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ESR 31:47-60 (2016)  -  DOI:

Risks of dam construction for South American river dolphins: a case study of the Tapajós River

Heloise J. Pavanato1,*, Gabriel Melo-Santos2, Danielle S. Lima1,3, Marcela Portocarrero-Aya4, Mariana Paschoalini1,5, Federico Mosquera6, Fernando Trujillo6, Rafael Meneses1,7, Miriam Marmontel1, Cláudio Maretti8,9

1Research Group on Amazonian Aquatic Mammals, Mamirauá Institute for Sustainable Development, 2584 Estr. do Bexiga, 69553-225, Tefé, AM, Brazil
2Biology and Conservation of Amazon Aquatic Mammals, Federal University of Pará, Graduate Program of Theory and Research of Behavior, 01 Augusto Correa, 66075-110, Guamá, PA, Brazil
3Laboratory of Mastozoology, Institute of Scientific and Technological Research of the State of Amapá, Rod. Juscelino Kubitschek km. 10, 68901-025, Macapá, AP, Brazil
4Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, 15-09 Callle 28A, Bogota DC, Colombia
5Laboratory of Behavioral Ecology and Bioacoustics, Federal University of Juiz de Fora, José Lourenço Kelmer, 36036-330, Juiz de Fora, MG, Brazil
6Omacha Foundation, 23-28 Calle 86A, Bogota DC, Colombia
7Biodiversity Department, State University of Maranhão, Cidade Universitária Paulo VI, 66055-970, São Luís, Maranhão, Brazil
8WWF Living Amazon Initiative, Edificio Jade Office SGCV Lote 15, S/N, Zona Industrial Guará, 71215-650 Brazil, Brasília DC, Brazil
9Present address: Diretoria de Ações Socioambientais e Consolidação Territorial em Unidades de Conservação/Brazilian Ministry of Environment, EQSW 103/104 Bloco C, Complexo Administrativo Setor Sudoeste, 700670-350, Brasília DC, Brazil
*Corresponding author:

ABSTRACT: River dolphins are strongly affected by the construction of hydroelectric dams. Potential isolation in subpopulations above and below such dams and the resulting low genetic variability of these subpopulations can cause extinction at a local level. Here we aimed to estimate density and population size of South American river dolphins (boto Inia geoffrensis and tucuxi Sotalia fluviatilis), map their distribution, and estimate potential biological removal (PBR) limits in order to evaluate the effects of population fragmentation between planned dams in the Tapajós River, Amazonian basin, Brazil. Boat-based surveys were conducted following a line transect sampling protocol covering different dolphin habitats in 2 stretches of the river divided by rapids. The mark-recapture distance sampling method was applied to account for animals missed on the trackline. After the estimation of population sizes by habitat, PBR was calculated. The farthest upriver sighting of tucuxis was close to the São Luiz do Tapajós rapids, whereas the farthest upriver sighting of botos was upstream of the rapids, suggesting that botos move upstream through the rapids. Estimated abundance of tucuxis (3372 ind., CV = 0.38) was twice as high as that estimated for botos (1815 ind., CV = 0.4). The PBR ranged from 11 to 18 ind. for boto and 21 to 34 for tucuxi. Throughout this study, we identified low abundances of river dolphins compared to other Amazon rivers. Boto may not be sustainable at a population level, due primarily to population fragmentation which would result from the construction of the proposed dams. Precautionary measures are urgently needed before construction of dams begins in the Tapajós River.

KEY WORDS: Cetacean abundance · Distance sampling · Inia geoffrensis · Sotalia fluviatilis · Extinction · IUCN Red List Category · Marine mammal · Population modeling

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Cite this article as: Pavanato HJ, Melo-Santos G, Lima DS, Portocarrero-Aya M and others (2016) Risks of dam construction for South American river dolphins: a case study of the Tapajós River. Endang Species Res 31:47-60.

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