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Assessing population parameters and trends of Guiana dolphins ( Sotalia guianensis ): An eight‐year mark‐recapture study
Author(s) -
Cantor Mauricio,
Wedekin Leonardo L.,
DauraJorge Fábio G.,
RossiSantos Marcos R.,
SimõesLopes Paulo C.
Publication year - 2012
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2010.00456.x
Subject(s) - mark and recapture , population , abundance (ecology) , estuary , ecology , geography , vital rates , fishery , population size , population growth , population model , population decline , biology , demography , habitat , sociology
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.