Wild salmon undergo extraordinary spawning migrations involving physical deterioration that raises questions about the nature of their suffering.
The death of Pacific salmon after spawning is a programmed biological process — the deterioration is genetically predetermined and may not involve suffering in the same sense as starvation. However, dam blockages cause suffering by frustrating the strongly motivated migration drive. Stranded salmon unable to reach spawning grounds face prolonged stress. Water temperature and pollution in degraded rivers cause thermal stress and disease. Restoration of river connectivity directly reduces salmon welfare harms.