White-clawed crayfish are the only species native to the UK

Magistrates in Kendal were told that the dead fish were found in the River Mint, at Patton Bridge, last June.

Investigations found that the water contained sheep dip from a nearby farm.

Alan Hodgson, from Patton Bridge, pleaded guilty to causing polluting matter to enter a controlled water and was fined �1,500, plus �1,409 in costs.

The Environment Agency established that although he had checked his dipping tubs for leaks, the sheep had not been given an adequate draining off period after being dipped.

'Disastrous effect'

Mr Hodgson said he would now change his dipping practices and apologised if he had inadvertently caused the crayfish to die.

White-clawed crayfish is the only crayfish species that is native to the UK.

Nationally, disease and competition from other, non-native crayfish species has had a serious effect on white-clawed crayfish numbers, making the Cumbrian populations particularly important.

Last winter, the Environment Agency transferred some crayfish from other locations to the River Mint to encourage the population to recover.

Environment Agency officer, Jon Mellor, said: "Most farmers use sheep dip responsibly, but even the tiniest amount can have a disastrous effect on crayfish and similar creatures if the dip gets into rivers and streams.