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Auteur Poisson, F.; Filmalter, J.D.; Vernet, A.L.; Dagorn, L. url  doi
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  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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Auteur BAUER, R.; Graewe, U.; Stepputtis, D.; Zimmermann, C.; Hammer, C. url  openurl
  Titre Identifying the location and importance of spawning sites of Western Baltic herring using a particle backtracking model Type Article scientifique
  Année 2014 Publication Revue Abrégée Ices Journal Of Marine Science  
  Volume 71 Numéro 3 Pages 499-509  
  Mots-Clés backtracking; Baltic Sea; Clupea harengus; hatching sites; lagoon; larval transport; spring spawning  
  Résumé The recruitment success of some herring stocks fluctuates strongly, and apparently, success is often already determined during the early life stages, i.e. before metamorphosis. In studying the survival of early life stages and its affecting factors, particularly those during the egg stage, it is crucial to examine the processes at the spawning sites, which often cannot be explored directly. A recent decline in the recruitment of Western Baltic spring-spawning herring (WBSSH) increases the urgency of filling the knowledge gap for this stock, especially because one bottleneck in the recruitment seems to occur before hatching. We examined the successful 20032009 spawning sites of WBSSH in the main spawning ground, the Greifswalder Bodden lagoon. Instead of using common techniques such as diving or underwater videography, which are usually unsuitable for mapping large areas, we applied a model approach. We tracked herring larvae at length 610 mm, recorded by larval surveys during MarchJune of the respective years, back to their hatching sites using a Lagrangian particle backtracking model. We compared the spawning areas identified by the model with the results of earlier field studies; however, we also analysed variations between years, larval length groups, and different applied growth models, which are needed to define hatch-dates. Although spawning sites could not be identified with high precision because of the strong diffusion in the area studied, results indicate that larvae up to 10 mm length are caught near their hatching sites. However, the location of successful spawning sites varied largely between years, with the main hatching sites situated in the Strelasund and the eastern entrance of the lagoon. This may reflect variations in spawning-site selection or quality. A better knowledge of the locations and relative importance of, and the processes occurring on, the different spawning sites will provide an important contribution to the sustainable management of this commercially valuable herring stock.  
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  ISSN 1054-3139 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1136  
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Auteur Potier, M.; Bach, P.; Ménard, F.; Marsac, F. url  doi
openurl 
  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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  Editeur Lieu de Publication Éditeur Barlow, R.; Marsac, F.; Ternon, J.-F.; Roberts, M.  
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  ISSN 0967-0645 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 369  
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Auteur MAHE, K.; VILLANUEVA, C.-M.; VAZ, S.; COPPIN, F.; KOUBBI, P.; CARPENTIER, A. url  openurl
  Titre Morphological variability of the shape of striped red mullet Mullus surmuletus in relation to stock discrimination between the Bay of Biscay and the eastern English Channel Type Article scientifique
  Année 2014 Publication Revue Abrégée Journal Of Fish Biology  
  Volume 84 Numéro 4 Pages 1063-1073  
  Mots-Clés fish body shape; head morphology; morphometric analysis; stock identification; Truss model  
  Résumé Striped red mullet Mullus surmuletus L. 1758 is an economically important species in the Mediterranean Sea and in the northern Atlantic Ocean, where it is exploited from the Bay of Biscay to the southern North Sea (ICES, 2010). In Atlantic waters, there are two main areas where this species is caught, the Bay of Biscay and the eastern English Channel. This species was initially exploited by the Spanish fleets along the Spanish coast inside the Bay of Biscay. Originally considered as valuable by-catch (Marchal, 2008), the growing exploitation ofM. surmuletus and a conspicuous increase in landings in the English Channel and the southern North Sea by French, English and Dutch fleets have been observed from the 1990s onwards. This was attributed to an increase in the migratory distribution and abundance of this species in these areas, which is largely heightened by the decline of traditionally targeted species and the trend for sea water warming (Poulard&Blanchard, 2005; Marchal, 2008; ICES, 2010).  
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  ISSN 0022-1112 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1137  
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Auteur Roberts, M.J.; Ternon, J.-F.; Morris, T. url  doi
openurl 
  Titre Interaction of dipole eddies with the western continental slope of 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 54-67  
  Mots-Clés Chlorophyll filaments; Currents; Dipole eddies; Mozambique Channel; Slope upwelling  
  Résumé Sea Level Anomaly (SLA) data were used to track a southward propagating eddy dipole along the western slope of the Mozambique Channel over some 6 months. In April 2005, this dipole (with the cyclone to the south) was close to the continental slope off southern Mozambique. The contact zone between the contra-rotating vortices and the slope was surveyed by ship using onboard (S-)ADCP and CTD lines. The data showed strong ( > 1.4 m s(-1)) southward (geostrophic) currents over the slope adjacent to the anticyclone with horizontal divergence over the shelf edge. Significant slope upwelling between the dipole and the shelf was evident, concomitant with enhanced nutrient and chlorophyll levels enriching shelf near-surface waters. Satellite observations depicted a 300 km long surface chlorophyll filament extending offshore in the frontal zone between the contra-rotating vortices. A satellite-tracked drifter deployed at the coastal base of this filament confirmed the offshore advection of chlorophyll-enriched shelf water, which ultimately wrapped around the cyclone and filling its centre. The slope upwelling was also clearly evident in hourly temperature data collected by a recorder deployed on a nearby reef (Zambia Reef) in a depth of 18 m. According to the SLA data, the dipole took several weeks to pass Zambia Reef causing prolonged bouts of upwelling that finally ceased when it left the continental slope and moved southwards into the open ocean. Further analysis showed that lone anticyclones and cyclones against the Mozambique continental shelf also induce slope upwelling as a result of horizontal divergence created by the radial circulation of the vortex. In the case of cyclones, the divergence occurs north of the contact zone. Overall, this case study confirms that eddies moving southwards along the western side of the Mozambique Channel are the main mechanism for pumping nutrients into the otherwise oligotrophic surface waters, and moreover, provide a vigorous mechanism for shelf-open ocean exchange.  
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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  
  Région Expédition Conférence  
  Notes (up) Approuvé pas de  
  Numéro d'Appel LL @ pixluser @ collection 370  
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