Ecología trófica de cetáceos subantárticos utilizando el análisis de isótopos estables

iii TROPHIC ECOLOGY OF SUBANTARCTIC CETACEANS USING STABLE ISOTOPES ANALYSIS ABSTRACT. The appropriate management of the Southwest Atlantic marine ecosystems requires a better understanding of its structure and dynamics. That is why it is of major importance the study of the presence and trophic function of the cetacean species since, given their role as top predator, they exert important effects on marine food webs. The aim of this study is to evaluate the trophic ecology of eight species of toothed whales that inhabit the sub-Antarctic waters of Tierra del Fuego. This study demonstrated the utility of the isotopic variation of bone collagen to The appropriate management of the Southwest Atlantic marine ecosystems requires a better understanding of its structure and dynamics. That is why it is of major importance the study of the presence and trophic function of the cetacean species since, given their role as top predator, they exert important effects on marine food webs. The aim of this study is to evaluate the trophic ecology of eight species of toothed whales that inhabit the sub-Antarctic waters of Tierra del Fuego. This study demonstrated the utility of the isotopic variation of bone collagen to define the main feeding behavior of six species of delphinids (Lagenorhynchus australis, Cephalorhynchus commersonii, Grampus griseus, Lissodelphis peronii, Pseudorca crassidens and Lagenorhynchus cruciger) and two species of phocoenids (Phocoena dioptrica and Phocoena spinipinnis). The stable isotopes analysis on different prey groups (fish, cephalopod mollusk and crustaceans) contributed to the ecological interpretation of the δ13C and δ15N values of the predators analyzed. The combined use of δ13C and δ15N of bone collagen reveals spatial information on a long time scale (~5 to 10yr) on food habits and foraging areas of the cetaceans. It was found a trophic continuum, revealed by these isotopes, from the most coastal species with the highest values (Lagenorhynchus australis) to the most oceanic species spread further south between waters of the Drake Passage and the Polar Front (Phocoena dioptrica and Lagenorhynchus cruciger). The δ13C and δ15N values of these marine consumers are a reflection of the spatial variations in these isotopes values of the primary producers and their prey species at different habitats – coastal, Patagonian shelf, oceanic –. The isotopic evidence suggests that in inshore habitats Lagenrohynchus australis and two other coastal species Cephalorhynchus commersonii /Phocoena spinipinnis occupy different ecological niches. The high isotopic values of Lagenorhynchus australis are consistent with coastal consumers of high trophic levels. The main δ13C and δ15N values and the isotopic variance in Cephalorhynchus commersonii and Phocoena spinipinnis indicate the use of coastal and shelf resources and mainly an ichthyophagous diet. In offshore regions, the similarities found in the isotopic signatures of Grampus griseus,