The scientific team, led by Dr Stefano Mariani who began the work while based at University College Dublin, believe that the Pacific oysters are now an established species in the wild, a fact that has important ramifications for local conservation groups and industry.
The findings, which are published in the Journal of Heredity, are the result of a one year study that involved genetic testing of specimens collected in the area of Lough Foyle which lies between County Londonderry and County Donegal
The level of genetic variation between the populations which live in the Lough, and those contained in man-made farms suggested to the team that the specimens collected from the wild were a different group to those in the nearby farms. Once they were able to rule out introduction by prevailing currents and passing ships, they concluded that the ‘feral’ oysters were now a self-sustaining group.
Pacific oysters are originally from the Far East and are native to countries such as Japan and Korea. However they were spread to Europe in 1966 and North America from 1920 in order to replenish stocks depleted by overfishing or to establish farms in areas previously without native oysters. Since then they have become invasive in many places, causing significant changes to local ecosystems.
To date, management at Lough Foyle has focused on keeping oysters contained within the farms. Judith Kochmann, the student who completed the work, believes that additional measures are now needed to control the populations now established in the wild, whose presence may harm the native populations of European oysters as well as altering biodiversity and ecosystem functioning.
Dr Mariani, from the School of Environment & Life Sciences said: “Once an exotic species is settled in a new environment, it can spread independently of the original cause of its arrival.
“Now the Pacific oyster is with us, the far-reaching consequences of its establishment are still debatable, but just controlling aquaculture is no longer an effective means to reduce its further spread.
“We may enjoy our oysters with Guinness or champagne, but we should now think more deeply about our insatiable need for more and more easy-to-access commodities.”
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