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

2011; Wiley; Volume: 28; Issue: 1 Linguagem: Inglês

10.1111/j.1748-7692.2010.00456.x

1748-7692

Maurício Cantor, Leonardo Liberali Wedekin, Fábio G. Daura‐Jorge, Marcos R. Rossi‐Santos, Paulo C. Simões‐Lopes,

Avian ecology and behavior

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.