Get access

Assessing population parameters and trends of Guiana dolphins (Sotalia guianensis): An eight-year mark-recapture study

Authors

  • Mauricio Cantor,

    1. Laboratório de Mamíferos Aquáticos,
      Departamento de Ecologia e Zoologia,
      Centro Ciências Biológicas,
      Universidade Federal de Santa Catarina,
      P. O. Box 5102, CEP 88040-970,
      Florianópolis, Santa Catarina, Brazil
      and
      Instituto Baleia Jubarte,
      Rua Barão do Rio Branco, 26,
      CEP 45900-000, Caravelas, Bahia, Brazil
      E-mail: m.cantor@ymail.com
    Search for more papers by this author
  • Leonardo L. Wedekin,

    1. Instituto Baleia Jubarte,
      Rua Barão do Rio Branco, 26,
      CEP 45900-000, Caravelas, Bahia, Brazil
    Search for more papers by this author
  • Fábio G. Daura-Jorge,

    1. Laboratório de Mamíferos Aquáticos,
      Departamento de Ecologia e Zoologia,
      Centro Ciências Biológicas,
      Universidade Federal de Santa Catarina,
      P. O. Box 5102, CEP 88040-970,
      Florianópolis, Santa Catarina, Brazil
    Search for more papers by this author
  • Marcos R. Rossi-Santos,

    1. Instituto Baleia Jubarte,
      Rua Barão do Rio Branco, 26,
      CEP 45900-000, Caravelas, Bahia, Brazil
    Search for more papers by this author
  • Paulo C. Simões-Lopes

    1. Laboratório de Mamíferos Aquáticos,
      Departamento de Ecologia e Zoologia,
      Centro Ciências Biológicas,
      Universidade Federal de Santa Catarina,
      P. O. Box 5102, CEP 88040-970,
      Florianópolis, Santa Catarina, Brazil
    Search for more papers by this author

Abstract

This study represents the first attempt to study the population dynamics of Guiana dolphins (Sotalia guianensis), by evaluating a set of demographic parameters. The population of the Caravelas River estuary, eastern Brazil, was systematically monitored through a long-term mark-recapture experiment (2002–2009). Abundance estimates revealed a small population (57–124 dolphins), comprised of resident dolphins and individuals that temporarily leave or pass through the study area. Temporary emigration from the estuary to adjacencies (γ″= 0.33 ± 0.07 SE) and return rate (1 −γ′= 0 .67) were moderate and constant, indicating that some dolphins use larger areas. Survival rate (ϕ= 0.88 ± 0.07 SE) and abundance were constant throughout the study period. Power analysis showed that the current monitoring effort has high probability of detecting abrupt population declines (1 −β= 0.9). Although the monitoring is not yet sensitive to subtle population trends, sufficient time to identify them is feasible (additional 3 yr). Despite such apparent stability, this population, as many others, inhabits waters exposed to multiple human-related threats. Open and closed population modeling applied to photo-identification data provide a robust baseline for estimating several demographic parameters and can be applied to other populations to allow further comparisons. Such synergistic efforts will allow a reliable definition of conservation status of this species.

Ancillary