Abstract

In contrast to the other European crayfish species the distribution of Austropotamobius torrentium should reflect the preferred habitat of this species: Due to their small body size they are of no commercial interest and thus were not artificially stocked. In addition, they are largely unaffected by the introduced American crayfish species, which could not invade their turbulent habitat. However, due to its low economic value little is known about population structure and habitat characteristics of this species. We examined five populations of Austropotamobius torrentium in the Constance area: Four populations inhabited brooks of 80 to 200 cm in width and 4 to 15 cm in depth and one population lived at the shore of the outlet of Lake Constance into the River Rhine (down to 300 cm water depth). Flow speeds ranged from 1 cm/sec to 62 cm/sec. The population density varied between 6 and 12 individuals per metre shore length. In the laboratory when offered food collected from their habitats the crayfish showed a broad food spectrum including annelids, molluscs, insect larvae, amphipod crustaceans, small fish, macrophytes, and rotting leaves. Crayfish diet changed with seasons: In summer at T = 14°C the proportion of animals to plants was higher (1:1) than in spring (0.4:1) at T = 7°C. The preference for plants in spring may be related to the lack of plant specific nutrients or minerals during winter. Supported by DFG.

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