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Okochi Y.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Okochi Y.,Tokyo University of Marine Science and Technology | Abe O.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Tanaka S.,Tokai University | And 3 more authors.
Fisheries Research | Year: 2016

A histological analysis of ovaries was conducted to examine reproductive characteristics of female Pacific bluefin tuna, Thunnus orientalis (Temminck and Schlegel, 1844), in the known spawning ground in the Sea of Japan. A total of 1040 females caught with purse seines were sampled from late May to early August in 2011 and 2012. The spawning season began in mid-June and continued until early August. The sex ratio for the catch in 2012 was nearly 1:1. The estimated spawning time was 1700-2200 h based on the occurrence of 0h postovulatory follicles. The estimated mean spawning frequency and mean spawning interval were 0.91 per day and 1.10 days, respectively, indicating that mature females spawn nearly every day in the Sea of Japan. The fork lengths at 50% and 95% mature were 114.4 cm and 133.6 cm, respectively. Batch fecundity was positively correlated with fork length, gilled and gutted body weight, and gonad weight. The mean batch fecundity was 6.4 million oocytes, and the mean relative batch fecundity per gilled and gutted body weight was 122 oocytes. This study provides some comprehensive information on reproductive biology of female Pacific bluefin tuna in the Sea of Japan. © 2015 Elsevier B.V.


Ueta K.,Shikoku University | Ueta K.,Tottori University | Ishihara Y.,Tottori Prefecture Fisheries Experimental Station | Yabuta Y.,Tottori University | And 2 more authors.
Journal of Liquid Chromatography and Related Technologies | Year: 2011

Vitamin B12 contents of Japanese rock-oyster "Iwa-gaki" (Crassostrea nippona) maintained high levels (14.2-19.8 μg/whole body and 20.1-27.0 μg/100g wet weight) in the oyster season (from June to August at Tottori-city in Japan). To evaluate whether the oyster contains true vitamin B12 or inactive corrinoid compound, a corrinoid compound was purified to homogeneity and partially characterized. TLC and HPLC patterns of the purified compound were identical to those of authentic vitamin B12. These results indicate that Japanese rock-oyster Iwa-gaki contains substantial amounts of true vitamin B12 and would be an excellent source of the vitamin. Copyright © Taylor &Francis Group, LLC.


Ishihara Y.,Tottori Prefecture Fisheries Experimental Station | Ishihara Y.,Tottori University | Imai E.,Tottori University | Takenaka S.,Osaka Prefecture University | And 4 more authors.
Food Science and Technology Research | Year: 2011

A substantial amount of vitamin B12 (357 ± 42.7 μg/100 g) was detected in pacific bluefin tuna (Thunnus orientalis) liver using a microbiological assay method. To evaluate whether tuna liver contains true vitamin B12 or an inactive corrinoid compound, a corrinoid compound was purified and characterized. The purified compound was identical to that of authentic vitamin B12, judging by TLC and LC/ESI-MS/MS chromatograms, and 1H NMR spectral data. These results indicate that pacific bluefin tuna liver contains substantial amounts of true vitamin B12 and would be an excellent source of the vitamin.

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