Rainbow trout is one of the most commonly farmed fish globally. Their welfare in net pen and flow-through tank systems is significantly affected by stocking density and water quality management.
Rainbow trout welfare in commercial aquaculture is affected at every stage of production. Egg and early juvenile stages require precise water quality management for developmental welfare. Juvenile density management affects growth and aggression through the grow-out period. Trout are more active and aggressive than some farmed species, making the behavioral consequences of crowding more acute. Research by Lynne Sneddon and others has established that trout have nociceptors, respond behaviorally to painful stimuli, and show long-term behavioral changes after painful experiences — providing evidence for welfare-relevant sentience. Slaughter welfare is highly variable — CO2 stunning is widely used but is aversive; electrical stunning and percussive stunning provide more humane alternatives now being adopted by welfare-conscious producers.