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Pasaia, Spain

Aldanondo N.,Marine Research Unit | Cotano U.,Marine Research Unit | Alvarez P.,Marine Research Unit | Uriarte A.,Marine Research Unit
Marine and Freshwater Research

In order to validate the first annual increment deposition in European anchovy otoliths, early juveniles were captured in October 2012 in the southern Bay of Biscay. These individuals were maintained under a continuous feeding regimen in a sea cage over a period of 6 months. From October 2012 to January 2013, lengths increased slightly or remained stable at ∼9.8cm. After this period, standard length increased significantly up to a mean value of 12.0cm in April 2013. Likewise, the age of anchovies was estimated based on otolith microstructure analysis. The estimated age varied from 96 days (for individuals sampled in October 2012) to 293 days (for anchovies sampled in April 2013). A daily increment deposition rate was confirmed in otoliths of individuals maintained in the sea cage during the winter. The general otolith daily growth pattern showed that increment widths increased rapidly and were broadest between 51 and 56 days, with a mean of 19.1μm. Thereafter, the widths decreased steadily to 1.5μm and remained almost constant until the end of the experiment. The present study also revealed that the first translucent band formation started in autumn and was completed by spring. © 2016 CSIRO. Source

Aldanondo N.,Marine Research Unit | Cotano U.,Marine Research Unit | Goikoetxea N.,Marine Research Unit | Boyra G.,Marine Research Unit | And 2 more authors.
Fisheries Oceanography

In order to understand better the recruitment variability in European anchovy in the Bay of Biscay, it is important to investigate the processes that affect survival during the early life stages. Anchovy juvenile growth trajectories and hatch-date distributions were inferred over a 3-year period based on otolith microstructure analysis. Otolith growth trajectories showed a characteristic shape depending on their hatch-date timing. Earlier-born juveniles had notably broader maximum increments than later born conspecifics, resulting in higher growth rates. This observation suggests that early hatching would be beneficial for larval and juvenile growth, and, therefore, survival. The estimated juvenile hatch-date distributions were relatively narrow compared with the extended anchovy spawning season (March-August) in the Bay of Biscay and indicated that only individuals originated mainly from the summer months (June-August) survived until autumn. Hatch-date distributions were markedly different among years and seemed to influence the interannual recruitment strength of anchovy. We conclude that years characterized by juvenile survivors originating from the peak spawning period (May and June) would lead to considerable recruitment success. Downwelling events during the peak spawning period seem to affect larval survival. Furthermore, size-dependent overwinter mortality would be an additional process that regulates recruitment strength in the anchovy population in the Bay of Biscay. © 2016 John Wiley & Sons Ltd. Source

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