Human‐caused mortality in general, and unregulated hunting in particular, have been implicated in reductions in brown bear (Ursus arctos) populations throughout much of their range. In northwestern Alaska, USA, bear densities have not been assessed in 20 years while harvest regulations have been liberalized, raising concerns that broad undetected population declines might occur. We used a modified mark‐resight approach to estimate brown bear density during 2005–2018 in 4 subareas throughout the region. We also summarized harvest information for each subarea and used our survey results to estimate harvest rates. We estimated densities for independent bears assuming constant or heterogeneous probabilities of detection and occurrence. We present the results of the constant model for more direct comparison with past work and the heterogeneity model results to provide estimates of density that are less likely to be negatively biased. Using the constant model, we estimated the density of independent bears was 17.0, 49.2, 24.9, and 19.4/1,000 km² on portions of the Seward Peninsula, the lower Noatak River, the upper Noatak River, and Gates of the Arctic National Park and Preserve, respectively. These estimates are broadly similar to those from past work in interior and northwestern Alaska, with the exception of the lower Noatak River subarea where our estimates are the highest reported for a bear population in northern Alaska. We estimated that the harvest rate on the Seward Peninsula was approximately 5.2% or 7.7% on average, depending upon the model used. In the remaining areas, we estimated annual harvest rates were <2.5%, well within sustainability guidelines from past work. Overall, our results suggest that brown bear densities are similar or somewhat higher than in the past in much of northwestern Alaska and that current harvest rates are sustainable in most areas, except perhaps the Seward Peninsula. Ongoing survey work will be useful for further evaluating the assumptions of the modified mark‐resight survey approach, assessing population trajectory, and determining the effect of harvest on brown bear populations. © 2021 The Wildlife Society.

中文翻译：

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阿拉斯加西北部的棕熊密度和估计收成率

一般说来，人为造成的死亡率，特别是无节制的狩猎，与棕熊的减少有关（熊熊（Ursus arctos））人口的大部分范围。在美国阿拉斯加西北部，20年来未对熊的密度进行评估，而放宽了捕捞法规，这引发了人们的担忧，即未发现的人口大范围下降。我们使用了改进的标记检验方法来估计2005-2018年整个区域内4个分区的棕熊密度。我们还总结了每个分区的收获信息，并使用我们的调查结果来估算收获率。我们假设检测和发生的概率恒定或异质，估计独立熊的密度。我们提出了常数模型的结果，以便与过去的工作进行更直接的比较，而异质性模型的结果则提供了密度估计的可能性，这种估计不太可能产生负偏差。使用常数模型²在苏厄德半岛的部分地区，诺阿塔克河下游，诺阿塔克河上游以及北极国家公园和自然保护区的大门上。这些估算值与阿拉斯加内陆和西北部以往工作的估算值大致相似，但下游的Noatak河子地区除外，在该地区，我们的估算值是阿拉斯加北部熊种群的最高记录。我们估计，根据所使用的模型，苏厄德半岛的收割率平均约为5.2％或7.7％。在其余地区，我们估计年收成低于2.5％，完全符合过去工作的可持续发展准则。总体而言，我们的结果表明，阿拉斯加西北部的大部分地区的棕熊密度与过去相似或略高，而且大多数地区的当前收成率是可持续的，除了苏厄德半岛。正在进行的调查工作将有助于进一步评估修改后的标记检验调查方法的假设，评估种群轨迹以及确定收获对棕熊种群的影响。©2021野生动物协会。