Farmed Animals

Farmed Salmon Recirculating Aquaculture System Welfare

Recirculating aquaculture systems (RAS) are increasingly used for salmon farming, offering controlled conditions but introducing new welfare challenges compared to sea cage farming.

Key Facts

RAS systems recycle up to 99% of water, maintaining precise control over temperature and dissolved oxygen
RAS eliminates sea lice infestation and reduces disease transmission from wild fish
High fish densities in RAS can still cause aggression, fin damage, and chronic stress
Water quality failures in RAS can cause rapid mass mortality due to the closed system
Gas supersaturation (too much dissolved oxygen or nitrogen) causes gas bubble disease in RAS salmon

Welfare Considerations

While RAS eliminates some sea cage welfare problems such as parasites and environmental pollution, it introduces others. Fish in RAS experience reduced environmental complexity, potentially higher stress from artificial light and noise, and risks from system failures. Rapid changes in water chemistry in closed systems can cause acute suffering. The welfare benefits of RAS depend heavily on operator skill, monitoring quality, and stocking density management.

What You Can Do

Support aquaculture certification schemes that include RAS-specific welfare standards
Encourage research into optimal stocking densities and environmental enrichment in RAS systems
Choose salmon from farms with independently audited welfare programmes
Advocate for regulatory standards requiring backup systems in RAS to prevent catastrophic failures