L. Forró szerk.: Miscellanea Zoologica Hungarica 8. 1993 (Budapest, 1993)

Vida, A.: Expected effects of the Gabčikovo river barrage system on the ichthyofauna of the Szigetköz and its values

the side branch systems of the flood-plain, the diversity of which was for many species indispensable. The species found in the main channel spawned in the side arm systems, and the different phases of fry development took place in this part as well. The following rheophilous, stenoecious species form an exception in this respect as they spawn in the main channel itself: Zingel zingel, Z. stréber, Gymnocephalus schraetzer, Salmo spp., Hucho hucho, Thymallus thymallus and Gobio kessleri. For this reason, the sub-montane character of the main channel is expected to change on the short run, and of the previously registered 57 species only 36 species will probably survive. These are usually those that are considered common in Hungary. However, even these species will occur in much lower numbers, thereby lowering the genetic value of the individual populations. Species probably disappeared in the past few months: Thymallus thymallus, Salmo trutta m. fario, S gairdneri, Hucho hucho, Chalcalbumus chalcoides mento, Phoxinus phoxinus, Pararutilus frisii meidingeri, Zingel stréber. Species expected to disappear within a few years: Eudontomyzon mariae, Acipenser ruthenus, Caspialosa kessleri pontica, Coregonus albula, C. lavaretus, Alburnoides bipunctatus, Gobio kessleri, Pelecus cultratus, Cottus gobio, Gymnocephalus schraetzer, Zingel zingel. Species expected to suffer serious population decline: Anguilla anguilla, Esox lucius, Cyprinus carpio, C. carpio m. hungaricus, Abramis brama, A. ballerus, A. sapa, Alburnus albumus, Aspius aspius, Barbus barbus, Blicca bjoerkna, Carassius auratus, Chondrostoma nasus, Ctenopharyngodon idella, Gobio albipinnatus, G. gobio, Hypophthalmichthys molitrix, H. nobilis, Leuciscus cephalus, L. leuciscus, Rutilus rutilus, R. pigus virgo, Vimba vimba, Cobitis taenia, C. aurata, Silurus glanis, Lota lota, Perca fluviatilis, Gymnocephalus baloni, G. cernuus, Stizostedion lucioperca, S. volgense, Proterorhinus marmoratus. Some of these species are positively affected, but are included in this list due to habitat loss. Species expected to be indifferent as regards to the changes: Pseudorasbora parva, Rhodeus sericeus amarus, Noemacheilus barbatulus, Lepomis gibbosus. Qualification of the main channel in the Szigetköz area and the expected changes according to the number of valuable fish species are shown in Fig. 1. All categories used throughout this study (endangered (e), vulnerable (v), rare (r) and intermediate (i)) after Lelek (1987). Fig. 1. Qualification of the main channel in the Szigetköz area and the expected changes according to the number of valuable fish species. All categories used throughout this study (endangered (e), vulnerable (v), rare (r) and intermediate (i)) after Lelek (1978).