A SURVEY carried out on a stretch of the River Wansbeck that flows through the National Trust's Wallington Estate has revealed the area as one of the top sites in England for the endangered White-clawed crayfish.
It is one of Britain's most endangered native animals.
Numbers have declined dramatically as a result of the impact of the American signal crayfish, which are larger, more aggressive and carry the crayfish plague, a disease fatal to White-clawed crayfish.
The pollution of rivers and degradation of river habitats by inappropriate land management practices have also played a substantial part in their decline.
The survey was carried out by National Trust Warden John Jamieson.
Mr Jamieson said: "Results have confirmed that the River Wansbeck is an internationally important stronghold for the White-clawed crayfish.
"We now have the data to help focus our work on how we can further strengthen their habitats."