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Auteur Fromentin, J.-M.; Bonhommeau, S.; Arrizabalaga, H.; Kell, L.T.
Titre The spectre of uncertainty in management of exploited fish stocks: The illustrative case of Atlantic bluefin tuna Type Article scientifique
Année (down) 2014 Publication Revue Abrégée Marine Policy
Volume 47 Numéro Pages 8-14
Mots-Clés tuna
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Volume de collection Numéro de collection Edition
ISSN 0308-597x ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 323
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Auteur Dueri, S.; Bopp, L.; Maury, O.
Titre Projecting the impacts of climate change on skipjack tuna abundance and spatial distribution Type Article scientifique
Année (down) 2014 Publication Revue Abrégée Global Change Biology
Volume 20 Numéro 3 Pages 742-753
Mots-Clés Apecosm-E; Atlantic Ocean; global warming; Indian Ocean; Katsuwonus pelamis; Pacific Ocean; scenario; Tropical tuna
Résumé Climate-induced changes in the physical, chemical, and biological environment are expected to increasingly stress marine ecosystems, with important consequences for fisheries exploitation. Here, we use the APECOSM-E numerical model (Apex Predator ECOSystem Model – Estimation) to evaluate the future impacts of climate change on the physiology, spatial distribution, and abundance of skipjack tuna, the worldwide most fished species of tropical tuna. The main novelties of our approach lie in the mechanistic link between environmental factors, metabolic rates, and behavioral responses and in the fully three dimensional representation of habitat and population abundance. Physical and biogeochemical fields used to force the model are provided by the last generation of the IPSL-CM5 Earth System Model run from 1990 to 2100 under a &8216;business-as-usual&8217; scenario (RCP8.5). Our simulations show significant changes in the spatial distribution of skipjack tuna suitable habitat, as well as in their population abundance. The model projects deterioration of skipjack habitat in most tropical waters and an improvement of habitat at higher latitudes. The primary driver of habitat changes is ocean warming, followed by food density changes. Our projections show an increase of global skipjack biomass between 2010 and 2050 followed by a marked decrease between 2050 and 2095. Spawning rates are consistent with population trends, showing that spawning depends primarily on the adult biomass. On the other hand, growth rates display very smooth temporal changes, suggesting that the ability of skipjack to keep high metabolic rates in the changing environment is generally effective. Uncertainties related to our model spatial resolution, to the lack or simplification of key processes and to the climate forcings are discussed.
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Volume de collection Numéro de collection Edition
ISSN 1354-1013 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 327
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Auteur Jaquemet, S.; Ternon, J.-F.; Kaehler, S.; Thiebot, J.B.; Dyer, B.; Bemanaja, E.; Marteau, C.; Le Corre, M.
Titre Contrasted structuring effects of mesoscale features on the seabird community in the Mozambique Channel Type Article scientifique
Année (down) 2014 Publication Revue Abrégée Deep-Sea Research Part II.Topical Studies in Oceanography
Volume 100 Numéro No spécial Pages 200-211
Mots-Clés Foraging habitats; Frigatebird; Marine productivity; Mesoscale eddies; Red-footed booby; Sooty tern; Tropical marine predators; Tuna; Western Indian Ocean
Résumé The Mozambique Channel (western Indian Ocean) is a dynamic environment characterised by strong mesoscale features, which influence all biological components of the pelagic ecosystem. We investigated the distribution, abundance and feeding behaviour of seabirds in the Mozambique Channel in relation to physical and biological environmental variables, with a specific interest in mesoscale features. Seabird censuses were conducted in summer and winter during 7 cruises in the southern and northern Mozambique Channel. Tropical species accounted for 49% of the 37 species identified and 97% of the individuals, and species from the sub-Antarctic region constituted 30% of the identifications. The typically tropical sooty tern (Onychoprion fuscata) was the dominant species during all cruises, and overall accounted for 74% of the species observations and 85% of counted birds. Outputs of Generalised Linear Models at the scale of the Mozambique Channel suggested that higher densities of flying and feeding birds occurred in areas with lower sea surface temperatures and lower surface chlorophyll a concentrations. Most of the flocks of feeding birds did not associate with surface schools of fish or marine mammals, but when they did, these flocks were larger, especially when associated with tuna. While tropical species seemed to favour cyclonic eddies, frontal and divergence zones, non-tropical species were more frequently recorded over shelf waters. Sooty terns foraged preferentially in cyclonic eddies where zooplankton, micronelcton and tuna schools were abundant. Among other major tropical species, frigatebirds (Fregata spp.) predominated in frontal zones between eddies, where tuna schools also frequently occurred and where geostrophic currents were the strongest. Red-footed boobies (Sula sub) concentrated in divergence zones characterised by low sea level anomalies, low geostrophic currents, and high zooplanlcton biomass close to the surface. Our results highlight the importance of mescoscale features in structuring the tropical seabird community in the Mozambique Channel, in addition to segregating tropical and non-tropical species. The mechanisms underlying the segregation of tropical seabirds seem to partially differ from that of other tropical regions, and this may be a consequence of the strong local mesoscale activity, affecting prey size and availability schemes. Beyond characterising the foraging habitats of the seabird community of the Mozambique Channel, this study highlights the importance of this region as a hot spot for seabirds; especially the southern part, where several endangered sub-Antarctic species over-winter.
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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
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Numéro d'Appel LL @ pixluser @ collection 363
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Auteur NIEBLAS, A.-E.; DEMARCQ, H.; DRUSHKA, K.; SLOYAN, B.; BONHOMMEAU, S.
Titre Front variability and surface ocean features of the presumed southern bluefin tuna spawning grounds in the tropical southeast Indian Ocean Type Article scientifique
Année (down) 2014 Publication Revue Abrégée Deep-sea Research Part II-topical Studies In Oceanography
Volume 107 Numéro Pages 64-76
Mots-Clés Front detection index; Indo-Australian region; Oceanic fronts; Southern bluefin tuna Thunnus maccoyii; Spawning grounds (10 degrees S-20 degrees S 105 degrees E-125 degrees E); Tropical southeast Indian Ocean
Résumé The southern bluefin tuna (SBT, Thunnus maccoyii) is an ecologically and economically valuable fish. However, surprisingly little is known about its critical early life history, a period when mortality is several orders of magnitude higher than at any other life stage, and when larvae are highly sensitive to environmental conditions. Ocean fronts can be important in creating favourable spawning conditions, as they are a convergence of water masses with different properties that can concentrate planktonic particles and lead to enhanced productivity. In this study, we examine the front activity within the only region where SBT have been observed to spawn: the tropical southeast Indian Ocean between Indonesia and Australia (10 degrees S-20 degrees S, 105 degrees E-125 degrees E). We investigate front activity and its relationship to ocean dynamics and surface features of the region. Results are also presented for the entire Indian Ocean (30 degrees N-45 degrees S, 20 degrees E-140 degrees E) to provide a background context. We use an extension of the Cayula and Cornillon algorithm to detect ocean fronts from satellite images of sea surface temperature (SST) and chlorophyll-a concentration (chl-a). Front occurrence represents the probability of occurrence of a front at each pixel of an image. Front intensity represents the magnitude of the difference between the two water masses that make up a front. Relative to the rest of the Indian Ocean, both SST and chl-a fronts in the offshore spawning region are persistent in occurrence and weak in intensity. Front occurrence and intensity along the Australian coast are high, with persistent and intense fronts found along the northwest and west coasts. Fronts in the tropical southeast Indian Ocean are shown to have strong annual variability and some moderate interannual variability. SST front occurrence is found to lead the Southern Oscillation Index by one year, potentially linked to warming and wind anomalies in the Indian Ocean. The surface ocean characteristics of the offshore SBT spawning region are found to be particularly stable compared to the rest of the Indian Ocean in terms of stable SST, low eddy kinetic energy, i.e., low mesoscale eddy activity, and low chl-a. However, this region has high front occurrence, but low front intensity of both SST and chl-a fronts. The potential impact of these oceanic features for SBT spawning is discussed.
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Editeur Lieu de Publication Éditeur
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 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1131
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Auteur Kaplan, D.; Chassot, E.; Amande, J.M.; Dueri, S.; Demarcq, H.; Dagorn, L.; Fonteneau, A.
Titre Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives Type Article scientifique
Année (down) 2014 Publication Revue Abrégée Ices Journal of Marine Science
Volume 71 Numéro 7 Pages 1728-1749
Mots-Clés Bycatch; conservation; Indian Ocean; Marine protected areas (MPAs); pelagic; spatial management of fisheries; tropical tuna fisheries
Résumé Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, by catch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.
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Volume de collection Numéro de collection Edition
ISSN 1054-3139 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1199
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