THE stronghold of native crayfish in the North-East could be under threat from the spread of the aggressive signal crayfish, Environment Agency officers have warned.

Angling clubs, conservation groups and other organisations have all been advised that North American signal crayfish have been discovered in the River Derwent, near Blaydon, Tyneside.

As a result, measures have been put in place to try to halt their spread to strongholds of the native species in the rivers Wansbeck and Aln.

Last month, agency officers were informed by staff at Gateshead's Thornley Woods Centre that they had found two signal crayfish - one alive and one dead.

Further surveys revealed another female signal crayfish at Thornley Woods. This was removed by agency staff.

Agency conservation officer Anne Lewis said: "At the moment, the signal crayfish seem to be present in the Derwent in low numbers but it is essential that we take every step to prevent their spread.

"The American species of crayfish is bigger, more aggressive and out-competes our native crayfish. Most importantly, it also carries a fungal disease known as crayfish plague that has wiped out our native crayfish from most rivers in the South."

Efforts to stop the spread of the signal crayfish into rivers that are home to the smaller, native white-clawed crayfish, include ensuring angling equipment is thoroughly dry when moving between rivers, a halt to the transfer of fish from the Derwent to catchments that are home to native crayfish, and spreading information about the problem.

If anyone discovers signal crayfish, they are asked to call the agency using a free emergency number - 0800 80 70 60.