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Episode 322: Monster Mekong Giant Catfish

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The magnificent Mekong Catfish (image from https://a-z-animals.com/)

Part of the shark catfish family, the Mekong Catfish is one of the largest freshwater in the world, with some individuals hitting the t at as much as 395kg. Once abundant, the catfish today has faced catastrophic population crashes, and is now a very, very rare sight. They can only be found in the main streams of the lower Mekong River Delta that spreads throughout Mynamar, Lao PDR, Thailand, Cambodia and Vietnam.

Scientists know very little about the species, with their migratory patterns and spawning ground locations poorly understood. Studies have shown that they start life as tiny little fry, during which time they cannibalise their fellow fry and also feed on zooplankton. They grow incredibly quickly and once they have matured, they spend their life peacefully cruising through the riverways, munching on filamentous algae growing on submerged rocks. They are well suited for their herbivorous lifestyle, as unlike a lot of other species of catfish, they have no teeth!

Giants in a Jam: the plight of the Mekong Catfish

The vast and biodiverse Mekong delta (image from Mongabay news.mongabay.com)

In the last decade, Mekong catfish are suspected to have decreased in number by 90%, although no one has ever managed to get accurate numbers from the Vast Mekong River Delta. There are concerns there may be as few as hundred left in the wild. Although they can be extensively fished, the biggest threat facing the Mekong catfish is the intense development of infrastructure throughout the Mekong River. In particular, dams are a huge threat. Although essential for the provision of water to local communities, the indiscriminate building of dams in certain parts of the Mekong River is affecting the migration routes and suspected spawning grounds of this endangered fish. Additionally, dams can also isolate populations from each other, preventing them from breeding and keeping healthy flow of genes for good genetic diversity. These plans to dam large regions of the Mekong River will seriously threaten this catfish, blocking the last free flowing river they exist in.

One of the mega dams that is threatening the Mekong River and its biodiversity. Balancing the needs of the people in the region with ensuring robust biodiversity is a challenge. (image from the Japan Times)

Conservation Optimism

Although the Mekong Catfish is an underappreciated species and often not well known, concerns for their future have reached the World Wildlife Fund, who use the catfish as a flagship species for their Living Mekong Programme. This project aims to secure the future of the Mekong River, both for humans and wildlife.

Recently, scientists have also utilized eDNA, which is the detection and sequencing of DNA from the environment which enables scientists to accurately determine what species are in the area. This is particularly challenging in freshwater, where DNA can degrade very rapidly, but scientists had some success trialing this in Thai reservoirs, and have been able to roll this technique out in the wider Mekong Delta.

Scientists at the Nongkhai Inland Fisheries Research and Development Centre tagging Mekong Giant Catfish being raised at the centre for release into the wild to try and safeguard the future of this incredible fish (image from fishbio.com)

The Mekong Catfish is not the only species that is under the attention of the WWF. The Mekong River delta and the surrounding land is home to amazing threatened species like the Irrawaddy Dolphin, Asian Elephants and the Soala Antelope, to name but a few. The incredible biomes on the Mekong River also support the livelihoods and food supplies of millions of people, with 25% of all freshwater fish caught fished from the waters of the Mekong. As part of their conservation project, the WWF works both on the ground in practical conservation, surveying populations and helping local communities protect their resources, and also get involved in policy changes, setting up sustainable and legal forest supply chains and collaborating with governments to develop more efficient and less destructive dams. Alongside the Living Mekong Programme, the WWF also run the Voices for Mekong Forest project, which is a forest governance system empowering small businesses and land holders to adopt forest production certificates, which helps them gain a foothold in the international market. You can check out these amazing projects from the WWF at Mekong River | Greater Mekong | Places | WWF (worldwildlife.org)

Awesome videos!


Bellemain, E. Harmony, P. Thomas, G. Francois, G. Alice, V. Claude, M. and Tony, D. (2016) ‘Trials of river monsters: detecting critically endangered Mekong Giant Catfish Pangasianodon gigas using environmental DNA.’ Global Ecology and Conservation

Hogan, Z.S. Moyle, P.B. May, B. Vander Zanden, M.J. and Baird, I.G. (2004) ‘The imperiled giants of the Mekong: ecologists struggle to understand and protect Southeast Asia’s large migratory catfish.’ American Scientist

Sun, J. Du, W. Lucas, M.C. Ding, C. Chen, J. Tao, J. and He, D. (2023) ‘River fragmentation and barrier impacts on fishes have been greatly underestimated in the upper Mekong River.’ Journal of Cleaner Production

Yamagishi, Y. Miromichi, M. Yasushi, M. Nobuaki, A. Khacha, M and Thavee, V. (2004) ‘Study on feeding habits of Mekong giant catfish in Mae Peum Reservoir, Thailand

Mekong giant catfish, facts and photos (nationalgeographic.com)

Mekong giant catfish | WWF (panda.org)

Inside the plan to save some of the biggest freshwater fish | National Geographic


May 10, 2023
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