Freshwater Rainbow Trout Welfare in Recirculating Systems

Recirculating aquaculture systems (RAS) offer improved control over trout welfare but introduce new challenges compared to traditional flow-through systems.

Key Facts

RAS systems recirculate 95-99% of water, reducing disease introduction and environmental impact
Precise control of temperature, oxygen and CO2 allows optimisation for fish welfare
Failure of RAS mechanical systems can cause mass mortality within hours
Trout in RAS show different behavioural repertoires than flow-through fish due to different current regimes
RAS systems enable production inland away from rivers, reducing disease transmission to wild fish

Welfare Considerations

RAS trout welfare has advantages and specific challenges compared to flow-through systems. The precise environmental control possible in RAS can optimise welfare conditions when functioning correctly. However, total dependence on mechanical systems creates catastrophic failure risk unknown in natural water systems. Psychological welfare of trout in still RAS water compared to flowing systems requires research. The biosecurity advantages of RAS reduce disease transmission to wild fish, benefiting both farmed and wild fish welfare. Welfare optimisation in RAS requires species-specific research into flow, social density and environmental enrichment.

What You Can Do

Support research into RAS-specific trout welfare requirements and optimisation
Advocate for welfare monitoring and backup system requirements in RAS regulations
Choose trout from RAS operations with documented welfare management protocols
Engage with the expanding RAS industry about integrating welfare into design standards