Warwick-Evans V, Pearmain E J, Thorne L, Phillips R A
British Antarctic Survey, Natural Environment Research Council, Cambridge, UK.
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, USA.
Conserv Biol. 2025 Aug 20:e70126. doi: 10.1111/cobi.70126.
Spatial segregation in at-sea distribution is frequently observed in seabirds and can have important implications for conservation and management. Globally, many albatross and petrel populations are declining due to bycatch in fisheries. In South Georgia, the decrease in wandering albatrosses (Diomedea exulans) differs among breeding sites, which could reflect segregation in foraging areas, leading to differing degrees of overlap with particular fishing fleets and hence unequal bycatch risk. We investigated whether spatial segregation could explain the different rates of population decline of wandering albatrosses at South Georgia. We tracked wandering albatrosses from 2 breeding sites at South Georgia, Prion Island, and Bird Island, located 50 km apart. We investigated potential causes of spatial segregation with species distribution models and by comparing wind conditions among sites. Overlap with fisheries was quantified for each population. Although overall distributions were from the Antarctic to the subtropics, virtually all wandering albatrosses from Bird Island foraged only to the west of the island group, whereas those from Prion Island foraged to the east and west. Preferred habitat characteristics were similar at both colonies, and waters to the east and west provided foraging habitat. Wind conditions when birds departed were also similar at the 2 sites. Because neither habitat specialization nor wind conditions appeared to be factors in the observed spatial segregation among colonies, this segregation likely reflected a combination of past experience, information exchange, and cultural evolution. Breeding birds from both sites overlapped most with Chinese squid jiggers, Argentinian trawlers, and South Korean set (demersal) longliners, but the spatial segregation led to a higher overlap with demersal longline, demersal trawl, and pelagic longline fisheries by wandering albatrosses at Bird Island, which could have resulted in the faster population decline. Ours is one of the first studies to demonstrate how spatial segregation may affect population dynamics, which has important implications for the conservation of this globally threatened species.
海鸟在海上分布的空间隔离现象屡见不鲜，这对保护和管理具有重要意义。在全球范围内，许多信天翁和海燕种群因渔业兼捕而数量减少。在南乔治亚岛，漂泊信天翁（Diomedea exulans）在不同繁殖地的数量减少情况有所不同，这可能反映了觅食区域的隔离，导致与特定捕鱼船队的重叠程度不同，进而造成兼捕风险不均。我们研究了空间隔离是否能解释南乔治亚岛漂泊信天翁种群数量下降的不同速率。我们追踪了来自南乔治亚岛两个相距50公里的繁殖地——普里恩岛和鸟岛的漂泊信天翁。我们利用物种分布模型并通过比较各地点的风况来研究空间隔离的潜在原因。对每个种群与渔业的重叠情况进行了量化。尽管总体分布范围从南极到亚热带，但实际上鸟岛的所有漂泊信天翁仅在岛屿群以西觅食，而普里恩岛的漂泊信天翁则在东西两侧觅食。两个繁殖地的偏好栖息地特征相似，东西两侧的水域都提供了觅食栖息地。两个地点鸟类出发时的风况也相似。由于栖息地专业化和风况似乎都不是观察到的繁殖地间空间隔离的因素，这种隔离可能反映了过去的经验、信息交流和文化进化的综合作用。来自两个地点的繁殖鸟类与中国鱿鱼钓船、阿根廷拖网渔船和韩国底层（底栖）延绳钓船重叠最多，但空间隔离导致鸟岛的漂泊信天翁与底层延绳钓、底层拖网和中层延绳钓渔业的重叠度更高，这可能导致了更快的种群数量下降。我们的研究是首批证明空间隔离如何影响种群动态的研究之一，这对保护这种全球受威胁物种具有重要意义。
