北海道噴火湾におけるキュウリウオ雌魚の成熟 Gonadal Maturation of Female Rainbow Smelt Osmerus eperlanus mordax in Funka Bay, Hokkaido
Rainbow smelt <i>Osmerus eperlanus mordax</i>, were collected during May 1993 to April 1995 from Funka Bay, Hokkaido, and the Yamazaki and Rukotsu rivers, which flow into the western side of the bay. Ovarian eggs from females were examined histologically. Oocytes from the chromatin-nucleolus stage to the ripe stage were found in the ovaries. From May to August, females had immature oo-cytes in the yolkless stage and yolk vesicle stage. Postovulatory follicles were also found in the ovaries of females collected from the bay in May. After November, a bimodal distribution of egg diameter was observed. More advanced oocytes developed from the primary-yolk stage in November to the migratory-nucleus stage in April. These observations indicate that group-synchronous oocyte development occurred.<br>All oocytes in the migratory-nucleus stage from females collected by set nets in the coastal area off Mori were found in late April. From late April to mid-May, oocytes of females collected from the two rivers were in the ripe stage. These results suggest that rainbow smelt inhabiting Funka Bay spawn from late April to mid-May in the rivers flowing into the western coast of the bay. Visual observations of adults in the rivers and the developmental process of oocytes indicate that rainbow smelt return to the sea after spawning.
日本水産学会誌 63(1), 50-55, 1997-01-15