White-clawed crayfish released in North Somerset Published duration 11 September 2012

About 80 rare white-clawed crayfish have been released into the wild in North Somerset as part of a conservation programme.

The crayfish are the largest freshwater invertebrates in the UK and the only native species.

They are under threat from North American signal crayfish which were introduced to the UK in the 1970s for the fishing and restaurant industry.

The native crayfish are pink-white on the underside of their claws.

Due to competition from the signal crayfish and the spread of a disease which is carried by them, white-clawed crayfish numbers have decreased dramatically.

They are now classified as a globally endangered species by the International Union for Conservation of Nature.

Elusive animal

The South West Crayfish Partnership was set up in 2008 in response to the decline.

image caption The native white-clawed crayfish (l) could be "out-competed" by the American signal crayfish (r)

It is a collaboration between Bristol Zoo Gardens, Avon Wildlife Trust, Bristol Science and Conservation Foundation, Bristol Water, the Environment Agency and Buglife - The Invertebrate Conservation Trust.

The crayfish being released have been reared at the zoo for a year to ensure they have a good chance of survival when introduced in to their new home.

"We have all worked so hard here at the zoo to successfully breed this endangered species and we will be thrilled to see them return to their natural habitat, thanks to the support of the Heritage Lottery Fund," said Jen Nightingale, Bristol Zoo's UK Conservation Manager.

"This is a relatively small release, however it is the beginning of a large scale approach to prevent the extinction of this species.

"Captive populations are paramount to increasing our knowledge as we still know relatively little about this elusive animal."