Sea resident Japanese eel collected from Kozushima Island, Japan

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A Japanese eel Anguilla japonica was collected off Kozushima Island, one of the volcanic Izu Islands in Japan. The external morphology corresponded to a silvering stage (Silvering Index: S1) with a melanized body coloration of the head, and the tip of the lower jaw to the anus. However, the value of the gonado-somatic index of the female eel was low, and the oocytes were not matured (peri-nucleolus stage). Otolith analyses indicated that the individual had exclusively inhabited the sea for five years without entering freshwater. This record is the first collection of silver-phased Japanese eel in the Kuroshio region, which could be on the spawning migration route of the species, although it was not determined if the eel was settling around the Izu Islands or migrating to the spawning ground.

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We are grateful to Kazuto Ando and Ichiro Komazawa of Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries, and to Ryosuke Matsue and Kazutaka Hamakawa for providing the eel specimen. We thank Toyoji Kaneko for the technical support of the histological analysis.

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Correspondence to Mari Kuroki.

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Kuroki, M., Mikawa, N., Mizuta, F. et al. Sea resident Japanese eel collected from Kozushima Island, Japan. Ichthyol Res (2020).

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  • Anguilla japonica
  • Izu Islands
  • Silver eel
  • Spawning migration