Rainbow trout are among the most commonly farmed fish globally with welfare challenges specific to salmonid species.
Trout welfare in intensive systems is affected by crowding, water quality, and nutritional deficiencies. Cataracts reduce visual acuity needed for predator detection and social interaction. Stress from crowding causes cortisol elevation that suppresses immune function. The welfare and production cases for better water management and optimal nutrition align — stressed fish grow more slowly and are more disease-susceptible.