Have you read up on the life cycle of mollusks? This reproductive cycle must be maintained within the cultured pearl industry so pearl farmers have mollusks to nucleate to create pearls. So, how old do mollusks need to be to create pearls?
Remember that, in nature, a foreign substance or bacteria invading a mollusks can be traumatic and can lead to death. Truthfully, the same is true with cultured pearls. The insertion of a nucleus into a mussel or oyster can lead to death as well. One way to prevent this premature death is to ensure a mollusk is old enough to handle being cultured.
So, how old do mollusks need to be to create pearls? A lot of it depends on the species. Freshwater mussels in China are typically between 6 months to one year old before they are nucleated. They then spend anywhere between two and seven years producing pearls. In the Philippines, the gold-lipped oyster is two years old before it is nucleated. So, you can see the difference based on the species.
Most pearl farms either run their own hatcheries for the the reproduction and growth of these Chinese freshwater mussels or they purchase mussels from independent hatcheries. Read more about cultured pearls and fish...