Author(s): Kamal Prasad Pandey; Ismail Albayrak; Armin Peter; Torbjorn Forseth; Eric Lillberg; David Florian Vetsch; Mikaela Larsson; Robert Michael Boes; Ana Teixeira Silva

Linked Author(s): Ismail Albayrak

Keywords: Downstream fish migration; Fish passage; Behavioural guidance structure; Guidance efficiency

Abstract: In the scope of the FishPath project, we investigated the behavioral responses of Atlantic salmon smolts (Salmo salar) to horizontal, vertical, and streamwise turbulent eddies generated by three experimental structures in a small-scale laboratory flume. Insights from these tests, combined with hydraulic data, guided the design of several geometrical configurations of a novel turbulent eddy-based fish guidance system (EGS), which were tested attached to a bypass system. These configurations were tested with salmon smolts in a large- scale ethohydraulic flume at VAW, ETH Zurich. The EGS consisted of streamwise eddy generators attached to vertical plates (elements) with three different lateral spacings in the streamwise direction ranging from 100 to 200 mm . Two horizontal angles of the EGS relative to the approach flow direction, within the range of 15° to 45°, were tested result ing in six different EGS configurations. At an approach flow velocity of 0.60 m s−1 and bypass inlet flow velocity of 0.72 m s−1 (velocity ratio =1.2), all EGS configurations produced streamwise vortices whose wake interactions varied with angle and spacing, influencing the behavioral response of fish. The EGS angle strongly influenced the fish guidance efficiency, yielding lower values of 44-66% for the smaller angle and higher efficiencies up to 73-97% for larger angle. The highest efficiency was observed for larger angles with intermediate spacing. This optimal configuration was selected for subsequent semi-natural large-scale testing at the Vattenfall AB laboratory, Sweden, with salmon smolts. The EGS demonstrates strong potential as an effective downstream fish guidance and protection system for hydropower and water intake facilities, exhibiting high protection and guidance efficiencies.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.188

Year: 2026