Widespread passive acoustic detection of Yangtze finless porpoise using miniature stereo acoustic data-loggers: A review

Abstract

Data on distribution, abundance, ecology, and behavior are essential for conservation and management of endangered animals in the wild. Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is an endangered small odontocete species, living exclusively in the Yangtze River and its connecting Poyang and Dongting Lakes. Frequent production of high-frequency bio-sonar signals allows the animal to be detectable using passive acoustic methods. Recently, a stereo acoustic event data-logger (A-tag) has been used extensively to detect the animal by using both fixed and mobile platforms. The passive acoustic monitoring methods were not only successful in detecting the presence of animals, but also in counting, localizing, and tracking phonating individuals. Underwater behavior observed acoustically helped to assess possible effects of vessels on the animals during acoustic surveys.

Passive acoustic survey of Yangtze finless porpoises using a cargo ship as a moving platform

“…Each click train of biosonar signals produced by the Yangtze finless porpoises usually contains five to several hundred clicks with regular intensities and interclick intervals (ICI) of approximately 20-70 ms (Akamatsu et al, 1998;Akamatsu et al, 2008;Li et al, 2010). Noise recorded by the A-tag had randomly changing intensities and interclick intervals, which is quite different from the porpoise clicks.…”

“…Any irregular successive clicks greater than twice or less than half the previous interclick intervals were also considered to be noises and excluded (Akamatsu et al, 1998(Akamatsu et al, , 2001. In addition, the sound source of the five pulses should come from same direction to make sure all pulses originated from a single sound source (reviewed in Li et al, 2010).…”

“…As a complement or potential substitute for the traditional visual survey, acoustic monitoring was demonstrated to be a powerful method for detecting mysticetes (McDonald, 2006) and odontocetes Carstensen et al, 2006;Akamatsu et al, 2008;Li et al, 2010). Passive acoustic methods that detect animal sounds were widely used for cetacean detection (McGregor et al, 1997;McDonald and Fox, 1999;Oswald et al, 2003;Wang et al, 2005;Mellinger et al, 2007;Li et al, 2010).…”

“…Passive acoustic methods that detect animal sounds were widely used for cetacean detection (McGregor et al, 1997;McDonald and Fox, 1999;Oswald et al, 2003;Wang et al, 2005;Mellinger et al, 2007;Li et al, 2010). The Yangtze finless porpoise, as a small odontocete, possesses a highly developed sound production system likely used in navigation, orientation, and prey capture (Au, 1993;Akamatsu et al, 2005;Verfuss et al, 2009).…”

“…These narrow-band ultrasonic pulses are quite different from background noise and other artificial sources, and therefore can be easily detected acoustically. Recently, passive acoustic surveys have been widely utilized for porpoise monitoring in the Yangtze River system using either mobile or fixed survey platforms (reviewed by Li et al, 2010). A stereo acoustic event data-logger (A-tag) was demonstrated to be an effective instrument for picking up click phonation events of the porpoises and therefore detecting the presence of the animals.…”