About Pearl Culture
The pearl culturing business in Ehime is divided into two parts. Culturing Akoya mother oysters and producing pearls by using the mother oysters.
We make a mass purchase of Akoya oysters that traders grew for about 2 years around this time of year.
Now the pearl culturing begins using these Akoya oysters.
After we purchase Akoya oysters, we pack them in the baskets.
We pack many Akoya oysters into the baskets called “pre-conditioning box”. It is almost sealed and it doesn’t let water go through. Then the baskets are submerged into the ocean.
The crammed Akoya oysters in the baskets gradually go into a state of apparent death as there is not so much water going through. Traders of pearl-culturing express this process as “let them live but don’t kill them”, this is why.
Now, a nucleus is inserted in Akoya oysters.
A nucleus is a source of pearl.
A round-shaped piece scraped from a shell called swan mussel is used as a nucleus.
Inserting a nucleus requires a high degree of skill. It usually takes several years to be able to do it.
First, a pre-operation called “cutting tissue” has to be done. Akoya oysters used here are called “donor oyster”. Outer mantle fold is separated from donor oyster. Outer mantle fold is a part that secrets the component of shells. When you look at inside shells, it is shiny. The “color” and “luster” there will be reflected on pearls. A nucleus is inserted in Akoya oyster along with the mantle fold, then the outer mantle fold forms nacre. That becomes a pearl.
Usually, one nucleus is inserted in one oyster, but sometimes two nuclei are inserted. Our specialists deal with about 600 to 700 implantations a day.
After the implantation, Akoya oysters go into post-surgery “rehabilitation”.
They are neatly lined in the basket and placed under the rafts stretching into the ocean. They spend about a month in the inshore calm bay until their wound is healed, until they recuperate fully.
After the recuperation for about a month, they get back into society, and finally “leave the hospital”.
They are transferred to the farm outside the bay. It’s called “offshore transfer”.
Some oysters discharge a nucleus thinking it was a foreign substance.
The oysters are examined individually by fluoroscopy in order to check if the inserted nucleus is still there.
They are transferred into a net and moved to the farm blessed with abundant nutrition.
Akoya oysters stay there until the harvest after being transferred offshore. Barnacles, sea moss and some other things can be adhered to Akoya oysters or a net so that cleaning has to be done every 10 to 14 days using a machine until the harvest. If they are too persistent, it has to be done by hand.
Akoya oysters are pulled up from the ocean and pearls are taken out of the shell. The harvest is carried out during the winter when the water temperature is low.
The nacre gets firm when water is cold, and that creates a strong luster.
After getting out of the ocean, Akoya oysters are taken out of the net and divided into “alive” and “dead”. Living oysters are opened, and the content is divided into adductor muscle and the rest of the meat. There is a pearl in the rest of the meat except adductor muscle. A large mixer can separate pearls from the meat. The harvested pearls are sorted according to the type of mother oysters.
The process above takes about a year.
The pearls produced after these processes are called “Tonen-mono (harvested within a year)”.
The pearls harvested in the following year after nurtured in the ocean for another year are called “Koshi-mono (harvested over the year).”
“Koshi-mono” stays in the ocean a year longer so that the nacre layer becomes thicker and we tend to get higher quality pearls.
However, the mortality rate of Akoya oysters becomes higher and not all the pearls have higher quality, so in other words, it’s taking a big risk. Doi Pearl makes an effort to increase the quantity of “Koshi-mono” as much as possible in order to produce higher quality pearls.
Miuranishi, Uwajima-shi, Ehime,
Open from 9:00 a.m to 17:00 p.m