ホシガレイ

The reproductive biology of female spotted halibut, Verasper variegutus, was examined from 19 specimens sampled in Tachibana Bay, Nagasaki Prefecture during 27 December 1997 to 30 January 1998. The maturity stages of the ovaries were categorized into three classes based on the histological characteristics and the size-frequency distribution of oocytcs; pre-spawning, spawning and post-spawning. The occurrence rates of the different maturity stages of ovaries during the collection period suggested that the spawning season of spotted halibut in Tachibana Bay extends from late December to early February. Developing oocyte in the course of vitellogenesis formed a single clutch separated from the pre-vitellogenic oocyte group, which resulted in showing two peaks isolated each other in the size-frequency distribution of oocytes. After the completion of vitellognesis in all oocytcs of the advanced clutch, final oocyte maturation and following ovulalion occurred in a part of oocytes of the clutch. The number of oocytes of the advanced clutch gradually decreased during the spawning season due to serially occurring ovulalion. The ovaries after spawning contained only pre-vitellogenic oocytes scattered among the degenerating postovulatory follicles. Total fecundity (TF) in five fish with the ovaries at the prc-spawning stage was related to total length (TL, mm) as TF=7.45・10-6TL4.08 (341≦TL≦488).