Zebrafish are among the most widely used vertebrates in biomedical research, but their welfare needs including social housing, environmental complexity, and humane endpoints are often neglected.
Zebrafish welfare has lagged behind that of rodents in research settings despite their vertebrate status and growing evidence of sentience and stress responses. Social isolation, a common feature of many experimental protocols, causes measurable welfare harm. The 3Rs framework (Replace, Reduce, Refine) applies fully to zebrafish research, and refinements including social housing, environmental enrichment, and better-defined humane endpoints produce measurable welfare improvements without compromising research validity.