Scientific understanding of fish sentience has advanced significantly, with evidence for pain, fear, learning, and potentially subjective experience reshaping how fish welfare is considered in science and policy.
The scientific consensus on fish sentience has shifted dramatically in the past two decades. The traditional assumption that fish do not feel pain — based on absence of a neocortex — has been replaced by understanding that fish have functionally equivalent pain processing systems in different brain structures. Behavioral, neurological, and physiological evidence converge on fish as sentient beings capable of suffering. This evidence base underlies growing policy recognition of fish welfare, including the UK's Animal Welfare (Sentience) Act and expanding aquaculture welfare standards. The welfare implications are profound given the billions of fish affected by human activities annually.