Mekong Giant Catfish

One of the largest freshwater fish in the world, the Mekong Giant Catfish is a grey to white giant that can reach a length of 3 m. These massive creatures grow very fast, attaining a weight between 150 to 200 kg in just six years, with some reported to weigh as much as 350 kg. Adult specimens are distinguished by a near-total lack of barbels and an absence of teeth, features they lose as they grow beyond 50 cm in length.

Originally, this species spanned almost the entire 4,800 km length of the Mekong River, from China down to Vietnam. Today, they are mostly found in small, isolated groups in the middle Mekong region. They prefer the main river channel where the water is deeper than 10 m, though they also inhabit the Tonle Sap River and Lake in Cambodia. At the start of the rainy season, these fish congregate and travel hundreds of miles upstream to reach their spawning grounds.

While young fish eat zooplankton and sometimes each other, they become toothless herbivores after their first year. They primarily survive on filamentous algae and plants found on submerged rocks. This species now faces many dangers, including overfishing and the destruction of breeding grounds. Infrastructure projects like dams cause fragmentation that threatens larval fish and reduces the ability of adults to breed. Siltation and declining water quality also take a toll on the specific environmental conditions these migratory fish need to survive.