Anglers in Cork have expressed fears that they may be facing a complete wipeout of brown trout on the Blackwater after thousands of fish have mysteriously died in the river over the past three days.
Mallow Trout Anglers chairman John Ruby said the discovery of “thousands upon thousands of dead fish” in a near 30km stretch of water from Banteer bridge to Killavullen bridge was particularly worrying as trout are continuing to die all along the river.
“It’s having a huge impact on trout stocks whatever is the cause,” he said.
Sean Long, director for South Western Inland Fisheries Ireland, told RTÉ News that the precise cause of the fish kill had yet to be established but it appeared that many of the dead fish had a fungal infection. It wasn’t clear if the infection was the primary cause of their deaths.
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He cited low oxygen levels from nutrients draining into the water, low water levels and rising temperatures as potential stressors for the fish.
“Unfortunately, it’s a lethal cocktail for these guys,” he said.
Mr Ruby said that many of Mallow Trout Anglers’ 80 or so members are pulling dead fish from the river including over 400 from a short stretch upstream of Mallow, while they are also noticing trout are trying to get into tributaries of the Blackwater to escape whatever is killing them.
He said that while it is primarily brown trout that seem to be affected with the fish, anglers have started to find a small number of dead salmon while they have also noticed salmon behaving very oddly swimming around in pools as if very distressed.
“The trout are nearly all showing the same signs – a ghostly white colour, even though we are finding a few dead ones that have kept their buttery brown and gold colouring. But it’s their eyes, their eyes are exploding in their heads, and their tails are getting affected by it too.”
Mr Ruby said anglers wanted to know if they should continue removing dead fish from the Blackwater to try to maintain the quality of the water and if they do, how are they dispose of the dead fish, many of which have lost their scales.
And he expressed some scepticism about water temperature being a primary cause of the problem pointing out that two weeks ago the temperature in the Blackwater was warmer than the 17 to 19 degrees currently being recorded in the river.
“This is different to sewerage where you could see it and smell it and follow it and trace it back to a source, but we haven’t seen any sign or smell of anything on the water, which is strange – there is no obvious source, but it could be something toxic that is colourless and odourless,” he added.
