Wild Atlantic Salmon Welfare: Migration Barriers, Predation, and Sea Lice

Atlantic salmon face severe welfare challenges during their migration from freshwater nurseries to ocean feeding grounds and back. Human-caused barriers and sea lice from aquaculture compound natural stresses.

Key Facts

Atlantic salmon (Salmo salar) are anadromous — born in freshwater, maturing in ocean, returning to spawn
Global Atlantic salmon populations have declined by 75-80% over the past 40 years
Dams and weirs block migration routes; fish ladders restore passage but are not fully effective for all fish
Sea lice (Lepeophtheirus salmonis) from aquaculture farms infest wild salmon during coastal migration phases
Wild salmon lose up to 30% of their body weight during spawning migrations without feeding
River temperature increases from climate change cause thermal stress and mortality during upstream migration
Catch-and-release angling causes handling stress, air exposure, and exhaustion that can be lethal in warm water

Welfare Considerations

Wild salmon experience intense physical challenges across their life cycle that are substantially worsened by human modifications to freshwater and coastal ecosystems. Dams and weirs impose additional energetic costs and sometimes lethal barrier effects. Sea lice from salmon farms parasitise wild smolts during the critical early ocean entry phase, causing tissue damage, osmotic stress, and mortality in affected individuals. Climate-driven river warming is pushing thermal tolerance limits in summer migration months, causing both direct mortality and physiological stress that reduces spawning success. Each of these welfare compromises represents a human-caused addition to natural challenges that wild salmon already face. Conservation interventions with direct welfare benefits include dam removal, fish passage improvement, aquaculture sea lice management, and angling practice reform requiring cold-water wet-hand handling.

What You Can Do

Support dam removal and fish passage restoration projects in salmon river systems
Advocate for aquaculture sea lice management requirements that protect wild salmon during migration seasons
If angling for salmon, use barbless hooks, keep fish in water, and release quickly — avoid handling in warm water
Support organisations working on Atlantic salmon river restoration including riverine habitat improvement
Engage with climate policy that reduces temperature increases threatening salmon thermal limits