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Auteur Carlier, A.; Chauvaud, L.; van der Geest, M.; Le Loc’h, F.; Le Duff, M.; Vernet, M.; Raffray, J.; Diakhaté, D.; Labrosse, P.; Wagué, A.; Le Goff, C.; Gohin, F.; Chapron, B.; Clavier, J. url  doi
openurl 
  Titre Trophic connectivity between offshore upwelling and the inshore food web of Banc d’Arguin (Mauritania): new insights from isotopic analysis Type Article scientifique
  Année 2015 Publication Revue Abrégée Estuarine, Coastal and Shelf Science  
  Volume 165 Numéro Pages (down) 149-158  
  Mots-Clés Banc d’Arguin West Africa food web structure remote sensing stable isotope upwelling  
  Résumé Banc d’Arguin (BA), Mauritania, is a nationally protected shallow gulf > 10,000 km2 between the Sahara desert and the upwelling system off the Mauritanian coast. In the southeast, BA consists of a 500 km2 tidal flat, the most important wintering site for shorebirds using the East Atlantic Flyway. The Mauritanian upwelling-driven phytoplankton production supports the most productive fisheries worldwide, but little is known about its trophic role in the functioning of the inshore BA food web. Using stable isotopes as trophic tracers to distinguish between upwelling-driven phytoplankton, open ocean phytoplankton, and benthic primary producers, we assessed the spatial extent to which the inshore BA food web is fuelled by upwelling-driven phytoplankton production. The δ13C and δ15N signals were characterized in dominant primary producers, benthic invertebrate taxa, and various fish species along an offshore–inshore (northwest–southeast) gradient. We also monitored the spatial and temporal extent of upwelling entering BA during 2008 with remote sensing of sea surface temperature and chlorophyll a data. The results suggest that benthic invertebrates and fishes living in the northwestern part of BA depend on the nearby upwelling phytoplankton production, but this food source does not support the intertidal benthic community in southeast BA. Furthermore, the isotopic signatures of fishes suggest weak trophic connectivity between the northern subtidal and southeastern intertidal BA. Our results support the hypothesis that the southeastern tidal flat region functions as a distinct ecosystem with a food web supported mainly by local benthic primary production, which is crucial knowledge for effective management of the pristine BA national park.  
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  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0272-7714 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ 1417 collection 1367  
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Auteur Hampton, S.L.; Moloney, C.L.; van der Lingen, C.D.; Labonne, M. doi  openurl
  Titre Spatial and temporal variability in otolith elemental signatures of juvenile sardine off South Africa Type Article scientifique
  Année 2018 Publication Revue Abrégée J. Mar. Syst.  
  Volume 188 Numéro Pages (down) 109-116  
  Mots-Clés anchovy; challenges; chemistry; fingerprints; fish; Microchemistry; Otoliths; protein; salinity; Sardine; Stock structure; stocks; temperature; Upwelling; water  
  Résumé Otolith elemental signatures can be used to identify when individual or groups of fish are spending a significant amount of time in different environments. Elemental signatures of juvenile sardine Sardinops sagax caught in winter 2008 and 2009 around the coast of South Africa were measured using inductively-coupled plasma mass-spectroscopy. The otolith elemental signatures of 34 fish caught in 2008 and of 52 fish caught in 2009 were measured at the edge (to represent conditions 20-30 days prior to capture). Principal component analysis was used to visualise the relationships of individuals to each other, in terms of their otolith chemistry, in two-dimensional space, and multiple ANOVAs were used to investigate spatial and temporal variations among samples collected in 2008 and 2009. Significant differences among sites were found in MANOVAs, but the between-site differences varied among the elements. Magnesium concentration tended to decrease whereas barium concentration tended to increase from the west to the east coast. Barium indicate upwelling impact but for 2008 samples on the northern part of the west coast. Otolith microchemistry provides evidence of large and small-scale differentiation in sardine, but differences between years indicates that this is not necessarily temporally stable. The ocean off South Africa is a dynamic and variable environment and this is reflected in the inter-site, and also inter-annual, differences in elemental signatures of juvenile sardine.  
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  Langue English Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0924-7963 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ collection 2448  
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Auteur Travers, M.; Watermeyer, K.; Shannon, L.J.; Shin, Y.-J. url  doi
openurl 
  Titre Changes in food web structure under scenarios of overfishing in the southern Benguela : comparison of the Ecosim and OSMOSE modelling approaches Type Article scientifique
  Année 2010 Publication Revue Abrégée Journal of Marine Systems  
  Volume 79 Numéro Pages (down) 101-111  
  Mots-Clés and; Benguela; ecosystem; Fishing; Food; function; indicators; model; structure; Trophic; upwelling; web  
  Résumé Ecosystem models provide a platform allowing exploration into the possible responses of marine food webs to fishing pressure and various potential management decisions. In this study we investigate the particular effects of overfishing on the structure and function of the southern Benguela food web, using two models with different underlying assumptions: the spatialized, size-based individual-based model, OSMOSE, and the trophic mass-balance model, Ecopath with Ecosim (EwE). Starting from the same reference state of the southern Benguela upwelling ecosystem during the 1990s, we compare the response of the food web to scenarios of overfishing using these two modelling approaches. A scenario of increased fishing mortality is applied to two distinct functional groups: i) two species of Cape hake, representing important target predatory fish, and ii) the forage species anchovy, sardine and redeye. In these simulations, fishing mortality on the selected functional groups is doubled for 10 years, followed by 10 years at the initial fishing mortality. We compare the food web states before the increase of fishing mortality, after 10 years of overfishing and after a further 10 years during which fishing was returned to initial levels. In order to compare the simulated food web structures with the reference state, and between the two modelling approaches, we use a set of trophic indicators: the mean trophic level of the community and in catches, the trophic pyramid (biomass per discrete trophic level), and the predatory/forage fish biomass ratio. OSMOSE and EwE present globally similar results for the trophic functioning of the ecosystem under fishing pressure: the biomass of targeted species decreases whereas that of their potential competitors increases. The reaction of distant species is more diverse, depending on the feeding links between the compartments. The mean trophic level of the community does not vary enough to be used for assessing ecosystem impacts of fishing, and the mean trophic level in the catch displays a surprising increase due to the short period of overfishing. The trophic pyramids behave in an unexpected way compared to trophic control theory. because at least two food chains with different dynamics are intertwined within the food web. We emphasize the importance of biomass information at the species level for interpreting dynamics in aggregated indicators, and we highlight the importance of competitive groups when looking at ecosystem functioning under fishing disturbance. Finally, we discuss the results within the scope of differences between models, in terms of the way they are formulated, spatial dimensions, predation formulations and the representation of fish life cycles.  
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  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0924-7963 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 111  
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Auteur Brochier, T.; Lett, C.; Freon, P. url  doi
openurl 
  Titre Investigating the “northern Humboldt paradox” from model comparisons of small pelagic reproductive strategies in eastern boundary upwelling ecosystems Type Article scientifique
  Année 2011 Publication Revue Abrégée Fish and Fisheries  
  Volume Numéro Pages (down) 94-109  
  Mots-Clés Benguela; Californie; Canaries; comparative; Courant; De; Espece; estimation; Etude; Humboldt; Impact; L'Environnement; Marin; Pelagique; Poisson; Reproduction; Stock; upwelling  
  Résumé  
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  Auteur institutionnel Thèse  
  Editeur Lieu de Publication Éditeur  
  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1467-2979 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 124  
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Auteur Ortega-Cisneros, K.; Shannon, L.; Cochrane, K.; Fulton, E. A.; Shin, Y.-J. url  doi
openurl 
  Titre Evaluating the specificity of ecosystem indicators to fishing in a changing environment: A model comparison study for the southern Benguela ecosystem Type Article scientifique
  Année 2018 Publication Revue Abrégée Ecological Indicators  
  Volume 95 Numéro Pages (down) 85-98  
  Mots-Clés Ecosystem models; Environmental change; Fishing; Indicators; Specificity; Upwelling  
  Résumé Ecological indicators used to monitor fishing effects in the context of climate change and variability need to be informative to enable effective ecosystem-based fisheries management. We evaluated the specificity of the response of ecosystem indicators to different fishing and environmental pressure levels using Ecosim and Atlantis ecosystem models for the southern Benguela ecosystem. Three fishing strategies were modelled to represent a variety of ways of targeting fishing within an ecosystem: one focused on low trophic levels (i.e. forage species), another on higher trophic levels (i.e. predatory fish) and a third tested fishing pressure across the full range of potentially exploitable species. Two types of environmental change were simulated for each fishing mortality scenario – random environmental variability and directional climate change. The specificity of selected ecological indicators (mean trophic level of the community, proportion of predatory fish, biomass/landings, mean intrinsic vulnerability and marine trophic index) was evaluated for different combinations of fishing strategy, fishing mortality and both types of environmental change. While there were mostly large differences in indicator values computed from the Atlantis and Ecosim models, the specificity of the ecological indicators considered under changing climate generally corresponded between the two models. Certain indicators (i.e. mean trophic level of the community) were less specific in detecting effects of fishing in the southern Benguela for some of the three fishing strategies modelled (i.e. high trophic level fishing strategy) under climate change. This helped refine the most appropriate indicator set for our system, reflecting the focus of a particular fishing strategy, and improved confidence in the suitability of these indicators for monitoring fishing effects in the Southern Benguela.  
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  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1470-160x ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2402  
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