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The Burry Inlet and Three Rivers Estuary (Carmarthen Bay) Cockle Mortality
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Mass mortality of cockles has occurred in the Burry Inlet and Three Rivers Estuary for the last four to five years and continues this year also (2007) costing the Welsh economy in excess of £3 million a year on first sale prices. This loss could rise to as much as £17 million when post processing value added products are considered. The cockle fishery is Wales’s largest fishery, larger and worth more than the whitefish and crustacean fisheries combined. The Burry Inlet has been recognised by a Marine Stewardship Council accreditation which certified that management gives rise to a sustainable fishery in both fishery and ecological terms however current mortality is of concern.
The Burry Inlet is an internationally important site for waterfowl such as Oystercatchers and Knots which is reflected in its status a Special Protection Area (SPA) and a Ramsar site (from the Ramsar convention [sites first started to be designated in 1976]). The continued mortality of cockles is of conservation concern as they principal food resource for these bird species. Both the Burry Inlet and Three Rivers are also components of the Carmarthen Bay and Estuaries Special Area for Conservation (SAC).
The cockle mortalities over the last 3 years have shown a similar pattern. There is very high recruitment of juveniles with good winter survival, growth and spawning in the spring before near total mortality in the summer months (Dr Andy Woolmer SWSFC pers. comm.). Previous studies have linked cockle mortality to severe winters (Strasser et al., 2001), summers (Lauchner, 1983) and other environmental stressors such as temperature and parasites (Thieltges, 2006). Currently the cause of the mortality in the Burry Inlet and neighbouring Three Rivers Estuary is unknown and not thought to be due solely to parasites.
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Experience at Bangor University (BU) (Dr. Shelagh Malham) and Swansea University (Dr. Emma Wootton and Dr. Ruth Callaway) in shellfish mortality and immunology has demonstrated that unexplained causes of mortality are often a result of a number of environmental and biological factors acting in combination to cause mortality. A holistic understanding of the problem can lead to better management of the fishery with real time knowledge of the state of both the environment and the biology of the cockle. Considerable research on cockle biology (such as growth, (Brown et al., 1976; Seed and Brown, 1978) reproductive cycles, (Seed and Brown, 1975; Seed and Brown, 1977) has also been undertaken by the researchers at Bangor and Swansea Universities who are involved in this project, along with a local marine consultant (Dr Andy Woolmer) who has expertise in this area.
Without the financial and informational support of CCW, Seafish (Sea Fish Industry Authority) and collaborations between Bangor and Swansea University this project would not have been able to go ahead. Many agencies have expressed an interest and are actively helping to supply data and time to the project, including the Environment Agency, Dwr Cymru, South Wales Sea Fisheries Committee and the County Councils etc. The project is being driven by South & West Wales Fishing Communities Ltd as the association also represents the interests of its cockle gatherer members.
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It is anticipated that the current project will end in March 2008 and will recommend key areas for further investigation. The research group are currently searching for sources of funding to enable a larger project that will secure the future of the fishery.
To this end Bangor and Swansea Universities will be applying to Seafish for bursaries to support 2 PhD students which it is hoped will start as soon as possible. Further funding however will be necessary to support the PhDs and also further studies.
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