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

Tóth, Sándor: Monitoring dragonflies on the section of the Drava between Őrtilos and Vízvár (Insecta: Odonata) - Szitakötők monitorozása a Dráva mente Őrtilos és Vízvár közötti szakaszán (Insecta: Odonata)

Natura Somogyiensis 7 35-48 Kaposvár, 2005 Monitoring dragonflies on the section of the Dráva rr between Ortilos and Vízvár (Insecta: Odonata) TÓTH SÁNDOR 8420 Zirc, Széchenyi u. 2. Hungary flycatcher@vnet.hu TÓTH S.: Monitoring dragonflies on the section of the Dráva between Ortilos and Vízvár (Insecta: Odonata) Abstract: The power plant planned on the Croatian section of the Dráva can result in unfavourable changes in the fauna of wetlands by the river and may - among others - affect the dragonflies developing there, too. This necessitates the long-term monitoring of the local dragonfly fauna. Already the experiences of the first few years of monitoring referred to the fact that the shallower wetlands of the area are particularly vulnerable. In the course of the examinations it turned out that the dragonfly fauna of the area is rich -14 of the 48 species detected so far are protected by law. Outstanding among these are the 5 taxons listed in the Bern Convention (Aeshna viridis, Gomphus flavipes, Ophiogomphus cecilia, Leucorrhinia caudalis, Leucorrhinia pectoralis). The composition of the local fauna - similarly to the national situation - is dominated by Pontic-Mediterranean, Siberian and West-Siberian faunal elements. However, the proportions alter to some extent from group to group. The author gives a detailed analysis of the composition of the fauna of the individual sampling sites and offers a separate depiction of the quantitative composition of the fauna according to the subordo. Key words: Odonata, Drava river, biomonitoring Introduction The operation of the power plant planned for the Croatian area of the Dráva (Novo Virje) is expected to affect the wetlands by the river, particularly the fauna living there and bound to the water due to the development of its larvae: such as dragonflies among others. Dragonflies (Odonata), as insects developing in the water and sensitively reacting to the characteristics of the habitat (indicator organisms), are suitable for tracking the changes occurring in the condition of the habitat. The examinations carried out with them are facilitated by the fact that the Hungarian fauna is well-researched and the number of permanent species is relatively low: altogether 65. As a result of the odonatological examinations in process for a longer period in the area of the Duna-Dráva National Park, the dragonfly fauna of the area is relatively well known. Based on the publications prepared in the course of the work (DÉVAI 1978, 1981, DÉVAI et al. 1978, 1993, TÓTH 1995, 1998), the occurrence of altogether 54 species (83 per cent of the Hungarian fauna) can be regarded as proven. The monitoring of dragonflies can be built on larvae, exuviums and imagoes as well. Undoubtedly, primarily the survey of imagoes is justified in the establishment of a quantitative fauna picture. In spite of this, especially in certain periods, e.g. in early spring (when imagoes do not yet fly) and late autumn (when most of the species do not fly any longer) it is worth collecting larvae, too. Collecting exuviums is much easier and far