Abstract:To study the effect of morphological difference and morphological characteristics on body weight of reciprocally-crossed subgroups of Oreochromis niloticus × O. Aureus, this study undertook to track and measure body weight and seven growth-related morphological traits, including total length, standard length, head length, body depth, caudal peduncle length, caudal peduncle depth, body width. Fifty individuals were randomly selected in the orthogonal group, and 50 males and 50 females were randomly selected in the backcrossing group for our analysis. All experimental fish are cultured in the same pond. The results showed that the total length, body depth and caudal peduncle depth 3 traits have a major impact on the weight of forward hybrid subgroups, thus establishing a multivariate regression equation related to body weight as YBW=–154.286+9.016XTL+10.065XBD+17.884XCPD; Meanwhile for female individuals of reverse hybrid subgroups, total length and body depth, were two traits found to have a major impact on body weight, thus establishing a multivariate regression equation related to body weight as YBW=–92.582+7.415XTL+8.727XBD; for male individuals, standard length and body depth are the two traits which have a major impact on body weight, thus establishing a multivariate regression equation related to body weight as YBW=–120.299+8.661XSL+16.590XBD. In order to eliminate the influence of differences in body size among the individuals, we obtained seven proportion characteristics including BS, TS, HS, BDS, CLS, CDS, and BWS, respectively. In the characteristic coefficients plots of principal components factor scores, those seven proportion characteristics were divided into two groups, the first group concluded TS, BDS, CDS, BWS and HS, the other concluded BS and CLS. We drew a scatter plot through the score coefficients of every individuals in principal component factors PCR1 and PCR2. In the plot, the individuals of forward hybrid males could obviously be differentiated with reverse hybrid females. The conclusion showed that the morphological traits affecting body weight were different between different hybridization methods and different genders. In the selection of broodstock and the breeding of progeny, comprehensive traits selection should be adopted to improve the accuracy and stability of the breeding results.
