Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Geochronological studies of samples from continuous crustal sections of fossil intra-oceanic arcs are paramount for determining the precise timing of major processes that took place during the building of an oceanic island-arc crust. In this study, laser ablation ICP-MS U-Pb zircon (and conventional Rb-Sr) analyses pinpoint the timing of major events responsible for crustal growth of the Kohistan paleo-island arc (Northern Pakistan). Inheritance in magmatic rocks is evidence for recycling of intra-arc material and indicates that the Kohistan arc may have formed as early as 135 +/- 4 Ma. One older inherited grain indicates that the arc developed on a young oceanic lithosphere whose remnants include a c. 175 Ma old component. An interesting consequence is that intra-oceanic arc magmas can yield inherited zircons, which can be much older than the arc system itself without requiring recycling back into the mantle by subduction processes. In the case of the Kohistan arc, ante-arc Neotethys oceanic lithosphere was tapped by arc magmas during their way upward into the arc crust. The oldest magmatic ages measured in this study fall in the range 101-102 Ma (100.9 +/- 0.6 and 102.1 +/- 0.4 Ma). This period corresponds to arc build-up and thickening of the arc crust. Leucogranitic melts dated at 89.9 +/- 0.4 Ma and 90.9 +/- 1.0 Ma are considered as produced by dehydration/melting reaction accompanying granulitisation of the thickened lower arc crust. A maximum age for this event is 97.7 +/- 0.7 Ma, the age of emplacement of a garnet meta-tonalite affected by granulite facies metamorphism. Magmatic activity was still ongoing during and after the granulitisation as testified by emplacement of a diorite and a gabbro dated at 89.1 +/- 0.6 and 88.2 +/- 0.9 Ma respectively. The upper part of the metaplutonic sequence contains diorite samples dated at 84.6 +/- 0.5 Ma and 84.3 +/- 0.5 Ma and as young as 81.1 +/- 0.7 Ma. During this period, and based on the present day outcropping sequences, the mean crustal growth rate varied from 32 to 65 km(3)/km/Ma (volume per unit width along the strike of the arc) which is comparable to the range for present day arcs of the Western Pacific region. The correspondence of crustal growth rates observed for present-day island arcs and the good preservation of the crustal section in the Kohistan arc, make this area an exceptional natural laboratory to study arc related processes and to check models of continental crust formation by arc accretion.
ISSN: 0012-821X

hal-00644555
https://hal.archives-ouvertes.fr/hal-00644555
DOI : 10.1016/j.epsl.2011.07.016

Éditeur(s) : Blackwell science
Résumé : Patterns of mitochondrial DNA (mtDNA) variation were used to analyse the population genetic structure of southwestern Indian Ocean green turtle (Chelonia mydas) populations. Analysis of sequence variation over 396 bp of the mtDNA control region revealed seven haplotypes among 288 individuals from 10 nesting sites in the Southwest Indian Ocean. This is the first time that Atlantic Ocean haplotypes have been recorded among any Indo-Pacific nesting populations. Previous studies indicated that the Cape of Good Hope was a major biogeographical barrier between the Atlantic and Indian Oceans because evidence for gene flow in the last 1.5 million years has yet to emerge. This study, by sampling localities adjacent to this barrier, demonstrates that recent gene flow has occurred from the Atlantic Ocean into the Indian Ocean via the Cape of Good Hope. We also found compelling genetic evidence that green turtles nesting at the rookeries of the South Mozambique Channel (SMC) and those nesting in the North Mozambique Channel (NMC) belong to separate genetic stocks. Furthermore, the SMC could be subdivided in two different genetic stocks, one in Europa and the other one in Juan de Nova. We suggest that this particular genetic pattern along the Mozambique Channel is attributable to a recent colonization from the Atlantic Ocean and is maintained by oceanic conditions in the northern and southern Mozambique Channel that influence early stages in the green turtle life cycle.
Molecular Ecology (0962-1083) (Blackwell science), 2007 , Vol. 16 , N. 1 , P. 175-186

Droits : 2007 Blackwell
http://archimer.ifremer.fr/doc/2007/publication-2185.pdf
DOI:10.1111/j.1365-294X.2006.03122.x
http://archimer.ifremer.fr/doc/00000/2185/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
AimThe global biodiversity crisis requires the identification of regions with high evolutionary potential, i.e. evolutionary hotspots (evospots). We created an analytical framework based on comparative phylogeography and coalescent methods to assess the dynamics of diversification and population persistence in the reef ecosystem of a little-studied region: the Southwestern Indian Ocean (SWIO).LocationCoral reefs of the SWIO, with comparative data from the Pacific Ocean.MethodsWe generated sequences of mitochondrial DNA (COI and 16S) for 10 widespread brittle-stars (345 specimens) from 21 localities (8 in the SWIO). We analysed them by combining comparative phylogeography approaches, coalescent-based methods, molecular clocks and the concept of evolutionarily significant units (ESUs) to draw conclusions about the drivers of biodiversity in the region.ResultsCryptic diversity was prevalent, increasing lineage diversity within the 10 nominal species by 70% within the SWIO and by 200% across the Indo-West Pacific. All seven new SWIO lineages meet the criteria for ESUs and at least six are biological species. We detected likely intraregional diversifications dating to the Plio-Pleistocene, supporting the SWIO as a generator of biodiversity. Geographical restriction of ESUs, long coalescent times (> 80 ka) and old in situ diversification (> 1 Ma) point to the persistence of populations over multiple glacio-eustatic cycles. We provide data suggesting demographic expansion during sea-level high stands. Regional connectivity was lower, and cryptic differentiation higher in lecithotrophs than in planktotrophs.Main conclusionsThe analytical framework based on a biodiversity survey makes it possible to identify evospots by assessing the potential of a region to maintain and generate biodiversity and by evaluating the evolutionary processes and potential drivers at play.
ISSN: 0305-0270

hal-01369697
http://hal.univ-reunion.fr/hal-01369697
DOI : 10.1111/jbi.12155

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A variety of atypical plume-like structures and focused upwellings that are not rooted in the lower mantle have recently been discussed, and seismological imaging has shown ubiquitous small-scale convection in the uppermost mantle in regions such as the Mediterranean region, the western US, and around the western Pacific. We argue that the three-dimensional return flow and slab fragmentation associated with complex oceanic subduction trajectories within the upper mantle can generate focused upwellings and that these may play a significant role in regional tectonics. The testable surface expressions of this process are the outside-arc alkaline volcanism, topographic swell, and low-velocity seismic anomalies associated with partial melt. Using three-dimensional, simplified numerical subduction models, we show that focused upwellings can be generated both ahead of the slab in the back-arc region (though -five times further inward from the trench than arc-volcanism) and around the lateral edges of the slab (in the order of 100 km away from slab edges). Vertical mass transport, and by inference the associated decompression melting, in these regions appears strongly correlated with the interplay between relative trench motion and subduction velocities. The upward flux of material from the depths is expected to be most pronounced during the first phase of slab descent into the upper mantle or during slab fragmentation. We discuss representative case histories from the Pacific and the Mediterranean where we find possible evidence for such slab-related volcanism.
ISSN: 0012-821X

hal-00553075
https://hal.archives-ouvertes.fr/hal-00553075
DOI : 10.1016/j.epsl.2010.08.012

Éditeur(s) : HAL CCSD
Résumé : Satellite and in situ chlorophyll concentration data collected as part of VALidation HYperspectral of a BIOgeochemical model (ValHyBio), a PNTS-sponsored project dedicated to satellite ocean-colour imaging of the Southwest Pacific, are analyzed to describe chlorophyll variability in the Coral Sea, a vast oligotrophic region characterized by a deep chlorophyll maximum and blue waters of high transparency. Average chlorophyll concentrations estimated from MODIS-Aqua are very low (<0.2 mg m-3) except in the vicinity of main islands and coral reefs, where enrichment may occur due to upwelling or internal waves that bring nutrients to the euphotic zone from the deep part of the water column. During the summer season, blooms of cyanobacteria (Trichodesmium) develop in the surface waters and may form large slicks. The nitrogen fixed by these slicks is a potential source of new nitrogen later assimilated by picoplankton and the marine food chain. Coastal areas exhibit higher chlorophyll concentrations because of nutrient input from the land, as observed in 2008 around New Caledonia. In lagoon areas, the sea colour is influenced by turbidity and bathymetry, and the MODIS OC3 algorithm is inadequate, with a systematic overestimation of chlorophyll concentration in the New Caledonia lagoon. Improved bio-optical algorithms are needed for those turbid and shallow waters, to allow not only a better description of chlorophyll variability, but also evaluation of chlorophyll simulations by recently developed biogeochemical models.
of the 12th International Coral Reef Symposium, 18E
CAIRNS, Australia

hal-00746470
https://hal.archives-ouvertes.fr/hal-00746470
https://hal.archives-ouvertes.fr/hal-00746470/document

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Despite decades of petrological and geochemical studies, the nature and setting of obducted ophiolites remain controversial: the influence of supra-subduction zone environments on pre-existing oceanic lithosphere is yet to assess, and the processes leading to subduction/obduction initiation are still poorly constrained. Our study documents successive influx of slab-derived fluids and progressive strain localization within the upper mantle in a supra-subduction environment during the first few My of the subduction history. We focus on strongly sheared mafic amphibolites intruding peridotites near the mantle–crust transition of the New Caledonia obducted ophiolite and ~ 50 to 100 m above the basal thrust contact of the ophiolite. These m- to hm-long and several m-thick shear bands are interpreted as inherited small-scale intrusions of mafic melts, probably dikes or sills, which were derived from a moderately refractory mantle source refertilized by supra-subduction zone fluids. 40Ar/39Ar age constraints on pargasite at ca. 90 Ma suggest that they could be inherited from the former Pacific west-dipping subduction.Secondary deformation of these mafic intrusions is intimately associated to three major stages of fluid infiltration: (1) the first stage of deformation and metasomatism is marked by syn-kinematic growth of Ca-amphibole (at 700–800 °C and 3–5 kbar) with a distinctive supra-subduction zone signature, and controlled later channelization of aqueous fluids. 40Ar/39Ar dating on magnesio-hornblende indicates that this deformation episode occurred at ca. 55 Ma, coincident with east-dipping subduction initiation; (2) the main metasomatic stage, characterized by the development of a phlogopite-rich matrix wrapping peridotites and amphibolite boudins, points to the percolation of alkali-rich aqueous fluids at still high temperature (650–750 °C); (3) the last, low temperature (< 600 °C) metasomatic stage results in the formation of deformed veinlets containing talc, chlorite and serpentine.
ISSN: 0024-4937

hal-01306664
https://hal.archives-ouvertes.fr/hal-01306664
https://hal.archives-ouvertes.fr/hal-01306664/document
https://hal.archives-ouvertes.fr/hal-01306664/file/Soret_2016_Strain_localization.pdf
DOI : 10.1016/j.lithos.2015.11.022

Éditeur(s) : American Geophysical Union
Résumé : We use seismic reflection and rock sample data to propose that the first-order physiography of New Caledonia Trough and Norfolk Ridge formed in Eocene and Oligocene time and was associated with the onset of subduction and back-arc spreading at the Australia-Pacific plate boundary. Our tectonic model involves an initial Cretaceous rift that is strongly modified by Cenozoic subduction initiation. Hence, we are able to explain (1) complex sedimentary basins of inferred Mesozoic age; (2) a prominent unconformity and onlap surface of middle Eocene to early Miocene age at the base of flat-lying sediments beneath the axis of New Caledonia Trough; (3) gently dipping, variable thickness, and locally deformed Late Cretaceous strata along the margins of the trough; (4) platform morphology and unconformities on either side of the trough that indicate a phase of late Eocene to early Miocene uplift to near sea level, followed by rapid Oligocene and Miocene subsidence of similar to 1100-1800 m; and (5) seismic reflection facies tied to boreholes that suggest absolute tectonic subsidence at the southern end of New Caledonia Trough by 1800-2200 m since Eocene time. The Cenozoic part of the model involves delamination and subduction initiation followed by rapid foundering and rollback of the slab. This created a deep (>2 km) enclosed oceanic trough, similar to 2000 km long and 200-300 km across, in Eocene and Oligocene time as the lower crust detached, with simultaneous uplift and local land development along basin flanks. Disruption of Late Cretaceous and Paleogene strata was minimal during this Cenozoic phase and involved only subtle tilting and local reverse faulting or folding. Basin formation was possible through the action of at least one detachment fault that allowed the lower crust to either be subducted into the mantle or exhumed eastward into Norfolk Basin. We suggest that delamination of the lithosphere, with possible mixing of the lower crust back into the mantle, is more widespread than previously thought and may be commonly associated with subduction initiation, such as Cenozoic events in the Mediterranean and western Pacific.
Tectonics (0278-7407) (American Geophysical Union), 2010-03 , Vol. 29 , N. TC2004 , P. 1-16

Droits : Copyright 2010 by the American Geophysical Union.
http://archimer.ifremer.fr/doc/00001/11271/9283.pdf
DOI:10.1029/2009TC002476
http://archimer.ifremer.fr/doc/00001/11271/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Three-dimensional P-wave velocity structure of the mantle beneath the South Pacific Superswell is determined through passive broadband seismic experiments on the ocean floor and islands between 2003 and 2005. We collected approximately 1500 relative times of long-period teleseismic P-waves by using a waveform cross-correlation. We analyzed this data set with relative time tomography to depths of 2000 km. The resultant structure shows lateral heterogeneity of approximately +/- 2%, in which a distinct low velocity region is found beneath the center of the Superswell at a depth of 1600 km. At 1200km depth, an elongated low velocity region is found beneath the Society to Pitcairn hotspots. At 800 km depth, two linear low velocity regions are located beneath Tuamotu and Austral islands. Isolated low velocity regions are identified beneath the Society, Marquesas, and Macdonald hotspots at 400 km depth. Our new tomographic images reveal that the large low velocity region rooted in the deep lower mantle is split into two sheets at 1200 km depth and these terminate at approximately 800 km depth. This feature appears to be consistent with the characteristics of a thermo-chemical pile or dome.
ISSN: 0031-9201

hal-00413036
https://hal.archives-ouvertes.fr/hal-00413036
https://hal.archives-ouvertes.fr/hal-00413036/document
https://hal.archives-ouvertes.fr/hal-00413036/file/Tanaka_tomo_PLUME_PEPI2009_hal.pdf
DOI : 10.1016/j.pepi.2008.10.016

Éditeur(s) : Neidine Editeurs
Résumé : The text is the transcription of the oral presentation made on November 5th, 2014 in front of the National Assembly in Paris within the framework of the conference, organized by the FEDOM and the ACCIOM, entitled: " the economic and strategic stakes of South Pacific overseas French Territories: New Caledonia, French Polynesia, Wallis and Futuna : valuable lands, ocean of future ". After a presentation of the geographical context of the three communities: New Caledonia, Wallis and Futuna and French Polynesia, a first chapter develops their main advantages towards stakes in economic growth in terms of spaces, quality, biodiversity, geo-diversity, energy resources, know-how … A second chapter, after a reminder of the ambitions of the National Commission on Innovation focuses for each of the territories on the axes of new growth linked to the maritime potential which characterizes them. In conclusion we clarify all the interest which represent these three communities and their complementarities as sustainable development laboratories bound to the sea and the necessity of the elaboration of adequate support strategies..
Le texte est la transcription de la présentation orale effectuée le 5 novembre 2014 devant l’Assemblée Nationale à Paris dans le cadre de la conférence, organisée par la FEDOM et l’ACCIOM, intitulée : « Les enjeux économiques et stratégiques de l’outre-mer français du Pacifique : Nouvelle-Calédonie, Polynésie française, Wallis et Futuna , terres de valeurs, océan d’avenir ». Après une présentation du contexte géographique des 3 collectivités : Nouvelle-Calédonie, Wallis et Futuna et Polynésie française, un premier chapitre développe leurs atouts majeurs vis-à-vis d’enjeux de croissance en termes d’espaces, de qualité, de biodiversité, de géo-diversité, de ressources énergétiques, de savoir-faire… Un second chapitre, après un rappel des ambitions de la Commission Nationale Innovation se focalise pour chacun des 3 territoires sur les axes de croissance nouvelle liée au potentiel maritime qui les caractérise. En conclusion on explicite tout l’intérêt que représentent ces trois collectivités et leurs complémentarités comme laboratoires de développement durable lié à la mer et la nécessité de l’élaboration de stratégies d’accompagnement adéquates.
Tai Kona (2269-7535) (Neidine Editeurs), 2015-03 , N. 12 , P. 24-38

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00255/36615/35184.pdf
http://archimer.ifremer.fr/doc/00255/36615/

Éditeur(s) : Amer Geophysical Union
Résumé : The freshest surface waters in the tropical Pacific are found at its eastern boundary. Using in situ observations, we depict the quasi-permanent presence of a far eastern Pacific fresh pool with Sea Surface Salinity (SSS) lower than 33, which is confined between Panama's west coast and 85W in December and extends westward to 95W in April. Strong SSS fronts are found at the outer edge of this fresh pool. We investigate the seasonal dynamics of the fresh pool using complementary satellite wind, rain, sea level and in situ oceanic current data at the surface, along with hydrographic profiles. The fresh pool appears off Panama due to the strong summer rains associated with the northward migration of the ITCZ over Central America in June. During the second half of the year, the eastward-flowing North Equatorial Counter Current keeps it trapped to the coast and strengthens the SSS front on its western edge. During winter, as the ITCZ moves southward, the north-easterly Panama gap wind creates a south-westward jet-like current in its path with a dipole of Ekman pumping/eddies on its flanks. As a result, upwelling in the Panama Bight brings to the surface cold and salty waters which erode the fresh pool on its eastern side while both the jet current and the enhanced South Equatorial Current stretch the fresh pool westward until it nearly disappears in May. New SMOS satellite SSS data proves able to capture the main seasonal features of the fresh pool and monitor its spatial extent.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2012-04 , Vol. 117 , P. -

Droits : 2012 AGU
http://archimer.ifremer.fr/doc/00072/18311/16581.pdf
DOI:10.1029/2011JC007802
http://archimer.ifremer.fr/doc/00072/18311/

Éditeur(s) : Gauthier-Villars
Résumé : Since the advent of plate tectonics the active margins of the oceans have been studied according to a model whose basis is a piling up of imbrications of oceanic material units, in front of the upper plate, forming a great tectonic accretionary prism. This model is broadly the same for all the authors; it has been largely used for alpine-type or paleo-oceanic mountain chain, all around the world. The authors have directly taken part in the drillings on western and eastern Pacific active margins (Legs 60 and 67) and they have worked on the tectonics of alpine (paleo-oceanic) chains of the peri-mediterranean, peri-caribbean, and peripacific belts. They compare the geological data acumulated from these tow direct sources. The tectonic constraints constraints regime is specified and the consequences of the subduction are looked for. The notions of collison and obduction are discussed in relation to subduction and tectonics. Finally, an anlaysis of the temporal evolution of active margins and of chains, shows the necessity of thinking in terms of superimposed tectonics.
Oceanologica Acta, Special issue (0399-1784) (Gauthier-Villars), 1981

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00246/35700/34207.pdf
http://archimer.ifremer.fr/doc/00246/35700/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : It is generally accepted that innovations in tuna purse seine technology have affected fishing operations and the traditional measurement of fishing effort, days fished including searching time. Not much is known, however, about the actual effects of the innovations on fishing performance. Data from the us tuna purse seine fishery in the Western Pacific Ocean were used to determine the impact of drifting Fish Aggregating Devices (fads) on the performance of the us fleet. The results indicate, inter alia, a high rate of success (96%) in catching tuna and high yield rate (37 t/successful set) for fad sets. Log sets were comparable in success rate (94%) and catch rate (36 t/successful set). Unassociated sets, on the other hand, had a higher catch rate (42 t/successful set) than fad sets, but a low success rate, 53 per cent. fad sets significantly improved the fleet's performance.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15296/12655.pdf
http://archimer.ifremer.fr/doc/00042/15296/

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
In order to ensure a sustainable management of reef fisheries, data need to be collected regularly on the effect of these fisheries on both fish resources and the ecosystems that sustain them. Habitat and resources monitoring programs can provide such information, but are difficult to implement as they involve a range of technical, financial and human resources. Regarding these problems, the involvement of the local population in monitoring programs, called participatory monitoring, seems to offer solutions. Indeed, participatory monitoring has the potential of increasing the number of data collected at low cost, while taking advantage of the traditional ecological knowledge available locally. Some questions need clarifying, however: which methods can bring relevant information for the monitoring of reef fisheries while being appropriate to the motivations and skills of the local population? Is the degree of participation of the local population sufficient to make the monitoring program work, particularly over the long term? To answer these questions, participatory monitoring methods commonly used for coral reef ecosystems have been implemented to assess reef fisheries at three different sites: Moorea island and Tikehau atoll in French Polynesia, and the Bay of Tulear in Madagascar. While highlighting the relevance of some participatory monitoring programs for snapshot and large-scale surveys, the results of this study also show their lesser interest for regular data gathering on long-time scales. In any case, strong coordination and supervision by scientists are considered essential.
La gestion durable des écosystèmes coralliens nécessite de disposer d’informations régulières concernant l’impact des pêcheries sur les ressources récifales et sur les écosystèmes dont elles dépendent. Les suivis intégrés des ressources, des habitats et des espèces associées qui visent à fournir ce type d’informations sont difficiles à mettre en œuvre, car ils impliquent de nombreuses ressources humaines, techniques et financières. Face à ces problèmes, la participation de la société civile dans les programmes de suivi semble en mesure d’apporter des solutions. Dans le but de tester cette hypothèse, des méthodes de suivi participatif ont été mises en œuvre afin de caractériser des pêcheries récifales sur trois socio-écosystèmes contrastés : l’île de Moorea et l’atoll de Tikehau en Polynésie française, et le littoral de Tuléar à Madagascar. Les résultats de cette étude soulignent la pertinence de certains suivis participatifs pour fournir une vision écosystémique dans le cas de collecte de données ponctuelles et de large envergure, et leur intérêt moindre pour la collecte continue de données sur de longues échelles de temps. Dans tous les cas, une structure de coordination et l’implication de scientifiques s’avèrent primordiales pour assurer pérennité et fiabilité au système de suivi.
ISSN: 1240-1307

hal-01302983
https://hal-univ-perp.archives-ouvertes.fr/hal-01302983
DOI : 10.1051/nss/2013109

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
IODP Expedition 324 cored igneous rocks from Shatsky Rise, an oceanic plateau in the northwest Pacific Ocean that formed mainly during late Jurassic and Early Cretaceous times. We selected 60 samples from 3 different holes for Thellier-Thellier palaeointensity determinations. Induced and remanent magnetization curves measured at low- and high-temperature suggest a diverse and complex magnetic mineralogy, with large variations in Ti content and oxidation state. Hysteresis and FORC measurements show that most samples contain singledomain magnetic grains. After carrying out the palaeointensity determinations, only 9 samples satisfied all reliability criteria. These gave palaeointensity values between 16.5 and 21.5 μT, which correspond to average VDM values of (4.9 ± 0.2) × 1022 Am2 for an estimated age of 140-142 Ma. This value is lower than that for the recent field, which agrees with the hypothesis of a Mesozoic Dipole Low.
ISSN: 0956-540X

hal-00795491
https://hal.archives-ouvertes.fr/hal-00795491
DOI : 10.1093/gji/ggs100

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : International audience
Assessing population connectivity is necessary to construct effective marine protected areas. This connectivity depends, among other parameters, inherently on species dispersal capacities. Isolation by distance (IBD) is one of the main modes of differentiation in marine species, above all in species presenting low dispersal abilities. This study reports the genetic structuring in the tropical hydrozoan Macrorhynchia phoenicea (sensu Postaire et al., 2016a), a brooding species, from 30 sampling sites in the Western Indian Ocean and the Tropical Southwestern Pacific, using 15 microsatellite loci. At the local scale, genet dispersal relied on asexual propagation at short distance, which was not found at larger scales. Considering one representative per clone, significant positive F-IS values (from -0.327*** to 0.411***) were found within almost all sites. Gene flow was extremely low at all spatial scales, among sites within islands (<10km distance) and among islands (100 to >11,000km distance), with significant pairwise F-ST values (from 0.035*** to 0.645***). A general pattern of IBD was found at the Indo-Pacific scale, but also within ecoregions in the Western Indian Ocean province. Clustering and network analyses identified each island as a potential independent population, while analysis of molecular variance indicated that population genetic differentiation was significant at small (within island) and intermediate (among islands within province) spatial scales. As shown by this species, a brooding life cycle might be corollary of the high population differentiation found in some coastal marine species, thwarting regular dispersal at distances more than a few kilometers and probably leading to high cryptic diversity, each island housing independent evolutionary lineages.
ISSN: 2045-7758

hal-01681593
https://hal.archives-ouvertes.fr/hal-01681593
DOI : 10.1002/ece3.3236

Éditeur(s) : Gauthier-villars
Résumé : The submersible-study of four segments of the East Pacific Rise between 17 degrees and 18 degrees 40'S, where the spreading rate is greater than 150 mm/a, allows us to confirm the variability of the accretion processes. The segment between 17 degrees and 17 degrees 30'S shows an intense present-day magmatic activity. The one between 18 degrees 10' and 18 degrees 22'S shows a mainly tectonic activity. The segment between 18 degrees 22' and 18 degrees 37'S is an intermediate stage with an axial graben in which fresh lavas were emplaced by an extremely young eruption. On all the segments the hydrothermal activity exists ranging from shimmering water up to black smokers, It is associated with different stages of animal colonization.
L'étude par le submersible Nautile de quatre segments de la Dorsale Est Pacifique entre 17° et 18°40'S où le taux d'ouverture est de plus de 150 mm/an, permet de confirmer la variabilité des processus de l'accrétion dans le temps et dans l'espace. Le segment compris entre 17° et 17°30'S montre une intense activité magmatique actuelle ou sub-actuelle, celui compris entre 18°10' et 18°22'S montre une activité essentiellement tectonique et celui compris entre 18°22' et 18°37'S une combinaison des deux, le graben d'extension étant partiellement rempli de laves émises lors d'une éruption extrêmement récente. Partout existe une activité hydrothermale, allant de l'émission de fluides moirés à des fumeurs noirs, associée à divers stades de colonisation animale.
Comptes Rendus de l'Academie des Sciences Serie II (1251-8069) (Gauthier-villars), 1994-10 , Vol. 319 , N. 7 , P. 811-818

Droits : Académie des Sciences
http://archimer.ifremer.fr/doc/00183/29458/27840.pdf
http://archimer.ifremer.fr/doc/00183/29458/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : French Polynesia started it's Fish Aggregating Device programme in June 1981 with the positioning of the first buoy offshore of the main island of Tahiti. Since then, 251 structures have been installed throughout the 5 archipelagoes of this French overseas territory. The shape and size of the devices have evolved 8 times over this period, however, a single model has not yet been adopted. Trials are currently underway using lighter structures similar to those found in the Indian Ocean. The anchoring lines have progressively been modified through better knowledge of material and product availability, as well as better understanding of environmental constraints. The programme is entirely financed by the territorial government and managed by the public sector. This ongoing technical assistance, aimed towards the local small-scale coastal fishery, is considered an important factor to maintaining this activity alive. Up until 1997, this economical support policy of outer island populations far from the metropolis central town, along with incidental fishing methods around FADs, have given mitigated results without nevertheless putting into cause this programme. The use of 'drifting handlines' retained at the surface by small indicator floats are one of the contributing factors to the degradation of the anchor lines. It is now commonly accepted that a new fishing strategy must be adopted so that professional coastal fishermen become more aware with regards to an expensive work tool due to local bathymetric conditions, so that fishing effort is increased through the development of better adapted fishing techniques, and finally so that community spirit rules over individualism.Original Abstract: Le programme d'ancrage de DCP en Polynesie francaise a vu le jour en juin 1981 avec l'implantation d'un premier dispositif au large des cotes de Tahiti. Depuis cette date, ce sont 251 structures qui ont ete installees dans les cinq archipels de ce pays d'outre-mer. La forme et la taille des bouees ont evolue huit fois sans etre definitivement arretees a un seul modele et des essais sur des structures legeres de type " Ocean Indien " sont en cours. Les lignes d'ancrage ont fait l'objet de modifications progressives en raison de meilleures connaissances des produits ainsi que des contraintes du milieu environnant. Ce programme est finance en totalite par le territoire de la Polynesie francaise et gere par le secteur public. Il s'adresse a la pecherie artisanale et cotiere qui considere depuis de nombreuses annees cette assistance technique comme un atout indispensable au maintien de son activite. La politique d'engagement de ce soutien economique jusqu'en 1997 aupres des populations d'iles et atolls tres eloignes de la capitale ainsi que l'incidence de la technique de peche la plus repandue autour des DCP ont abouti a des resultats mitiges sans pour autant remettre en cause ce programme. En effet, les lignes a main derivantes et retenues en surface par une petite bouee temoin sont un des principaux facteurs de degradation des lignes d'ancrage. Il est desormais reconnu par tous les intervenants qu'une nouvelle strategie doit etre deployee afin que les pecheurs cotiers professionnels soient mieux responsabilises face a un outil de travail onereux en raison de la bathymetrie environnante, pour que l'effort de peche soit accru par l'utilisation de techniques de peche mieux adaptees, et enfin que l'esprit communautaire prime sur l'individualisme.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15292/12649.pdf
http://archimer.ifremer.fr/doc/00042/15292/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : This paper develops a comparative overview of the development of Fish Aggregating Devices (or fads) by the tropical purse seine fisheries in various ocean areas (Atlantic, Indian, Western and Eastern Pacific Oceans). First, a comparative review of fishery statistics is developed. Recent catches on fads by purse seiners can be estimated at a level of one million tons yearly. This comparison allows to describe the fishing zones and catch trends over time, the species composition and size taken in the various fad fisheries. Skipjack tuna is the dominant species in most fad fisheries, but significant amounts of yellowfin and bigeye are also frequently taken under fads. The paper also presents an overview of various observer data concerning the by-catches of the various fisheries using fads. This comparison allows to estimate the total worldwide yearly by-catches at about 100,000 t, and their species composition in each ocean. The fad technology used in the various oceans by purse seiners is described. The recent use of fads by purse seiners has introduced major uncertainties in most stock assessments, because analyses are hampered by changes in the fishing effort in a fad fishery, by changes in fishing zones and in sizes caught. As a last point, the management of fads presently done or in view by the various tuna bodies are introduced. It appears that the present massive use of fads worldwide is perhaps an unsafe fishing mode, which could produce serious overfishing of many stocks. There is then a consensus that the use of fads needs to be controlled and limited to sustainable biological levels.

Droits : Ifremer
http://archimer.ifremer.fr/doc/00042/15278/12664.pdf
http://archimer.ifremer.fr/doc/00042/15278/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Seismic anisotropy has been widely studied this last decade, particularly by measuring splitting of vertically propagating core shear waves. The main interest in this technique is to characterize upper mantle flow beneath seismic stations. On the other hand, the major restriction in this method is that a single station gives a single anisotropy measurement. Alternative methods have been developed in order to avoid this restriction. An accurate determination of upper mantle seismic anisotropy beneath a seismic station may allow one, by doing anisotropy correction, to characterize remote or deeper anisotropy. The Geoscope network is ideal for this purpose because it is composed of a large set (about 26) of high-quality, broadband seismometers globally distributed and because some of these stations have run for more than 10 years and most of them for more than 5 years. We selected about 100 events at each site, generally of magnitude (m b) > 6.0, and we performed systematic measurements of the splitting parameters (fast polarization direction φ and delay time δt) on SKS, SKKS, and PKS phases. Splitting on oceanic islands has been difficult to observe owing to the low quality of the signal but also perhaps owing to complex upper mantle structures beneath the stations. Station KIP (Kipapa, Hawaii) in the Pacific is the only oceanic Geoscope station with a clear anisotropy. We determined well-constrained splitting parameters for 10 of the 17 continental stations that may be explained by a single anisotropic layer. The poor correlation between fast polarization directions and the absolute plate motion together with the apparent incoherence between the plate velocities and the observed delay times suggest that a simple drag-induced asthenospheric flow alone fails to explain most of the observations. For some stations located on or near major lithospheric structures (TAM, Tamanrasset, Algeria, for instance), we observe a good correlation between fast polarization directions and regional structures. At station SCZ (Santa Cruz, California), we found clear variations of the splitting parameters as a function of the event backazimuth, compatible with two layers of anisotropy. Three stations (CAN (Canberra), HYB (Hyderabad, India) and SSB (Saint Sauveur Badole, France)) seem to be devoid of detectable anisotropy.
ISSN: 2169-9313

hal-01388830
http://hal.univ-reunion.fr/hal-01388830
http://hal.univ-reunion.fr/hal-01388830/document
http://hal.univ-reunion.fr/hal-01388830/file/Barruol_anisoGeoscope_JGR1999.pdf
DOI : 10.1029/1999JB900033

Éditeur(s) : The Japanese Society of Systematic Zoology
Résumé : Prior to this study, two species of ophiuroid had been described from hydrothermal vent sites, and another from methane cold seeps, all from the Atlantic Ocean. Although ophiuroids have occasionally been reported from vents in the Pacific Ocean as well, none has been described before. This study presents two new species, Spinophiura jolliveti gen. et sp. nov., family Ophiuridae, and Ophiolamina eprae gen. et sp. nov., family Ophiacanthidae, which are most likely endemic to reducing environments in the East Pacific. We also include detailed descriptions of the post-metamorphic development of these species. Spinophiura jolliveti is characterized by up to five rather long, semi-erect arm spines and a relatively small oral shield. Its postlarva is unusual in lacking a buccal scale and in that the tooth forms later in development than in all other species the postlarvae of which have been examined. The most characteristic features of O. eprae are the attitude of the three proximal laminar mouth papillae, standing almost vertically on the oral plate, and the presence of two oval, scale-like, distal papillae. Additional migrant (non-vent-endemic) species found at Pacific vent sites are tabularized, but not identified below genus level due to the poor taxonomic state of the Pacific ophiuroid fauna. Biogeographic and ecological issues are discussed.
Species Diversity (1342-1670) (The Japanese Society of Systematic Zoology), 2006-02 , Vol. 11 , N. 1 , P. 7-32

Droits : 2006 The Japanese Society of Systematic Zoology
http://archimer.ifremer.fr/doc/2006/publication-6475.pdf
http://archimer.ifremer.fr/doc/00000/6475/