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Changes in otolith microstructure and microchemistry during larval development of the European conger eel (Conger conger)

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Abstract

Otolith microstructure and chemical composition (Sr:Ca ratios) of the European conger eel (Conger conger) were examined during the larval developmental stages by scanning electron microscopy and wavelength dispersive spectrometer. Back-calculated hatching dates from the otolith microstructure of the developing leptocephali indicate a protracted spawning season from December to June. The early age of our developing specimens captured south of the Azores Islands suggests that the conger eel has another spawning area closer to Azores than the Mediterranean. Otolith increment width, which was relatively constant and narrow in the developing leptocephalus stage, increased sharply at age 170–250 days. Sr:Ca ratios in the otolith, which increased during the developing leptocephalus stage, showed a rapid drop coinciding with the increase in increment width. These coincidental changes were regarded as the onset of metamorphosis for this species. A close linear relationship between the age at metamorphosis and otolith growth rate indicates that the faster-growing larvae metamorphose earlier, suggesting that somatic growth should play an important role in the timing of metamorphosis. As shown in earlier work, the existence of an otolith marginal zone with unclear rings during metamorphosis prevents an accurate estimate of the larval stage duration of this species.

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Acknowledgements

The Portuguese Foundation for Science and Technology (Research Project Praxis XXI:2/2.1/MAR/1728/95) supported this study. The author has a PhD grant (BD 18082/98) from the same sponsor. We thank Dr. J. Wilson for English language assistance, and Dr. F. Ramos and Dr. P. Piedade for help in preparing and analysing the otolith microchemistry, respectively.

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Authors and Affiliations

  1. Centro Interdisciplinar de Investigação Marinha e Ambiental, Rua do Campo Alegre 823 , 4150-180, Porto, Portugal

    A. T. Correia, C. Antunes & J. Coimbra

  2. Instituto Ciências Biomédicas Abel Salazar da Universidade do Porto, Largo Abel Salazar 2, 4099-033, Porto, Portugal

    A. T. Correia & J. Coimbra

  3. Departamento de Oceanografia e Pescas da Universidade dos Açores, 9901-862, Horta, Portugal

    E. J. Isidro

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  1. A. T. Correia
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  2. C. Antunes
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Correspondence to A. T. Correia.

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Communicated by S.A. Poulet, Roscoff

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Correia, A.T., Antunes, C., Isidro, E.J. et al. Changes in otolith microstructure and microchemistry during larval development of the European conger eel (Conger conger). Marine Biology 142, 777–789 (2003). https://doi.org/10.1007/s00227-002-0993-4

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