A recent survey of Irrawaddy dolphins in the Mekong River showed their numbers have dropped to only 85. Their population has been studied by photographing them and noting unique markings of their dorsal fins. Survival of their calves is very low, so the small numbers mean they could go extinct. They are mainly threatened by fishing practices that result in them being accidentally caught, as well as habitat loss. In the 1950s there thousands living in the Mekong. Now on any given day, there may be more tourist boats looking for them than there are dolphins.
Thailand, Burma, the Philippines, India and Indonesia also have critically endangered populations. Only the Irrawaddy living in Bangladeshi waters are at more stable population of about 5,800.
Irrawaddy dolphins are actually ocean dolphins that live in brackish water. They have been known for behaviors such as spitting water, fluke-slapping and spyhopping, which means they raise their heads out of the water to see better. (Orcas also do this.)
There have been reports these dolphins sometimes help fishermen by driving fish into their nets. Sadly, it is this close relationship with humans that is costing many dolphin lives because they get stuck in their nets sometimes and drown. Habitat loss occurs when river development projects like dams and levees are constructed. Additionally sometimes explosive devices are used for fishing to kill fish in the Mekong’s deep pools. Such loud explosions can injure or kill the dolphins.