A keystone species
In Devon, white-clawed crayfish survive in just two river systems: the Culm and the Creedy-Yeo. Research shows that, without help, white-clawed crayfish could disappear from Devon – and the UK – within a few years. They are classified as endangered on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species and are protected under European and UK legislation.
Their disappearance would be devastating, as white-clawed crayfish are a keystone species of UK rivers and streams. Their presence indicates good water quality and they have a valuable role in the ecosystem, providing food for larger animals like otters.
An invasive rival
Native white-clawed crayfish are not only being pushed to the brink of extinction by water pollution and habitat degradation, but also by the presence of other crayfish species.
The American signal crayfish was introduced into the UK in the 1970s. These animals are not only larger – outcompeting native crayfish for food and territory – but they are also responsible for spreading the deadly ‘crayfish plague’. This is a fungal disease that American signal crayfish are immune to, but is lethal to white-clawed crayfish.
Creating ark sites
Wild Planet Trust has been helping to ensure the survival of the white-clawed crayfish by creating ark sites (safe, self-contained locations) in East Devon, and releasing breeding-age individuals into these sites.
Since 2019, approximately 50 animals have been bred by the Bristol Zoological Society and released, under licence, into an ark site in the River Culm catchment, with the hopes that populations will become self-sustaining.
We are now planning to develop more ark sites around the Creedy and Yeo rivers to enable these highly threatened animals have a secure future in Devon.
Now that the ark sites have been established and breeding-age crayfish have been introduced, Wild Planet Trust and the Blackdown Hills AONB will continue to actively monitor and maintain the site to assess the health of the population.
Working in partnership
The project is being run in collaboration with Wildwood Trust, Bristol Zoological Society, the Environment Agency, local crayfish specialist Dr Nicky Green, the Blackdown Hills AONB and the South West Crayfish Partnership. Volunteers from the local community also help by surveying the river for both native and invasive crayfish, carrying out water-quality checks, and preparing the ark sites for release.