The dolphin census, a collaborative effort by Uttar Pradesh Forest Department and WWF-India supported by National Mission for Clean Ganga, was done under the 'My Ganga, My Dolphin' 2015 campaign of the UP government.
According to the census, stretches downstream Varanasi registered 269 dolphins and the 125 km stretch upstream of Fatehpur saw 175 dolphins.
Stretches of Ghaghra, Rapti, Gandhak, Chambal recorded an increase whereas Ramsar site Brijghat to Narora recorded a decrease, the census said.
"Besides mapping the population and distribution of Gangetic dolphins, emphasis was laid on sensitising local communities on Ganga dolphins, its importance and the steps needed to eliminate the threats," Sanjeev Saran, Principal Secretary (Forests), said.