Eisaguirre Joseph M, Williams Perry J, Lu Xinyi, Kissling Michelle L, Beatty William S, Esslinger George G, Womble Jamie N, Hooten Mevin B
Department of Natural Resources and Environmental Science, University of Nevada Reno, Reno, NV, USA.
United States Fish & Wildlife Service, Marine Mammals Management, Anchorage, AK, USA.
Mov Ecol. 2021 Jun 30;9(1):34. doi: 10.1186/s40462-021-00270-w.
Reintroducing predators is a promising conservation tool to help remedy human-caused ecosystem changes. However, the growth and spread of a reintroduced population is a spatiotemporal process that is driven by a suite of factors, such as habitat change, human activity, and prey availability. Sea otters (Enhydra lutris) are apex predators of nearshore marine ecosystems that had declined nearly to extinction across much of their range by the early 20th century. In Southeast Alaska, which is comprised of a diverse matrix of nearshore habitat and managed areas, reintroduction of 413 individuals in the late 1960s initiated the growth and spread of a population that now exceeds 25,000.
Periodic aerial surveys in the region provide a time series of spatially-explicit data to investigate factors influencing this successful and ongoing recovery. We integrated an ecological diffusion model that accounted for spatially-variable motility and density-dependent population growth, as well as multiple population epicenters, into a Bayesian hierarchical framework to help understand the factors influencing the success of this recovery.
Our results indicated that sea otters exhibited higher residence time as well as greater equilibrium abundance in Glacier Bay, a protected area, and in areas where there is limited or no commercial fishing. Asymptotic spread rates suggested sea otters colonized Southeast Alaska at rates of 1-8 km/yr with lower rates occurring in areas correlated with higher residence time, which primarily included areas near shore and closed to commercial fishing. Further, we found that the intrinsic growth rate of sea otters may be higher than previous estimates suggested.
This study shows how predator recolonization can occur from multiple population epicenters. Additionally, our results suggest spatial heterogeneity in the physical environment as well as human activity and management can influence recolonization processes, both in terms of movement (or motility) and density dependence.
重新引入捕食者是一种很有前景的保护手段，有助于补救人类导致的生态系统变化。然而，重新引入种群的增长和扩散是一个时空过程，受到一系列因素的驱动，如栖息地变化、人类活动和猎物可获得性。海獭（Enhydra lutris）是近岸海洋生态系统的顶级捕食者，到20世纪初，其在大部分分布范围内已几近灭绝。在阿拉斯加东南部，这里由多种近岸栖息地和管理区域构成，20世纪60年代末重新引入413只海獭，启动了一个如今数量超过25000只的种群的增长和扩散。
该地区定期的空中调查提供了一系列空间明确的数据，以调查影响这一成功且仍在进行的恢复过程的因素。我们将一个生态扩散模型（该模型考虑了空间可变的移动性和密度依赖的种群增长，以及多个种群中心）整合到一个贝叶斯分层框架中，以帮助理解影响这一恢复成功的因素。
我们的结果表明，海獭在保护区冰川湾以及商业捕鱼有限或没有商业捕鱼的区域停留时间更长，平衡丰度也更高。渐近扩散率表明，海獭以每年1 - 8千米的速度在阿拉斯加东南部定殖，在与停留时间较长相关的区域扩散速度较低，这些区域主要包括近岸且禁止商业捕鱼的区域。此外，我们发现海獭的内在增长率可能高于先前的估计。
本研究展示了捕食者如何从多个种群中心重新定殖。此外，我们的结果表明，物理环境以及人类活动和管理中的空间异质性，在移动性（或迁移能力）和密度依赖性方面，都可以影响重新定殖过程。
