Zebrafish are the world's most commonly used research fish, with millions used annually in biomedical studies, yet their welfare needs only recently gained serious scientific attention.
Zebrafish welfare in research has historically been neglected compared to mammalian species, partly due to assumptions about fish sentience. However, growing evidence confirms zebrafish experience nociception, stress, and respond adaptively to adverse conditions. Poor tank conditions - inadequate water quality, inappropriate social grouping, barren environments - cause chronic stress measurable through cortisol and behavioural endpoints. The regulatory gap at early larval stages means many experiments occur without welfare oversight. Refinement of zebrafish research is an area of active development, with housing standards, anaesthesia protocols, and humane endpoints all improving.