Correlation and Path Analysis of Shell Morphological and Body Mass Traits in Pacific Abalone (Haliotis discus hannai)

Body mass, the primary target in the selective breeding of aquatic mollusks, is less intuitive to assess than shell morphological traits. To improve breeding efficiency, this study used path analysis to examine the influence of shell morphological traits on body mass. Shell length (X_L), width (X_W), height (X_H), perimeter (X_P), and area (X_A), along with total weight (Y_W) and soft body weight (Y_S), were measured in 2-year-old female and male Pacific abalone (Haliotis discus hannai). Correlation and path analysis were conducted with shell morphological traits (X_L, X_W, X_H, X_P, and X_A) as independent variables and body mass traits (Y_W and Y_S) as dependent variables. Correlation analysis revealed significant relationships between body mass and shell morphological traits in both sexes (P < 0.05). Path analysis revealed that in females, shell perimeter (0.500), height (0.451), and length (0.212) had the strongest direct effects on total weight, whereas in males, shell area (0.611), length (0.431), and width (-0.039) were most influential. For soft body weight, shell length had the highest coefficient of determination in females (0.504), while shell area had the highest in males (0.458), indicating sex-specific differences in traits affecting body mass. Importantly, shell length was identified as a key determinant of body mass across all four multiple regression equations. These findings suggest that shell length can be directly used for rapid breeding selection on farms to efficiently identify abalones with higher body weight, thereby providing a theoretical foundation for improved germplasm resource utilization and innovative breeding strategies.