Induced ovulation of Japanese flounder (Limanda yokohamae) with human chorionic gonadotropin and salmon gonadotropin, with special reference to changes in quality of eggs retained in the ovarian cavity after ovulation.

Abstract

This study was undertaken to determine the effects of delay between ovulation and stripping on egg quality in the Japanese flounder. Post-ovulatory eggs were divided into 2 categories. Eggs in stage I were normal, whereas those in stage II were over-ripened and observed to be 3 to 5 days affer ovulation. In HCG-treated fish the percentages of successful fertilization and hatching indicatied were maximal one day after ovulation, followed by a rapid decrease, whereas in SG-G100-treated fish the fertilization rate was maximal 2 days after ovulation, followed by a more gradual decrease. It is shown that flounder eggs remain in good condition for 2 or 3 days depending upon the type of hormone used to induce ovulation. Changes in body weight, water and sodium contents of the eggs are discussed in relation to the over-ripening phenomenon.