Smaller rivers in the Ganga basin are playing a crucial role in preserving the habitat of the endangered Gangetic dolphin, India's revered national aquatic animal, a joint study by the Wildlife Institute of India (WII) and the Union Government's National Mission for Clean Ganga has said.

However, they noted that despite their importance, the conservation and management of these smaller rivers have not received adequate attention compared to larger rivers.

With a comprehensive two-year-long survey covering 1,290 kilometers of the Ganga's tributaries and sub-tributaries, researchers have identified 620 kilometers of critical habitats requiring urgent conservation efforts and management strategies specifically tailored for these smaller water bodies to ensure the long-term survival of the Gangetic dolphin population.

The findings hold significance given that in recent years, the distribution range of the Gangetic dolphin in various rivers has dwindled, particularly in the upstream stretches. The aquatic mammals which are now in the IUCN list of threatened species are now believed to be extirpated from the Son, Ken, Betwa, and Sind rivers, the middle and upper stretch of the Sharda river, and the upper stretch of the Yamuna river.

"These findings not only shed light on the importance of these lesser-known rivers but also underscore their vital contribution to the ecological resilience and health of the entire Ganga river system," said Syed Ainul Hussain, a scientist at Dehradun-based WII and co-author of the study.

He added that these lesser-known rivers harbor more than 15 per cent of the Gangetic dolphins and contribute to habitat diversity. "This underscores the importance of conserving these rivers to safeguard biodiversity," Hussain emphasised, pointing out gaps in ecological restoration efforts, particularly in the conservation of smaller rivers.

While larger rivers have often been the focus of conservation efforts, the importance of smaller rivers has been largely neglected. During the two-year survey conducted boat-based visual encounter in ten rivers, covering Girwa (20 km), Kauriyala (15 km), Babai (75 km), Sharda (220 km), Rapti (500 km), Bagmati (60 km), Mahananda (230 km), Ken (40 km), Betwa (90 km), and Sind (40 km), researchers found that engagement with local communities is a crucial component of successful conservation endeavors, especially in areas where dolphin populations intersect with villages.

"By linking community concerns regarding flood erosion, embankments, and livelihood security to broader biodiversity conservation initiatives, a strategic framework can be established to garner support for river conservation efforts," said Neeraj Mahar, one of the researchers in their study "Conservation planning for Gangetic dolphin (Platanista gangetica) in smaller rivers of the Ganga River Basin, India".

The other authors of the study include Goura Chandra Das, Aftab Alam Usmani, Surya Prasad Sharma, Srijani Guha, SK Zeeshan Ali, Shivani Barthwal, Arkojyoti Sarkar, Ajay Rawat, G Gokulakrishnan, Javed Anwar, and Ruchi Badola from the Ganga Aqualife Conservation and Monitoring Centre, WII, and Sandeep Kumar Behera  from National Mission for Clean Ganga, Union Ministry of Jal Shakti.

Despite the importance of smaller rivers in Gangetic dolphin conservation, numerous challenges such as human-induced stressors such as dam construction and pollution continue to threaten the health of these river ecosystems. "However, by adopting a basin-wide approach and prioritising interconnected riverine ecosystems, we can overcome these challenges and safeguard the future of Gangetic dolphins, " said the researchers.