Fish ladder effectiveness for migrating species varies significantly with design, and poorly designed structures cause welfare harm through exhaustion.
Fish attempting to pass poorly designed fish ladders make repeated failed ascent attempts causing exhaustion and physiological stress. Fish in compromised condition have reduced survival whether they eventually pass or turn back. Modern fish ladder designs with appropriate step heights, attraction flows, and resting pools achieve substantially higher passage rates with lower energy cost. Dam removal remains the most welfare-positive solution where feasible.