Rainbow trout is one of the most widely farmed freshwater fish globally. Welfare science is well-developed for this species, providing clear guidance on stocking density, handling, and slaughter that the industry is slowly adopting.
Rainbow trout welfare is better understood than most farmed fish species, thanks to decades of welfare research. High stocking densities cause chronic stress, fin damage, immunosuppression, and reduced growth in subordinate fish. Grading operations that sort fish by size reduce size-based aggression but cause acute mechanical stress and should use water-return systems that minimise air exposure. Slaughter welfare is the best-documented issue — live chilling without stunning causes prolonged consciousness during asphyxiation; percussive or electrical stunning prior to slaughter is both feasible and increasingly mandated by welfare certification bodies. The RSPCA Assured standard and GLOBALG.A.P. Aquaculture include trout-specific welfare criteria. Consumer preference for certified trout drives producer adoption of improved practices.