Rainbow trout are among the most widely farmed freshwater fish globally, and growing welfare science is informing standards for stocking density, water quality, handling, and humane slaughter in trout production.
Trout welfare science has advanced substantially over the past decade, providing clear evidence that intensively farmed trout experience stress responses, nociception, and behavioural indicators of positive and negative welfare states. Stocking density is one of the most tractable welfare variables: lower densities reduce aggression, fin damage, and disease transmission while improving individual fish quality of life. Water temperature management is critical for a cold-water species: temperatures above 18-20°C cause chronic thermal stress and immune suppression. The welfare gap at slaughter — between the best available methods (stunning followed by spiking) and common industry practice (CO2 immersion or live chilling) — represents an area where targeted welfare standards could produce rapid, measurable improvement. Consumer demand for welfare-certified trout products is growing, creating market incentives for producers to invest in welfare improvements across the production cycle.