Body Condition Scoring for Adult Zebrafish (Danio rerio).

Body condition scoring (BCS) is a simple, rapid, noninvasive tool used to assess body condition in animals. In this study, wedeveloped and validated a diagram-based BCS for adult zebrafish (Danio rerio), a popular research model. After receiving 20min of hands-on training regarding the scoring system, 5 people each rated 95 adult zebrafish. The fish then were euthanizedand measured to establish body condition indices (BMI and the Fulton K factor). Both condition indices were highly correlatedwith fish width. Using correlation data and observed trends in fish width, we established expected BCS definitions. Wevalidated the BCS definitions in 2 ways. First, we calculated the Pearson correlation coefficient between the average observedBCS and expected BCS; this statistic revealed very strong correlation between observed and expected BCS. In addition, weassessed the predictive power of BCS by using multinomial logistic regression and then applied the fitted model to evaluatethe accuracy of the predictions (BCS compared with BMI, 85%; BCS compared with K factor, 61%). Finally, to determine therobustness of BCS to variation among raters, we calculated the intraclass correlation coefficient and demonstrated high interrater reliability. In conclusion, adult zebrafish BCS can be used to quickly identify animals with different body conditionindices (thin to obese). In addition, the diagram-based chart is easy to use and implement accurately, with minimal training.