Rainbow trout is the most widely farmed salmonid after Atlantic salmon. Disease prevention and management are central welfare challenges in trout aquaculture, with vaccination and biosecurity transforming production outcomes.
Trout welfare in aquaculture has improved significantly in markets where vaccination programs have reduced disease burdens and antibiotic treatment requirements. Chronic disease — whether bacterial, viral, or parasitic — is among the most significant welfare harms in aquaculture: fish with active infections experience pain, respiratory compromise, and behavioral disruption over extended periods. Prevention through vaccination, biosecurity, and stocking density management is both the most welfare-effective and increasingly the most economically rational approach, as antibiotic resistance concerns have elevated the cost of treatment-focused disease management. Slaughter welfare remains inconsistent: electrical stunning is effective and increasingly adopted by certified producers, but ice slurry and CO2 immersion remain common in non-certified facilities and cause significant pre-slaughter distress.