Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, P.O. Box 1346, Kāne'ohe, HI 96744, USA.
Department of Ecology and Evolution, Stony Brook University, 650 Life Sciences Building, Stony Brook, NY, 11794, U.S.A.
Conserv Biol. 2020 Feb;34(1):256-265. doi: 10.1111/cobi.13416. Epub 2019 Sep 12.
Antarctic fur seals (Arctocephalus gazella) were commercially exploited on the subantarctic island of South Georgia for over 100 years and nearly driven to extinction. Since the cessation of harvesting, however, their populations have rebounded, and they are now often considered a nuisance species whose impact on the terrestrial landscape should be mitigated. Any evaluation of their current population requires the context provided by their historic, pre-exploitation abundance, lest ecologists fall prey to shifting baseline syndrome in which their perspective on current abundance is compared only with an altered state resulting from past anthropogenic disturbance. Estimating pre-exploitation abundance is critical to defining species recovery and setting recovery targets, both of which are needed for the International Union for the Conservation of Nature's recent efforts to develop a green list of recovering species. To address this issue, we reconstructed the South Georgia fur seal harvest from 1786 to 1908 from ship logbooks and other historical records and interpolated missing harvest data as necessary with a generalized linear model fit to the historical record. Using an approximate Bayesian computation framework, harvest data, and a stochastic age-structured population model, we estimated the pre-exploitation abundance of Antarctic fur seals on South Georgia was 2.5 million females (95% CI 1.5-3.5 million). This estimate is similar to recent abundance estimates, and suggests current populations, and the ecological consequences of so many fur seals on the island, may be similar to conditions prior to human harvest. Although the historic archive on the fur sealing era is unavoidably patchy, the use of archival records is essential for reconstructing the past and, correspondingly, to understanding the present. Article impact statement: Defining species recovery requires an understanding of baseline population state, which can be estimated through statistical methods.
南极软毛海豹（Arctocephalus gazella）在南乔治亚亚南极岛屿上被商业开发了 100 多年，几乎被捕杀至灭绝。然而，自停止捕捞以来，它们的数量已经反弹，现在它们通常被认为是一种滋扰物种，其对陆地景观的影响应该得到缓解。任何对其当前种群数量的评估都需要参考其历史上、开发前的丰富程度，以免生态学家陷入“基线转移综合征”，即他们对当前丰富程度的看法仅与过去人为干扰造成的改变后的状态进行比较。估计开发前的丰富程度对于定义物种恢复和设定恢复目标至关重要，这两者都是为了国际自然保护联盟最近努力制定一个恢复物种的绿色清单。为了解决这个问题，我们根据船只航海日志和其他历史记录，从 1786 年到 1908 年重建了南乔治亚软毛海豹的捕捞情况，并在必要时使用拟合历史记录的广义线性模型对缺失的捕捞数据进行插值。我们使用近似贝叶斯计算框架、捕捞数据和随机年龄结构种群模型，估计了南乔治亚软毛海豹在开发前的丰富程度为 250 万只雌性（95%置信区间为 150 万至 350 万只）。这一估计与最近的丰富程度估计相似，表明当前的种群数量以及如此多的软毛海豹在岛上的生态后果，可能与人类捕捞前的情况相似。尽管关于软毛海豹时代的历史档案不可避免地存在缺口，但利用档案记录对于重建过去以及相应地理解现在是至关重要的。
