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Navarro, J., Saez-Liante, R., Albo-Puigserver, M., Coll, M., & Palomera, I. (2017). Feeding strategies and ecological roles of three predatory pelagic fish in the western Mediterranean Sea. Deep-Sea Res. Part II-Top. Stud. Oceanogr., 140, 9–17.
Résumé: Knowing the feeding ecology of marine predators is pivotal to developing an understanding of their ecological role in the ecosystem and determining the trophic relationships between them. Despite the ecological importance of predatory pelagic fish species, research on these species in the Mediterranean Sea is limited. Here, by combining analyses of stomach contents and stable isotope values, we examined the feeding strategies of swordfish, Xiphias gladius, little tunny, Euthynnus alletteratus and Atlantic bonito, Sarda sarda, in the western Mediterranean Sea. We also compared the trophic niche and trophic level of these species with published information of other sympatric pelagic predators present in the ecosystem. Results indicated that, although the diet of the three species was composed mainly by fin-fish species, a clear segregation in their main feeding strategies was found. Swordfish showed a generalist diet including demersal species such as blue whiting, Micromesistius poutassou, and European hake, Merluccius merluccius, and pelagic fin-fish such as barracudina species (Arctozenus risso and Lestidiops jayakari) or small pelagic fish species. Little tunny and Atlantic bonito were segregated isotopically between them and showed a diet basically composed of anchovy, Engraulis encrasicolus, and round sardinella, Sardinella aurita, and sardines, Sardina pilchardus, respectively. This trophic segregation, in addition to potential segregation by depth, is likely a mechanism that allows their potential coexistence within the same pelagic habitat. When the trophic position of these three predatory pelagic fish species is compared with other pelagic predators such as bluefin tuna, Thunnus thynnus, and dolphinfish, Coryphaena hippurus, present in the western Mediterranean Sea, we found that they show similar intermediate trophic position in the ecosystem. In conclusion, the combined stomach and isotopic results highlight, especially for little tunny and Atlantic bonito, the trophic importance of Clupeoid species in their diet. In addition, the importance of demersal resources for swordfish provides evidence for the pelagic-demersal coupling of the ecosystem and the need to manage marine resources in an integrated way. (C) 2016 Elsevier Ltd. All rights reserved.
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Ouisse, V., Riera, P., Migne, A., Leroux, C., & Davoult, D. (2012). Food web analysis in intertidal Zostera marina and Zostera noltii communities in winter and summer. Marine Biology, 159(1), 165–175.
Résumé: The food web of two intertidal seagrass (Zostera marina and Zostera noltii) beds that may be influenced by the seasonal variation in food source abundance was studied in winter and in summer with delta(13)C and delta(13)N analysis. In spite of high relative variation of abundance of main primary producers at the two sites, the food web did not vary between winter and summer. The delta(13)C range of primary producers was wide. Zostera leaves, the most (13)C-enriched source, were not consumed directly by grazers. Deposit and filter feeders have a similar delta(13)C and could use a mix of suspended and sedimented organic particulate matter, largely composed of detritus from macroalgae to seagrass. This trophic pathway allows the local incorporation of the high biomass produced by seagrasses. The wide delta(15)N range of predators was linked either to a large variety from omnivore to carnivore predators or to the also wide ranges of delta(15)N of primary consumers.
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