The following explanations are to explain the differences between the farming methods used for Freshwater, Akoya, South Sea and Tahitian Pearl Production. However, our focus is on South Sea Pearl and Tahitian Pearl Production.
Freshwater Pearl Production
Freshwater pearls are farmed as the name suggests in ponds, lakes and rivers, with China being the major producer. The majority of Freshwater mussels are not bead nucleated.
The technician creates a small incision into the mantle of a 6 to 12 month old mussel, and inserts a small piece of mantle tissue from a donor mussel. Usually there are 12 to 16
insertions per side of the oyster, (it has two halves) producing from 24 to 32 pearls per mussel. The pearls that are non-nucleated are solid nacre. Some of the larger sizes of freshwater pearls, which have reached even 12mm could be nucleated.
Freshwater pearls have a wide range in colours, and some of the crop is dyed as with
'black coloured' freshwater pearls.
Akoya Pearl Production
The akoya oyster is the smallest pearl producing oyster, producing pearls ran
ranging from 2mm to 10mm. Akoya pearls are cultured or nucleated pearls farmed in saltwater, from the Pinctada fucata (martensii). The word 'Akoya' is the Japanese name for this Pearl Oyster. The Japanese pioneered the cultivating techniques, which also form the basis of the skills learned in South Sea Pearls and Tahitian Pearl production as described below.
Tahitian Pearl Farming
Pearls from the species Pinctada Margaratifera and are naturally found and farmed in
Tahiti and French Polynesia, and this same species is also found in the Cook Islands,
and several other areas around the world. The pearls are unique because of their natural dark colours,which range from silvers to greens, brown pistachio, aubergine, green, 'peacock', to a very rare 'jetblack'.
These oysters can grow to nearly 30cm diameter. After 3 years they usually range between 15 to 18cm diameter, and can weigh up to 3 or even 4 kg.
Tahitian pearl oyster farming is different in that the spat or larvae grow in the lagoons of Tahiti, where the spat is collected at 'exit' points of lagoons, where the tidal flow exits to the ocean. The spat bonds to objects, even motor car tyres, which serve as the collectors. When the oysters are mature enough to produce pearls, from two years to two and a half years old, they are then grafted and beaded - a small piece of mantle tissue of a donor oyster is grafted on to a nucleus made from a freshwater mussel inserted 'surgically' into the gonad of the oyster. After the grafting process the oysters are then suspended on long lines in the clear water of the lagoon for minimum one and a half years to produce the pearls. These can be grafted 2 or three times. But, unfortunately the pearl quality can reduce as the oyster produces the larger pearls.
South Sea Pearl Production
These oysters, from the Pinctada Maxima, are the largest of oysters, growing up to 30cm in
diameter, and over 3kg, and are larger than the Pinctada Margaritifera. The largest Tahitian Pearl is usually up to 18mm, while the largest South Seas Pearl can be 20 to 23mm, with some South Sea Baroques being even larger. The nacres of South Sea Pearls can be from 2mm thick to more than 6mm thick.
Pinctada Maxima Oysters are initially collected from the wild, in the bays and in the ocean,
however the major producers have hatcheries, where they produce oysters from spat, which are the baby oysters or lavae, rather than from collecting shell from the wild.
The oysters have nucleii, made from the shell of freshwater mussels, inserted into the
gonad of the oyster; and a graft from mantle tissue (epithelium) from the donor oyster is inserted into the gonad of that oyster, and this initiates the growth of nacre around the nucleus. The grafted tissue encases the foreign body by forming a Pearl Sac. Without this pearl sac a pearl will not form. The gonad of a South Sea oyster is much larger than that of the Tahitian Oyster, as being the major reason allowing the Pinctada Maxima to produce the larger pearls.
The oysters are held in nets for usually up to two years, where they are cleaned regularly,
for any marine organisms and parasites. Pearl Farming is an incredibly labour intensive and expensive process. The pearls are harvested annually, but the different species have different harvesting criteria, according to their species, the seasons, and water temperatures. Some Pearl Farms will seed their oyster for one, two or up three times. But the usual is once or twice.