Why in news
The first estimate of Gangetic dolphins found 6,327 in the Ganga and its tributaries, including 6,324 Ganges river dolphins and 3 Indus river dolphins.
Survey
The study used acoustic hydrophones (underwater microphones) to detect dolphin sounds, as dolphins are hard to count due to their underwater habitat and inability to be uniquely identified like land animals.
Unlike land animals, dolphins can't be identified easily due to their reliance on echolocation and sporadic surfacing for breathing.
The team used boats and hydrophones to triangulate their location and avoid double counting.
The dolphins were distributed across various locations: 3,275 in the Ganga main stem, 2,414 in tributaries, 584 in the Brahmaputra main stem, and 101 in the Beas river.
Challenges to dolphin survival include entanglement in fishing nets and habitat pollution.
The highest number of dolphins were found in Uttar Pradesh, followed by Bihar, West Bengal, and Assam.
COMMENTS