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Auteur (up) Jaquemet, S.; Ternon, J.-F.; Kaehler, S.; Thiebot, J.B.; Dyer, B.; Bemanaja, E.; Marteau, C.; Le Corre, M. url  doi
openurl 
  Titre Contrasted structuring effects of mesoscale features on the seabird community in the Mozambique Channel Type Article scientifique
  Année 2014 Publication Revue Abrégée Deep-Sea Research Part II.Topical Studies in Oceanography  
  Volume 100 Numéro No spécial Pages 200-211  
  Mots-Clés Foraging habitats; Frigatebird; Marine productivity; Mesoscale eddies; Red-footed booby; Sooty tern; Tropical marine predators; Tuna; Western Indian Ocean  
  Résumé The Mozambique Channel (western Indian Ocean) is a dynamic environment characterised by strong mesoscale features, which influence all biological components of the pelagic ecosystem. We investigated the distribution, abundance and feeding behaviour of seabirds in the Mozambique Channel in relation to physical and biological environmental variables, with a specific interest in mesoscale features. Seabird censuses were conducted in summer and winter during 7 cruises in the southern and northern Mozambique Channel. Tropical species accounted for 49% of the 37 species identified and 97% of the individuals, and species from the sub-Antarctic region constituted 30% of the identifications. The typically tropical sooty tern (Onychoprion fuscata) was the dominant species during all cruises, and overall accounted for 74% of the species observations and 85% of counted birds. Outputs of Generalised Linear Models at the scale of the Mozambique Channel suggested that higher densities of flying and feeding birds occurred in areas with lower sea surface temperatures and lower surface chlorophyll a concentrations. Most of the flocks of feeding birds did not associate with surface schools of fish or marine mammals, but when they did, these flocks were larger, especially when associated with tuna. While tropical species seemed to favour cyclonic eddies, frontal and divergence zones, non-tropical species were more frequently recorded over shelf waters. Sooty terns foraged preferentially in cyclonic eddies where zooplankton, micronelcton and tuna schools were abundant. Among other major tropical species, frigatebirds (Fregata spp.) predominated in frontal zones between eddies, where tuna schools also frequently occurred and where geostrophic currents were the strongest. Red-footed boobies (Sula sub) concentrated in divergence zones characterised by low sea level anomalies, low geostrophic currents, and high zooplanlcton biomass close to the surface. Our results highlight the importance of mescoscale features in structuring the tropical seabird community in the Mozambique Channel, in addition to segregating tropical and non-tropical species. The mechanisms underlying the segregation of tropical seabirds seem to partially differ from that of other tropical regions, and this may be a consequence of the strong local mesoscale activity, affecting prey size and availability schemes. Beyond characterising the foraging habitats of the seabird community of the Mozambique Channel, this study highlights the importance of this region as a hot spot for seabirds; especially the southern part, where several endangered sub-Antarctic species over-winter.  
  Adresse  
  Auteur institutionnel Thèse  
  Editeur Lieu de Publication Éditeur Barlow, R.; Marsac, F.; Ternon, J.-F.; Roberts, M.  
  Langue Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0967-0645 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 363  
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Auteur (up) Tew-Kai, E.; Rossi, V.; Sudre, J.; Weimerskirch, H.; Hernandez-Garcia, E.; Marsac, F.; Garçon, V. doi  openurl
  Titre Top marine predators track Lagrangian coherent structures Type Article scientifique
  Année 2009 Publication Revue Abrégée Proc. Natl. Acad. Sci. U. S. A.  
  Volume 106 Numéro Pages 8245-8250  
  Mots-Clés finite-size Lyapunov exponent; frigatebird; Mozambique Channel; submesoscale  
  Résumé Meso- and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behavior and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel in the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamic concept, the finite-size Lyapunov exponent (FSLE), we identified Lagrangian coherent structures (LCSs) present in the surface flow in the channel over a 2-month observation period (August and September 2003). By comparing seabird satellite positions with LCS locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short trips and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biologic corridors. The birds being often associated with tuna schools around foraging areas, a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel.  
  Adresse  
  Auteur institutionnel Thèse  
  Editeur Lieu de Publication Éditeur  
  Langue Eng Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0027-8424 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 30  
Lien permanent pour cet enregistrement
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