The science of fish pain has advanced dramatically in recent decades. Understanding what the evidence now shows is essential context for fish welfare policy and practice.
The evidence that fish experience pain has moved from fringe hypothesis to mainstream scientific view. Multiple lines of evidence — anatomical, pharmacological, and behavioral — support the conclusion that fish experience noxious stimuli as harmful and that this experience motivates avoidance behavior in ways analogous to pain in mammals. Whether fish experience pain with the same subjective quality as human pain remains philosophically uncertain, but the welfare precautionary principle argues strongly for acting as if they do. This has major implications for aquaculture, recreational fishing, and research: practices that would be unacceptable for mammals should be reevaluated in light of what we now know about fish.