Little information exists on the current status of Southern Hemisphere sei whales (Balaenoptera borealis). We assessed their distribution and abundance along the west coast of the Falkland Islands (southwest Atlantic) during February and March 2018, using line transect and nonsystematic surveys. Abundance estimates were generated for a single survey stratum using design- and model-based approaches. Sightings of sei whales and unidentified baleen whales (most, if not all, likely to be sei whales) occurred from the coast to the 100 m depth isobath that marked the offshore boundary of the stratum. The modeled distribution predicted highest whale densities in King George Bay and in the waters between Weddell Island and the Passage Islands. Sei whale abundance was estimated as 716 animals (CV = 0.22; 95% CI [448, 1,144]; density = 0.20 whales/km²) using the design-based approach, and 707 animals (CV = 0.11; 95% CI [566, 877]; density = 0.20 whales/km²) using the model-based approach. For sei whales and unidentified baleen whales combined, the equivalent estimates were 916 animals (CV = 0.19; 95% CI [606, 1,384]; density = 0.26 whales/km²) and 895 animals (CV = 0.074; 95% CI [777, 1,032]; density = 0.25 whales/km²). The data indicate that the Falkland Islands inner shelf region may support globally important seasonal feeding aggregations of sei whales, and potentially qualify as a Key Biodiversity Area.

中文翻译：

---

福克兰群岛西海岸塞鲸的分布和丰度

关于南半球塞鲸（Balaenoptera borealis）现状的信息很少。我们在 2018 年 2 月和 3 月期间使用线样带和非系统调查评估了它们在福克兰群岛（西南大西洋）西海岸的分布和丰度。使用基于设计和模型的方法为单个调查层生成了丰度估计。从海岸到标志着地层离岸边界的 100 m 深度等深线发现了塞鲸和身份不明的须鲸（大多数，如果不是全部，很可能是塞鲸）。模型分布预测了乔治王湾以及威德尔岛和通道群岛之间水域的最高鲸鱼密度。塞鲸的丰度估计为 716 只动物（CV = 0.22; 95% 置信区间 [448, 1,144]；密度 = 0.20 头鲸/km ²）使用基于设计的方法，707 只动物（CV  = 0.11；95% CI [566, 877]；密度 = 0.20 头鲸/km ²）使用基于模型的方法。对于塞鲸和身份不明的须鲸加起来，等效估计数为 916 只动物（CV  = 0.19；95% CI [606, 1,384]；密度 = 0.26 头鲸/km ²）和 895 只动物（CV  = 0.074；95% CI [777] , 1,032]；密度 = 0.25 头鲸鱼/km ²）。数据表明，福克兰群岛内陆架区域可能支持塞鲸在全球范围内重要的季节性觅食聚集地，并有可能成为关键生物多样性区。