Monitoring the distribution of crayfish in England and Wales.

The distribution of crayfish in England and Wales is described for the period 1997 to 2001 inclusive and is illustrated using a catchment based classification scheme and 10-km square maps. Comparison with previous data from the period 1990 to 1996 shows a decrease in the number of catchments where the native crayfish, Austropotamobius pallipes, is present. Conversely there has been an increase in the distribution of non-native species, notably Pacifastacus leniusculus, which is now more widely distributed than A. pallipes (according to presence within 10-km squares of the Ordnance Survey National Grid of England and Wales). The Environment Agency is the main environmental regulator in England and Wales, and plays a key role in gathering crayfish survey data. A co-ordinated programme of monitoring and reporting, ideally involving partner organisations, should be utilised to accurately reflect the changing status of crayfish in these countries. Crayfish survey data is currently recorded on a series of local databases within the Agency, and records are also stored on a national freshwater invertebrate archive used primarily for water quality monitoring purposes. Records generated by other groups and individuals are collated by the Biological Records Centre, with whom the Environment Agency has established links, and the need for a dedicated national database has been expressed by many workers. One area currently under development involves the National Biodiversity Network, a medium for sharing wildlife information via the internet, founded by a consortium of statutory and conservation organisations.