Flow-through raceways are the most common production system for rainbow trout. Welfare in these systems is affected by stocking density, water quality, and feeding management.
Rainbow trout welfare in flow-through raceways involves chronic stressors from high stocking density, the absence of environmental complexity, and social competition for optimal flow positions. High-density conditions cause fin damage from aggression, suppress immune function, and reduce the ability to perform natural behaviors. Water quality management through appropriate stocking density, feeding management to prevent waste accumulation, and disease monitoring are foundational welfare requirements. Raceway design that provides hydraulic complexity — variable flow speeds and depth gradients — gives trout more behavioral options than completely uniform raceways. Feeding system management to ensure all fish receive adequate nutrition reduces competitive stress between dominant and subordinate individuals.