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Caro, A., Escalas, A., Bouvier, C., Grousset, E., Lautredou-Audouy, N., Roques, C., et al. (2012). Epibiotic bacterial community of Sphaeroma serratum (Crustacea, Isopoda): relationship with molt status. Mar. Ecol.-Prog. Ser., 457, 11–27.
Résumé: Sphaeroma serratum is a marine isopod species that inhabits seashores from Europe to West Africa. The individuals live under stones in direct contact with reduced sediments and harbour a diverse bacterial community on the cuticle of their pleopods. We investigated the diversity of these epibiotic bacteria on male (pubescent and senescent) and female specimens with electron microscopic observations and molecular tools. The microbial community of S. serratum was shown to be composed of at least 5 bacterial morphotypes observed on the pleopodal cuticle in all male specimens. Using fluorescence in situ hybridization, we identified 5 major phylogenetic groups (alpha-, beta-, gamma- and delta-Proteobacteria and Archaea) whereas denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments of epibiotic bacteria revealed 50 bands. The bacterial community associated with S. serratum seems more diverse than in other marine crustaceans, such as Rimicaris. The relative diversity of this bacterial community was also studied in relation to the molt cycle. The comparison of DGGE band patterns of several individuals from female, pubescent male and senescent male groups revealed that the bacterial community diversity was dependent on the sex and the age of the individuals and more generally on the molt status.
Mots-Clés: 16s ribosomal-rna; Crustacean; DGGE band pattern; Epibiotic biofilm; Molt cycle; Sphaeroma; fish; gastropod; gradient gel-electrophoresis; hydrothermal-vent; in-situ hybridization; mid-atlantic ridge; oxidizing bacteria; phylogenetic diversity; riftia-pachyptila; shrimp rimicaris-exoculata; urothoe-poseidonis
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Amandé, M., Ariz, J., Chassot, E., Molina, A. D. de, Gaertner, D., Murua, H., et al. (2010). Bycatch of the European purse seine tuna fishery in the Atlantic Ocean for the 2003-2007 period. Aquatic Living Resources, 23(4), 353–362.
Résumé: Bycatch of several groups of species and their characteristics are presented for the period 2003 to 2007 for the European purse seine tuna fishery operating in the Atlantic Ocean. Data were collected through French and Spanish observer programmes and represented a total of 27 trips corresponding to 2.9% coverage. Bycatch is defined as non-targeted species and small or damaged target species. Bycatch species composition, main species length, sex ratio and the fate of the most common species are presented first. Stratified ratios relative to landings of major commercial tunas were then used to estimate the total bycatch; these ratios were considered the most appropriate variable for extrapolation. Stratification was based on the fishing mode (free school vs. floating object), season (quarters) and spatial areas. The annual average bycatch was estimated at about 6400 t, corresponding to a mean annual value of 80.8 t per 1000 t of tuna landed or 7.5% of the total catch. Tunas represent 83% (67.2 t/1000 t) of the total bycatch, followed by other bony fishes (10%, 7.8 t/1000 t), billfishes (5%, 4.0 t/1000 t), sharks (1%, 0.9 t/1000 t) and rays (1%, 0.9 t/1000 t). Based on estimates of the annual bycatch, 16% was kept on board and sold in local markets.
Mots-Clés: atlantic Ocean; Bycatch; discards; Purse seining; Tuna fisheries
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Dueri, S., Bopp, L., & Maury, O. (2014). Projecting the impacts of climate change on skipjack tuna abundance and spatial distribution. Global Change Biology, 20(3), 742–753.
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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Bodin, N., Lesperance, D., Albert, R., Hollanda, S., Michaud, P., Degroote, M., et al. (2017). Trace elements in oceanic pelagic communities in the western Indian Ocean. Chemosphere, 174, 354–362.
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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Darnaude, A. M., & Hunter, E. (2018). Validation of otolith delta O-18 values as effective natural tags for shelf-scale geolocation of migrating fish. Mar. Ecol.-Prog. Ser., 598, 167–185.
Résumé: The oxygen isotopic ratio of fish otoliths is increasingly used as a 'natural tag' to assess provenance in migratory species, with the assumption that variations in delta O-18 values closely reflect individual ambient experience of temperature and/or salinity. We employed archival tag data and otoliths collected from a shelf-scale study of the spatial dynamics of North Sea plaice Pleuronectes platessa L., to examine the limits of otolith delta O-18-based geolocation of fish during their annual migrations. Detailed intra-annual otolith delta O-18 measurements for 1997-1999 from individuals of 3 distinct sub-stocks with different spawning locations were compared with delta O-18 values predicted at the monthly, seasonal and annual scales, using predicted sub-stock specific temperatures and salinities over the same years. Spatio-temporal variation in expected delta O-18 values (-0.23 to 2.94%) mainly reflected variation in temperature, and among-zone discrimination potential using otolith delta O-18 varied greatly by temporal scale and by time of year. Measured otolith delta O-18 values (-0.71 to 3.09%) largely mirrored seasonally predicted values, but occasionally fell outside expected delta O-18 ranges. Where mismatches were observed, differences among sub-stocks were consistently greater than predicted, suggesting that in plaice, differential sub-stock growth rates and physiological effects during oxygen fractionation enhance geolocation potential using otolith delta O-18. Comparing intra-annual delta O-18 values over several consecutive years for individuals with contrasted migratory patterns corroborated a high degree of feeding and spawning site fidelity irrespective of the sub-stock. Informed interpretation of otolith delta O-18 values can therefore provide relatively detailed fisheries-relevant data not readily obtained by conventional means.
Mots-Clés: atlantic bluefin tuna; carbon stable-isotopes; cod gadus-morhua; Fish migration; life-history; Natural tag; north-sea plaice; Oxygen; oxygen-isotope fractionation; Plaice; Pleuronectes platessa; pleuronectes-platessa l; population regulation; Site fidelity; Stable isotopes; stock structure; western-australia
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