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Blow to fishermen after outbreak of killer disease in Lough Foyle oyster bed

An outbreak of an incurable disease that affects oysters has been discovered in Northern Ireland.

Oyster fishermen have been ordered to stop harvesting in one particular bed in Lough Foyle in Co Londonderry after an outbreak of bonamia ostreae, a condition that has wiped out native oysters in parts of Europe and in other parts of Ireland.

This means the Foyle is now the most significant habitat for oysters across Europe, making the protection of the shellfish that remain critical and of the highest importance.

Barry Fox, director of aquaculture and shellfish with the Loughs Agency, said saving the oysters was his main priority. He said the disease was a bit of a mystery.

"This is a blood parasite that can lie dormant in young oysters and attacks them when they get stressed, but there is very little known about it and no cure.

"It was first detected in Lough Foyle in 2005, but unfortunately the strict controls that now exist governing the harvesting of oysters only came into effect in 2008 and the numbers of oysters in the Foyle are not what they could have been.

"When oysters are harvested from the bed, the ones that are too small are thrown back, but this causes stress to the oyster, which is when bonamia can take hold, and it has been known to completely wipe out the supply of oysters.

In fact, this has happened in a number of places across Europe and in Westport in Co Mayo and Lough Swilly in Donegal.

"We conducted a significant survey before Christmas and found that in this sizeable bed in the middle of the Foyle, 80% of the oysters are undersize and 70% of the stock in the bed are infected with bonamia ostreae, which is why we stopped harvesting of this particular oyster bed.

"We know the oysters are stressed because they remain open when they are brought up from the bed. Normally the shell would remain closed."

The oyster fishing season runs from September to March, when licensed fishermen can harvest them from Monday through to Friday, from 6am to 6pm.

During any season, oyster harvesting is worth approximately £500,000 to the local economy.

Belfast Telegraph