Year Cycle and Morphometrical Characteristics of Austropotamobius Torrentium from Two Karstic Rivers in Croatia

Stone crayfish (Austropotamobius torrentium) is one of the four native European crayfish species inhabiting Croatian freshwaters and is protected by Croatian law. The aim of this work was to investigate several aspects of species life cycle, morphometrics and habitat preferences. Populations were studied for 18 months in two streams in the Karlovac County. Crayfish were trapped once a month. Altogether 806 crayfish were analysed and their weight plus 7 morphometric characteristics per crayfish were recorded. Eight different physicochemical parameters of the water were measured. We found positive correlations between the number of captured individuals and water temperature, conductivity and water hardness. A negative correlation was found between the number of captured individuals and water level. The maximal recorded weight was 72 g for males and 43 g for females, while the maximal recorded body length was 11.02 cm for males and 10.37 cm for females. Freshly moulted animals were caught from June to November. Development of the glair glands started in July, external eggs were recorded from November to June and newly hatched juveniles were caught in June and July. The smallest egg-bearing female was 6.42 cm long. Males and females differed significantly in all measured morphometric characteristics and body weight, while crayfish from the two populations differed significantly in carapace width, claw length, claw width and claw height in males and in total body length, carapace width, claw height and width of the first abdominal pleura in females. It could be assumed that observed morphological differences between populations occurred due to crayfish adaptation to specific local environmental and ecological conditions.