Current Status of the Zebrafish Euthanasia and Humane Endpoint in the Republic of Korea and Guideline Suggestion from Nationwide Expert Elicitation: A Model for Other Countries.

Since its introduction as a model organism in the 1980s, the use of zebrafish ( Danio rerio ) in research has expanded worldwide. Despite its now widespread use in research, guidelines to safeguard the ethical treatment of zebrafish, particularly with regard to euthanasia and humane endpoint practices, remain inadequate. One well-recognized example is the use of excess tricaine methanesulfonate (MS-222) as a means to euthanize zebrafish, regardless of life stage. In this study, through nationwide expert elicitation, we provide a detailed account of zebrafish research practices within the Republic of Korea and the challenges of implementing appropriate methods for euthanasia as a humane endpoint, with many opting for hypothermic shock. We report a local expert consensus for establishing national guidelines to improve zebrafish welfare and good research practice. Suggestions and recommendations for national guidelines were offered. Taken together, our findings raise awareness broadly among zebrafish research practitioners in the field, offer an accurate account of the welfare and treatment of zebrafish in research within the Republic of Korea, and advocate for the development and implementation of national guidelines. As such, our study is useful as a model to adopt the expert elicitation approach to investigate, quantify, and address welfare concerns in zebrafish research, and to establish best practice guidelines.