CUMBRIAN farmers have been urged to take extra care while dipping their sheep as part of a campaign to protect the white-clawed crayfish.

The freshwater crustaceans are the UK's only native crayfish and are particularly vulnerable to pollution.

Thousands were killed in June when a pollutant believed to be sheep dip spread through a 10 kilometre stretch of the River Mint at Patton Bridge near Kendal.

To protect the crayfish - whose numbers have already been hard-hit by crayfish plague' and competition from non-native species - the Environment Agency has issued pollution prevention advice to more than 2,500 farms close to the River Kent, and parts of the River Leven and River Eden where crayfish are known to thrive.

Jonathan Shatwell, the Environment Agency's Environment Manager for Cumbria, said: "A very small quantity of sheep dip can kill thousands of crayfish and effect a whole length of beck.

"We have seen this happen on a number of streams in Cumbria this year. Also, during times of the year when river levels are low, it is even more important to make sure that jobs are done in a way that minimises the risk of pollutants going into the becks."

Letters dispatched to farmers ask them to follow a raft of pollution-prevention measures including: l Making sure dipping facilities are well away from becks and drains and that they do not leak or spill over into them; l Making sure dipped sheep dry off in a contained area that does not drain directly to a sink-hole or beck - dip is not fully fixed to the fleece for some hours after dipping; l Disposing of used dip in the way authorised or using a pour-on preparation or a company that does showering; l Making sure slurry is spread away from the banks of streams and becks so it does not get into the water; l Spreading slurry when it is reasonably dry to avoid slurry run off, not when it is raining hard or when the ground is sodden; l Making sure silage stores are strong enough for the job and won't leak into drains and becks.

The campaign is part of a national Environment Agency initiative to encourage farmers to take care when dipping, showering or jetting sheep. Failure to do so could mean farmers jeopardise their Single Farm payment from 2005.

"Pollution from sheep dip is a national problem but in Cumbria prevention is especially vital because of the risk to the white-clawed crayfish," said Mr Shatwell. "This area is the only one in the country where the native species is not yet under direct threat from the foreign signal crayfish, so we must all take whatever action we can to assist its future survival."