Growth, morphometrics, size at maturity, sexual dimorphism and condition index of Austropotamobius torrentium Schrank

Growth, morphometric relationships and the size at maturity of the Stone crayfish Austropotamobius torrentium, a highly endangered European crayfish species, were investigated, in order to provide information for future protection management. Analyses of the weight-length relationship of A. torrentium revealed that males gained weight faster than females. This difference is due to an increased growth of chelae of males larger than 50 mm, which is assumed to be the size of sexual maturity of males. Female crayfish reached sexual maturity at 59 - 65 mm total length. The sex ratio in the studied sections of the brook Biberbach in Lower Austria was balanced. The estimated annual instantaneous growth rates ranged from 0 to 1.84. The growth rate declined rapidly in both sexes with increasing crayfish size. The crayfish condition showed the tendency to decline from May to August. The average crayfish condition was significantly higher in the section with superior current heterogeneity and percentage of potential shelter stones.