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Generalized life cycle of the Pacific oyster: Male and female oysters spawn in late July to early August. Spawning may not occur every year. Sex reversal may occur from year to year. Mass fertilization occurs in water column, within 15 hours of spawning. Fertilized eggs develop within 24 hours into ciliated, motile larvae. Larvae drift in plankton for 3-4 weeks, but retain position in the upper 4 m of water column. At 0.3 mm size larvae settle and attach the left valve to a solid, clean substrate using excreted cement, referred to as spatting. At approximately 25 mm the spat or juvenile oyster is referred to as "seed". Oysters remain fixed to substrate for life. Adults live to over 20 yr and reach a maximum shell length of over 30 cm.