Artificial fertilization of Senegalese sole ( Solea senegalensis): Hormone therapy administration methods, timing of ovulation and viability of eggs retained in the ovarian cavity

Abstract

One method to overcome the difficulties involved in reproducing first generation Senegalese sole that are born in captivity (F1) is to obtain gametes by stripping and then using them for artificial fertilization. The aim of this paper was to determine an appropriate protocol for hormonal induction of ovulation and artificial fertilization. To induce ovulation, two different GnRHa administration methods, weekly injections versus a single GnRHa implant, were compared. The number of spawns per female and the relative fecundity were significantly higher in females that received the hormonal therapy through repeated injection (6.3 ± 0.8 spawns per female and 574.9 ± 67.2 × 10 3 eggs kg −1 BW) than those treated with a single implant (2.7 ± 0.6 spawns per female and 134.6 ± 40.9 × 10 3 eggs kg −1 BW). The lapsed time to ovulation and the changes in fertilization and hatching rates of eggs that were retained in the ovarian cavity after ovulation were determined after GnRHa treatment. At 16 °C, ovulation was detected at 41–44 h post-treatment in 70% of the females. The highest fertilization and hatching rates were obtained during the first 3 h after ovulation, and they significantly decreased thereafter. The results suggested that the GnRHa injection was the most appropriate administration method for the induction of ovulation. Ovulated eggs inside the female were viable for a short time, and therefore it is important to determine the time of ovulation after hormonal treatment.