Inland Fisheries Ireland (IFI) says it has confirmed a significant fish kill on the Royal Canal in Kilcock, Co Kildare earlier this week.
A report was received on Monday 1 July from Waterways Ireland of the fish kill, which has claimed some 300 fish of various species including roach, rudd, bream and pike.
The investigation, which commenced immediately and remains ongoing, has identified agricultural discharge to a River Ryewater feeder that enters the canal at Kilcock.
IFI says work is now ongoing to ensure that there is no further polluting discharge to the system from this location.
It has also has issued a fresh appeal to farmers to remain vigilant in avoiding water pollution during the summer months when harvesting silage and spreading slurry.
Silage effluent is a significant pollutant and if allowed to enter a waterway can potentially lead to fish death and habitat degradation.
IFI has a confidential hotline number at 1890 34 74 24 or 1890 FISH 24 for the public to report incidents of water pollution, fish kills and illegal fishing. For more visit fisheriesireland.ie.