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Auteur |
Soares, A.; Lira, A.S.; Gonzalez, J.G.; Eduardo Nole, L.; Lucena-Fredou, F.; Le Loc'h, F.; Ferreira, B.P.; Fredou, T. |
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Titre |
Feeding habits and population aspects of the spotted goatfish, Pseudupeneus maculatus (Perciformes: Mullidae), on the continental shelf of northeast Brazil |
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Article scientifique |
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Année  |
2020 |
Publication |
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Revue Abrégée |
Sci. Mar. |
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Volume |
84 |
Numéro |
2 |
Pages |
119-131 |
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Mots-Clés |
biodiversity; biology; Brazil; coast; cross-shelf; diet composition; distribution patterns; dynamics; ecology; island; reef fishes; stable isotopes; stomach content analysis; strategy; teleostei |
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Résumé |
This study provides information about the feeding habits, population aspects and spatial distribution of the spotted goatfish, Pseudupeneus maculatus, along the coast of the tropical Brazilian continental shelf. Distribution patterns are described using length frequencies and catch rates. Stable isotope ratios of carbon (delta C-13) and nitrogen (delta N-15), along with stomach contents, were analysed to determine the diet of the spotted goatfish. Multivariate analysis and numerical indicators of the diet, such as numerical frequency. frequency of occurrence and weight percentage, were computed to evaluate the diet composition. The mean trophic position was defined using both stable isotope ratios and stomach content analysis. The length at first maturity for the species was determined as 13.7 cm. A slight pattern in size distribution was observed, with mean size increasing with depth along the shelf. The diet was mainly composed of crustaceans, teleosts and Polychaeta. No clear dietary difference was found between habitat types, water depth or latitude. Both trophic positions estimated by stable isotopes and stomach contents analysis ranged between levels 3 and 4. P. maculatus was found to be feeding on many rare and infrequent prey items, classifying it as a generalist zoobenthivorous predator, probably due to its efficient search strategy. |
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English |
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0214-8358 |
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WOS:000539067100006 |
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pas de |
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MARBEC @ isabelle.vidal-ayouba @ |
collection |
2825 |
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Auteur |
Annasawmy, P.; Cherel, Y.; Romanov, E.; Le Loc'h, F.; Menard, F.; Ternon, J.-F.; Marsac, F. |
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Titre |
Stable isotope patterns of mesopelagic communities over two shallow seamounts of the south-western Indian Ocean |
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Article scientifique |
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Année |
2020 |
Publication |
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Revue Abrégée |
Deep-Sea Res. Part II-Top. Stud. Oceanogr. |
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Volume |
176 |
Numéro |
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Pages |
104804 |
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Mots-Clés |
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 |
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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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English |
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ISSN |
0967-0645 |
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Notes |
WOS:000556810400002 |
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pas de |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
2835 |
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Auteur |
Demarcq, H.; Noyon, M.; Roberts, M.J. |
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Titre |
Satellite observations of phytoplankton enrichments around seamounts in the South West Indian Ocean with a special focus on the Walters Shoal |
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Article scientifique |
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Année |
2020 |
Publication |
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Revue Abrégée |
Deep-Sea Res. Part II-Top. Stud. Oceanogr. |
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Volume |
176 |
Numéro |
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Pages |
104800 |
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Mots-Clés |
chlorophyll; Chlorophyll-a; currents; Deep chlorophyll maximum; ecology; flow; Geostrophic currents; model; MODIS-Aqua; Remote sensing; swig; zooplankton |
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Résumé |
Spatial anomalies associated with seamounts and islands have been detected in the South West Indian Ocean using a new surface chlorophyll-a based enrichment index (EI). Calculated from daily L3 4-km MODIS chl-a data from 2003 to 2018, the EI was used to quantify recurrent (seasonal) surface enrichment associated with these features. Most notable were the shallow Walters Shoal (18 m) and nearby deeper WS-2 seamount (480 m), both located on the southern Madagascar Ridge, which showed high EI values of 40% and 15% local enhancement. Tmmelin Island, east of Madagascar, exhibited more moderate values of 15% local increase. Other shallower seamounts including La Perouse (60 m) and MAD-Ridge (240 m) exhibited sporadic or no measurable surface maxima. Regions of strong mesoscale activity such as south of Madagascar where the South East Madagascar Current detaches from the continent also revealed high EI values. A marked seasonality of the EI was observed over the Walters Shoal, with higher values during the oligotrophic season than in the austral winter. The seasonal variability of the MLD in combination with the seamount bathymetry appears to induce the thermal and biological anomalies observed there, possibly favoured by the presence of a Taylor cap at the summit. Ship-collected in situ measurements showed the satellite observed enrichment to be associated with shallowing of the deep chlorophyll maximum, as well as a shift of phytoplankton groups towards diatoms and small flagellates. No net increase of integrated chl-a was measured but a potential doubling in primary productivity is expected. The EI developed in this study, designed to reveal sporadic, small localised chl-a maxima, is likely applicable to other areas in the ocean where there is local enrichments. |
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English |
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ISSN |
0967-0645 |
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Notes |
WOS:000556810400010 |
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pas de |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
2841 |
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Auteur |
Mourier, J.; Claudet, J.; Planes, S. |
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Titre |
Human-induced shifts in habitat use and behaviour of a marine predator: the effects of bait provisioning in the blacktip reef shark |
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Article scientifique |
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Année |
2020 |
Publication |
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Revue Abrégée |
Anim. Conserv. |
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Mots-Clés |
carcharhinus-melanopterus; Control-Impact design; coral reef; ecology; ecotourism; habitat use; impacts; life-history; metaanalysis; reserves; sexual segregation; shark; tourism; traits; wildlife; wildlife provisioning; wildlife tourism |
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Résumé |
While the negative effects of consumptive pressures on marine predators are well established, the effects of increasing non-consumptive activities such as wildlife tourism are still understudied. As such, the long-term effects of the provision of bait on shark behaviour are still unclear. Here, we assessed the effects of provisioning using a Control-Impact design on the spatial use and level of residency of the blacktip reef sharkCarcharhinus melanopterusover a 2-year period. We used effect sizes to model the relative changes in residency between provisioning and non-provisioning sites. Sharks showed a high degree of residency and significant changes in their habitat use which persisted overnight while the activity ceased. We suggest that provisioning activities can affect species with high level of residency such as the blacktip reef shark. Further research is needed to better understand how these behavioural modifications can alter the fitness of this species. It is important to adapt shark provisioning activities to limit the induced changes in habitat use. |
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English |
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ISSN |
1367-9430 |
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WOS:000557161200001 |
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pas de |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
2852 |
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Auteur |
Noyon, M.; Rasoloarijao, Z.; Huggett, J.; Ternon, J.-F.; Roberts, M. |
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Titre |
Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean |
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Article scientifique |
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Année |
2020 |
Publication |
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Revue Abrégée |
Deep-Sea Res. Part II-Top. Stud. Oceanogr. |
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Volume |
176 |
Numéro |
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Pages |
104759 |
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Mots-Clés |
biomass size spectrum; chlorophyll-a; cyclonic eddy; eddies; leeuwin current; Mesoscale eddies; Normalised biovolume size spectrum (NBSS); north pacific; Oligotrophic environment; patterns; Pelagic ecology; plankton; temperature; Topography; zooplankton distribution |
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Résumé |
Seamounts are recognised as hotspots of biodiversity, attracting large numbers of top predators, but the underlying mechanisms are still unclear. We studied mesozooplankton abundance and size distribution at three shallow seamounts (60 m, 240 m and 18 m deep) in the South West Indian Ocean, along a latitudinal gradient (19 degrees S, 27 degrees S and 33 degrees S). Samples were analysed using a ZooScan, allowing the use of a size-based approach. Differences were observed between seamount areas, but overall zooplankton communities did not seem to be affected by the changes in topography. Only in the lee of La Perouse seamount was the zooplankton community slightly more concentrated than upstream, suggesting that zooplankton were flushed downstream of the seamount. The southernmost and shallowest seamount, Walters Shoal, had low abundance and its size spectrum differed greatly from the two other seamounts further north. These differences were attributed to seasonality and mesozooplankton population dynamics, whereas the other two seamounts exhibited a more “typical” oligotrophic pelagic ecosystem, at equilibrium and dominated by small organisms. At the time of sampling, the unnamed seamount south of Madagascar was influenced by a mesoscale dipole that impacted the zooplankton distribution, potentially masking any seamount effect. The normalised biomass size spectrum approach contributed to a better understanding of the ecosystem dynamics (i.e. equilibrium vs. non-steady state) but revealed little variability within a stable oligotrophic environment. |
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English |
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ISSN |
0967-0645 |
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Notes |
WOS:000556810400008 |
Approuvé |
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Numéro d'Appel |
MARBEC @ isabelle.vidal-ayouba @ |
collection |
2853 |
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| Lien permanent pour cet enregistrement |
