Common periwinkle

With limited data for periwinkles and an absence of stock assessments across the United Kingdom there is concern for populations’ biomass. Periwinkle landings are not well reported, and with no sustainable limit defined there is concern for fishing pressure.Route 2 scoring has been applied to this rating owing to the lack of reference points for fishing pressure and biomass. There are no assessments of the resilience or vulnerability of this species. MCS considers common periwinkle to have medium resilience to fishing pressure, based on several life history parameters. Periwinkles are reported to have low sensitivity to and high recoverability from biological removals.There is currently no formal assessment of periwinkle populations (or stocks) throughout the United Kingdom. In the absence of information, there is concern for biomass.The only available data relating to fishing pressure is landings data. Landings data is not a good indicator of fishing mortality or biomass because it does not account for changes in fishing effort or catchability. Periwinkle landings data is provided by the MMO. Officially, relatively small numbers of periwinkle landings are recorded in the UK compared to other commercial fisheries e.g., whelks (source MMO data). Over the last five years, recorded landings of periwinkle (Littorina spp.) have more than halved from 21 tonnes in 2018 to 9 tonnes in 2022, whilst their commercial value per kg has increased in the same time frame, from £1.31/kg to £2.04/kg. However, government reports and others have noted that periwinkle landings are likely to be substantially underreported, therefore there is concern for fishing pressure.

Overarching management measures are absent for periwinkle populations within the United Kingdom.Periwinkle fisheries are data poor. The absence of stock assessments prevents the definition of catch limits and presents several challenges for management.There are currently no regulations in place to control the quantities of periwinkles harvested commercially. It is difficult to accurately assess the size of periwinkle fisheries as they are unregulated, under reported, and often black market in nature, as reported by NIFCA, government reports and others. The scale of IUU (illegal, unregulated and unreported) fishing for periwinkles is unknown.There is no minimum conservation reference size (MCRS) in place for periwinkle(s) caught in UK waters. Periwinkles taken below the size of maturity (SOM - the size at which 50% of the population is sexually mature) would likely not have had the chance to reproduce. In the UK, SOM ranges between 11 and 17mm, varying geographically. If a minimum legal size is implemented it should be greater than the minimum size at which spawning occurs and to allow a minimum of one winter spawning (e.g., 16mm Northern Ireland).Certain regions within the United Kingdom have regulations in place (e.g. harvest control rules such as a minimum legal size and closed seasons) for the collection of periwinkles. See additional periwinkle ratings here.MCS is keen to see publicly available Fishery Management Plans 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 evidenceTimeframes for stock recoveryImproved data collection, transparency and accountability, supported by technologies such as Remote Electronic Monitoring (REM)Consideration of wider environmental impacts of the fishery

Periwinkles are gathered by hand on coastal shores. This is a low impact way of catching shellfish. There are rarely any seabed impacts and no bycatch of unwanted species, although disturbances can occur on certain substrates.Periwinkles are found on a variety of intertidal habitats including rocks, stones, and gravels. They can also be found on softer sediment such as mud and sand, they are one of the only Littorinid species to be found on both hard and soft substrates. They are particularly abundant on broken shores or where there are many crevices, congregating near boulders and larger cobbles when on mixed substrates (i.e. exposed bedrock, boulders, cobbles, pebbles, gravel and sand).Hand gathering is the lowest impact way of catching shellfish as there are rarely any seabed impacts and no bycatch of unwanted species. However, it is still important to control these activities. In some UK areas, hand gathering is so extensive that beaches have had to be closed to prevent too many shellfish from being taken.The most significant potential impacts to non-target rocky shore dwelling plants and animals from hand gathering activities:Given the nature of periwinkle collection, it has the potential to cause disturbance to nesting or feeding birds.Physical damage from boulder turning and trampling disturbance can cause a reduction in habitat stability and biodiversity.It can adversely impact organisms that depend on upper rock surfaces, such as seaweeds.UK regulations to reduce the impacts of fishing on marine habitats and wider species are under development, in the meantime most EU regulations 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).