長崎および銚子沖合産トガリツノザメの繁殖生態

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  • Some aspects of reproduction in the pointed-snout dogfish Squalus japonicus taken off Nagasaki and Choshi.
  • 長崎および銚子沖合産トガリツノザメの繁殖生態〔英文〕
  • ナガサキ オヨビ チョウシ オキアイサン トガリツノザメ ノ ハンショク セイ

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Specimens of the pointed-snout dogfish Squalus japonicus taken off Nagasaki and Choshi, were investigated to study its reproduction. Specimens from Choshi were larger in the size at maturity as well as in the maximum size than those from Nagasaki. The size at first maturity for females was 560-157mm in Nagasaki and 740-759mm in Choshi. Maximum lengths were greater by 14cm for males and 19cm for females in Choshi than in Nagasaki. Testis weights and clasper lengths showed a rapid increase with onset of maturity. The gestation period was estimated to be roughly one year sine both full-term embryos and fertilized eggs occurred in the same period. Litter size ranged from 2 to 8 for each region but average litter size was 3.9in Nagasaki and 5.3in Choshi. Litter size increased with size of the parent. A difference was also noted in the average number of ovarian eggs per adult female between the two regions (4.4in Nagasaki and 6.6in Choshi). Ova usually outnumbered embryos and showed a similar growth pattern to embryos. The ratio of males to females in embryos was approximately 1:1 as a whole in both regions.

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  • 日本水産学会誌

    日本水産学会誌 47 (9), 1157-1164, 1981

    公益社団法人 日本水産学会

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