Higdon Jeff W, Ferguson Steven H
Department of Geography, Clayton H. Riddell Faculty of Environment, Earth, and Resources, University of Manitoba, 501 University Crescent, Winnipeg, Manitoba R3T2N6, Canada.
Ecol Appl. 2009 Jul;19(5):1365-75. doi: 10.1890/07-1941.1.
Killer whales (Orcinus orca) are major predators that may reshape marine ecosystems via top-down forcing. Climate change models predict major reductions in sea ice with the subsequent expectation for readjustments of species' distribution and abundance. Here, we measure changes in killer whale distribution in the Hudson Bay region with decreasing sea ice as an example of global readjustments occurring with climate change. We summarize records of killer whales in Hudson Bay, Hudson Strait, and Foxe Basin in the eastern Canadian Arctic and relate them to an historical sea ice data set while accounting for spatial and temporal autocorrelation in the data. We find evidence for "choke points," where sea ice inhibits killer whale movement, thereby creating restrictions to their Arctic distribution. We hypothesize that a threshold exists in seasonal sea ice concentration within these choke points that results in pulses in advancements in distribution of an ice-avoiding predator. Hudson Strait appears to have been a significant sea ice choke point that opened up .approximately 50 years ago allowing for an initial punctuated appearance of killer whales followed by a gradual advancing distribution within the entire Hudson Bay region. Killer whale sightings have increased exponentially and are now reported in the Hudson Bay region every summer. We predict that other choke points will soon open up with continued sea ice melt producing punctuated predator-prey trophic cascades across the Arctic.
虎鲸（逆戟鲸）是主要的捕食者，可能通过自上而下的压力重塑海洋生态系统。气候变化模型预测海冰将大幅减少，随之而来的是物种分布和丰度的重新调整。在此，我们以哈德逊湾地区虎鲸分布随海冰减少的变化为例，来研究气候变化引发的全球范围重新调整。我们汇总了加拿大北极地区东部哈德逊湾、哈德逊海峡和福克斯盆地虎鲸的记录，并将其与历史海冰数据集相关联，同时考虑数据中的空间和时间自相关性。我们发现了“瓶颈点”的证据，即海冰阻碍了虎鲸的移动，从而限制了它们在北极的分布。我们推测，在这些瓶颈点内的季节性海冰浓度存在一个阈值，这导致了一种避开冰的捕食者分布推进的脉冲现象。哈德逊海峡似乎一直是一个重要的海冰瓶颈点，大约在50年前打开，使得虎鲸最初突然出现，随后在整个哈德逊湾地区逐渐扩散。虎鲸目击报告呈指数增长，现在每年夏天在哈德逊湾地区都有相关报告。我们预测，随着海冰持续融化，其他瓶颈点将很快打开，在北极地区产生间断性的捕食者 - 猎物营养级联效应。
