Endangered White-clawed crayfish thriving in Northumberland.

A survey carried out on a stretch of the River Wansbeck that flows through the National Trust’s Wallington Estate in Northumberland has revealed this area as one of the top sites in England for the endangered White-clawed crayfish. The White-clawed crayfish 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 that is 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 work was carried out by National Trust Warden John Jamieson over a two week period. Data and information gathered has been used to help evaluate the abundance of the White-clawed crayfish, any threats to the population from the American signal crayfish and the quality of the habitat.

Both of the burns surveyed had a high or very high abundance of crayfish and the results revealed that there was a chance of finding a crayfish under two out of every three of the stones that they use as refuges. In total eight sample sites were monitored during the two week survey and 250 White-clawed crayfish were found in 400 refuges. The lack of crayfish on nearby burns has been linked to land use, such as cattle grazing, close to the river.

John Jamieson, National Trust Warden at the Wallington Estate, says, ‘Results from this survey 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 and make sure that the crayfish can flourish.’ Last Stand for Peak District Crayfish?
By Paul Mortimer, National Trust Countryside Manager, South Peak Estate

The native or white-clawed crayfish, Austropotamobius pallipes, was once widespread in the UK but is now in steady decline and due for extinction within the next 30 years if nothing is done and the present decline continues. The main reason for this decline is crayfish plague, a disease caused by the fungus Aphanomyces astaci, which is carried by some North American crayfish, including the signal crayfish Pacifastacus leniusculus, introduced into the UK for aquaculture in the late 1970’s.

The main stronghold for the native crayfish in the Peak District was the River Dove, part of the South Peak Estate. In July 2005 we witnessed the impact of crayfish plague as the entire population was wiped out in less than two weeks. Hundreds of these normally reclusive creatures could be seen dead on the bottom of the river. How the disease entered the river remains a mystery – to date no signal crayfish have been recorded, but as the spores remain viable in water for some time, the opportunities it has (via spread on wet dogs, birds, fish, wet fishing tackle etc.) are numerous.

Only one natural population of native crayfish now remains in the Peak District, partly on National Trust land in the River Manifold. This river is well used and fished like the Dove, and is very vulnerable to an outbreak of crayfish plague.

Control of the spread of signal crayfish and of the plague is ineffective at the present time and, until this is better understood, there is a move to safeguard white-clawed crayfish populations through reintroduction projects or the creation of ark sites where a number of a white-clawed crayfish population are translocated to safe havens away from signal crayfish, thereby reducing the risk of plague.

Such as site has been identified on the South Peak Estate, and we are working with a crayfish consultant to set up an ark population. A number of individuals have already been removed from the main population and are being held in an isolated location where they will be established as a breeding population. Next summer the ark site will be developed, which will be populated by new recruits from the breeding population as well as from the original in situ population. By establishing this, even if the main population is wiped out in the future, we will have a locally genetic population of Peak District white clawed crayfish in the area that would be available for possible reintroduction schemes.

In the meantime we are working with the local BAP partnership to support surveys, awareness raising initiatives and habitat work that will help understand and protect the species here in the Peak District.