Inland Fisheries Ireland (IFI) has said it could not find out who was responsible for a pollution incident on the River Blackwater in Co Cork earlier this year, because it is required to catch perpetrators in the act of polluting.
The incident, which left some 32,000 fish dead, was described as one of the biggest in the State's history.
IFI is appearing before the Public Accounts Committee over historical issues around governance.
People Before Profit-Solidarity TD Paul Murphy asked if it was the case that no source of pollution was found in the River Blackwater, and whether a repeat could be avoided.
"Nothing has been done to prevent something like that happening again, is that a fair summary of where we're at?"
Deputy CEO Barry Fox said it is something that IFI is engaging with local stakeholders on, and they will assess the catchment next year.
"We are successful in about 70% of our detections," he said.
"If it's not being discharged when our officers attend onsite, under our legislation, we can't bring forward a prosecution."
Asked why the source of the pollution was not detected by IFI investigators, Mr Fox said they suspected that a "plume" may have been discharged into the body of water "about 72 hours before the first detection of dead fish".
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