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Population status and conservation of the ganges river dolphin (platanista gangetica gangetica) in the indian subcontinent

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Herein we discuss the Ganges River dolphin (Platanista gangetica gangetica or susu) which inhabits the Ganges-Brahmaputra-Meghna and Sangu-Karnaphuli river systems of India, Nepal and Bangladesh. The chapter begins with a discussion of the origin, evolution, and phylogeny of the Ganges River dolphin as well as river dolphins in general. Also included are descriptions of past and present distribution patterns of the Ganges River Dolphin along with its anatomical structure, including primitive characters and morphological characters of interest. In the second section of the chapter we elaborate on Ganges River dolphin population surveys we conducted within a 500 km section of the Ganges River in the state of Bihar during 2005 to 2007. Both upstream and downstream surveys were performed three times per year. A significantly greater number of Ganges dolphins were observed per kilometer upstream compared to downstream surveys (1.28 versus 1.0 respectively) and the mean number of dolphins observed per upstream survey ranged from 559 to 808. Our results also support spatial and temporal variation of the Ganges dolphin population with for example a greater number of animals in confluence areas. These survey results are similar to those obtained from other Ganges River surveys that used similar methods. The chapter concludes with a discussion on the Ganges River dolphin's conservation status and major threats to its existence. Direct catch, incidental catch, pollution, and habitat degradation are all serious threats.
... The highest encounter rates of Ganges River Dolphins have been observed in the Ganges main stem between Patna and Rajmahal (2-2.5 dolphins/linear km along the river) (Sinha et al. , 2010Kannan 2014, Kelkar et al. 2010). Within this stretch, encounter rates were particularly high from Sultanganj to Rajmahal (2.5-3 dolphins/km), peaking downstream of Kahalgaon and Maniharighat (3-3.2 dolphins/km), based on surveys carried out from 2000 to 2015 . ...
... Major threats to Ganges River Dolphins include 1) flow regulation and habitat fragmentation by water development projects (dams, barrages, canals, and embankment construction projects), 2) mortality from entanglement in fishing nets, 3) targeted hunting of dolphins for oil and flesh, 4) river pollution, and 5) disturbance from human activities related to boat traffic, underwater noise, and shoreline/riverfront development (Smith and Smith 1998, Sinha et al. 2010, Sinha and Kannan 2014, Dey et al. 2018, Braulik and Smith 2019, Kelkar and Dey 2020. Other emerging threats include river bottom sediment dredging, saline ingress from sea level rise (in the Sundarbans Delta), and the impacts of climate change on basin-scale hydrological dynamics. ...
... As fishers are usually aware that hunting is illegal, such activities are almost never reported for fear of penalties and fines, and no reliable numbers are available. Hunting might still occur occasionally in the middle Ganges near Patna, India , Sinha 2002, Sinha et al. 2010, the Kalni-Kushiyara River of Bangladesh (Smith et al. 1998), the Gandak River, Bihar (Dey, S., pers. obs.), the Ganges and Hooghly Rivers in West Bengal (Qureshi et al. 2018, Samad 2021, and the upper reaches of the Brahmaputra River in Assam, India (Mohan et al. 1997). ...
... Energy consumption that results from the adaptations to heterobalance in an organism will lead to the decline of various functions (Davis & Schreck, 1997). The studies of Ganges river dolphin (Platanista gangetica) have suggested that the dolphins take advantage of lower stream velocities at river junctions, inside bends and in countercurrent eddies to conserve energy (Smith, 1993;Sinha, Verma & Singh, 2010). Hence, the preference of the YFPs for the nonshipping branch of the river is likely to represent a strategy to avoid underwater noise that can threaten their survival. ...
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• Yangtze finless porpoise (YFP) is Critically Endangered, It relies on its biological sonar sensing system for important life activities. The rapid development of the Yangtze valley has brought busy shipping, which has resulted in increased noise. • Two locations on the shipping channel and non‐shipping branch were selected. Passive acoustic monitoring was used to record the biosonar signals of porpoises and underwater noise. The number of click trains, echolocation encounters, buzzes and buzz ratios were counted and the root mean square sound pressure level of noise was calculated in five diel phases. • A non‐parametric test was used to analyse the differences among different phases and between different locations. The aim of the study was to detect the spatial and temporal variations in the biosonar activity of YFPs and underwater noise between non‐shipping and shipping channels, and to provide scientific advice for YFP conservation. • Significant spatial and temporal patterns were observed both in biosonar activity and noise. Average biosonar activity, including click trains, buzzes, buzz ratio and echolocation encounters, was higher in the non‐shipping channel than in the shipping channel, whereas the noise level was higher in the shipping channel than in the non‐shipping channel. • In the non‐shipping channel, the buzz numbers and buzz ratios, indicators of porpoise feeding activity, were higher at night than during the day while the noise level was higher during the day than at night. • These findings may be associated with the noise avoidance strategies of YFPs to adapt to the busy shipping on the Yangtze River. Maintaining the non‐shipping status of some branches of the Yangtze River can provide more shelters for the YFPs. Strengthening the measures for banning navigation at night or reducing the vessel speed at night throughout the entire year would improve the YFPs’ feeding success.
... Their first known appearance in the Miocene marks a time when members of most other crown odontocete lineages were extremely rare. Presently, the family is restricted to the genus Platanista Wagler, 1830, freshwater inhabitants with relict distributions in the Ganges and Brahmaputra river systems of south Asia (Sinha et al., 2010). Up until quite recently, they were central constituents of the Platanistoidea, an early evolutionary radiation of small-to medium-size dolphin-like animals that diversified during the Oligocene and early part of the Miocene (Barnes et al., 2010;Tanaka and Fordyce, 2015). ...
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The Ganges river dolphin, Platanista gangetica is a freshwater dolphin, commonly known as susu and is distributed in Ganga-Brahamputra-Meghna and Karnaphuli river systems in India, Nepal and Bangladesh. It is found in the freshwater and estuarine zones but never enters sea. It is one of the four freshwater cetacean species found in the world. Over-exploitation and habitat destruction are the major factors for rapid decline in dolphin population. Construction of Farakka Barrage in mid-1970s has genetically isolated the susu population. For the first time dolphin count in Feeder Canal, Bhagirathi and Hooghly rivers, and downstream Farakka Barrage was undertaken in low water season of 1995. Actual count as suggested by Cetacean Specialist Group of IUCN/SSC was done between Farakka and Calcutta. A best count of 152 dolphins was obtained. Habitat preferences of susus and impact of pollution and other human activities were studied. Based on the study, current status of dolphin in Bhagirathi and Hooghly rivers has been discussed and conservation measures suggested.
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