Expert says Cork fish kill caused ‘agonising deaths’ as toxic spill suspected on River Blackwater

Nearly 50,000 salmon and trout have died in Cork’s River Blackwater fish kill, with a toxic chemical spill suspected

Species most affected include brown trout and Atlantic salmon, of all life stages, from fry to adult.

Many of the thousands of fish killed on a Cork river and its tributaries died in agony by having their flesh eaten away by severe necrosis.

That is according to an expert who examined them and carried out tests after what has been described as the biggest fish kill in the history of the State.

Angling clubs along the River Blackwater have claimed that nearly 50,000 fish have died following the incident which was first reported on August 9.

Scientist Sue Mitchell, an expert who is accredited by the European Council of Aquatic Animal Health, compiled a stark report for angling clubs.

It showed in her opinion it was almost certain to have been a man-made incident, likely to be due to some toxic chemical spill.

She said she visited three sites and found a "significant population of dead and dying fish in the river and nearby tributaries". 

Species most affected include brown trout and Atlantic salmon, of all life stages, from fry to adult.

Ms Mitchell said many fish were lethargic and swimming abnormally.

She said many fish showed severe damage to their eyes which were bleeding and in some cases their eyeballs had burst open. 

She added that the gills, used for breathing, were eaten away by severe necrosis.

Ms Mitchell carried out autopsies on some of the fish which showed that none of them had been recently feeding. 

If fish cannot see, they find it almost impossible to catch prey.

Autopsies on some of the fish showed that none of them had been recently feeding. 

She said she could find no evidence of parasites, bacteria or fungal infection being responsible for the kills.

The scientist added that while some of her results are still pending, agricultural run-off (which would include pesticides, herbicides, slurry etc) could be one cause as could a spill of industrial effluent such as chemicals or heavy metals.

She also did not rule out a chemical spill involving fuel or solvents.

The expert added that many of these substances, particularly if concentrated or released in excessive quantities, are capable of causing the kill.

“While low water levels and higher than usual temperatures may have been suggested as a contributing factor, the severity of the gill and eye damage is not consistent with this,” Ms Mitchell said.

Minister of State for nature, heritage and biodiversity Christopher O’Sullivan expressed concern about the impact the incident could have on the special area of conservation.

Rumours have been circulating that other creatures have also died from eating the fish.

However, Mr O’Sullivan said there have been no confirmed reports of deaths of otters, kingfishers or cormorants.

“Any incidences involving mammals should be reported immediately to National Parks & Wildlife Service or Inland Fisheries Ireland,” he said.

The main river has been severely impacted, along with the Clyda river in Drommahane, the Awbeg which flows through Castletownroche, and a number of smaller streams in the region, including the Ross in Killavullen.

The kill has decimated the salmon population in the Blackwater as mature and young have been wiped out, meaning it could take a years before their numbers recover on what was regarded as one of the best salmon fisheries in the country.