To examine the birth seasons of Japanese embiotocid fishes, Ditrema temmincki, D. viridis and Neoditrema ransonneti, samples were collected at Otsuchi Bay northern Japan in July 2000. Specimens of the three species were divided into small and large size groups, respectively. Large groups included gravid females and females just after parturition. Most embryos extracted from the gravid females were grown and ready to birth. All fish of the small groups were slightly larger than the embryos, indicating that the former fish were young just after birth. Thus, the birth seasons of the three species appeared to be from July to early August. Their annual reproductive cycles may differ from those in southern Japan where the birth seasons have been reported being from May to July.
