Belonidae is an extremely slender body, cylindrical or flat on its side, covered with tiny round scales. Both jaws are as slender as needles, the upper jaw is slightly shorter, the teeth on both sides are fine, and there is a row of sparse canine teeth on the outside. The scales are small, the lateral line is close to the abdominal edge, and it becomes a raised ridge on both sides of the tail stalk. The dorsal fin and the anal fin are relative to the back of the body. The dorsal fin usually has 1 1-26 soft strips, up to 43, and there is no free fin on the back. The pectoral fin and ventral fin are short; The caudal fin is bifurcated, truncated or obtuse. There are 32 species (Nelson, 1994) belonging to the genus 10, of which about 1 1 species live in freshwater areas. Most of the surface migratory fish belonging to warm tropical waters live in the ocean, but some of them live in tropical fresh water or brackish water areas. The body color is similar to that of general migratory fish, with a typical blue-black back and a silvery-white abdomen. Most of them swim in groups in the open sea, and a few swim in groups or alone to the coast. It's carnivorous, catching sand by hunting? Or eat whitebait. When frightened, it will jump out of the water like a flying fish, and it can slide for a distance by hitting the water with its tail fin. Eggs are large and round, usually laid on floating seaweed fragments, driftwood or dead leaves. Widely distributed in temperate to tropical waters, as well as fresh water areas in South America, Pakistan, India and Southeast Asian countries.