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Marine Ecology Progress Series

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MEPS 310:219-233 (2006)  -  doi:10.3354/meps310219

Migration of juvenile American eels Anguilla rostrata between freshwater and estuary, as revealed by otolith microchemistry

B. M. Jessop1,*, J.-C. Shiao2, Y. Iizuka3, W.-N. Tzeng4

1Department of Fisheries and Oceans, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada
2Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan 11529, ROC
3Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, Taiwan 11529, ROC
4Institute of Fisheries Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan 10617, ROC

ABSTRACT: The temporal patterns in the otolith Sr:Ca ratios of yellow-phase American eels Anguilla rostrata from the East River, Chester, on the Atlantic coast of Nova Scotia, Canada, indicated variable patterns of migration between river and estuarine/marine waters. About 29% of yellow eels (n = 107) had a history of migration between river and estuary other than their initial entry. Male and sexually undifferentiated eels, potentially mostly male, comprised 96% of the sample and females comprised 4%, but the proportions of migratory and non-migratory eels did not vary by sex or development stage. Most migrants (81%) made only 1 round trip, while 19% made 2 round trips. Yellow eels with a migratory history were patchily distributed, with most (84%) concentrated 9.4 km upriver. About 36% of yellow eels showed a check (false annulus) corresponding with a habitat transition from estuary to river, while for 16% of yellow eels the check occurred during the initial freshwater entry as an elver. Otolith checks not associated with a habitat transition occurred for 22% of yellow eels, primarily at intermediate ages. Mean lengths-at-age were higher for eels with a history of primarily estuarine growth than for eels of primarily freshwater growth, as were annual growth rates (26.6 versus 21.7mm yr–1).

KEY WORDS: Anguilla rostrata · American eel · Strontium:calcium ratios · Growth rate · Migratory history · Otolith check

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