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