Estimating age composition in Alpine native populations of Austropotamobius pallipes complex

Assessing the population structure and understanding growth patterns is crucial to manage freshwater resources and to solve fundamental questions concerning endangered species conservation. Austropotamobius pallipes (Lereboullet, 1858) species complex has been declining on a widespread basis in Europe, including Italy, but detailed data on population structure and growth are lacking. In four mountain streams populated by the species, water temperature data were collected by data-loggers. In July 2012, a total of 746 crayfish were collected at night and their length was measured. Females and males size distributions were analysed separately for each stream using Bhattacharya’s Method. Age was assigned to each length class. The mean values of the age classes were used to evaluate the growth rate of Von Bertalanffy, by the seasonalized equation. Up to six age classes were identified in two populations. Results show that three out of four populations are well-structured, and they confirm that A. pallipes complex is a K-selected species. We stress the need for long-term monitoring and the importance of obtained results in development of conservation plans of endangered crayfish.