Distribution and ecology of

In Germany, three species of native freshwater crayfish are found : the noble crayfish (Astacus astacus), the stone crayfish (Austropotamobius torrentium) and the white-clawed crayfish (Austropotamobius pallipes), which occurs very rarely. The distribution of white-clawed crayfish (A. pallipes) in Germany is restricted to parts of the south-west, east of the Rhine in the area of the city Freiburg (Germany). This is the north-eastern limit of the distribution. The occurrence of this species in Germany was first described in 1989 (TROSCHEL and BERG, 1989). It has now been discovered in eight localities. To characterize the biotops, the hydrochemistry was investigated and the structure of two typical streams evaluated. The wide variation of the water parameters indicates that the presence of A. pallipes is not dependent on the water chemistry. It is clear that the stream morphology is vital for the occurrence of this species. The variation of depth (0.05 - 0.5 m) and width (1 - 5 m) is large and there are numerous hiding places for the crayfish among the stones, decaying wood and tree roots. A. pallipes and A . astacus are found in the lower parts of the river whereas A. torrentium is found more in the headwaters. These three species are protected by the Fish Protection Act. Normally, non-native species do not invade the biotops of A. pallipes and the danger of transported Aphanomyces astaci is small.