Development of an automatic discrimination method of the bio-sonar clicks of Irrawaddy dolphin (Orcaella brevirostris) from various types of boat noises

Long-term acoustic monitoring of the Irrawaddy dolphins using a PAM (passive acoustic monitoring) system has been conducted since 2011 at the stationary observatory in the middle-river district of the Mahakam river in Borneo. For statistical data analysis using a large amount of data of both Irrawaddy dolphin clicks and a variety of boat noise pulses acquired by the long duration monitoring, applying the click train based ICI (Inter-click Interval) change rate and CF (Centroid Frequency) / frequency component analysis, a new integrated automatic discrimination method of the dolphin clicks from various types of boat noises pulses was developed. For evaluation of the proposed method, the analysis results using the method were compared with the manual analysis results. Similar trends were shown in both analysis results of the daily/monthly dolphin's appearance frequency (Ad), and the differences of the Ad values were within an acceptable range. It can be said that the proposed method could capture the overall trends of the dolphin's appearance frequency in a long-term span. From this, the effectiveness of the proposed method was demonstrated well.