Data_Sheet_3_Spatial Connectivity and Drivers of Shark Habitat Use Within a Large Marine Protected Area in the Caribbean, The Bahamas Shark Sanctuary.docx

Marine protected areas (MPAs) have emerged as potentially important conservation tools for the conservation of biodiversity and mitigation of climate impacts. Among MPAs, a large percentage has been created with the implicit goal of protecting shark populations, including 17 shark sanctuaries which fully protect sharks throughout their jurisdiction. The Commonwealth of the Bahamas represents a long-term MPA for sharks, following the banning of commercial longlining in 1993 and subsequent designation as a shark sanctuary in 2011. Little is known, however, about the long-term behavior and space use of sharks within this protected area, particularly among reef-associated sharks for which the sanctuary presumably offers the most benefit. We used acoustic telemetry to advance our understanding of the ecology of such sharks, namely Caribbean reef sharks (Carcharhinus perezi) and tiger sharks (Galeocerdo cuvier), over two discrete islands (New Providence and Great Exuma) varying in human activity level, over 2 years. We evaluated which factors influenced the likelihood of detection of individuals, analyzed patterns of movement and occurrence, and identified variability in habitat selection among species and regions, using a dataset of 23 Caribbean reef sharks and 15 tiger sharks which were passively monitored in two arrays with a combined total of 13 acoustic receivers. Caribbean reef sharks had lower detection probabilities than tiger sharks, and exhibited relatively low habitat connectivity and high residency, while tiger sharks demonstrated wider roaming behavior across much greater space. Tiger sharks were associated with shallow seagrass habitats where available, but frequently transited between and connected different habitat types. Our data support the notion that large MPAs afford greater degrees of protection for highly resident species such as Caribbean reef sharks, yet still may provide substantial benefits for more migratory species such as tiger sharks. We discuss these findings within the context of species-habitat linkages, ecosystem services, and the establishment of future MPAs.

海洋保护区（Marine Protected Areas, MPAs）已成为保护生物多样性、缓解气候影响的重要潜在保护工具。在各类海洋保护区中，有相当比例的设立初衷为保护鲨鱼种群，其中包含17个在管辖全域内全面保护鲨鱼的鲨鱼保护区（shark sanctuaries）。巴哈马联邦长期以来都是鲨鱼的海洋保护区域：1993年该国禁止商业延绳钓作业，随后于2011年被正式设立为鲨鱼保护区（shark sanctuary）。然而，人们对该保护区内鲨鱼的长期行为与空间利用模式知之甚少，尤其是礁栖鲨鱼这类理论上可从该保护区获得最大保护效益的类群。本研究于两年时间内，在人类活动水平存在差异的两座独立岛屿（新普罗维登斯岛与大埃克苏马岛），采用声学遥测（acoustic telemetry）技术深化对这类鲨鱼生态学特征的认知，研究对象为加勒比礁鲨（Carcharhinus perezi）与虎鲨（Galeocerdo cuvier）。本研究依托23尾加勒比礁鲨与15尾虎鲨的监测数据集，通过两套总计13台声学接收器组成的接收阵列对其进行被动监测，分析了影响个体被检测概率的因素、鲨鱼的移动与出现模式，并明确了不同物种与区域间栖息地选择的差异性。相较于虎鲨，加勒比礁鲨的个体检测概率更低，且栖息地连通性较弱、居留性更高；而虎鲨则展现出更大范围的漫游活动，活动空间跨度更广。虎鲨偏好栖息于存在浅海海草床的生境，且频繁穿梭于不同生境类型之间以实现生境连通。本研究数据佐证了这一观点：大型海洋保护区可为加勒比礁鲨这类高居留性物种提供更高程度的保护，同时也能为虎鲨这类洄游性物种带来可观的保护效益。本研究还从物种-生境关联、生态系统服务以及未来海洋保护区设立的视角，对上述研究结果展开了讨论。