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 (Territorial waters 0-12nm)
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. In addition, 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. This, coupled with management measures such as MPAs, area closures, and curfews to avoid catching brown crabs (which are more mobile overnight), means that there is a reduced risk to the ecosystem compared to dredging.


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.


Management measures are in place, but quotas have been set above scientific advice and the stock is continuing to decline. In addition, 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.

The Isle of Man queen scallop trawl fishery operates form July-October each year. The 2018 quota was 794 tonnes - a 20% decrease from the previous year owing to a decline in abundance. It was split between the trawl and dredge fisheries, with 687t going to the former and 97t going to the latter. Reported landings by the trawl fishery were 659 tonnes. However, the stock is not expected to be able to support this level of fishing, as the TAC equates to a removal of 53% of the biomass (more than double the recommended level of 20%). Queen scallops in the Isle of Man have been fished above scientifically recommended levels since 2013, and the biomass is continuing to decline. Scientific advice was therefore for no fishing to take place in the stock assessment unit in 2019. However, for socio-economic reasons, a TAC of up to 242 tonnes could be sustained by the stock while maintaining the fishery. The Scallop Management Board instead opted to reduce the 2018 TAC by 20% and add an additional precautionary 20%, taking it to 476t - around twice the recommended level.

In addition to the TAC, management measures for 2018 included:
A freeze on capacity - since 2016 licences have only been given to vessels that were fishing for queen scallops during 2010-2012.
Two closed areas where fishing for king and queen scallops was prohibited.
Queenie conservation zones where dredging for queen scallops was prohibited.
Spawning protection closure (1st April to 31st May). This closure was voluntary in 2017 and statutory in 2018.
Voluntary Irish Sea closure (1st April to 30th June).
Weekend ban and a daily curfew (06:00 - 18:00).
Weekly catch limits for trawl fishery (maximum of 2,695 kg).
Individual quotas for dredge fishery (16,166 kg per vessel).
Minimum landing size (55 mm).

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. There are no restricted management measures in this part of the fishery, although landings have also declined here. It is recommended that the Irish Sea queen scallop fishery be assessed and managed as a single biological stock.

Capture Information

Most queen scallops are caught with otter trawls and there are protective measures throughout the Isle of Man to protect vulnerable habitats. Most substrate is predominantly sand or fine gravel.

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 varies 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.

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.

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.

An area in excess of 85% of the territorial sea is not trawled for queen scallops with the mean footprint of the fishery, relatively stable at around 12% of the territorial sea. The Queenie Conservation Zone, is a designated dredge box with a TAC for the dredge fishery.

Conservation zones in Manx waters promote spawning potential and trawling is prevented from occurring in vulnerable marine habitats. Since June 2016, around 3% of Manx waters are protected as MPAs, with additional seasonal or temporary protected areas.

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. In territorial waters, protection is provided, however, the efficacy of protection outside territorial waters is unknown.

Future Fisheries, the Isle of Man’s Fisheries Strategy, highlights the importance of ecosystem management, and emphasises the significant role of Marine Protected Areas in protecting the marine environment and supporting sustainable fisheries.


Bangor University, 2016. Fisheries and Conservation Science Group: Scallop fisheries: Fishery. Available at: [Accessed on 06.11.2019].

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Isle of Man Government, 2018. Closed or restricted area maps: Marine Protected Areas maps. Available at: [Accessed on 06.11.2019].

Isle of Man Scallop Management Board, 2019. Minutes of the meeting held at DEFA in St John's on 21st May 2019. Available at [Accessed on 06.11.2019].

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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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