Zebrafish are the second most commonly used vertebrate in UK research, yet their welfare needs are less well understood than those of rodents and refinement efforts are catching up.
Zebrafish welfare refinement has accelerated as the species has become more widely used. Key areas include enriched housing with plants and shelters, appropriate shoal sizes, refined anaesthesia for procedures, and improved endpoints for experiments involving pain or distress models. The unregulated status of early larvae creates a welfare gap - while larvae may have reduced sentience, best practice suggests welfare consideration should begin before the regulated developmental stage. Research institutions should proactively apply refinement principles throughout zebrafish life stages.