THE North American signal crayfish has been discovered for the first time in the River Eden system in Cumbria.

This is extremely bad news for the endangered native white-clawed crayfish, whose best stronghold in Britain is in the Eden Valley.

White-clawed crayfish are an endangered species and the River Eden is of such importance for these lobster-like creatures that it is designated as a Site of Special Scientific Interest by the UK Government and a Special Area of Conservation by the European Union to protect them.

The non-native North American signal crayfish, which is larger, out-competes and eats native crayfish, as well as carrying a fungal disease called crayfish plague.

Following a report of dead crayfish washed out of a beck in flooding, a signal crayfish population has been discovered in a small tributary of the River Eden in north Cumbria.

It appears likely that this particular population of signal crayfish has existed for many years. The two species are not currently overlapping in their distributions in the River Eden system, but if they did occur together it is likely that the signal crayfish would eradicate the native crayfish.