土佐湾のマイワシにおける卵母細胞の吸水完了および産卵開始時刻

概要

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Tosa Bay in southwestern Japan is one of the main spawning grounds for the Japanese sardine Sardinops melanostictus (Temminck et Schlegel). The time of maximal oocyte hydration and that of spawning in Japanese sardine were monitored in Tosa Bay by collecting fish by drift net about once an hour from 1, 815 to 2, 145hours on 18 November 1990. The water content in oocytes increased significantly until about 2, 000hours but remained unchanged thereafter. Similarly, oocyte volume increased until about 2, 000hours but remained constant thereafter. The frequency distribution of gonadosomatic index values changed drastically at about 2, 100hours, and the total percentage of females with hydrated oocytes and ovulated eggs decreased from 45.9 to 21.4% at this time. These results indicate that the hydration of oocytes in Japanese sardme in Tosa Bay was completed at about 2, 000hours and that the spawning started at about 2, 100hours.
日本水産學會の論文