2. Facts about Pearls
- First Cultured Pearl was in Japan by
- Natural, cultured, freshwater and saltwater
are the most common pearls types.
- Japan is the largest producers of Pearls
- First pearl culture research was developed
- The best quality of pearl is known as
Lingha pearl obtained from marine
oysters. The duration of formation of pearl
is about 7 years. The pearl oyster belongs
to genus Pinctada, family pteriidae, and
class bivalvia and phylum Mollusca
6. 1. Selection of farm site
01 Quality pearls are produced in deeper waters (beyond 10 m)
02Muddy bottom should be avoided. Sea bottom should preferably be gravelly or
an admixture of sand.
03Water current should be mild (about 1 knot)
04The suitable range of temperature is between 18-25°C. During winter when
temperature drops to about 10°C, the oysters undergo hibernation.
The normal calcium level in sea water is 400 mg/1. In Tuticorin Bay, salinity
ranges from 316 to 454 mg/1.
The pH of the sea water should be between 7-8. Salinity in the Gulf of Mannar
generally varies between 30 and 35 ppt.
07 Pink coloured pearls contain more sodium and zinc, while copper and silver
are responsible for gold- and cream-coloured pearls.
The hatchery establishment comprises facilities for good sea water supply, aeration, maturation
and spawning of oysters, live algal production for food, larval and spat rearing
7. 2. Construction of Pearl Farm
The whole pearl farm system is
based on series of floating
Ten units of wooden rafts are
Each raft consists of two to five
pieces of wood making the
total length to 20 ft.
The raft is covered with wire
mesh baskets, each of which
house 10 oysters.
8. 3. Well planned
A typical work schedule plays a
very critical role in pearl culture.
The timing for collecting and
seeding the oysters must be
scheduled and followed strictly.
9. Collecting oysters
Oysters are generally located on a flat rock bottom and are
usually covered with marine animals and a thin layer of silt.
Therefore, it is often very difficult for divers to recognise them.
The shells collected, are cleaned, sized, and placed into baskets
for storage until they are transferred to the pearl farm.
Cleaning & Transfer
They are fed once a day with adequate supplies of
microalgal food. The sea water is changed every alternate
day after removing the larvae on a sieve. To prevent
bacterial and fungal diseases, antibiotics are added to the
larval rearing medium.
Spat must grow upto 20 g in weight
to be considered suitable for Nucleus
When the spat reaches 3 mm, they are carefully collected from the tanks, placed in
fine-meshed velon screen nets with a protective covering and transplanted to the
When the oyster reaches 25 mm, they are taken out and grown in regular baskets
Preparation of the Graft Step 3
Two-three year old healthy oysters are
considered for surgical implantation known as
seeding. This is a very delicate operation and
involves three stages:
Attatching the Graft
Inserting the core
A donor oyster or mussel is sacrificed to obtain
mantle. Mantle is needed by the host oyster to
accept the nucleus.
The mantle is located on the outer section of
the oyster and Mantle produces the nacre
which forms pearl. Before a graft is taken from
the mantle, the oysters are starved for several
days to slow down the metabolism of the
oyster. This helps to decrease the risk of core
rejection and open the oyster easily.
Preparation of the Graft
Best sites forPearl formation are gonandal
regions and spent individual (gonads withno
Nucleus isinserted ingonadal region
13. Spherical shell
beads are used
as nuclei to
prepared out of
thick shells of
14. What you need
This is where most
From a donor oyster
An external spherical
shell bead to be
implanted as an
Called “Mother of the
Time ranges from 2-7
Mantle Gonad regions
Gets to work
What Oyster has
The oyster is opened with special wedges
and pliers, then a scalpel slit is made in the
soft tissue near the reproductive organ and a
graft of living mantle is inserted into the slit.
Attaching of the Graft
Timeand number of nuclei to beimplanted
will bedetermined inadvance
A nucleus is placed in the scalpel slit and the oyster is
then returned back to the water. The inserted core
irritates the oyster, provoking it to gradually coat the
core with thin layers of mother of pearl nacre. After
some time, the oysters are collected, and x-rayed to
see whether the implants have been accepted. Oysters
which have rejected the implant are returned to the
water and are once again operated. The oysters which
have accepted the implant are transferred to the pearl
Attaching of the Core
Convalesence- A time period of rest and
allowed to recover from the disturbance
Oysters are kept in cages
The Epithelial cells of the peal sac will
deposit a nacreous layer around the nucleus
which leads to the formation of a pearl
Attaching of the Core
19. Methods in Pearl culture
After 2-3 years, the oysters are
harvested. It is necessary to make a
trial harvest to determine whether
the pearls have a sufficient coating. If
it is not sufficient then an additional
six months to a year of culturing is
necessary. The oysters are split open
and pearl bags are cut by the scalpel
to remove the pearls. Collected pearls
should be thoroughly dried after the
harvest to prevent loss of luster.
Pearls are obtained by Pulverising the
20. Methods in Pearl culture
There are many different steps involved with the
sorting of pearls. Firstly, the pearls are sorted
according to whether they can be used for the
cultured pearl industry or not.
These are categorised into three sections:
• Unmarked pearls
• Pearls with one major blemish
• Pearls with more than one major blemish
27. (1) To control the mortality of oysters in the post-
(2) reduce the rate of rejection of nuclei,
(3) improve production of quality pearls,
(4) to increase the size of the nuclei up to 16 mm
(5) production of round nucleated pearls having size up
to 17 mm diameter, in freshwater mussels.
Future Challenges to be encountered