Tidal power turbines are developed to reach the ambition of supplying coastal communities with renewable energy. However, little is still known about the potential environmental effects on the local ecosystems and what rotor design can do to minimize such effects. The knowledge gap includes fish behavior around tidal power rotors and adequate sampling techniques for such studies. In this contribution stereo-video methodology has been used for monitoring fish movements at an operating model of a vertical-axis tidal turbine rotor. The results show that stereo-video methodology offers excellent opportunities for detailed analysis of fish behavior and several recommendations of how to optimize such sampling are provided. Preliminary results of fish-turbine interactions are presented.