How fish welfare science has advanced over two decades and what remains to be understood.
The scientific transformation of fish welfare from dismissed concern to established field in two decades represents one of the most significant welfare science developments in history. The starting point — the dismissal of fish pain as scientifically implausible — gave way as methodologically rigorous research demonstrated nociception, avoidance learning, analgesic responses, and behavioral evidence consistent with pain and fear across multiple fish species. This scientific progress created the evidence base for regulatory change in the EU, Australia, and other jurisdictions, and drove the emergence of fish-specific welfare standards in aquaculture. The remaining scientific frontiers — particularly the question of conscious pain experience as opposed to nociceptive responses — will shape the long-term trajectory of fish welfare standards and the precautionary principle in fish management.