PRINCIPAL COMPONENT AND DISCRIMINANT ANALYSES OF TRAITS OF NILE TILAPIA(OREOCHROMIS NILOTICUS) AT DIFFERENT AGES

In order to research the growth of morphological traits of Nile tilapia(Oreochromis niloticus) and judge the age matching with the size of Nile tilapia missing the best growing season,data were collected from 100 Nile tilapia at different ages individually.The body length,head length,trunk length,body depth,caudal peduncle length,caudal peduncle depth,body width and body weight were measured.The physical characteristics were analyzed by principal component and discriminant analysis.The results showed that the characteristics parameter of traits of Nile tilapia at different ages had notable correlation(P0.05),especially the relationship between body weight and body length and body depth.The principal components of Nile tilapia at different ages were different.The first principal component is body weight factor at 2―5 months.The second principal component was caudal peduncle factor at 2―4 months,but that was trunk factor at 5-month-old.The third principal component was head factor at 2-month-old,was trunk factor at 3―4 months,was caudal peduncle factor at 5-month-old.The month age closely related to the size of Nile tilapia which had missed the best growing period was deduced by established discriminant functions,the overall discriminant accuracy was 99.25%,which was 100% 2―4 months.