Parental effects on sex ratios in progeny of the European sea bass (Dicentrarchus labrax)

In European sea bass (Dicentrarchus labrax), females grow 20-50% faster than males. Therefore, they are more in demand than males for commercial farming, generating much interest in the development of female monosex populations. Whereas most current research focuses on the influence of temperature on sex determination, the present experiments aimed at studying parental effects on sex ratios in progeny. The study analyzed progeny resulting from a diallel crossing (2 x 2 type or a complete bi-factorial mating design), reflecting both maternal and paternal genetic relatedness among progeny. The proportion of females varied significantly among families (20.7-68.2%). There were significant maternal and paternal effects on the proportion of females among the progeny. The effect of the parental interaction on the sex ratio in the progeny was also significant. Parents had a significant effect on total length and body weight. Sexual growth dimorphism, in favor of females, was evident in all the full-sib families and varied significantly between families. Among offspring at 9-9.5 months (68.9 +/- 23.7 g), females were 26.6% heavier than males. It is concluded that in addition to temperature manipulation in sea bass, as proposed in earlier studies, selection of parents will probably result in an improved ratio of female to male progeny.