Scientific understanding of fish cognition has advanced dramatically, demonstrating learning, social intelligence, and pain responses that demand welfare consideration.
Fish were long assumed to lack the neurological complexity for pain experience, but this assumption has been overturned. Fish have nociceptors, produce endogenous opioids, show protective behaviours after injury, and respond to analgesics in ways consistent with pain relief. Their cognitive abilities including tool use, social recognition, and learning rival many mammals. Welfare standards must be updated to reflect this evidence.