Zebrafish are the third most commonly used vertebrate in UK research. Their welfare is governed by the same regulatory framework as mammals, but species-specific welfare knowledge is less developed and presents ongoing challenges.
Zebrafish welfare in research represents an area where regulatory coverage has outpaced species-specific welfare knowledge. Researchers are required to consider and minimise zebrafish suffering but have fewer validated welfare assessment tools than for mammalian species. Group housing requirements are well-established, but optimal group sizes, social compositions, and environmental enrichment are less well-defined. The large numbers of zebrafish used - including embryonic stages where welfare status is uncertain - mean that cumulative welfare impact across the research sector is substantial. Investing in zebrafish-specific welfare science, including validated pain and stress indicators, would substantially improve the ability of institutions to meet their welfare obligations.