Introduction of an advanced census method using fusion of acoustic and visual census of the Ganges river dolphins (Platanista gangetica) inhabiting a long tract of the Ganges river system

An advanced and accurate census methodology that fuses acoustic and visual census of the freshwater dolphins has been successfully introduced for the Ganges river dolphins that inhabit and migrate in a long tract of the Ganges river system. In order to conduct an accurate census of the dolphins, an acoustic array system with provision to display the dolphin's real-time direction data on a GUI (Graphical User Interface), i.e. the RAPID-Array (Real-time Acoustic Passive In-situ Dolphin tracking Array) was developed in 2014. Targeting 10–13 Ganges river dolphins (adults, juveniles and calves) that were estimated to inhabit a 7-km stretch, i.e. a part of the entire 200km riverstretch from Bhitora to Allahabad in India, using the array, the initial census using fusion of acoustic and visual census was conducted for one day on 24 November 2015. Based on the data acquired during the census, an estimate of the number of the dolphins was quickly made at the site. The effectiveness of the proposed method was demonstrated for carrying out the census in a long tract of the entire habitat.