Zebrafish are increasingly used in biomedical research but their welfare needs and capacity for suffering are often underappreciated in laboratory settings.
Zebrafish have become a laboratory workhorse partly because of assumptions about their simpler nervous system and lower welfare status compared to mammals. However, research increasingly indicates that zebrafish demonstrate stress responses, social preferences, and avoidance behaviours consistent with a capacity for negative experiences. The regulatory framework for zebrafish welfare has historically lagged behind the science, with larval stages often unprotected. As their use in research grows, the welfare implications of housing conditions, experimental procedures, and killing methods for millions of fish annually deserve serious attention. The Three Rs framework applies to zebrafish research, and opportunities for refinement through better housing, enrichment, and anaesthesia are well established but not universally implemented.