Marine Institute

Oyster Mortalities in 10 Irish Bays

July 15, 2009

Oyster growers in 10 bays around the country have been experiencing  losses of between 15 and 75 per cent of their stock since June 22nd.  Initial reports came from three bays in the south-west, south east and north-east where oysters were imported from France earlier this year.  Reports have now been received from a further seven bays where seed or partially grown oysters were imported from France, as well as England and Guernsey. Oysters that were in deeper water and growing more quickly appear to have been more severely impacted.  

Four samples from three bays have tested positive for herpes virus OsHV1. Analysis is ongoing on samples received to date and more samples are expected to arrive at the Marine Institute this week. The presence of disease listed in Council Directive 2006/88/EC has so far been ruled out.

All movements of oysters for on-growing either within Ireland, or for export or import must be notified to the Marine Institute and will be reviewed on a case by case basis. Movements will be restricted from areas experiencing oyster losses. 

Some oyster growing areas in France, where mortalities began in April, continue to experience oyster mortalities. The mortalities began in the south of France and spread northwards affecting the majority of French growing areas. In areas south of the Loire, oyster mortalities are coming to an end and trade restrictions are beginning to be lifted.

The herpes virus, which is considered to be endemic in parts of Europe, is not controlled under fish health legislation. Therefore when importing seed or partially grown oysters, it is the responsibility of the producer to ensure that their stock is free of the herpes virus.

The Marine Institute strongly recommends that the growers exercise caution when importing stock from areas which have experienced heavy losses of oysters.   

For notification of abnormal oyster mortalities or movements of oysters for on-growing email notification [at] marine [dot] ie  or fax 091 387 201 or call 091 387 200.

The herpes virus OsHV1 has no known impact on human health.

For more information on fish health regulations or updates visit www.marine.ie/fishhealth