Rainbow trout is one of the most widely farmed salmonid species globally, with an established welfare science base that can guide improvements in farming practice.
Rainbow trout welfare is relatively well-studied compared to many other farmed fish species, providing a solid evidence base for welfare-positive management. Their cold-water requirements mean that temperature management is a primary welfare consideration, with warm summer temperatures in uncontrolled systems causing heat stress. Crowding produces territorial aggression leading to fin damage, an easily observed welfare indicator that serves as a proxy for density-related stress. The variation in individual growth rates creates a challenge: in high-density systems, dominant individuals grow faster and subordinates are progressively disadvantaged in feed access, creating within-tank welfare inequality. Sorting fish by size reduces this inequality. Humane slaughter standards for trout are among the most developed in aquaculture, reflecting the longer history of welfare attention to salmonid species.