About 2,000 brown trout were killed when a large quantity of domestic heating oil flowed into the Killough river, Enniskerry, Co Wicklow, a tributary of the Dargle.
Ms Greta Hannigan, environmental officer with the Eastern Regional Fisheries Board, said the kill took place on Wednesday when the pipe to a diesel tank was severed on a resident's property at Waterfall Road. "It was done during the night. The oil spilled out along the ground, into a surface water drain and ended up in the stream."
Fisheries Board staff mounted a rescue operation on the evening of the pollution and managed to remove 200 fish. "That was the best we could do. As well as the 2,000 trout, almost everything else in the river was destroyed: it was a complete wipe-out," said Ms Hannigan.
It is estimated that it will take five or six years to restock the river.