Selection of the families with high growth rate and high female proportion in half-smooth tongue sole(Cynoglossus semilaevis)

The present study aims to uncover the relationship between the phenotypic sex and genotypic sex and the growth rate of male and female half-smooth tongue sole and to select the excellent families with high female proportion.In this paper,we firstly established 22 half-smooth tongue sole families which were cultured in the same pond.Secondly,we identified the offspring's phenotypic sex and genotypic sex of 5 normal male families and 5 neo-male families.This study shows that there are significant differences not only in growth rate but also in proportion of male to female.Two fast-growing families(No.16 and No.61)whose relative weight gain rate were 0.81 g/d and 0.56 g/d and 4 relatively fast-growing families(No.21,No.28,No.57 and No.63),the relative weight gain rate ranges from 0.48 g/d to 0.53 g/d were selected;12 commonly-growing and 4 slow-growing families were selected also.The average ratios of genotypic female and phenotypic female of the 5 normal male(ZZ)families were 51.87% and 42.94%,and the ratio of genotypic female reversing to phenotypic male was 14.08%.Instead,the average genotypic female and phenotypic female ratio of the 5 neo-male(ZW)families was 49.34% and 4.45%,respectively,and the ratio of genotypic female reversing to phenotypic male was 91.41%.In the present study we found for the first time that there were significant differences in phenotypic sex ratio between different families.We also found that the genotypic females in neo-male families were more easily reversed to phenotypic males,which increased the number of phenotypic males in cultured populations.It initially showed that the families with high female proportion and fast growing rate could be selected via family selection,which could provide theories and new technical methods for the breeding and the production of high quality seeding of half-smooth tongue sole.