First-ever Comprehensive Survey of India’s River Dolphins

Context

• India’s first-ever riverine dolphin estimation report has recorded 6,327 dolphins across 28 rivers in eight states. Uttar Pradesh recorded the highest number, followed by Bihar, West Bengal, and Assam.
• Previous attempts to map the population used significantly different methods, making the latest figure less helpful for determining whether their numbers have changed over time.

Key Findings

• As per a press report from the Environment Ministry observed as World Wildlife Day, there are 6,324 Ganges River dolphins and three Indus River dolphins (a closely related species).
• In UP, the highest encounter or concentration of dolphins was found in the 47-km stretch of Bhind-Pachnada in Chambal River.

• The Kanpur-Vindhyachal stretch of 380 km had an encounter rate of 1.89 dolphins per kilometer, while the dolphin population along the 366-km Narora to Kanpur stretch was nearly absent, the report stated.
• In Bihar, the survey found thriving dolphin populations in stretches with higher water depth from tributaries like Ghaghara, Gandak, Kosi, and Son, along with favorable river morphology.

Survey Method

• The survey, conducted by the Wildlife Institute of India and other state forest departments under Project Dolphin, launched in 2020.
• Dolphins are underwater and surface sporadically to breathe, making them difficult to count. Unlike tigers and elephants, which can be identified by distinctive features like stripes or ears, individual dolphins cannot be uniquely recognized in the same way.
• For their survey, researchers traveled by boat at a constant speed, using acoustic hydrophones to detect sounds emitted by the blind dolphins, which rely on echolocation to communicate and navigate.

About Gangetic Dolphin and Indus Dolphin

• India is home to two species of freshwater dolphins — the Ganges (Platanista gangetica) and the Indus (Platanista minor), which act as bio-indicators of the health of river ecosystems.
• Both dolphins are classified as Endangered and listed as Schedule I species under the provisions of the Wild Life (Protection) Act, 1972.
• The Ganges River dolphin can only live in freshwater and is essentially blind. They hunt by emitting ultrasonic sounds, which bounces off of fish and other prey, enabling them to “see” an image in their mind.
• The Indus river Dolphin is endemic to the Indus River basin in Pakistan and Beas River in northwestern India.