Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan.
J Acoust Soc Am. 2010 Sep;128(3):1435-45. doi: 10.1121/1.3442574.
A method is presented to estimate the density of finless porpoises using stationed passive acoustic monitoring. The number of click trains detected by stereo acoustic data loggers (A-tag) was converted to an estimate of the density of porpoises. First, an automated off-line filter was developed to detect a click train among noise, and the detection and false-alarm rates were calculated. Second, a density estimation model was proposed. The cue-production rate was measured by biologging experiments. The probability of detecting a cue and the area size were calculated from the source level, beam patterns, and a sound-propagation model. The effect of group size on the cue-detection rate was examined. Third, the proposed model was applied to estimate the density of finless porpoises at four locations from the Yangtze River to the inside of Poyang Lake. The estimated mean density of porpoises in a day decreased from the main stream to the lake. Long-term monitoring during 466 days from June 2007 to May 2009 showed variation in the density 0-4.79. However, the density was fewer than 1 porpoise/km(2) during 94% of the period. These results suggest a potential gap and seasonal migration of the population in the bottleneck of Poyang Lake.
本文提出了一种利用固定被动声学监测估算江豚种群密度的方法。立体声学数据记录仪（A-tag）检测到的click 脉冲串数量被转换为江豚密度的估计值。首先，开发了一种自动的离线滤波器来检测噪声中的 click 脉冲串，并计算了检测率和误报率。其次，提出了一种密度估计模型。通过生物标记实验测量了 cue 的产生率。根据声源级、波束模式和声传播模型，计算了 cue 的检测概率和面积大小。检验了群体大小对 cue 检测率的影响。最后，将提出的模型应用于从长江到鄱阳湖内部的四个地点估算江豚的种群密度。估算的江豚日平均密度从主流区向湖区逐渐降低。2007 年 6 月至 2009 年 5 月期间进行的 466 天的长期监测显示，密度在 0-4.79 之间变化。然而，在 94%的时间里，密度都少于 1 头/公里²。这些结果表明，鄱阳湖瓶颈处的种群存在潜在的缺口和季节性迁移。
