Zebrafish have become one of the most widely used vertebrate research models, yet their welfare needs are often underestimated. Their numerical scale means welfare improvements have enormous aggregate impact.
Zebrafish welfare is a frontier area where welfare science is advancing rapidly but institutional practice lags behind. As social shoaling fish, zebrafish experience measurable distress when isolated — cortisol responses are activated within minutes. Standard tank sizes and configurations often prevent normal social and exploratory behaviour. Procedural welfare is often overlooked: fin clipping without anaesthesia is painful, and routine netting and transfer cause acute stress that can affect research outcomes. The scale of zebrafish use — tens of millions per year — means even modest welfare improvements have massive aggregate impact. The emerging recognition of zebrafish sentience is driving better welfare standards, but implementation is inconsistent across institutions and countries.