Aquaculture

Farmed Salmon Gill Health

Gill health is one of the most significant welfare challenges in Atlantic salmon aquaculture, with multiple pathogens and environmental stressors causing chronic respiratory compromise in large numbers of fish.

Key Facts

Gill disease is responsible for the majority of salmon mortality on Norwegian farms
Amoebic gill disease (AGD) caused by Neoparamoeba perurans affects the majority of sea-water-phase salmon
Freshwater bath treatments for AGD are effective but impose significant acute stress
Genetic selection for gill health and improved pen design both reduce disease prevalence

Welfare Considerations

Salmon with compromised gills experience chronic respiratory distress equivalent to breathing through clogged airways. Reduced oxygen uptake causes lethargy, reduced feeding and vulnerability to secondary infection. AGD treatment with freshwater baths involves crowding fish, pumping them through a tube, holding them in freshwater for 20-60 minutes, and returning them to sea water — a stressful procedure often required multiple times per production cycle.

What You Can Do

Choose salmon from producers with published gill health monitoring data
Support research into non-stressful AGD treatment alternatives
Advocate for stocking density reductions that reduce gill disease transmission
Back genetic selection programmes for disease-resistant salmon strains