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Generalized life cycle of the red sea urchin: Males and females generally spawn from June to September, peaking in July, but spawning periods vary from area to area. Mass fertilization occurs in water column. Fertilized eggs develop into free-swimming larvae or nauplii which drift and feed in plankton. After 6-8 weeks, larvae settle and develop into juvenile sea urchins. Often they seek aggregations of adults and remain under spines until they reach test diameter of 40 mm. Sea urchins are very vulnerable to predation between 50-80 mm. Sea urchins usually aggregate in areas where food is plentiful, with the preferred food being giant or bull kelp. Adult urchins may reach 180 mm and live to be over 7-10 years old.