title: Density estimation of Yangtze finless porpoises using passive acoustic sensors and automated click train detection.
abstract: 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.
authors.affiliation: Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Kimura
authors.forename: Tomonari
authors.initials: T
authors.lastname: Akamatsu
authors.forename: Songhai
authors.initials: S
authors.lastname: Li
authors.forename: Shouyue
authors.initials: S
authors.lastname: Dong
authors.forename: Lijun
authors.initials: L
authors.lastname: Dong
authors.forename: Kexiong
authors.initials: K
authors.lastname: Wang
authors.forename: Ding
authors.initials: D
authors.lastname: Wang
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Arai
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D025041:Animal Migration; D000818:Animals; D002681:China; D008962:Models, Theoretical; D011156:Population Density; D019576:Porpoises / Q000502:physiology*; D015203:Reproducibility of Results; D012621:Seasons; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D014159:Transducers; D014828:Vocalization, Animal