Rainbow trout (Oncorhynchus mykiss) is among the most studied farmed fish species for welfare, with research informing stocking density standards, slaughter methods, and environmental management across temperate aquaculture systems.
Rainbow trout welfare science is among the most developed for any farmed fish species, providing a relatively strong evidence base for management standards. Research has established trout pain physiology, stress responses, and welfare-relevant behavioral indicators including cognitive bias testing. The gap between evidence and practice remains significant: stocking densities in commercial trout farms routinely exceed welfare-recommended levels because the productivity-welfare trade-off is resolved in favor of productivity without regulatory compulsion. Slaughter welfare has improved in some regions through industry adoption of electrical stunning, but live chilling persists. The trout welfare evidence base creates both an opportunity and a responsibility: there is sufficient knowledge to implement meaningful improvement, making continued poor practice a choice rather than a knowledge gap.