Inland Fisheries Ireland are investigating a significant fish kill on the Ballygowan River in Claremorris.
Last Wednesday evening, Inland Fisheries officers received a report from a member of the public regarding a fish kill on the Ballygowan River, which flows into Lough Mask.
Investigations are still ongoing, but it's believed the fish kill was the result of effluent of agricultural origin.
Local reports noted fish - primarily wild brown trout- in an agitated state in the river on Tuesday evening last.
Over a thousand wild brown trout up to 4 years old have been removed dead from the river.
Inland Fisheries says the stream where the fish were found dead shows no sign of enrichment, so the polluting matter must have passed through the river and since dissipated downstream.
With water levels low and temperatures high for trout and salmon, Inland Fisheries says a small amount of polluting matter can have devastating results.
They're calling on farmers and silage contractors to be extremely careful to ensure no effluent is released near drains, streams and rivers.