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
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 yr1).
KEY WORDS: Anguilla rostrata · American eel · Strontium:calcium ratios · Growth rate · Migratory history · Otolith check
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