Depletion of naturally recruited wild Japanese eels in Okayama,Japan, revealed by otolith stable isotope ratios and abundance indices |
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| Authors: | Kenzo Kaifu Kazuki Yokouchi Tomihiko Higuchi Hikaru Itakura |
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| Institution: | 1.Faculty of Law,Chuo University,Tokyo,Japan;2.National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency,Yokosuka,Japan;3.Atmosphere and Ocean Research Institute, The University of Tokyo,Kashiwa,Japan;4.Chesapeake Biological Laboratory,University of Maryland Center for Environmental Science,Solomons,USA;5.Graduate School of Science,Kobe University,Nadaku, Kobe,Japan;6.Graduate School of Frontier Sciences,The University of Tokyo,Kashiwa,Japan |
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| Abstract: | To investigate the population dynamics of naturally recruited wild Japanese eels, fisheries data of wild individuals in Okayama Prefecture were investigated as a case study. Wild and stocked eels were discriminated using a recently developed method based on otolith stable isotopes. Of the 161 eels captured in freshwater areas where eels had been stocked, 98.1% were discriminated as stocked. In contrast, 82.8% of 128 eels captured in coastal areas where eels are not stocked were discriminated as wild. There was a significant decrease in longline and set-net catch per unit effort between 2003 and 2016 in the coastal areas where most eels were discriminated as wild, indicating ongoing depletion of wild Japanese eels in these waters. |
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