Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
J Acoust Soc Am. 2012 Jan;131(1):550-60. doi: 10.1121/1.3662070.
Monitoring abundance and population trends of small odontocetes is notoriously difficult and labor intensive. There is a need to develop alternative methods to the traditional visual line transect surveys, especially for low density areas. Here, the prospect of obtaining robust density estimates for porpoises by passive acoustic monitoring (PAM) is demonstrated by combining rigorous application of methods adapted from distance sampling to PAM. Acoustic dataloggers (T-PODs) were deployed in an area where harbor porpoises concurrently were tracked visually. Probability of detection was estimated in a mark-recapture approach, where a visual sighting constituted a "mark" and a simultaneous acoustic detection a "recapture." As a distance could be assigned to each visual observation, a detection function was estimated. Effective detection radius of T-PODs ranged from 22 to 104 m depending on T-POD type, T-POD sensitivity, train classification settings, and snapshot duration. The T-POD density estimates corresponded to the visual densities derived concurrently for the same period. With more dataloggers, located according to a systematic design, density estimates would be obtainable for a larger area. This provides a method suitable for monitoring in areas with densities too low for visual surveys to be practically feasible, e.g., the endangered harbor porpoise population in the Baltic.
监测小型齿鲸的数量和种群趋势是一项非常困难和费力的工作。需要开发替代传统视觉线截距调查的方法，特别是对于低密度地区。在这里，通过将适用于距离抽样的方法严格应用于被动声学监测（PAM），证明了通过被动声学监测（PAM）获得海豚密度估计值的前景。在视觉上同时跟踪港湾海豚的区域中部署了声学数据记录仪（T-POD）。通过标记-重捕方法估计了检测概率，其中视觉目击构成“标记”，同时声学检测构成“重捕”。由于可以为每个视觉观察分配一个距离，可以估计一个检测函数。T-POD 的有效检测半径范围为 22 至 104 米，具体取决于 T-POD 类型、T-POD 灵敏度、列车分类设置和快照持续时间。T-POD 密度估计值与同期为同一时期得出的视觉密度相对应。通过使用更多的数据记录仪，并根据系统设计进行定位，可以为更大的区域获得密度估计值。这为在视觉调查实际不可行的低密度地区提供了一种适合监测的方法，例如波罗的海濒危的港湾海豚种群。
