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Auteur Mellon-Duval, C.; Harmelin-Vivien, M.; Metral, L.; Loizeau, V.; Mortreux, S.; Roos, D.; Fromentin, J.-M.
Titre Trophic ecology of the European hake in the Gulf of Lions, northwestern Mediterranean Sea Type Article scientifique
Année 2017 Publication Revue Abrégée Sci. Mar.
Volume 81 Numéro 1 Pages 7-18
Mots-Clés age; bay; biscay; celtic sea; diet; foodweb; glm; habitat; Merluccius merluccius; merluccius-merluccius l.; predator-prey relationships; Size; small pelagic fish; spatiotemporal variation; stable-isotope ratios; Stable isotopes; Stomach contents
Résumé The European hake, Merluccius merluccius, is an important resource for Mediterranean fisheries. This study focuses on juvenile and adult hake feeding ecology in the Gulf of Lions, using information from scientific surveys carried out during two seasons and three years (2004- 2006). Stomach content and stable isotope (delta N-15, delta C-13) analyses were performed, and the main factors explaining variations in delta N-15 were investigated using GLMs. In the Gulf of Lions, hake mostly fed on crustaceans and fish and a dominant piscivorous regime was reached at 15 cm total length. Pelagic fish (sardine, anchovy and small blue whiting) were the main source of prey (40%- 80%) and cannibalism was low (< 5%). The results confirmed that hake is an opportunistic feeder and also showed that the size and diversity of prey vary among hake size classes, probably as a result of the different spatial distribution and/or foraging migrations. The present study finally postulates that the unbalanced sex ratio (80% female against 20% male) observed at the adult stage could be related to the combination of growth pattern differences, diet and exploitation rate on the continental shelf, where the males spend a longer period of time.
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Auteur institutionnel Thèse
Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0214-8358 ISBN Médium
Région Expédition Conférence
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Numéro d'Appel MARBEC @ alain.herve @ collection 2121
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Auteur Moullec, F.; Gascuel, D.; Bentorcha, K.; Guénette, S.; Robert, M.
Titre Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems? Type Article scientifique
Année 2017 Publication Revue Abrégée Journal of Marine Systems
Volume 172 Numéro Pages 104-117
Mots-Clés Bay of Biscay; celtic sea; Ecopath with Ecosim; Ecosystem Approach to Fisheries Management (EAFM); EcoTroph; Trophic indicators
Résumé Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980–2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.
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Auteur institutionnel Thèse
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 0924-7963 ISBN Médium
Région Expédition Conférence
Notes Approuvé pas de
Numéro d'Appel MARBEC @ alain.herve @ collection 2093
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