Freudenau is the latest constructed Hydropower plant (HPP) on the Austrian Danube located in Vienna. Within the framework of the HPP construction, a fish ecological preservation of evidence took place in 1993/1994 in the surrounding Danube main channel affected by the HPP between river kilometres 1945.5 1917. Thereby, as well as for the followed-up fish ecological investigations in 1999/2000 and in 2014 inter alia standardized longlines baited with Eisenia fetida were fished focusing on benthic fish species. By comparing the catches of these longlines fishing investigations via CPUE (catch per unit effort), we attempt to assess temporal and spatial changes in the benthic fish biocoenosis related to the construction and operation of the HPP. Therefore, the investigation area was subdivided into sections according to the direct influence of the HPP on this Danube stretch into Head of Impoundment, Transition Zone, Central Impoundment and Tailwater. By using the, CPUE, count of caught fish species, species classification referring to habitat requirements by Jungwirth (2003) and Zauner & Eberstaller (1999 & 2003) and changes of the benthic fish biocoenosis in individual sections across the three investigation periods impacts on the altered fish habitats by the HPP could be analysed. Clear changes in benthic fish species abundance and occurrence could be observed and could be linked to the changed habitat after impounding the river. Thus, a trend in the benthic fish biocoenosis from a rheophilic assemblage to a more indifferent one could be observed. Further, CPUE-values of most native fish species clearly declined with in the investigation periods while invasive Gobiidae species, which immigrated in the 90s became the most abundant benthic fish species in the investigation area. While strongest altered sections like the Central Impoundment and the Transition Zone seem to be suitable habitats for this invasive species, most native species show only low CPUE-values.