| 13/05/02 |
Burry Inlet Cockles - Shellfish toxins
- News from the South Wales Sea Fisheries
Committee The temporary
Prohibition Order closing the cockle fishery on public health grounds continues to run on
from July 2001. Food Standards Agency (FSA) and CEFAS continue to investigate the
cause, but it is clear that it is not typical diarrhetic shellfish poisoning (DSP) and
which is normally caused by the presence of a species of dinoflagellate in the plankton.
The cause of this outbreak is of a particular concern because it is very potent and
unusually persistent. Cockle fisheries in the Thames and Wash estuaries are also now
closed on similar grounds. FSA are in liaison with experts in other countries, in
particular Eire and USA and who have experienced similar problems in the past.
Cockle fishermen remain out of work, although facility for
hardship payments have recently been agreed by the Welsh Assembly Government. In the
meanwhile the cockles that would normally have been removed by fishing remain in the
sands. This is causing further concerns and is the subject of proposals for further
research from a joint working group of various interests: Local authorities, SWSFC,
Swansea University, Environment Agency, CCW, NAW and industry, and an application
being progressed under Objective 1 funding.
The cockles have shown slow growth and poor meat condition
over the previous four years coincident with improvements made to sewage discharges to the
estuary. At the same time cockle stocks have been relatively high and the winters
mild. The study is intended to review nutrient levels in the estuary and relate this
to cockle growth, and consider whether stresses have made the cockles more susceptible to
algae toxicity. Depending on the cause of the outbreak it may also be able to relate
nutrient levels to the presence of certain causative organisms and which seems likely to
be a benthic alga. Finally, there are real concerns that the cockles, if left
unharvested, will die off (either prematurely or due to natural causes) creating more
shell, and that this will form the basis for mussel settlement. Experience in recent
years has shown that mussels have been widely available in the water column (perhaps due
to mild winters) and once settled on cockle shell have been difficult to remove.
Persistent mussel has the capacity to build up mud and assist the infilling of the
estuary thus changing its character and reducing the area available to cockles. This
could have further ecological implications, and the study will consider these aspects and
offer advice to fisheries managers as to the need for and scope of corrective action.
The paradox is that the clean up of the estuary associated
within Urban Waste Waters, Shellfish Waters and Bathing Waters directives may result in
changes to the estuary and contrary to the intent of the Habitats Directive and Birds
Directive under which the estuary is also designated.
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