Status and Distribution of the Gangetic Dolphin, Platanista Gangetica Gangetica (Roxburgh, 1801) In River Buriganga During 2003-2004 and Its Conservation

Abstract

Studies on the population status, distribution and conservation issues of the Gangetic dolphin Platanista gangetica gangetica were undertaken in the river Buriganga from November 2003 to November 2004. A total of 29 sightings with the highest of five sightings and a best-high-low estimate of 9-11-7 individuals were recorded in November 2004, while in the months of August and October no dolphin was observed. The mean density was 0.25 dolphin/km and the highest encounter rate was 0.29 sightings/km. Of the total sightings, 41.38% were in the groups of more than one individuals. Of the observed dolphins, 71.43% were adults,16.66% maturing and 11.9% young. The dolphins were found in 15 locations with both single as well as multiple sightings. Main threat to the dolphins was found to be pollution followed by traffic load and dredging activities. DOI: http://dx.doi.org/10.3329/bjz.v40i1.12890 Bangladesh J. Zool. 40(1): 21-31, 2012

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

“…Preliminary survey confirmed about the presence and absence areas of dolphins in that section of the river. This was also supported by Alam and Sarker (2012). The absence of dolphin in the area due to, may be, the human population along the river bank seemed to exert immense pressure from Babu bazzar bridge to Kholamora ghat (appox.…”

“…The survey design principles followed those used in previous studies conducted by different authors (Shrestha 1989;Smith et al 1994, Chaudhary 2007and Alam and Sarker 2012. A boat based survey method and distance sampling were used to obtain density and encounter rate of dolphins.…”

“…Ganges River Dolphins are present in the Buriganga River, which is mostly a polluted river in Bangladesh with huge industrial, household discharges, encroachments and vehicle loads and sometimes regarded as ecologically dead (IWM 2004, Ahmed and Reazuddin 2000, Smith et al 2008, Alam and Sarker 2012. Over the last decade, this pressure on the ecosystem increased in many ways from increasing numbers of industries to vehicles carrying both humans and goods (Islam 2011).…”

“…Modification of river flows (especially from dams), alterations in sediment and nutrient fluxes, habitat destruction, river pollution from urbanization and agriculture, boat traffic, illegal intentional hunting, and over exploitative fisheries are known to threaten the habitats of this species in South Asia (Payne and Temple 1996, Bannerjee 1999, Dudgeon 2000a, 2000bManel et al 2000, Gergel et al 2002. In Bangladesh, however, habitat fragmentation by barrages, excessive water abstraction and river pollution are the major threats for this species , Sinha 2006, and Alam and Sarker 2012. Hence, they are classified as an endangered species in the country (IUCN Bangladesh 2000) and are placed in the First Schedule of Bangladesh Wildlife (Preservation & Security) Acts, 2012.…”

“…conducted a short visit to the Buriganga River to survey the status of the Ganges River Dolphins, where they observed only one group of two to three individuals. Later, Alam and Sarker (2012) conducted a month-wise yearlong study during 2003-2004 where they found a population ranging from none to 9 in different months in full stretch of this river (Basilla to Hariharpara in Fatulla). Since then, no study has been reported and the present study was conducted from Babu Bazar Bridge to Amin Bazar Bridgeto observe the status of dolphin population in the present condition of river Buriganga.…”