As the oysters begin to spawn they are segregated by sex into small bowls. After 20 or 30 minutes, the oysters are removed and a small amount of sperm is mixed with the eggs. A single female may produce several million eggs. The fertilized eggs are placed in larger aerated tanks where they will develop into swimming larvae in 24 to 48 hours. The larvae are fed either cultured algae or wild algae from filtered seawater.
Cultured algae is more reliable but requires special equipment and experience.
As the larvae grow they are moved from one tank to another every few days by sieving. After 10 to 14 days, the larvae have reached the eyed larvae stage and are ready for setting. The finely ground shell is referred to as microcultch , and the subsequent single oysters are called cultchless oysters since they do not appear to be attached to anything. Larvae set on whole shell will eventually form clumps and are similar to oysters found on natural reefs. Eyed larvae can be kept in the refrigerator for several days, which means that eyed larvae can also be shipped on ice to farmers who then set the larvae themselves.