AN INTRODUCTION TO RIVER DOLPHIN SPECIES - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 19

Their distribution is non-continuous within the Ganges-Brahmaputra-Meghna and
Karnaphuli-Sangu River systems in India, Bangladesh and Nepal (Sinha et al., 2000) and
have mostly been observed as solitary animals with surveyed densities of 0.76 to 1.36
dolphins per km (Smith et al., 2001). During the monsoon season they inhabit confluences
and complex habitat areas while in the dry season they remain in river channels and deep
tributary pools. Total estimated numbers for Ganges River dolphins are from 1,000 to 3,000,
significantly less than the estimated 4,000-5,000 in 1986 (Mohan, 1989).
Figure 8. Some images of Platanista gangetica gangetica (copyright Dr. Singh).
Human developments, severe pollution, over fishing, habitat degradation, alteration of
sedimentation, and hydrologic changes, all pose serious threats to the Ganges River dolphin
(Dudgeon, 2000; Sinha, 2006). Elevated heavy metal and Butyltin compound concentrations,
direct hunting (Sinha, 2002), and accidental bycatch are additional threats (Kannan et al.,
1993; Kannan et al., 1997). Moreover, barrages and dams have confined and isolated Ganges
River dolphins as well as reduced water flow (Mohan, 1989; Reeves & Leatherwood, 1994).