Zebrafish are increasingly used in biomedical research, raising welfare questions about pain and stress in a species whose sentience was long underestimated.
Zebrafish welfare is an area where science and ethics are actively evolving. Evidence that zebrafish respond to pain in functionally similar ways to mammals, and that these responses are modifiable by analgesics, supports the view that they experience something meaningfully analogous to suffering. The sheer scale of zebrafish use in research - millions of animals annually - means even modest welfare improvements could have large aggregate impact. Chronic housing stress in overcrowded or barren tanks causes measurable physiological changes and may constitute ongoing suffering. The 3Rs framework increasingly applies to zebrafish, but implementation lags significantly behind mammalian species.