There is actually not really much known about the legendary Giant Catfish, who is at home in the Mekong River. In the old days, what is here not so long ago, some decades only, the Giant Catfish lived in the whole of the 4,800km long Mekong River, in some of it's tributaries and in the Tonle Sap (River) and Tonle Sap Lake.
Due to overfishing, pollution and the construction of the first four dams in China, the biggest sweetwater fish on earth is nowadays critically endangered. Very vew individuals are still observed or fished. They retreated mostly in the parts of the Mekong between Houayxay and Vientiane in Laos or in the Tonle Sap River and Tonle Sap Lake in Cambodia. In the middle of the majestic river, where the depths reach more than 10m, some fish still survived. There are only a few, isolated populations left. But, probably soon none is left. It's estimated that the population has been fallen by 80 % in the fourteen years between 1997 and 2011. There are probably not more than 2,500 individuals still living, rather much less.
It's probable that the Giant Catfish is moving annually over thousands of kilometers riverupwards from central and north Cambodia up to north Thailand, where the females lay their eggs. These eggs reach numbers between 500.000 and 2.000.000, about 13kg to 14kg. The hatched individuals are then using the flow riverdownstreams to spread out over the middle and lower sections of the river.
The Giant Mekong Catfish is a day-active species who prefers to stay in deeper areas of the river except in nighttime, when he comes closer to the surface and the riverbanks.
Since 1967 Giant Catfish are bred in Thailand in reservoirs or aquariums. One of the breeding stations was in Chiang Khong, but it's abondend there since at least seven years (I found it closed already in early 2007). Artificially bred Giant Catfish was brought into the Chao Phraya River in central Thailand, but it didn't succeed to found a new population.
The fish lives mostly from plants. Catfish are generally known for searching the grounds of muddy waters and eating plants, algaes, rotting plants and animal remains on the grounds. Much of what they do is scavenging. Adults are almost exclusively plant eaters. Common catfish appear in a great variety and most different sizes in Southeast Asia. They are an often seen fish on any freshmarket in Thailand where freshwater fish is sold.
The deepest sites in the Mekong River are as deep as 80m. These spots are great hideouts for larger fish. It's interesting that there are still many species living in and around the large river who are yet unknown for science. In 2015, WWF published a brochure in which a larger number of newly discovered animals of the Mekong are introduced.
The Giant Mekong Catfish grow up to more than 3m in length and can gain a weight of over 300kg. They are a very fast growing species and gain quickly weight and size in their young age. It's supposed they are the greatest freshwaterfish on earth. But there are others as well. For example in the Oder River, which marks nowadays the border between Germany and Poland, there are catfish of the same size living, up to 3m. Maybe they weight a bit less, but they are about the same size as the Mekong catfish.
Chiang Khong's Catfish Aquarium
Chiang Khong has a remarkable Catfish Aquarium at the river banks of the Mekong in town. Here were Giant Catfish bred the first time. But the project might haven't been really successfull. I heared rumours about an official project in the past, when the authorities bred young Giant Catfish and released them into the Mekong at Chiang Khong. News went around quickly and the local fishermen did what they could to immediately catch the young fish for their businesses.
Nowadays, the aquarium is an empty place. It looks still quite tidy, undamaged and basically in a good shape. Maybe it will be revived once? Could be it will reopen when the new Mekong River bridge is completed.
Not only the Giant Catfish is endangered in the Mekong River, but the whole ecology in an huge catchment area. There is a great dam under construction some 30km away from Sanyabury in Laos. Here you get more on 'Damming the Mekong'.