Entanglement and count data for Steller sea lions and California sea lions in northwest Washington

Steller and California sea lions in northwest Washington were counted and monitored for entanglements from 2010 through 2018 to determine population trends and temporal and spatial patterns of entanglement rates for the two species. The collection of count data and the majority of monitoring of entanglements occurred at four major sea lion haulout complexes: Tatoosh Island, Bodelteh Islands, Carroll Island, and Sea Lion Rock. We conducted counts with the aid of 8x40 and 7x50 binoculars. We photographed each sea lion with evidence of entanglement using a digital SLR camera with powerful zoom lens of either 70-300 mm or 100-400 mm. Some entanglements were observed and recorded at minor haulouts outside of the four complexes and were recorded for purposes of characterizing the temporal patterns of what type of debris causes entanglements. After surveys, we processed photographs to determine characteristics of each entanglement event. Our first step was to evaluate if our photographs were of sufficient quality for subsequent analyses. If the photos were not, we often relied on field notes to record details on the entanglement. For each suitable photograph of an entanglement, we recorded the species of sea lion entangled and whether the entanglement was active or was a scar from a previous entanglement. For active entanglements, we recorded what type of debris caused the entanglement into twelve categories: fishing lure, flasher, gillnet, longline, monofilament, net, packing band, rope, rubber band, scar, trawl net, unknown. Last, we determined the sex and age of each entangled individual to allow analyses to determine if there were patterns in the type of marine debris that affected sea lions of different age, sex, and species.

2010年至2018年，研究人员对华盛顿州西北部的斯特勒海狮（Steller sea lion）与加州海狮（California sea lion）开展计数与缠结监测工作，旨在明确两种海狮的种群动态趋势，以及缠结率的时空分布模式。计数及绝大多数缠结监测工作均在4处主要海狮聚集休憩点复合体开展，分别为塔托什岛（Tatoosh Island）、博德尔泰群岛（Bodelteh Islands）、卡罗尔岛（Carroll Island）与海狮岩（Sea Lion Rock）。研究人员借助8×40及7×50型双筒望远镜完成种群计数。对于出现缠结迹象的海狮，使用搭载70-300mm或100-400mm长焦变焦镜头的数码单反相机（digital SLR）进行拍摄。此外，研究人员也在上述4处复合体以外的小型休憩点观测并记录缠结情况，以梳理引发缠结的海洋垃圾类型的时间分布特征。调研结束后，研究人员对拍摄照片进行处理，以提取每起缠结事件的相关特征。首先评估照片是否满足后续分析的质量要求，若照片质量不达标，则通常借助野外观测笔记补充缠结事件的细节信息。对于符合质量标准的缠结照片，研究人员会记录涉事海狮的物种，以及该缠结为活跃状态还是既往缠结遗留的疤痕。针对活跃缠结，将引发缠结的海洋垃圾划分为12个类别：钓鱼假饵、闪光诱鱼器、刺网、延绳钓组、单丝渔线、渔网、打包带、绳索、橡皮筋、疤痕、拖网、未知。最后，研究人员记录每头缠结个体的性别与年龄，以便开展后续分析，探究不同年龄、性别及物种的海狮所受海洋垃圾缠结的类型差异模式。