The present study was carried out in the HyTEC-facility in Lunz am See. The main issue of the project was to test the effects of hydropeaking on growth and condition development of juvenile grayling. The second part of this thesis dealt with habitat suitability of juvenile grayling at different life stages and habitat modelling in the channels at different flow rates. Growth and conditions development of juvenile grayling in the treatment and the reference channel were compared. As a result there was no negative influence on growth and condition development of juvenile grayling due to hydropeaking. In contrast, high rates of drift were detected in the treatment channel in both periods (37% in November 2012, 31% in February 2013 of total 250 individuals in each period). In the treatment channel 37% of total 250 graylings stranded due to hydropeaking in February 2013 and 9% in November 2012, while in the control channel there was none. The simulations in the experimental channel with varying water discharges showed the changing habitat suitability of different age classes. With raising discharge the habitat availability for the larval stage diminished. The suitability of the habitats depends strongly on flow velocity and water depth. For juvenile grayling the suitable habitat was at its biggest during summer but with raising discharge it declined as well. In contrast, during autumn the habitat for juvenile grayling enlarged with increasing discharge. With respect to the habitat suitability analyses for different age classes of grayling, results of the hydropeaking experiment can be interpreted more specific. For a comprehensive assessment of the ecological impact of hydropeaking further research is needed.