Zebrafish are used in millions of experiments annually; increasing evidence of their sentience demands urgent attention to their welfare in laboratory settings.
Zebrafish welfare has historically received minimal attention compared to mammalian models, partly because their small size and aquatic lifestyle makes welfare assessment difficult. However, their complex behavioral repertoire, social nature, and documented pain responses indicate they experience welfare-relevant states. Chronic stress from inadequate housing, poor water quality, and social isolation causes physiological stress responses. Application of the 3Rs framework to zebrafish research is growing but still lags behind mammalian welfare standards significantly.