Effects of morphometric traits on body weight for juvenile Polyodon spathuln
The relationships between morphometric traits and body weight of juvenile Polyodon spathuln for 30 d and 41d were analyzed in this study.Nine morphometric traits including total length(X1),head length(X2),snout length(X3),body width(X4),head width(X5),interorbital distance(X6),body depth(X7),head depth(X8) and body weight(Y) from 120 P.spathuln were measured.The correlation coefficients and path coefficients were calculated by correlation analysis,path analysis and multiple regression analysis.The results showed that all the correlation coeffi-cients of each morphometric trait to body weight were all at extremely significant level(P0.01),excepting for the correlation coefficients of head length to body weight of 41 d P.spathuln.The path coefficients of total length,body width,head width and head depth for 30 d P.spathuln to body weight all achieved very significant level(P0.01).The path coefficients of total length,body depth,head width,interorbital distance and body width for 41d P.spathuln to body weight all achieved very significant level(P0.01).There were some difference in the direct effect of mor-phometric traits to body weight in different years old,but the path coefficients of total length,body width and head width to body weight for 30 d and 41 d P.spathuln all achieved very significant level(P0.01),among which total length was the most predominant variable to affect body weight.The diversification of determinant coefficients analysis was consistent with that of path analysis.The morphometric traits which reached level of significance(P0.05) were used to establish the multiple regression equations,which were LgY =-3.808 + 1.759 Lg X1 + 0.235 Lg X5 + 0.336 Lg X7 + 0.308 Lg X4 in 30 d P.spathuln and LgY =-3.374 + 1.328 Lg X1 + 0.591 Lg X8 + 0.253 Lg X4 + 0.231 Lg X6 + 0.198 Lg X5 in 41 d P.spathuln,respectively.