This work evaluated the spawning of sea urchin Lytechinus variegates based on lunar cycle and population characteristics. Eight monthly collections were realized to estimate the gonadosomatic index (GI) and population parameters regarding reproduction. To evaluate the effect of the lunar cycle on spawning, samples were taken for each moon phase of three lunar cycles. In the entire work 295 individuals were collected, 156 males and 131 females (1.19:1 ratio). However, there was no significant difference in the sex ratio of the population. The weight of males was significantly greater than that of females. There were no differences between males and females in gonadosomatic index (GI), gonad weight and diameter. There was an effect of the lunar periodicity on spawning, with lower GI in new moon, indicating that spawning occurs on the first lunar quarter in spring tide.
