13 research outputs found
Study of the life-history traits of two species of polychaetes, Arenicola marina and A. defodiens, implementation of a Dynamic Energy Budget model and conservation of the species
Les arĂ©nicoles sont des polychĂštes benthiques prĂ©sentant un cycle de vie bentho-pĂ©lagique complexe avec deux phases de dispersion larvaire seulement partiellement dĂ©crit jusquâĂ prĂ©sent. Ces espĂšces sont intensĂ©ment pĂȘchĂ©es comme appĂąt sur les plages de la Manche orientale, notamment au sein dâune aire marine protĂ©gĂ©e, le Parc naturel marin des estuaires picards et de la mer dâOpale. Sans mesures de gestion, cette activitĂ© pourrait entraĂźner une diminution des populations dâarĂ©nicoles tout en affectant les caractĂ©ristiques physiques des plages et la biodiversitĂ© associĂ©e. Tout dâabord, deux espĂšces dâarĂ©nicoles ont Ă©tĂ© identifiĂ©es, Arenicola marina et A. defodiens, et leurs abondances, leurs distributions spatiales, ainsi que certains de leurs traits de vie (pĂ©riode de ponte, taille de premiĂšre maturitĂ© sexuelle) ont Ă©tĂ© mesurĂ©es sur 4 sites dâĂ©tude. Ces donnĂ©es ont Ă©tĂ© comparĂ©es Ă des donnĂ©es de pĂȘche pour estimer si les populations dâarĂ©nicoles Ă©taient exploitĂ©es durablement, et pour fournir de potentielles mesures de gestion (De Cubber et al., 2018). Sur lâun des sites Ă©tudiĂ©s, A. marina Ă©tait prĂ©sente en grands nombres en mĂ©diolittoral supĂ©rieur et moyen tandis que A. defodiens occupait les niveaux mĂ©diolittoral infĂ©rieur et infralittoral de lâestran. Sur les autres sites, les deux espĂšces occupaient les niveaux mĂ©diolittoral infĂ©rieur et infralittoral, et les individus de A. marina Ă©taient moins nombreux, et sans recrus. Les pontes de A. marina ont eu lieu en dĂ©but dâautomne et celles de A. defodiens en fin dâautomne. Le besoin de mise en place de mesures de gestion de A. marina a Ă©tĂ© mis en Ă©vidence sur un site en comparant les abondances et les donnĂ©es de pĂȘche. Ensuite, un modĂšle de type Dynamic Energy Budget (DEB) a Ă©tĂ© appliquĂ© Ă A. marina en combinant des donnĂ©es de terrain, des donnĂ©es expĂ©rimentales (de croissance et de consommation dâoxygĂšne) et des donnĂ©es de la littĂ©rature pour reconstruire le cycle de vie et la croissance de lâespĂšce dans des conditions environnementales in situ (De Cubber et al., in press). La reconstruction de la chronologie des premiers stades de vie avec le modĂšle DEB pour A. marina en fonction des conditions environnementales in situ a permis de prĂ©dire une premiĂšre phase de dispersion de 5 jours suivie dâune pĂ©riode dâinstallation temporaire de 7 mois avant une deuxiĂšme phase de dispersion au printemps, Ă la fin de la mĂ©tamorphose, qui semble concorder avec les observations de terrain. Enfin, la structure en taille de la population de A. marina sur un des sites dâĂ©tude a Ă©tĂ© suivie pendant 1.5 an pour explorer les migrations des adultes vers le bas dâestran reportĂ©es par plusieurs auteurs. Pour cela, un modĂšle permettant la reconstruction de la tempĂ©rature au sein du sĂ©diment a Ă©tĂ© adaptĂ© dâun modĂšle de tempĂ©rature pour la vase; le contenu en azote du sĂ©diment a Ă©tĂ© mesurĂ© et diffĂ©rents proxys pour la nourriture ont Ă©tĂ© testĂ©s. Les rĂ©ponses mĂ©taboliques des arĂ©nicoles Ă la nourriture (rĂ©ponse fonctionnelle) et Ă la tempĂ©rature (intervalle de tolĂ©rance et tempĂ©rature dâArrhĂ©nius) ont Ă©tĂ© estimĂ©es. Ces donnĂ©es, combinĂ©es au modĂšle DEB pour A. marina ont permis dâĂ©tudier les effets de variations de la tempĂ©rature et la de nourriture rencontrĂ©s par les arĂ©nicoles suivant leur position sur lâestran et la profondeur de leur galerie. Le suivi de la structure en taille de la population de A. marina a clairement indiquĂ© la prĂ©sence de migration au cours du temps vers le bas dâestran.Arenicola spp. are marine benthic polychaetes displaying a complex bentho-pelagic life cycle with two larval dispersal phases, only partially described up to now, and intensively dug for bait by anglers on many foreshores of the Eastern English Channel. Without regulation, this activity can lead to the decrease of lugwormsâ population while affecting the physical characteristics of the beach and the associated biodiversity. First, we identified through morphology and genetics two species of lugworms, Arenicola marina and A. defodiens, and assessed their abundance and spatial distribution at four studied sites, as well as some life-history traits such as the spawning periods and the size at first maturity. These data were compared to lugwormsâ collection data to estimate its sustainability and to provide potential management measures (De Cubber et al., 2018). At one studied site, A. marina was present in large numbers on the higher and middle shore, whereas A. defodiens occupied the lower shore. At the other sites, both species cooccurred on the lower shore, and A. marina individuals were less numerous and lacking recruits. Spawning periods for A. marina occurred in early autumn and in late autumn for A. defodiens. One site appeared in need for management when linking abundance data with bait collection, where harvest was above the carrying capacity of the beach for A. marina. Second, a Dynamic Energy Budget (DEB) model was applied to the species combining the former as well as new field data, experimental data (growth and oxygen consumption data), and literature data in order to reconstruct the life cycle and growth of A. marina under in situ environmental conditions (De Cubber et al., in press). The reconstruction of the early life-stages chronology by the DEB model for A. marina according to in situ environmental conditions indicated a first dispersal phase of 5 days followed by a 7 monthsâ temporary settlement before a second dispersal phase in spring, at the end of metamorphosis, which appeared consistent with field observations. Finally, we followed-up the population size structure of A. marina at one studied site during 1.5 year to explore the down shore migration of lugworms recorded by several authors. To do so, we adapted a sediment temperature model from a mud temperature model (Guarini et al., 1997), measured the nitrogen content and tested several proxys for the food sources. The metabolic responses of lugworms to food (scaled functional response) and temperature (temperature tolerance range and Arrhenius temperature) were then assessed. We combined those data with the former DEB model to explore the effects of the fine changes in temperature and food conditions met by the individuals along the foreshore gradient and according to the depth of their galleries. The follow-up of the population size structure of A. marina showed clearly a migration pattern. The effect of sediment temperature alone when migrating did not allow significantly higher growth and egg production, while an increase of food concentrations down the shore did. Other factors might be taken in consideration in further studies such as desiccation and anaerobic metabolism during emersion periods at low tide. All these data constitute valuable information for conservation managers to better understand and regulate the lugworm populations. Further combination of the DEB model developed in this study with an individual-based model and a larval dispersal model could enable to understand the dynamics of the local lugworm populations
Annelid polychaetes experience metabolic acceleration as other Lophotrochozoans: inferences on the life cycle of Arenicola marina with a Dynamic Energy Budget model
International audienceArenicola marina is a polychaete (Lophotrochozoan) displaying a complex bentho-pelagic life cycle with two larval dispersal phases, only partially described up to now. A Dynamic Energy Budget (DEB) model was applied to the species in order to reconstruct its life cycle and growth under in situ environmental conditions. Two types of DEB models are usually applied to other Lophotrochozoans displaying similar life cycles: the standard (std-) model, applied to polychaetes (5 entries among the 1524 of the Add-my-Pet database on the 18/10/2018), and the abj-model, which includes an acceleration of metabolism between birth and metamorphosis, and which has been applied to most molluscs (77 abj-entries out of the 80 mollusc entries) enabling better fit predictions for the early life stages. The parameter estimation was performed with both models to assess the suitability of an abj-model for A. marina. The zero-variate dataset consisted of length and age data at different life cycle stages, the lifespan, the maximum observed length, and the wet weight of an egg. The uni-variate dataset consisted of two growth experiments from the literature at two food levels and several temperatures, laboratory data of oxygen consumption at several temperatures, and fecundity for different lengths. The predictions of the abj-model fitted better to the data (SMSEâŻ=âŻ0.29). The acceleration coefficient was ca 11, which is similar to mollusc values. The field growth curves and the scaled functional responses (as a proxy of food levels) were suitably reconstructed with the new parameter set. The reconstruction of the early life-stages chronology according to in situ environmental conditions of a temperate marine ecosystem indicated a first dispersal phase of 5 days followed by a 7 months temporary settlement before a second dispersal phase in spring, at the end of metamorphosis. We emphasize the need for using abj-models for polychaetes in future studies
Linking life-history traits, spatial distribution and abundance of two species of lugworms to bait collection: A case study for sustainable management plan
Arenicola spp. are marine benthic polychaetes dug for bait by anglers. Without regulation, this activity can lead to the decrease of lugworms' population meanwhile affecting the physical characteristics of the beach and the biodiversity. Here, we identified through morphology and genetics two species of lugworms, Arenicola marina and A. defodiens, within a Marine Protected Area of the Eastern English Channel (France). For each species, abundance and spatial distribution were assessed using a stratified random sampling and interpolation at four studied sites, as well as some life-history traits. These data were compared to lugworms' collection data to estimate its sustainability and to provide potential management measures. At one site, A. marina was present in large numbers on the higher and middle shore, whereas A. defodiens occupied the lower shore. At the other sites, both species co-occurred on the lower shore, and A. marina individuals were less numerous and lacking recruits. Spawning periods for A. marina occurred in early autumn and in late autumn for A. defodiens. The size at first maturity of A. marina was at 3.8âŻcm of trunk length (between 1.5 and 2.5 years old). One site (Au) appeared in need for management when linking abundance data with bait collection, where harvest of both species represented âŒ14% of the total amount of lugworms and was above the carrying capacity of the beach for A. marina. The retail value associated to lugworm harvesting within the MPA was estimated at the same level as the shrimp retail value. Our results highlight the need for some fishery regulations
Unravelling mechanisms behind population dynamics, biological traits and latitudinal distribution in two benthic ecosystem engineers: A modelling approach
The mechanistic approach consisting of coupling Dynamic Energy Budget (DEB) models to Individual-BasedModels (IBMs) allows simulating individual and population biological traits and their dynamics. This approachwas developed here to study population dynamics of two sympatric intertidal ecosystem engineers, Arenicolamarina and Arenicola defodiens (Annelida Polychaeta) occurring in the North-East Atlantic from Portugal toSweden. Latitudinal heterogeneity of the two speciesâ performances were investigated in terms of populationdynamics and biological traits using latitudinal differences in environmental forcing variables. The impactof the forcing variables on population dynamics processes (shore colonisation and migration, spawning andrecruitment, etc.) within a specific foreshore (mean values and seasonal patterns) was also assessed. PublishedDEB parameters were used for A. marina and a specific calibration was undertaken for A. defodiens, combiningliterature data and new laboratory experiments and field data. Our DEB-IBM simulated super-individualsâgrowth and reproduction while lugworms were colonising, migrating and dying over a simulated foreshore.Density rules affected population dynamics. Environmental forcings consisted in monthly values of chlorophylla(chl-a) concentrations and daily values of SST. Scenarios focusing on the two most contrasted of theseforcing variables time series were used to explore their relative effects over populationsâ dynamics and onshoreprocesses were investigated at two sites displaying highly different simulated population abundances.Overall, northern sites with higher chl-a levels performed better displaying higher biomass, maximum lengthand reproductive outputs for both species. As expected, Sea Surface Temperature (SST) changes between sitesdid not impact greatly populations dynamics. Under favourable environmental conditions, intra- and interspecificcompetitions emerged from the model. Under non-favourable environmental conditions, A. defodiensâpopulations crashed and A. marina displayed atypical population processes, with rare spawning events barelyallowing the populationâs renewal, and lower size at maturity. Further use and development of this model willlead to better insights on the lugworm populationsâ evolution over the next decades
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 fishâs 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 âmetabolic accelerationâ 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 fishâs 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 âmetabolic accelerationâ 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
Robust identification of potential habitats of a rare demersal species (blackspot seabream) in the Northeast Atlantic
Species distribution models (SDM) are commonly used to identify potential habitats. When fitting them to heterogeneous, opportunistically collated presence/absence data, imbalance in the number of presence and absence observations often occurs, which could influence results. To robustly identify potential habitats for blackspot seabream (Pagellus bogaraveo) throughout its distribution area in the Northeast Atlantic and the western Mediterranean Sea, we used an ensemble species distribution modelling (eSDM) approach, modelling gridded presenceâabsence data with environmental predictors for two types of occurrence data sets. The first data set displayed the observed unbalanced spatially heterogeneous presence/absence ratio and the second a balanced presence/absence ratio. The data covered the full distribution area, including the European Atlantic shelf, the Azorean region and the Western Mediterranean Sea. Across these regions, populations display variable status. The main environmental predictors for potential habitats were bathymetry and annual maximum SST. The fitted ensemble compromise (eSDM) was projected over the whole grid to create a habitat suitability map. This map exhibited higher probabilities of presence for the balanced-ratio data set. A binary presenceâabsence map was then generated using optimized presence probability thresholds for four validation indices. Using the true skill statistic to optimize the threshold, the surface areas of the binary presenceâabsence map was 53% smaller for the balanced data set than for the observed unbalanced data set. However, the choice of validation index had an even greater impact (up to 15 000%). This indicates that studies using opportunistic data for SDM fitting need to pay attention to the effects of presence/absence data imbalance and the choice of validation index to fully evaluate uncertainty. © 2022 Elsevier B.V. All rights reserved.The study received financial support from France FiliĂšre PĂȘche (project DynRose) and the European Unionâs Horizon 2020 research and innovation programme under Grant Agreement No 773713 (PANDORA).Pagellus bogaraveo; Species distribution models; Ensemble modelling; Heterogeneous data set; Presenceâabsence imbalancePeer reviewe
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 fishâs 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 âmetabolic accelerationâ 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 fishâs 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 âmetabolic accelerationâ 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