Zebrafish are one of the most widely used vertebrates in biomedical research. As their use grows, so does the scientific evidence supporting their welfare needs and sentience.
Zebrafish are sometimes used as a lower-welfare-scrutiny alternative to mammals in research, but growing evidence of their sentience challenges the assumption that their welfare matters less. They experience pain, fear, and social stress in ways that should trigger welfare obligations comparable to those applied to rodents. Research facility zebrafish husbandry often focuses on water chemistry and disease prevention while neglecting behavioural needs — social housing, environmental enrichment, and management of chronic stressors. The welfare science for zebrafish is rapidly advancing; translating this science into facility practice and regulatory standards is the current challenge. The enormous scale of zebrafish use makes welfare improvement in this species one of the highest-leverage interventions in laboratory animal welfare overall.