Blackwater mass fish kill confirmed as due to pollution incident

Marine Institute experts are not yet able to identify chemical involved in Co Cork incident or where it came from

Member of Mallow Trout Anglers with dozens of dead brown trout recovered from the Blackwater in Mallow, Co Cork. Photograph: Mallow Trout Anglers
Member of Mallow Trout Anglers with dozens of dead brown trout recovered from the Blackwater in Mallow, Co Cork. Photograph: Mallow Trout Anglers

Inland Fisheries Ireland (IFI) has confirmed that the deaths of thousands of brown trout on Cork’s river Blackwater were caused by a pollution incident.

However, it has not yet been able to identify the source of the problem.

IFI acting chief executive Suzanne Campion said it had received the preliminary results of tests by Marine Institute staff on some of the dead fish taken from the Co Cork river that suggested they had died as a result of some environmental contamination.

Ms Campion said the examination of the fish tissue found that their “gill pathology was consistent with and suggests possible exposure to some form of environmental insult/irritant, is widespread, and largely chronic pathology is functionally significant”.

IFI senior fisheries environmental officer Andrew Gillespie said Marine Institute fish health unit experts were not yet in a position to identify what chemical was involved and where it came from.

Ms Campion said Marine Institute scientists found no evidence of any significant bacterial infection among the dead fish that they had tested while they also found no evidence of disease in any of their organs.

But she stressed the IFI investigation is continuing and virology results will be available on August 29th.

She promised to keep anglers and all interested parties briefed on whatever the investigation uncovers.

In its first statement last week on the fish kill, the IFI said it was a possible fungal infection that had led to the deaths, saying that high water temperatures and low water levels could make brown trout vulnerable to such infections.

The IFI also said last week it was estimated that between 8,000 and 10,000 fish were killed.

Mr Gillespie would not be drawn on whether the IFI had updated this figure, or on claims by angling groups that up to 46,000 had died.

Asked if the Marine Institute had examined dead fish from various points along the 40km of affected river way, Mr Gillespie said institute scientists had tested fish from just upstream of Mallow where the heaviest concentration of mortalities appeared to have occurred.

Ms Campion and Mr Gillespie were speaking at an information meeting chaired by the Minister of State at the Department of Agriculture, Food, Fisheries and the Marine, Timmy Dooley, that was attended by about 60 people including angling club members and other interested parties along the Blackwater.

IFI South Western Regional Fisheries director Sean Long said experts estimated the irritant could take 24 to 72 hours to kill the fish, which – given that dead fish were first spotted on August 9th – suggested the incident could have happened as early as August 6th.

He said dead fish were now being found over a 40km stretch of the Blackwater from Ballymaquirke downstream to Mallow town and beyond to Killavullen, but he noted that some found at the downstream extremity could have died farther upstream and been washed down.

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Barry Roche

Barry Roche

Barry Roche is Southern Correspondent of The Irish Times