Farmed Salmon Gill Health and Welfare

Gill disease is one of the most significant welfare challenges in Atlantic salmon farming, causing respiratory distress and chronic discomfort across large populations.

Key Facts

Amoebic gill disease caused by Neoparamoeba perurans is a major production and welfare problem
Affected salmon show increased ventilation rate, surface swimming, and reduced feed intake
Freshwater treatments are effective for AGD but cause handling and osmotic stress
Complex gill disease with multiple causative agents is increasingly common in Norwegian farms
Gill health monitoring through score assessment provides early detection that reduces welfare burden

Welfare Considerations

Gill disease in farmed salmon causes chronic respiratory distress that is invisible to consumers but measurable in affected fish behaviour. Salmon with AGD swim more slowly, avoid depth, and show increased ventilation effort as they struggle to extract sufficient oxygen through damaged gill tissue. The welfare burden is significant and prolonged — weeks between treatment events during which fish experience ongoing respiratory compromise. Freshwater treatments that kill the causative amoeba are effective but impose the acute stress of transfer and osmotic challenge. Managing this welfare trade-off requires investment in early detection through gill scoring, lower stocking densities that reduce disease pressure, and farm siting that reduces amoeba exposure risk.

What You Can Do

Choose salmon certified to welfare schemes with gill health monitoring requirements
Support research into salmon gill health management that reduces both disease burden and treatment stress
Advocate for gill disease monitoring to be reported as a welfare indicator in aquaculture standards
Ask salmon retailers about their supplier farms gill health management protocols