MEPS 418:235-248 (2010)  -  DOI: https://doi.org/10.3354/meps08826

ABSTRACT: We used stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis to investigate the trophic ecology of 8 small cetacean species of the southwestern South Atlantic Ocean: 6 delphinids (Grampus griseus, Lagenorhynchus cruciger, L. australis, Lissodelphis peronii, Pseudorca crassidens, and Cephalorhynchus commersonii) and 2 phocoenids (Phocoena dioptrica and P. spinipinnis). We also analyzed samples of possible prey collected from oceanic and coastal habitats adjacent to Tierra del Fuego. Cetacean bone-collagen δ¹³C and δ¹⁵N data revealed information on both habitat and prey preferences. We observed an isotopic continuum in which coastal species had the highest values of δ¹³C and δ¹⁵N (L. australis), while oceanic and southern species had the lowest values (L. cruciger and P. dioptrica), indicative of offshore foraging in cold oceanic waters near the Antarctic Convergence. Overlap in mean isotope values between C. commersonii and P. spinipinnis suggests that these species may have similar habitat and/or prey preferences. Isotope results for L. peronii, P. crassidens, and G. griseus suggest that at these latitudes (~54°S) they forage on the outer continental shelf. G. griseus show bimodal isotopic patterns, suggesting that 2 ecotypes that forage in different habitats and/or consume different prey items occur in this region of the southwestern Atlantic Ocean. The isotopic data presented here provide insight into the ecology of these cetaceans, with relevant implications for their successful management and conservation.

KEY WORDS: Stable isotopes · δ¹³C · δ¹⁵N · Small cetaceans · Foraging areas · Food/prey · South Atlantic Ocean · Southern Ocean