Arapaima (scientific name: Arapaima gigas): It is a species of Arapaima, Osteoglossi, Actinopterygii, also known as walrus fish. Adult fish can reach 2-6 meters in length and weigh up to 100 kilograms. It has a huge, long, and slightly flattened body. The head skeleton is composed of free plate-like bones. The mouth is large and has no whiskers. There is no mandible, and there are strong and developed teeth on the tongue. The swim bladder is surrounded by rich blood vessels, the inner surface is honeycomb-shaped, and there are often special branchial organs. The scales are large and hard, inlaid. The dorsal fin and anal fin are located at the back of the body, opposite to each other. The pectoral fins are low. The pelvic fins are behind the abdomen. The tail fin is round. The body is gray-green, the back is dark, the abdomen is lighter, and the tail fin and the back of the body are red.

Gar is a general term for large fish of the genus Lepisosteus in the family Lepisosteidae, found in North America or Central America. It is closely related to bowfin fish and belongs to the order Holostei. It mainly lives in fresh water, but some species can enter brackish water or even salt water. It has sharp teeth and is a large, ferocious fish that is carnivorous. Gar meat is edible, but its eggs are poisonous. In Shanghai, Chongqing, Shaoguan and other places in China, gar, as an alien invasive species, poses a great threat to other local fish and may destroy the local ecosystem.