Inland Fisheries Ireland is investigating what it is describing as a major fish kill on a tributary of one of the country's most important salmon rivers.
The fish kill occurred on the Owentaraglin River, a tributary of the Blackwater near the village of Kiskeam, in north Cork.
More than 1,200 dead fish have been recovered by fisheries officers along a 2km stretch of the river.
Species included salmon, brown trout, eel and stickleback.
Inland Fisheries Ireland has said it believes the fish kill was caused by a large discharge of slurry into the river and says significant damage has been done to spawning beds.
The source of the pollution is believed to have been identified.
IFI Director in the South West Sean Long said it will take years for the Owentaraglin to recover.
Mr Long warned farmers about the dangers involved in storing and moving slurry.
Inland Fisheries Ireland is the body charged with protection and conservation of fish stocks in rivers and lakes.
