Zebrafish have become one of the most widely used vertebrates in biomedical research, raising important welfare questions about housing, handling, anaesthesia, and the nature of their sentient experience.
Zebrafish welfare has received less attention than mammalian research species, partly because their small size and aquatic nature make welfare assessment less intuitive for researchers trained with mammalian models. However, the evidence for zebrafish sentience is substantial, and the scale of their use — millions of animals across thousands of facilities — makes welfare improvements potentially impactful. Housing enrichment that enables schooling behaviour, careful anaesthesia protocols, and attention to water quality are all practically achievable refinements. The regulatory gap around early larvae also deserves attention as research increasingly uses embryonic stages for drug screening.