The Irrawaddy Dolphin’s habitat preferences for freshwater and near shore marine environments make the species especially vulnerable to intensive human use and abuse. Living in very confined areas, freshwater populations are in particularly serious decline in terms of range and size.
The Mekong population makes no exception to this trend: Research indicates a minimum mortality rate of 16-20% over the last 3 years, which is clearly unsustainable. In fact, scientists suggest that mortality rates should not exceed 1-2% to ensure this small population’s long-term survival. Calf mortality rates are mysteriously high, and there is no evidence that a single calf has survived to independence during the last 3 years.

Historically, populations were decimated by hunting for meat and oil, accidental drowning in nets, explosives fishing, and even being used as target practice by various armies during Cambodia’s recent troubled periods. Today, accidental drowning in gillnets is the main threat to adult Irrawaddy dolphins in the Mekong, especially with fishing becoming increasing intensive and cheap nylon gillnets replacing thicker traditional nets that could be detected by dolphin echolocation. But many other possible threats exist:
  • Overfishing with small-meshed nylon nets that depletes fish stocks and threatens future livelihoods of humans and dolphins. Illegal fishing methods using electricity or explosives can even kill dolphins directly.
  • Dams and irrigation systems reduce habitat availability for fish and dolphins, particularly in the crucial dry season, change the water flow and block fish and dolphin migration.
  • The hydropower-dams that are planned along the Mekong-mainstream could have disastrous consequences for dolphins, many other species, and the people that depend on it, as they cause large-scale shifts in habitat size, water flow, sedimentation, and animal mobility.
  • Pesticides, heavy metals, plastic particles and other contaminants from industry, agriculture, and towns have been implicated in dolphin mortality and, since many of these pollutants are persistent, will affect local biodiversity for many years to come.
  • Boat traffic on the Mekong is increasing with rising human populations, development and tourism. This can disturb dolphins, lead to stress and illness, and even result in collision-associated deaths of dolphins through contact with the propeller.
© Phay Somany / WWF-Cambodia
Regular patrols enforce a ban on nylon gillnets that can be dangerous for dolphins.
© Phay Somany / WWF-Cambodia