Rainbow trout are among the most studied farmed fish species for welfare. Research on trout pain response, stress, and slaughter methods has generated welfare guidelines that are informing broader aquaculture standards.
Rainbow trout occupy a special place in animal welfare science because they were the species used in landmark research that shifted scientific consensus on fish pain. The trout data showing morphine-reversible anomalous behavior after painful stimuli was influential in convincing the scientific community that fish pain involves more than reflexive nociception. This welfare science has translated into concrete regulatory improvements in Norway and increasing adoption of pre-slaughter stunning globally. Trout represent a welfare success story in the making: a species where the welfare evidence is strong, the interventions are technically available and affordable, and regulatory uptake is occurring. This trajectory provides a model for broader aquaculture welfare improvement.