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Auteur NIEBLAS, A.-E.; DRUSHKA, K.; REYGONDEAU, G.; ROSSI, V.; DEMARCQ, H.; DUBROCA, L.; BONHOMMEAU, S.
Titre Defining Mediterranean and Black Sea Biogeochemical Subprovinces and Synthetic Ocean Indicators Using Mesoscale Oceanographic Features Type Article scientifique
Année 2014 Publication Revue Abrégée Plos One
Volume 9 Numéro 10 Pages 1-13
Mots-Clés (up)
Résumé 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, finite-size Lyapunov exponents, and surface frontal gradients) ocean features that we use to characterize the surface ocean variability. We employ a k-means clustering algorithm to objectively define biogeochemical subprovinces based on classical features, and, for the first time, on mesoscale features, and on a combination of both classical and mesoscale features. Principal components analysis is then performed on the oceanographic variables to define integrative indices to monitor the environmental changes within each resultant subprovince at monthly resolutions. Using both the classical and mesoscale features, we find five biogeochemical subprovinces for the Mediterranean and Black Seas. Interestingly, the use of mesoscale variables contributes highly in the delineation of the open ocean. The first axis of the principal component analysis is explained primarily by classical ocean features and the second axis is explained by mesoscale features. Biogeochemical subprovinces identified by the present study can be useful within the European management framework as an objective geographical framework of the Mediterranean and Black Seas, and the synthetic ocean indicators developed here can be used to monitor variability and long-term change.
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ISSN 1932-6203 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1130
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Auteur Lezama-Ochoa, A.; Irigoien, X.; Chaigneau, A.; Quiroz, Z.; Lebourges Dhaussy, A.; Bertrand, A.
Titre Acoustic reveal the presence of Macrozooplankton biocline in the Bay of Biscay in response to hydrological conditions and predator-prey relationships Type Article scientifique
Année 2014 Publication Revue Abrégée PLoS One
Volume 9 Numéro 2 Pages
Mots-Clés (up)
Résumé Bifrequency acoustic data, hydrological measurements and satellite data were used to study the vertical distribution of

macrozooplankton in the Bay of Biscay in relation to the hydrological conditions and fish distribution during spring 2009.

The most noticeable result was the observation of a &8216;biocline&8217; during the day i.e., the interface where zooplankton biomass

changes more rapidly with depth than it does in the layers above or below. The biocline separated the surface layer, almost

devoid of macrozooplankton, from the macrozooplankton-rich deeper layers. It is a specific vertical feature which ties in

with the classic diel vertical migration pattern. Spatiotemporal correlations between macrozooplankton and environmental

variables (photic depth, thermohaline vertical structure, stratification index and chlorophyll-a) indicate that no single factor

explains the macrozooplankton vertical distribution. Rather a set of factors, the respective influence of which varies from

region to region depending on the habitat characteristics and the progress of the spring stratification, jointly influence the

distribution. In this context, the macrozooplankton biocline is potentially a biophysical response to the search for a

particular depth range where light attenuation, thermohaline vertical structure and stratification conditions together

provide a suitable alternative to the need for expending energy in reaching deeper water without the risk of being eaten.
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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 1932-6203 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 365
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Auteur SARAUX, C.; FROMENTIN, J.-M.; BIGOT, J.-L.; BOURDEIX, J.-H.; MORFIN, M.; ROOS, D.; VAN BEVEREN, E.; BEZ, N.
Titre Spatial Structure and Distribution of Small Pelagic Fish in the Northwestern Mediterranean Sea Type Article scientifique
Année 2014 Publication Revue Abrégée Plos One
Volume 9 Numéro 11 Pages 1-12
Mots-Clés (up)
Résumé Understanding the ecological and anthropogenic drivers of population dynamics requires detailed studies on habitat selection and spatial distribution. Although small pelagic fish aggregate in large shoals and usually exhibit important spatial structure, their dynamics in time and space remain unpredictable and challenging. In the Gulf of Lions (north-western Mediterranean), sardine and anchovy biomasses have declined over the past 5 years causing an important fishery crisis while sprat abundance rose. Applying geostatistical tools on scientific acoustic surveys conducted in the Gulf of Lions, we investigated anchovy, sardine and sprat spatial distributions and structures over 10 years. Our results show that sardines and sprats were more coastal than anchovies. The spatial structure of the three species was fairly stable over time according to variogram outputs, while year-to-year variations in kriged maps highlighted substantial changes in their location. Support for the McCall's basin hypothesis (covariation of both population density and presence area with biomass) was found only in sprats, the most variable of the three species. An innovative method to investigate species collocation at different scales revealed that globally the three species strongly overlap. Although species often co-occurred in terms of presence/absence, their biomass density differed at local scale, suggesting potential interspecific avoidance or different sensitivity to local environmental characteristics. Persistent favourable areas were finally detected, but their environmental characteristics remain to be determined.
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Volume de collection Numéro de collection Edition
ISSN 1932-6203 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1134
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Auteur Nieblas, A.E.; Bonhommeau, S.; Le Pape, O.; Chassot, E.; Dubroca, L.; Barde, J.; Kaplan, D.
Titre Reply to Roopnarine : what is an apex predator ? Type Article scientifique
Année 2014 Publication Revue Abrégée Proceedings of the National Academy of Sciences of the United States of America
Volume 111 Numéro 9 Pages
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Volume de collection Numéro de collection Edition
ISSN 0027-8424 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 367
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Auteur Poisson, F.; Filmalter, J.D.; Vernet, A.L.; Dagorn, L.
Titre Mortality rate of silky sharks (Carcharhinus falciformis) caught in the tropical tuna purse seine fishery in the Indian Ocean Type Article scientifique
Année 2014 Publication Revue Abrégée Canadian Journal of Fisheries and Aquatic Sciences
Volume 71 Numéro 6 Pages 795-798
Mots-Clés (up)
Résumé Scientists aboard French purse seine vessels recorded the number and condition of silky sharks (Carcharhinus falciformis) caught during three fishing cruises in the Indian Ocean. A sample of 31 individuals that showed signs of life were tagged with satellite tags to investigate their postrelease mortality. The majority of individuals (95%) were brought on board using the brailer. Combining the proportion of sharks that were dead (72%) and the mortality rate of those released (48%), the overall mortality rate of brailed individuals was 85%. Few individuals (5%) were not brailed as they were entangled and landed during the hauling process. The survival rate of these individuals was high, with an overall mortality rate of meshed individuals of 18%. The combination of these two categories led to an overall mortality rate of 81%. This high value reflects the harsh conditions encountered by sharks during the purse seine fishing process. Consequently, methods that prevent sharks being brought on board are a priority for future investigations, but good handling practices should also be promoted as they could reduce mortality by at least 19%.
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ISSN ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 368
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