is in the Celtic Seas, southwest of the UK, where most of the seabass gillnetting activity takes place. Exposure to gillnetting is high. A review of activities in the Bristol Channel Approaches Harbour Porpoise SAC lists commercial fisheries with bycatch (predominantly static nets) as a high risk, and a strandings report by Cornwall Wildlife Trust also shows that common dolphin bycatch is very high in this area. There is also bycatch of elasmobranch species which may be threatened or endangered. Porbeagle sharks are being caught as bycatch in gillnets but as they are a prohibited species, there is no official data on the numbers being caught and discarded. Spurdog bycatch is also thought to be of concern. The National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) highlighted continued problems of spurdog bycatch and despite a supposed real time avoidance programme being implemented, 50 tonnes were still landed in Cornish ports in 2019.Acoustic deterrent devices (ADDs), such as ‘pingers’, have been shown to be effective at reducing harbour porpoise bycatch in gillnets, but the reduction achieved so far has been small (<15% of the total number of cetaceans killed in UK fisheries), they may cause unwanted disturbance or displacement, and they may not be effective for other species.Larger mesh sizes used (100mm, south Wales) and the banning of fishing in inshore bass nursery areas in England and Wales, will reduce bycatch of small species and undersized seabass.Increasing evidence over the last decade has shown that seabirds are suffering mortality from bycatch, particularly in gillnets. Bycatch of seabirds in gillnet fisheries is estimated to kill ~400,000 birds globally, each year. Diving seabirds are generally more vulnerable than surface feeding seabirds. Most of the UK’s gillnetting takes place in southwest UK and therefore there is concern for seabird populations here (i.e., razorbill (Near Threatened, Europe: IUCN), puffin (Endangered, Europe: IUCN) and the herring gull, arctic skua and roseate tern (Red - Birds of Conservation Concern 4: the Red List for Birds (UK)).If lost, gillnets can continue to fish for several weeks before becoming tangled and bundled up, a phenomenon known as ghost fishing. Fishing gears represent an investment by fishermen, thus there are incentives to avoid losing or damaging gear.UK regulations to reduce the impacts of fishing on marine habitats and wider species are under development, in the meantime most EU regulation have been adopted. Under EU legislation, bycatch species should be managed within scientifically defined or, where data isn’t available, suitability precautionary sustainable exploration limits. If stocks fall below a certain threshold, measures can be brought in such as gear limitations (e.g., mesh size or depth of use), time and/or areas closures, and Minimum Conservation Reference Sizes (MCRS).

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