We estimated density and abundance of the threatened southwest Alaska distinct population segment of northern sea otters (Enhydra lutris kenyoni) in two management units. We conducted aerial surveys in Bristol Bay and South Alaska Peninsula management units in 2016, and modeled sea otter density and abundance with Bayesian hierarchical distance sampling models and spatial environmental covariates (depth, distance to shore, depth × distance to shore). Spatial environmental covariates substantially impacted sea otter group density in both management units, but effects sizes differed between the two management units. Abundance (9,733 otters, 95% CrI 6,412–17,819) and density (0.82 otters/km², 95% CrI 0.54–1.49) estimates for Bristol Bay indicated a moderate population size. In contrast, abundance (546 otters, 95% CrI 322–879) and density (0.06 otters/km², 95% CrI 0.03–0.09) estimates indicated a relatively low population size in South Alaska Peninsula. Overall, our results highlight the importance of accounting for the detection process in monitoring at-risk species to reduce the uncertainty associated with making conclusions about population declines.

中文翻译：

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评估受威胁海洋哺乳动物种群的现状：估计阿拉斯加西南部北部海獭（Enhydra lutris kenyoni）的数量

我们估计了两个管理单位中受威胁的阿拉斯加西南部独特种群北部海獭 ( Enhydra lutris kenyoni ) 的密度和丰度。我们于 2016 年在布里斯托尔湾和南阿拉斯加半岛管理单位进行了航测，并使用贝叶斯分层距离采样模型和空间环境协变量（深度、到岸的距离、深度 × 到岸的距离）模拟了海獭的密度和丰度。空间环境协变量对两个管理单位的海獭种群密度产生了重大影响，但两个管理单位之间的影响大小不同。丰度（9,733 只水獭，95% CrI 6,412–17,819）和密度（0.82 只水獭/km ², 95% CrI 0.54–1.49) 对布里斯托尔湾的估计表明人口规模适中。相比之下，丰度（546 只水獭，95% CrI 322-879）和密度（0.06 只水獭/km ²，95% CrI 0.03-0.09）估计表明南阿拉斯加半岛的种群规模相对较低。总体而言，我们的结果强调了在监测高危物种时考虑检测过程的重要性，以减少与得出人口下降结论相关的不确定性。