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Published July 2022 | Published
Journal Article Open

Severe winter conditions improve recruitment success of blue whiting (Micromesistius poutassou), a temperate water fish species, in the NW Mediterranean sea

Abstract

Fish recruitment variability results from a complex mix of biological and physical processes, and their interactions, acting in the early life stages. In this study, we aim to investigate the environmental factors driving the recruitment success of blue whiting (Micromesistius poutassou) in the NW Mediterranean through reconstruction of early life history traits derived from otoliths microstructure analysis. To this purpose, the study characterizes the oceanographic conditions in winter-spring of two contrasted years, 2017 and 2018, and relates them to the onset and duration of the spawning, growth performance and condition of blue whiting recruits. Winter 2017 was mild, with a short period of cold temperatures and limited winter vertical mixing. In winter 2018, temperatures reached lower values and extended for a longer period with intense vertical mixing and dense water cascading down the continental slope at the end of February. These different conditions were mirrored in the subsequent phytoplanktonic bloom, which in 2018 occurred later and was more intense than in 2017, extending over a longer period and occupying a wider area. The reproductive period of blue whiting was linked to the duration of low winter temperatures (∼13 °C), shorter in 2017 than in 2018 (∼40 and ∼ 60 days respectively). While in 2017 all individuals were born in a relatively short period of time, and under similar environmental conditions, in 2018 the hatching period presented two differentiated peaks, separated by a period of relatively low hatchings at the end of February. This gap corresponded to dense water cascading and intense vertical mixing events, suggesting that these phenomena limited the survival of eggs and larvae. The few individuals hatched in this period showed the lowest growth rates (maximum values ∼ 1.5 mm TL day⁻¹), which would be related with the poor trophic environment during these events of intense mixing. Conversely, in both years, higher growth rates corresponded to the individuals born just before the phytoplankton bloom (attaining ∼ 2 mm TL day⁻¹). Recruits of 2018 showed better condition than those born the previous year which would be associated with the higher primary production detected in spring 2018. The recruitment strength in 2018, estimated from landings, was also much higher indicating that severe winter conditions translate into improved recruitment of a temperate water fish in the NW Mediterranean Sea.

Additional Information

© 2022 The Authors. Published by Elsevier Under a Creative Commons license - Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Received 12 January 2022, Revised 8 April 2022, Accepted 16 May 2022, Available online 27 May 2022, Version of Record 1 June 2022. We greatly appreciate the assistance of the crew of the fishing vessel Medan during the samplings. Thanks are due to the crew of the R/V García del Cid and colleagues from the Institut de Ciencies del Mar (ICM-CSIC) and Unidad de Tecnología Marina (UTM-CSIC) who helped us with the sampling during the oceanographic cruises. This research was funded by project [CTM2015-68543-R], Spain. We thank 3 anonymous reviewers for their accurate and constructive comments. J.M-A. was supported by a predoctoral fellowship of the FI program of the Secretaria d'Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons Social Europeu (FSE) [2019FI_B2 00183]. Thanks are due to the Fisheries Service of the Generalitat de Catalunya for the access to the fishing statistics. This work acknowledges the Severo Ochoa Centre of Excellence accreditation [CEX2019-000928-S]. Data availability. MUR data may be downloaded from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) at https://podaac.jpl.nasa.gov. MODIS data is available at NASA's Ocean Color website at https://oceancolor.gsfc.nasa.gov/l3/. The data set on landings and effort (fishing days) over the period 2017–2019 were obtained from the fishing statistics of the Generalitat de Catalunya. Other data underlying this article were generated by the authors and will be shared on reasonable request to the corresponding authors. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023