PEARL CULTIVATION

The art of pearl cultivation is a long and delicate process. Man had been trying to unlock the secret of the pearl's beauty as far back as 1000 BC, but it wasn't until the early 1900's that Kokichi Mikimoto successfully grew a pearl. There are two main cultivation processes known Nucleated Cultivation and Non-Nucleated Cultivation, used for saltwater and freshwater pearls respectively. The Nucleated Cultivation process is used in Australia. Australian pearls are formed in the following way.
The Gathering of the Oyster Shell The process of culturing pearls begins at sea. Australian oysters are not yet conceived on farms; young oysters must be found in the wild and collected by divers on the sea bottom off Australia's north west coast.
The oysters are gathered with the aid of the pearl boat, which serves as the divers' platform and transports several thousand live oysters in its holding tanks. There are two long booms (about 10 metres long) that extend out from the side of the boat, each holding towropes.
With the aid of the booms, as many as six divers can operate simultaneously on the bottom of the ocean floor at depths of seven to 20 metres and cover an area 20 metres across as the boat drifts along with the tide. On board the pearl boat, the oysters are counted, cleaned and weighed, then placed in a window-sized metal frame between layers of nylon netting. The panels hold between six to nine shells. The oysters are then transported in a saltwater tank to a holding area, where the frames are attached to the sea bottom in order to recover from the stress of their capture.
The Seeding of the Oyster In a few months the panels are lifted back onto the boat where the oysters are opened and seeded by a technician. The technicians - predominantly Japanese - have honed the implantation process to a delicate art form.
The process involves inserting into the oyster a nucleus and a tiny piece of mantle cut from a nearby oyster; the nucleus is made with shell taken from a North American mussel and the mantle is the part of the fleshy oyster lip that secretes the nacre. It has been found that the shell of the North American mussel is the best material for the pearl nuclei because it is least likely to be rejected by the oyster. However, due to the great demand within the industry for them, the mussel shells are very expensive.
Once the seeding process is completed, the oysters are quickly returned to the holding area in their panels for further convalescence. Several months later the shells are transported, sometimes up to 2,000 nautical miles away, to remote farming bases.
The Pearl Farm The pearl farms are best located in sheltered areas with active tides. The north coast of Western Australia has proved to be an ideal location: there is scarcely any water pollution, few people, and extremely good tides as high as 10 metres. The big tides feed the oyster a rich mixture of organic food.
These locations are also chosen for their geographical protection from cyclones which is a climate hazard of the north west. Once here, the oyster shells are suspended from culture systems; the panels holding the shells are hung on long lines, like underwater clotheslines, supported by buoys. They are tended daily by farm workers who carry out the intensive husbandry required for the next 20 to 24 months. The oysters are cleaned to keep them free of marine growth and, occasionally, even hauled up for x-ray to assess their progress.
The Pearl Harvest The pearls are harvested during the months of June and September. Once the pearls have been taken out of the oysters, they are initially sorted, usually by shape and size. The oysters are seeded anew and the cycle begins again. A healthy oyster can be reseeded as many as four times with a new nucleus. As the oyster grows, it can accommodate progressively bigger pearl nuclei. Therefore, the biggest pearls are most likely to come from the oldest oysters. Unproductive oysters are still valuable: the nacre-covered inside is marketed as mother-of-pearl and its dried meat sold overseas in such places as Hong Kong and Shanghai, where it is considered a delicacy. The cultivation process for freshwater pearls is very similar with the following exceptions: Freshwater pearls are cultivated in mussels. Freshwater pearls are farmed in lakes and rivers, predominantly in Japan and China. During the implantation process, only mantle tissue is inserted into the mussel. In contrast to saltwater oysters, these mussels can produce 10 or more pearls at once by inserting the required number of mantle tissues. Freshwater mussels do not need to be cleaned at all once they are returned to the pearl farms. The harvesting period is shorter. Freshwater mussels are not reseeded as many times as saltwater oysters.