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Auteur Young, J.W.; Olson, R.J.; Ménard, F.; Kuhnert, P.M.; Duffy, L.M.; Allain, V.; Logan, J.M.; Lorrain, A.; Somes, C.J.; Graham, B.; Goñi, N.; Pethybridge, H.; Simier, M.; Potier, M.; Romanov, E.; Pagendam, D.; Hannides, C.; Choy, C.A. url  doi
openurl 
  Titre Setting the stage for a global-scale trophic analysis of marine top predators: a multi-workshop review Type Article scientifique
  Année 2015 Publication Revue Abrégée Rev Fish Biol Fisheries  
  Volume 25 Numéro 1 Pages (down) 261-272  
  Mots-Clés climate change; Freshwater & Marine Ecology; Global diet data; Global nitrogen model; Global stable isotope data; Predictive analyses; top predators; Tuna trophic ecology; Zoology  
  Résumé Global-scale studies of marine food webs are rare, despite their necessity for examining and understanding ecosystem level effects of climate variability. Here we review the progress of an international collaboration that compiled regional diet datasets of multiple top predator fishes from the Indian, Pacific and Atlantic Oceans and developed new statistical methods that can be used to obtain a comprehensive ocean-scale understanding of food webs and climate impacts on marine top predators. We loosely define top predators not as species at the apex of the food web, but rather a guild of large predators near the top of the food web. Specifically, we present a framework for world-wide compilation and analysis of global stomach-contents and stable-isotope data of tunas and other large pelagic predatory fishes. To illustrate the utility of the statistical methods, we show an example using yellowfin tuna in a “test” area in the Pacific Ocean. Stomach-contents data were analyzed using a modified (bagged) classification tree approach, which is being prepared as an R statistical software package. Bulk δ15N values of yellowfin tuna muscle tissue were examined using a Generalized Additive Model, after adjusting for spatial differences in the δ15N values of the baseline primary producers predicted by a global coupled ocean circulation-biogeochemical-isotope model. Both techniques in tandem demonstrated the capacity of this approach to elucidate spatial patterns of variations in both forage species and predator trophic positions and have the potential to predict responses to climate change. We believe this methodology could be extended to all marine top predators. Our results emphasize the necessity for quantitative investigations of global-scale datasets when evaluating changes to the food webs underpinning top ocean predators under long-term climatic variability.  
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  ISSN 0960-3166, 1573-5184 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1263  
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Auteur Mullon, C.; Guillotreau, P.; Galbraith, E.D.; Fortilus, J.; Chaboud, C.; Bopp, L.; Aumont, O.; Kaplan, D. url  doi
openurl 
  Titre Exploring future scenarios for the global supply chain of tuna Type Article scientifique
  Année 2017 Publication Revue Abrégée Deep Sea Research Part II: Topical Studies in Oceanography  
  Volume 140 Numéro Pages (down) 251-267  
  Mots-Clés climate change; Global supply chain; marine protected area; Scenarios; Tuna  
  Résumé The abundance of tuna, an important top predator that ranges throughout tropical and subtropical oceans, is now largely determined by fishing activity. Fishing activity, in turn, is determined by the interaction of fish availability, fishing capacity, fishing costs and global markets for tuna products. In the face of overfishing, the continued sustainable supply of tuna is likely to require improved global governance, that would benefit from modeling frameworks capable of integrating market forces with the availability of fish in order to consider alternative future projections. Here we describe such a modeling framework, in which we develop several simple, contrasting scenarios for the development of the tuna supply chain in order to illustrate the utility of the approach for global evaluation of management strategies for tuna and other complex, stock-structured fisheries. The model includes multiple national and multi-national fishing fleets, canneries and fresh/frozen markets, and connects these to global consumers using a network of flows. The model is calibrated using recent data on fish catch, cannery and fresh/frozen production, and consumption. Scenarios explore the control on future outcomes in the global tuna fishery by representing, in a simple way, the effects of (1) climate change, (2) changes in the global demand for tuna, and (3) changes in the access to fishing grounds (marine reserves). The results emphasize the potential importance of increasing demand in provoking a global collapse, and suggest that controlling tuna production by limiting technical efficiency is a potential countermeasure. Finally we discuss the outcomes in terms of potential extensions of the scenario approach allowed by this global network model of the tuna supply chain.  
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  ISSN 0967-0645 ISBN Médium  
  Région Expédition Conférence  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2098  
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Auteur Robert, M.; Dagorn, L.; Lopez, J.; Moreno, G.; Deneubourg, J.L. url  doi
openurl 
  Titre Does social behavior influence the dynamics of aggregations formed by tropical tunas around floating objects ? An experimental approach Type Article scientifique
  Année 2013 Publication Revue Abrégée Journal of Experimental Marine Biology and Ecology  
  Volume 440 Numéro Pages (down) 238-243  
  Mots-Clés Aggregation; Binary choice; FADs; Social behavior; tuna  
  Résumé Tropical tunas associate with objects floating at the surface of the ocean, a behavior widely exploited by fishers. However, the respective roles played by environmental variables and behavioral processes (e.g., social behavior) in the formation of these aggregations remain elusive. To investigate the role of social behavior in the dynamics of such aggregations, we used the binary choice approach. The experimental design comprised two close and identical anchored fish aggregating devices (FADS) equipped with an echo sounder buoy to monitor the aggregated biomass of tuna under each device. Analysis of the results entailed characterizing whether the aggregated biomass is distributed asymmetrically (indicative of social behavior playing a role in the dynamics) or symmetrically between the two close and identical FADs, and comparing the results with theoretical distributions based on different definitions of basic units (individual fish or small schools). The results suggest that social interactions underlie aggregation processes, which represents a major advance in our understanding of these aggregations, a priority for science-based fishery management. While recognizing the logistical and technical constraints, we encourage the development of experimental studies (e.g., in which animals are presented with controlled situations) to enhance our understanding of the behavior of large pelagic fish.  
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  ISSN 0022-0981 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 249  
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Auteur Guillotreau, P.; Salladarre, F.; Dewals, P.; Dagorn, L. url  doi
openurl 
  Titre Fishing tuna around Fish Aggregating Devices (FADs) vs free swimming schools : skipper decision and other determining factors Type Article scientifique
  Année 2011 Publication Revue Abrégée Fisheries Research  
  Volume 109 Numéro 2-3 Pages (down) 234-242  
  Mots-Clés Fish Aggregating Devices; Purse-seine; Skipper effect; tuna  
  Résumé Fish Aggregating Devices (FADs) are increasingly used by tuna purse-seine fleets all around the world, modifying the species catch composition. We analyse the determinants of FAD vs free school (FS) fishing, including the skipper effect, and environmental and economic factors. A multivariate and econometric analysis of a panel dataset for the French purse-seine fleet in the Indian Ocean (1980-2007), complemented by a survey of fishers, demonstrates the influential role of climate and prey on FAD fishing and also emphasises individual skipper preference. However, we found that the major determinant of FAD fishing remains the growing fishing capacity (use of bigger vessels, satellite buoys, echo-sounders, supply vessels), thus modifying the species catch composition towards smaller tuna. Other things being equal, raising the proportion of FAD sets by 1% would increase the catches of skipjack by 1.3% and decrease those of large yellowfin tuna by 1.7%. This result shows that the control of effort and investment could be adapted through management measures to encourage one fishing method.  
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  ISSN 0165-7836 ISBN Médium  
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  Numéro d'Appel LL @ pixluser @ collection 143  
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Auteur DRUON, J.-N.; FROMENTIN, J.-M.; AULANIER, F.; HEIKKONEN, J. url  openurl
  Titre Potential feeding and spawning habitats of Atlantic bluefin tuna in the Mediterranean Sea Type Article scientifique
  Année 2011 Publication Marine Ecology-progress Series Revue Abrégée  
  Volume 439 Numéro Pages (down) 223-240  
  Mots-Clés Habitat mapping; Bluefin tuna; Thunnus thynnus; Feeding; Spawning; Mediterranean Sea; Remote sensing; Satellite data  
  Résumé Atlantic bluefin tuna Thunnus thynnus (ABFT) is a fish of high market value which has recently become strongly overexploited, notably in the Mediterranean Sea. This area is an essential habitat for ABFT reproduction and growth. We present here an approach for deriving the daily mapping of potential ABFT feeding and spawning habitats based on satellite-derived sea surface temperature (SST) and chl a concentration. The feeding habitat was mainly derived from the simultaneous occurrence of oceanic fronts of temperature and chl a content while the spawning habitat was mostly inferred from the heating of surface waters. Generally, higher chl a contents were found to be preferred for the feeding habitat and a minimum SST value was found for the spawning habitat. Both habitats were defined by the presence of relevant oceanographic features and are therefore potential and functionally-linked habitats. This approach provides, for the first time, a synoptic view of the potential ABFT habitats in the Mediterranean Sea. The model performs well in areas where both satellite data and ABFT observations are available, as 80% of presence data are in the vicinity of potential habitats. The computed monthly, seasonal and annual maps of potential feeding and spawning habitat of ABFT from 2003 to 2009 are in good agreement with current knowledge on ABFT. Overall, the habitat size of ABFT is about 6% of the Mediterranean Sea surface. The results displayed a strong seasonality in habitat size and locations as well as high year-to-year variations (30 to 60%), particularly for the potential spawning habitat, which is key information for evaluating the utility of ABFT Marine Protected Areas in the Mediterranean Sea.  
  Adresse IFREMER, Ctr Rech Halieut Mediterraneen & Trop, F-34203 Sete, France.  
  Auteur institutionnel Thèse  
  Editeur Inter-research Lieu de Publication Éditeur  
  Langue Langue du Résumé Titre Original  
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  Volume de collection Numéro de collection Edition  
  ISSN 0171-8630 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ 16053 collection 1003  
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