Adult male crabs average 143-149 mm in carapace width and 1.7-2.4 lb in weight. Females are considerably smaller, averaging 102 mm in width and 0.6-0.8 lb in weight. Average size of adults and juveniles decreases with greater depth.
Molting probably takes place in late summer - fall. Most females cease to molt after the puberty molt. Adult males may not molt every year. The mean carapace width increase after molting for juvenile crabs was calculated to be 26.14%.
Minimum size at maturity is approximately 118 mm carapace width for males and 85 mm for females. Age at maturity is predicted to be 5-6 years.
Adult males migrate to deeper waters in the fall and winter, presumably for mating. Tanner crabs are probably polygamous i.e. a single crab will mate with more than one individual. Eggs are carried by the female for almost a year and hatch in the next winter specially between January to March just before the next batch of eggs are ovulated and then fertilized. Larvae are planktonic near the sea surface for approximately of 80 days. During this planktonic phase, surface currents are mostly directed offshore. Consequently, when the larvae settle to the bottom, they are distributed at greater depths. Young crab then migrate to shallower depths as growth proceeds.
The Tanner crabs are probably food generalists, opportunistic, and sometimes cannibalistic.