Distribution and Current Status of Stone Crayfish Populations Austropotamobius torrentium (Decapoda: Astacidae) in Natura 2000 Protected Areas in Bulgaria

The stone crayfish Austropotamobius torrentium is one of the three native crayfish species occuring in Bulgaria (the other two are Astacus astacus and Astacus leptodactylus), which is protected by many European and national laws. In comparison with other European countries little is known about the population status of stone crayfish in Bulgaria. The aim of this work was to summarise newly collected data on the distribution and population status of A. torrentium in Natura 2000 protected areas in Bulgaria. This study was carried out from September 2011 to November 2012. During this period 994 localities in 570 different rivers and streams from 76 Natura 2000 protected areas were studied. A total of 2340 individuals were found in 112 localities from 83 rivers and streams in 30 protected areas. Stone crayfish had comparatively restricted and uneven distribution in Bulgaria and its populations were characterised by a relatively low abundance (0.002 - 0.34 ind./m(2)). The species was found in the range from 189 m to 1342 m a.s.l., but it was mainly located from 300 to 900 m (78.5% of all localities). There was a clear trend for the distribution of species in high mountains, where it was wider distributed in southern slopes and did not occur or was rare in northern slopes. Stone crayfish was found mainly in rivers with banks covered by beech (Fag-us sylvatica), alder (Alnus glutinosa), oak (Quercus spp.) or sycamore (Platanus orientalis), and rarely in rivers with banks covered only by bushes. The species was almost completely absent in the exposed areas of the rivers and in the areas with coniferous vegetation. All our findings can be used as a basis for future monitoring of the state of stone crayfish populations and assessing the conservation status of the species in Bulgaria.