Zebrafish have become the second most used vertebrate in biomedical research, yet welfare standards lag behind those for mammals despite evidence of zebrafish nociception and social cognition.
The regulatory framework for zebrafish welfare has not kept pace with their increased use in research. Early larval stages lack legal protection in most jurisdictions. Adult zebrafish in research facilities frequently experience social isolation, monotonous environments, and water quality fluctuations that cause measurable stress. Given that the value of zebrafish as a research model partly rests on their physiological similarity to humans, ignoring the welfare implications of that similarity is scientifically as well as ethically incoherent.