Recent distribution, population densities and ecological requirements of the stone crayfish (<i>Austropotamobius torrentium</i>) in the Czech Republic

Abstract

The stone crayfish Austropotamobius torrentium (Schrank) is one of five species of crayfish inhabiting waters in the Czech Republic, usually occupying small and medium-sized streams. The stone crayfish is protected by national and European laws. At present, stone crayfish are known to occur in 41 streams in the Czech Republic. For each of these streams, we measured the population density, sex ratio and age structure of the stone crayfish populations. The average population density varied between 0.3–4.72 spms·m−2, with a maximum estimated population density at some sites reaching 8.6 spms·m−2. The sex ratio was evaluated only in abundant populations (> 0.5 spms·m−2 and it did not significantly vary from the expected rate of 0.5 (0.3–0.72).