Effect of dietary lipid composition on vitellogenin, 17β-estradiol and gonadotropin plasma levels and spawning performance in captive sea bass (Dicentrarchus labrax L.)

The influence of dietary lipid composition on the reproductive performance of the sea bass (Dicentrarchus labrax) and on vitellogenin (VTG), 17β-estradiol (E2) and gonadotropin II (GtH II) plasma levels has been investigated. The control group was fed with a natural diet consisting of trash fish (Boops boops). Two experimental groups were fed with pelleted diets containing different amounts of lipids: Group A was fed with a commercially available diet with a 10% lipid content and Group B fed the base diet enriched to a 22% lipid content using refined fish oil enriched with n - 3 fatty acids. The control group exhibited higher egg viability and hatching rate than the experimental groups. The better spawning performance of the control group, with respect to the experimental groups, was associated with differences in endocrine profiles during the reproductive cycle. In the experimental groups, E2 levels were higher than in controls during the period of vitellogenesis. In the profiles of VTG levels, groups A and B exhibited a greater decrease of plasma VTG during the mid spawning time as compared to the control group. Profiles of plasma GtH II levels were determined for the first time in the sea bass and showed a single annual peak during the spawning period. At that time, GtH II levels from groups A and B were higher than in the controls. The present data suggest that dietary lipid composition significantly affects the reproductive performance of the sea bass.This work was supported in part by the EEC projects: FAR no. AQ 2 406 E UK to N.C. and LT no: AIR2-CT93 1005 to N.B. and a NATO project no. CRG 940889 to S.T. J.N. received a PhD fellowship from the Generalitat Valenciana and actually has a bursary from the EC (Contract No. Env-4-CT965042) in the Center for Environmental Research, Leipzig, Germany. GtH II analysis were supported by an NOAA research grant (No. NA46RG0091) to Y.Z. from Maryland Sea Grant