McIntosh Rebecca R, Sorrell Karina J, Thalmann Sam, Mitchell Anthony, Gray Rachael, Schinagl Harley, Arnould John P Y, Dann Peter, Kirkwood Roger
Conservation Department, Phillip Island Nature Parks, Cowes, Victoria, Australia.
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
PLoS One. 2022 Mar 18;17(3):e0265610. doi: 10.1371/journal.pone.0265610. eCollection 2022.
Fur seal populations in the Southern Hemisphere were plundered in the late 1700s and early 1800s to provide fur for a clothing industry. Millions of seals were killed resulting in potentially major ecosystem changes across the Southern Hemisphere, the consequences of which are unknown today. Following more than a century of population suppression, partly through on-going harvesting, many of the fur seal populations started to recover in the late 1900s. Australian fur seals (Arctocephalus pusillus doriferus), one of the most geographically constrained fur seal species, followed this trend. From the 1940s to 1986, pup production remained at approximately 10,000 per year, then significant growth commenced. By 2007, live pup abundance had recovered to approximately 21,400 per year and recovery was expected to continue However, a species-wide survey in 2013 recorded a 20% decline, to approximately 16,500 live pups. It was not known if this decline was due to 2013 being a poor breeding year or a true population reduction. Here we report the results of a population-wide survey conducted in 2017 and annual monitoring at the most productive colony, Seal Rocks, Victoria that recorded a large decline in live pup abundance (-28%). Sustained lower pup numbers at Seal Rocks from annual counts between 2012-2017 (mean = 2908 ± 372 SD), as well as the population-wide estimate of 16,903 live pups in 2017, suggest that the pup numbers for the total population have remained at the lower level observed in 2013 and that the 5-yearly census results are not anomalies or representative of poor breeding seasons. Potential reasons for the decline, which did not occur range-wide but predominantly in the most populated and long-standing breeding sites, are discussed. To enhance adaptive management of this species, methods for future monitoring of the population are also presented. Australian fur seals occupy several distinct regions influenced by different currents and upwellings: range-wide pup abundance monitoring enables comparisons of ecosystem status across these regions. Forces driving change in Australian fur seal pup numbers are likely to play across other marine ecosystems, particularly in the Southern Hemisphere where most fur seals live.
18世纪末和19世纪初,南半球的海狗种群遭到大肆捕杀,以获取用于制衣业的皮毛。数百万只海豹被猎杀,这可能导致了整个南半球生态系统的重大变化,而其后果至今仍不明朗。在经历了一个多世纪的种群抑制后,部分原因是持续的捕猎,许多海狗种群在20世纪后期开始恢复。澳大利亚海狗(Arctocephalus pusillus doriferus)是地理分布最受限制的海狗物种之一,也遵循了这一趋势。从20世纪40年代到1986年,幼崽产量每年约为10000只,之后开始显著增长。到2007年,存活幼崽数量已恢复到每年约21400只,预计恢复还将继续。然而,2013年的一次全物种调查记录了数量下降了20%,降至约16500只存活幼崽。尚不清楚这种下降是因为2013年繁殖不佳还是真正的种群减少。在此,我们报告了2017年进行的一次全种群调查结果以及在维多利亚州海豹岩这个繁殖力最强的栖息地的年度监测情况,该监测记录了存活幼崽数量大幅下降(-28%)。2012 - 2017年海豹岩年度统计中幼崽数量持续较低(平均值 = 2908 ± 372标准差),以及2017年全种群估计有16903只存活幼崽,这表明整个种群的幼崽数量一直维持在2013年观察到的较低水平,而且每五年一次的普查结果并非异常情况或代表繁殖不佳的季节。文中讨论了数量下降的潜在原因,这种下降并非在整个分布范围内发生,而是主要出现在种群数量最多且历史最久的繁殖地。为加强对该物种的适应性管理,还介绍了未来种群监测的方法。澳大利亚海狗占据了几个受不同洋流和上升流影响的不同区域:全分布范围内的幼崽数量监测能够比较这些区域的生态系统状况。导致澳大利亚海狗幼崽数量变化的因素可能在其他海洋生态系统中也起作用,尤其是在大多数海狗生活的南半球。