Introduction of balloon census for acoustic and visual census of the Ganges river dolphins (Platanista gangetica) that inhabit in a long tract of the Ganges river system

For increasing the accuracy of quantitative analysis of the census data of Ganges river dolphins that inhabit and migrate over a long tract of the river stretches in the Ganges river system, a balloon with a video camera system was developed for supporting the census using fusion of acoustic and visual census which was previously proposed by authors [1]. The developed balloon with the camera system was tested on the ground in October 2016. Followed by the test, targeting the groups of Ganges river dolphin (adults, juveniles and calves) that were estimated to inhabit a 24-km stretch, i.e. a part of the entire 200km river-stretch from Bhitora to Allahabad in India, the initial census using the balloon with a video camera system and fusion of acoustic and visual census has been conducted for three days from 21 to 23 November 2016. Even though the coverage range was limited, its potential use for supporting the fusion census for the acoustic and visual census was well demonstrated from the results of the initial balloon census.