The spring fish is dioecious, but the male fish is hard to find. It can lay eggs all year round, belonging to a transgender variety, and its male and female organs can change with the environment.

Spring fish is a deep-sea fish native to Japan, belonging to Cucurbitaceae. Duochun fish, also known as hairy scale fish and cucurbit fish, is named "Duochun" because there are many fish eggs in the belly of female fish (eggs and eggs are called "Spring" in Hakka dialect in southern China). They include Shishamo, which is produced in Takekawa-CHO, Yongfu County, Hokkaido, Japan, capelin, which is called "Japanese willow fish" in Iceland, and Longfin smelt or Hairscale fish, which are produced in the Pacific coast of Canada and the United States. The spring fish is elongated, with a flat side, about15-23 cm long. Big eyes and small scales. The dorsal fin is in the middle, the lipid fin is low and long, and the gluteal fin is located behind and below the dorsal fin.