HABITAT FEATURES IMPORTANT FOR THE CONSERVATION OF THE NATIVE CRAYFISH AUSTROPOTAMOBIUS-PALLIPES IN BRITAIN

The survival of Austropotamobius pallipes in Britain is threatened by habitat modification, pollution, exotic crayfish species, and crayfish plague. The status of A. pallipes in the catchments of the relatively unpolluted Upper Wye and Upper Severn were surveyed in July/August 19 88. Sixty-two sites were visited and A. pallipes was found at 48% of t hem. The Llynfi and Teme sub-catchments were particularly well populat ed. A large number of environmental variables was measured at each sit e and multiple regression techniques used to determine which of the va riables most influenced crayfish abundance. It was concluded that, pro vided the water chemistry ensured crayfish survival, the size of the c rayfish populations was determined principally by the steepness of the channel banks, the presence of riparian shrubs and trees, and the ext ension of their roots into the water. The channel margins seemed to be especially important as nursery areas for the young crayfish. It is e ssential, where A. pallipes is to be protected or re-established, that these bankside features are retained, enhanced or restored.