Path analysis and curve fitting of morphometric traits and body weight of juvenile Aspiorhynchus laticeps.

In this experiment, correlation analysis, path analysis, regression analysis and curve-fitting methods were employed to investigate the relationships between the body weight (Y) and morphological variables (X1-X36) of juvenile Aspiorhynchus laticeps (common name: big-head schizothoracin). These methods were used to identify the main morphological trait indices affecting body weight and further determine the optimal fitting models between four main morphological traits and body weight. The study found that 94% of the morphological traits of juvenile A. laticeps had a highly significant positive correlation with body weight (p < 0.01). The trait with the highest correlation with body weight (Y) was the distance from the starting point of the dorsal fin base to the starting point of the pelvic fin base (CI, X30), with a correlation coefficient of 0.921. The correlation between the distance from the end of the dorsal fin base to the starting point of the anal fin base (DH, X34) and body weight was not significant (p > 0.05), while other morphological traits had a significant positive correlation (p < 0.05). The quantification of the effect of morphological traits on body weight (Y) by path analysis showed that the trait with the greatest direct effect was CI (X30, 0.430) and the trait with the greatest indirect effect was body width (X3) through CI (X30, 0.335). Through regression analysis and calculation of the determination coefficient, it was found that CI (X30) had the largest direct determination coefficient for body weight (0.185), and the combined determination coefficient of body width (X3) and CI (X30) was the largest (0.169). The multiple regression equation of the four morphological traits and body weight was Y = -8.827 + 0.449X30 + 0.381X3 + 0.217X11 + 0.118X35. Among the optimal fitting models of the four main morphological traits and body weight, the optimal fitting model of body width (X3) and body weight (Y) was an exponential function equation ln(Y) = -17.517 × (1/X3) + 3.767 (R = 0.718), the optimal fitting model of mouth cleft height (X11) and body weight was a power function equation ln(Y) = -9.847 × (1/X11) + 3.065 (R = 0.560), the optimal fitting model of CI (X30) and body weight was a logarithmic function equation ln(Y) = -36.207 × (1/X30) + 4.308 (R = 0.881), and the optimal fitting model of the distance from the end of the dorsal fin base to the starting point of the ventral caudal fin (DF, X35) and body weight was a logarithmic function equation ln(Y) = -61.089 × (1/X35) + 3.811 (R = 0.728). The research results indicate that in the breeding selection of juvenile A. laticeps, CI (X30) should be taken as the main selective trait, supplemented by body width (X3), mouth cleft height (X11) and DF (X35) as references.