Scallop, Queen, scallops

Aequipecten opercularis

Method of production — Caught at sea
Capture method — Demersal otter trawl
Capture area — North East Atlantic (FAO 27)
Stock area — Irish Sea
Stock detail — 7a: Isle of Man (Non-territorial waters outside 12nm)
Picture of Scallop, Queen, scallops

Sustainability rating five info

Sustainability overview

Updated: November 2019.

The Isle of Man Queen Scallop stock is at very low levels, and has been subjected to fishing levels higher than the scientific advice since 2013. There is no formal stock assessment containing reference points, but there is clear concern for both biomass and fishing pressure. The stock is at its lowest size on record, but there is no recovery plan in place and fishing quotas continue to be set higher than the scientific advice. Therefore this rating receives a critical fail for stock status and is a default red. The stock and the fishery extend beyond the Isle of Man territorial waters, but assessments and management only apply to the 0-12nm area, meaning the stock is not managed holistically. Queen scallops are usually caught with otter trawls in the Isle of Man because they are keen swimmers and are easily caught in nets. Otter trawls are less damaging to the seabed than dredges, and bycatch is generally lower. However, beyond 12nm little is done to mitigate the impacts of either capture method.


Queenies are a fast growing species with a maximum lifespan that rarely exceeds five years. Queen scallops are simultaneous hermaphrodites (i.e. an individual has both male and female reproductive organs) and become sexually mature at 1-2 years at approximately 40mm shell height. Although smaller than King scallops they can grow up to about 90mm. Queen scallops are broadcast spawners (i.e. they release eggs and sperms into the sea) and can spawn in both spring and summer. When one individual spawns, pheromones contained in the eggs and sperms released into the water column, signal to neighbouring scallops to release their own eggs and sperms ensuring synchronous spawning. Thus, in order for spawning (and subsequently recruitment) to successfully occur Queen scallops need to be present at relatively high densities. In low density populations there is a risk that the spawning stock may not be present at high enough densities to successfully reproduce (i.e. there are too few individuals around to come into contact for fertilisation), a phenomenon known as the Allee effect. They are usually found at depths down to about 100m on sand or gravel. It feeds on plankton and other organic material by filter feeding. They reach market size of 55mm (minimum landing size in Isle of Man; 40mm for rest of the Irish Sea) within 2-3 years depending on the available micro-algae feed from the water column.

Stock information

Criterion score: Critical fail info

Stock Area

Irish Sea

Stock information

The Isle of Man Queen Scallop stock is at very low levels, and has been subjected to fishing levels higher than the scientific advice since 2013. There is no formal stock assessment containing reference points, but there is clear concern for both biomass and fishing pressure. Queen scallops have a low vulnerability to fishing pressure (22 out of 100).

The estimated population biomass has been steadily decreasing - after peaking at over 20,000 tonnes in 2010, it declined sharply to around 5,000 tonnes in 2014 and in 2019 was 1,208t - the lowest level since data recording began in 1993. While there are no biological reference points, this decline is of significant cause for concern. The general scientific advice is not to exceed a fishing mortality of 20% of the stock biomass, which is the level thought to be replaceable by annual recruitment when taking natural mortality into account. However, to enable recovery of the stock as quickly as possible, actual fishing recommendations have been 0t since 2014. Actual removals in the past 5 years have averaged 40%.

While the queen scallop stock extends beyond Isle of Man territorial waters, stock assessments and management focus on the 0-12nm mile area, meaning there is not a complete understanding of the stock and management is not holistic.


The stock is not assessed or managed holistically, but is in a state of decline and subjected to overfishing. Outside of Isle of Man territorial waters, the queen scallop receives the following minimal management: a mandatory EU minimum landing size of 40 mm, some control of fishing effort for vessels over 15 metres in length, and a spawning closure in the Irish Sea from 1st April to 30th June. There are no entry restrictions into the fishery, no EU Total Allowable Catch (TAC), and no curfews.

While landings are restricted within Isle of Man territorial waters, additional landings are coming from the wider area of the biological stock, in non-territorial waters - ICES rectangles 36, 37 and 38E5. Initially, landings from non-territorial waters stayed high even though the stock and recruitment were declining, but landings are also now declining here. It is recommended that the Irish Sea queen scallop fishery be assessed and managed as a single biological stock.

The Manx Government has been encouraging the pan-Irish Sea management plan to implement harvest controls to manage fishing effort outside the IOM Territorial Sea. In 2015 the pan-Irish Sea working group introduced a voluntary ban on queen scallop fishing during May throughout the Irish Sea and to the west of Scotland. There was a consensus from the Pan-Irish Working Group that the following management measures are required: increased Minimum Landing Size (MLS), voluntary closed season, entry restrictions. To be effective, researchers advise that management must include suitable sites for closed areas for spawning and recruitment. In 2017, a consultation was held on introducing additional measures, but none have yet been put in place.

Capture Information

Queen scallops are active swimmers and when disturbed by tickler chains on otter trawl, quickly swim upwards and are captured in the fishing net. Otter trawls are used in the summer season when higher temperatures cause this swimming behaviour while skid dredges being used are used in the winter months.

Bycatch and discarding is monitored and managed by the IOM Government and the Manx Fish Producers Organisation. Bycatch is generally considered as low (<10%) in the Manx Queen scallop trawl fishery, but has increased in recent surveys. Bycatch significantly varied between fishing ground and time of year, but generally includes: fish (e.g. dab, cod, whiting, gurnards, monkfish), cephalopods (e.g. squid), elasmobranchs (e.g. smoothhounds, blonde ray, thornback ray, spotted ray, cuckoo ray, small-spotted catsharks, nursehounds) and invertebrates (e.g. Dead man’s fingers, oyster, sea squirts, star fish, whelk, sea urchin, crabs). However, many invertebrates are unidentifiable or not retained in the surveys.

Otter trawls catch exhibit higher levels of finfish bycatch but are more environmentally friendly to habitats compared to dredges. ‘Newhaven’ dredge cause less damage per catch compared to the traditional dredges.

Recent surveys have observed general increases in discard rates of undersized queen scallops but discard mortality from otter trawling is nearly a third of that observed in skid dredges. The introduction of the new Landings Obligation regulations require some bycatch (e.g. whiting) to be landed.

Mobile fishing gears cause the greatest levels of disturbance to marine benthic communities, either by direct (removal, burial or crushing), indirect (increase susceptibility to predation) or change biogeochemical properties of the environment. However, otter trawls are comparatively much less destructive than dredges.

Habitats and species of conservation concern (some of which are covered by UK BAP, EU Habitats Directive and OSPAR) have identified around the Isle of Man e.g. maerl beds, modiolus beds, sabellaria spinulosa and edwardsia timida. S. spinulosa (the tube-building polychaete worm) are particularly vulnerable because they are located within areas of high queen scallop densities. There is no statutory protection for S. spinulosa reefs in the UK.

Of concern is the use of bottom towed fishing gear in Marine Protected Areas (MPAs), especially sites to protect seabed features or where an appropriate impact or risk assessment has not been undertaken to demonstrate that the activity has no significant effect to the site.

There are few management measures to protect the habitat from fishing methods in the larger biological stock unit.


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Hinz, H., Murray, L.G. Gell, F., Hanley, L., Horton, N., Whiteley, H., Kaiser. M.J. Seabed habitats around the Isle of Man. Fisheries & Conservation report No. 12, Bangor University. pp.29.

Hinz, H., Murray, L. Malcolm, F. R. , Kaiser, M. 2012. The environmental impacts of three different queen scallop (Aequipecten opercularis) fishing gears. Marine Environmental Research, 73, 85-95pp.

Howarth, L. M. & Stewart, B. D. 2014. The dredge fishery for scallops in the United Kingdom (UK): effects on marine ecosystems and proposals for future management. Report to the Sustainable Inshore Fisheries Trust. Marine Ecosystem Management Report no. 5, University of York, 54 pp

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Sciberras, M., Hinz, H., Bennell, J., Jenkins, S., Hawkins, S., Kaiser, M., 2013. Benthic community response to a scallop dredging closure within a dynamic seabed habitat. Mar. Ecol. Prog. Ser. 480, 83-98. doi:10.3354/meps10198.

UK Scallop Management Conference, 2019. Report of first UK Scallop Management Conference, 4-5 February 2019, London, UK. Available at [Accessed on 07.11.2019].