1, maximum size of Hucho taimen: the maximum weight of an adult is about 50 kg, and it is about 2 meters long. Habitat: There are five species in the world, which are distributed in the Danube River basin in northern Asia and Europe. 2. The maximum size of the Mekong giant catfish is 1 18 inch (300 cm). 66 1.4 lb (about 300 kg) Habitat: Mekong River, Southeast Asia 3. Maximum size of the Mississippi paddlefish: 87 inches (about 22 1 cm) together with the head bone plate Habitat: Mississippi River, North America 4. Maximum size of the European giant catfish: 197 inches. 675 pounds (about 306 kilograms) Habitat: Widely distributed in Europe and Asia. 5. Maximum size of alligator eel: 120 inches (about 305 centimeters), 300 pounds (about 136 kilograms) Habitat: Mississippi River, North America, 6. Nile perch: 79 inches (about 20 centimeters) 44 1 lb (about 200 kg) Habitat: Nile Valley in Africa 7. Maximum size of giant freshwater stingray: 197 inch (about 500 cm), 1323 lb (about 600 kg), Habitat with a body length of 95 inches (about 240 cm) without tail: Mekong River, Southeast Asia 8. Maximum size of giant tongue fish: 177 inch (about 450 cm), 44 1 pound (about 200 kg) Habitat: Amazon River basin in South America 9. Maximum size of Australian freshwater cod: 79 inch. 250 lbs (about 1 13.5 kg) Habitat: Australia's Murray River 10, Siamese giant carp's maximum size: 1 18 inches (about 300 cm), 661.