When water temperature reaches about 20°C and salinity levels are between 20-35 psu, synchronized spawning occurs. Sperm and egg are released at the same time through mutual stimulation and external fertilization occurs in the water (Minchin and Gollasch, 2008: 1; Pauley et al., 1988: 5). Females can release tens to hundreds of millions of eggs each year. Low success rates of these eggs are compensated by the long lifespan of the oysters (Padilla, 2010). Fertilization takes place within 10-15 hours of spawning (Nehring, 2006: 6).