Whale sightings during POLARASTERN cruise PS139/2@en

Data on whale distribution and abundance in the polar oceans is rather sparse, as implementing the standard surveying method, line-transect surveys, is challenging and costly. To overcome this problem, we initiated a program to electronically log all opportunistic cetacean sightings during all Polarstern expeditions through the nautical officer on watch. Opportunistic (visual) sightings by naked eye were logged during Polarstern Cruise PS139/2 (Las Palmas – Cape Town) by the nautical officer on duty using a customized Software package (WALOG, WhAleLOGger) installed on a touch screen laptop located on the ship's bridge. Species were identified by naked eye or handheld binoculars (7x50) to the lowest possible taxonomical level and assigned a \"certainty\" level of identification. The number of animals were counted if possible or estimated for larger groups. Whenever identification to species level was not possible, the next identifiable taxonomical category was assigned. Information on sighting position, date and time are automatically transferred from the ship's DAVIS-Ship System (https://dship.awi.de/) to the WALOG software at the time of logging. Photographs were taken, if possible, for retrospective analysis. All data of acquired sightings were retrospectively validated by a marine biologist and converted to a standard format. To this end, plausibility of sighting time, location, standardization of species names, eventual comments added at the time of sighting, as well as additional information such as photographs (if available) were checked either to verify or improve species identification. Datasets are used in species distribution modelling and to inform interested parties about occurrences.

极地海洋中鲸类分布与种群丰度的数据相当匮乏，因为实施标准调查方法——线样带调查（line-transect surveys）——不仅难度颇高，且成本高昂。为破解这一困境，我们启动了一项研究计划：依托当班航海官员，在所有极星号（Polarstern）科考航次中，以电子日志形式记录所有偶遇鲸类目击记录。在极星号PS139/2航次（拉斯帕尔马斯—开普敦航线）中，当班航海官员借助安装于舰桥触控笔记本电脑上的定制化软件包WALOG（WhAleLOGger），以裸眼目视方式记录了偶遇式鲸类目击事件。科研人员通过裸眼或手持7×50型双筒望远镜，将物种鉴定至尽可能精细的分类学层级，并为每个目击记录分配鉴定置信度等级。若条件允许，则直接统计动物个体数量；对于大型群体，则采用估算方法得到数量。若无法鉴定至物种层级，则将目击记录归类至下一级可识别的分类单元。目击位置、日期与时间信息会在记录生成时，自动从船舶DAVIS-Ship系统（DAVIS-Ship System，https://dship.awi.de/）同步至WALOG软件。如有条件，会拍摄目击场景照片用于回溯分析。所有已获取的目击数据均由专业海洋生物学家进行回溯验证，并转换为统一标准格式。为此，我们会核查目击时间与位置的合理性、物种名称的标准化处理、目击时添加的附带注释，以及照片（若有）等额外信息，以此验证或优化物种鉴定结果。本数据集可应用于物种分布建模，并可为相关方提供鲸类出现情况的参考信息。