DISTRIBUTION OF CRAYFISH AND CRABS IN THE UPPER REACHES OF THE KAMCHIYA RIVER, BULGARIA

250 Bulgarian Journal of Agricultural Science, 19 (2) 2013, 250 254 Agricultural Academy DISTRIBUTION OF CRAYFISH AND CRABS IN THE UPPER REACHES OF THE KAMCHIYA RIVER, BULGARIA E. STOYNOV 1, D. PARVANOV 2 and A. GROZDANOV 2 1 Fund for Wild Flora and Fauna, BG 2700 Blagoevgrad, Bulgaria 2 Sofi a University St. Kliment Ohridski, Faculty of Biology, BG 1164 Sofi a, Bulgaria Abstract STOYNOV, E., D. PARVANOV and A. GROZDANOV, 2013. Distribution of crayfish and crabs in the upper reaches of the Kamchiya River, Bulgaria. Bulg. J. Agric. Sci., Supplement 2, 19: 250 254 As a result of this study, twelve new localities were discovered and four indigenous species (noble crayfish Astacus astacus, narrow-clawed crayfish Astacus leptodactylus, stone crayfish Austropotamobius torrentium and Potamon ibericum) were found in a relatively small area in the upper reaches of the Kamchiya River Kotel Mountain (Eastern Stara Planina Mountain, Bulgaria). Extremely rare in Europe mixed populations of A. torrentium and A. astacus were detected in Golyama Kamchiya and Luda Kamchiya Rivers. The ratio of A. torrentium to A. astacus in the total catch decreased considerably from habitats with large stones and high water velocity to sites with small stones and relatively slow velocity for both locations with observed mixed populations. The obtained results are important for the development of management strategies with the aim of better crayfish and crab habitat protection in the circumstances of increasing anthropogenic impact. Key words: Astacus astacus, Austropotamobius torrentium, Astacus leptodactylus, Potamon ibericum, mixed populations, Kamchiya River Introduction There are three species of crayfish (Astacus leptodactylus Esch., Astacus astacus L. and Austropotamobius torrentium Schrank) and one species of freshwater crab (Potamon ibericum, Bieberstein) in Bulgaria. Their distribution was studied from the middle of the last century (Bulgurkov, 1961; Subchev and Stanimirova, 1998). In recent years, the data has been updated and new localities have been found (Subchev, 2001; Hubenova et al., 2002, Bechev, 2000; Bechev, 2004; Zaikov, 2004; Zaikov and Hubenova, 2007; Zaikov et al., 2010b, c; Zaikov et al. 2011a,b). In addition detailed investigations of the reproductive biology (Hubenova et al., 2002; Hubenova et al., 2010) and shelter competition between different age groups and species have been made (Zaikov et al., 2001; Zaikov et al., 2004; Zaikov et al., 2010a). However, the data about freshwater decapods in Eastern Bulgaria, especially in Eastern Stara Planina Mts. and Kamchiya River is rather scarce. The noble crayfish (A. astacus) and the stone crayfish (A. torrentium) have been included as endangered species in the Bulgarian Red List and have been listed in the Annex IV of European Community Directives for the Conservation of Natural habitats and wild Flora and Fauna (97/62/EU) as subject of special conservation measures. In producing this paper, the authors aim to provide new information about the distribution of crayfish and crabs in Bulgaria. An additional aim of this article is to inform and promote the development of appropriate management strategy for the conservation of crabs and crayfish habitats in the upper reaches of Kamchiya River in relation to the establishment of Natura 2000 network. *E-mail: pirin@fwff.org

Distribution of Crayfish and Crabs in the Upper Reaches of the Kamchiya River, Bulgaria Material and Methods Between 2004 and 2011, twelve localities on the upper reaches of the Kamchiya River were examined periodically for the presence of freshwater crabs and crayfish. The localities included the main river and most of its major tributaries (Golyama Kamchiya, Luda Kamchiya, Kotleshnica, Medvenska, Glogova and Neikovska rivers). At each river site, locations for sampling were selected based on ease of access to the shore and identification of areas believed likely to provide suitable crab and crayfish habitat (Figure 1). Crabs and crayfish captured were counted and identified. After these procedures, the individuals were released back to the water. In some locations, local anglers provided additional material. Three sampling methods were used to catch crabs and crayfish: (1) Direct hand sampling from the river bed, by searching spaces between rocks and within the roots (2) By ring net, which is basically a basket made of two solid rings connected by cotton or nylon 0.6 cm mesh. The top ring has a larger diameter (50 cm) than the bottom ring (30 cm). When deployed, this kind of trap becomes flat on the river bottom, giving crabs and crayfish access to the bait in the centre. (3) A new highly effective method with а fishing rod, cord, safety pin and bait attached to it was used. The bait (small fish (e.g. Phoxinus phoxinus, Linnaeus, 1758), earth- Fig. 1. Habitat of noble and stone crayfish in Golyama Kamchiya River near Ticha Village Altitude: 400 m Geographic coordinates: 42 58 23.23 N / 26 23 23.48 E 251 worm or piece of meat) is moved up and down in front of the crayfish hole. The method is also called thumping because during the crayfishing the bait frequently touches the bottom of the river. During this process, the crayfish come out from their shelter, attracted by the bait and its specific vertical movement and began to look for it. Once the crayfish has the bait firmly in his claws, the bait is raised to the water surface (Figure 2). All of the crabs and crayfish caught were determined to species (Pöckl et al., 2006; Zaikov, 2010). Results and Discussion Throughout this research a total number of 837 crayfish (356 A. astacus, 242 A. torrentium; 232 A. leptodactylus) and 129 crabs (P. ibericum) were caught. The presence of three crayfish species (the noble, the narrow-clawed and the stone crayfish) and one crab species (Potamon ibericum, Bieberstein, 1808) have been discovered (Figure 3). During the research period twelve of the investigated localities were inhabited by certain species, three populated by the stone crayfish (Austropotamobius torrentium, Schrank, 1803), eight by the noble crayfish (Astacus astacus, Linnaeus, 1758), two by the narrow-clawed crayfish (Astacus leptodactylus, Eschscholtz, 1823) and one by the Potamon ibericum. The population of Potamon ibericum in Medvenska River is the first locality reported in the Kamchiya River Fig. 2. Crayfishing in Kotleshnica River using thumping method

E. Stoynov, D. Parvanov and A. Grozdanov 252 Fig. 3. The distribution of freshwater crayfish and crabs in the upper reaches of Kamchiya River Fig. 4. Crayfish captured in Golyama Kamchiya River between the villages Bratan and Ticha (13.08.2004) (a) Male noble crayfish (Astacus astacus). (b) Male (up) and female (down) stone crayfish (Austropotamobius torrentium)

Distribution of Crayfish and Crabs in the Upper Reaches of the Kamchiya River, Bulgaria 253 Basin. The other populations of this freshwater crab in Bulgaria were described in Tundja, Maritsa, Arda and Mesta rivers by previous reports (Subchev and Stanimirova, 1998; Bechev, 2004). Potamon ibericum was observed in different regions from the Black Sea catchment area such as the rivers in Strandzha Mountain and near Varna. Despite the wide distribution of this species in Bulgaria and the relatively high number of localities, some of its populations are fragmented, and the threat level from pollution and climatic changes is high, so there is cause for concern for the future of some of its populations including the newly discovered one in Medvenska River. Mixed populations of A. torrentium and A. astacus were found in Golyama Kamchiya and Luda Kamchiya rivers (Figure 4). These localities are the only places, reported in Bulgaria, where the latter two species of crayfish occur together. Mixed populations of these species were found in other European countries the Czech Republic (Kozak et al., 2002), Germany (Sint et al., 2006), Croatia (Magiure and Gottstein-Matocec, 2004) and Romania (Parvulescu and Petrescu, 2010). The reason for the rare occurrence of these mixed populations is still not known. The sites where characterized by having both banks of the river shaded by trees (Figure 1). The species occur on a substrate consisting primarily of stone and gravel, the preferred shelter is represented by the spaces under and between stones. The most frequent combination of riparian vegetation is. Alnus sp. and Salix sp. The ratio of A. torrentium to A. astacus in the total catch decreased considerably from habitats with large stones and high water velocity (mean 2.31; standard deviation 0.43) to sites with small stones and relatively slow velocity (mean 0.96; standard deviation 0.12) for both locations with observed mixed populations. On the other hand, the ratio was relatively stable in the investigated two localities during the whole period. It is well known that a close relationship exists between stream morphology, substrate and abundance of crayfish species (Payne, 1984). Highest densities of Astacus astacus occurred in gravel and stony areas (Niemi, 1977), whereas A. torrentium abundance was correlated to the relative amount of stones and pieces of wood serving as a shelter for this crayfish (Pockl and Streissl, 2005). One of the distinctive features of the latter species is his preferences to large stones with shape that has little difference between length and width and a bearing surface between 300 cm 2 and 900 cm 2 (Streissl and Hodl, 2002). Another important factor is the aggression potential of different native and introduced crayfish species (Vorburger and Ribi, 1999; Zaikov, 2004; Zaikov, 2010a), but up to now no comparative investigations dealing with the aggression potentials of A. astacus and A. torrentium living in the same habitat have been performed. The observed results about the ratio between these two species showed that A. torrentium is able to exclude larger specimens of the other crayfish from shelter and may show a generally more aggressive behavior than Astacus astacus. However, it could be assumed that the main factor that was responsible for the reported larger numbers of A. torrentium compared with those of A. astacus in specific parts of the studied localities was the size and shape of the river stones. Conclusion Three indigenous crayfish and one crab species were found in a relatively small area in the upper reaches of the Kamchiya River. 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