Zebrafish have become the second most used vertebrate in biomedical research, yet their welfare needs and capacity for suffering remain poorly understood and often neglected.
Zebrafish have been adopted as a research model partly because of assumptions that they are less sentient than mammals — assumptions increasingly contradicted by neuroscience research. Their exclusion from welfare oversight in many jurisdictions means billions of fish are held in conditions that cause chronic stress without any regulatory requirement to improve their lives. Providing flow, structural enrichment, stable shoal groups and appropriate lighting cycles are low-cost refinements with measurable welfare benefits. Updating regulatory frameworks to include zebrafish — and other fish — in animal welfare protections is an urgent and tractable welfare priority.