Spawning occurs near the surface, and eggs float freely until they hatch after 5-6 days. When larvae reach 2-4 cm, they form groups and start swimming in schools. Sprat have a relatively a short life cycle; populations are dominated by 1-2 year-olds. In years with fast growth, fry can be recruited to the catch by the fourth quarter. They are preferred prey items sought after as food by many other species.
To understand the ecosystem dynamics, it is important to determine the abundance of sprat necessary to sustain populations of other species (fish, seabirds). Major portions of the population are found in central and southeastern areas of the North Sea. In the Skagerrak sprat are found in areas close to shore, and in fjords on the coasts of Sweden and Norway.
Analysis of microsatellite DNA of sprat in the North East Atlantic revealed that Baltic Sea and the North Sea sprat were genetic different from the sprat in the Norwegian fjord. Here small differences were found, though not significant differences. They spawn locally, but are believed to be recruited from spawning areas in Skagerrak / North Sea.