Rainbow trout are one of the most extensively studied farmed fish for welfare purposes. Research on their pain responses and behavioral needs is helping transform farming practices.
Rainbow trout are a model species for fish welfare science. Studies have demonstrated that they respond to harmful stimuli in ways consistent with pain experience, show conditioned avoidance, and have their normal behavior disrupted after painful experiences. In commercial settings, the chronic stress of high stocking densities suppresses immune function and increases disease susceptibility. Fin erosion affects the majority of fish in intensive systems, representing both a welfare problem and an indicator of poor overall conditions. Sea lice infestations cause tissue damage that fish respond to through increased scratching behavior and attempts to remove the parasites. The science of trout welfare has advanced significantly but operational implementation in commercial farms remains inconsistent.