Re-assessment of the Conservation Status of the Indo-Pacific Humpback Dolphin (Sousa chinensis) Using the IUCN Red List Criteria

Jefferson, Thomas A.; Smith, Brian D.

doi:10.1016/bs.amb.2015.04.002

“…The conservation status of the Indo-Pacific humpback dolphin has recently been re-assessed under the IUCN categories and criteria as Vulnerable [36]; previously listed as Near Threatened [33]. The regional status of local populations, however, can differ, sometime substantially [34].…”

Section: Discussionmentioning

confidence: 99%

“…The population numbers across the region are thought to be low, ranging from few tens to low few hundred [31,35,36], only exceptionally reaching over a thousand individuals [37]. Humpback dolphins inhabiting coastal waters of the Pearl River Estuary (PRE) are thought to number ca .…”

Section: Introductionmentioning

confidence: 99%

Indo-Pacific humpback dolphins (Sousa chinensis) in Hong Kong: Modelling demographic parameters with mark-recapture techniques

Chan

¹

,

Karczmarski

²

2017

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Indo-Pacific humpback dolphins (Sousa chinensis) inhabiting Hong Kong waters are thought to be among the world's most anthropogenically impacted coastal delphinids. We have conducted a 5-year (2010–2014) photo-ID study and performed the first in this region comprehensive mark-recapture analysis applying a suite of open population models and robust design models. Cormack-Jolly-Seber (CJS) models suggested a significant transient effect and seasonal variation in apparent survival probabilities as result of a fluid movement beyond the study area. Given the spatial restrictions of our study, limited by an administrative border, if emigration was to be considered negligible the estimated survival rate of adults was 0.980. Super-population estimates indicated that at least 368 dolphins used Hong Kong waters as part of their range. Closed robust design models suggested an influx of dolphins from winter to summer and increased site fidelity in summer; and outflux, although less prominent, during summer-winter intervals. Abundance estimates in summer (N = 144–231) were higher than that in winter (N = 87–111), corresponding to the availability of prey resources which in Hong Kong waters peaks during summer months. We point out that the current population monitoring strategy used by the Hong Kong authorities is ill-suited for a timely detection of a population change and should be revised.

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“…The Pearl River Estuary shelters the world's largest known population of Indo-Pacific humpback dolphins (Chen et al 2010;Jefferson & Smith 2016;Preen 2004), with an estimated population of 2637 (Coefficient of variation of 19% to 89%) (Chen et al 2010;Jefferson & Smith 2016). The general preference of this species for estuarine habitats and coastal and shallow water (<30 m depth) distribution make it susceptible to the impacts of human activity (Jefferson & Smith 2016).…”

Section: Passive Hearing By the Dolphinmentioning

confidence: 99%

Diversity of fish sound types in the Pearl River Estuary, China

Wang

¹

,

Nowacek

²

,

Akamatsu

³

et al. 2017

Preprint

0

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Background. Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Methods. Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. Results. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2600 Hz and a majority of the energy below 4000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1+1 and 1+N 10 might belong to big-snout croaker (Johnius macrorhynus), and 1+N 19 might be produced by Belanger's croaker (J. belangerii).Discussion. Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin (Sousa chinensis) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species.Additionally, prey and predator relationships can be observed when a database of species- AbstractBackground. Repetitive species-specific sound enables the identification of the presence and behavior of

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“…The Pearl River Estuary shelters the world's largest known population of Indo-Pacific humpback dolphins (Chen et al 2010;Jefferson & Smith 2016;Preen 2004), with an estimated population of 2637 (Coefficient of variation of 19% to 89%) (Chen et al 2010;Jefferson & Smith 2016). The general preference of this species for estuarine habitats and coastal and shallow water (<30 m depth) distribution make it susceptible to the impacts of human activity (Jefferson & Smith 2016).…”

Section: Passive Hearing By the Dolphinmentioning

confidence: 99%

“…The general preference of this species for estuarine habitats and coastal and shallow water (<30 m depth) distribution make it susceptible to the impacts of human activity (Jefferson & Smith 2016). The current conservation status of the Chinese white dolphin meets the IUCN Red List criteria for classification as Vulnerable; however, the conservation management in a majority of its distribution range is severely inadequate, and the humpback dolphin population in the Pearl River Estuary is declining by 2.5% annually (Karczmarski et al 2016).…”

Section: Passive Hearing By the Dolphinmentioning

confidence: 99%

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Background. Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Methods. Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. Results. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2600 Hz and a majority of the energy below 4000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1+1 and 1+N 10 might belong to big-snout croaker (Johnius macrorhynus), and 1+N 19 might be produced by Belanger's croaker (J. belangerii).Discussion. Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin (Sousa chinensis) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species.Additionally, prey and predator relationships can be observed when a database of species- AbstractBackground. Repetitive species-specific sound enables the identification of the presence and behavior of

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Re-assessment of the Conservation Status of the Indo-Pacific Humpback Dolphin (Sousa chinensis) Using the IUCN Red List Criteria

Cited by 110 publications

References 50 publications

Indo-Pacific humpback dolphins (Sousa chinensis) in Hong Kong: Modelling demographic parameters with mark-recapture techniques

Indo-Pacific humpback dolphins (Sousa chinensis) in Hong Kong: Modelling demographic parameters with mark-recapture techniques

Diversity of fish sound types in the Pearl River Estuary, China

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