Farmer Anthony Edwards, 63, from Maerdy, had denied polluting the River Ceirw and allowing matter poisonous or injurious to fish to enter the river in April 2002.

Llandudno Magistrates Court heard that the Environment Agency officer who investigated the pollution found five barrels containing detergent in a shed on the nearby Maerdy Farm.

Edwards was fined £3,000 with £2,000 costs.

The court was told one barrel had rusted and the contents had leaked. Tests on samples from the barrel found the contents were very similar to the pollutant found in the dead fish.

At the time the shed was rented out to Edwards by the owner of Maerdy Farm, Arthur Evans, in exchange for straw.

In court on Friday, Edwards denied that he was responsible for putting the barrels in the shed and said that he hardly noticed them.