Wild Atlantic and Pacific salmon undertake extraordinary migrations with significant welfare implications from both natural stressors and human-caused impacts on rivers and oceans.
Wild salmon welfare is shaped by the extraordinary energetic demands of their life history. The ocean-to-river spawning migration involves weeks or months without feeding while swimming thousands of kilometres against current, over waterfalls, and through temperature extremes. Dams that prevent passage cause salmon to die attempting to pass impassable barriers -- a direct welfare harm in addition to the population collapse that results. Elevated river temperatures cause heat stress and thermal mortality in animals already physiologically compromised by their migration. Climate change and dam infrastructure represent the two most pressing welfare threats to wild salmon, alongside the sea lice spillover from coastal salmon farms.