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Evaluation of the larval distribution and migration of the Japanese eel in the western North Pacific |
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| Authors: | Akira Shinoda Jun Aoyama Michael J Miller Tsuguo Otake Noritaka Mochioka Shun Watanabe Yuki Minegishi Mari Kuroki Tatsuki Yoshinaga Kazuki Yokouchi Nobuto Fukuda Ryusuke Sudo Seishi Hagihara Kei Zenimoto Yuzuru Suzuki Machiko Oya Tadashi Inagaki Shingo Kimura Atsushi Fukui Tae Won Lee Katsumi Tsukamoto |
| Institution: | 1. Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan 8. Department of Biology, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku, Tokyo, 160-8402, Japan 2. Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, East, Fukuoka, Fukuoka, 812-8581, Japan 3. The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan 4. School of Marine Biosciences, Kitasato University, Ofunato, Iwate, 022-0101, Japan 5. Fisheries Laboratory, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 2971-4 Bentenjima, Maisaka, Hamamatsu, Shizuoka, 431-0214, Japan 6. Graduate School of Marine Science and Technology, Tokai University, 3-20-1 Orito Shimizu, Shizuoka, Shizuoka, 424-8610, Japan 7. Department of Oceanography, Chungnam National University, Daejeon, 305-764, Korea |
| Abstract: | The distribution of all larval stages of the Japanese eel, Anguilla japonica, were examined using historical catch records and original data in the western North Pacific (WNP) to evaluate existing information about the larval distribution and migration of this species. A total of 148 preleptocephali, 2547 leptocephali, 6 metamorphosing larvae, and 21 glass eels were collected during 37 cruises over a 52-year period (1956?C2007). Sampling effort was spatio-temporally biased in latitude/longitude among seasons with sampling effort being concentrated near the western margin of the subtropical gyre near Taiwan in the winter season and extensive effort occurring near the spawning area to the east near the seamount chain of the West Mariana Ridge in summer during the spawning season. The distribution of preleptocephali (4.2?C8.7 mm) was limited to a narrow area around 14°N, 142°E just west of the southern part of the seamount chain, while leptocephali (7.7?C62.0 mm) were widely distributed at increasing size westward in the North Equatorial Current (NEC) to the region east of Taiwan. Metamorphosing larvae (52.7?C61.2 mm) were collected only in the area 21?C26°N, 121?C129°E to the east of Taiwan, while glass eels (51.3?C61.2 mm) occurred only within or west of the Kuroshio. These distributions suggest that leptocephali begin to metamorphose within or just east of the Kuroshio, then after completion of metamorphosis the glass eels detrain from the current and migrate inshore. The relationship between catch date and body size of leptocephali suggested that the spawning season is from April to August, but further sampling is needed to eliminate possible effects of sampling bias. This analysis is consistent with the existing hypothesis that Japanese eel larvae born near the West Mariana Ridge are transported westward in the NEC and then transfer to the Kuroshio to recruit to East Asia, although more sampling effort is needed for later stage larvae in the NEC bifurcation region to help understand the larval migration in relation to the possible impacts of ocean?Catmosphere changes. |
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