Atlantic salmon undergo extraordinary physiological transformation during their upstream spawning migration, facing multiple natural and human-made welfare challenges.
The upstream migration of Atlantic salmon is one of nature's most extraordinary journeys, but it involves significant physiological stress and welfare challenges. Salmon cease feeding on entering freshwater, using only body reserves - accumulated over years at sea - to fuel the migration. This places enormous physiological demands on the fish, making any additional stressors particularly damaging. Human barriers including weirs, dams, and hydroelectric structures can physically injure fish attempting to pass, cause exhaustion through repeated failed jumping attempts, and block migration entirely where fish passes are absent or ineffective. Elevated water temperatures from climate change are causing mortality events in spawning rivers, as salmon cannot regulate their body temperature and heat stress causes physiological failure. Angling for wild salmon, even with catch-and-release practices, causes acute stress that can impair spawning success. Conservation and welfare overlap strongly in salmon: improving fish passage, reducing water temperature, and minimising fishing pressure all benefit both population survival and individual animal welfare.