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Tomonari Akamatsu Kiyomi Nakamura Ryo Kawabe Seishiro Furukawa Hiromi Murata Akihiro Kawakubo Masayuki Komaba 《Marine Biology》2010,157(8):1879-1887
A number of local populations of finless porpoises (Neophocaena phocaenoides) are widely distributed throughout the warm coastal waters of Asia. The Omura Bay population, consisting of approximately
300 individuals, is the smallest of five populations inhabiting Japanese waters. It is a relatively new population that established
after the global warming that took place approximately 9000 years ago. To observe whether these porpoises appear in the major
corridor to the ocean from Omura Bay, we used acoustic monitoring to record occurrences of finless porpoises from November
2007 to May 2009. A stereo acoustic event recorder recorded the intensity and the sound source direction of biosonar signals,
providing independent traces of sound sources corresponding to each detected animal. A total of 226 individuals were detected
over the 1.5-year monitoring period, of which 76% occurred at night and 73% occurred during March and April. We compared the
presence of porpoises to the Japanese anchovy catch in Omura Bay and the Hario Strait over the same period. Results suggested
that possible reductions in anchovy resources in the bay could attract porpoises to the outside of their normal habitat. In
total, 70% of the porpoise recordings took place when the tidal current was moving out of Omura Bay. Porpoises might follow
the prey that are transported out of the bay due to the strong outbound current. The finless porpoises confined to the bay
might extend their swimming area if prey is available. 相似文献