Data from: Shark movement strategies influence poaching risk and can guide enforcement decisions in a large, remote Marine Protected Area

Large, remote marine protected areas (MPAs) containing both reef and pelagic habitats, have been shown to offer considerable refuge to populations of reef-associated sharks. Many large MPAs are, however, impacted by illegal fishing activity conducted by unlicensed vessels. While enforcement of these reserves is often expensive, it would likely benefit from the integration of ecological data on the mobile animals they are designed to protect. Consequently, shark populations in some protected areas continue to decline, as they remain a prime target for illegal fishers. To understand shark movements and their vulnerability to illegal fishing, three years of acoustic tracking data, from 101 reef-associated sharks, were analysed as movement networks to explore the predictability of movement patterns and identify key movement corridors within the British Indian Ocean Territory (BIOT) MPA. We examined how space use and connectivity overlap with spatially-explicit risk of illegal fishing, through data obtained from the management consultancy enforcing the MPA. Using individual-based models, the movement networks of two sympatric shark species were efficiently predicted with distance-decay functions (>95% movements accurately predicted). Model outliers were used to highlight the locations with unexpectedly high movement rates where MPA enforcement patrols might most efficiently mitigate predator removal. Activity space estimates and network metrics illustrate that silvertip sharks were more dynamic, less resident and link larger components of the MPA than grey reef sharks. However, we show that this behaviour potentially enhances their exposure to illegal fishing activity. Synthesis and applications. Marine protected area (MPA) enforcement strategies are often limited by resources. The British Indian Ocean Territory MPA, one of the world’s largest ‘no take’ MPAs, has a single patrol vessel to enforce 640,000 km2 of open ocean, atoll and reef ecosystems. We argue that to optimise the patrol vessel search strategy and thus enhance their protective capacity, ecological data on the space use and movements of desirable species, such as large-bodied reef predators, must be incorporated into management plans. Here, we use electronic tracking data to evaluate how shark movement dynamics influence species mortality trajectories in exploited reef ecosystems. In doing so we discuss how network analyses of such data might be applied for protected area enforcement.,Acoustic detection data 2013-2016All acoustic detection data used for analysis of silvertip and grey reef sharks in the British Indian Ocean Territory between 2013 and 2016. Receiver locations have been removed from the data and are referred to by station name.Acoustic Data DJacoby.csv,Acoustic tags were surgically implanted in 101 sharks reef sharks during February-April between 2013 and 2016. Sharks were tracked for three years across five isolated atoll systems in the north of the British Indian Ocean Territory Marine Protected Area. The study array consisted of a total of 52 Vemco acoustic receivers (Vemco, Nova Scotia, Canada, 46 VR2Ws, plus four VR2W-UWM and two VR4Gs) with additional receivers placed further afield in the archipelago excluded from the analyses due to later deployment dates or lack of data from this cohort of animals. Sharks were caught at various locations around the northern atolls using hand-lines with barbless circle hooks and brought alongside or into the boat. Vemco V16 acoustic tags were surgically implanted into the shark and had a expected duration of up to 10 years. Data were downloaded on an annual basis and filtered for false detections prior to finalising the data for analysis.,

大型偏远海洋保护区（Marine Protected Area, MPA）兼具珊瑚礁与远洋生境，已被证实可为礁栖鲨鱼种群提供可观的庇护所。然而，诸多大型MPA仍受无许可船只开展的非法捕捞活动影响。尽管对这些保护区的执法往往成本高昂，但整合其旨在保护的移动动物的生态数据，或能大幅提升执法效能。部分保护区内的鲨鱼种群仍持续下降，因为它们仍是非法捕捞者的主要目标。
为理解鲨鱼的移动模式及其对非法捕捞的脆弱性，本研究对2013至2016年间101头礁栖鲨鱼的三年声学追踪数据进行分析，将其构建为移动网络，以探究移动模式的可预测性，并识别英国印度洋领地（British Indian Ocean Territory, BIOT）MPA内的关键移动廊道。我们结合该MPA执法管理咨询机构获取的数据，检验了空间利用与连通性如何与空间明确的非法捕捞风险重叠。通过基于个体的模型（individual-based models），我们利用距离衰减函数高效预测了两种同域鲨鱼物种的移动网络，预测准确率超95%的移动事件。模型异常值被用于标注移动速率意外偏高的区域，MPA执法巡逻队可在此最高效地减少捕食者遭捕捞移除的情况。
活动空间估算值与网络指标显示，相较于灰礁鲨，银鳍鲨的活动更为动态、居留性更低，且能连通MPA中更大范围的区域。但本研究表明，这种行为特性或会提升它们面临非法捕捞的风险。
### 综合与应用
海洋保护区（MPA）的执法策略往往受限于资源。英国印度洋领地MPA是全球规模最大的禁捕型MPA之一，仅配备1艘巡逻艇来管控64万平方公里的远洋、环礁与珊瑚礁生态系统。我们主张，为优化巡逻艇的搜索策略并提升其保护效能，必须将大型珊瑚礁捕食者等受保护物种的空间利用与移动模式的生态数据纳入管理规划。本研究利用电子追踪数据，评估了鲨鱼的移动动态如何影响被开发珊瑚礁生态系统中的物种死亡轨迹。借此，我们探讨了此类数据的网络分析方法可如何应用于保护区执法。

#### 声学检测数据（2013-2016年）
本部分包含2013至2016年间用于英国印度洋领地内银鳍鲨与灰礁鲨分析的全部声学检测数据。数据中已移除接收器的实际位置，仅以监测站名称指代。
数据文件名：Acoustic Data DJacoby.csv

#### 实验细节
2013至2016年的2-4月间，研究人员通过手术将声学标签植入101头礁栖鲨鱼体内。研究团队在英国印度洋领地北部的5个孤立环礁系统中，对这些鲨鱼进行了为期三年的追踪。研究阵列共包含52台Vemco声学接收器（加拿大新斯科舍省Vemco公司生产，其中46台VR2Ws、4台VR2W-UWM以及2台VR4Gs），另有部分部署于群岛更远区域的接收器因部署时间较晚或该组鲨鱼缺乏有效数据，未纳入本次分析。
研究人员使用无倒刺圆形钩手线在北部环礁周边的多个地点捕获鲨鱼，将其拖至船侧或船上。Vemco V16型声学标签通过手术植入鲨鱼体内，预计续航时长可达10年。数据每年下载一次，并在最终用于分析前过滤掉虚假检测记录。