• Prime Minister Narendra Modi released the report of the first-ever riverine dolphin estimation conducted in the country during the seventh meeting of the National Board for Wildlife on March 3.

• The report titled ‘Population Status of River Dolphin in India’ has revealed the presence of 6,327 dolphins in the Ganga, Brahmaputra and Indus river systems.

• This pioneering effort involved surveying 28 rivers across eight states, with 3,150 man-days covering over 8,500 kilometers.

• Uttar Pradesh has the highest number of dolphins at 2,397, followed by Bihar 2,220, West Bengal 815, Assam 635, Jharkhand 162, Rajasthan and Madhya Pradesh 95, and Punjab 3.

• The Prime Minister emphasised the importance of awareness on dolphin conservation by involvement of local population and villagers in the areas. He also advised organising exposure visits of school children in dolphin habitat areas.

Project Dolphin 

• During his address on Independence Day on August 15, 2020, PM Modi announced ‘Project Dolphin’ for the conservation of both marine and riverine dolphins as well as the associated cetaceans.

• Project Dolphin is envisaged to bring both river dolphins and marine dolphins under its conservation programme.

• This project aims to address existing conservation concerns and to empower the stakeholders to participate in conservation of dolphins.

• A robust scientific monitoring of any population is the single most crucial aspect that is needed for any effective conservation action, and to ensure the long-term survival of a species. 

• The river and marine ecosystem is the lifeline for the most marginal people in the country, apart from several threatened and endangered fauna. Dolphin acts as an umbrella species, whose conservation will result in the wellbeing of associated habitat and biodiversity, including humans.

• Under Project Dolphin, the first-ever comprehensive survey has successfully estimated the population of river dolphins across eight states. 

• This marks one of the world’s largest freshwater surveys, covering the entire range of the Ganges River Dolphin in the Ganga and Brahmaputra, as well as the Indus River Dolphin in the Beas river.  

Survey methodology

• During the survey, data on dolphin abundance, habitat quality, anthropogenic pressure, and associated fauna were collected. 

• The estimation of river dolphins has always been a challenging task, given the habitat and short surfacing time of the species.

• The population status has largely been understood through encounter rates and in some stretches through line transect.

• Dolphins surface only for just about 1.26 seconds and dive for about 107 seconds. 

• To address observer and availability biases, active boat-based surveys employed the independent double observer method and underwater acoustic hydrophones, with data analysed using Lincoln-Peterson's Chapman’s corrected formula and the Huggins method to estimate dolphin abundance.

• In Ganga, a total of 7,109 km was actively surveyed, which includes its tributaries — Chambal, Yamuna, Rapti, Sharda, Ghaghara, Mahanada, Kosi, Gandak, Geruwa, Rupnarayan, Torsa, Kaljani, Churni and Haldi covering the states of Uttar Pradesh, Bihar, Jharkhand, West Bengal, Madhya Pradesh and Rajasthan.

• In Brahmaputra, 1,297 km of the river was surveyed including the tributaries Subansiri, Kulsi, Beki, Kopili and Barak river in Assam and 101 km in Beas River was surveyed for the Indus River Dolphin. 

• The survey covering over 8,000 km was conducted from 2021 to 2023. It included eight states along the Ganga and Brahmaputra rivers and their tributaries, as well as the Beas river.  

• During the survey, 58 rivers were assessed. Of these, 28 rivers were actively surveyed by boat, while 30 were studied through road surveys, focusing on locations where the Ganges river dolphin had been historically reported.

• The dolphin estimate for Ganga is 5,689, while 635 dolphins were estimated in Brahmaputra, totalling to a population estimate of 6,324 in the surveyed rivers. 

• While the Indus River Dolphin population was always small, six individuals were reported in 2018. While three individuals were sighted during the survey, a recent mortality of one adult female has brought the status of the current population to two individuals. 

Key facts about river dolphins in India:

• River dolphins are indicator of a healthy river and act as an umbrella species of the river ecosystem. 

• There are currently two species of the river dolphins inhabiting India — Ganges River Dolphin (Platanista gangetica) and Indus River Dolphin (Platanista minor).

• Ganges River Dolphin is listed in Schedule I of the Indian Wildlife (Protection) Act 1972 in India, and was declared as the National Aquatic Animal of India and the State Aquatic Animal of Assam in 2009. 

• They are also accorded the highest protection priority for conservation, by being listed in Appendix I of CITES and Appendix II of Conference of the Parties to the Convention on the Conservation of Migratory Species of Wild Animals.

• The Indus River Dolphins in India are only distributed in a small pocket of the Beas River in Punjab, while the majority of the population are distributed in Pakistan.

• River dolphins are characterised by a long rostrum, almost small dorsal fin, and side-swimming behaviour. Males are smaller than females in both  species. They give birth once every 2-3 years, and generally to only one calf. This puts the species at a high risk of extinction, as population recovery will be slow.

• They have rudimentary eyes, as an adaptation for turbid waters and rely largely on acoustic communication for not only movement but also foraging and other life history traits. This means they can only make out the difference between light and dark, and survival mainly depends on their hearing. 

• This makes the soundscape of the river very important for the survival of the dolphins. They have the longest inner ear canals of any extant cetacean, and hence can hear a wide frequency range.

Manorama Yearbook app is now available on Google Play Store and iOS App Store