Cockle, cockles

Cerastoderma edule

Method of production — Caught at sea
Capture method — Hand-gathering
Capture area — North East Atlantic (FAO 27)
Stock area — England
Stock detail

Eastern IFCA district only


Sustainability rating three info

Sustainability overview

The cockle fishery is economically and environmentally important to the EIFCA district, valued at 4.25 million pounds in 2016-2017 and providing an essential food source for over-wintering birds. There is significant interannual variability in cockle populations, which in turn impacts the total allowable catch (TAC) permitted each year. For example, the TAC has ranged from 957 tonnes (2011) to 8,609 tonnes (2016)). These fluctuations are mainly caused by atypical mortalities. The IFCA have monitored and analysed atypical mortalities which have been considerably high in the recent decade. In 2008, the IFCA produced contingency measures to mitigate the risk and impact of atypical mortalities. IFCAs survey cockle populations annually: the 2017 survey indicated that there were exceptional quantities of cockles available but there are some negative population signs.

Historically, the fishery was exploited by hand gathering, then technology (particularly dredging) enabled a more efficient method of harvesting cockles. These efficiency gains have resulted in a boom and bust-style exploitation of the stock. Since 2008, dredging has not been as prominent in the Wash, as conditions have not been deemed suitable to support a dredge fishery. Therefore, the fishery is now mostly exploited by hand. The handwork fishery usually involves rakes and shovels. Prop-washinga is commonly used to harvest cockles, where fishers turning their vessels in tight circles around a single point. The propa (the propeller) washes cockles out of the sediment and into a pile that is more easily collected than when cockles are buried under the surface of the sediment.

Biology

The common cockle is a bivalve mollusc found buried in mud and sand in estuaries and on beaches. Cockles have distinctive rounded shells that are slightly heart shaped. It is a bivalve (two identical shells) belonging to the family Cardidae meaning heart-shaped. An organ called a siphon allows the animal to feed and breathe whilst buried in the sand. They can jump by bending and straightening the foot - the end bit- which is often coloured red and called the red nosea. The shell size is up to 5cm long, although average sizes tend to be around 3-4cm. Maturity occurs at a shell length of around 2cm. Cockles spawn from March to August, although exact times will vary from region to region.

Stock information

Criterion score: 0.75 info

Stock Area

England

Stock information

Summary
There is concern for both biomass and fishing mortality. A recent stock assessment shows conflicting trends including declines in population size, high-density patches and meat yields. There is a shift towards targeting increasingly smaller cockles, which the Inshore Fisheries Conservation Authority (IFCA) believes is a worrying trend.

Cockles are considered to be a high resilience species.

Management

Criterion score: 0.25 info

The majority of the fishery is managed under The Wash Fishery Order (WFO). Management measures implemented in the fishery generally include licences, closed areas to protect spat (juvenile cockles), a daily quota of 3-tonnes, anchor requirements to reduce the impact to the seabed when prop-washing, a Code of Best Practise requires minimal damage to habitats and vulnerable species such as seals.

The TACs are calculated and vary annually and the fishery can be closed early to protect the stock.

There is no Minimum Landing Size (MLS). This is because it is difficult to determine an appropriate minimum landing size as their size does not just depend on age.

Since 2008, cockle populations have been negatively impacted by mass mortality events. The cause of this is not yet known. The mass mortality events have predominantly impacted larger, faster-growing cockles and resulted in few cockles surviving their initial spawning events. Therefore, management in recent years has focused on protecting the most vulnerable cockle populations.

Monitoring
Eastern IFCA undertakes annual cockle survey. Catch information has to be recorded and provided to EIFCA on a weekly basis.

Enforcement
A relatively high level of resource is dedicated to enforce the fishery to ensure compliance for the cockle fishery and Marine Protected Area designations (including Special Area of Conservation, Special Protected Area).

Capture Information

Criterion score: 0.25 info

A common method of hand-caught fishing to harvest cockles is prop-washing. This is where fishers spin their vessels in tight circles in order to wash cockle out of the sediment, making them easier to catch. Prop washing is less efficient than blowing out and creates less disturbance to the ground. Hand raking can be assisted by a process known as blowing out. This is where a vessel uses wash from its propeller to blow the cockles out of the seabed, prior to grounding the vessel at low water, where cockles are hand raked into sacks and placed aboard the vessel.

Bycatch
Bycatch may include invertebrates such as shore crabs. The impact of the fishery on endangered protected or threatened species is considered low. To further mitigate this the fishery operates in a highly-designated area which is protected by a Special Area of Conservation and the fishery has adopted a code of conduct to reduce its impact on ETP species and vulnerable habitats.

Habitat
Through best practice, prop-washing causes a negligible effect on the habitat. However, if done incorrectly, may result in deep troughs and/or large piles of cockles left out of the sediment which die quickly from exposure. The Wash cockle fishery lies in one of the most highly designated marine areas of the UK including a European Marine Site (EMS) that is a Special Area of Conservation under the Habitats Directive.

Cockles are targeted in highly dynamic sandbanks in the intertidal zone. High risk features include Ross worm reef (Sabellaria spinulosa reef), Eelgrass (Zostera marina) and sub-tidal boulder and cobble communities in The Wash and North Norfolk Coast Special Area of Conservation (SAC).

To mitigate the impact of prop-washing on the habitat, EIFCA closely monitors the fisheryas impact on the habitat, designated bird species, seals and the sediment and implements measures to reduce the risk to vulnerable ecosystems, such as by implementing a code of conduct.

References

Jessop, R.W. 2017. 2017 Research report, WFO cockle stock assessment. Report produced for Eastern IFCA. Available at: http://www.eastern-ifca.gov.uk/wp-content/uploads/2016/11/2017_WFO_cockle_stock_assessment.pdf

Eastern IFCA. 2017-18 Wash Cockle Fishery Skippers Briefing Pack. Available at: http://www.eastern-ifca.gov.uk/wp-content/uploads/2017/06/2017_skippers_briefing_pack_FINAL.pdf

Eastern Inshore Fisheries and Conservation Authority (EIFCA). 2017. Wash Fishery Order (1992) Licence fees Impact Assessment (IA) 11/08/2017. IA No: EIFCA005. Available at: http://www.eastern-ifca.gov.uk/wp-content/uploads/2017/09/Impact-Assessment.pdf

Eastern IFCA. 2018. WASH COCKLE FISHERY 2017/2018 NOW OPEN. Available at: http://www.eastern-ifca.gov.uk/wash-cockle-fishery-20172018-now-open/

Worrall, J. 2017. Highs and lows in east coast cockles. Fishing News. 4th July 2017. https://fishingnews.co.uk/features/highs-and-lows-in-east-coast-cockles/

Eastern IFCA . 2017. Eastern IFCA Enforcement Policy Regulation 2 (daily catch restriction). Wash Fishery Order (1992) Cockle Fishery 2017. Available at: http://www.eastern-ifca.gov.uk/wp-content/uploads/2017/06/2017_EIFCA_Enforcement_Policy_Reg_2_Daily_Catch_Restrictions.pdf