Atlantic and Pacific salmon undertaking upstream spawning migrations face an increasingly hostile gauntlet of warm water, low flows, predators, and fishing pressure that affects their welfare and survival.
The spawning migration of salmon represents the culmination of a multi-year oceanic existence and is physiologically demanding even under ideal conditions. Warming rivers, reduced flows, and multiple fishing encounters combine to exhaust salmon before they complete their migration, causing deaths in the river rather than after spawning. Fish that die pre-spawning or that arrive at spawning grounds too physiologically depleted to successfully reproduce have experienced welfare failures that also have population-level consequences. River temperature management through riparian shade planting, abstraction limits, and emergency releases from reservoirs during critical periods represents one of the most cost-effective interventions for both salmon welfare and population recovery.