Turbot is a premium European flatfish farmed in Spain, France, and China. Its welfare in intensive tank systems raises questions about stocking density, water quality, and slaughter methods for a high-value, welfare-understudied species.
Turbot welfare in RAS systems is shaped by the species' benthic lifestyle and sensitivity to environmental conditions. As flatfish, turbot rest and move along tank bottoms — high stocking densities that would be less problematic for round fish create genuine crowding for fish competing for bottom space. Stacking behaviour at very high densities — where fish rest on top of each other — limits access to oxygenated water at the boundary layer, causing hypoxic stress. The long grow-out period (2–3 years) means that any ongoing welfare deficit — from water quality problems, disease, or inadequate space — compounds over an extended timeline. The premium market position of turbot creates alignment between quality and welfare: stressed, injured fish produce poorer quality flesh, incentivising producers to maintain welfare conditions. Electrical stunning before slaughter, increasingly adopted in Spanish production, provides rapid insensibilisation and is the welfare-positive standard for this species.