Morphological variation and mathematical analysis of effects of morphological traits on body-weight of GIFT tilapia after 3 generations of breeding

Abstract

GIFT strain of Nile tilapia(Oreochromis niloticus) played an important role in world fishery.Several researches indicated that the growth performance of GIFT can still be improved.As an important indicator of breeding,body-weight was influenced by many morphological traits,and morphological traits that impact offspring body-weight might be changed after breeding,so comparative analyses of the impacts of morphological traits on body-weight between the offspring and parental generation became necessary.Sixty families of GIFT were introduced into FFRC as the parents(P) in 2006 for further study,three generations of offspring were bred(F1,F2,F3).In order to observe the achievement of breeding,body-weight(Y),body-length(X1),body-thickness(X2) and body-height(X3) of the P and F3 were measured,variation of four morphological traits of P and F3 were analyzed;correlation analysis,path analysis and regression analysis were used to calculate the correlation coefficient,path coefficient and the coefficient of determination,and the multiple regression equations between body-weight(Y) and morphological traits(X1,X2,X3)were established and analyzed.Results showed that: 1) compared with P,body-weight,body-length and body-thickness of F3 had a significant increase(P0.01),meanwhile a certain decline in the coefficient of variation(CV) was observed,body size of tilapia of F3 showed a trend of being consistent.Male of F3 had increased in some degree,significant increase of 4 traits of the male group was not observed.2) Trait af-fected the body-weight most of F3 converted to body-length,which was body-height×body-length in P.3) The influence of body-length,body-thickness and body-height on body-weight declined more in F3 than that in P.Results above indicated that,breeding made a positive effect on the growth speed of GIFT;for further study we should be more careful in selecting morphological traits,and some other morphological traits which might impact the body-weight should be taken into account for more accurate breeding project.