Stable isotopes reveal the trophic position and mesopelagic fish diet of female southern elephant seals breeding on the Kerguelen Islands

Type Article
Date 2008-10
Language English
Author(s) Cherel Y1, Ducatez S1, Fontaine C1, Richard Patrice2, Guinet C1
Affiliation(s) 1 : CNRS, Ctr Etud Biol Chize, UPR 1934, F-79360 Villiers En Bois, France.
2 : CNRS IFREMER ULR, Ctr Rech Ecosyst Littoraux Anthropises, UMR 6217, F-17137 Lhoumeau, France.
Source Marine Ecology Progress Series (0171-8630) (Inter-Research), 2008-10 , Vol. 370 , P. 239-247
DOI 10.3354/meps07673
WOS© Times Cited 123
Keyword(s) Squid, Southern Ocean, Pelagic ecosystem, Myctophid, Mesopelagic fish, Cephalopod
Abstract Trophic interactions between organisms are the main drivers of ecosystem dynamics, but scant dietary information is available for wide-ranging predators during migration. We investigated feeding habits of a key consumer of the Southern Ocean, the southern elephant seal Miroungia leonina, by comparing its blood delta(13) C and delta N-15 values with those of various marine organisms, including crustaceans, squid, fishes, seabirds and fur seals. At the end of winter, delta C-13 values (-23.1 to -20.1 parts per thousand)indicate that female elephant seals forage mainly in the vicinity of the Polar Front and in the Polar Frontal Zone. Trophic levels derived from delta N-15 values (trophic level = 4.6) show that the southern elephant seal is a top consumer in the pelagic ecosystem that is dominated by colossal squid. The mean delta N-15 value of seals (10.1 +/- 0.3 parts per thousand) indicates that they are not crustacean eaters, but instead feed on crustacean-eating prey. Surprisingly, most of the previously identified prey species have isotope delta C-13 and delta N-15 values that do not fit with those of potential food items. The most singular pattern to emerge from delta N-15 values of predators and prey is that female seals are likely to feed on myctophid fishes, not squid or Patagonian toothfish. We therefore suggest that they Occupy a unique trophic niche amongst the guild of air-breathing, diving vertebrates by feeding on mesopelagic fish at great depths. In turn, this finding emphasizes the role of myctophids in oceanic waters and will help to quantify and model fluxes of matter and energy within the pelagic ecosystem of the Southern Ocean.
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Cherel Y, Ducatez S, Fontaine C, Richard Patrice, Guinet C (2008). Stable isotopes reveal the trophic position and mesopelagic fish diet of female southern elephant seals breeding on the Kerguelen Islands. Marine Ecology Progress Series, 370, 239-247. Publisher's official version : https://doi.org/10.3354/meps07673 , Open Access version : https://archimer.ifremer.fr/doc/00000/5021/