Updated August 2021
Background and Status
Irrawaddy dolphins (Orcaella brevirostris) are coastal dolphins that are patchily distributed in the nearshore waters of south and southeast Asia. Three discrete riverine populations occur in the Mekong, Mahakam and Ayeyarwady Rivers of Cambodia, Indonesia and Myanmar, respectively. The Irrawaddy dolphin species is red-listed as Endangered, while the three riverine subpopulations are all Critically Endangered (Mekong, Mahakam, Ayeyarwady).
The effective range of Irrawaddy dolphins in the Mekong River is a 180 km segment from Kratie Township, Kratie Province, Cambodia (about 500 km upstream of the Mekong river mouth in Viet Nam) to slightly upstream of the Laos/Cambodia border just below the Khone Falls (or Lee Pee) in Champassak province, Lao PDR. In the distant past, in addition to the Mekong River, dolphins also occurred in the Sekong, Sesan and Srepok Rivers, however, these rivers are no longer inhabited by dolphins (Beasley 2007). In the last 10-15 years, the primary habitat of the dolphins during the low-water season has been in nine deep pools (Beasley 2007). However, during surveys conducted in 2020 and 2021, no dolphins were observed in some of the pools, likely due to changing and reduced dry-season water levels.