Establishing quality standards for Kohaku Koi Fish (

This study aims to quantify the quality standards for Kohaku koi fish (Cyprinus rubrofuscus) by integrating truss morphometric measurements, red color coverage area, and pigmentation intensity analysis. Twenty-four juvenile Kohaku specimens were selected from the results of selective crossbreeding between Nidan female parents and Sandan Kohaku male parents. Morphometric analysis measured 21 truss morphometric characters of koi fish, and digital image analysis using ImageJ software measured the area of coverage and intensity of red color. Principal component analysis and hierarchical clustering were employed to classify phenotypic patterns of individual fish characteristics. Results demonstrated significant morphometric variation with coefficients ranging from 10.76% to 27.91% within the population. Red color coverage area varied extensively from 4,200 to 442,851 pixels, while intensity values ranged from 85.2 to 160.0 on a 0-255 scale. Kohaku specimens with larger red areas show higher color intensity, wider tail fins, and greater body depth. Size distribution analysis revealed 41.7% large, 37.5% medium, and 20.8% small fish, demonstrating successful selective breeding outcomes. This integrated quantitative approach provides a scientific foundation for standardized quality evaluation, replacing subjective assessment methods and supporting data-driven breeding programs to enhance the aesthetic and economic value of Kohaku koi in commercial production.