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Auteur Bodin, N.; Lesperance, D.; Albert, R.; Hollanda, S.; Michaud, P.; Degroote, M.; Churlaud, C.; Bustamante, P. doi  openurl
  Titre Trace elements in oceanic pelagic communities in the western Indian Ocean Type Article scientifique
  Année 2017 Publication Revue Abrégée Chemosphere  
  Volume 174 Numéro Pages 354-362  
  Mots-Clés atlantic-ocean; blue marlin; Environmental risk assessment; makaira-nigricans; Marine fish; Mediterranean Sea; Mercury; mercury content; North Pacific; risk-assessment; Seafood; Selenium; swordfish xiphias-gladius; Tuna fisheries' bycatch  
  Résumé The mineral composition of target and non-target pelagic fish caught by purse-seiners and longliners in the western-central Indian Ocean was determined. From the 10 essential elements analysed, selenium and zinc showed the highest concentrations in swordfish and blue marlin while Indian mackerel appeared as a good source of copper, iron and chrome. All catch had levels of lead and cadmium, two toxic elements, below the maximum sanitary limits. Although some concerns were raised regarding mercury concentrations in the largest species (wahoo, swordfish and blue marlin), molar ratios of mercury and selenium indicate that all oceanic pelagic fish from the western-central Indian Ocean are safe for human consumption. This study also gives insights on the relationships between the levels of essential and toxic elements in fish muscle and the size, trophic position and diet sources of the studied pelagic species. (C) 2017 Elsevier Ltd. All rights reserved.  
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  ISSN (up) 0045-6535 ISBN Médium  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 2119  
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Auteur Keller, S.; Quetglas, A.; Puerta, P.; Bitetto, I.; Casciaro, L.; Cuccu, D.; Esteban, A.; Garcia, C.; Garofalo, G.; Guijarro, B.; Josephides, M.; Jadaud, A.; Lefkaditou, E.; Maiorano, P.; Manfredi, C.; Marceta, B.; Micallef, R.; Peristeraki, P.; Relini, G.; Sartor, P.; Spedicato, M.T.; Tserpes, G.; Hidalgo, M. doi  openurl
  Titre Environmentally driven synchronies of Mediterranean cephalopod populations Type Article scientifique
  Année 2017 Publication Revue Abrégée Prog. Oceanogr.  
  Volume 152 Numéro Pages 1-14  
  Mots-Clés atlantic bluefin tuna; balearic sea; Cephalopods; Dynamic factor analysis; ecological niche approach; fisheries; fluctuations; hake merluccius-merluccius; Illex coindetii; life-history; Mediterranean; medits; octopus; Octopus vulgaris; squid; Synchrony; time-series  
  Résumé The Mediterranean Sea is characterized by large scale gradients of temperature, productivity and salinity, in addition to pronounced mesoscale differences. Such a heterogeneous system is expected to shape the population dynamics of marine species. On the other hand, prevailing environmental and climatic conditions at whole basin scale may force spatially distant populations to fluctuate in synchrony. Cephalopods are excellent case studies to test these hypotheses owing to their high sensitivity to environmental conditions. Data of two cephalopod species with contrasting life histories (benthic octopus vs nectobenthic squid), obtained from scientific surveys carried out throughout the Mediterranean during the last 20 years were analyzed. The objectives of this study and the methods used to achieve them (in parentheses) were: (i) to investigate synchronies in spatially separated populations (decorrelation analysis); (ii) detect underlying common abundance trends over distant regions (dynamic factor analysis, DFA); and (iii) analyse putative influences of key environmental drivers such as productivity and sea surface temperature on the population dynamics at regional scale (general linear models, GLM). In accordance with their contrasting spatial mobility, the distance from where synchrony could no longer be detected (decorrelation scale) was higher in squid than in octopus (349 vs 217 km); for comparison, the maximum distance between locations was 2620 km. The DFA revealed a general increasing trend in the abundance of both species in most areas, which agrees with the already reported worldwide proliferation of cephalopods. DFA results also showed that population dynamics are more similar in the eastern than in the western Mediterranean basin. According to the GLM models, cephalopod populations were negatively affected by productivity, which would be explained by an increase of competition and predation by fishes. While warmer years coincided with declining octopus numbers, areas of high sea surface temperature showed higher densities of squid. Our results are relevant for regional fisheries management and demonstrate that the regionalisation objectives envisaged under the new Common Fishery Policy may not be adequate for Mediterranean cephalopod stocks. (C) 2017 Elsevier Ltd. All rights reserved.  
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  ISSN (up) 0079-6611 ISBN Médium  
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Auteur Dagorn, L.; Holland, K.N.; Filmalter, J. url  doi
openurl 
  Titre Are drifting FADs essential for testing the ecological trap hypothesis ? Type Article scientifique
  Année 2010 Publication Revue Abrégée Fisheries Research  
  Volume 106 Numéro Pages 60-63  
  Mots-Clés ecological; Fad; hypothesis; trap; Tunas  
  Résumé Because tropical tunas are known to aggregate around floating objects, it has been suggested that the large number of drifting fish aggregating devices (FADS) built and deployed by purse seiners could act as an 'ecological trap'. This hypothesis states that these networks of drifting FADS could take fish to areas where they would not normally go or retain them in places that they would otherwise leave. Because the ecological trap hypothesis was first advanced for drifting FADs, some have argued that only studies using drifting FADs can test this hypothesis. However, because working with drifting FADs is difficult, accepting this precept would preclude the scientific community from providing urgently needed information to organizations charged with management of fisheries that exploit drifting FADs. We argue that because both anchored and drifting FADs alter the natural environment, the more easily accessible anchored FADs can be used to test the ecological trap hypothesis. Also, based on a comparative scientific approach, we argue that understanding the behaviour of tunas around anchored FADs can improve our general understanding of tunas around all types of floating objects and help design new, well focused studies for drifting FADs. As anchored FADs are easier to access and offer a greater potential for research, we encourage scientists to design and conduct studies (in particular on the behaviour of fish at FADS) around the moored structures.  
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Auteur Gaertner, D.; Hallier, J.-P. url  doi
openurl 
  Titre Tag shedding by tropical tunas in the Indian Ocean and other factors affecting the shedding rate Type Article scientifique
  Année 2015 Publication Fisheries Research Revue Abrégée  
  Volume 163 Numéro Si Pages 98-105  
  Mots-Clés averaging; Bayesian model; Beta-binomial model; Indian Ocean; Shedding rate; Tagging data; Tropical tunas  
  Résumé A key objective of the Regional Tuna Tagging Project Indian Ocean was to estimate tag-shedding rates, Type-I (immediate tag shedding) and Type-II (long-term tag shedding). To assess this, a series of double-tagging experiments (26,899 double tags released with 4555 recoveries) were conducted as part of the broader tagging program. After omitting data from tags placed by less experienced taggers, the results of our analyses did not show any evidence that individual differences between taggers (i.e., a tagger effect) impacted estimates of tag-shedding rates. However, it was shown that the probability of retaining the second tag (inserted in the left side of the fish) was larger than retaining the first tag (inserted in the right side, i.e., the side typically tagged in single-tagging experiments). We used a Bayesian model averaging approach to account for model uncertainty in the estimates of the parameters a and L used to calculate the probability of tag retention Q(t)= alpha e-((L t)) for the right tag. The parameter estimates were alpha = 0.993 and L (per year) = 0.030 (skipjack); alpha = 0.972 and L (per year) = 0.040 (yellowfin); and alpha = 0.990 and L (per year) = 0.021 (bigeye). These results agree with estimates obtained by other large-scale tropical tuna tagging projects. We showed that tag loss has a moderate impact on the underestimation of the exploitation rate (bias = 2-6% depending on the tuna species). However, non-reporting leads to a bias of around 7% when using the high reporting rate estimate of purse seiners. Finally, tag shedding (specifically Type-II shedding) modified the individual weights of the samples of recaptures. Consequently, the total instantaneous mortality estimates (Z; calculated from mean times-at-large) were reduced by a range of 1-3%.  
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  Editeur Lieu de Publication Éditeur Murua, H.; Marsac, F.; Eveson, J.P.  
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  ISSN (up) 0165-7836 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1104  
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Auteur Lucena Frédou, F.; Frédou, T.; Gaertner, D.; Kell, L.; Potier, M.; Bach, P.; Travassos, P.; Hazin, F.; Ménard, F. url  doi
openurl 
  Titre Life history traits and fishery patterns of teleosts caught by the tuna longline fishery in the South Atlantic and Indian Oceans Type Article scientifique
  Année 2016 Publication Revue Abrégée Fisheries Research  
  Volume 179 Numéro Pages 308-321  
  Mots-Clés Bycatch; Fishing impact; Tuna; Billfish; Ecosystem based fisheries management  
  Résumé The identification and mitigation of adverse effects of the bycatch of tuna longline fishery have been mainly developed and implemented for seabirds, sharks and turtles and, the knowledge on teleost bycatch for this fishery, remains very poor. This paper contributes to a comprehensive assessment of life history traits and fishery attributes of target and bycatch species caught by the tuna longline fishery in the South Atlantic and Indian Oceans. Data was compiled on seven life history traits and three fishery attributes for 33 and 27 teleost stocks caught by longliners in South Atlantic and Indian Oceans, respectively. In addition, each species was assigned into four categories describing the fate of the catch: target species for commercial use, bycatch species kept for consumption, bycatch species kept for commercial use and discarded bycatch. Life history traits and fishery attributes did not differ between oceans. However, non-target but commercialized species were smaller in the Atlantic Ocean. Teleosts caught by the tuna longline fishery was segregated into three main groups: (1) the fast growing species represented mainly by dolphinfishes (Coryphaena hippurus and C. equisellis), skipjack tuna (Katsuwonus pelamis), kawakawa (Euthynnus affinis), bullet tuna (Auxis rochei), snoek (Thyrsites atun) and blackfin tuna (Thunnus atlanticus); (2) target tunas and most other bycatch species which were part of an intermediate group and (3) billfishes including swordfish representing the large and slow growing species with moderate to high market values and unknown or highly uncertain stock status. Investment in some key life history traits (such as growth coefficient) and the development of quantitative or semi-quantitative approaches (stock assessment and Ecological Risk Assessment) should be priorized as precautionary management measures for these species.  
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