Moving beyond harm reduction to positive welfare states for rainbow trout in aquaculture through environmental enrichment and management.
Rainbow trout welfare science has advanced beyond simply minimizing harmful conditions to identifying and promoting positive welfare states. Research has demonstrated that trout show individual behavioral differences, form preferences about their environment, and express exploratory and play-like behaviors when conditions allow. Positive welfare in trout aquaculture involves providing environmental complexity that permits natural behavior expression: varying current patterns that allow trout to exercise rheotaxis, substrate that allows resting behavior, and appropriate social density that enables shoaling without crowding stress. The growing body of trout welfare science challenges the view of fish as welfare-irrelevant production units and supports a positive welfare framework where the goal is flourishing rather than mere survival. Certification schemes are beginning to incorporate positive welfare indicators alongside harm reduction measures.