quality:correction
Ecology

No complete and precise list of all the fish in the Irrawaddy river basin currently exists, but in 1996 it was estimated that there are about 200 species. In 2008, it was estimated that the Irrawaddy ecoregion is home to 119–195 species of fish found nowhere else in the world (endemic). Several new species of fish have been described from the Irrawaddy river basin in recent years (for example, the cyprinid Danio htamanthinus in 2016 and the stone loach Malihkaia aligera in 2017), and it is likely that undescribed species remain.

Among the most well-known species in the river is the Irrawaddy dolphin (Orcaella brevirostris), a euryhaline species of oceanic dolphin with a high and rounded forehead, lacking a beak. It is found in discontinuous sub-populations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and South-East Asia.

Along the north–south course of the Irrawaddy River, a number of notably different ecoregions can be distinguished.