Rainbow trout farming in recirculating aquaculture systems (RAS) is expanding rapidly. Understanding how these intensive indoor systems affect trout welfare informs better design and management standards.
Recirculating aquaculture systems offer genuine environmental advantages but present distinct welfare challenges for trout. The controlled indoor environment allows precise water quality management but creates a sensory monotony — constant temperature, flow rate, and lighting — that bears no relationship to the varied river and lake environments trout evolved in. High stocking densities create competitive stress, physical damage from fin-nipping, and chronic physiological stress that compromises immune function and growth. The welfare trajectory for RAS trout farming is improving: enrichment research, stocking density guidance, and slaughter welfare standards are all advancing. But implementation of best practice across commercial systems remains inconsistent, and the gap between welfare science and industry standard is substantial.