Shabangu Fannie W, Yemane Dawit, Stafford Kathleen M, Ensor Paul, Findlay Ken P
Fisheries Management, Department of Agriculture, Forestry and Fisheries, Foreshore, Cape Town, South Africa.
Mammal Research Institute Whale Unit, University of Pretoria, Wynberg, South Africa.
PLoS One. 2017 Feb 21;12(2):e0172705. doi: 10.1371/journal.pone.0172705. eCollection 2017.
Harvested to perilously low numbers by commercial whaling during the past century, the large scale response of Antarctic blue whales Balaenoptera musculus intermedia to environmental variability is poorly understood. This study uses acoustic data collected from 586 sonobuoys deployed in the austral summers of 1997 through 2009, south of 38°S, coupled with visual observations of blue whales during the IWC SOWER line-transect surveys. The characteristic Z-call and D-call of Antarctic blue whales were detected using an automated detection template and visual verification method. Using a random forest model, we showed the environmental preferences pattern, spatial occurrence and acoustic behaviour of Antarctic blue whales. Distance to the southern boundary of the Antarctic Circumpolar Current (SBACC), latitude and distance from the nearest Antarctic shores were the main geographic predictors of blue whale call occurrence. Satellite-derived sea surface height, sea surface temperature, and productivity (chlorophyll-a) were the most important environmental predictors of blue whale call occurrence. Call rates of D-calls were strongly predicted by the location of the SBACC, latitude and visually detected number of whales in an area while call rates of Z-call were predicted by the SBACC, latitude and longitude. Satellite-derived sea surface height, wind stress, wind direction, water depth, sea surface temperatures, chlorophyll-a and wind speed were important environmental predictors of blue whale call rates in the Southern Ocean. Blue whale call occurrence and call rates varied significantly in response to inter-annual and long term variability of those environmental predictors. Our results identify the response of Antarctic blue whales to inter-annual variability in environmental conditions and highlighted potential suitable habitats for this population. Such emerging knowledge about the acoustic behaviour, environmental and habitat preferences of Antarctic blue whales is important in improving the management and conservation of this highly depleted species.
在过去的一个世纪里，南极蓝鲸（Balaenoptera musculus intermedia）因商业捕鲸而数量锐减至危险的低水平，人们对其对环境变化的大规模反应了解甚少。本研究使用了1997年至2009年南半球夏季在南纬38°以南部署的586个声呐浮标收集的声学数据，并结合了国际捕鲸委员会（IWC）同步调查期间对蓝鲸的目视观测。采用自动检测模板和目视验证方法检测南极蓝鲸特有的Z叫声和D叫声。我们使用随机森林模型展示了南极蓝鲸的环境偏好模式、空间分布和声学行为。到南极绕极流南部边界（SBACC）的距离、纬度以及到最近南极海岸的距离是蓝鲸叫声出现的主要地理预测因子。卫星衍生的海面高度、海面温度和生产力（叶绿素a）是蓝鲸叫声出现的最重要环境预测因子。D叫声的发生率由SBACC的位置、纬度以及该区域目视检测到的鲸鱼数量强烈预测，而Z叫声的发生率则由SBACC、纬度和经度预测。卫星衍生的海面高度、风应力、风向、水深、海面温度、叶绿素a和风速是南大洋蓝鲸叫声发生率的重要环境预测因子。蓝鲸叫声的出现和发生率因这些环境预测因子的年际和长期变化而有显著差异。我们的研究结果确定了南极蓝鲸对环境条件年际变化的反应，并突出了该种群潜在的适宜栖息地。这种关于南极蓝鲸声学行为、环境和栖息地偏好的新知识对于改善对这种极度濒危物种的管理和保护至关重要。
