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Abstract: Very few freshwater ecosystems maintain river dolphin populations. Over the last century, much effort has been invested in assessing threats and impacts to river dolphin species in Asia. As a result, population sizes, distribution, and trends in populations of these species are well known. For many reasons, the situation in South America is quite different, and considerable knowledge gaps remain regarding the species in the region. Nevertheless, the Amazon region sustains the world’s largest population of river dolphins, mostly in Brazil. The Brazilian Amazon encompasses nine states, and many of these territories lack credible information on river dolphin ecology, habitat use, population trends, genetics, and distribution. For instance, the International Union for Conservation of Nature’s geographic range maps for Inia geoffrensis and Sotalia fluviatilis do not acknowledge their occurrence throughout Amapá in the northeastern Amazon. This study adopted a biogeographical rather than a hydrological approach to assess the distribution of river dolphin species in Amapá. The research compiled field data gathered from 2008 to 2020 and produced geographic range/distribution maps for I. geoffrensis and Sotalia spp. in Amapá. A literature review was coupled with field work and interviews with authorities and local researchers to assess distribution, and past and present evidence of anthropogenic disturbance of the species. Critical knowledge gaps were identified, and approaches to improve the protection of the species and their habitats in the region are recommended. We suggest that at least 4,224 and 2,596 km of rivers for I. geoffrensis and Sotalia spp., respectively, should be added to the IUCN’s geographic range maps as well as the exclusion of 1,033 km of water courses erroneously indicated as an occurrence area of I. geoffrensis.
Key Words: distribution, Amazon River dolphin, tucuxi, Guiana dolphin, threats, habitat change, Amapá
Page Numbers: 376-393
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