This project evaluates optimization of connectivity measures at hydropower sites. To reach the national environmental goals, the industry needs efficient and cost-effective passage solutions. Passage solutions have traditionally been designed to maximize passability for especially fish, and have been evaluated by fish and benthos field surveys up- and downstream the implemented passage solutions. The present grant proposal will complement such traditional survey methods by introducing and developing genetic tools for evaluation of species richness (eDNA) and population genetics composition (RAD) over connectivity-reducing hydropower plants. Atlantic salmon (S. salar) started to diminish in the beginning of the 1990s and is considered to be especially threatened by the increase of temperatures, caused by climate change, and by the presence of numerous hydropower plants and dams, which represent an impediment for their migration. To increase accessibility, connectivity and make over 100 kilometers of high-quality river habitat available for both salmon, brown trout and a number of other organisms, the municipalities located along Rönne å have decided to remove the three lowest hydropower plants by 2025. We will analyze the genetic differences between the population up-stream and down-stream of these hydropower plants and among the different tributaries of the river. The data will serve as a comparison when the effect of the restoration is evaluated with focus on genetic diversity.