Priority Species: White-clawed Crayfish
1. Maintain the present distribution of white-clawed crayfish populations
2. Maintain and create appropriate habitat conditions for white-clawed crayfish.
3. Where feasible, restore white-clawed crayfish populations to watercourses within their former range
Vision Statement: To maintain populations of white-clawed crayfish in off stream and upland stream locations and to safeguard these populations against crayfish plague.
|1. To maintain the current range of white-clawed crayfish in the Durham BAP area.||maintain||number of sites||11|
|2. To expand the range of white-clawed crayfish by establishing new populations in off-stream or upland stream locations in the Durham BAP area.||expand||number of sites||1|
The white-clawed crayfish is the only species of freshwater crayfish native to the UK. This crustacean is found mainly in clean, calcareous streams, rivers and lakes. It is one of the UK’s largest mobile freshwater invertebrates, growing up to 10-12cm in length. The species gets its name from the pale undersides to its claws; the rest of the crayfish is dark greenish brown. Three non-native crayfish species are now breeding in the wild in the UK; these were introduced into the country and farmed but have escaped into river systems. These are the American signal crayfish (Pasifastacus leniusculus), the noble crayfish (Astacus astacus) and the Turkish crayfish (Astacus leptodactylus).
As across most of the UK, white-clawed crayfish are thought to have declined dramatically over recent decades in the DBAP area, but the scale of the decline is unknown due to a lack of survey data. It is thought that habitat loss and competition from non-native crayfish species are the main reasons for the decline, but again no comprehensive studies have been carried out.
There are no known white-clawed crayfish populations in the River Wear or its tributaries and it is suspected that the species was not native to the Wear or has been absent for centuries. White-clawed crayfish are found in the Tees catchment, but there are only sporadic records. However, there are two known populations located in still waters, one in the Durham area and one in the Tees valley.
- Loss of habitat due to inappropriate management of riparian habitats.
- Competition from non-native crayfish species.
- Transmission of crayfish plague via non-native crayfish species or through fish stocking.
- Poisoning by pollutants, for example synthetic pyrethroids.