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Marine Ecology Progress Series

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MEPS 531:1-14 (2015)  -  DOI:

The role of sardine as prey for pelagic predators in the western Mediterranean Sea assessed using stable isotopes and fatty acids

Luis Cardona1,*, Laura Martínez-Iñigo1, Rafael Mateo2, Jacob González-Solís1

1Biodiversity Research Institute (IRBio) and Department of Animal Biology, Faculty of Biology, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain
2Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM, Ronda de Toledo s/n, 13071 Ciudad Real, Spain
*Corresponding author:

ABSTRACT: This study combined the analysis of fatty acids and stable isotopes of nitrogen and carbon to test the hypothesis that the pelagic food web of the south Catalan Sea has a wasp-waist structure supported by sardines Sardina pilchardus. If this hypothesis were correct, most predators would be expected to have stable isotope ratios and fatty acid profiles consistent with those derived from a sardine-based diet. However, this was true only for mackerel Scomber scomber, blue butterfish Stromateus fiatola, all seabirds and oceanic loggerhead turtles Caretta caretta. The values of the DHA/EPA index of neritic loggerhead turtles and striped dolphins Stenella caeruleoalba were also consistent with a sardine/squid diet, but their trophic positions were too high. On the other hand, the DHA/EPA index of most predatory fishes indicated that anchovies Engraulis encrasicolus and/or horse mackerel Trachurus trachurus were their main prey. Nevertheless, some amounts of low trophic level invertebrates were likely to be consumed by some predatory fishes, because their trophic positions where lower than expected from a fish-based diet only. The heterogeneous distribution of phytoplankton groups above and below the thermocline during the warm season is hypothesized to be the primary reason for this food web structure, although the strong reliance of some seabirds on sardines is the likely consequence of a massive consumption of discards from fishing boats. In short, there is little evidence for a wasp-waist structure based on sardine, which may explain why the populations of predators fluctuate less than the population of sardines.

KEY WORDS: Anchovy · Engraulis encrasicolus · Fatty acids · Food web · Sardina pilchardus · Sardine · Stable isotope · Top predator

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Cite this article as: Cardona L, Martínez-Iñigo L, Mateo R, González-Solís J (2015) The role of sardine as prey for pelagic predators in the western Mediterranean Sea assessed using stable isotopes and fatty acids. Mar Ecol Prog Ser 531:1-14.

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