Aim of the thesis is to assess and evaluate the habitat improvements at the Upper Drau River from a fish-ecological perspective and to highlight and discuss further existing deficits respectively. Data collection within the 60 km long section between the villages of Oberdrauburg and Molzbichl was carried out in November 2010. The overall situation of the fish stocks shows clear improvements compared to the year 2002, but worsened again compared to the last survey in 2006. Alternating flow conditions and therefore natural fluctuations leading to decreased reproduction success of the grayling (Thymallus thymallus) could be detected as the main cause for this development. All typical fish species of the Upper Drau River were found, but some species in very low numbers only (Danube salmon, nase, barbel). The populations of single small sized species, listed in the FFH-directive (e.g. souffia, lamprey), and also the populations of chub and minnow could be stabilized during the last years. The population structure of grayling and brown trout are still balanced but the biomasses are far below the values of the late 1980s. In total the fish stocks show a trend for slow recovery. The Danube salmon and the nase are about to disappear ultimately, which is a main threat for the ecosystem. Both species could be found in very low numbers only. Nevertheless 2010 was the first survey which could prove the “good status” for Drau River section upstream the village of Sachsenburg within the restored reaches. In contrast, the section downstream is in “bad status” due to very low fish biomasses. The river restoration measures contributed to clear improvements of the overall ecological situation. However, further improvement particularly concerning the problem of hydropeaking and the disrupted longitudinal continuum are imperative to reach and, further on, to stabilize the “good status” stipulated by the EU Water Framework Directive.