© Fish Bio
The Mekong's Forgotten Fishes
Mekong fishes, vital for tens of millions of people and health of the Mekong river system, are on the brink— with one fifth facing extinction, warns a new report

Mekong's Forgotten Fishes, a new report published by WWF and 25 local, regional and global Mekong-based organizations, details the extraordinary variety of fish species in the Mekong river. These dazzlingly diverse fishes are critical for the health, food security and livelihoods of tens of millions people across the region as well as the overall health of the river system, but they are under ever increasing pressure with one in five already threatened with extinction. 

The report details the extraordinary variety of fish species in the river – with at least 1,148 making the Mekong the third most biodiverse river after the Amazon and Congo. The Mekong is also home to one of the largest migrations on Earth in terms of numbers of animals, with an estimated 5 billion fishes on the move.

The report also highlights the critical role of all these fishes in maintaining the health of the Mekong River Basin and supporting societies and economies across the region. The Mekong boasts the world’s largest inland fishery, which accounts for over 15 per cent of the entire global inland catch, generates over US$11 billion annually, and is central to the food security and livelihoods of over 40 million people in communities across the basin.

But the Mekong’s fishes continue to be undervalued and overlooked by decision makers and at least 19 per cent of assessed species are now estimated to be heading towards extinction, with 18 species already listed as Critically Endangered by the IUCN Red List of Threatened Species. However, a staggering 38 per cent of species are considered Data Deficient, meaning too little is known about them to gauge their conservation status – and that the number of threatened species is likely far higher.

An unprecedented combination of threats is driving the decline in the Mekong’s fishes, including habitat loss, hydropower dams, conversion of wetlands for agriculture and aquaculture, unsustainable sand mining, invasive species – and the worsening impacts of climate change. Together, these threats are devastating fishes and fisheries with fish populations in Tonle Sap collapsing by 88 per cent between 2003-2019 and an estimated one-third fall in the economic value of the Mekong fishery between 2015-2020.

Urgent action is needed to reverse this alarming trend. Along with protecting and restoring freshwater ecosystems, Mekong countries should implement a transboundary Emergency Recovery Plan for Freshwater Biodiversity. This comprehensive 6-pillar plan, which includes letting rivers flow more naturally, improving water quality, and ending unsustainable exploitation of resources, can deliver solutions at the scale necessary to reverse the collapse in Mekong fish populations. Critically, local fishers and communities possess knowledge, expertise and solutions — such as community Fish Conservation Zones — that have demonstrated success and which we can build on to help safeguard their fish and their river. However, local communities cannot safeguard the whole Mekong on their own — decision makers need to factor in Mekong fishes and scale-up effective actions to restore the health of the river and the invaluable life below its surface.

Full Report

The report celebrates the Mekong's wealth of species diversity – from the world’s most massive freshwater fish to one of its most minute, from fishes that ‘talk’ and ‘walk’ to fishes that spit water to knock unsuspecting prey into the river.

Giant Freshwater Stingray

Urogymnus chaophraya. Endangered. This elusive giant is the largest freshwater fish ever recorded, weighing up to 300 kg — the weight of an average vending machine. Little is known about this species and more information is urgently needed so that conservation activities can be prioritized.

Giant Mekong Catfish

Pangasianodon gigas. Critically Endangered. This iconic freshwater giant, endemic to the Mekong river and considered sacred across communities, was once abundant in the region. Today, evidence indicates that species numbers have fallen by at least 80% since the 1980s.

Sultan Fish

Leptobarbrus rubipinna. Data Deficient. This migratory species, which is known in Thai as 'Pla ba' (translates to 'mad fish'), sometimes gorges on the seeds of fruits that can cause delirium if eaten. Historically, local communities in Lao PDR know when the sultan fish are on their way from their seasonal home in Thailand because another fish, the Pa sieu, makes a noise like crickets, which signals the sultan fish’s arrival.

Giant Gourami

Osphronemus goramy. Least Concern. The Giant gourami is among several gourami species found in the Mekong river. These striking fish continue to draw global popularity for their unique features, generating profit in growing industries such as the aquarium trade and the recreational angling sector. In their natural environment, these fish have been known to grow to a length of up to two feet.

Giant snakehead

Channa micropeltes. Least Concern. Snakeheads are ambush predators whose adapted gills allow them to breathe air. The colourful giant snakehead can grow to nearly 1 metre. Armed with razor sharp teeth, this fish feeds on other fishes and small crustaceans. Highly protective of their offspring, they are known to guard their fry until they reach about 5 cm in length. 

Long-snouted pipefish

Doryichthys boaja. Data Deficient. This unexpected Mekong fish is a relative of the seahorse. It holds the title of the world’s largest freshwater pipefish species, growing just over 40 cm long. Just like seahorses, this fish is ovoviparous, meaning males carry eggs before giving birth to live young. But sadly, little is known about this species and it is rarely seen. 

Croaking Gourami

Trichopsis Schalleri. Least Concern. Amazingly, this beautiful fish can talk. Like other close relatives, the species can produce audible sounds via specialized pectoral fins, whose tendons and muscles are stretched and plucked by the anterior fin rays as if they were guitar strings. Studies suggest that they transmit ‘croaking’ signals to settle conflict and ‘purring’ sounds to initiate spawning.

Jullien’s golden carp

Probarbus jullieni. Critically endangered. This migratory Mekong giant can weigh up to 70 kg and nearly 5 metres long. Although they have a long lifespan, ranging up to 50 years, and were once widely consumed across the Mekong river basin, this fish has faced troubling population declines and has been rarely recorded. 


Probarbus jullieni

Asian Arowana

Scleropages formosus. Endangered. Also called the dragonfish, the stunning Asian arowana is believed to bring good luck and fortune. Demand for this species in the aquarium trade is high, and depending on their colour and size, individuals can sell for huge sums – but it is estimated to have declined by between 50-90% across its range, with unsustainable harvest for the pet trade being a primary cause.

Mekong fighting fish

Betta smaragdina. Data Deficient. Also called the emerald fighting fish, the Mekong fighting fish, is one of the most famous of the Mekong’s aquarium fishes, and arguably one of the most beautiful fishes in the world. Native to Lower Mekong Basin, it’s found in the domestic and specialist international pet trade and is also used for game fighting. Little is known about its status in the wild. 

Giant barb

Catlocarpio siamensis. Critically Endangered. Weighing up to 300 kg, the revered Giant barb is considered sacred for many communities across the Mekong, particularly in Cambodia where it is believed that killing this fish can bring curses to families. As Cambodia’s national fish, there are large statues of the Giant barb throughout the country. But the species faces extinction and is rarely recorded in areas where they were once abundant.

Hillstream Loach species

Sewellia breviventralis, Critically Endangered. This hillstream loach species lives in the fast flowing streams of the Sesan river basin, which forms part of the Mekong. Like other hillstream loach species they have evolved adaptations such as sucker mouths, flattened bodies and adapted fins, which help them cling onto rocks in the current. This species are particularly vulnerable to threats like pollution or changes to the flow of rivers and streams due to hydropower development. This image is of Sewellia lineolata - a close relative of Sewellia breviventralis.

At approximately 4,900km in length, the Mekong is the longest river in Southeast Asia, and the 8th longest in the world. The Upper Mekong River Basin begins in China and comprises the Tibetan Plateau and Three Rivers Area, and the Lancang Basin in both China and Myanmar. Meanwhile, the Lower Mekong River Basin drains a catchment of around 571,000km2, covering a large part of north-eastern Thailand, most of Lao PDR and Cambodia, and the southern tip of Viet Nam.

© Adam Oswell / WWF-Laos

© Adam Oswell / WWF-Greater Mekong


Lan Mercado, Regional Director, WWF Asia-Pacific

“The alarming decline in fish populations in the Mekong is an urgent wake-up call for action to save these extraordinary – and extraordinarily important – species, which underpin not only the region’s societies and economies but also the health of the Mekong’s freshwater ecosystems. These fishes have swum through our civilizations and cultures for millenia and millions of people still depend on them every day. But overlooked by decision makers, they are disappearing. We must act now to reverse this disastrous trend because the communities and countries of the Mekong cannot afford to lose them.” 


© Zeb Hogan


Zeb Hogan, Lead, Wonders of the Mekong

“The good news is that it’s not too late to restore the Mekong and bring its fishes back from the brink,” said Zeb Hogan, Lead for Wonders of the Mekong, which funded the report. “By factoring the future of fishes and fisheries into decisions that impact the basin while building on the expertise, knowledge and solutions of local communities, we can chart a new course for the Mekong – securing food and jobs for millions, safeguarding cultural icons, boosting biodiversity and enhancing resilience to climate change.”


© Daiju Azuma


Kathy Hughes, Freshwater Biodiversity Lead, WWF Asia-Pacific

“Local fishers and communities have shown that there is hope. Together, we can scale up their solutions. We can protect and restore the Mekong, and use it sustainably for the benefit of societies and economies now and in the future – a future in which the river’s extraordinary freshwater fishes survive and thrive. Reversing decades of decline will be hard but it’s possible – if we act collectively and urgently."


© WWF-Greater Mekong


Loris Palentini, Country Director, WWF-Laos

"In Lao PDR, where Mekong fishes contribute 13 per cent of the country's GDP, we need to do more to protect the Mekong river's invaluable biodiversity. The impacts are visible across the country — from the communities we work with reporting unprecedented losses of fish catch every year, to the national extinction of freshwater dolphins in Lao PDR in early 2023. But there are signs of hope, which show Laos’ capacity to influence change: the forthcoming updated national law on aquatic and fisheries, with improved fisheries management approaches, as well as the successes of community-led Fish Conservation Zones are steps in the right direction. By scaling up successful actions and addressing these drivers of loss, we can restore the health of the river and all life below its surface, while contributing to sustainable development, food security, and poverty alleviation."


Report cover