KANPUR: As many as 19 dolphins have been sighted in a major stretch of Ganga in Fatehpur district.The dolphin census, a collaborative effort by experts of IIT-Delhi, University of Tokyo (Japan) and the Society for Conservation of Nature was done to find out the exact number of the endangered animal. The experts are taking the help of sonar monitoring systems and camera-fitted balloons in 35 km stretch of Ganga at Bhitora Ghat as part of the efforts to conserve the endangered dolphin population in the river. The census attained significance as there has been a major rise in the count of dolphins this year as compared to last years’ figure of seven conducted by the state forest department.“Nearly 35 km of stretch from Bhitora in Fatehpur has emerged as the region’s most congenial habitat for endangered Gangetic dolphins. The first ever headcount operation through sonar monitoring systems and camera-fitted balloons of the aquatic animals conducted recently, has come out with sighting of 19 dolphins. Significantly, the census figure found more dolphins inhabiting in both up and down streams of Ganga,” informed Harumi Sugimatsu, an acoustical engineer associated with the University of Tokyo’s Institute of Industrial Science, who is part of the team.“While five dolphins were sighted in the upstream towards Kanpur, 14 others were counted inhabiting near Durga Ghat at Bhitora in the up and down streams,” said Rajendra Bahl , professor in Centre for Applied Research in Electronics at the IIT, Delhi.As the sighting of dolphins has become a routine feature for wildlife enthusiasts, a census by IIT-Delhi, University of Tokyo and Society for Conservation of Nature was done to find out the exact number of the endangered animal.How the survey is being doneThe hydrophone system dangles in the water suspended from a boat’s prow. The line of individual hydrophones, used to study the lonely dolphin, has been replaced by a single piece of equipment holding six hydrophones. These sensors are arranged to pick up sounds coming from every direction, so they’ll capture more sonar beams as passing dolphins scan back and forth. Each pair of hydrophones is like a pair of ears, Bahl said.To locate the source of sounds, the system uses triangulation: A dolphin click, travelling at the speed of sound through water (roughly 1,500 metre per second) reaches one end-point hydrophone, a fraction of a millisecond before the other. The hydrophone in the middle acts as a ‘third ear’ to provide another data point, and thus more precision. The system then calculates how far that sound travelled to reach each hydrophone to determine the dolphins direction and distance. For every 40 microsecond clicks, the system runs the calculation for both sets of ears.Bahl explained that the system can pinpoint a dolphin’s location within a few metre, making it precise enough to track individual creatures.