Up to 100,000 fish have been killed as a result of last week's landslide at Derrybrien, Co Galway, according to the Shannon Regional Fisheries Board.
Tests carried out by board staff over the weekend found "huge" numbers of dead fish in the silt washed into the Owendalulleegh River, according to the chief executive, Mr Éamon Cusack.
Based on these tests, the board now believes that virtually all fish in the 10-mile stretch of the river down to Lough Cutra have been killed. Mr Cusack estimated the number of dead, farmed and wild fish at between 50,000 and 100,000.
Work on barriers to contain the landslide continued on a 24-hour basis over the weekend, and no further slippage was reported. Contaminated water is still flowing into the river but the larger chunks of earth are being held back, according to Mr Martin Collins of the Derrybrien Landslide Action Group.
Mr Collins said local people were still shocked and annoyed over what happened. Although it looked like "the worst is over - for now at least", there were concerns about further slippages.
Locals believe the landslide was caused by the construction work being done on a €60 million wind farm in the Slieve Aughty mountains at Derrybrien. However, the developers, Hibernian Wind Power, an ESB subsidiary, say it is too early to establish the cause.
An ESB spokesman said "good progress" was made on stabilising works over the weekend, assisted by fair weather. A five-metre dam had been installed at the worst-affected point, and this was now being reinforced. He said "no slippage" had occurred over the weekend.
The spokesman said that if it was proven that the landslide resulted from work on the windfarm, the ESB would "take responsibility" and take "appropriate measures". This could take the form of compensation for families affected by the disaster.
With assistance from the Air Corps, fisheries inspectors also carried out aerial surveys of the damage caused by the landslide at the weekend. However, Mr Cusack said there was very little that could be done now to save fish life. A major concern would be to ensure no more silt flows into the river.
He said the board would also investigate who was responsible and could decide to prosecute. Under current legislation, fines of €2,000 and/or a jail term of six months can be imposed in such pollution cases. Courts can also award damages against polluters, of up to €10,000 in District Court cases and more in the higher courts, in serious cases.
The Owendalulleegh River holds good stocks of wild brown trout and is a spawning river for the lake. The landslide happened as the trout were beginning to move from the lake up to the river to spawn. A preliminary report on the disaster is expected from the ESB within a week.
