It's reported the algal bloom identified off the west coast is continuing to kill fish and shellfish in significant concentrations from north Galway to north Donegal.
Up to 80 per cent of stock has been affected on some oyster farms in Donegal, and it is also having a negative impact on sea angling tourism, the Marine Institute has confirmed.
Samples of this new bloom, first detected in May, are being collected for Marine Institute monitoring by the Irish Coast Guard search and rescue helicopters.
Marine Institute spokesperson Joe Silke says the bloom not associated with pollution but contained a “toxic irritant” that damaged gills of shellfish, fish and invertebrates.
Earlier this month the bloom resulting in dead marine life washing up on Rossnowlagh and Murvagh beaches.
Irish Farmers’ Association fish farm section chief executive Richie Flynn said if there was a “properly functioning” licensing system in place, farmers could take measures to move stock when such blooms occurred.