Zebrafish have become the second most commonly used laboratory animal after mice. Growing evidence of zebrafish sentience and complex behavior raises important welfare questions for research settings.
Zebrafish welfare is an emerging area where welfare science is catching up with rapidly increasing research use. Evidence of nociception, stress responses, and social complexity suggests zebrafish experience welfare-relevant states. Regulatory protection typically begins at 120 hours post-fertilization, but early larvae show pain responses before this threshold. Social isolation causes stress responses. Tank enrichment, appropriate social housing, and less invasive sampling techniques can improve zebrafish welfare with minimal impact on research validity.