Location,size and age at onset of metamorphosis in the Japanese eel Anguilla japonica |
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| Authors: | N Fukuda D Ambe S Chow T Yamamoto K Yokouchi A Shinoda Y Masuda M Sekino K Saitoh M Masujima T Watanabe N Mochioka H Kuwada |
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| Institution: | 1. National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 6‐31‐1 Nagai, Yokosuka, Kanagawa 238‐0316, JapanBoth authors contributed equally to this work.;2. National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2‐12‐4 Fukuura, Kanazawa, Yokohama, Kanagawa 236‐8648, Japan;3. National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 6‐31‐1 Nagai, Yokosuka, Kanagawa 238‐0316, Japan;4. Department of Biology, Tokyo Medical University, A13 6‐1‐1 Shinjuku, Tokyo 160‐8402, Japan;5. National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, 183‐2 Irozaki, Minami‐Izu, Kamo Shizuoka 415‐0156, Japan;6. Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency, 3‐27‐5, Shinhama, Shiogama, Miyagi 985‐0001, Japan;7. National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, 2‐12‐4 Fukuura, Kanazawa, Yokohama, Kanagawa 236‐8648, Japan;8. Fisheries Agency of Japan, 1‐2‐1, Kasumigaseki, Chiyoda‐ku, Tokyo 100‐8950, Japan;9. Bioresource Sciences, Faculty of Agriculture, Kyushu University, Fukuoka‐City Fukuoka, 812‐8581, Japan |
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| Abstract: | This study clarifies the location, size and age at the onset of metamorphosis in Japanese eels Anguilla japonica through oceanic surveys, rearing experiments and analyses of the morphology and otoliths of leptocephali and glass eels. Twenty‐eight metamorphosing leptocephali were collected in the mesoscale eddy region to the east of Taiwan during research expeditions in 2004. Rearing experiments showed that the total length (LT) of leptocephali decreased by an average of 12·5% during metamorphosis and 13·9% during the 2–12 h after death. Thus, the mean back‐calculated LT at the onset of metamorphosis for 630 glass eels from Taiwan and Japan was estimated at 67·8 ± 2·7 mm (mean ± S.D.). The estimated mean ante‐mortem size of the fully grown pre‐metamorphic leptocephali collected in 2004 was 64·6 ± 3·4 mm, which was consistent with the LT estimate for glass eels. Otolith analysis showed that the mean age at the onset of metamorphosis was 137 ± 15 days and indicated that Japanese eels may have a recruitment route through the mesoscale eddies to the east of Taiwan in addition to the direct transfer route from the North Equatorial Current to the Kuroshio Current. |
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| Keywords: | glass eel larval transport leptocephalus North Pacific otolith shrinkage |
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