Ontogenic changes in the feeding ecology of the early life stages of the Antarctic silverfish (Pleuragramma antarcticum) documented by stable isotopes and diet analysis in the Dumont d'Urville Sea (East Antarctica)

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The feeding ecology of the notothenioid fish Pleuragramma antarcticum was studied in the Dumont d'Urville Sea (East Antarctica) near the French Antarctic station. Stable isotopes (δ13C and δ15N) and diet contents were used in order to study dietary shifts between fish larvae and juveniles. All specimens had low δ13C values (<−24‰), a main characteristic of high-Antarctic pelagic species. Fish larvae showed differences in both carbon and nitrogen ratios when compared with juveniles. Muscle δ15N values showed a difference of one trophic level ( 3‰) between larvae (6.7‰) and juveniles (9.7–10.0‰) and a trophic position of tertiary consumers. Diet content analyses (stereomicroscope and scanning electron microscopes) indicated that larvae are omnivorous, feeding on phytoplankton (mainly diatoms) as well as on zooplankton species. A positive relationship between δ15N values and size was found and indicated a carnivorous diet for older specimens.