Departmental Bulletin Paper Morphological and physiological characteristics of an oceanic-migrating Japanese eel Anguilla japonica off Fukushima, Japan

Matsuya, Noriaki  ,  Hagihara, Seishi  ,  Wada, Toshihiro  ,  Ijiri, Shigeho  ,  Adachi, Shinji

38 ( 1 )  , pp.8 - 11 , 2015-07 , International Coastal Research Center, Atmosphere and Ocean Research Institute, the University of Tokyo
A female silver Japanese eel Anguilla japonica (681 mm TL) was captured by bottom trawl off Fukushima on 18 October 2013. This is the first report of an oceanic-migrating Japanese eel in the western North Pacific Ocean off northern Japan. We described the status of the silvering stage, morphological characteristics, age, developmental stage of the ovaries, and the serum levels of sex steroids for the eel. The GSI of the eel was 2.33 and the mean diameter of the largest group of oocytes was 269.9 μm and these were at the early vitellogenic stage. The serum E2 level was 3.9 ng/ml and 11-KT was 17.9 ng/ml. These steroid levels were higher than the mean steroid levels of female silver eels captured in Hamana Lake, but other morphological and physiological characteristics of the eel were not much different from those of silver eels captured in river, estuary, and coastal waters.

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