Rainbow trout are among the most widely farmed fish globally, with welfare concerns around stocking density, handling stress, and slaughter methods that affect millions of individual animals.
Rainbow trout welfare has received more scientific attention than many aquaculture species, establishing a clearer evidence base for welfare standards. Trout show pain responses, stress behaviors, and preference-based behavioral indicators that support sentience claims. Welfare improvements center on reducing stocking density, minimizing handling stress during grading and harvesting, and ensuring effective pre-slaughter stunning. CO2 narcosis, while widely used, is associated with aversive behavior suggesting it is not the welfare-neutral method it was once believed to be. Welfare certification programs are beginning to drive adoption of better practices in this important species.