Young fish move inshore and congregate into schools near the beach. They can reach 16 in-ches, but are usually less than 12 in. There is a good deal of regional variation in growth rates, with average size increasing from south to north. In the Pacific northwest, sardine will reach 215 mm after four year and 235 mm after five years. Females will grow faster than males.
Some individuals mature in their first year, most in their second.
Maximum age 13-25 years, most are less than 8 years. Size and age at maturity may decline with decrease in biomass. All sizes of sardines are food for a large variety of marine birds, fishes, and mammals. Sardines may become more important as prey for many species as the sardine resource continues to increase. The northern subpopulation of sardine has made extensive migration, moving north to British Columbia in early summer and back to southern California in the fall and winter.