The small adipose fin behind the dorsal fin in salmon and trout has welfare significance in aquaculture — its removal is used for stock identification, raising questions about pain, regeneration, and the ethics of routine surgical procedures in fish.
Fin clipping inflicts brief but real pain in fish, and the scale of the practice — hundreds of millions of individuals — makes its cumulative welfare impact substantial even if individual suffering is short-lived. Evidence that salmon respond to painful stimuli with lasting behavioural changes challenges historical dismissals of fish pain. The welfare justification for adipose fin removal rests on fisheries management benefits, but alternatives including genetic marking, otolith marking, and electronic tagging should be developed and adopted where feasible. Aquaculture operations that minimise routine painful procedures and use anaesthesia where unavoidable demonstrate higher welfare standards.