The White-clawed Crayfish is the only native species of freshwater crayfish in the UK. It was formerly widespread throughout Europe but due to severe declines across its range, the remaining populations are becoming increasingly fragmented. It was widely distributed in Britain and Ireland until the 1980s, but factors such as crayfish plague and competition with introduced species have contributed to the loss of many populations. Up to 24% of the global population of the White-clawed Crayfish is thought to be sustained in the UK and it is relatively abundant in central and northern areas of England and in Wales.

White-clawed Crayfish are olive-green to brown in colour and their common name refers to the off-white to pinkish colour of the undersides of their claws. They grow up to 12 cm in length and live from 7 to 12 years. They are nocturnal and omnivorous and are found in a range of aquatic habitats, such as lakes, rivers, streams, canals or quarry pools. Crayfish prefer unpolluted, calcareous waters with limited sediment and plenty of shelter in the form of rocks, aquatic plants and tree roots. They have many predators such as otter, mink, rats, birds (such as heron) and fish (such as pike and trout).

Breeding usually takes place in the autumn. The eggs develop whilst attached to the female’s abdomen and hatch in late spring or early summer. Juveniles may moult more than seven times in their first year, but then only once annually after reaching maturity.

Since the commercial introduction of the non-native North American Signal Crayfish (Pasifastacus leniusculus), the native White-clawed Crayfish has suffered due to direct competition for food and habitat as well as from crayfish plague. Crayfish plague is a virulent fungal disease caused by the fungus Aphanomyces astaci and Signal Crayfish are a known carrier of the fungus with little apparent harm caused to them. Native crayfish populations however are known to have been destroyed by the disease within a matter of days. Spores from the fungus can be transported from population to population in water, mud, damp equipment and fish from contaminated waters. In addition to Signal Crayfish, two other non-native crayfish species are now breeding in the wild in the UK.

Another factor affecting the White-clawed Crayfish is the destruction and fragmentation of suitable habitat due to modification and management of watercourses and water bodies. Water pollution (especially urban and agricultural run-off, and domestic sewage) and increased sediment levels have also caused White-clawed Crayfish populations to suffer.


The White-clawed Crayfish has declined to the extent that it is considered ‘Globally Threatened’ by the IUCN and the species is protected under the Wildlife and Countryside Act (1981), making it illegal to:

intentionally kill, injure or take from the wild;

sell, offer for sale, possess or transport for the purpose of sale and live or dead animal or part thereof. The species is listed on Annex II of the European Habitats Directive (92/43/EEC). The White-clawed Crayfish also has a Species Action Plan and is a Priority Species under the UK Biodiversity Action Plan. The EC Water Framework Directive’s requirement for maintenance of good ecological status of aquatic ecosystems is also important for the management of White-clawed Crayfish habitats.

When considering planning applications, the authorities are required by law to take account of protected species and the conservation of habitats. A detailed ecological survey is usually required before planning permission can be granted.


Habitat assessment can be undertaken at any time of year but surveys can only take place from mid-July to the end of September to ensure females are not disturbed while carrying eggs. The main survey technique used is active searching in suitable habitat, though this method is only suitable during times of base (i.e. low) flow in streams. Night searching by torch is recognised as an effective method in addition to trapping, which may be a suitable option in deep, slow moving pools where active searches cannot be conducted.


Any activity likely to contravene legislation in regard to protected White-clawed Crayfish populations will require a licence. Applications for licences must be submitted to Natural England by a competent ecologist, i.e. a person able to demonstrate to the satisfaction of Natural England that they have the relevant skills and knowledge of the species concerned.