Anchovies are slender, with a flat back and a very beautiful tail. There are great differences in body shape and color between male and female fish. The male fish is thin and thin, with a body length of 4-5 cm. The dorsal fin is long and pointed, the caudal fin is wide and long, accounting for more than half of the total length, and the caudal stalk is longer than the caudal stalk. According to the shape of its tail fin, it can be divided into early tail, lower sword tail, double sword tail, piano tail, needle tail, round tail, flag tail, fan tail, triangular tail, cut tail, pointed tail and big tail. Its body, dorsal fin and caudal fin are colorful, mainly including red, blue, black, yellow, green, tiger skin and variegated colors. Some male fish have small blue-black spots on their tails, like peacock's tail feathers, hence the name. The female fish is stout: the body length can reach about 7 cm, the body color is dim, fleshy and slightly transparent, and the color of dorsal fin and caudal fin is much inferior to that of male fish.