2024-03-29T01:46:19Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/355652022-11-17T02:08:08Zhdl_2115_20049hdl_2115_141夏季の中部北太平洋におけるサンマの成熟と日齢Maturation and age in days of Pacific saury Cololabis saira (Brevoort) in the central North Pacific Ocean during the summer巣山, 哲桜井, 泰憲島崎, 健二サンマ成熟過程日齢中部北太平洋660The maturation process and age in days of female Pacific saury Cololabis saira (Brevoort) in the central North Pacific Ocean were examined based on histological observations and otolith daily growth increments. The maturation process of Pacific saury used in this study (243-342mm in knob length) was divided into 6 stages: early yolk vesicle stage, late yolk vesicle stage, yolk formation stage, maturation stage, atretic stage I, and atretic stage II. Atretic stage fish were considered to be post-spawning as many degenerated oocytes were observed. The large size group (more than 296mm), in which fish were more than 1.5 years old as estimated from daily growth increments in otoliths, contained spawning and post-spawning individuals, although all individuals from the medium size group (241-295mm), from 10 months to 1 year and 3 months old, were immature. Since post-spawning fish were seen to have recovered their initial condition factors, it is suggested that they survive beyond the first spawning season. Based on observations of asynchronously developing oocytes, it is considered that Pacific saury spawn several times during a single spawning season.日本水産学会Journal Articleapplication/pdfhttp://hdl.handle.net/2115/35565https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/35565/3/62_361.pdf0021-53921349-998XAN00193422日本水産学会誌6233613691996-05-15jpninfo:doi/10.2331/suisan.62.361© 1996 公益社団法人日本水産学会publisher