Adults enter fresh water and spawn from February to mid-May. Typically, males enter the rivers first, followed shortly by the females. Most spawning eulachon are three years old though they can live up to five years. Spawning is done in large masses and usually during the night. The females' eggs and the males' sperm are dispersed together into the water column and the fertilized eggs quickly attach to gravel, wood or the sandy bottom of rivers.
Most adults die shortly after spawning.
The 7,000 to 60,000 eggs per female hatch in five to six weeks. Because of its small size the larval eulachon are rapidly swept downstream and out into the estuaries and open ocean. Northern California to the eastern Bering Sea and the Pribilof Islands. All life stages of the eulachon feed primarily on plankton. The eulachon play an important role as prey or food for other animals.