Farmed Salmon Infectious Diseases

Infectious diseases are the leading welfare and economic challenge in salmon aquaculture — affecting millions of fish and requiring careful management to prevent suffering at scale.

Key Facts

Atlantic salmon in aquaculture are susceptible to a wide range of bacterial, viral, and parasitic diseases due to high stocking densities
Pancreas disease (PD), caused by Salmonid alphavirus, is among the most economically damaging diseases — causing gut damage, cardiac inflammation, and muscle necrosis
Infectious salmon anaemia (ISA) is a notifiable disease that has caused major culling events, including outbreaks destroying entire farm cohorts
Bacterial diseases including furunculosis (Aeromonas salmonicida) and piscirickettsiosis cause significant mortality in Chilean and Norwegian farms
Vaccination has dramatically reduced antibiotic use in Norwegian salmon farming since the 1990s — a major welfare and public health success story
Infectious diseases cause pain responses in fish including reduced feeding, altered swimming behaviour, and physiological stress indicators
Disease outbreaks may require emergency depopulation — the welfare of slaughter methods used in emergencies is often suboptimal

Welfare Considerations

Disease in farmed salmon causes welfare harms through both the direct effects of pathogens — inflammation, tissue damage, loss of appetite, impaired gill function — and through the management responses they necessitate. Emergency culling of diseased fish often occurs under conditions that prioritise speed over welfare. The stress of disease is compounded by the crowded environments in which farmed salmon live, where sick fish cannot withdraw from social interactions or find refuge. Preventing disease through better biosecurity, vaccination programmes, lower stocking densities, and site rotation is therefore both a welfare and a productivity imperative.

What You Can Do

Choose salmon certified by the ASC (Aquaculture Stewardship Council) which includes disease management and welfare requirements
Support investment in salmon vaccine development and biosecurity research through consumer choices that reward certified products
Advocate for stocking density limits in salmon aquaculture regulation — lower density reduces disease transmission and stress
Support salmon farming reform campaigns run by organisations such as CIWF, Feedback, and the Global Animal Partnership
Reduce farmed salmon consumption or substitute with lower-impact seafood options when welfare-certified products are unavailable
Lobby government to mandate welfare outcome monitoring in salmon farms, including disease prevalence and mortality reporting
Support closed containment aquaculture technologies that reduce disease pressure by separating fish from wild pathogens