Zebrafish have become a major model organism in biomedical research, raising welfare questions that differ from those for rodents but are no less important.
Zebrafish welfare has received less attention than mammalian model organisms despite their vast numbers and growing evidence for nociception and stress responses from early development. Regulatory frameworks often exempt early larvae, but scientific evidence suggests meaningful capacity for negative experience emerges sooner than thresholds reflect. Group housing, enrichment, water quality, and humane endpoints are all welfare-relevant for zebrafish. As their use in research grows, so does the importance of applying the 3Rs framework thoughtfully to this species.