Developing dynamic energy budget (DEB) models for small pelagic fishes in the Southern Benguela

Dynamic energy budget models are useful for describing energy flow in individual organisms as functions of their state (e.g., age, size, and energetic reserves) and environment (e.g., food and temperature). Anchovy (Engraulis encrasicolus), redeye round herring (Etrumeus whiteheadi) and sardine (Sardinops sagax) are short-lived fish species co-occurring in the Southern Benguela upwelling system, where they experience marked environmental variability. This study developed full life cycle dynamic energy budget models of these species in the Southern Benguela, which could be compared to the same or similar species in other ecosystems and investigated trade-offs between temperature and feeding conditions in influencing the growth and reproductive outputs of the three species. The key hypothesis was that there would be niche differences among bioenergetic factors for the three species that allow them to cooccur. Models were created and calibrated using published information and survey data (recruitment, biomass, weight-at-length) from 2012-2016. Best visual fit values were estimated for five parameters, using von Bertalanffy growth models and length-weight relationships of each species. Results indicated that redeye round herring invested less than anchovy and sardine in reproductive storage capacity (larger maintenance ratio) and had lower assimilation rates. Sardine had higher structural growth costs than anchovy and redeye round herring. Larval redeye round herring took longer to reach metamorphosis than anchovy and sardine. In all three species, decreased growth rates of larvae in cool waters were mitigated by increased growth from good food availability. Good feeding condition associated with cooler temperatures halved the time spent as recruits in all three species. Thus, increased growth rates from good food availability outweighed decreased growth rates from cool temperatures and resulted in higher egg batch production in adults. Comparisons of Southern Benguela anchovy and sardine to similar species in other ecosystems showed differences in core parameters between regions because of the influence of environmental inputs and species differences, indicating that model parameters may not be species-specific or transferable between ecosystems. Differential responses of small pelagic fish species to environmental factors help in understanding the variable population dynamics of these species and can help predict the impacts of climate change

A generalized Dynamic Energy Budget model including 3D shape changes for modeling small pelagic fish growth

International audienceUnderstanding pelagic fish growth patterns from early life stages to adulthood is fundamental to accurately predict larval survival and predator-prey dynamics, which are influenced by individual size. Dynamic Energy Budget (DEB) models constitute useful tools to predict and explain these patterns in changing environments. In DEB models, fish individuals are usually assumed to grow either isomorphically, or to experience a metabolic acceleration phase between birth (b) and metamorphosis (j), during which the shape coefficient changes and both the maximum surface-area specific assimilation rate and the energy conductance are multiplied by a metabolic acceleration coefficient function of structural length. Here we propose a different growth model based on a Dynamic Energy Budget model (modified as in Maury, 2019 to properly account for the size-dependence of maintenance) that captures deviations from pure isomorphy, allowing length and width to grow non-proportionally. Our model represents the fish’s structural body as an ellipsoid and differentially allocates volumetric growth to length, height and width as a function of the distance between the current shape and characteristic stage-dependent shape attractors (expressed as width/length and height/width ratios). The resulting changes of the structural surface-to-volume ratios due to changing shape mechanistically explain the “metabolic acceleration” phenomenon that is often invoked to interpret early life growth patterns. We estimated model parameters for the European anchovy Engraulis encrasicolus, using data covering growth at all life-stages, observed shapes at early life stages, transitions between life-stages, and reproduction. The calibrated model accurately reproduces the observed deviations from isomorphy, with exponential length-dominated growth until metamorphosis, then a shift to height- and width-dominated growth (with a corresponding deceleration of growth in length) until the adult shape is reached, and finally isomorphic (characteristic von Bertalanffy) length growth. These deviations from the usual von Bertalanffy growth model could profoundly affect our understanding of larval survival, predator-prey and ecosystem-dynamics

A generalized Dynamic Energy Budget model including 3D shape changes for modeling small pelagic fish growth

Understanding pelagic fish growth patterns from early life stages to adulthood is fundamental to accurately predict larval survival and predator-prey dynamics, which are influenced by individual size. Dynamic Energy Budget (DEB) models constitute useful tools to predict and explain these patterns in changing environments. In DEB models, fish individuals are usually assumed to grow either isomorphically, or to experience a metabolic acceleration phase between birth (b) and metamorphosis (j), during which the shape coefficient changes and both the maximum surface-area specific assimilation rate and the energy conductance are multiplied by a metabolic acceleration coefficient function of structural length. Here we propose a different growth model based on a Dynamic Energy Budget model (modified as in Maury, 2019 to properly account for the size-dependence of maintenance) that captures deviations from pure isomorphy, allowing length and width to grow non-proportionally. Our model represents the fish’s structural body as an ellipsoid and differentially allocates volumetric growth to length, height and width as a function of the distance between the current shape and characteristic stage-dependent shape attractors (expressed as width/length and height/width ratios). The resulting changes of the structural surface-to-volume ratios due to changing shape mechanistically explain the “metabolic acceleration” phenomenon that is often invoked to interpret early life growth patterns. We estimated model parameters for the European anchovy Engraulis encrasicolus, using data covering growth at all life-stages, observed shapes at early life stages, transitions between life-stages, and reproduction. The calibrated model accurately reproduces the observed deviations from isomorphy, with exponential length-dominated growth until metamorphosis, then a shift to height- and width-dominated growth (with a corresponding deceleration of growth in length) until the adult shape is reached, and finally isomorphic (characteristic von Bertalanffy) length growth. These deviations from the usual von Bertalanffy growth model could profoundly affect our understanding of larval survival, predator-prey and ecosystem-dynamics

A generalized Dynamic Energy Budget model including 3D shape changes for modeling small pelagic fish growth

International audienceSmall pelagic fish (SPF) are key components of marine ecosystems, transporting energy from the lower to the upper trophic levels and thereby influencing the dynamics of the entire ecosystem. Understanding their complex growth patterns from early life stages to adulthood is fundamental to accurately predict larval survival and predator-prey dynamics, which are influenced by individual size. However, growth models are generally unable to accurately reproduce the growth acceleration and deceleration phases observed, particularly during early life stages. Here we propose a growth model based on a Dynamic Energy Budget model (modified as in Maury, 2019 to properly account for size-dependence of maintenance) that captures deviations from pure isomorphy. It represents the fish’s body as an ellipsoid and differentially allocates volumetric growth to length, height and width as a function of the distance between the current shape and characteristic stage-dependent shape attractors (expressed as width/length and height/width ratios). The resulting surface-to-volume ratios mechanistically explain the “metabolic acceleration” often invoked to explain early life growth patterns. We estimated model parameters for three important SPF species in the Benguela upwelling system, using data covering growth at all life-stages, transitions between life-stages, and reproduction. The calibrated models reproduced the observed deviations from isomorphy, with exponential length-dominated growth until metamorphosis, then a shift to height- and width-dominated growth (with a corresponding deceleration of length growth) until the adult shape is reached, and finally isomorphic (characteristic von Bertalanffy) length growth. These deviations from the usual von Bertalanffy growth model could profoundly affect our understanding of larval survival, predator-prey and ecosystem-dynamic

A generalized Dynamic Energy Budget model including 3D shape changes for modeling small pelagic fish growth

Small pelagic fish (SPF) are key components of marine ecosystems, transporting energy from the lower to the upper trophic levels and thereby influencing the dynamics of the entire ecosystem. Understanding their complex growth patterns from early life stages to adulthood is fundamental to accurately predict larval survival and predator-prey dynamics, which are influenced by individual size. However, growth models are generally unable to accurately reproduce the growth acceleration and deceleration phases observed, particularly during early life stages. Here we propose a growth model based on a Dynamic Energy Budget model (modified as in Maury, 2019 to properly account for size-dependence of maintenance) that captures deviations from pure isomorphy. It represents the fish’s body as an ellipsoid and differentially allocates volumetric growth to length, height and width as a function of the distance between the current shape and characteristic stage-dependent shape attractors (expressed as width/length and height/width ratios). The resulting surface-to-volume ratios mechanistically explain the “metabolic acceleration” often invoked to explain early life growth patterns. We estimated model parameters for three important SPF species in the Benguela upwelling system, using data covering growth at all life-stages, transitions between life-stages, and reproduction. The calibrated models reproduced the observed deviations from isomorphy, with exponential length-dominated growth until metamorphosis, then a shift to height- and width-dominated growth (with a corresponding deceleration of length growth) until the adult shape is reached, and finally isomorphic (characteristic von Bertalanffy) length growth. These deviations from the usual von Bertalanffy growth model could profoundly affect our understanding of larval survival, predator-prey and ecosystem-dynamic

Caractérisation des différences de traits de vie chez les anchois du genre Engraulis spp.: Apports d'une approche de modélisation de type Dynamic Energy Budget

International audienceLes petits poissons pélagiques (PPP), au cœur du réseau trophique, ont un rôle clé dans l’écosystème. Représentant 20% des captures de pêche et étant la principale source d’oméga-3 pour l’Homme, ils sont cruciaux pour la sécurité alimentaire mondiale. Leur biomasse varie suivant les années et entre espèces mais les facteurs explicatifs restent à déterminer. Des parties de leur cycle de vie sont difficiles à étudier particulièrement l’investissement reproducteur. Le modèle bioénergétique basé sur la théorie Dynamic Energy Budget (DEB) permet de définir le cycle de vie de l’individu en quantifiant l’impact des conditions environnementales et de la physiologie sur trois processus physiologiques : croissance, développement et reproduction. Comparer les traits de vie et les conditions climatiques des régions avait pour but de quantifier les potentielles différences environnementales et physiologiques. L’étude s’est focalisée sur les 7 principales populations d’anchois du genre Engraulis spp. afin d’établir la variabilité inter-populationnelle des traits de vie de ce groupe d’espèces. Les résultats révèlent que (1) des environnements contrastés reproduisent ces différences de traits de vie, (2) la définition de la nourriture disponible pour un individu doit prendre en compte la compétition et la différence de qualité de nourriture et (3) un compromis entrecroissance et reproduction n’a pas pu être établi. Notre étude a donc confirmé l’hypothèse de travail d’une plasticité des traits de vie de l’anchois en fonction des conditions environnementales. Les perspectives de l’étude discutées concernent une meilleure prise en compte de la variabilité spatiale et interannuelle

Caractérisation des différences de traits de vie chez les anchois du genre Engraulis spp.: Apports d'une approche de modélisation de type Dynamic Energy Budget

International audienceLes petits poissons pélagiques (PPP), au cœur du réseau trophique, ont un rôle clé dans l’écosystème. Représentant 20% des captures de pêche et étant la principale source d’oméga-3 pour l’Homme, ils sont cruciaux pour la sécurité alimentaire mondiale. Leur biomasse varie suivant les années et entre espèces mais les facteurs explicatifs restent à déterminer. Des parties de leur cycle de vie sont difficiles à étudier particulièrement l’investissement reproducteur. Le modèle bioénergétique basé sur la théorie Dynamic Energy Budget (DEB) permet de définir le cycle de vie de l’individu en quantifiant l’impact des conditions environnementales et de la physiologie sur trois processus physiologiques : croissance, développement et reproduction. Comparer les traits de vie et les conditions climatiques des régions avait pour but de quantifier les potentielles différences environnementales et physiologiques. L’étude s’est focalisée sur les 7 principales populations d’anchois du genre Engraulis spp. afin d’établir la variabilité inter-populationnelle des traits de vie de ce groupe d’espèces. Les résultats révèlent que (1) des environnements contrastés reproduisent ces différences de traits de vie, (2) la définition de la nourriture disponible pour un individu doit prendre en compte la compétition et la différence de qualité de nourriture et (3) un compromis entrecroissance et reproduction n’a pas pu être établi. Notre étude a donc confirmé l’hypothèse de travail d’une plasticité des traits de vie de l’anchois en fonction des conditions environnementales. Les perspectives de l’étude discutées concernent une meilleure prise en compte de la variabilité spatiale et interannuelle

Caractérisation des différences de traits de vie chez les anchois du genre Engraulis spp.: Apports d'une approche de modélisation de type Dynamic Energy Budget

International audienceLes petits poissons pélagiques (PPP), au cœur du réseau trophique, ont un rôle clé dans l’écosystème. Représentant 20% des captures de pêche et étant la principale source d’oméga-3 pour l’Homme, ils sont cruciaux pour la sécurité alimentaire mondiale. Leur biomasse varie suivant les années et entre espèces mais les facteurs explicatifs restent à déterminer. Des parties de leur cycle de vie sont difficiles à étudier particulièrement l’investissement reproducteur. Le modèle bioénergétique basé sur la théorie Dynamic Energy Budget (DEB) permet de définir le cycle de vie de l’individu en quantifiant l’impact des conditions environnementales et de la physiologie sur trois processus physiologiques : croissance, développement et reproduction. Comparer les traits de vie et les conditions climatiques des régions avait pour but de quantifier les potentielles différences environnementales et physiologiques. L’étude s’est focalisée sur les 7 principales populations d’anchois du genre Engraulis spp. afin d’établir la variabilité inter-populationnelle des traits de vie de ce groupe d’espèces. Les résultats révèlent que (1) des environnements contrastés reproduisent ces différences de traits de vie, (2) la définition de la nourriture disponible pour un individu doit prendre en compte la compétition et la différence de qualité de nourriture et (3) un compromis entrecroissance et reproduction n’a pas pu être établi. Notre étude a donc confirmé l’hypothèse de travail d’une plasticité des traits de vie de l’anchois en fonction des conditions environnementales. Les perspectives de l’étude discutées concernent une meilleure prise en compte de la variabilité spatiale et interannuelle