Mekong giant catfish are toothless as adults - which is surprising for such a large creature. They eat mostly algae and plant matter that grows on the riverbed. Despite having no teeth and being herbivores, they can grow to extraordinary sizes on this plant diet.
The fish have whisker-like 'barbels' around their mouth, which is how catfish get their name. These barbels sense vibrations and chemicals in the water, helping the fish navigate the muddy, dark depths of the Mekong where light doesn't reach.
They are famous for being difficult to study because they live in deep, murky water and can swim huge distances upriver to breed. Scientists believe they migrate from the lower Mekong in Cambodia all the way up to deep pools in northern Thailand and Laos to spawn - a journey of thousands of kilometres.
Cambodian fishermen once caught these fish in large numbers in the Tonle Sap lake, and they were an important part of the local food supply. Today they are protected, and the focus has shifted to tagging and releasing the fish so scientists can track where they go.