The species regarded as the “living treasure” of the Mekong River—the longest river in Southeast Asia—is the Irrawaddy dolphin (scientific name: Orcaella brevirostris).
International biologists consider this beautiful, petite dolphin a symbol of the grandeur of the Mekong River, which ranks as the seventh longest river in Asia and the twelfth in the world (4,350 km), along with its continuous high biodiversity.
Image of the rare Irrawaddy dolphin living in the Mekong River. (Photo: Getty Images).
However, this species is facing the risk of extinction in the wild. Human activities have significantly reduced the population of this species. Let’s explore the causes and the efforts taken by humans to rectify this situation and protect biodiversity on our planet.
“Living Treasure” of the Longest River in Southeast Asia
The IUCN reports that Irrawaddy dolphins are distributed discontinuously in the coastal waters of the tropical and subtropical Indian and Pacific Oceans, and are primarily associated with freshwater sources.
According to a 2017 survey conducted by the IUCN, Irrawaddy dolphins are found in 12 Asian countries: Bangladesh, Brunei, Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam (known as ‘cá nược’ in our country).
Coastal and river estuary populations range from Borneo and the central islands of Indonesia northward to Palawan in the Philippines and westward to the Bay of Bengal, including the Gulf of Thailand. Additionally, there are freshwater subpopulations in three major rivers: the Ayeyarwady in Myanmar (up to 1,400 km upstream from the river mouth), the Mahakam in Indonesia, and the Mekong River flowing through Cambodia and Laos.
Currently, the 180 km stretch of the Mekong River in northeastern Cambodia is the last intact ecological habitat for Irrawaddy dolphins.
Irrawaddy dolphins living in the Mekong River in northeastern Cambodia represent the largest population. (Photo: Thai National Parks).
This river section is home to 89 individuals of Irrawaddy dolphins (according to a 2020 survey by the Ministry of Agriculture, Forestry and Fisheries of Cambodia); and it is also one of 35 priority conservation areas identified by the World Wildlife Fund (WWF) globally.
Although there are only 89 individuals, this makes the population of Irrawaddy dolphins in the Mekong River in northeastern Cambodia the largest among the five critically endangered freshwater populations of this species worldwide.
Thai National Parks states that one of the earliest documented descriptions of the Irrawaddy dolphin was made by British biologist Sir Richard Owen in 1866, based on a specimen found in 1852 at the Visakhapatnam port on the eastern coast of India.
Genetically, the Irrawaddy dolphin is closely related to the killer whale (Orca). This is the largest dolphin species and one of the strongest predators in the world, known as the ‘ocean killer’. When hunting in pods, orcas can successfully kill a blue whale—the largest animal on Earth, as reported by National Geographic.
According to the information on the World Wildlife Fund’s website, the Irrawaddy dolphin is a small, shy dolphin with gray-black coloration that is lighter on the underside, a small rounded dorsal fin, and a blunt rounded head. They can grow up to 2.75 meters long, weigh up to 150 kg, and usually live in groups of up to 6 individuals.
The Irrawaddy dolphin spends most of its time foraging. They are not particularly active dolphins or fond of acrobatics. This species usually dives for under 2 minutes, but the dive time may slightly increase when they feel threatened. The lifespan of the Irrawaddy dolphin is about 30 years, and while some individuals reach mature size between the ages of 4 and 6, the specific age of maturity is still unknown.
The Irrawaddy dolphin is one of three species of whales and dolphins that live in both freshwater and saltwater. The marine populations reside in coastal areas, particularly in muddy and brackish waters, while the freshwater populations prefer the deeper waters of lakes and large rivers. The largest known population of marine dolphins is approximately 6,000 individuals found off the coast of Bangladesh.
All five remaining freshwater populations have fewer than 100 individuals and are listed in the IUCN Red List as Critically Endangered (CR) and Endangered (EN), depending on their distribution across different countries.
Specifically, the Irrawaddy dolphin (Orcaella brevirostris) has been continuously assessed by the IUCN since 1988. By 2017, the species faced extinction risk and was categorized as Endangered (EN).
According to the IUCN assessment, Irrawaddy dolphins were previously found throughout the Mekong River from the Laos-Cambodia border down to the delta in Vietnam and in Tonle Sap Lake (Cambodia)—the largest freshwater lake in Southeast Asia.
The population and distribution of this dolphin species have significantly decreased over the past four decades. During the dry season, from January to May, when water levels are low, the dolphin population concentrates in nine deep pools along a 180 km stretch of the Mekong River from northern Kratie (eastern Cambodia) to the Laos border.
While these pools provide safe habitats for dolphins to rest and forage, such concentration also makes them vulnerable to human fishing activities.
Threats to the Mekong River Dolphin Population
The Irrawaddy dolphin’s preference for freshwater and coastal areas near river mouths makes this species particularly vulnerable to overexploitation and misuse by humans (as human activities often concentrate in these areas). Living in very restricted areas, the freshwater population is seriously declining in range and size.
Traditionally, the Irrawaddy dolphin population was decimated due to hunting for meat and oil, becoming entangled in fishing gear, fishing using explosives, and even being targeted for practice by military forces.
An Irrawaddy dolphin swimming in the Mekong River in Kratie province of Cambodia, March 24, 2012. (Photo: AFP/Gerry Ryan/WWF-Cambodia).
Today, accidental mortality rates in small-scale fisheries—such as entanglement in gill nets—are the main threat to adult Irrawaddy dolphins in the Mekong River, especially as fishing becomes increasingly intensive and nylon gill nets replace traditional, thicker nets, making it harder for dolphins to detect fish using their echolocation tools.
Additionally, there are several other potential threats, including habitat loss and degradation. The construction of dams and irrigation systems reduces dolphin habitats; pollution from pesticides, heavy metals, plastics, and other industrial and agricultural pollutants deteriorates river quality;
Lastly, waterway traffic (boat movement for transport and tourism stresses dolphins, as they are very afraid of boats, making them susceptible to diseases, and even leading to death due to collisions with boat propellers.
Successful Rectification!
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has placed the Irrawaddy dolphin on the list of species that require urgent protection.
In 2004, CITES moved the Irrawaddy dolphin from Appendix II to Appendix I, prohibiting all commercial trade activities concerning endangered species globally.
The number of dolphins in the Mekong River in Cambodia has increased from 89 to a total of 105 individuals. (Photo: Rainforestcruises).
In 2005, the World Wildlife Fund (WWF) established the Cambodia Mekong Dolphin Conservation Project (WWF-Cambodia) with the support of the government and local communities.
On August 24, 2012, the Cambodian government announced that the 180 km stretch of the Mekong River in northeastern Cambodia was declared a fishing exclusion zone, prohibiting the use of floating houses, fishing cages, and gill nets. This area is patrolled 24/7 by a network of River Police, specifically to protect Irrawaddy dolphins.
Thanks to relentless efforts to protect and conserve the Irrawaddy dolphin, by July 2024, the world received good news from the Minister of Agriculture, Forestry, and Fisheries of Cambodia: the number of dolphins in the Mekong River in Cambodia has increased from 89 to a total of 105 individuals, as reported by Phnom Penh Post.
This is a significant effort from Cambodia (from the government level, provincial authorities to local communities) as well as environmental organizations like the World Wildlife Fund in Cambodia.
Since stabilizing the Irrawaddy dolphin population starting in 2010, the number of newborn dolphins has significantly increased. Simultaneously, mortality rates have consistently decreased: from 9 deaths in 2015 to 6 in 2016 and only 2 in 2017 (as of mid-November), with 9 dolphins born in the same year.
The contribution to these results comes from our team of skilled staff. Through training, their knowledge and capabilities enable the team to carry out conservation work effectively. This, along with a close relationship with local media, government officials, and villagers, has contributed to overall success.
This effort demonstrates how important it is to protect biodiversity on Earth for both the animal and plant worlds, as well as for humanity itself.
