Abstract
Optimising the design of passage facilities to restore fluvial connectivity for juvenile European eel (Anguilla anguilla) is a key priority within conservation efforts for the species, across the majority of its freshwater range. Employing an experimental setup that simulated gravity-fed upstream eel passes, this study demonstrated that novel V-profile passes, which incorporate two lateral slopes (15°), performed better than laterally flat passes over the flow rates tested (0.2–0.6 L s−1). For the small eel size used (60–80 mm length), the bristle substrate consistently outperformed studs, but the lateral slope had a greater effect on passage metrics than the substrate choice. Our findings strongly support the use of V-shaped channels for upstream migrating eel at fish passage facilities, particularly in scenarios where flow rates may be elevated and/or fluctuating, such as for gravity-fed passes.