Zebrafish are the second most commonly used vertebrate in biomedical research globally, and their welfare requires specific attention to tank density, water quality, social grouping, and analgesic protocols for experimental procedures.
Zebrafish welfare deserves the same systematic attention as mammalian research animals. They show behavioral indicators of pain, social deprivation stress, and responses to adverse conditions that reflect genuine welfare states. Their small size and large numbers create a welfare context where individual attention is impractical, making tank management systems the primary welfare lever. Density, social grouping, water quality, and enrichment at the tank level determine the welfare of thousands of individual fish simultaneously.