Rainbow trout are one of the most commonly farmed fish in Europe and North America. Their welfare is increasingly well-studied, making them a model species for aquaculture welfare improvement.
Rainbow trout are at the forefront of farmed fish welfare partly because extensive research has validated their sentience and mapped their welfare needs clearly. Stocking density management is central: research shows welfare deteriorates significantly above recommended densities through stress, injury from social aggression, and reduced access to food. Pre-slaughter stunning — both for welfare and product quality — is increasingly standard among higher-welfare producers and required by certification schemes. The individual personality variation documented in trout has implications for how group management affects individual animals: bold fish outcompete shy fish for food at high densities, and shy fish show chronic stress in inadequate environments. Rainbow trout welfare is a model for how fish welfare can be taken seriously in commercial production.