The presence of algae along stretches of the Owenriff River in Connemara has renewed fears about the impact pollution was having on the endangered pearl mussel.

These photographs taken last week at various points along the river that runs through Oughterard and drains into Lough Corrib highlight the extent of the problem.

Small farmer and environmental campaigner John Gibbons said the Owenriff Special Area of Conservation (SAC) was regarded as the second most important river in Europe for pearl mussel but its water quality was deteriorating due to over-farming, and agricultural nutrients run-off.

“We’re looking at the annihilation of the pearl mussel, a highly protected species under European law, on the Owenriff,” said Mr Gibbons, Secretary of the Corrib, Mask and Carra Water Protection Group.

“This is the death-knell of the Owenriff and the trout hatchery, and where goes the Corrib after that?”

Mr Gibbons said he has been campaigning about water quality at the Owenriff and Corrib in County Galway for almost four decades. And he has been involved in three successful court cases in Europe to protect the pearl mussel.

The Glengowla resident said intensification of agriculture in Connemara was causing even greater problems to the water catchments than other threats such as invasive pike species.

He said the primary threat was now “nutrient run-off from farming”.

“Once it gets into the river the algae grows and it cuts off all the oxygen, and when it dies then it gives off bacteria, and kills all the juvenile pearl mussel, an endangered species,” he said.

“The pearl mussel is a canary in the mine with regards water. They’re a water filterer. When the pearl mussel dies in the water, everything else is gone – your salmon, your trout, your water quality, everything,” he added.

Mr Gibbons insisted he was not bashing farmers, and as a small farmer himself, he was certainly not anti-farmers. But he said a minority of farmers were causing untold damage.

“It’s not about taking on farming or killing farming. Everyone has to have a livelihood, and everyone who has farming land in the area must farm it, but they must farm it in line with the regulations,” he said.

Mr Gibbons, a former trout hatchery manager, confirmed a complaint has been lodged with the EU Court of Justice but he feared that the pearl mussel could be wiped out before the problem is dealt with.