Ábrahám Levente: Biomonitoring a Dráva folyó magyarországi szakasza mentén 2000-2004 - Natura Somogyiensis 7. (Kaposvár, 2005)

Héra, Zoltán: On experiences in monitoring molluscs (Mollusca) in the area of Duna-DrávanNational Park - A Duna-Dráva Nemzeti Park térségében végzett puhatestű (Mollusca) monitoring tapasztalatai

26 NATURA SOMOGYIENSIS 2. Sampling applied in monitoring invasive species Potamopyrgus antipodarum - collecting 3 m

3 deposit and underwater individual sampling in 4 (50x50 cm) quadrates. Arion lusitaniens - single individual sampling counts on 10 m

2 site. Dreissena polymorpha - collecting 5 dm

3 alluvial deposit (possibly float debris) once a year. Anodonta woodiana - individual sampling from the riverbed to determine absence, once a year. Helicella obvia - indivividual sampling to determine absence, once a year. 3. Monitoring water fauna Collecting alluvial float debris three times a year, float debris from lakes once a year with skimming net, collecting 5 dm

3 material on each occasion. Quadrate method: underwater counts of individuals on 10 sites of 50x50 cm quadrate, four times a year. Sweep - netting on riverbed with a 0.5 mm wide scraping net of 1 mm meshes on a 2 m stretch five times a year. Single individual sampling with a dipping - net or from plants picked out of water with a handle holder, once a year. 4. Monitoring terrestrial fauna Collecting 25 dm

3 surface debris twice a year. Single individual sampling of slugs for 20 minutes once a year. Collecting fluvial float debris three times a year, collecting float debris from lakes once a year with a skimming - net, 5 dm

3 material is collected on each occasion. Sampling of mollusc communities living in wood assemblages by hiding place quadrate. Results and conclusions During monitoring protected species we managed to prove the presence of 10 mollusca and 2 bivalves species. Strictly protected species were not present among them (Fig. 1). Amphimelania holandri (Pfeiffer, 1828) a tertiary fossil species with an East and West Balkan distribution, lives in the Dráva and the Sava water system. In the Hungarian waters this species lives in the Dráva, the Zala, the Kerka and the Mura. Its habitat in the section between Bolhó and Őrtilos is on pebbly sandbanks, but it also settled on spurs and protective paving of the bank. On the sampling site near Vízvár, according to the investigation data, it lives in a density exceeding 300 individuals/m

2

. Among concomitant fauna members Ancylus fluviatilis (Müller, 1774) can be found. In case the planned Croatian power station near Novo Virje is constructed, this habitat and the undelying pebbly sandbank would be destroyed or severly damaged due to the drastic changes in the course of the river. After halfa century Theodoxus danubialis (C. Pfeiffer, 1828) is present on the national stretch of the Dráva. The first report about its presence comes from Soós (1933), formerly it was collected in Légrád (now on Croatian territory). In 1997 one shell was found in the float debris (VARGA and UHERKOVICH 1997). In the autumn of 2001 it was present in mass with an individual density exceeding 200 specimens/m

2 at the mouth of the Mura in Őrtilos at various times (HÉRA 2002). Colonization may have come from the Mura as it occurs in the upper section. Pomatias elegáns (С. Pfeiffer, 1828) lives on the slopes overlooking the Dráva in the environs of Őrtilos hills. Once it may have been more widespread in the country. At present it can be found on the Tihany Peninsula, in the Zala hills and in some parts of the