Dams block fish migration routes that have existed for millions of years, causing population crashes in salmon, eel, shad, and other migratory species.
Fish impeded by dams experience extreme physiological stress, exhaustion, and injury. Turbine mortality affects fish passing through dam intakes, causing traumatic injury and death. Stranded fish in warming, oxygen-depleted reservoirs behind dams face slow deaths. The interruption of ancient migration instincts in animals with strong homing behavior represents a profound welfare harm at population scale.