White-clawed crayfish are a protected species in the UK

An outbreak of crayfish plague is believed to be threatening the already endangered creatures.

Dead native white-clawed crayfish have been found recently along the Sherston Avon and Luckington Brook.

The creatures have fallen victim to their larger cousin, the American Signal Crayfish which has been introduced into Britain.

'Native crayfish'

Martin Frayling of the Environment Agency said: "This is very bad news indeed for one of our rare native species.

"The plague is likely to kill all the native crayfish in that stretch of river, probably many thousands of animals.

"We have no idea how the disease got there but we are advising all our staff who carry out work in rivers to take precautions to prevent accidentally spreading it."

A similar plague on the Sherston Avon in the early 1980s wiped out a large number of native crayfish and resulted in a major re-stocking programme.