Ecologists and managers require accurate population estimates of marine mammals to assess potential anthropogenic threats to these animals. We present estimates of in‐water density and abundance of a distinct stock of harbor seals (Phoca vitulina richardii) in Hood Canal, Washington, USA. We used aerial line‐transect survey data collected from 2013 to 2016 to directly estimate harbor seal density and abundance in the waters of Hood Canal, a deep‐water fjord in the Salish Sea. We estimated a correction factor for trackline detection probability from dive and surface time data gathered from regional seal tagging studies, and applied this factor to correct for seals missed on the trackline during surveys. We applied conventional and multiple covariate line‐transect approaches in the analysis. The resulting best estimate of in‐water density of harbor seals in the Hood Canal study region was 5.80 seals/km², with an estimated abundance of 2,009 seals. We did not derive a correction factor to account for the number of seals on land (i.e., hauled out). Therefore, these estimates do not reflect total stock size but provide a starting point to evaluate potential influences of anthropogenic activities, particularly those involving underwater noise, on this marine mammal stock. © 2021 The Wildlife Society.

中文翻译：

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水中密度和海豹丰度的估算

生态学家和管理人员需要对海洋哺乳动物进行准确的种群估计，以评估对这些动物的潜在人为威胁。我们提出了不同密度的海豹（Phoca vitulina richardii）的水中密度和丰度的估计值），位于美国华盛顿的胡德运河。我们使用2013年至2016年收集的空中线剖面调查数据直接估算了萨利什海深水峡湾胡德运河水域的海豹密度和丰度。我们从区域海豹标记研究收集的潜水和水面时间数据中估计了航迹检测概率的校正因子，并应用该因子校正了勘测过程中在航迹上遗漏的海豹。我们在分析中应用了常规和多个协变量线样线方法。由此得出的对胡德运河研究区域的海豹海豹密度的最佳估计为5.80海豹/ km ²，估计有2,009只海豹。我们没有得出校正因子来说明陆地上的海豹数量（即，拖出的海豹数量）。因此，这些估计数并不反映种群总数，而是提供一个起点来评估人为活动对该海洋哺乳动物种群的潜在影响，特别是涉及水下噪声的活动。©2021野生动物协会。