White-clawed crayfish
1 March 2010
The white-clawed crayfish was once widespread in English rivers and lakes with calcareous (‘hard’) water. Over the past 30 years, populations have been decimated by the spread on non-native crayfish species and a disease that they carry. Few strongholds remain, and many remaining populations are vulnerable to extinction.
(c) Natural England/Paul Glendell
Latin name: Austropotamobius pallipes
Population numbers: Unknown. The species has been lost from around 60% of the area of England and Wales where it occurred in 1970. It has been estimated that, if current trends continue, the species is likely to become extinct within 30 years.
Where to see and when: White-clawed crayfish spend most of the day hiding under large stones or in the banks of rivers and lakes, so you have to search to find them. They are now extinct from many catchments, with the best surviving populations tending to be in the north of England beyond the advancing front of non-native crayfish. The species is strictly protected, and it is illegal to take them from their habitat without a licence. In most places it is more likely you will find the bully-boy of the crayfish world, the non-native signal crayfish.
What’s being done: No cost-effective control techniques have yet been found for eradicating non-native crayfish once established in a river or lake. Even in waters where non-natives have yet to reach, crayfish plague can wipe out native crayfish populations simply by the transfer of infected water or fish. Conservation efforts are therefore focusing on creating Ark sites, remote from the threat of invasion by non-native crayfish and from the transfer of plague, so that there are at least some safe havens for remaining populations.
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