Zebrafish have become a major model organism in biomedical research, and their welfare requirements - including group housing, environmental enrichment, and humane experimental endpoints - are increasingly recognized.
Zebrafish welfare was historically neglected relative to mammalian research animals, partly due to assumptions about fish sentience and partly due to the sheer scale of use - millions of fish are used annually. Growing recognition of fish sentience and the expanding evidence base for zebrafish stress responses is driving protocol improvements. The 3Rs principles - Replace, Reduce, Refine - apply to zebrafish as to all research animals.