|
|
|
| Registros recuperados: 16 | |
|
|
| Diankha, Ousmane; Ba, Aliou; Brehmer, Patrice; Brochier, Timothee; Sow, Bamol Ali; Thiaw, Modou; Gaye, Amadou Thierno; Ngom, Fambaye; Demarcq, Herve. |
| We investigate Sardinella aurita and Sardinella maderensis recruitment success relative to the variability of oceanographic conditions in Senegalese waters using generalized additive models (GAM). Results show that recruitment of both species is marked by a strong intra-annual (seasonal) variation with minimum and maximum in winter and summer, respectively. Their interannual variations are synchronous until 2006 (recruitment decreasing), while from 2007 there is no synchrony. The model developed shows that sardinella recruitment variability is closely related to the tested environmental variables in the study area. However, the key environmental variables influencing the recruitment success are different for both species: the Coastal Upwelling Index and... |
| Tipo: Text |
Palavras-chave: Recruitment success; Sardinella aurita; Sardinella maderensis; Upwelling; West Africa. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00611/72299/71189.pdf |
| |
|
|
| Bauer, Robert; Fromentin, Jean-marc; Demarcq, Herve; Brisset, Blandine; Bonhommeau, Sylvain. |
| Different dolphin and tuna species have frequently been reported to aggregate in areas of high frontal activity, sometimes developing close multi-species associations to increase feeding success. Aerial surveys are a common tool to monitor the density and abundance of marine mammals, and have recently become a focus in the search for methods to provide fisheries-independent abundance indicators for tuna stock assessment. In this study, we present first density estimates corrected for availability bias of fin whales (Balaenoptera physalus) and striped dolphins (Stenella coeruleoalba) from the Golf of Lions (GoL), compared with uncorrected estimates of Atlantic bluefin tuna (ABFT; Thunnus thynnus) densities from 8 years of line transect aerial surveys. The... |
| Tipo: Text |
|
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00284/39481/37969.pdf |
| |
|
|
| Nieblas, Anne-elise; Drushka, Kyla; Reygondeau, Gabriel; Rossi, Vincent; Demarcq, Herve; Dubroca, Laurent; Bonhommeau, Sylvain. |
| The Mediterranean and Black Seas are semi-enclosed basins characterized by high environmental variability and growing anthropogenic pressure. This has led to an increasing need for a bioregionalization of the oceanic environment at local and regional scales that can be used for managerial applications as a geographical reference. We aim to identify biogeochemical subprovinces within this domain, and develop synthetic indices of the key oceanographic dynamics of each subprovince to quantify baselines from which to assess variability and change. To do this, we compile a data set of 101 months (2002-2010) of a variety of both "classical'' (i.e., sea surface temperature, surface chlorophyll-a, and bathymetry) and "mesoscale'' (i.e., eddy kinetic energy,... |
| Tipo: Text |
|
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00239/34995/33536.pdf |
| |
|
|
| Barbraud, Christophe; Bertrand, Arnaud; Bouchon, Marilu; Chaigneau, Alexis; Delord, Karine; Demarcq, Herve; Gimenez, Olivier; Gutierrez Torero, Mariano; Gutierrez, Dimitri; Oliveros Ramos, Ricardo; Passuni, Giannina; Tremblay, Yann; Bertrand, Sophie. |
| In marine ecosystems top predator populations are shaped by environmental factors affecting their prey abundance. Coupling top predators' population studies with independent records of prey abundance suggests that prey fluctuations affect fecundity parameters and abundance of their predators. However, prey may be abundant but inaccessible to their predators and a major challenge is to determine the relative importance of prey accessibility in shaping seabird populations. In addition, disentangling the effects of prey abundance and accessibility from the effects of prey removal by fisheries, while accounting for density dependence, remains challenging for marine top predators. Here, we investigate how climate, population density, and the accessibility and... |
| Tipo: Text |
|
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56117/57647.pdf |
| |
|
|
| Roa Pascuali, Liliana; Demarcq, Herve; Nieblas, Anne-elise. |
| In order to optimize frontal detection in sea surface temperature fields at 4 km resolution, a combined statistical and expert-based approach is applied to test different spatial smoothing of the data prior to the detection process. Fronts are usually detected at 1 km resolution using the histogram-based, single image edge detection (SIED) algorithm developed by Cayula and Cornillon in 1992, with a standard preliminary smoothing using a median filter and a 3 × 3 pixel kernel. Here, detections are performed in three study regions (off Morocco, the Mozambique Channel, and north-western Australia) and across the Indian Ocean basin using the combination of multiple windows (CMW) method developed by Nieto, Demarcq and McClatchie in 2012 which improves on the... |
| Tipo: Text |
Palavras-chave: Mesoscale thermal fronts; Preliminary smoothing; Sea surface temperature; 4 km resolution; Gradient intensity classification; Expert-based approach; Detection efficiency; Indian Ocean. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00269/37998/42023.pdf |
| |
|
|
| Demarcq, Herve. |
| Les images satellitaires fournissent une vue synoptique de la zone d'étude, difficilement réalisable à partir des moyens de prospection à la mer. De plus, la répétitivité des observations à partir de l'espace, de l'ordre de quelques jours, ou moins, permet d'étudier l'évolution spatio-temporelle, souvent rapide, des phénomènes marins observés. Ces caractéristiques de la mesure satellitaire ont été exploitées pour mettre en évidence quelques phénomènes dynamiques et biologiques se déroulant en Méditerranée nord-occidentale, et plus particulièrement dans le golfe du Lion. |
| Tipo: Text |
|
| Ano: 1985 |
URL: http://archimer.ifremer.fr/doc/00105/21644/19225.pdf |
| |
|
|
| 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 |
| |
|
|
| Bauer, Robert Klaus; Fromentin, Jean-marc; Demarcq, Herve; Bonhommeau, Sylvain. |
| We investigated the habitat utilization, vertical and horizontal behaviour of Atlantic bluefin tuna Thunnus thynnus (ABFT) in relation to oceanographic conditions in the northwestern Mediterranean Sea, based on 36 pop-up archival tags and different environmental data sets. Tags were deployed on early mature ABFT (127–255 cm) between July and November in 2007-2014, on the shelf area off Marseille, France. The data obtained from these tags provided 1643 daily summaries of ABFT vertical behaviour over 8 years of tag deployment. Based on a hierarchical clustering of this data, we could identify four principle daily vertical behaviour types, representing surface (≦10m) and subsurface (10–100 m) orientation, moderate (50–200 m) and deep (≧200m) diving behaviour.... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Habitat use; Spike dives; Fronts; Thermal stratification; Archival tags. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00382/49329/49709.pdf |
| |
|
|
| Vianello, Patrick; Ternon, Jean-francois; Demarcq, Herve; Herbette, Steven; Roberts, Michael J.. |
| This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Pérouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20°S and 33°S, some 1500 km. The study provides the background oceanography for the once-off, multidisciplinary snapshot cruise studies around the seamounts. As life on seamounts is determined by factors such as summit depth, proximity to the light layers of the ocean, and the ambient circulation, a first description of regional spatial-field climatologies (16–22 years) and monthly... |
| Tipo: Text |
Palavras-chave: South West Indian Ocean; Madagascar Ridge; Seamounts; Walters shoal; Sea surface temperature; Eddy kinetic energy; Mixed layer depth; Chlorophyll-a; Geostrophic currents. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00634/74581/74476.pdf |
| |
|
|
| Diogoul, Ndague; Brehmer, Patrice; Demarcq, Herve; El Ayoubi, Salaheddine; Thiam, Abou; Sarre, Abdoulaye; Mouget, Anne; Perrot, Yannick. |
| The resistance of an east border upwelling system was investigated using relative index of marine pelagic biomass estimates under a changing environment spanning 20-years in the strongly exploited southern Canary Current Large marine Ecosystem (sCCLME). We divided the sCCLME in two parts (north and south of Cap Blanc), based on oceanographic regimes. We delineated two size-based groups (“plankton” and “pelagic fish”) corresponding to lower and higher trophic levels, respectively. Over the 20-year period, all spatial remote sensing environmental variables increased significantly, except in the area south of Cap Blanc where sea surface Chlorophyll-a concentrations declined and the upwelling favorable wind was stable. Relative index of marine pelagic... |
| Tipo: Text |
|
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00676/78789/81019.pdf |
| |
|
|
| Mannocci, Laura; Forget, Fabien; Travassos Tolotti, Mariana; Bach, Pascal; Bez, Nicolas; Demarcq, Herve; Kaplan, David; Sabarros, Philippe; Simier, Monique; Capello, Manuela; Dagorn, Laurent. |
| Fisheries observer programs represent the most reliable way to collect data on fisheries bycatch. However, their limited coverage leads to important data gaps that preclude bycatch mitigation at the basin scale. Habitat models developed from available fisheries observer programs offer a potential solution to fill these data gaps. We focus on tropical tuna purse seine fisheries (TTPSF) that span across the tropics and extensively rely on floating objects (FOBs) for catching tuna schools, leading to the bycatch of other species associated with these objects. Bycatch under floating objects is dominated by five species, including the vulnerable silky shark Carcharhinus falciformis and four bony fishes (oceanic triggerfish Canthidermis maculata, rainbow runner... |
| Tipo: Text |
Palavras-chave: Bycatch; Habitat modelling; Hotspots; Fisheries observer programs; Geographical extrapolation; Tropical oceans. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00662/77385/78986.pdf |
| |
|
|
| Chassot, Emmanuel; Bonhommeau, Sylvain; Reygondeau, Gabriel; Nieto, Karen; Polovina, Jeffrey J.; Huret, Martin; Dulvy, Nicholas K.; Demarcq, Herve. |
| Satellite remote sensing (SRS) of the marine environment has become instrumental in ecology for environmental monitoring and impact assessment, and it is a promising tool for conservation issues. In the context of an ecosystem approach to fisheries management (EAFM), global, daily, systematic, high-resolution images obtained from satellites provide a good data source for incorporating habitat considerations into marine fish population dynamics. An overview of the most common SRS datasets available to fishery scientists and state-of-the-art data-processing methods is presented, focusing on recently developed techniques for detecting mesoscale features such as eddies, fronts, filaments, and river plumes of major importance in productivity enhancement and... |
| Tipo: Text |
Palavras-chave: Ecosystem approach; Fisheries; Mesoscale; Satellite; Tracking. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14188/11468.pdf |
| |
|
|
| Marsac, Francis; Galletti, Florence; Ternon, Jean-francois; Romanov, Evgeny V.; Demarcq, Herve; Corbari, Laure; Bouchet, Philippe; Roest, Walter; Jorry, Stephan; Olu, Karine; Loncke, Lies; Roberts, Michael J.; Ménard, Frédéric. |
| There is a growing interest in the management of seamounts of the South Western Indian Ocean (SWIO) both in waters under national jurisdictions and in the Areas Beyond National Jurisdiction (ABNJ). On the one hand, new scientific knowledge has been gathered through various oceanographic cruises during the past decade and, on the other hand, new agreements are under consideration globally to promote conservation and sustainable use of the biodiversity in the ABNJ, where the deep sea ecosystems associated to seamounts are a growing matter of concern. SWIO seamounts have attracted interests from fishing operators since the 1960s, while mining exploration contracts have been recently granted. Seamounts are known to shelter rich, fragile and poorly resilient... |
| Tipo: Text |
Palavras-chave: International Law of the Sea; Vulnerable Marine Ecosystems; Deep-sea fisheries; Deep-sea mining; Benthic biodiversity; Saya de Malha Bank; South Indian Ocean Fisheries Agreement; Areas Beyond National Jurisdiction; Amended Nairobi Convention; Marine protected areas. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00598/71049/69362.pdf |
| |
|
|
| Passuni, Giannina; Barbraud, Christophe; Chaigneau, Alexis; Demarcq, Herve; Ledesma, Jesus; Bertrand, Arnaud; Castillo, Ramiro; Perea, Angel; Mori, Julio; Viblanc, Vincent A.; Torres-maita, Jose; Bertrand, Sophie. |
| In fluctuating environments, matching breeding timing to periods of high resource availability is crucial for the fitness of many vertebrate species, and may have major consequences on population health. Yet, our understanding of the proximate environmental cues driving seasonal breeding is limited. This is particularly the case in marine ecosystems, where key environmental factors and prey abundance and availability are seldom quantified. The Northern Humboldt Current System (NHCS) is a highly productive, low-latitude ecosystem of moderate seasonality. In this ecosystem, three tropical seabird species (the Guanay Cormorant Phalacrocorax bougainvillii, the Peruvian Booby Sula variegata, and the Peruvian Pelican Pelecanus thagus) live in sympatry and prey... |
| Tipo: Text |
Palavras-chave: Anchovy; Engraulis ringens; Guanay Cormorant; Northern Humboldt Current System; Occupancy model; Oceanographic variability; Pelecanus thagus; Peru; Peruvian Booby; Peruvian Pelican; Phalacrocorax bougainvillii; Prey abundance; Seasonal breeding; Sula variegata. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00317/42844/74394.pdf |
| |
|
|
| Kide, Saikou Oumar; Mante, Claude; Dubroca, Laurent; Demarcq, Herve; Merigot, Bastien. |
| Environmental changes and human activities can have strong impacts on biodiversity and ecosystem functioning. This study investigates how, from a quantitative point of view, simultaneously both environmental and anthropogenic factors affect species composition and abundance of exploited groundfish assemblages (i.e. target and non-target species) at large spatio-temporal scales. We aim to investigate (1) the spatial and annual stability of groundfish assemblages, (2) relationships between these assemblages and structuring factors in order to better explain the dynamic of the assemblages’ structure. The Mauritanian Exclusive Economic Zone (MEEZ) is of particular interest as it embeds a productive ecosystem due to upwelling, producing abundant and diverse... |
| Tipo: Text |
|
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00288/39945/38493.pdf |
| |
|
|
| Diankha, Ousmane; Demarcq, Herve; Fall, Massal; Thiao, Djiga; Thiaw, Modou; Sow, Bamol Ali; Gaye, Amadou Thierno; Brehmer, Patrice. |
| This study investigated variations of landings of two key species, Sardinella aurita and Sardinella maderensis, in Senegalese waters over a ten-year period (2004-2013). Using generalized additive models, it was found that fishing gear played a major role in explaining differences in monthly landings for both species (51-71% deviance explained). Its effect was more significant in the southern part of Senegal. Fishing effort (number of trips) accounted only for 4-18% of variability in landings. Purse seine (PS) fishing was the most important contributor to the landings of both species. In addition, in the southern area, surrounding gillnet fishing was also important for S. maderensis. Modeling results showed that the relationship between monthly effort and... |
| Tipo: Text |
Palavras-chave: Effects of fishing; Generalized additive model; Sardinella aurita; Sardinella maderensis; Purse seine; Surrounding gillnet; Senegal. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00616/72808/72585.pdf |
| |
| Registros recuperados: 16 | |
|
|
|
