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Analysis of distribution of river dolphins (Inia and Sotalia) in protected and transformed areas in the Amazon and Orinoco basins

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Federico Mosquera-Guerra, Fernando Trujillo, Danni Parks, Marcelo Oliveira-da- Costa, Miriam Marmontel, Dolors Armenteras-Pascual, Saulo Usma, Daphne Willems, Juan David Carvajal-Castro, Hugo Mantilla-Meluk, Nicole Franco, Diego Amorocho, R

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International Whaling Commission


Roberto Maldonado, Karina Berg, Lila Sainz, Paul A. Van Damme, Elizabeth Cambell. (author list continued)
The South American river dolphins have evolved in the continental aquatic ecosystems of the Amazon, Grande, Iténez - Mamoré, Araguaia - Tocantis and Orinoco rivers. The spatial and temporal distribution and the habitat use of these cetaceans do in these systems, are determined by distinct environmental characteristics such as precipitation regimes, elevation, productivity and biomass specific to each system. In addition, geomorphological accidents, such as rapids, have emerged as barriers that separate dolphin populations, potentially promoting processes of speciation. To date, there is no comprehensive analysis of river dolphins distribution and representativeness in protected areas or areas transformed by hydroelectric plants. In the present work, through niche and spatial modeling tools, we research the representativeness of both protected areas and areas transformed by hydroelectric plants in the Amazon and Orinoco basins in the distribution of river dolphins (Inia and Sotalia). The models presented here were constructed using the MaxEnt algorithm through the integration of 35,594 georeferenced records and 19 environmental variables derived from the Bioclim and Hydroshed database, which were parameterised in the R programme. A good representation of the distribution of river dolphins within the protected areas was evidenced, although the limited management
of the aquatic ecosystems inside the protected areas does not guarantee the conservation of these species. A major threat identified for river dolphins in South America is the loss of habitat and fragmentation as a result of the construction of hydroelectric dams. We examined the degree of overlap between the distribution of Inia and Sotalia and
hydroelectric projects in construction, operation and planning phases and provided an initial quantification of this tensor. Finally, we consider that the cumulative impacts
(fragmentation, regulation of the flood pulse, retention of limiting nutrients and alteration in the levels of productivity) generated by this type of infrastructure at the macrobasin scale will exacerbate the level of the threats to the conservation of river dolphins and their habitats in the Amazon and Orinoco basins.

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