Rainbow trout are the most widely farmed salmonid globally. Evidence-based welfare improvements in stocking density, water quality, enrichment, and slaughter are achievable within current production systems.
Rainbow trout welfare improvements are scientifically well-supported and technically achievable. Reducing stocking density below 25 kg/m³ reduces fin damage, aggression, and cortisol levels — welfare benefits that are often accompanied by improved growth rates, aligning welfare and productivity. Maintaining dissolved oxygen above 7 mg/L and minimising temperature fluctuations reduces physiological stress across the production cycle. Environmental enrichment for trout — current variability, substrate patches, and refuge structures — remains an underexplored area but shows promise in reducing stereotypic circular swimming and improving exploratory behaviour. Handling during grading and transfer causes acute stress; minimising frequency and duration of out-of-water exposure is important. Slaughter by live chilling alone is the most common but least humane method; percussion or electrical stunning immediately before killing is a significant welfare advance being adopted by certified producers.