Tracking India’s Aquatic Heritage: The First Comprehensive Dolphin Survey

Context

• Riverine dolphins are indicator species, reflecting the health of freshwater ecosystems.
• The Gangetic dolphin (Platanista gangetica gangetica) is India’s National Aquatic Animal and plays a crucial role in maintaining ecological balance.
• Both the Gangetic dolphin and Indus River dolphin are classified as Endangered under the IUCN Red List and are legally protected under Schedule I of the Wildlife Protection Act, 1972.
• The survey (2021-2023) provides the first-ever comprehensive estimation of India’s riverine dolphin population, aiding in evidence-based conservation efforts.

Key Findings of the Riverine Dolphin Survey (2021-2023)

Survey Overview

• Conducted by the Wildlife Institute of India (WII) under the Union Ministry of Environment, Forest, and Climate Change (MoEFCC).
• Covered 28 rivers by boat and 30 rivers by road, spanning the Ganga, Brahmaputra, and Beas river basins.
• Total river stretch surveyed: 8,507 km
  • Ganga and tributaries: 7,109 km
  • Brahmaputra system: 1,297 km
  • Beas River: 101 km

Dolphin Population Estimates

Gangetic Dolphin Population: 6,324 (Estimated Range: 5,977 – 6,688)

• Ganga River (Main Stem) – 3,275 dolphins
• Ganga Tributaries – 2,414 dolphins
• Brahmaputra River (Main Stem) – 584 dolphins
• Brahmaputra Tributaries – 51 dolphins

Indus River Dolphin Population: 3

• Found only in the Beas River, Punjab, indicating severe population decline.

State-Wise Distribution of Gangetic Dolphins

• Uttar Pradesh – 2,397 (Highest population)
• Bihar – 2,220
• West Bengal – 815
• Jharkhand – 162
• Rajasthan & Madhya Pradesh – 95
• Punjab – 3

Challenges in Dolphin Population Estimation

• Turbid Waters – River dolphins inhabit murky waters, making visual detection difficult.
• Brief Surface Time – Dolphins surface for 1.26 seconds before diving for 107 seconds, leading to:
  • Observer Error – Some dolphins may be missed.
  • Availability Error – Some dolphins may remain underwater throughout the survey period.

Survey Methodology

1. Visual Survey Methods

• Double Observer Method (for deep and wide river channels)
  • Two teams scan both sides of the vessel.
  • Boat speed maintained at 8–10 km/hour to prevent double counting.
• Tandem Method (for narrow channels <600m wide, <3m deep).
• Single Boat Method (for very narrow channels <300m wide, <2m deep).

2. Acoustic Surveys

• Uses hydrophones to detect dolphin echolocation clicks.
• Helps in triangulating dolphin locations and reducing observer error.

Dolphin Distribution: Hotspots vs. Coldspots

Coldspots – Areas with Low or No Dolphin Presence

• Ganga River:
  • Narora to Kanpur (366 km) – Extremely low encounter rate (0.1 dolphins/km).
  • Farukkhabad-Kannauj – Another critical coldspot.
• Other Coldspots:
  • Yamuna River (Kaushambi-Chitrakoot)
  • Sharda River (Pilibhit)
  • Rapti River (Balrampur-Siddharth Nagar)
  • Barak River (Assam)
  • Subansiri and Kulsi Rivers (Assam) – Dolphin population declining.

Hotspots – Areas with High Dolphin Population

• Uttar Pradesh – Encounter rate: 0.62 dolphins/km
• Bihar – Highest encounter rate: 1.62 dolphins/km, due to deeper river channels and tributary confluences (Ghaghara, Gandak, Kosi, Son).
• Densely Populated Stretches:
  • Chausa-Manihar (590 km) – 2.20 dolphins/km
  • Manihari (Bihar) to Rajmahal (Jharkhand) – 2.75 dolphins/km (highest density)

Conservation Implications and Challenges

Threats to Riverine Dolphins

• Pollution – Industrial effluents, pesticides, and plastic waste degrade dolphin habitats.
• Habitat Fragmentation – Dams and barrages disrupt river flow and impact prey availability.
• Overfishing – Declining fish populations due to unsustainable fishing practices.
• Climate Change – Erratic rainfall and altered river dynamics affect dolphin breeding patterns.
• Accidental Entanglement – Dolphins get trapped in fishing nets, leading to injuries and fatalities.

Government Initiatives for Dolphin Conservation

• Project Dolphin (2020) – Launched under the Namami Gange Programme, focusing on dolphin conservation in the Ganga and its tributaries.
• National Ganga River Dolphin Conservation Action Plan (2010-2020) – Outlined protection measures for Gangetic dolphins.
• Biosphere Reserves & Protected Areas – Vikramshila Gangetic Dolphin Sanctuary (Bihar) is a critical dolphin habitat.
• Community Participation – Efforts to involve local communities in conservation and awareness programs.

Way Forward

• Strengthening Pollution Control Measures – Enforcing strict environmental regulations on industries and urban sewage.
• Restoring River Ecosystems – Ensuring adequate water flow, reducing sand mining, and controlling illegal fishing.
• Scientific Monitoring & Research – Expanding acoustic survey techniques for better population estimation.
• Sustainable Development Strategies – Balancing infrastructure projects with wildlife conservation.
• International Collaboration – Learning from conservation models in Nepal and Bangladesh, which share dolphin habitats.

Conclusion

• The 2021-2023 dolphin survey provides crucial insights into the status of India's riverine dolphins.
• The presence of over 6,000 Gangetic dolphins is encouraging, but the critically low Indus River dolphin population is alarming.
• Dolphins are indicators of river health—protecting them ensures sustainable freshwater ecosystems.
• Urgent conservation efforts are needed to address habitat degradation, pollution, and human-induced threats.
• Strengthening Project Dolphin and enhancing community-based conservation programs will be essential in ensuring long-term protection of India's National Aquatic Animal.