Timing of metamorphosis and larval segregation of the Atlantic eels Anguilla rostrata and A. anguilla, as revealed by otolith microstructure and microchemistry |
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Authors: | T Arai T Otake K Tsukamoto |
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Institution: | (1) Ocean Research Institute, The University of Tokyo, Minamidai, Nakano, Tokyo 164-8639, Japan e-mail: arait@ori.u-tokyo.ac.jp Tel.: +81-3-53516520; Fax: +81-3-53516514, JP;(2) Faculty of Bioresources, Mie University, Kamihama, Tsu 514-8507, Japan, JP |
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Abstract: | Otolith microstructure and microchemistry were examined in juveniles of American (Anguilla rostrata) and European (A. anguilla) eels. Otolith increment width markedly increased from age 132 to 191 d (156 ± 18.9 d; mean ± SD) in A. rostrata and 163 to 235 d (198 ± 27.4 d; mean ± SD) in A. anguilla, both of which were coincident with drastic decreases in otolith Sr:Ca ratios, suggesting that metamorphosis from leptocephalus
to glass eel began at those ages in each species. The duration of metamorphosis was estimated to be 18 to 52 d from otolith
microstructure, for both species studied. Ages at recruitment were 171 to 252 d (206 ± 22.3 d; mean ± SD) in A. rostrata and 220 to 281 d (249 ± 22.6 d; mean ± SD) in A. anguilla. In these two species, positive linear relationships were found in ages between the beginning of metamorphosis and recruitment,
suggesting that early metamorphosing larvae recruited at younger ages. Duration of the leptocephalus stage to recruitment
in A. anguilla was about 40 d longer than that in A. rostrata. The geographical segregation between the two species in the Atlantic Ocean seems to be involved in the differences in the
duration of the leptocephalus stage (age at metamorphosis).
Received: 8 November 1999 / Accepted: 8 May 2000 |
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