Zebrafish are the second most commonly used vertebrate in biomedical research. Their welfare needs, including social housing and environmental complexity, are increasingly recognised as scientifically and ethically important.
Zebrafish welfare in laboratory settings is an area of active improvement as researchers recognise that welfare-compromised fish produce unreliable data as well as experiencing suffering. Social isolation - common in individual housing protocols - causes measurable stress that affects both animal welfare and research validity. Environmental enrichment that provides substrate, vegetation, and hiding places improves welfare indicators without reducing experimental utility. The 3Rs framework applied to zebrafish is driving progressive welfare improvement through group housing requirements and enrichment standards that reduce stress and improve research reproducibility.