Ireland remains an important refuge for the freshwater crayfish Austropotamobius pallipes. To determine factors that influence their riverine distribution, forty rivers or tributaries of rivers that flow into Upper and Lower Lough Erne were sampled and surveyed. The nineteen sites where crayfish occurred had more bedrock and moss than those without crayfish, indicating the importance of a stable substrate and an indirect source of food. A subset of these sites, for which hydrochemical data were available, showed greater water hardness where crayfish were present, indicating that a high calcium water content is important to these animals. However, neither biological water quality nor invertebrate community structure varied between sites where crayfish were present and sites where they were absent. This indicates that biological factors have little influence on the presence of crayfish in a river and that crayfish influence biological water quality to a limited degree.
展开▼
