Wild salmon undertake extraordinary spawning migrations, but dams and other obstacles block passage and cause significant welfare harm. Restoration programs are improving outcomes.
Wild salmon face welfare challenges during spawning migrations from blocked passage, temperature stress, and exhaustion. Fish ladders allow passage but are energetically costly and sometimes impassable for weaker fish. Fish that cannot pass barriers may linger at dam bases for weeks before dying without spawning — a welfare harm compounded by failure to complete their biological purpose. Dam removal — the most complete welfare solution — has shown spectacular results on rivers like the Elwha in Washington State. Climate-warming rivers cause thermal stress that kills salmon before they complete migration, a growing welfare concern.