Farmed Salmon in Recirculating Aquaculture Systems: Welfare Challenges

Recirculating aquaculture systems (RAS) offer environmental benefits but present unique welfare challenges for farmed Atlantic salmon, including water quality management and behavioral restriction.

Key Facts

RAS recycles up to 99% of water, reducing environmental discharge
Atlantic salmon in RAS are raised at densities of 50-80 kg per cubic meter
Ammonia and carbon dioxide buildup in RAS can cause gill damage and stress
RAS salmon cannot perform natural migratory or current-swimming behaviors
Water quality fluctuations in RAS cause acute stress responses in salmon
RAS operations are growing in Norway, Canada, and the United States

Welfare Considerations

RAS environments eliminate sea lice and reduce antibiotic use, representing improvements over net pen farming. However, constant recirculation, artificial lighting cycles, and high densities create chronic stress. Salmon are highly motivated to swim against currents, and the absence of this behavior in still RAS water may constitute a welfare deprivation. Carbon dioxide narcosis used in RAS slaughter requires careful monitoring. Research into optimal RAS parameters for salmon welfare is still developing.

What You Can Do

Support research organizations advancing welfare standards for RAS salmon farming
Choose salmon certified under schemes that include welfare auditing, not just environmental credentials
Ask retailers whether their RAS salmon suppliers use welfare outcome monitoring
Advocate for mandatory water quality and stress biomarker reporting in RAS salmon operations