Bengal home to 111 endangered Irrawaddy dolphins, Sundarbans has 108: Nat’l survey
Times of India | 5 March 2025
12345 Kolkata: In the first comprehensive study on Irrawaddy dolphins — estuarine dolphins that are more salt-tolerant — in the Indian Sundarbans, researchers found that the delta harbours 108 of these endangered dolphins. The findings emerged during the release of the inaugural nationwide report on Ganges river dolphins, also classified as endangered on the IUCN Red list.
Including three Irrawaddy dolphins in the Diamond Harbour stretch of the Hooghly, Bengal now houses 111 of these dolphins.
Regarding Ganges river dolphins, predominantly found in freshwater, the study revealed that of the 815 documented in Bengal, the Farakka barrage to Diamond Harbour stretch of Ganga houses the largest concentration — 429. Bakshi canal of the Rupnarayan river system exhibited the highest encounter frequency at 3.6 per kilometre.
Despite fishing and vessel traffic challenges, both dolphin species are doing well in Bengal, said a scientist.
After examining 86 river channels, encompassing 958 km in the Sundarbans Tiger Reserve and 566 km in South 24 Parganas division, researchers identified 94 Irrawaddy dolphins with a minimum count of 75 in tiger reserve area, whilst the biosphere reserve or the buffer zone houses 14 dolphins with a minimum count of 8.
The current survey identified merely two Ganges river dolphins in the Indian Sundarbans. "They were spotted in a 26 km stretch of Chayakapura-Katuajhuri river. The Bangladesh Sundarbans, having lower salinity, supports higher river dolphin numbers," said Qamar Qureshi, former scientist with Wildlife Institute of India, who was closely associated with the study.
Meanwhile, the report said that the 483km Farakka Barrage-Diamond Harbour stretch housed 429 river dolphins. The Rupnarayan river system, including tributaries, supports an estimated 217 river dolphins, with lower and upper limits of 207 and 228, respectively.
Bengal's highest river dolphin encounter rate was recorded at Bakshi canal of the Rupnarayan system at 3.6 per kilometre, supporting 21 dolphins. The Gauripur-Rajmahal stretch of Mahananda river sustains 64 river dolphins.
The dolphin population remains robust, according to Debal Roy, state's head of forest force. Qureshi identified fishing and vessel traffic as primary threats to both Irrawaddy and river dolphins in Bengal. He advocated providing pingers to all fishermen with administrative cost coverage. These devices, attached to fishing nets, alert marine mammals to net presence.
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