ABUNDANCE OF IRRAWADDY DOLPHINS (<i>ORCAELLA BREVIROSTRIS</i>) AND GANGES RIVER DOLPHINS (<i>PLATANISTA GANGETICA GANGETICA</i>) ESTIMATED USING CONCURRENT COUNTS MADE BY INDEPENDENT TEAMS IN WATERWAYS OF THE SUNDARBANS MANGROVE FOREST IN BANGLADESH

Smith, Brian D.; Braulik, Gill; Strindberg, Samantha; Ahmed, Benazir; Mansur, Rubaiyat M.

doi:10.1111/j.1748-7692.2006.00041.x

Cited by 69 publications

(77 citation statements)

References 20 publications

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“…Habitat characteristics included measures of water depth using a depth finder (Leatherwood et al 2000, Akbar et al 2004, Smith et al 2008, river width using a range finder (Smith et al 2006(Smith et al , 2008 and habitat structure of the river. While measuring river depth, the boat remained midway between the banks in order to standardize these values.…”

Section: Dolphin Surveysmentioning

confidence: 99%

“…Bardia National Park, Koshi Tappu Wildlife Reserve, and Chitwan National Park), their numbers and distribution have still declined significantly since monitoring began (Shrestha 1989, Smith 1993, Smith et al 2006, WWF-Nepal 2006, with the species vanishing completely from some rivers (i.e. present in 4 rivers in the 1980s, now found only in 3; Leatherwood & Reeves 1994).…”

Section: Introductionmentioning

confidence: 99%

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The Endangered Ganges River dolphin Platanista gangetica gangetica in Nepal: abundance, habitat and conservation threats

Paudel¹,

Pal²,

Cove³

et al. 2015

Endang. Species. Res.

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Conservation of the last remaining Ganges River dolphins Platanista gangetica gangetica in Nepal will require robust population estimates and better information on suitable habitat characteristics. To gain a better understanding of these parameters, we conducted boatbased surveys in the 3 major river systems (Karnali, Sapta Koshi, and Narayani) of Nepal. We recorded covariates at high spatial resolution and utilized these data to inform occurrence and abundance models. We allowed for detection bias by applying occupancy and N-mixture models that account for imperfect and heterogeneous detection. Occupancy results indicate that dolphin site use varies among the different river systems, across 2 seasons, and increases with river depth. River effects received nearly 100% of the model support and had the strongest influence on dolphin occurrence and abundance. The seasonal influence on dolphin occurrence in the systems (Σω i = 0.997) revealed that occupancy probabilities were heightened during the pre-monsoon season. Deep pool habitat was also identified as a predictor of dolphin habitat use, which accounted for 41.02% of all dolphin sightings occurring in this habitat. Although estimates vary depending on season, we estimate that there are between 37 and 42 (95% CI: 28 to 52) Ganges River dolphins distributed in the rivers of Nepal. Results suggest that seasonality and each specific river affect dolphins and their habitat in Nepal; we strongly recommend site and season-specific conservation actions. Further research on the integration of additional and alternative abundance techniques, behavioral studies, and pursuit of a conservation genetics approach are all important steps in the management of this endangered species.

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Section: Dolphin Surveysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Endangered Ganges River dolphin Platanista gangetica gangetica in Nepal: abundance, habitat and conservation threats

Paudel¹,

Pal²,

Cove³

et al. 2015

Endang. Species. Res.

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“…The photo-identification surveys were realized in Bangladesh, Malaysia andIndia between 2004 and (Table 1) following the methods described in Smith et al (2006), Minton et al (2011Minton et al ( , 2013 and Sutaria & Marsh (2011). Dolphins were photo graph ed with digital SLR cameras equipped with 70 to 400 mm zoom lenses, at distances ranging from a few to several hundreds of meters.…”

Section: Photo-identification Surveys and Study Areasmentioning

confidence: 99%

Cutaneous nodules in Irrawaddy dolphins: an emerging disease in vulnerable populations

Bressem¹,

Minton²,

Sutaria³

et al. 2014

Dis. Aquat. Org.

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The presence of cutaneous nodules is reported in vulnerable populations of Irrawaddy dolphins Orcaella brevirostris from Malaysia (Kuching, Bintulu-Similajau, KinabatanganSegama and Penang Island), India (Chilika Lagoon) and Bangladesh (Sundarbans). Approximately 5700 images taken for photo-identification studies in 2004 to 2013 were examined for skin disorders. Nodules were detected in 6 populations. They appeared as circumscribed elevations of the skin and varied in size from 2 to > 30 mm, were sparse or numerous and occurred on all visible body areas. In 8 photo-identified (PI) dolphins from India and Malaysia, the lesions remained stable (N = 2) or progressed (N = 6) over months but did not regress. The 2 most severely affected individuals were seen in Kuching and the Chilika Lagoon. Their fate is unknown. Cutaneous nodules were sampled in a female that died in a gillnet in Kuching in 2012. Histologically, the lesions consisted of thick collagen bundles covered by a moderately hyperplasic epithelium and were diagnosed as fibropapillomas. Whether the nodules observed in the other O. brevirostris were also fibropapillomas remains to be investigated. Disease prevalence ranged from 2.2% (N = 46; Bintulu-Similajau) to 13.9% (N = 72; Chilika) in 4 populations from Malaysia and India. It was not significantly different in 3 study areas in eastern Malaysia. In Chilika, prevalence was significantly higher (p = 0. well et al. 1975, Kiszka et al. 2009, Reif et al. 2009, Van Bressem et al. 2009b. In some small communities of inshore and estuarine populations, these pathologies are highly prevalent, may progress to cover extensive body areas and have been associated with the death or disappearance of severely affected individuals, including calves (Simões-Lopes et al. 1993, Van Bressem et al. 2007a, Kiszka et al. 2009, Daura-Jorge & Simões-Lopes 2011. However, their impact on the long-term viability of affected communities is still vastly unknown. The fungi Lacazia loboi, Fusarium spp., Paracoccidioides brasiliensis and Trichophyton spp. have been identified as the aetiological agents of some nodular disorders (Caldwell et al. 1975, Frasca et al. 1996, Van Bressem et al. 2007a, Esperón et al. 2012, Tanaka et al. 2012). Immune dysfunction is also known to play a role in the pathogenesis of L. loboi disease in coastal common bottlenose dolphins Tursiops truncatus from Florida, USA (Reif et al. 2009, Murdoch et al. 2010.Irrawaddy dolphins Orcaella brevirostris occur in large rivers and marine appended lakes in South Asia, as well as in the coastal waters of the Indo-Pacific Ocean (Smith 2009). Estuarine and nearshore populations are distributed in tropical and subtropical waters of the Indo-Pacific Ocean, from eastern India to the Philippines (Dolar et al. 2002, Minton et al. 2011. Riverine populations have been documented in 3 major river systems: the Mahakam (Indonesia), the Ayeyarwady (Myanmar) and the Mekong (Laos, Cambodia and Vietnam) (Smith 2009). Their habitat preference exposes them to multiple anthropog...

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“…This variation may be due to the difference in sampling design and area. However, in Bangladesh, 55 sightings were recorded from Sundarbans Delta area in March 2002 (Smith et al 2006) and 25 sightings were recorded from Jamuna River in just three days in April, 1996 . Best-high-low estimate of 25-30-21 individuals were recorded in the Karnali River, Nepal (Smith 1993).…”

Section: Resultsmentioning

confidence: 99%

Status of ganges dolphin, Platanista gangetica gangetica (Roxburgh, 1801) in the river Buriganga, Dhaka

Alam¹,

Hossain²,

Baki³

et al. 2015

Bangladesh J. Zool.

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Population abundance and density of the Ganges River Dolphin Platanista gangetica gangetica (Roxburgh, 1801) was studied in the Buriganga River from December 2012 to November 2013.The survey was conducted twice a month. The dolphins were counted directly and applied in transect length of 10.5 km within 15 km stretches of the river. A total of 34 sightings of dolphins were recorded both in individuals and groups. We encountered the dolphins at the rate of 0.48 dolphins per km in the Buriganga River. Highest best-high-low estimate of 12-14-10 individuals were recorded in November 2013. The mean density was 0.38 (SD ±0.37) dolphins/km² with the highest density of dolphin observed also in the month of November, which was 1.14 dolphin/km². Pollution and water traffic were observed to be the major threats to the dolphins.

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ABUNDANCE OF IRRAWADDY DOLPHINS (ORCAELLA BREVIROSTRIS) AND GANGES RIVER DOLPHINS (PLATANISTA GANGETICA GANGETICA) ESTIMATED USING CONCURRENT COUNTS MADE BY INDEPENDENT TEAMS IN WATERWAYS OF THE SUNDARBANS MANGROVE FOREST IN BANGLADESH

Cited by 69 publications

References 20 publications

The Endangered Ganges River dolphin Platanista gangetica gangetica in Nepal: abundance, habitat and conservation threats

The Endangered Ganges River dolphin Platanista gangetica gangetica in Nepal: abundance, habitat and conservation threats

Cutaneous nodules in Irrawaddy dolphins: an emerging disease in vulnerable populations

Status of ganges dolphin, Platanista gangetica gangetica (Roxburgh, 1801) in the river Buriganga, Dhaka

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