Efficient Artificial Fertilization Method Based on the Ovulation Cycle in Barfin Flounder Verasper moseri

In this study, we investigated the ovulation cycles, time course of a decline of fertilization rate due to over-ripening, and effect of semen quality on the fertilization rate, in order to establish an efficient technique of artificial fertilization in barfin flounder Verasper moseri. The ovulation cycle of this species is 3 to 4 days at 6°C. The fertilization rate of the eggs pressed out just after ovulation attained about 90%, gradually decreasing with time after ovulation, and fell to 45% on average 2 days after ovulation. The difference of the spermatocrit values had little influence on the fertilization rate. These results indicate that the fertilization rate depends primarily on the time after ovulation. It is important for successful fertilization to estimate the ovulation date by checking ovulation during the early spawning season, and to use fresh eggs soon after ovulation.