Long-term changes in the fish community of Neusiedler See (Burgenland, Austria)

In the course of establishing the National Park Neusiedler See-Seewinkel, an investigation of the fish community of Neusiedler See on the Austrian/Hungarian border was carried out between 1990 and 1992. According to the literature, 19 indigenous fish species occur in the lake. In addition another ten species have occasionally been found in the lake but they are usually confined to the small tributaries of the catchment area. Seven alien species were introduced by stocking to enhance the professional fisheries (e.g., Anguilla anguilla, Ctenopharyngodon idella) or by aquarists (e.g., Lepomis gihhosus). Comparing the results of the present study with those of investigations before 1960, marked changes in species composition and abundance can be observed: four indigenous species have disappeared completely (Umbra krameri, Leucaspius delineatus, Misgurnus fossilis, Proterorhinus marmoratus) and the abundance of several species has declined considerably (e.g., Tinca tinca) while others, especially planktivorous species (e.g., Pelecus cultratus, Alburnus alburnus), show a pronounced increase in population density. The possible reasons for these changes are: