The use of anesthesia in fish during sampling, treatment, and research procedures is increasingly recognized as an ethical requirement, reflecting growing understanding of fish pain.
Fish anesthesia represents one of the clearest practical applications of fish welfare science. The evidence that fish experience stress and likely pain during unanesthetized handling is sufficiently strong that the default assumption should be that procedures causing stress in mammals require mitigation in fish as well. Anesthesia during blood sampling, weighing, vaccination, and surgical marking in aquaculture reduces both the welfare harm to individual fish and the physiological disruption that compromises immune function and health outcomes. The barrier to wider adoption in commercial aquaculture is cost and logistical complexity rather than technical feasibility — the tools exist and work well. Regulatory requirements and welfare certification standards that mandate anesthesia for defined procedures provide the most reliable mechanism for broad adoption across the industry.