INTERACTION BETWEEN NATIVE AND ALIEN SPECIES OF CRAYFISH IN AUSTRIA: CASE STUDIES

Abstract

In Austria, three indigenous crayfish species occur: the noble crayfish (Astacus astacus), the stone crayfish (Austropotamobius torrentium), and the white-clawed crayfish (Austropotamobius pallipes). It is not known if Astacus leptodactylus is autochthonous in the very eastern part of Austria, near the border with Hungary and Slovakia. In other parts of Austria the Turkish crayfish has been transplanted into several gravel pits and ponds. Up to now, the red swamp crayfish (Procambarus clarkii) is not known to occur in the wild, but can be bought alive in fish markets, restaurants, and the aquarium trade. The Nearctic spiny-cheek crayfish (Orconectes limosus) and the signal crayfish (Pacifastacus leniusculus) have been introduced since the 1970s by crayfish farmers because these species are resistant to the crayfish plague fungus (Aphanomyces astaci). There are just a few populations of O. limosus, and the species is not spreading actively. However, P. leniusculus is widespread all over Austria, and was illegally introduced from one water body to another. It can be characterized as an aggressive, invasive North American species, spreading actively and acting as a vector of the crayfish plague. Unfortunately the habitat requirements of the native noble crayfish and the alien signal crayfish are nearly the same. Case studies are given in the following chapters: the first group of examples refers to water bodies where the alien signal crayfish is most probably the cause of displacement of the indigenous noble crayfish: 1) Hintersee, 2) Irrsee (« Zeller See »), 3) north-western Lower Austria (« Waldviertel »), 4) Merzenstein (aquacultural enterprise), 5) Neufelder See. The second group of examples refers to water bodies where alien and indigenous species are able to coexist: a) the confluence of the main course of the Danube River, the Ölhafen and the Neue Donau in the southeast part of Vienna, b) the Schönauer Wasser, a backwater of the Danube River downstream Vienna, c) backwaters and ox bows of the Morava River. The differences between these two groups are analysed, and it is speculated on possible causes allowing coexistence. Some conclusions are drawn. Important actions related to the protection of native crayfish are briefly discussed.