The South-Western Regional Fisheries Board has reported an increase in fish kills of more than 60 per cent on 1996.
It says 11 fish kills were recorded in the region in 1997, including a serious incident at the ESB's Carrigadrohid hatchery.
In the 11 kills reported, the board said seven occurred in Co Cork with the remainder in Co Kerry.
Excluding the ESB incident, for which there was no explanation, the other fish kills included agricultural pollution, eutrophication (low water), local authority discharges and two more incidents not definitively proven.