Zebrafish have become one of the most widely used laboratory vertebrates, with millions used annually in biomedical research under welfare standards that are still evolving.
The welfare of laboratory zebrafish has historically received less attention than that of mice or rats, partly because their small size and aquatic nature create different challenges. However, evidence of their capacity for stress responses and nociception makes welfare improvement morally important. Key welfare challenges include maintaining water quality at scale, providing appropriate social grouping (zebrafish are shoaling fish), and minimizing procedural stress. The early larval exclusion from regulation also creates a welfare gap that warrants precautionary consideration.