The scientific evidence that fish experience pain and suffering has grown substantially, with important implications for how we treat fish in aquaculture, fishing, and research.
The fish pain debate has been substantially settled by evidence: fish have the biological machinery for pain perception, show behavioural and physiological pain responses, and these responses are modified by analgesics in ways consistent with genuine pain experience. The lingering uncertainty is about the subjective, conscious quality of that experience — whether there is "something it is like" to be a fish in pain. Given the enormous numbers of fish killed and injured in aquaculture and fishing, applying the precautionary principle here — acting as if fish feel pain until proved otherwise — has potentially massive welfare implications. The most conservative scientifically defensible position now is that fish feel pain and deserve welfare protections accordingly.