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Auteur Saulquin, B.; Fablet, R.; Mercier, G.; Demarcq, H.; Mangin, A.; d' Andon, O.H.F. url  doi
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  Titre Multiscale Event-Based Mining in Geophysical Time Series: Characterization and Distribution of Significant Time-Scales in the Sea Surface Temperature Anomalies Relatively to ENSO Periods from 1985 to 2009 Type Article scientifique
  Année 2014 Publication Revue Abrégée IEEE J. Sel. Top. Appl. Earth Observ. Remote Sens.  
  Volume 7 Numéro 8 Pages 3543-3552  
  Mots-Clés algorithm; climate-change; Distribution of the sea surface temperature anomalies events related to the ENSO periods; event-based mining in large geophysical datasets (big data); frequency; geophysical time series as series of significant time-scale events; models; monsoon variability; ocean; pacific; patterns; predictability; wavelet analysis  
  Résumé In this paper, one-dimensional (1-D) geophysical time series are regarded as series of significant time-scale events. We combine a wavelet-based analysis with a Gaussian mixture model to extract characteristic time-scales of 486 144 detected events in the Sea Surface Temperature Anomaly (SSTA) observed from satellite at global scale from 1985 to 2009. We retrieve four low-frequency characteristic time-scales of Nino Southern Oscillation (ENSO) in the 1.5- to 7-year range and show their spatial distribution. High-frequency (HF) SSTA event spatial distribution shows a dependency to the ENSO regimes, pointing out that the ENSO signal also involves specific signatures at these time-scales. These fine-scale signatures can hardly be retrieved from global EOF approaches, which tend to exhibit uppermost the low-frequency influence of ENSO onto the SSTA. In particular, we observe at global scale a major increase by 11% of the number of SSTA HF events during Nino periods, with a local maximum of 80% in Europe. The methodology is also used to highlight an ENSO-induced frequency shift during the major 1997-2000 ENSO event in the intertropical Pacific. We observe a clear shift from the high frequencies toward the 3.36-year scale with a maximum shift occurring 2 months before the ENSO maximum of energy at 3.36-year scale.  
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  Langue English Langue du Résumé Titre Original  
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  Volume de collection Numéro de collection Edition  
  ISSN 1939-1404 ISBN Médium  
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Auteur Sabarros, P.S.; Grémillet, D.; Demarcq, H.; Moseley, C.; Pichegru, L.; Mullers, R.H.E.; Stenseth, N.C.; Machu, E. url  doi
openurl 
  Titre Fine-scale recognition and use of mesoscale fronts by foraging Cape gannets in the Benguela upwelling region Type Article scientifique
  Année 2014 Publication Revue Abrégée Deep Sea Research Part II: Topical Studies in Oceanography  
  Volume Numéro Pages 77-84  
  Mots-Clés Area-restricted search; Behavioral shift; Environmental cue; Feeding activity; Fractal landscape; Morus capensis; Oceanographic fronts; seabird; South Africa; southern Benguela  
  Résumé 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 from transiting to area-restricted search mode (ARS) at a distance from fronts ranging between 2 and 11 km (median is 6.7 km). This suggests that Cape gannets may be able to sense fronts (smell or vision) or other predators, and that such detection triggers an intensified investigation of their surroundings (i.e. ARS). Also we found that diving probability increases near fronts in 11 out of 20 tracks investigated (55%), suggesting that Cape gannets substantially use fronts for feeding; in the remaining cases (45%), birds may have used other cues for feeding including fishing vessels, particularly for gannets breeding on the west coast. We demonstrated in this study that oceanographic structures such as mesoscale fronts are important environmental cues used by a foraging seabird within the rich waters of an upwelling system. There is now need for further investigations on how Cape gannets actually detect these fronts.  
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  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Fronts, Fish and Top Predators Titre de collection Abrégé  
  Volume de collection 107 Numéro de collection Edition  
  ISSN 0967-0645 ISBN Médium  
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Auteur Rishworth, G.M.; Tremblay, Y.; Green, D.B.; Pistorius, P.A. url  doi
openurl 
  Titre An automated approach towards measuring time-activity budgets in colonial seabirds Type Article scientifique
  Année 2014 Publication Revue Abrégée Methods Ecol Evol  
  Volume 5 Numéro 9 Pages 854-863  
  Mots-Clés automated monitoring; Bioindicator; Cape gannet; foraging effort; very high frequency  
  Résumé * Seabird proxies have the potential to act as useful and cost-effective indicators of the state of the marine environment. Seabird time-activity budgets, in particular, reflect short-term changes in prey conditions. * We tested an automated technique for long-term continuous recording of Cape gannet, Morus capensis, time-activity budgets using coded very high frequency (VHF) transmitters allowing for simultaneous monitoring of a large sample of study birds. * Radiotransmitters attached to leg-rings had no impact on adult foraging trip and nest attendance durations, breeding success or chick growth. Furthermore, frequencies of nest attendance and foraging trip durations estimated by the VHF logging system were no different to those estimated from hourly direct observations. * Using time-depth recorders, the relationship between the time that birds rested on the sea surface in relation to foraging trip duration was assessed. Trip duration during chick rearing was clearly an accurate proxy for foraging effort. * The VHF monitoring system provides a simple method of accurately assessing the time-activity budgets of colonial seabirds, which can be expanded to a range of other colonially breeding taxa. In the case of seabirds, this approach can potentially provide sensitive, real-time indicators of prey abundance for fisheries management.  
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  Volume de collection Numéro de collection Edition  
  ISSN 2041-210x ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 1203  
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Auteur Rishworth, G.M.; Tremblay, Y.; Green, D.B.; Connan, M.; Pistorius, P.A. url  doi
openurl 
  Titre Drivers of Time-Activity Budget Variability during Breeding in a Pelagic Seabird Type Article scientifique
  Année 2014 Publication Revue Abrégée PLoS ONE  
  Volume 9 Numéro 12 Pages  
  Mots-Clés  
  Résumé During breeding, animal behaviour is particularly sensitive to environmental and food resource availability. Additionally, factors such as sex, body condition, and offspring developmental stage can influence behaviour. Amongst seabirds, behaviour is generally predictably affected by local foraging conditions and has therefore been suggested as a potentially useful proxy to indicate prey state. However, besides prey availability and distribution, a range of other variables also influence seabird behavior, and these need to be accounted for to increase the signal-to-noise ratio when assessing specific characteristics of the environment based on behavioural attributes. The aim of this study was to use continuous, fine-scale time-activity budget data from a pelagic seabird (Cape gannet, Morus capensis) to determine the influence of intrinsic (sex and body condition) and extrinsic (offspring and time) variables on parent behaviour during breeding. Foraging trip duration and chick provisioning rates were clearly sex-specific and associated with chick developmental stage. Females made fewer, longer foraging trips and spent less time at the nest during chick provisioning. These sex-specific differences became increasingly apparent with chick development. Additionally, parents in better body condition spent longer periods at their nests and those which returned later in the day had longer overall nest attendance bouts. Using recent technological advances, this study provides new insights into the foraging behaviour of breeding seabirds, particularly during the post-guarding phase. The biparental strategy of chick provisioning revealed in this study appears to be an example where the costs of egg development to the female are balanced by paternal-dominated chick provisioning particularly as the chick nears fledging.  
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Auteur Ndour, I.; Loc'h, F.L.; Kantoussan, J.; Thiaw, M.; Diadhiou, H.D.; Ecoutin, J.M.; Morais, L.T. de; Thiaw, O.T. url  doi
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  Titre Changes in the trophic structure, abundance and species diversity of exploited fish assemblages in the artisanal fisheries of the northern coast, Senegal, West Africa Type Article scientifique
  Année 2014 Publication Revue Abrégée African Journal of Marine Science  
  Volume 36 Numéro 3 Pages 361-368  
  Mots-Clés  
  Résumé This work investigates the effects of changes in both fishing pressure and the environment on the trophic dynamics, abundance and diversity of species in the artisanal commercial fisheries off the northern coast of Senegal. Using artisanal commercial fishing data (provided by the Centre for Oceanographic Research of Dakar-Thiaroye [CRODT] in Senegal), we identify changes in the catch per unit effort, mean trophic level, biomass trophic spectrum and species diversity between two fishing periods (1990–1999 and 2000–2009). Decreases in mean trophic level, the biomass of high trophic level species and indices of species diversity between 1990 and 2009 were observed in commercial catches. These decreases were then related to changes in fishing pressure, fishing strategy and the combined effects of fishing and environmental factors (as derived from satellite observations). This paper helps to better inform the management of fisheries resources by providing decision makers with more effective biological indicators that incorporate the effects of fishing pressure and environmental change and that are applicable at local, regional and global scales.  
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  ISSN 1814-232x ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection (down) 1201  
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