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

Cardona, Luis and Martínez-Iñigo, Laura and Mateo, Rafael and González-Solís, Jacob (2015) The role of sardine as prey for pelagic predators in the western Mediterranean Sea assessed using stable isotopes and fatty acids. Marine Ecology Progress Series, 531 . pp. 1-14. ISSN 0171-8630

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

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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 sea-birds and oceanic loggerhead turtles Caretta caretta. The values of the DHA/EPA index of neritic logger-head 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 in- dicated 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.

Keywords:Sardine, Sardina pilchardus, Anchovy, Engraulis encrasicolus, Fatty acids, Food web, Stable isotope, Top predator, JCOpen
Subjects:C Biological Sciences > C180 Ecology
C Biological Sciences > C350 Marine Zoology
C Biological Sciences > C161 Marine Biology
C Biological Sciences > C160 Marine/Freshwater Biology
C Biological Sciences > C100 Biology
F Physical Sciences > F710 Marine Sciences
Divisions:College of Social Science > School of Psychology
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ID Code:17807
Deposited On:06 Jul 2015 15:30

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