Dinkel Thaya Mirinda, Girard Angélique, Bär Tom, Dähne Michael, Craul Ann-Kristin, Cosentino Mel, Meyer-Klaeden Ole, Dahlke Flemming, von Dorrien Christian
Thünen Institute of Baltic Sea Fisheries, Alter Hafen Süd 2, Rostock, Germany.
Institute of Marine Ecosystem and Fisheries Science, University of Hamburg, Große Elbstraße 133, Hamburg, Germany.
Sci Rep. 2025 Jun 25;15(1):20302. doi: 10.1038/s41598-025-06978-8.
Theodolites and drones are key instruments for observing small whales in coastal areas. This study compared their performance while observing the harbour porpoise (Phocoena phocoena) in the western Baltic Sea. The methods were used simultaneously providing information on location, behaviour and group size during a field campaign in 2022. Theodolite observers were able to detect surfacing positions during 80.5% of porpoise sightings while a drone collected data during 50.7% of total sightings detected by plain eye. The drone footage quality was poor during 47.3% of these sightings. An in-depth analysis of 75:36 h of good quality footage resulted in 16:55 h (22.4%) of cetacean appearance. The determination of group size was significantly more precise using drone footage while the theodolite was more accurate in determining the start/end of a sighting. The accuracy of locations was modelled using the distance (D) between recorded theodolite and drone coordinates of the same surfacing porpoise. D varied significantly based on the point quality. Sea state and porpoise to theodolite observer distance did not influence D. Both methods complement each other and should ideally be used simultaneously to obtain both accurate and detailed information on harbour porpoises and other marine mammals during land-based observation studies.
经纬仪和无人机是在沿海地区观测小须鲸的关键仪器。本研究比较了它们在波罗的海西部观测港湾鼠海豚（Phocoena phocoena）时的性能。在2022年的一次实地考察中，这些方法同时被使用，以提供有关位置、行为和群体大小的信息。经纬仪观测者能够在80.5%的鼠海豚目击事件中检测到浮出水面的位置，而无人机在肉眼检测到的总目击事件中的50.7%期间收集了数据。在这些目击事件中，47.3%的无人机拍摄画面质量较差。对75:36小时的高质量画面进行深入分析，得到16:55小时（22.4%）的鲸类动物出现画面。使用无人机拍摄画面确定群体大小明显更精确，而经纬仪在确定目击事件的开始/结束时间方面更准确。通过记录同一浮出水面鼠海豚的经纬仪和无人机坐标之间的距离（D）对位置准确性进行建模。D根据点质量有显著差异。海况和鼠海豚与经纬仪观测者的距离对D没有影响。这两种方法相互补充，理想情况下应同时使用，以便在陆基观测研究中获得关于港湾鼠海豚和其他海洋哺乳动物的准确和详细信息。
