Atlantic salmon are facing extinction in many rivers due to barriers to migration, water temperature, disease, and reduced prey at sea. Restoring rivers improves welfare of salmon and river ecosystems.
Salmon blocked from reaching spawning grounds by barriers, weirs, and culverts experience frustrated migration instinct and eventual death without reproduction. Predation risk increases at barriers where fish congregate. Water temperatures above 20 degrees Celsius cause heat stress and disease susceptibility in salmon adapted to cold rivers. Pollution reduces river oxygenation needed for salmonid health. Sea lice from fish farms colonise migrating smolts, weakening them before they even reach the sea.