Native oyster

Not enough is known about wild populations of native oysters in the UK. The species is of conservation concern thanks to historic declines. Currently, fishing pressure is low.Route 2 (data limited) scoring has been applied to this rating owing to the lack of reference points for biomass and fishing pressure. There is no data available about native oyster vulnerability, so other indicators have been used. As they mature at a relatively young age (2-3 years) and are not particularly long lived, at up to 15 years, we consider this species to have medium resilience to fishing pressure.Native oysters have been identified as one of the most threatened species that requires conservation action in the UK, having experienced a 95% population decline in abundance over the past century. It is listed as a priority species on the UK list of Priority Habitats and Species and is assigned critical status due to population declines across Europe. Oyster reefs are also a feature of conservation importance, due the habitats that they offer.Some conservation efforts are beginning to show promise. Assessments from 2015 in Loch Ryan fisheries showed indications of stock increases, although more recent updates and management details for this fishery are not readily available. However, other areas such as Sussex and Cornwall as showing local declines. The conservation concerns, contradicting local trends, and general lack of wider population data mean there is concern for biomass of native oysters. Clear evidence of population recovery would be needed to suggest healthy biomass for the species.The only available data regarding fishing pressure on oysters in the UK is through landings data from the Marine Management Organisation (MMO). There may be some unreported hand gathering of oysters, although there are only occasional reports of illegal hand gathering, suggesting this is not a large part of the fishery. In areas with permits for fishers, landing reports may also be required. Available landings data from the MMO indicate that reported landings of native oysters have drastically declined, from 70 to 9 tonnes between 2016-2020, likely due to Brexit and coronavirus reducing market demand. No absolute catch or landing limits are set in open fisheries to assess fishing pressure against, however, effort is managed somewhat through limited permit allocation and closure of fisheries where stocks are not recovering. Owing to the reduced oyster landings overall, and there is currently no concern for fishing pressure.

Management of oyster fishing is patchy, and does not appear to have been effective at helping native oysters to recover from historically low abundance. Considerable improvements and better data are needed.In England, oyster fisheries are often managed by Inshore Fisheries Conservation Authorities. In Scotland, most naturally occurring oysters belong to and are managed by the Crown Estate. However some grounds are privately managed due to private ownership of grounds or access to fisheries (known as several orders). For example the Loch Ryan fishery and areas of the Blackwater, Crouch, Roach and Colne Estuaries Marine Conservation Zone are privately owned or managed.Due to the huge decline in native oyster abundance across UK seas and the lack of consistent population studies, it is difficult to assess the effectiveness of current management measures. Long term data is not available to assess recovery from historic depletion levels. Indications from areas that have been recently assessed in Sussex and Cornwall show that oyster populations are not consistently stable or increasing. In Loch Ryan, management prior to 2015 is reported to have increased the stock although more recent updates and management details for this fishery are not readily available. There is limited accessible data for other private grounds or fisheries.In some areas stock assessments have been used to guide oyster catch restrictions. Restrictions in England are determined by the local Inshore Fishery Conservation Authority (IFCA), bylaws. For oysters, these include measures such as limiting fishing times and areas, landings per trip, gear restrictions and seasonal closures in the spawning season. The exact closed seasons vary slightly but include the summer spawning period between May and August. Privately owned sites can have specific license restrictions such as landings caps and minimum landing sizes, but current details are not readily accessible. Recently some areas have been fully closed to fishing due to poor stock or population status.Minimum landing sizes, and the way that they are measured, vary. For example, in Kent and Essex the oyster must pass through a 70mm gauge, while in Cornwall the oyster can rest on top of a 67mm gauge, allowing smaller oysters to be landed. Male and female oysters are understood to mature at 5 cm, so these sizes are likely to protect juveniles. However, as larger oysters are more fertile, smaller landing sizes may limit reproductive potential.Across the UK, a number of restoration projects are in the process of being developed and implemented. The Oslo/Paris convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR), suggests that to ensure long-term preservation of the species and habitats, upscaling of oyster restoration is needed. An increase in restored oyster reefs may help to support wild fishery stocks as spat settle outside of conservation areas and increase the availability of locally adapted oysters. The UK Fisheries Act came into force in January 2021 and requires the development of Fisheries Management Plans (FMPs). 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). FMPs are currently in development, but the scope of them remains unclear. They 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 publicly available 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, based on the best available 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

Oyster dredging can be damaging to seabed habitats and species and is known to occur in marine protected areas. However, some vulnerable habitats and species are protected through closed areas, closed seasons and gear restrictions. There could be some concern for bycatch, although many species are returned to the sea alive in oyster fisheries.Around 82% of UK native oysters catches are by dredges, the remainder are mainly caught in other mobile gears and in pots and traps. Dredges are designed to disturb the seabed and penetrate sediments which has significant impacts on the seabed and the species associated with it.No evidence is available about the specific impacts of oyster dredges on the seabed, therefore, the impacts are assumed to be similar to scallop dredges that fish in the same environment. Dredge impacts are of particular concern in areas where biogenic reefs (created by organisms settling together on the seabed) are damaged and the species removed. Although native oysters themselves have been shown to maintain relatively high recruitment in some disturbed areas, ecologically important biogenic oyster reefs have been lost around UK waters due to high levels of dredging. Oyster reefs are themselves Features of Conservation Interest (FOCI) in England and Wales.Oyster dredging in UK waters is undertaken in conservation or protection areas. The Fal fishery occurs in a special area of conservation (SAC) and although the fishery mainly occurs in the zone of least sensitivity (zone 1) impacts include occasional ‘minor disturbance’ of maerl. In the Essex blackwater marine conservation zone mixed sediments and native oyster beds are protected features. The blackwater fishery is currently closed due to oyster stock concerns however, dredging is theoretically permitted under flexible bylaws when open. The Loch Ryan fishery area does not have any conservation designations. Certain marine protected areas are also closed to dredging in all circumstances. In some areas bylaws protect the beds from over-exploitation by limiting harvesting to non-mechanical means. The overall impacts of all dredge fisheries depend on the total hours, gear size and spatial extent of all vessels in the fishery.To improve monitoring and reporting of fishing activity, MCS would like to see remote electronic monitoring (REM) with cameras implemented, used and enforced. To reduce the impacts of fishing on the marine environment we would like to see a just transition to the complete removal of bottom towed gear from offshore Marine Protected Areas designated to protect the seabed. We also want to see reduction and mitigation of environmental impacts including emissions and blue carbon habitat damage.

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