Rainbow trout are one of the most widely farmed fish in temperate regions. Their welfare depends on stocking density management, disease control, and water quality throughout production.
Trout welfare is closely tied to water quality and temperature management. As metabolic rates increase in warmer water, oxygen requirements rise while disease resistance falls -- summer heat events create acute welfare challenges for farmed trout. Crowding beyond welfare-optimal densities increases fin damage, feeding competition, and disease transmission. Grading operations that remove fish from water cause acute stress and scale damage. Best welfare practice minimizes out-of-water handling time, uses well-oxygenated water during any necessary crowding, and maintains temperatures within the species' thermal comfort zone. Pre-slaughter stunning is increasingly standard in higher-welfare producers.