Effectiveness of an Electrical Barrier to Improve Silver Eel (ABSTRACT

The European eel population is in severe decline, leading to several regulations to save the species from extinction. Various factors impact various stages of the complex lifecycle of this species, and improving the survival of silver eels migrating downstream through turbines is essential in hydropower plants (HPPs). While adapted physical barriers ensure total protection in new small HPPs, effective solutions are still needed for larger existing facilities. An electrical barrier was installed across the forebay of 160 m3 s−1 HPP. An acoustic telemetry study compared silver eel passage via the dam versus the turbines between reference values in the year prior to the installation of the barrier versus migration after installation and operation of the electrical barrier. The dam passage rate increased significantly with the electrical barrier, in hydrological conditions similar to those of the reference year. Under flow conditions where the nonturbine flow was the lowest, a reduction of 52% in turbine passage could be explained by the electrical barrier. While this efficacy is far from perfect, the results encourage using this technology in large HPPs as a first step in eel protection. At our pilot study site, the technology was adopted as a permanent solution, associated with turbine shutdown according to an eel migration prediction model.