Zebrafish welfare in laboratory settings is improved significantly by appropriate social housing, and evidence-based minimum group sizes are increasingly incorporated into institutional standards.
Zebrafish social housing welfare is an area where welfare improvements align directly with research quality improvements. Isolated zebrafish show elevated stress hormones, altered behaviour, and physiological changes that can confound experimental results. Group housing with appropriate environmental enrichment produces animals with lower baseline stress, more stable physiology, and behaviour more representative of natural populations — improving both welfare and research validity simultaneously. This alignment provides a compelling scientific argument for welfare improvement that goes beyond ethical obligation alone. Institutional standards are increasingly incorporating minimum group size and enrichment requirements, but implementation consistency varies significantly between facilities and researchers.