Principal component and path analysis of morphological traits of Epinephelus fuscoguttatus at different month ages

In order to research growth characteristics and the effect of morphological traits on body mass of Epinephelus fuscoguttatus at different month ages, data of total length (X₁), standard length (X₂), head length (X₃), body width (X₄), body depth (X₅), caudal peduncle depth (X₆), eye diameter (X₇), head length after eye (X₈) and body mass (Y) were collected at 3 months, 8 months and 13 months of age in this study. The morphological traits were analyzed by principal component and path analysis. The results showed that: (1) the correlation coefficients between all morphological traits at different age phases and body mass were extremely significant. And the correlation coefficients between each trait and body mass differed at different age development stages. (2) The first principal component reflected the growth and development of E. fuscoguttatus at different growth phases. The second principal component reflected the development of eye at different month ages. Thes third principal component was different and reflected the tail development at 3-month-old, body width development at 8-month-old and body height development at 13-month-old. (3) The trait with strongest direct effect on body mass was total length at all the age phases (0.742, 0.776 and 0.840). The path coefficients of four morphometric attributes (X₁, X₅, X₄, X₆) for 3-month body mass reached significant difference level. The path coefficients of X₁, X₄, X₆, and X₈ for 8-month body mass were also significant. The path coefficients of X₁, X₅, X₄ and X₂ for 13-month body mass were highly significant. The multivariate regression equation was Y_3-month-old=–36.774+3.992X₁+2.295X₅+2.759X₄+2.186X₆, Y_8-month-old=–64.569+7.020X₁+6.480X₄+6.754X₆+50.926X₈, and Y_13-month-old=–302.340+18.128X₁+17.688X₅–28.463X₄+5.928X₂. This result suggests that the vital traits that affected body mass at different growth phases were different. (4) The relation equation between standard length and body mass was W=0.0378L^2.873 (R²=0.9596) in 3-month to 13-month stages of E. fuscoguttatus, which demonstrated the standard length and body mass growth at similar velocity. We proposed that the total length was the target trait for selective breeding of E. fuscoguttatus at 3–13 month-old stages .This paper provides theoretical evidence and measure targets for breeding ofE. fuscoguttatus in the early growth stage in aquaculture.