Crayfish Survey

By Kate Linck, Conservation Assistant, Worcestershire Wildlife Trust.

Worcestershire Wildlife Trust and the Environment Agency are just about to start a crayfish survey of Worcestershire. I have recently started working as a volunteer at Worcestershire Wildlife Trust, and my role is as co-ordinator of the Wildlife Trust section of the survey. Such a survey has never been done in the county before, and it is an essential preliminary to the effective conservation of our native white-clawed crayfish, and for the successful implementation of the Species Action Plan for the Worcestershire Biodiversity Action Plan.

The white-clawed crayfish Austropotamobius pallipes is currently under threat from introduced non-native crayfish, particularly the signal crayfish Pacifastacus leniusculus. The signal crayfish was originally introduced into England in the mid-1970s, in an attempt to develop a stock of crayfish immune to crayfish plague Aphanomyces astaci, but with the same culinary characteristics of the European noble crayfish. However, although normally immune to the fungal disease themselves (except occasionally when under stressful conditions), these alien crayfish are carriers of crayfish plague, to which the white-clawed crayfish are highly susceptible. The spores can also be transmitted by water, damp angling equipment, birds, animals, and by fish, (although signal and native crayfish appear to be the only hosts).

The signal crayfish poses another threat to the white-clawed crayfish, as they are also more successful when competing for food and habitat.

Due to the introduction of non-native crayfish, over the past 20 years there have been catastrophic declines in native population numbers. At present the white-clawed crayfish is listed in Appendix III of the Bern Convention and Annexes II and V of the EC Habitats Directive. It is classed as globally threatened by IUCN/WCMC. It is also protected under Schedule 5 of the Wildlife and Countryside Act 1981 in respect of taking from the wild and sale.

The aim of Crayfish Survey 2000 is to establish the status and distribution of both the native white-clawed crayfish, and non-native crayfish within the county of Worcestershire. The ultimate objective being to gather vital information in order to maintain the present distribution of the white-clawed crayfish by, specifically, limiting the spread of crayfish plague, preventing the spread of non-native species, maintaining suitable habitat, and identifying any potential re-introduction sites.

If you know of any crayfish in Worcestershire, please let me know, (include: location, grid reference, species if known, numbers, and date). Also, if you want to get involved with Crayfish Survey 2000, don't hesitate to contact me at Worcestershire Wildlife Trust Tel: 01905 754919).

(see also Mike Averillís article Crayfish in Worcestershire in Worcestershire Record No. 2, pages 4-5, April 1997. This also refers to an article by HOLDICH, D 1991 The native crayfish and threats to its existance. British Wildlife 2, 1, 141-151 which contains good photographs and diagrams to aid identification of crayfish. Both the law and situation have changed considerably since the article was written).

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