Giant freshwater stingray

The Mekong River is home of rare Irrawaddy river dolphins and rare pla buk, the world's largest freshwater fish, the Mekong Giant Catfish. By one count only around 100 river dolphins are left and they are mostly in northern Cambodia. But at the same time fish caught in the river are an important source of protein for an estimated 65 million people.

Jeremy Hance wrote in, “Home to giant catfish and stingrays, feeding over 60 million people, and with the largest abundance of freshwater fish in the world, the Mekong River, and its numerous tributaries, brings food, culture, and life to much of Southeast Asia. Despite this, little is known about the biodiversity and ecosystems of the Mekong, which is second only to the Amazon in terms of freshwater biodiversity. Meanwhile, the river is facing an existential crisis in the form of 77 proposed dams, while population growth, pollution, and development further imperil this understudied, but vast, ecosystem. More than 850 species have been described. [Source: Jeremy Hance,, April 23, 2013 |~|]

The Mekong river is home to around 850 species of freshwater fish, many of which are only found in the region, and a host of other animals. Researchers estimate there could be over 1,200 fish species in Mekong River. Eleanor J. Sterling and Merry D. Camhi wrote in Natural History magazine, “That mesh of waterways is one of the most productive and diverse ecosystems on Earth, supporting more than 6,000 species of vertebrates alone. Its fish fauna, with some 2,000 species, of which sixty-two are endemic, exceeds all but those of the Amazon and Congo river basins. The wetlands harbor several threatened and endangered birds and mammals, including the eastern sarus crane, Grus antigone sharpii; the Bengal florican, Houbaropsis bengalensis; and the hairy-nosed otter, Lutra sumatrana, which was recently rediscovered after having been feared extinct. Sixty-five million people live there, too, 80 percent of them dependent on the river for their livelihood as farmers and fishers. [Source: Eleanor J. Sterling and Merry D. Camhi, Natural History magazine, December 2007]

“The Mekong River Basin is a microcosm of the Earth’s freshwater resources—it includes almost all of the natural forms freshwater takes on Earth: groundwater, lakes, ponds, streams, and wetlands. (Wetlands are defined as shallow, often intermittently wet habitats, such as bogs, floodplains, marshes, and swamps.) Together, freshwater ecosystems cover less than 1 percent of the Earth’s surface and hold a mere 0.008 percent of its water, but they support about 100,000 animal species—an inordinately large number for their size relative to marine and terrestrial habitats. That freshwater fauna includes a third of all known vertebrates and a whopping 40 percent of all known fish species.

“Their rich biodiversity aside, freshwater systems bestow untold—and underappreciated—benefits on people. Indeed, they are the very foundation of our lives and economies. The value of all the services freshwater ecosystems provide worldwide, such as drinking water, irrigation for agriculture, and climate regulation, has been estimated at $70 billion per year—a figure that assumes, rather delusionally, that one could purchase the services elsewhere if they became unavailable in nature.

“Species along the Mekong, as in other freshwater systems, depend on natural flood cycles for nutrients and for transportation to and from spawning grounds. More than 90 percent of the fish species in the Mekong watershed spawn not in rivers, but in seasonal lakes or periodically flooded forests and fields.

"Elvis" Monkey and Psychedelic Gecko Among 208 New Mekong Species Discovered

In December 2011, AP reported: “A psychedelic gecko and a monkey with an "Elvis" hairdo are among 208 new species described last year by scientists in the Mekong River region of Southeast Asia, a conservation group announced. The animals were discovered in a biodiverse region that is threatened by habitat loss, deforestation, climate change and overdevelopment, the WWF said in a report. [Source: AP, December 12, 2011]

“The newly described species include a "psychedelic gecko" in southern Vietnam and a nose-less monkey in a remote province of Myanmar that looks like it wears a pompadour. "While this species, sporting an Elvis-like hairstyle, is new to science, the local people of Myanmar know it well," the Switzerland-based group said in its report. The region is home to some of the world's most endangered species, including tigers, Asian elephants, Mekong dolphins and Mekong giant catfish, the group said.

"This is a region of extraordinary richness in terms of biodiversity but also one that is extremely fragile," said Sarah Bladen, communications director for WWF Greater Mekong. "It's losing biodiversity at a tragic rate."The Mekong flows through China, Myanmar, Laos, Thailand, Cambodia and Vietnam.In October, WWF announced Vietnam has lost its last Javan rhinoceros, making the 40 to 60 Javan rhinos living in Indonesia the last remaining members of their species.

Reuters reported: “The area's diversity is so astonishing that a new species is found every two days, but regional cooperation and decision-making must take centre stage to preserve its richness, the WWF said ched into extinction. "While the 2010 discoveries are new to science, many are already destined for the dinner table, struggling to survive in shrinking habitats and at risk of extinction," said Stuart Chapman, Conservation Director of WWF Greater Mekong, in a statement.[Source: Reuters, December 12, 2011]

Among the new species highlighted in the report "Wild Mekong" is a gecko with bright orange legs, a yellow neck, and a blue-gray body with yellow bars on its bright orange sides, discovered on an island in southern Vietnam. Then there is a black and white snub-nosed monkey whose head sports an Elvis-like hairstyle, found in Myanmar's mountainous Kachin state. Locals say the animal can be spotted with its head between its knees in rainy weather as it tries to keep rain from running into its upturned nose. Other featured creatures among the 208 new finds include a lizard that reproduces via cloning without the need for male lizards, a fish that resembles a gherkin, and five species of carnivorous pitcher plant, some of which lure in and consume rats and even birds.

"Mekong governments have to stop thinking about biodiversity protection as a cost and recognise it as an investment to ensure long-term stability," Chapman said. "The region's treasure trove of biodiversity will be lost if governments fail to invest in the conservation and maintenance of biodiversity, which is so fundamental to ensuring long-term sustainability in the face of global environmental change."

Despite restrictions, trade in wildlife remains an active threat to a range of endangered animals in the region, with some hunted because body parts -- such as rhinoceros horns -- are coveted ingredients in traditional Asian medicine. Others, such as Mekong dolphins, face threats from fishing gear such as gill nets and illegal fishing methods, prompting the WWF in August to warn that one dolphin population in the river was at high risk of extinction.

126 New Species Discovered in Greater Mekong Region in 2011

A total of 126 new species were described in Asia'a Mekong region in 2011 according to report published by the World Wildlife Fund (WWF). This was on top of 208 new species described in 2010 in the Greater Mekong region, which covers five Southeast Asia nations — Cambodia, Laos, Vietnam, Thailand, and Myanmar — as well as China's Yunnan province. [Source:, December 18, 2012]

The report issued by a group called Extra Terrestrial aims to raise public awareness of the region's high levels of biodiversity as well as threats to its native ecosystems. Extra Terrestrial tallies species described for the first time in academic publications during 2011. It counts 82 plants, 13 fish, 21 reptiles, 5 amphibians and 5 mammals. The report highlights several charismatic species, including the demonic-looking Beelzebub’s bat; a new ‘walking’ catfish from Vietnam, a minuscule (2 cm long) fish from Thailand; a blind cave fish from Laos; a frog with a bird-like call; and ruby-eyed green pit viper from Vietnam.

The report notes that 1,710 new species have been described from the Greater Mekong region since 1997. “The Mekong region has a breathtaking array of biodiversity, but many of these new species are already struggling to survive in shrinking habitats,” said Dr. Barney Long, WWF Manager of Asian Species Programs, in a statement. “It’s vital that we increase our support for protected areas and greener economic development if we want these new species protected and to ensure that other intriguing species are discovered in years to come.”

Extra Terrestrial says that large-scale dams — notably the Xayaburi dam in Laos — are a major threat to the Mekong's aquatic biodiversity. Meanwhile many species in the region are vulnerable to poaching for the wildlife trade.

The new species includes: 1) the pygmy python (Python kyaiktiyo), a 1.5m-long snake from the Kyaiktiyo wildlife sanctuary in Myanmar (Burma); 2) the blue skink (Larutia nubisilvicola); 3) aA new blind cave fish (Bangana musaei) from underground karst formations in central Laos; 4) the Quang’s tree frog (Gracixalus quangi) from Vietnam, notable for singing a different call each time it vocalizes; 5) the The Ruby-eyed pit viper (Trimeresurus rubeus), discovered in the forest of Vietnam’s Cat Tien national park; 6) The yin-yang frog (Leptobrachium leucops), one of five new amphibian species discovered in the Greater Mekong region; 7) the Beelzebub’s tube-nosed bat (Murina beelzebub) from Quang Tri province, Vietnam; and 8) the tiny Boraras naevus from southern Thailand.

Endangered Species on the Mekong River

Eleanor J. Sterling and Merry D. Camhi wrote in Natural History magazine, “As a result, even as the human population of the globe has doubled, many species that depend on freshwater ecosystems have suffered steep declines. The list would bring tears to a conservationist’s eyes: in the past three decades, a fifth of the world’s water birds, a third of freshwater mammals, a third of amphibians, and more than half of freshwater turtles and crocodiles have become either threatened, endangered, or extinct. Freshwater fishes represent a quarter of the world’s living vertebrate species, and yet more than a third are threatened or endangered. The ecology of freshwater systems may be irreversibly damaged if we humans don’t improve the way we treat them. [Source: Eleanor J. Sterling and Merry D. Camhi, Natural History magazine, December 2007]

“Fish aren’t the only victims of overexploitation. As many as 10,000 water snakes are fished from Tonle Sap Lake each day. The water snakes mainly go to feed hungry crocodiles raised for commercial export; they substitute for fish, whose populations have declined. People are fishing down the food chain in the Mekong River Basin, as in so many freshwater and marine systems. After depleting the top predators and the largest species, fishermen turn their nets on successively smaller organisms.

“The upshot of all those assaults is that freshwater organisms rank among the world’s most threatened species. Data on global trends are sparse, but what biologists do know paints a bleak picture of striking declines across taxa. Freshwater dragonflies, damselflies, mussels, fishes, amphibians, reptiles, birds, and mammals—all are suffering. To prevent a wave of irreversible extinctions and ecosystem collapses, people need to take better care of fragile freshwater habitats.

Fish in the Mekong River

Harmony Patricio, a conservation biologist and the conservation director at FISHBIO, told It has the second largest number of fish species of any river on earth, only after the Amazon River. More than 850 species have been described, and researchers estimate there could be over 1200 species. As a comparison, the whole state of California has about 67 freshwater fishes. The Mekong is also the most productive freshwater system on the planet in terms of fish biomass. The estimated annual harvest is over 2.6 million metric tonnes per year, which represents about 18 percent of the total global inland fishery harvests. That's almost 1/5 of all freshwater fish harvest across the world, found just in this one river basin. What's also special is how important the fish are for the people. There are over 60 million people that depend on the fish for protein and income, and the economic value of the fisheries is as much as $3.8 billion US dollars per year on first sale. So the river's fish are highly diverse, feed a lot of people, and are worth a lot of money. There are also some really unique and endemic species that you won't find anywhere else on earth. [Source: Jeremy Hance,, April 23, 2013 |~|]

“One obvious standout is the Mekong giant catfish (Pangasianodon gigas) because it is on record as the world's largest freshwater fish. It's like the blue whale of freshwater. It can grow to up to 3 meters long (9.8 feet), and weigh 350 kilograms (770 pounds). The giant catfish migrates long distances between several different countries, and is primarily vegetarian, which is unique for such a large fish. Another standout species would be the giant freshwater stingray, which can grow up to 2.4 meters long (7.8 feet) and 5 meters wide (16.5 feet), and weigh up to 240 kilograms (530 pounds). It's huge! |~|

“In addition to the stingray, there are other fishes you'd typically expect to find in the ocean, like electric eels and puffer fish. Some of the Pangasiid (a type of catfish) species are also really interesting. One, Pangasius krempfi, is believed to migrate to the ocean, and they have been seen along the coast of the South China Sea in Vietnam. They also migrate extensive distances, past Cambodia and over major waterfalls at the southern border of Lao, all the way up to northern Lao. The fact that they use both freshwater and saltwater and also migrate through the entire Lower Mekong Basin is pretty amazing. |~|

Mekong Giant Catfish

Mekong giant catfish

The Mekong giant catfish (Pangasianodon gigas) it is the world’s largest catfish fish and a candidate for the world’s largest freshwater fish. Reaching three meters (10 feet) in length and weighing almost 650 pounds (295 kilograms), its lives mainly in the lower half of the Mekong River system, in Cambodia, Laos, Thailand, and Vietnam.

The Mekong Giant Catfish, also known as the pla buk, is seriously endangered, a victim primarily of overfishing, It is so rare now that when ever one is caught by a fishermen it is big news. The remaining members of the fish species are found mostly in Cambodia and Laos. One of its primary breeding areas, a stretch of reefs near Chuang Khong in Thailand, is currently dredged for navigation purposes.

According to National Geographic: Mekong giant catfish have very low-set eyes and are silvery to dark gray on top and whitish to yellow on the bottom. They are toothless herbivores who live off the plants and algae in the river. Juveniles wear the characteristic catfish “whiskers,” called barbels, but these features shrink as they age. Average life span in the wild: More than 60 years. [Source: National Geographic website]

“Highly migratory creatures, giant catfish require large stretches of river for their seasonal journeys and specific environmental conditions in their spawning and breeding areas. They are thought to rear primarily in Cambodia’s Tonle Sap lake and migrate hundreds of miles north to spawning grounds in Thailand. Dams and human encroachment, however, have severely disrupted their lifecycle.

Giant Freshwater Stingray

The giant freshwater stingray is a species of stingray native to large rivers and estuaries of Southeast Asia. It is one of the largest freshwater fishes in the world, with reports from the Chao Phraya and Mekong Rivers of individuals weighing 500 to 600 kilograms (1,100 to 1,300 pounds). Its numbers are dwindling due to overfishing and habitat loss, and it is in danger of extinction. The smaller freshwater whipray of New Guinea and northern Australia was once considered to be conspecific with the giant freshwater stingray but is now recognised as a separate species. [Source: Wikipedia]

Freshwater giant stingrays are among the largest of the approximately 200 species of rays. They can be found in a handful of rivers in Southeast Asia and northern Australia. The giant freshwater stingray was originally described from Thailand (where it occurs in the Chao Phraya, Nan, Mekong, Bangpakong, Prachinburi and Tapi Rivers). The giant freshwater stingray is also found in Indonesia (the Mahakam River Basin in Kalimantan) and Malaysia (the Kinabatangan River in Sabah). There are also records from various other river systems in the region. It is not clear whether all these fish are a single species or are subspecies or are a species complex. Dr Terry Bertozi, of the Evolutionary Biology Unit of the South Australian Museum in Adelaide, Australia, and is collecting genetic samples to determine whether these are the same species of stingray found in the rivers of Northern Australia.

Mekong River Irrawaddy Dolphin

Irrawaddy dolphin

There are a few dozen freshwater dolphin — the Irrawaddy dolphin—living in the Mekong River. Harmony Patricio told The dolphin that has a lot of cultural significance.“People really honor the dolphin, and there are many stories about dolphins helping drowning people or helping fishermen to catch fish. So they never kill the dolphins.

The Mekong River Irrawaddy dolphin (Orcaella brevirostris) population inhabits a 190 kilometers stretch of the Mekong River between Cambodia and Laos. The latest population is estimated between 64 and 76 members (2008 figures). The Irrawaddy dolphin is identified by a bulging forehead, a short beak, and 12-19 teeth on each side of each jaw. The pectoral fin is broadly triangular. There is a small dorsal fin, on the posterior end of the back.

In 2004, the Irrawaddy dolphin was declared a protected species. Most are found around the Khone Falls area in the Mekong River along the Laos-Cambodia border. Some believe they will be extinct in less than 50 years. Many have been killed by gill nets and dynamite fishing used mostly by Cambodians. Some fishermen have purposely caught them for their teeth, which are regarded as talismans against evil spirits Today villagers are encouraged to participate in the tourism trade in the area and so they have reason to conserve the dolphins.

Khon Island near Siphandan (on the Mekong River north of the Cambodian border) is place where tourist gather to try and catch a glimpse of the river dolphins. They are most likely to be seen off the southern tip of the island in the early morning or late afternoon from December to May. The best spot of all is on Kham Island, a small sand island within Cambodian territory on the Mekong River. Boats make runs to this island for a small fee. Viewing the dolphins from boats isn’t really practical because the boats scare the dolphins off.

Dams and Conservation on the Mekong River

Jeremy Hance of wrote: “One of the most immediate threats" on the Mekong River "is the proposed construction of 77 dams on the river, including the controversial Xayaburi Dam, which Patricio says could interrupt the migration of the giant catfish. Considered the world's biggest freshwater fish, the giant catfish is listed as Critically Endangered and has largely vanished in recent decades. Despite it's incredible size, scientists still know little about the animal. "Overall, the cumulative effect [of dam construction] will probably be a reduction in the number of migratory species and a shift in the species composition to favor species that do well in reservoirs," says Patricio. "Right now, we know more than a third (38 percent) of the total Mekong fish harvest consists of migratory species. If the biomass of the reservoir species doesn't scale up to replace the migratory species, we could see a decline in total harvest or productivity." [Source: Jeremy Hance,, April 23, 2013 |~|]

“A new program by FISHBIO, headed by Patricio, is working to compile and disperse data on the freshwater fish across the region, including gathering information on harvesting. The Mekong Fish Network, as it's called, hopes to draft baseline data, so that information can be compared over regions and time.FISHBIO is a fisheries and environmental consulting company with offices in Chico and Oakdale, California, and Vientiane, Laos. The group is dedicated to advancing the research, monitoring, and conservation of fishes around the world. To support global conservation efforts, FISHBIO partners with international agencies, NGOs, and local communities to provide technical assistance and share expertise developed through years of experience with freshwater fish monitoring in California. FISHBIO has provided funding and resources for a number of conservation projects in the Mekong region, reflecting the company's mission to improve the study and sustainable management of fishes. [Source: Jeremy Hance,, April 23, 2013 |~|]

Patricio said:“The main goal of the Mekong Fish Network is to help people working with fish in the different countries of the Mekong Basin to collaborate across national borders and share information so we can better understand what's happening with Mekong fishes throughout the basin. These fish migrate between six different countries: China, Myanmar, Lao PDR, Thailand, Cambodia and Vietnam. These countries all speak different languages and have different cultures and government structures, but the fish don't abide by national borders. They use different parts of the river basin for different parts of their life cycle, so sustainably managing or conserving these fishes requires international cooperation." |~|

“Conservation has been a challenge since there is so much we don't know about the basic biology, life cycles, and ecology of the fishes. There needs to be more funding and more technical expertise made available to the region so this basic species information can be used to design conservation strategies. In a multinational region with migratory fish, conservation also has to work across borders. The fish move between different countries, so you really need the countries to agree to work together and conserve the fish at all the different stages of their life cycles. |~|

Impact of Dams on Mekong River Fish Species

Harmony Patricio told “The strategic environmental assessment for mainstem dams that was commissioned by the Mekong River Commission suggests that mainstem dams like the Xayaburi could block the migrations of some rare or economically valuable species. It could alter the species composition to favor fish species better adapted to a reservoir environment. The fish that can withstand lower oxygen levels or higher temperatures and can survive in a reservoir will do better than fish that need the free-flowing river environment or that are highly migratory. [Source: Jeremy Hance,, April 23, 2013 |~|]

“Also, no one knows for sure where the giant catfish spawns, but based on local ecological knowledge, people believe they spawn upstream of the Xayaburi Dam location. It would be a problem if the giant catfish can't make it past the dam, but they've already stopped showing up to these traditional spawning grounds—they've already been affected by changes to the river. Maybe they will be able to spawn somewhere downstream of the dam. The dam could also trap sediment that is very important for maintaining downstream habitat in the Mekong Delta in Vietnam. Ultimately, the Xayaburi is likely to have some impacts on fish, but there are plans for many other dams as well. |~|

“The impact is really going to depend on the development scenario: whether all of those dams are built in the locations where they're planned now, and how they're built. There are many alternative scenarios that could reduce impacts on fish and still generate a substantial amount of electricity. Overall, the cumulative effect will probably be a reduction in the number of migratory species and a shift in the species composition to favor species that do well in reservoirs. Right now, we know more than a third (38 percent) of the total Mekong fish harvest consists of migratory species. If the biomass of the reservoir species doesn't scale up to replace the migratory species, we could see a decline in total harvest or productivity. |~|

“The sediment trapping could reduce the productivity of the marine fishery off the coast of the delta and the delta itself could suffer land loss from erosion, which might affect rice production. People also talk about how dams will change the river's flow regime. Right now the Mekong has a very dynamic regime, extremely high flows in the rainy season, and very low flows in the dry season. This difference in flows is one reason why people think the river so productive. It causes the flooding of the Tonle Sap, creates floodplain habitat, and the potential for riverside gardens. A lot reservoirs and dams will reduce the variability of the flow regime. The dry season flows will be higher and the wet season flows might be a bit lower. There are a lot of questions about how this will affect the system. |~|

Image Sources: Wikimedia Commons

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Last updated April 2014

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