Cetacea Argentina 13 dolphin 12 Pontoporia blainvillei 8 Atlantic Ocean 6 Atlantic Ocean (South) 6 Tierra del Fuego [(PRV) Argentina] 6 bone 6 carbon isotope 6 endangered species 6 nitrogen isotope 6 stable isotope 6 whale 6 Animals 4 Antarctica 4 Cephalorhynchus commersonii 4 Commerson's dolphin 4 Southern Ocean 4 cetacean 4 female 4 isotopic analysis 4 male 4 mitochondrial DNA 4 population genetics 4 species conservation 4 stomach content 4 tooth 4 trophic level 4 δ13C 4 δ15N 4