Zebrafish are increasingly used in biomedical research, with their numbers now exceeding traditional mammalian models in some institutions. Developing appropriate welfare standards for this species is an urgent priority.
Zebrafish welfare occupies a regulatory and ethical gap - their numbers have outpaced welfare standard development. The assumption that small size equates to lesser welfare concern is not supported by evidence of their capacity for pain and stress responses. Welfare improvements for research zebrafish include appropriate group housing and social management, optimal water quality maintenance, handling protocols that minimize stress, appropriate anesthesia for painful procedures, and regular welfare assessment. The growing scientific evidence for zebrafish pain experience makes development of species-specific welfare assessment tools urgent. Research institutions with strong zebrafish programs should invest in welfare science alongside the biological research that drives their use.