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  • Comparative Studies. Non-European Languages/Literatures  (12)
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  • Comparative Studies. Non-European Languages/Literatures  (12)
RVK
  • 1
    Online Resource
    Online Resource
    Density estimation of Yangtze finless porpoises using passive acoustic sensors and automated click train detection
    Acoustical Society of America (ASA) ; 2010
    In:  The Journal of the Acoustical Society of America Vol. 128, No. 3 ( 2010-09-01), p. 1435-1445
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 128, No. 3 ( 2010-09-01), p. 1435-1445
    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/km2 during 94% of the period. These results suggest a potential gap and seasonal migration of the population in the bottleneck of Poyang Lake.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3442574
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2010
    detail.hit.zdb_id: 1461063-2
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  • 2
    Online Resource
    Online Resource
    Passive acoustic survey of Yangtze finless porpoises using a cargo ship as a moving platform
    Acoustical Society of America (ASA) ; 2011
    In:  The Journal of the Acoustical Society of America Vol. 130, No. 4 ( 2011-10-01), p. 2285-2292
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4 ( 2011-10-01), p. 2285-2292
    Abstract: In order to periodically investigate the population and distribution of the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) in its main distribution range in the Yangtze River, a passive acoustic system deployed on a cargo ship as a moving platform, rather than a dedicated research ship, was developed. A stereo acoustic event data-logger (A-tag) was installed on the cargo ship to passively detect phonating animals. In three surveys carried out in the Yangtze River from Wuhan to Shanghai, an average of 6059 clicks in each survey and 284 porpoises in total were acoustically detected along an 1100-km stretch. The animals were detected frequently in most of the survey range except two “gap sections” with 40 and 60 km lengths, respectively, where no animals were detected in all three surveys. Detected group sizes of the animals in each 120-s time window were not significantly different among the surveys, but the distribution pattern was different and suggested seasonal migration. The cargo ship based passive acoustic survey was effective in detecting phonating animals and can potentially monitor the distribution and population trend over time. Compared to surveys that used dedicated research ships, the present method is more cost effective.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3625257
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
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  • 3
    Online Resource
    Online Resource
    Finding baiji and freshwater finless porpoises in the Yangtze River, China
    Acoustical Society of America (ASA) ; 2011
    In:  The Journal of the Acoustical Society of America Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2459-2459
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2459-2459
    Abstract: A stereo passive acoustic event recorder (A-tag) has been applied for range-wide monitoring of baiji and finless porpoises in China. As the pilot study, two research vessels were operated in 1700 km historic habitat of both species from Yichang to Shanghai in 2006. There was no detection of baiji, but 204 and 199 porpoises were counted acoustically by two vessels, respectively. In order to investigate the population trends of cetaceans, periodical survey is necessary. We installed A-tag on the cargo ship, which was operated 1100 km in the river once every month. An average of 6059 clicks and 95 porpoises were acoustically detected in each survey. Detected group sizes of the animals in 120-s time window were not significantly different among the surveys, but the distribution pattern suggested seasonal migration. The animals were detected in most of the survey range except two gap sections with 40 and 60 km lengths, down from Wuhan and Nanjing cities, respectively, where no animals were detected in the first three surveys. Fragmentation of population by anthropological factors was concerned. The cargo ship based passive acoustic survey was effective to monitor the distribution and population trend over time.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3654878
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
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  • 4
    Online Resource
    Online Resource
    Passive acoustical counting of odontocetes using towed and stationed platforms.
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2548-2548
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2548-2548
    Abstract: Counting the number of animals is essential for monitoring and management of marine mammals. Autonomous stereo acoustic event recorder (A-tag) to identify each sound source enabled to count phonating odontocetes in the wild. Finless porpoises were surveyed by towed A-tags in 1100 km stretch of Yangtze River from Wuhan to Shanghai. The calculated detection probability using acoustic method was approximately twice that for visual detection. The difference in detection probabilities between the two methods was caused by the large number of single individuals that were missed by visual observers. However, acoustics tended to underestimate group size due to the limited resolution of sound source bearing angles. The detection performance regarding stationary acoustic monitoring of this species was also examined. Three stereo acoustic data loggers were placed at different locations near the confluence of Poyang Lake and the Yangtze River. Acoustic monitoring confirmed the low density bottle neck of the population between the lake and the river that was consistent with visual observations. The passive pulse event monitoring was proved to be a practical and useful alternative to visual observations, especially for long-term and range-wide monitoring.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783632
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
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  • 5
    Online Resource
    Online Resource
    Comparison of stationary acoustic monitoring and visual observation of finless porpoises
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 125, No. 1 ( 2009-01-01), p. 547-553
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 125, No. 1 ( 2009-01-01), p. 547-553
    Abstract: The detection performance regarding stationary acoustic monitoring of Yangtze finless porpoises Neophocaena phocaenoides asiaeorientalis was compared to visual observations. Three stereo acoustic data loggers (A-tag) were placed at different locations near the confluence of Poyang Lake and the Yangtze River, China. The presence and number of porpoises were determined acoustically and visually during each 1-min time bin. On average, porpoises were acoustically detected 81.7±9.7% of the entire effective observation time, while the presence of animals was confirmed visually 12.7±11.0% of the entire time. Acoustic monitoring indicated areas of high and low porpoise densities that were consistent with visual observations. The direction of porpoise movement was monitored using stereo beams, which agreed with visual observations at all monitoring locations. Acoustic and visual methods could determine group sizes up to five and ten individuals, respectively. While the acoustic monitoring method had the advantage of high detection probability, it tended to underestimate group size due to the limited resolution of sound source bearing angles. The stationary acoustic monitoring method proved to be a practical and useful alternative to visual observations, especially in areas of low porpoise density for long-term monitoring.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3021302
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
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  • 6
    Online Resource
    Online Resource
    Effects of water levels on distribution patterns of the Yangtze finless porpoises in Poyang and Dongting Lakes, China
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3361-3361
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3361-3361
    Abstract: Two large freshwater lakes in China (Poyang and Dongting Lakes) are crucial habitats of the Yangtze finless porpoises. The lakes are confronted with threatens from low water levels. For evaluating possible impacts of low water levels on the porpoises in the lakes, the distribution patterns of the animals in the lakes were monitored in different seasons by using a boat-towing A-tag array from 2009 through 2011. The survey routes were almost same among different seasons. The acoustical detection number (i.e. encounter number) of porpoise in every 3-km section was calculated by counting the bearing angle traces of the sonar sources recorded by the array. The numbers in the same section were compared between high and low water level periods. Results indicated that porpoises appeared to congregate in deep water areas in low water level periods, while they tended to disperse toward the near shore waters in high water level periods. The results suggest concentration of individuals during low water level period. The variations of distribution patterns in different water level periods remind us that protection efforts should be focused on different areas according to the changes of water levels in different seasons.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4708665
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
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  • 7
    Online Resource
    Online Resource
    Acoustic capture-recapture method for towed acoustic surveys of echolocating porpoises
    Acoustical Society of America (ASA) ; 2014
    In:  The Journal of the Acoustical Society of America Vol. 135, No. 6 ( 2014-06-01), p. 3364-3370
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 135, No. 6 ( 2014-06-01), p. 3364-3370
    Abstract: Passive acoustic monitoring for cetaceans mainly employ fixed-location methods or point transect samplings; an acoustic survey from a moving platform to conduct line transects is less common. In this study, acoustic capture–recapture by combining a double-observer method with line transect sampling was performed to observe Yangtze finless porpoises. Two acoustic devices were towed with the distance between them varying 0.5 to 89.5 m. The conditional probabilities that both devices would detect the porpoises within the same time window were calculated. In a 1-s time window, it became smaller as the distance between the devices increased, approaching zero when the distance between them was more than 50 m. It was considered that the devices with less than 50 m distance detected the same signals from the same animals, which means the identical detection. When the distance between them is too great, the recapture rate is reduced and the incidence of false matching may increase. Thus, a separation distance of around 50 m between two devices in acoustic capture–recapture of Yangtze finless porpoises was recommended. Note that the performance of the double detections can change depending on the particular device used and on animal behaviors such as vocalizing interval, ship avoidance.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4875710
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2014
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  • 8
    Online Resource
    Online Resource
    Distribution pattern of finless porpoises at the junction of the Yangtze River and Poyang Lake observed by towed passive acoustic device
    Acoustical Society of America (ASA) ; 2011
    In:  The Journal of the Acoustical Society of America Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2460-2460
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2460-2460
    Abstract: The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is an endangered freshwater porpoise subspecies unique to the Yangtze River basin. Without immediate conservation measures, it could soon become extinct, just as the Yangtze River dolphin (baiji, Lipotes vexillifer). We report seasonal change in the local distribution of the porpoises living in the conjunction area of the middle reaches of the Yangtze River, side streams, and appended Poyang Lake. A towed stereo acoustic data-logger, A-tag, was used to detect echolocation signals and sound source bearing angles. The independent sound source directions provided the number of animals present, not just the number of sounds. Passive acoustic surveys were performed regularly from May 2007 to August 2010. The water level was highest in August (summer) and lowest in February (winter) and at mid-level in May (spring) and November (autumn). The average number of porpoises detected in 11 surveys conducted in different seasons varied from 0.53 to 1.26 individuals per km. No significant trend of reducing number of porpoises was detected during 3-y monitoring. The distribution of the porpoises was seasonally site-specific. In May and August, the animals were detected more often at river junctions than in the lake, but vice versa from November to February.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3654880
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
    detail.hit.zdb_id: 1461063-2
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  • 9
    Online Resource
    Online Resource
    Simultaneous production of low- and high-frequency sounds by neonatal finless porpoises
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 124, No. 2 ( 2008-08-01), p. 716-718
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 124, No. 2 ( 2008-08-01), p. 716-718
    Abstract: Phocoenids are generally considered to be nonwhistling species that produce only high-frequency pulsed sounds. Here our results show that neonatal finless porpoises (Neophocaena phocaenoides) frequently produce clear low-frequency (2–3kHz) pulsed signals, without distinct high-frequency energy, just after birth and can produce both low- (2–3kHz) and high-frequency ( & gt;100kHz) pulsed signals simultaneously until about 20days postnatal. The results indicate that low-frequency signals of neonatal finless porpoises are not an early form of high-frequency signals and suggest that low- and high-frequency signals may be produced by different sound production mechanisms.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2945152
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
    detail.hit.zdb_id: 1461063-2
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  • 10
    Online Resource
    Online Resource
    Acoustical estimation of bubble concentration in seawater.
    Acoustical Society of America (ASA) ; 1992
    In:  The Journal of the Acoustical Society of America Vol. 91, No. 4_Supplement ( 1992-04-01), p. 2468-2468
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 91, No. 4_Supplement ( 1992-04-01), p. 2468-2468
    Abstract: The acoustic backscattering characteristics of seawater were studied by the method of local acoustic measurements within a small volume to infer the bubble concentration in seawater. It was found that the scattering intensities were increased with wind speed, especially to the forming of white caps on the sea surface. In some cases the intensities were related to the sea state of earlier days. Under low wind speeds, the peak of the scattering spectra shifted toward high frequencies and its spectra became narrower. In high winds the spectra reversed its tendencies. The spectra in deep water at high winds had a similar shape as in shallower depth at light winds. The measured data can be fitted by the theoretical spectra constructed on the principles of energy superposition under the assumption of Poisson distribution of bubble number in different sizes per unit of volume. The dependence of bubble concentration on depth can be obtained by the fittings. The concentrations exponentially decrease with the depth. The decaying constant is 8 (1/m) and is independent of wind speed. A definition of effective thickness of the bubble layer near the sea surface was given by a critical density of 10−3 (1/cm3), ΔR=1 μm. The inferred thickness is dependent on the wind speed.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.403026
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1992
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