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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
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 (up) LL @ pixluser @ collection 365
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Auteur Marsac, F.; Barlow, R.; Ternon, J.-F.; Ménard, F.; Roberts, M.
Titre Ecosystem functioning in the Mozambique Channel : synthesis and future research Type Article scientifique
Année 2014 Publication Revue Abrégée Deep-Sea Research Part II.Topical Studies in Oceanography
Volume 100 Numéro No spécial Pages 212-220
Mots-Clés Bio-physical coupling; Ecosystem approach; Mesoscale circulation; Mozambique Channel
Résumé The MESOBIO programme investigated mesoscale dynamics using an integrated ecosystem approach, linking physical and biogeochemical processes with different trophic levels. Observation and modeling were used in combination to explain the main processes occurring in the mesoscale eddy field. The particular shape of the Mozambique Channel, composed of two basins interconnected through a narrow zone, favours the generation of mesoscale eddies and increases the opportunity for eddy-shelf interactions. Phytoplankton abundance peaked in areas of nutrient enrichment that are often found in the core of cyclonic eddies, as well as on the continental shelf. Grazers in zooplankton communities exhibited high biovolume in cyclonic eddies, but their abundance was lower in fronts and divergence zones, with lowest biovolume in anticyclones. Biovolume was highest at shelf stations, but very variable and similar to phytoplankton. Age of eddies, their subsequent maturation stage and the dynamics of the eddy field played a major role effecting zooplankton abundance. Micronekton presented abundance patterns coherent with zooplankton distribution, however this was only demonstrated by acoustic methods, whereas mid-water trawl collection and predators stomach contents (predators being used as biological samplers) did not reveal significant relationships with mesoscale features. For upper trophic levels, the average density of foraging seabirds was lowest in anticyclones, highest in cyclones and at intermediate levels in divergence, shelf and frontal zones. However, multifaceted behavioral responses were observed in such a highly variable environment. Swordfish was clearly associated with divergence zones, and to a lesser extent with fronts, suggesting that the higher density in divergences was related to the presence of its main prey, essentially large squids. Although tunas tended to be more abundant in areas with weak geostrophic currents, their relationship to mesoscale features was not straightforward as adult tunas caught by longline have the ability to explore different foraging habitats over a broad range of depths. Several suggestions for advancing eddy-related research from the current state of knowledge are proposed in the second part of the paper.
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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
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Numéro d'Appel (up) LL @ pixluser @ collection 366
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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
Mots-Clés
Résumé
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Editeur Lieu de Publication Éditeur
Langue 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
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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
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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Volume de collection Numéro de collection Edition
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Auteur Potier, M.; Bach, P.; Ménard, F.; Marsac, F.
Titre Influence of mesoscale features on micronekton and large pelagic fish communities 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 184-199
Mots-Clés Biodiversity; Mid-water trawl; Mozambique Channel; Oceanic eddies; Pelagic longline; Stomach contents
Résumé We investigated the diversity and distribution of two communities, micronekton organisms and large predatory fishes, sampled in mesoscale features of the Mozambique Channel from 2003 to 2009, by combining mid-water trawls, stomach contents of fish predators and instrumented longline fishing surveys. The highest species richness for assemblages was found in divergences and fronts rather than in the core of eddies. Despite an unbalanced scheme, diversity indices did not differ significantly between cyclonic and anticyclonic eddies, divergences and fronts. We found that eddies and associated physical cues did not substantially affect the distribution of micronektonic species which are mainly driven by the diel vertical migration pattern. Top predators exhibited a more complex response. Swordfish (Xiphias gladius) associated better with mesoscale features than tunas, with a clear preference for divergences which is consistent with the diel vertical migrations and occurrence of its main prey, the flying squids Sthenoteuthis oualaniensis (Ommastrephidae). On the other hand, the probability of presence of yellowfin tuna was not tied to any specific eddy structure. However, the highest values of positive yellowfin CPUEs were associated with low horizontal gradients of sea-level anomalies. We also showed a non-linear response of positive yellowfin CPUEs with respect to the depth of the minimal oxygen content. The larger the distance between the hooks and the minimal oxygen layer, towards the surface or at greater depths, the higher the CPUE, highlighting that yellowfin congregated in well-oxygenated waters. Micronekton sampled by mid-water trawls and stomach contents exhibited different species composition. The highly mobile organisms were not caught by trawling whereas they remain accessible to predators. The combination of stomach contents and mid-water trawls undoubtedly improved our understanding of the micronekton assemblage distribution. Our results provide some evidence that mesoscale features in the Mozambique Channel do not strongly affect the distribution of the mid-trophic level organisms such as micronekton and most of the large predatory fishes, and hypotheses are proposed to support this result.
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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 (up) LL @ pixluser @ collection 369
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