Mathematical analysis of effects of morphological traits on body weight for tilapia Oreochromis niloticus

The body weight(Y),body length(X1),head length(X2),trunk length(X3),body depth(X4),caudal peduncle length(X5),caudal peduncle depth(X6) and body width(X7) were measured in 57 female and 64 male 1-year old tilapia Oreochromis niloticus.The correlation analysis and path analysis revealed that the correlation coefficients of each morphological trait to body weight were all of very significant(P0.01).The key effective factors of the body weight were found to be body length,body depth,body width and head length in female tilapia,while the body depth,body length,trunk length,and body width seemed to be the key effective factors of the body weight in the male.The females had the maximal determination coefficients of body length(0.178)for body weight,and the males showed the maximal determination coefficients of body depth(0.136)for body weight.There were very greater determination coefficients of body depth,body length and trunk length in male tilapia.The relationship between morphometric traits and body weight was expressed as Y=-443.542+16.525X1-17.106X2+40.658X4+56.038X7 in the females and as Y=-684.921+15.531X1+25.413X3+38.976X4+48.213X7 in the males(P0.05).