Abalone are relatively slow growing. Tagging studies indicate northern California red abalone take about 12 years to reach 7 inches but growth rates are highly variable. Abalone grow nearly one inch per year for the first few years and much more slowly after that. It takes about 5 years for red abalone to grow from 7 inches to 8 inches. At 8 inches, growth rates are so slow it takes about 13 years to grow another inch. Slow growth makes abalone populations vulnerable to overfishing since many years are needed to replace each abalone taken.