They don't work for many species. For example, one study found that 3% of American shad were able to use a fish ladder. https://e360.yale.edu/features/blocked_m

They don't work for many species. For example, one study found that 3% of American shad were able to use a fish ladder. https://e360.yale.edu/features/blocked_migration_fish_ladders_on_us_dams_are_not_effective https://e360.yale.edu/features/blocked_migration_fish_ladder... Fish ladders are akin to greenwashing.