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ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01094

Occupancy and population density estimates of the Amazonian manatee in eastern Ecuador

Viviana Narváez Ruano, Victor Utreras B. , Galo Zapata-Ríos*

*Corresponding author:

ABSTRACT: The Amazonian manatee Trichechus inunguis has been categorized as Vulnerable (VU) by the International Union for Conservation of Nature. There have been few studies on the Amazonian manatee in its natural habitats due to its elusive nature, and the low visibility of its aquatic habitats. Understanding the conservation status of Amazonian manatees, as well as any changes in their population trends and direct threats, is the basis for their management and conservation. Our study was carried out in 2 localities of the Ecuadorian Amazon (Jatuncocha-Tambococha and the Lagarto River), in the provinces of Sucumbíos and Orellana. We surveyed Amazonian manatees along rivers and in lagoons, using a fish finder side-scan sonar to increase detectability rates. We estimated encounter rates, population density and occupancy. With a sampling effort of 573 km, we obtained an average encounter rate of 0.90 records/10 km, and estimated a population density of 1.09 and 0.94 individuals/km2 in Jatuncocha-Tambococha and Lagarto River, respectively. In addition, occupancy rates varied between 0.51 and 0.57, and presence and distribution of the species were a factor of distance to humans. The Amazonian manatee population estimates presented here represent a baseline for future research. Additional surveys will be needed to understand population fluctuations over time. Also, an evaluation of population viability in Tambococha-Jatuncocha and the Lagarto River would be required to determine whether these populations will be able to persist over the long-term under different deterministic and stochastic scenarios.