Use of carbon and nitrogen stable isotopes to study the feeding ecology of small coastal cetacean populations in southern Brazil

Authors

  • Fernando Augusto Sliva Hardt Universidade da Região de Joinville – UNIVILLE, Departamento de Ciências Biológicas, Laboratório de Nectologia
  • Marta Jussara Cremer Universidade da Região de Joinville – UNIVILLE, Departamento de Ciências Biológicas, Laboratório de Nectologia
  • Antonio José Tonello Junior Universidade da Região de Joinville – UNIVILLE, Departamento de Ciências Biológicas, Laboratório de Nectologia
  • Antonio Bellante Istituto per l'Ambiente Marino Costiero, Via del Faro, Consiglio Nazionale delle Ricerche
  • Gaspare Buffa Istituto per l'Ambiente Marino Costiero, Via del Faro, Consiglio Nazionale delle Ricerche
  • Giuseppa Buscaino Istituto per l'Ambiente Marino Costiero, Via del Faro, Consiglio Nazionale delle Ricerche
  • Salvatore Mazzola Istituto per l'Ambiente Marino Costiero, Via del Faro, Consiglio Nazionale delle Ricerche
  • André Silva Barreto Universidade do Vale do Itajaí – UNIVALI, Centro de Ciências Tecnológicas da Terra e do Mar, Laboratório de Oceanografia Biológica
  • Luiz Antonio Martinelli Centro de Energia Nuclear na Agricultura, Laboratório de Ecologia Isotópica
  • Giovanni Maria Zuppi Istituto di Geologia Ambientale e Geoingegneria, Consiglio Nazionale delle Ricerche

Keywords:

Pontoporia blainvillei, Sotalia guianensis, Babitonga Bay, feeding ecology, trophic level

Abstract

Samples from individuals of the populations of Sotalia guianensis (Guiana) and Pontoporia blainvillei (Franciscana) dolphins living in the Babitonga Bay estuary (26° 28′ S/48° 50′ W), and samples from individuals of a second population of P. blainvillei from a nearshore area (26° 38′ S/48° 41′ W), were collected and analyzed along with their prey between 2000 and 2006, to determine the carbon and nitrogen stable isotope ratios and to verify differences in their feeding ecology. No differences were found in the median ð15N values of Guiana (15.2‰) and Franciscana (15.9‰) dolphins living in Babitonga Bay, nor of nearshore Franciscana (15.0‰) individuals, suggesting no variation in the trophic level of these populations. However, the lack of more information on the isotopic compositions of their putative prey in the nearshore areas prevents the ability to draw definitive conclusions on this issue. The estuarine Franciscana and Guiana dolphin populations presented mean ð13C values of approximately −15.7‰, which were not statistically different from nearshore Franciscana individuals (−14.8‰). Based on stomach content analyses of these species from a previous study, it was reported that there was little overlap in the diet of estuarine Franciscanas and Guiana dolphins. However, based on the similarity of the ð13C values between these two species and of their putative prey, it appears that in fact there is an overlap in the diet of these two species. Based solely on stable isotope analysis, it was not possible to differentiate between estuarine and nearshore Franciscana populations, making it difficult to conclude whether captured nearshore specimens were indeed yearlong residents of these areas. Finally, this study suggests that Franciscana and Guiana dolphin populations are sharing the same resources, mostly L. brevis, D. rhombeus, and S. rastrifer. Therefore, the combination of resource sharing and commercial exploitation of their prey makes these two cetacean species vulnerable.

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Published

2013-12-01

How to Cite

Hardt, F. A. S., Cremer, M. J., Tonello Junior, A. J., Bellante, A., Buffa, G., Buscaino, G., Mazzola, S., Barreto, A. S., Martinelli, L. A., & Zuppi, G. M. (2013). Use of carbon and nitrogen stable isotopes to study the feeding ecology of small coastal cetacean populations in southern Brazil. Biota Neotropica, 13(4). Retrieved from //www.biotaneotropica.org.br/BN/article/view/1228

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