Assessing pain in fish is scientifically challenging but increasingly important as fish welfare enters mainstream animal welfare discourse. New tools and frameworks are improving our ability to measure fish suffering.
Fish pain assessment has moved from a fringe academic question to a central welfare science priority as billions of fish are killed each year with minimal consideration for their welfare. The challenge is methodological: fish cannot vocalise or use the behavioural indicators that make pain assessment in mammals intuitive. However, the development of species-specific grimace scales, the validation of pharmacological pain relief in reducing fish behavioural indicators of nociception, and the identification of central nervous system structures capable of processing pain have collectively built a strong case that fish pain matters morally. Welfare assessment tools for fish are less developed than for mammals, but the research trajectory is clear. Slaughter protocols, anaesthesia for research procedures, and management practices in aquaculture are all areas where fish pain assessment tools can drive welfare improvement.