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Auteur Dueri, S.; Guillotreau, P.; Jiménez-Toribio, R.; Oliveros-Ramos, R.; Bopp, L.; Maury, O. url  doi
openurl 
  Titre Food security or economic profitability? Projecting the effects of climate and socioeconomic changes on global skipjack tuna fisheries under three management strategies Type Article scientifique
  Année 2016 Publication Revue Abrégée Global Environmental Change  
  Volume 41 Numéro Pages 1-12  
  Mots-Clés (up) Bioeconomic model; climate change; fishery management; Mey; Msy; Skipjack tuna  
  Résumé We investigate the interactions between anthropogenic climate change, socioeconomic developments and tuna fishery management strategies. For this purpose, we use the APECOSM-E model to map the effects of climate change and commercial fishing on the distribution of skipjack tuna biomass in the three oceans, combined with a new bioeconomic module representing the rent or profit of skipjack fisheries. For forcing, we use Representative Concentration Pathway (RCP) 8.5, the highest emission scenario for greenhouse gas concentrations presented in the IPCC’s Fifth Assessment Report (AR5), and the IPCC Socioeconomic Shared Pathway (SSP) 3, which is characterized by low economic development and a strong increase in the world population. We first investigate the impact of climate change on regional skipjack abundance, catches and profits in three oceans (Atlantic, Indian and Pacific) in 2010, 2050 and 2095. We then study the effects of three management strategies (maximum sustainable yield or MSY, maximum economic yield or MEY, and zero rent or ZR) on the future distribution of fishing fleets between oceans and on global economic rent. Our model projections for 2050 and 2095 show an increase in global skipjack biomass compared to 2010 and major changes in its distribution, impacting local and regional fishing efforts. The Pacific Ocean will continue to dominate the skipjack market. In our modeling of management strategies, the currently predominant MSY strategy would have been unprofitable in 2010, due to a decreased catch per unit effort (CPUE). In the future, however, technological developments should increase fishing efficiency and make MSY profitable. In all the scenarios, a MEY strategy is more profitable than MSY but leads to the lowest catches and the highest prices. This raises ethical questions in a world where food security may become a top priority. In the scenarios where MSY generates an economic loss (e.g. 2010), a ZR strategy allows global stocks to be exploited at high but still profitable levels. Conversely, in the scenarios where MSY is profitable, (e.g. 2095) ZR leads to overfishing and smaller global catches. We conclude that the most appropriate management strategy at any time is likely to change as environmental and socioeconomic conditions evolve. The decision to follow one or other strategy is a complex one that must be regularly reviewed and updated.  
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  ISSN 0959-3780 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1601  
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Auteur Annasawmy, P.; Cherel, Y.; Romanov, E.; Le Loc'h, F.; Menard, F.; Ternon, J.-F.; Marsac, F. doi  openurl
  Titre Stable isotope patterns of mesopelagic communities over two shallow seamounts of the south-western Indian Ocean Type Article scientifique
  Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.  
  Volume 176 Numéro Pages 104804  
  Mots-Clés (up) biogeochemical provinces; Crustaceans; delta C-13; delta N-15; discrimination factors; feeding ecology; Fish; food-web structure; Micronekton; mozambique channel; particulate organic-matter; Squid; Trophic level; trophic structure; vertical-distribution; water column; yellowfin tuna  
  Résumé The stable carbon (delta C-13) and nitrogen (delta N-15) isotope values of soft tissues of micronekton (crustaceans, squid, mesopelagic fish) and zooplankton were measured from organisms collected on the RV Antea at two seamounts located in the south-western Indian Ocean: La Perouse (summit depth similar to 60 m) and “MAD-Ridge” (thus named in this study; summit depth similar to 240 m). Surface particulate organic matter (POM-Surf) showed higher delta C-13 at the more productive MAD-Ridge than at the oligotrophic La Perouse seamount. Particulate organic matter and zooplankton were depleted in N-15 at La Pemuse pinnacle compared with MAD-Ridge. Gelatinous organisms and crustaceans occupied the lowest and intermediate tmphic levels (TL similar to 2 and 3 respectively) at both seamounts. Mesopelagic fish and smaller-sized squid sampled at both seamounts occupied TL similar to 3 to 4, whereas the large nektonic squid, Ommastrephes bartramii, collected at MAD-Ridge only, exhibited a TL of similar to 5. The delta N-15 values of common open-water mesopelagic taxa were strongly influenced by specimen size and feeding habits at both seamounts, with an increase in delta N-15 values with increasing size. Carnivorous fish species sampled exclusively over the seamounts' flanks and summits exhibited TL values of similar to 4, irrespective of their wide size ranges. The work could not demonstrate any differences in delta C-13 values of mesopelagic fish between the seamounts and the surrounding oceanic areas. The study segregated clusters of mesopelagic organisms according to their delta C-13 and delta N-15 values, with variations in stable isotope values reflecting a complex range of processes possibly linked to productivity as well as biological and ecological traits of the species (size and feeding mode).  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2835  
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Auteur Roberts, M.J.; Ternon, J.-F.; Marsac, F.; Noyon, M.; Payne, A.I.L. doi  openurl
  Titre The MADRidge project: Bio-physical coupling around three shallow seamounts in the South West Indian Ocean Type Article scientifique
  Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.  
  Volume 176 Numéro Pages 104813  
  Mots-Clés (up) Biological productivity; biology; Current-topography interaction; dipoles; fisheries; Fisheries and governance; Foodweb; humpback whales; hypothesis; La Perouse; madagascar; Madagascar Ridge; seabird community; Seamounts; tuna; upwelling cell; variability; Walters Shoal  
  Résumé Compared with other ocean basins, little is known scientifically about the seamounts in the Indian Ocean. Nonetheless, fishers have plundered these fragile ecosystems for decades, and now mining is becoming a reality. We introduce a multidisciplinary project referred to as MAD-Ridge that recently focused on three shallow seamounts in the South West Indian Ocean between 19 degrees S and 34 degrees S. The larger Walters Shoal (summit at 18 m) discovered in 1963 occupies the southern part of the Madagascar Ridge and has long received attention from the fishing industry, and only recently by scientists. In contrast, nothing is known of the northern region of the ridge, which is characterised by a prominent, steep-sided seamount that has a flat circular summit at 240 m and width of similar to 20 km. This seamount is some 200 km south of Madagascar and unnamed; it is referred to here as the MAD-Ridge seamount. MAD-Ridge is the shallowest of a constellation of five deeper (>1200 m) seamounts on that part of the ridge, all within the EEZ of Madagascar. It lies in a highly dynamic region at the end of the East Madagascar Current, where mesoscale eddies are produced continuously, typically as dipoles. The Madagascar Ridge appears to be an area of great productivity, as suggested by the foraging behaviour of some tropical seabirds during chick-rearing and a longline fishery that operates there. The third seamount, La Perouse, is located between Reunion Island and Madagascar. With a summit 60 m below the sea surface, La Perouse is distinct from MAD-Ridge and Walters Shoal; it is a solitary pinnacle surrounded by deep abyssal plains and positioned in an oligotrophic region with low mesoscale activities. The overall aim of the MAD-Ridge project was to examine the flow structures induced by the abrupt topographies, and to evaluate whether biological responses could be detected that better explain the observed increased in fish and top predator biomasses. The MAD-Ridge project comprised a multidisciplinary team of senior and early career scientists, along with postgraduate students from France, South Africa, Mauritius and Madagascar. The investigation was based around three cruises using the French vessels RV Antea (35 m) and RV Marion Dufresne (120 m) in September 2016 (La Perouse), November-December 2016 (MAD-Ridge) and May 2017 (Walters Shoal). This manuscript presents the rationale for the MAD-Ridge project, the background, a description of the research approach including the cruises, and a synopsis of the results gathered in the papers published in this Special Issue.  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2856  
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Auteur Fonteneau, A.; Pereira, J.G. url  doi
openurl 
  Titre Analysis of the Daily Catch and Effort Data of the Bluefin (Thunnus Thynnus) Algarve Trap Fishery During the Years 1898–1900 Type Article scientifique
  Année 2012 Publication Revue Abrégée Aquatic Living Resources  
  Volume FirstView Numéro Pages  
  Mots-Clés (up) Bluefin tuna; Daily catches; East Atlantic; Fish behaviour; Fish trap; Historical survey; Portugal; Spawning migration pattern  
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  Numéro d'Appel LL @ pixluser @ collection 187  
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Auteur Mariani, P.; Křivan, V.; MacKenzie, B.R.; Mullon, C. url  doi
openurl 
  Titre The migration game in habitat network: the case of tuna Type Article scientifique
  Année 2016 Publication Revue Abrégée Theor Ecol  
  Volume 9 Numéro 2 Pages 219-232  
  Mots-Clés (up) Bluefin tuna; Game theory; Habitat selection; Ideal free distribution; Plant Sciences; Structured population; Theoretical Ecology/Statistics; Zoology  
  Résumé Long-distance migration is a widespread process evolved independently in several animal groups in terrestrial and marine ecosystems. Many factors contribute to the migration process and of primary importance are intra-specific competition and seasonality in the resource distribution. Adaptive migration in direction of increasing fitness should lead to the ideal free distribution (IFD) which is the evolutionary stable strategy of the habitat selection game. We introduce a migration game which focuses on migrating dynamics leading to the IFD for age-structured populations and in time varying habitats, where dispersal is costly. The model predicts migration dynamics between these habitats and the corresponding population distribution. When applied to Atlantic bluefin tunas, it predicts their migration routes and their seasonal distribution. The largest biomass is located in the spawning areas which have also the largest diversity in the age-structure. Distant feeding areas are occupied on a seasonal base and often by larger individuals, in agreement with empirical observations. Moreover, we show that only a selected number of migratory routes emerge as those effectively used by tunas.  
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  ISSN 1874-1738, 1874-1746 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1465  
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