Zebrafish are the second most widely used vertebrate in biomedical research globally, yet their welfare receives far less attention than mammalian laboratory species.
The rapid growth of zebrafish use in biomedical research has outpaced development of welfare standards. Unlike mammalian species covered by well-established refinement, reduction, and replacement frameworks, zebrafish welfare remains relatively poorly regulated and researched. Yet evidence of pain sensitivity and stress responses is growing. Key welfare issues include overcrowded tank housing, inadequate environmental enrichment, poor water quality management, and the use of larvae in high-throughput screening without welfare consideration. Applying the Three Rs framework consistently to zebrafish research and developing species-specific welfare guidelines are urgent priorities.