Decreasing trend in size for small pelagic fish across European waters: Bioenergetic modeling to explore the underlying individual to population scale processes

• Main Authors: Menu, Clara, Pecquerie, Laure, Bacher, Cedric, Doray, Mathieu, Hattab, Tarek, Kooij, Jeroen van Der, Huret, Martin
• Other Authors: Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDE]Environmental Sciences; Northeast Atlantic
• Online Access: https://hal.science/hal-04179051

International audience Small pelagic fish have shown a general decrease in size and body condition over the past two decades in several European regional seas. Although the underlying processes are still not well understood, recent studies point to a bottom-up control. In order to better understand how the environment impacts the main individual life history traits through phenotypic plasticity, we developed a comparative approach between two species, European anchovy and sardine, and across three regions of the Northeast Atlantic and Mediterranean Sea, namely the English Channel, the Bay of Biscay and the Gulf of Lion. We developed a bioenergetic modeling framework based on Dynamic Energy Budget theory (DEB). The first part of this work focuses on testing the bottom-up hypothesis at the individual scale. While this mechanistic framework successfully reproduced the spatial differences in size across the three studied regions, the temporal trends in the environment (temperature and zooplankton) were not strong enough to explain the drastic decrease in size through time. Through a scenario approach, we estimated the decrease in zooplankton quantity or quality required to reproduce the decrease in small pelagic size. Secondly, we assessed the effect of this bottom-up control on fish biomass and size distribution by scaling up to the population level using an existing DEB-IBM (Individual Based Model) in the Bay of Biscay. We also assessed the effects of population drivers, e.g. density-dependence, fishing and selective mortality, on population dynamics.