Crayfish distribution and data

Crayfish distribution in the UK

White-clawed crayfish populations are found in fragmented patches across England and Wales. The White-clawed crayfish has been declining rapidly across its range since the 1970s due to habitat loss, pollution, crayfish plague and competition from invasive crayfish species such as the North American signal crayfish (Pacifastacus leniusculus). As a result many populations of White-clawed crayfish have been lost in England and Wales.

The decline in White-clawed began in the 1970s and is continuing at a rapid rate across England and Wales. As the invasive species of crayfish (principally the Signal crayfish) spread northward and their populations have grown they have pushed the range of the White-clawed crayfish northward. This has had severe implications for the White-clawed crayfish as they cannot co-exist at the same site. Despite this decline there are populations of White-clawed crayfish persisting in areas such as: South Wales, Suffolk, East Midlands, Exmoor and the North York Moors. To illustrate the effect of invasive crayfish see maps below showing the decline in White-clawed crayfish distribution across the South-west from 1975 to 2009.

Approximate distribution of crayfish in the South-west in 1975 as created by Pete Sibley

Approximate distribution of crayfish in the South-west in 2009 as created by Pete Sibley