Pesut Mahakam (Orchaella brevirostris) is an Indonesian freshwater dolphin that can only be found in the Mahakam River Basin in East Kalimantan. The Mahakam River is the main habitat for these animals, distributed from the Mahakam Delta (Samarinda) to West Kutai (Melak), while the lake and swamp are cruises for playing and foraging. The distribution of the Mahakam Pesut (Orchaella brevirostris) in the Mahakam River has always shifted from time to time. The study was conducted in 2017 - 2018 in Samarinda, Kutai Kartanegara and West Kutai, East Kalimantan, with survey methods and direct interviews with fishermen, community members, the Marine and Fisheries Service, and the Natural Resources Conservation Agency (BKSDA) of East Kalimantan Province. The purpose of this study was to determine the population and distribution of Pesut (Orchaella brevirostris) in the Mahakam River. Pesut Mahakam (Orchaella brevirostris) era before the 1980s distributed from the Mahakam Delta to the Upper (Melak); in the era of 1980 - 2000 Pesut Mahakam was distributed from the Kutai Kartanegara area to Melak; whereas the era of 2000 until now Pesut Mahakam is only distributed in the Kutai Kertanegara region (Middle Mahakam).

Keywords : Distribution; Pesut Mahakam; From time to time; Mahakam watershed.