Facultative catadromy of the eel Anguilla japonica between freshwater and seawater habitats

• Published in: Marine ecology. Progress series (Halstenbek) 2001-01, Vol.220, p.265-276
• Main Authors: TSUKAMOTO, Katsumi, ARAI, Takaomi
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Anguilla japonica; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Marine; Vertebrata
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps220265

To confirm the occurrence of marine residents of the Japanese eel, Anguilla japonica, which have never entered freshwater ('sea eels'), we measured Sr and Ca concentrations by X-ray electron microprobe analysis of the otoliths of 69 yellow and silver eels, collected from 10 localities in seawater and freshwater habitats around Japan, and classified their migratory histories. Two-dimensional images of the Sr concentration in the otoliths showed that all specimens generally had a high Sr core at the center of their otolith, which corresponded to a period of their leptocephalus and early glass eel stages in the ocean, but there were a variety of different patterns of Sr concentration and concentric rings outside the central core. Line analysis of Sr/Ca ratios along the radius of each otolith showed peaks (ca 15 x 10 super(-3)) between the core and out to about 150 mu m (elver mark). The pattern change of the Sr/Ca ratio outside of 150 mu m indicated 3 general categories of migratory history: 'river eels', 'estuarine eels' and 'sea eels'. These 3 categories corresponded to mean values of Sr/Ca ratios of >6.0 x 10 super(-3) for sea eels, which spent most of their life in the sea and did not enter freshwater, of 2.5 to 6.0 x 10 super(-3) for estuarine eels, which inhabited estuaries or switched between different habitats, and of