Zebrafish (Danio rerio) have become a premier research model organism, with millions used annually. Applying the 3Rs principles — especially refinement — to zebrafish research improves welfare and data quality simultaneously.
Zebrafish welfare has historically received less attention than rodent welfare, partly because fish sentience has been contested and partly because the vast scale of zebrafish use has made individual welfare attention seem impractical. However, zebrafish show behavioral and physiological responses to adverse conditions that indicate subjective experience, and refinement improvements are both feasible and scientifically justified. Social housing, environmental enrichment, and validated handling protocols demonstrably reduce zebrafish stress and improve data quality. As the research community increasingly accepts fish sentience, zebrafish refinement standards will continue to evolve.