Freshwater habitats’ biological equilibrium depends critically on river dolphins, especially Indus and Gangetic dolphins. But pollution, habitat erosion, and climate change pose growing challenges to these aquatic species. Between 2021 and 2023, India undertook the first thorough study to estimate the population of these threatened species, therefore offering vital information on their present count. Under the Ministry of Environment, the Wildlife Institute of India (WII) is leading a trailblazing project to comprehend and protect river dolphins in this census.
In This Article:
Combining Visual and Acoustic Techniques: Survey Methodology
Combining optical and audio studies helped one reasonably estimate the river dolphin population. For the visual surveys, teams of observers set out on boats navigating different lengths of the Ganga, Brahmaputra, and Beas rivers. River dolphins are elusive. Hence, viewers utilized several techniques to ensure none missed any dolphins. Two crews examined both sides of the boat using a double observer method, where bigger and deeper river channels were covered. The Single Boat Method and Tandem Method were applied in smaller channels.
However, given the small surface time of dolphins—typically about 1.26 seconds per 107 seconds of diving—visual surveys alone could not provide a total count. Acoustic studies utilizing hydrophones—underwater microphones detecting echolocation clicks produced by the dolphins—were also carried out to handle this. Functionally blind, dolphins use these sound waves to find their way around. Multiple hydrophones would allow researchers to triangulate the dolphin positions, lowering observer mistakes and increasing survey accuracy.
Problems Predicting Dolphin Counts
There is no easy chore involved in counting river dolphins. The main difficulty is in the muddy rivers such as the Ganga and Brahmaputra, where limited visibility makes it challenging to find the animals. River dolphins also only surface momentarily for air; hence, viewers may overlook them in the few intervals when they show up at the water’s surface. Moreover, some dolphins may not emerge throughout the counting time, causing final count availability problems. Combining acoustic techniques with visual polls helps to overcome these difficulties and generates more accurate population estimates.
Surveying challenging terrain and spanning great distances was another challenge for the researchers. Including parts of the Ganga, Brahmaputra, and Beas rivers, the length under observation during this census was around 8,500 km. The effectiveness of this multi-method approach was evidence of the diligence and inventiveness required in the census, given the vast geographic region and diverse environmental circumstances.
Important Discoveries and Conservation Conventions
The poll yielded notable findings. With the most significant concentration discovered in Uttar Pradesh and Bihar, Gangetic dolphins were considered number 6,324 overall. By comparison, the Beas River in Punjab revealed only three Indus river dolphins. The research also identified several hotspots for dolphin numbers, like the confluence of streams in Bihar, with an average encounter rate of 2.75 dolphins per km. Conversely, places like Uttar Pradesh’s Narora-Kanpur stretch and rivers like the Yamuna and Sharda were noted as coldspots with either little or no dolphin presence.
The census findings highlight how urgently conservation initiatives to save river dolphins—especially in places where population declines—are needed. Among the primary challenges these species face are pollution, habitat degradation, and decreased prey availability, so the census data is somewhat helpful in formulating focused conservation plans.
A step towards conservation
Apart from giving a picture of the population of these threatened species, the first-ever thorough river dolphin count has provided vital information to guide the following conservation plans. Though surveying muddy river habitats has inherent difficulties, researchers have greatly improved the accuracy of population estimates by combining optical and audio approaches. The information from this study will direct initiatives to safeguard the habitats of these species and guarantee their survival for the next generations in the face of increasing dangers. This project’s success emphasizes the need for group, multifarious strategies in the protection of wildlife, particularly for species as threatened as river dolphins.
By – Bhawana
