Occurrence of estuarine and sea eels <Emphasis Type="Italic">Anguilla japonica</Emphasis> and a migrating silver eel <Emphasis Type="Italic">Anguilla anguilla</Emphasis> in the Tokyo Bay area,Japan |
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| Authors: | Takaomi Arai Naoko Chino Aya Kotake |
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| Institution: | (1) International Coastal Research Center, Ocean Research Institute, The University of Tokyo, Otsuchi Iwate, 028-1102, Japan;(2) Graduate School of Fisheries Sciences, Kitasato University, Ofunato Iwate, 022-0101, Japan;(3) Ocean Research Institute, The University of Tokyo, Nakano, Tokyo 164-8639, Japan |
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| Abstract: | Otolith microchemical analyses of the strontium (Sr) and calcium (Ca) concentrations in the eels Anguilla japonica and A. anguilla caught in Tokyo Bay were undertaken to reconstruct the eels’ migratory histories. A. japonica in the yellow stage (immature stage) were caught in a bay without any adjacent rivers or streams. A. anguilla was in the silver stage (early maturing stage), and the eel was confirmed to have just begun spawning migration to the open
ocean from Tokyo Bay based on the otolith Sr:Ca ratios, which showed a typical catadromous life history with low Sr:Ca ratio
values throughout the eel’s life after recruitment. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicated the eels belonged to several general categories of migratory histories,
including sea eels (average Sr:Ca ratio ≥6.0 × 10−3) and estuarine eels (average Sr:Ca ratio 2.5 to 6.0 × 10−3) based on the criteria reported previously in A. japonica. All eels had a certain freshwater life period, although the period was highly variable among fish. These results indicate
that A. japonica has a flexible pattern of migration, with the ability to adapt to various habitats and salinities. |
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