Alien crayfish in the streams of the Wyre Forest: avoiding contamination

The stream-walking volunteers have had to be mindful of aliens: and no that doesn't mean the latest Doctor Who monster, but an alien species of crayfish that can cause problems for the native crayfish in the streams of the Wyre Forest.

Atlantic Stream or white-clawed crayfish, courtesy Rosemary Winnall

The Atlantic Stream or white-clawed crayfish (Austropotamobius pallipes) is the native species of crayfish found in the British Isles. There has been a significant decline in native crayfish populations across England and Wales in recent years, and this has also been the case locally too. Much has been written about the local problem (see links below), and a major culprit for the decline is likely to be the invasion of local streams by an alien, or non-native crayfish, in particular the American Signal crayfish (Pacifastacus lenuisculus) which carries a disease (a fungal pathogen) which attacks the native crayfish.

American signal crayfish, courtesy Rosemary Winnall

American Signal Crayfish, courtesy Rosemary Winnall

Volunteers have been advised to take precautions to avoid the spread of the pathogen. As the alien crayfish is found mainly in some of the tributaries, the Dowles and the Baveney Brooks, one of the precautions has been to stream-walk each brook and tributary separately to avoid stream-hopping. Stream-walking was, therefore, carried out separately by different volunteers for each watercourse. The fungal pathogen does not survive for long outside water, so washing waders and leaving them to dry before re-visiting any of the streams was also a precaution. Obviously, there is the potential for contamination to be innocently spread by members of the general public, but at least for the purposes of the survey, we can keep this likelihood to a minimum.

Our last post showed the photograph of the claws of an American Signal crayfish on the Baveney Brook (the remains, possibly, of an otter meal) taken by volunteer Terry, showing that the alien crayfish still lurk in that stream. Note the larger, broader claws, which are one of the traits differentiating the Signal crayfish from the native crayfish.

Thanks are due to Dr Graham Hill of Hills Ecology Ltd and Cody Levine of Worcestershire County Council for their advice. All images are courtesy of Rosemary Winnall of Wyre Forest Study Group.

By Liz Pearson
lpearson@worcestershire.gov.uk; Google+

Links

Atlantic Stream (White-Clawed) Crayfish in the Wyre Forest

Crayfish of Wyre Forest - an update

Dowles Brook Wyre Forest crayfish survey