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

HÉRA Z.: ON EXPERIENCES IN THE MONITORING MOLLUSCS 29 Mecsek Mountains. This Mediterranean species with West-European distribution has a density of 20 individuals/m

2 on the humid and cool soil of Ortilos mixed beech woods. In some places this species can be found in the same habitat with a species, Ena топtana (Drapernaud, 1801) of Alpine - Carpathian distribution and a preference for mountainous climate (HÉRA and VARGA 2001).The latter is a rare species even in our mountainous regions. In the Zákány-Őrtilos hilly range 2 isolated species were recorded during monitoring investigation. The expansion of grapeyards and orchards on the account of beech woodlands endangers the survival of this species. On the basis of the investigation the estimated number of individuals is 200. The population of Cepaea hortensis (0. F. Müller, 1774) living in the upper cemetery of the village of Zákány is also isolated. The size of the population is about 500 individuals, so far only with yellow shells, either plain or streaked genetical variants have been found. Its habitat is bordered by intensively treated areas, so its dispersion is unlikely. Mollusc species generally spread in groves along the Dráva are Perforatella bidentata (Gmelin, 1788) and Cepaea nemoralis (O. F. Müller, 1774). Their empty shells are usually present in the float debris of the river. Helix pomatia (Linnaeus, 1758) can be frequently found in the woods and in the weeds. Vertigo angustior (Jeffreys, 1830) and Vertigo moulinsiana (Dupuy, 1849) are snail species with unknown habitat and population size. These small molluscs settle on vegetation close to the soil in humid habitats, their empty shells were found in floating debris. We managed to reveal the presence of individuals belonging to 2 protected bivalve species, Pseudanodonta complanata (Rossmässler, 1835) (Fig. 2.) and Unio crassus (Philipsson, 1788) in the Dráva and its tributaries. The methods applied do not make possible to estimate population size. It is certain that, compared to other large-bodied Gastropods, both species proved to be rather scarse on slow - flowing sections of the riverbed along the bank and also in the temporary dry and muddy branches. Table 1.: The protection state of species recorded during monitoring investigation Species 3 В о о о 2 2 О и s а си Ц о м о, ° В |£ с о и о о о (N OS В ев со •g s as м о Pomatias elegáns protected 1982 Ena montana protected 1993 Helix pomatia protected 1993 X V. Theodoxus danubialis protected 1993 Amphimelania holandri protected 2001 Cepaea hortensis protected 2001 Cepaea nemoralis protected 2001 Perforatella bidentata protected 2001 Pseudanodonta complanata protected 2001 LR/nt Unio crassus protected 2001 П., IV. LR/nt Vertigo angustior protected 2001 п. LR/cd Vertigo moulinsiana protected 2001 п. LR/cd