Rainbow trout are among the most farmed fish species globally; their welfare in aquaculture is affected by stocking density, water quality, and handling during harvesting and grading.
Rainbow trout welfare shares many characteristics with Atlantic salmon welfare but with species-specific differences that require separate management consideration. Trout are more territorial than salmon and show more intense aggression at high stocking densities, making density management particularly important. The grading of fish by size — a standard commercial practice — involves repetitive handling that causes scale loss and stress; minimising grading frequency reduces cumulative welfare harm. Water quality, temperature, and oxygen management all affect trout welfare in ways that are well understood but not always well managed in commercial operations. RSPCA Assured certification provides the most comprehensive UK welfare standard for farmed trout.