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Auteur Marsac, F.; Annasawmy, P.; Noyon, M.; Demarcq, H.; Soria, M.; Rabearisoa, N.; Bach, P.; Cherel, Y.; Grelet, J.; Romanov, E.
Titre Seamount effect on circulation and distribution of ocean taxa in the vicinity of La Perouse, a shallow seamount in the southwestern Indian Ocean Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages 104806
Mots-Clés acoustics; Bathymetry; behavior; chlorophyll; diet; humpback whales; l-adcp; Mesoscale eddies; Mesozooplankton; micronekton; Micronekton; migration; Pelagic longline fisheries; Stomach contents; swordfish xiphias-gladius; tuna; zooplankton
Résumé The La Perouse seamount (60 m depth) has so far been poorly studied despite it being a short distance (160 km) from Reunion Island. As part of the MADRidge project, a multidisciplinary cruise was conducted to evaluate the effect of this shallow seamount on the local hydrology and ecology. Current measurements, temperature and chlorophyll-a profiles, and mesozooplankton and micronekton samples were collected between the summit and 35 km away. Micronekton data were supplemented with stomach content of pelagic top predators as well as fisheries statistics from the domestic longline fleet operating from Reunion. Vertical current profiles revealed distinct patterns between the offshore and seamount-flanked stations, giving evidence of topographical induced flow instabilities, notably on its leeward side (west) relative to the east flank. Distinct patterns in temperature and chlorophyll-a vertical profiles suggest the formation of convergent and divergent circulation cells as a result of the irregular and crescent-like summit topography. Spatial differences in zooplankton abundance were detected with higher biovolumes on the leeward flank. The overall acoustic backscatter for micronekton over the summit was weaker than offshore, but highly concentrated in the upper layer. Albacore tuna and swordfish dominate the longline catch west of Reunion, seemingly in association with a deep (900 m) topographic feature. Yet the largest catch is not directly associated with La Perouse which would be too shallow for top predators to aggregate around in the long term. Enhanced levels of phytoplankton or zooplankton enrichment at La Perouse were not demonstrated in this study, nor was there notable diversity of micronekton species. This might explain the relatively limited importance of this seamount to the tuna fisheries in this region.
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Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
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ISSN 0967-0645 ISBN Médium
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Notes WOS:000556810400009 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2850
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