In Britain the white-clawed crayfish is our only native crayfish and is our largest freshwater invertebrate. It lives in clean, relatively hard, mineral-rich waters with a pH of between 7 and 9 and calcium concentrations above 5mgL -1. It is widespread in clean, calcareous streams, rivers and lakes in England but many populations have been lost since the 1970s.

The White-clawed Crayfish has now been identified as a priority species in the Biodiversity Action Plans of at least 12 planning authorities in the Yorkshire region.

As a result of legislative and conservation protocols the YNU has provided records and data on the former distribution of the White-clawed Crayfish in Yorkshire waters to a large number of planning authorities, statutory organisations, conservation bodies, academics and ecological consultancies.

Within the last decade the White-clawed Crayfish has been the subject of numerous site and river catchment surveys within the Yorkshire region, the results of which are being collated the Environment Agency.

Research paper: Gazetteer of White-clawed Crayfish in Yorkshire, by Colin Howes

Distribution map of White-clawed Crayfish from the NBN Gateway

photo by Defra