Author(s): Anita Moldenhauer-Roth; Gabor Suss; Luiz G. M. Silva; Celine Moeckli; Nicolas Diserens; Ismail Albayrak; Robert M. Boes

Linked Author(s): Luiz G Martins da Silva, Ismail Albayrak

Keywords: Longitudinal connectivity; Downstream fish passage; Electrified bar racks; Electric fields; Risk of fish injuries

Abstract: Run-of-river hydropower plants disrupt the longitudinal connectivity of rivers, hindering or delaying fish downstream movement. Electrified bar racks are a promising alternative or complement to physical and mechanical-behavioural bar rack bypass systems for preventing fish from entering turbines and potentially guiding them towards an alternative passageway. Electrification of existing intake racks may reduce fish turbine passages and allow them to search for an alternative passageway. Avoidance responses and thus fish protection efficiencies of electrified racks vary depending on fish species, electric field strength, electrode placement, and electrical parameters such as pulse type, duration and frequency. This study investigates electrified intake racks, which have shown promising fish protection efficiencies in laboratory tests, for possible injury risks to enable the implementation of pilot projects. Two intake rack configurations with bar spacings of 50 and 90 mm, were tested with two different electrode placements and electrified with either pulsed direct current or pulsed alternating current. Two types of fish interaction with each rack configuration were evaluated: 1) passage through the rack and 2) prevention from passage i.e. interaction with the electric field upstream of the rack. Hatchery-reared brown trout, ranging in total length from 178 to 323 mm (median

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.226

Year: 2026