2. The giant catfish (Pangasianodon gigas) in Mekong River is one of the large freshwater fishes of Siluriformes. The largest individual is 2.5-3 meters long and weighs 200-300 kilograms. Back bulge, flat body side, forked tail. The head is big and flat, the kiss is dull, the mouth is long, and the teeth and gill rakes exist when it is difficult to fish, but disappear when it is adult. The maxillary bone and mandibular tentacles of juvenile fish are well developed, but the mandibular tentacles become underdeveloped in sub-adult fish and adult fish, leaving only maxillary whiskers 1 pair. The eyes are small, and their height is lower than the mouth angle. Dorsal fin 1 piece. Posterior part 1 small lipid fin. The pectoral fin is small. The base of gluteal fin is long. Tail fin fork. The back is dark gray, the abdomen is silvery white, the fins are brown, and the body has no markings. Dorsal fin Ⅱ, 7-8; Anal fin 35; Vertebra 48.
3. Giant toothless perches on the bottom of rivers, especially on rocks and gravel bottoms, and sometimes perches in underwater caves. It mainly feeds on aquatic plants and algae, and is omnivorous. The Mekong River, which originated in Viet Nam, Cambodia, Laos and Thailand, has also appeared in the Mekong River basin in Myanmar and southwest China. In Thailand, it has been introduced into reservoirs and rivers, but failed to establish a population. China introduced it to Thailand in 1986 for trial breeding in the south.