The distribution of the crayfish, Austropotamobius pallipes, in British waters

SUMMARY. The distribution of Austropotamobius pallipes , the only freshwater crayfish indigenous to the British Isles, is examined using over 300 records collected since 1970. The majority of records are for England where crayfish are found in areas associated with base-rich easily weathered substrata. Waters containing crayfish tend to be in the pH range 7–9, with calcium levels above 5 mg l⁻¹. Crayfish are found in a wide variety of habitats ranging from deep water-filled quarries with a soft substratum to shallow fast-flowing streams.