Sea Mammal Research Unit (SMRU) UK aerial surveys of harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) during the summer harbour seal moult 2016-2019

The Sea Mammal Research Unit (SMRU) conducts an ongoing programme of aerial surveys along the English and Scottish coastlines during the harbour seal (Phoca vitulina) summer moult. These surveys are funded by the Natural Environment Research Council (NERC National Capability Funding, Grant Numbers SMRU10001 and NE/R015007/1), NatureScot, formerly Scottish Natural Heritage (SNH), and Natural England. To monitor harbour seal numbers, individuals onshore are counted in August, during their annual moult season, when animals generally spend more time hauled out. Such moult season counts tend to be slightly higher and more consistent than at other times of year. Grey seals (Halichoerus grypus) are also counted during these summer surveys, but their distribution can change more throughout the year because they congregate in breeding colonies during the autumn. These aerial surveys are conducted within 2 hours of low water using either a helicopter or fixed-wing aircraft. No surveying is carried out during periods with prolonged rain or heavy showers. The helicopter surveys began in 1988 and cover a different area each year. A full round of Scotland usually takes 3-5 years to complete. This dataset covers the 2016-2019 round of helicopter surveys that used multi-sensor (infrared, high-resolution DSLR, and video) gimbal-led imaging. Parts of the Moray Firth as well as the Firth of Tay and Eden Estuary Special Area of Conservation (SAC) are surveyed annually. Almost all the seals here haul out on sandbanks, which makes them much easier to spot. For that reason, less expensive fixed-wing aircraft and hand-held photography can be used. The same applies to the main harbour seal areas in England. Each year, SMRU performs fixed-wing surveys of the coastlines of Lincolnshire and Norfolk between Donna Nook and Scroby Sands. Less frequently, SMRU also surveys the Thames Estuary from Felixstowe to Goodwin Sands (fixed wing 2018 and 2019), the East Coast from around Coquet Island to Flamborough Head (fixed-wing 2016), and the Berwickshire and North Northumberland Coast SAC (helicopter 2018). The presence/absence and counts of hauled-out individuals from each of the years from 2016 to 2019 have been aggregated using the cells of a 5 km x 5 km UTM zone 30N (EPSG:32630) grid. Mean values are given for cells surveyed more than once in a single season. No value is reported if only part of the intertidal zone within a given cell was surveyed during a given year. The reports produced by SMRU for NERC’s Special Committee on Seals (SCOS), in particular Briefing Papers 17/03, 18/04, 19/03, and 20/03 in the 2017-2020 reports, contain additional information on these surveys and the data gathered. These are available from SMRU’s website: http://www.smru.st-andrews.ac.uk/scos/scos-reports/ Further details of the Scottish surveys over this period and the data they collected can also be found in this report: NatureScot Research Report 1256 - Aerial surveys of seals in Scotland during the harbour seal moult, 2016-2019 https://www.nature.scot/doc/naturescot-research-report-1256-aerial-surveys-seals-scotland-during-harbour-seal-moult-2016-2019海洋哺乳动物研究单元（Sea Mammal Research Unit, SMRU）长期开展航空调查项目，在港海豹（Phoca vitulina）夏季换毛期沿英格兰与苏格兰海岸线进行作业。本项目由自然环境研究委员会（Natural Environment Research Council, NERC，资助编号：SMRU10001与NE/R015007/1）、苏格兰自然署（前身为苏格兰自然遗产局Scottish Natural Heritage, SNH）以及英格兰自然署资助。 为监测港海豹种群数量，调查于每年8月港海豹年度换毛季开展，此时港海豹上岸休憩的时长显著增加，可对沿岸个体进行计数。换毛季的种群计数结果通常略高于其他时段，且一致性更强。本次夏季调查同时记录灰海豹（Halichoerus grypus）的数量，但灰海豹的全年分布变化幅度更大——它们会在秋季聚集于繁殖群落。 本次航空调查需在低潮前后2小时内开展，可使用直升机或固定翼飞机执行。若遭遇持续降雨或强阵雨，则暂停调查。直升机调查始于1988年，每年覆盖不同区域，完整覆盖苏格兰全境通常需要3至5年。 本数据集涵盖2016至2019年度的直升机调查数据，该批次调查采用多传感器（红外、高分辨率数码单反及视频）云台成像系统。莫雷湾（Moray Firth）、泰湾（Firth of Tay）与埃登河口特别保育区（Eden Estuary Special Area of Conservation, SAC）的部分区域每年都会开展调查。该区域内几乎所有海豹均栖息于沙洲之上，便于观测，因此可使用成本更低的固定翼飞机与手持摄影设备。英格兰境内的港海豹主要栖息区域也采用相同的调查方式。 每年，SMRU都会在林肯郡与诺福克郡海岸线开展固定翼调查，作业范围从唐纳诺克（Donna Nook）至斯克罗比桑兹（Scroby Sands）。此外，SMRU还会不定期开展其他区域的调查：2018与2019年使用固定翼飞机调查泰晤士河口（从费利克斯托至古德温桑兹）；2016年使用固定翼飞机调查从科克特岛附近至弗拉姆伯勒角的东海岸区域；2018年使用直升机调查贝里克郡与北诺森伯兰海岸特别保育区（Berwickshire and North Northumberland Coast SAC）。 2016至2019年各年度的上岸个体出现与否及计数结果，均以5km×5km的UTM 30N带（EPSG:32630）网格单元进行聚合。若单个网格单元在单个季节内被多次调查，则给出其均值；若某年度仅对给定网格内的潮间带区域进行了部分勘测，则不报告该单元的数值。 SMRU为NERC海豹特别委员会（Special Committee on Seals, SCOS）提交的报告，尤其是2017至2020年度的简报文件17/03、18/04、19/03与20/03，包含了本次调查及采集数据的更多细节，可从SMRU官网获取：http://www.smru.st-andrews.ac.uk/scos/scos-reports/ 此外，本时段苏格兰调查的更多细节及采集数据，可参阅以下报告：《苏格兰自然署研究报告1256：2016-2019年港海豹换毛期苏格兰海域海豹航空调查》，链接：https://www.nature.scot/doc/naturescot-research-report-1256-aerial-surveys-seals-scotland-during-harbour-seal-moult-2016-2019