ABSTRACT: The Amazonian manatee Trichechus inunguis has been categorized as Vulnerable by the IUCN. There have been few studies on the species 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 (Tambococha-Jatuncocha and the Lagarto River), in the provinces of Sucumbíos and Orellana. We surveyed Amazonian manatees along rivers and in lagoons, using 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^-1 and estimated a population density of 1.09 and 0.94 ind. km^-2 in Tambococha-Jatuncocha and the Lagarto River, respectively. In addition, occupancy rates varied between 0.51 and 0.57, and presence and distribution of the species were associated with distance to humans. The Amazonian manatee population estimates presented here represent a baseline for future research, and additional surveys will be needed to understand population fluctuations over time. An evaluation of population viability in Tambococha-Jatuncocha and the Lagarto River would also be required to determine whether these populations will be able to persist over the long term under different deterministic and stochastic scenarios.

中文翻译：

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厄瓜多尔东部亚马孙海牛的占有率和人口密度估计

摘要：亚马逊海牛Trichechus inunguisIUCN已将其归类为“易受伤害”。由于其难以捉摸的性质以及其水生生境的可见性低，因此在其自然生境中对该物种的研究很少。了解亚马逊海牛的保护状况，以及其人口趋势和直接威胁的任何变化，是其管理和保护的基础。我们的研究是在Sucumbíos和Orellana省的两个厄瓜多尔亚马逊地区（Tambococha-Jatuncocha和Lagarto河）进行的。我们使用探鱼器侧面扫描声纳来提高可检测率，从而对沿河和泻湖的亚马逊海牛进行了调查。我们估计了接触率，人口密度和入住率。通过573 km的采样努力，我们获得了0.90记录的平均遭遇率10 km ^-1并估计人口密度为1.09和0.94 ind。km ^-2分别位于Tambococha-Jatuncocha和Lagarto河。此外，占用率在0.51和0.57之间变化，并且物种的存在和分布与到人类的距离有关。此处显示的亚马逊海牛种群估计数是未来研究的基准，并且需要进行其他调查才能了解人口随时间的波动。还需要对Tambococha-Jatuncocha和Lagarto河中的种群生存能力进行评估，以确定这些种群是否能够在不同的确定性和随机性情况下长期持久。