On the evidence of the Irrawaddy Dolphin Orcaella brevirostris (Owen, 1866) (Mammalia: Cetartiodactyla: Delphinidae) in the Hooghly River, West Bengal, India

Abstract

We report the presence and status of the Irrawaddy Dolphin Orcaella brevirostris in the Hooghly River of West Bengal, India. These observations were made while conducting our field work on the Ganges River Dolphin, which involved vessel-based surveys as well as intensive monitoring from an anchored boat.

Historical and new records of the Irrawaddy Dolphins, Orcaella brevirostris (Owen in Gray, 1866) (Cetacea, Delphinidae) from the east coast of South Sumatra, Indonesia

“…Identification. The Irrawaddy Dolphin was identified by its small dorsal fin on the back, triangular pectoral fin, very short beak, and bulging forehead (Chowdhury et al 2020). The vital morphological features for this species identification included (1) a pronounced and rounded forehead, (2) no distinct beak, (3) a flexible neck-unusual among dolphin species, results in a slight depression behind the head in some animals, (4) bluish or brownish-grey upper side, (5) long broad paddle-like flippers, (6) a low blunt dorsal fin, which can vary a great deal in shape, (7) narrow tailstock, and (8) a light underside which may appear almost white in muddy water.…”

“…The Irrawaddy Dolphin, Orcaella brevirostris (Owen in Gray, 1866) (Cetacea, Delphinidae) is a marine mammal found in varied habitats such as estuaries, freshwater rivers, and coastal waters in the Indo-West Pacific (Minton et al 2017;Postrado et al 2019;Chowdhury et al 2020). In estuarine and coastal waters, these dolphin populations are known to occur in Borneo and Banten Bay of Indonesia, Palawan of Philippines, Bengal Bay of India, and the Gulf of Thailand (Minton et al 2017).…”