Over 70 per cent of premature deaths of the endangered Gangetic dolphin have occurred along the Hooghly and the Ganga’s main stem, scientists have found in a new study which mapped mortality hotspots along the river.

Researchers who investigated 76 dolphin deaths in 14 rivers in the Ganga basin have found that a third of the dolphins died in accidents, trapped in fishing nets or struck by boats — but the cause of death of an equal number remains unknown.

The Hooghly river accounted for 29 (38.2 per cent) of the 76 deaths documented between 2008 and 2024, followed by 26 in the Ganga main stem in Uttar Pradesh, Bihar and Jharkhand, according to the study published in the journal Ecological Informatics.

The study has identified 770km of river stretches as high-risk hotspots for human-caused mortality, notably the Ganga’s lower segments downstream of the
Kosi-Ganga confluence and the Hooghly.

The findings build on earlier indications that the Gangetic dolphin has suffered population declines from unsustainable fishing, habitat fragmentation by dams and barrages, poaching, pollution, and collisions with boats. But with dolphins spread across more than 5,000km of river stretches in the Ganga basin, scientists say, blanket conservation is difficult. Identifying mortality hotspots — specific stretches where threats and habitats converge — is therefore critical.

“Mapping hotspots will help authorities focus conservation efforts and prioritise limited resources in the most critical zones, making conservation more effective,” Ruchi Badola, professor at the Wildlife Institute of India, Dehradun, and a co-author of the study, told The Telegraph.

The WII researchers found that 25 (32.9 per cent) of the 76 deaths occurred when dolphins got caught in fishing nets, were hit by boats, or were killed in dredging operations, while 11 dolphins died after they were stranded in canals or shallow water. At least eight dolphins were killed for meat and four identified as victims of “retaliatory killings”.

The researchers have called for targeted interventions along the hotspots, including rapid rescue and veterinary response teams, stricter fishing regulations, and community-based conservation to balance the needs of riverside communities with the protection of India’s national aquatic animal. They say such measures could also serve as pilot projects to test strategies to reduce the human-dolphin conflict.

The study’s coauthors are Syed Ainul Hussain, Goura Chandra Das, Surya Prasad Sharma, Aftab Alam Usmani, Shivani Barthwal and Srishti Badola, all at the WII.

The new findings come against the backdrop of fresh government efforts to strengthen dolphin conservation. In March this year, India released the results of its first-ever river dolphin estimation exercise, putting the population at around 6,300, with the highest numbers in Uttar Pradesh, followed by Bihar, Bengal and Assam.

The Union water resources ministry has approved a ₹1-crore project to develop a specialised rescue vehicle — dubbed a “dolphin ambulance” — to respond to animals in distress.