Zebrafish are increasingly used as biomedical research models, with growing evidence for their capacity to experience pain requiring updated welfare standards.
The regulatory gap around zebrafish welfare reflects historical uncertainty about fish sentience that is increasingly contradicted by the evidence. As zebrafish use has expanded dramatically — they now number in the hundreds of millions in research globally — their welfare deserves commensurate attention. Best practice includes analgesia for painful procedures, refinement of euthanasia methods to minimize distress, and application of the 3Rs framework consistently. Welfare regulations should be updated to reflect current scientific consensus on zebrafish sentience.