Rainbow trout are the most commonly farmed freshwater fish in Europe, and their welfare needs in intensive aquaculture systems have received growing scientific attention.
Farmed trout welfare has been studied more thoroughly than most aquaculture species, providing a clear evidence base for improvement. Chronic crowding stress depresses immune function and increases susceptibility to disease. Aggression in high-density groups causes fin damage and eye injuries that persist throughout the production cycle. Water quality parameters - oxygen, temperature, nitrogen waste - directly affect moment-to-moment welfare. Slaughter welfare varies significantly: CO2 stunning causes distress before loss of consciousness, while percussive stunning provides more rapid insensibility. Reducing stocking density, improving water quality monitoring, and transitioning to percussive slaughter represent the most impactful near-term welfare improvements.