Pacific salmon migration runs involve extreme physiological effort, progressive body deterioration, and mass post-spawning death that represent significant individual welfare costs built into the species reproductive biology.
Salmon migration welfare is complex because much of the deterioration is species-typical and evolutionary — the post-spawning death of Pacific salmon is not a welfare failure but a programmed life history strategy. Human impacts that worsen migration conditions — dams that create obstacles requiring repeated attempts, pollution that weakens migrating fish, and poaching that intercepts already-stressed individuals — add welfare costs to an already demanding biological process. Dam removal and pollution reduction address the human-amplified welfare costs while the inherent biological costs remain.