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Registros recuperados: 5
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Couplage de modèles trophiques et effets combinés de la pêche et du climat ArchiMer
Travers, Morgane.
Overfishing and climate change are now recognized to have important effects on marine ecosystem functioning but uncertainties remains about their combined effects. Using a modelling approach this thesis aims at assessing how the top-down effects of fishing and the bottom-up effects of climate combine themselves within the food web. A preliminary review highlighted the lack of end-to-end model applicable as it stands to our study case - the southern Benguela - and suitable to study the combined effects of fishing and climate. Coupling the plankton model ROMS-N2P2Z2D2 and the fish model OSMOSE appeared as an innovative method allowing to develop an appropriate tool meeting our objectives. The importance of two-way coupling via the predation process is first...
Tipo: Text Palavras-chave: Modèle end-to-end; Couplage de modèle; Réseau trophique; Sud- Benguela; Effets combinés; Changement climatique; Surexploitation; End-to-end model; Model coupling; Food web; Southern Benguela; Combined effects; Climate change; Overfishing.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00003/11445/7993.pdf
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EcoTroph: a simple model to assess fishery interactions and their impacts on ecosystems ArchiMer
Gasche, Loic; Gascuel, Didier.
The EcoTroph model leaves aside the notion of species, and models the functioning of marine ecosystems as flows of biomass from low to high trophic levels, so as to quantify easily the impacts of fishing at an ecosystem scale. In this paper, based on two case studies we present a new development of the EcoTroph model that is devoted to the analysis of fishery interactions and impacts of fleet segments on ecosystems. First, deriving an EcoTroph model from an Ecopath model of the Guinea ecosystem, the impacts of the artisanal fishery are distinguished from those of the industrial fishery. It appears that these fisheries do not always compete for the same fish groups but that they both strongly impact the ecosystem and moderately impact one another. Then, an...
Tipo: Text Palavras-chave: Ecopath; Ecosystem modelling; EcoTroph; Fishery interactions; Fishing impact; Guinea; Management scenario; Small pelagics; Southern Benguela.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00138/24970/23123.pdf
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Fine-scale recognition and use of mesoscale fronts by foraging Cape gannets in the Benguela upwelling region ArchiMer
Sabarros, Philippe S.; Gremillet, David; Demarcq, Herve; Moseley, Christina; Pichegru, Lorien; Mullers, Ralf H. E.; Stenseth, Nils C.; Machu, Eric.
Oceanic structures such as mesoscale fronts may become hotspots of biological activity through concentration and enrichment processes. These fronts generally attract fish and may therefore be targeted by marine top-predators. In the southern Benguela upwelling system, such fronts might be used as environmental cues by foraging seabirds. In this study we analyzed high-frequency foraging tracks (GPS, 1 s sampling) of Cape gannets Morus capensis from two colonies located on the west and east coast of South Africa in relation to mesoscale fronts detected on daily high-resolution chlorophyll-a maps (MODIS, 1 km). We tested the association of (i) searching behavior and (ii) diving activity of foraging birds with mesoscale fronts. We found that Cape gannets shift...
Tipo: Text Palavras-chave: Seabird; Environmental cue; Behavioral shift; Area-restricted search; Feeding activity; Fractal landscape; Oceanographic fronts; Morus capensis; Southern Benguela; South Africa.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00236/34756/34575.pdf
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Long-term, Ecosystem-Scale Changes in the Southern Benguela Marine Pelagic Social-Ecological System: Interaction of Natural and Human Drivers Ecology and Society
Jarre, Astrid; Marine Research Institute, University of Cape Town, South Africa; ajarre@gmail.com; Ragaller, Sven M.; Marine Research Institute, University of Cape Town, South Africa; sven.ragaller@gmail.com; Hutchings, Laurence; Marine Research Institute, University of Cape Town, South Africa; larry.hutchings@gmail.com.
South Africa's small pelagics fishery is currently the largest in volume and second largest in value in the southern Benguela. It exploits short-lived, small pelagic fishes such as anchovy (for reduction into fish meal and oil) and sardine (for reduction as well as human consumption through canned products), and to a lesser extent redeye round herring and mesopelagics, largely for reduction. We explore the recent history (1940s to present) of the social-ecological system around this fishery. The natural subsystem, at the scales of the ocean environment and the ecosystem, is characterized by high interannual and documented decadal-scale variability. We characterize the human social subsystem at the scales of the fishing industry, legislation, and west...
Tipo: Peer-Reviewed Reports Palavras-chave: Anchovy; Coastal communities; Inshore fishery; Marine social-ecological systems; Purse seining; Rock lobster; Small pelagic fishery; South Africa; Southern Benguela; Sardine.
Ano: 2013
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Shelf-edge jet currents in the southern Benguela: a modelling approach ArchiMer
Veitch, Jennifer; Hermes, Juliet; Lamont, Tarron; Penven, Pierrick; Dufois, Francois.
The dynamics and seasonal variability of jet currents on the southern Benguela shelf-edge are investigated using a climatologically forced ROMS model. The jet is primarily forced by the intense horizontal gradients that exist across the southern Benguela shelf. These gradients are set up by nearshore cooling via the strongly seasonal upwelling regime and variable offshore warming by the advection of Agulhas waters. While the nearshore cooling is prevalent only during the spring and summer upwelling season, the offshore warming exists throughout the year. As a result intensified geostrophically adjusted currents exist throughout the year, particularly off the Cape Peninsula and Cape Columbine. However, the distinct shelf-edge jet features are most intense...
Tipo: Text Palavras-chave: Southern Benguela; Shelf-edge jet; Numerical model.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00403/51401/51976.pdf
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