To culture pearls Mikimoto developed a technique of nucleation. Once they'd been nucleated, the oysters were caged and suspended from rafts and left to grow for four years, to produce a thick coating of nacre. Japanese pearl farmers are struggling with many modern day problems. Changing weather patterns and pollution shorten the life spans of the oysters. After 100 years of continuous pearl culturing the Akoya oyster is under assault.
Oysters require clean water to produce good pearls.
So, you need, as the farmer, to put that oyster basket into good water. And that's virtually unattainable in an industrialized country like Japan.