Acoustic survey of baiji in their historic habitat of the Yangtze River

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Distribution of endangered freshwater cetaceans was revealed by cutting-edge underwater acoustic technology. Macro scale distribution of cetaceans in the entire Yangtze River and micro scale distribution in a high density area were provided. Historic habitat of baiji and Yangtze finless porpoises were surveyed from Yichang, nearby three gorges dam, to Shanghai, using towing type underwater microphone. Results suggested extinction of baiji and quick reduction of finless porpoises. Log-term stationary acoustic observation had been conducted at the hot spot, high density waters, in the middle of the Yangtze River. Using the outcomes, a model to convert acoustic detection rate to real density of existing number of animals was proposed. Extensive towing acoustic survey was conducted in the same section and provided detail map of distribution of porpoises. In the last year, periodical automatic surveys using a cargo ship as a platform of the acoustic device were conducted from Wuhan to Shanghai, 1100km stretch of the middle and lower reached of the Yanzgter River. This method is cost effective and useful for range-wide monitoring of small odontocetes, which has been applied worldwide in these days.