Author(s): Simon Fuhrer; Daniel S. Hayes; Daniel Mameri; Elora Fauchery; Thomas Hasler; David Graf; Stefan Schmutz Stefan Auer
Linked Author(s): Daniel Hayes
Keywords: No keywords
Abstract: Artificial sub-daily flow fluctuations during hydropeaking are considered one of the most significant impacts on rivers downstream of dams. They have, therefore, been subject to a growing number of studies in the last decades. Nevertheless, so far, cyprinid fish have hardly been considered worldwide and extensive knowledge gaps remain. Therefore, this study aims to assess the effect of rapid flow reductions on early life stages of common nase (Chondrostoma nasus L.) in an experimental approach. Different hydropeaking scenarios were simulated at an outdoor experimental facility (http: //hydropeaking. boku. ac. at) using mesocosms (2.25×2 m) mimicking typical larvae habitats to quantify stranding of young-of-the-year nase. Experiments were performed during day and night. At each replicate, 100 fish (body length <20 mm) were stocked at peak flow (80 L. s-1). After an adaption time (15 min.), the discharge was automatically reduced – with variable ramping rates – until constant low flow conditions (10 L. s-1) were reached and stranded fish were recorded. Our analyses show a distinct difference in stranding risk between day and night experiments. Further, the data indicates differences between tested down-ramping rates and interaction effects between time of day and down-ramping rate. The study outcome will benefit the ongoing discussion on hydropeaking mitigation by providing a more profound knowledge of the direct effects of artificial sub-daily flow fluctuations on the early life stages of cyprinid fish.