California Sea Grant College Program

Sea urchins are what are known as “broadcast spawners.” Adults release their gametes into seawater, and fertilization occurs if there is a high enough density of gametes to ensure that female and male gametes meet. What happens after fertilization is something of a mystery. Scientists do not, for instance, know how far, on average, larvae travel during the six-week period it takes for them to develop and settle onto the seafloor. And, they do not know the degree to which ocean waves and currents mix larvae originating from different geographic locales.