Breeding stock is regularly collected by divers from the wild and forms the basis of the hatchery operations and maintaining genetic diversity. Female abalone can produce in more than 1 million eggs per spawning period. Fertilisation leads to planktonic larvae that feed on their own energy stores.
Within a day of fertilisation the planktonic larvae hatch. These larvae feed on their own energy stores. About one week later the larvae settle onto specially prepared plates,covered with cultured diatoms, and metamorphose. Although juvenile abalone, called 'spat', are still vulnerable, careful growing can result in up to 90% survival over the next 3-6 months.
The spat spend from 8 to 12 months in the settlement tanks, until they grow to a length between 10 to 15mm. At the end of this time transferred to grow-out tanks.
Most grow-out tanks are raceways or circular tanks These tanks are usually shallow and made from strong black plastic. They are often covered with greenhouse mesh to stop predators and provide shelter for the abalone. Seawater is pumped from the sea then through a sand filter before being pumped continuously through the tanks. The abalone grow quickly in the fast-flowing water provided by these flow-through systems. Most abalone are harvested at the end of their third year when they have reached a size of about 70 mm or 50g.
Most land based abalone farms are 24-hour operations involving continuous monitoring of the water systems and the stock. Any interruption to the water supply and water temperature can be disastrous with large-scale losses of abalone.
Also see www.lib.noaa.gov/retiredsites/korea/main_species/abalone.htm