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Marine Science



Oyster sanctuary to be created in the Thames. The first Mother Oyster Sanctuary is set to be created in the Thames estuary in a bid to increase the oyster population which have been hit by pollution, disease and loss of natural habitat, reports the London Evening Standard.

Working in the only Marine Conservation Zone in England for native oysters, the Zoological Society of London (ZSL) – chaired ENORI, which is a coalition of oystermen, local communities, NGOs, universities and UK Government, have begun creating the habitat required for the Mother Oyster Sanctuary, replenishing the Thames estuary’s lost oysters, says the newspaper.

Over the last 200 years the oyster population has decreased by 95% due to historic overfishing and the oysters’ recovery has also been hindered by habitat loss, pollution and the introduction of diseases. Conservationists have concluded that microplastics do pose a risk to the health of shellfish and fish, though some species such as mussels are better at expelling microplastics and oysters are more sensitive to microplastics than mussels. The main risk pollutant on the Thames was previously TBT (Tributyltin), an anti-fouling paint used on boats which is now banned but as oysters are filter feeders, any chemical spill disrupts them.

As part of the project, ‘recycled’ shells from oysters bred in Mersea and sold in Borough Market and West Mersea as well as cockleshells from the Thames cockle fleet have been used to “lay the cultch” which means there is a hard surface for the oysters to grown on.

Once the “cultch laying” is completed, adult females or ‘mother oysters’ are laid, which when conditions are right, will spawn in the coming weeks; initiating the first stages of the native oyster’s life cycle.

Oyster farming has been recorded in Mersea since the Roman times, although populations of the European native, or Colchester oyster have suffered dramatic declines.

Oysters are known as ‘ecosystem engineers’ and one adult oyster, for example, can filter more than 140 litres of water in a single day.

Rachel Langley, living seas co-ordinator at Essex Wildlife Trust, said: “We are delighted that this exciting project is evolving into its next phase and we have no doubt that the outcome of ENORI’s pioneering restoration work will be extremely positive for the Native oyster population and subsequently the marine ecosystem in Essex.”

ENORI is a joint venture between ZSL, Essex Wildlife Trust, Blackwater Oysterman’s Association, Blue Marine Foundation, The University of Essex, The Nature Conservancy, River Roach Oyster Company, Colchester Oyster Fishery, CEFAS, Natural England, the Environment Agency, and the Kent and Essex Inshore Fisheries Authority (KEIFCA).

To find out more about ZSL’s Thames conservation projects and the Mother Thames campaign, visit www.zsl.org/MotherThames