|CS17 Invasive Species|
|Date: Thursday, June 13, 2002|
|Time: 11:00:00 AM|
|Zweimueller, I, , IECB, Vienna, Austria, email@example.com|
|RAPID ESTABLISHMENT OF TWO INVASIVE PONTO-CASPIAN FISH SPECIES (GOBIIDAE) IN A BACKWATER SYSTEM OF THE AUSTRIAN DANUBE |
|Neogobius kessleri and N. gymnotrachelus have expanded their range from the lower to the upper Danube, where they were first recorded in an Austrian backwater system in the mid- to late 1990īs.
Using long-line fishing and beach seine catches benthic fishes were surveyed in this backwater in 1995 and 2000. In 1998 the connectivity with the Danube and within the backwater-system was increased by lowering parts of summer dykes and check-dams. This study is part of the accompanying ecological impact assessment.
In 1995 N. kessleri was restricted to macrohabitats most frequently connected to the Danube. In 2000 the species was found nearly everywhere. N. gymnotrachelus was absent in 1995, but in 2000 it was only missing in macrohabitats most distant from the nearest inflow section. Data suggest that N. kessleri uses mainly the inshore zone, whereas N. gymnotrachelus was also found off-shore, where it replaced the ruffe (Gymnocephalus cernua) as the most abundant species.
Further trends in habitat expansion of ponto-caspian gobiids and their potential impact on the ecosystem will be discussed.