Zebrafish are among the most widely used research animals globally, yet welfare standards for their care and use lag behind those for mammals. Applying refinement principles to zebrafish protects billions of animals.
Zebrafish welfare has historically been neglected relative to mouse and rat welfare, despite zebrafish being used in equal or greater numbers in many countries. The assumption that fish are lower-welfare organisms requiring less protection has been challenged by growing evidence of pain sensitivity, social needs and emotional states in zebrafish. The regulatory gap for larvae under 5 days post-fertilisation in the UK is a particular concern, as genetically modified lines often cause welfare compromise from early developmental stages. Applying the 3Rs (Replacement, Reduction, Refinement) rigorously to zebrafish - including environmental enrichment, social housing and anaesthesia for procedures - would significantly reduce unnecessary suffering.