Trying to choose the less bad route: Individual migratory behaviour of Atlantic salmon smolts (Salmo salar L.) approaching a bifurcation between a hydropower station and a navigation canal

Contrary to small- and medium-sized rivers, little attention has been paid the downstream migration of Atlantic salmon smolts in large-sized rivers size-related impact hydropower stations. From 2014 2016, we investigated n = 72 acoustic-tagged Meuse river at a bifurcation zone between station equipped with three Kaplan turbines navigation canal. A hydrodynamic model that solves depth-integrated shallow water equations on Cartesian grid using finite volume technique was used infer influence discharge flow velocity smolts' behaviour upstream hydroelectric complex. Of migrating smolts, 41.5% performed back forth movements before approaching complex for first time, sometimes over long distances slow pace, leading significant delays (3–298 h). Beyond about 250 m3 s?1, direction changes towards gradual acceleration. median 161 s?1 associated 0.14 m tended favour more direct movement station. On other hand, canal mainly approached low (median 132 s?1), due higher 0.11 s?1) entrance. released only 38.6% passed through complex, which 36.4% migrated by 63.6% station, research time 04:44. Among all individuals, escapement rate end study site 2.9% 8.3% river. This site, offers two non-optimal, unattractive unsafe routes, turns out be problematic successful smolt migration.