An investigation is under way into a major fish kill at the popular angling resort of Lough Gara on the Roscommon/Sligo border. Up to 5,000 adult bream, roach and pike have died in the area, most in the south-west corner of the lake and in a five-mile stretch of the River Lung, north of Ballaghaderreen.
The Shannon Regional Fisheries Board has taken live fish samples as part of its investigation and expects to have initial results early next week.
Mr Matt Nolan, an inspector with the board, said it was unable to say at this stage what was responsible for the kill. "We have no idea. We don't know if it's a virus or water-related, or if it has something to do with water temperature."
While he could not rule out the possibility that farming effluent was responsible, he stressed that "intensive farming would not be a feature of the area".
Sightings of dead fish were first reported about a week ago by local fishermen at the 5,000-acre lake, which attracts anglers from around Ireland and Europe during the summer.
Mr Nolan said: "There is a worry about what this could do for the reputation of the lake and its impact on tourism, but still we felt it was important to let people know what has happened."
He said the dead fish were concentrated in the waters where the lake meets the River Lung from Ballaghaderreen, a town with some industry and a population of about 1,500. "We have found no dead fish upstream of the town. The whole ecosystem is very healthy there."
He added: "The board is putting all the resources at its disposal into the investigation and will continue to do so until we find a cause."
The fish kill is the third in the Shannon region this summer. It follows the death last month of 300 trout on the River Deel in west Limerick and 1,500 trout, salmon and eel on the Suir and its tributary, the Clonmore, near Thurles.
It comes three weeks after the Central Fisheries Board appealed to farmers to be extra-vigilant and to avoid water pollution as the silage-making season began.
The Lung was the scene of similar fish kills in June 1994 and July 1995, when a combined total of 15,000 coarse fish were found dead in the waters where the river runs into Lough Gara.
The Green Party spokeswoman on the environment, Ms Mary White, said fines against offenders should be increased to prevent further fish kills.
