Discovery of mature freshwater eels in the open ocean
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All freshwater eels of the genus Anguilla are catadromous, in that they perform long-distance migrations to offshore spawning area after years of growth in freshwater and near-shore habitats . Finding younger and smaller leptocephali indicated the spawning area to be located in the Sargasso Sea for European and American eels (Anguilla anguilla and A. rostrata, respectively) [2, 3] and in the western North Equatorial Current (NEC) area of the western North Pacific to the west of Mariana Islands for Japanese and giant mottled eels (A. japonica and A. marmorata, respectively) [4, 5, 6]. Recent investigation could further narrow down the area and timing for spawning of the Japanese eel (A. japonica), where a large number of small pre-leptocephali (n = 130, 4.2–6.5 mm in total length) were collected during the new moon in June 2005 around 14°N, 142°E to the west of the Suruga Seamount of the West Mariana Ridge . No matured adult eels have been captured or observed to date in the...
KeywordsAnguilla First catch Freshwater eels Matured males Spawning area
We thank the captains and crews of R/V Kaiyo Maru and R/V Hakuho Maru for assisting sample collection, K. Kawaguchi, T. Wada and M. Arimoto for realizing this research cruise, and S. Clarke for reading the manuscript. We gratefully acknowledge the financial support of the Fishery Agency of Japan and Fisheries Research Agency.
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