Fish anaesthesia is used in research and aquaculture to reduce stress during handling, sampling, and surgery, with welfare implications for both the quality of anaesthesia and the fish's recovery.
Fish anaesthesia serves important welfare functions by reducing acute stress during necessary handling, sampling, and surgical procedures. However, anaesthesia itself carries welfare costs including the aversive experience of induction, which fish actively avoid at sub-anaesthetic concentrations, and the physiological stress of recovery. The choice of anaesthetic agent, concentration, and exposure time significantly affects both induction quality and recovery welfare. Over-anaesthesia causes prolonged recovery and potential mortality; under-anaesthesia allows stress responses during procedures. The welfare of fish during anaesthesia requires the same attention to agent selection, dosing, monitoring, and recovery quality that anaesthesia of other vertebrates receives. As fish are increasingly recognised as sentient, the standards applied to their anaesthesia in both research and aquaculture are appropriately rising to match those established for mammals and birds.