To investigate the foraging habitats of delphinids in southeastern Brazil, we analyzed stable carbon (d13C) and nitrogen (d15N) isotopes in muscle samples of the following 10 delphinid species: Sotalia guianensis, Stenella frontalis, Tursiops truncatus, Steno bredanensis, Pseudorca crassidens, Delphinus sp., Lagenodelphis hosei, Stenella attenuata, Stenella longirostris and Grampus griseus. We also compared the d13C and d15N values among four populations of S. guianensis. Variation in carbon isotope results from coast to ocean indicated that there was a significant decrease in d13C values from estuarine dolphins to oceanic species. S. guianensis from Guanabara Bay had the highest mean d13C value, while oceanic species showed significantly lower d13C values. The highest d15N values were observed for P. crassidens and T. truncatus, suggesting that these species occupy the highest trophic position among the delphinids studied here. The oceanic species S. attenuata, G. griseus and L. hosei had the lowest d15N values. Stable isotope analysis showed that the three populations of S. guianensis in coastal bays had different d13C values, but similar d15N results. Guiana dolphins from Sepetiba and Ilha Grande bays had different foraging habitat, with specimens from Ilha Grande showing more negative d13C values. This study provides further information on the feeding ecology of delphinids occurring in southeastern Brazil, with evidence of distinctive foraging habitats and the occupation of different ecological niches by these species in the study area. |
