genus: pinctada pearls in fashion (mostly) pinctada margartifera tahitian peals (black) pinctada...

Pearl Oyster

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Megann Santana

Taxonomy

• Genus: Pinctada•Pearls in fashion (mostly)

• Pinctada margartifera•Tahitian peals (black)

• Pinctada fucata•Akoya pearls (classic)

• Pinctada maxima•South Sea pearls

History of Pearl Oysters• Pearls are the only organic gems and require no

processing to reveal their natural beauty.• 1 in 2,000 pearl oysters contain a natural pearl. • Natural pearls are formed when the pearl oyster reacts to

an irritant by coating it with nacre, the shiny iridescent material found on the inner surface of the shell.

• Natural pearls are usually small, of various colors and irregular in shape.

• The high value of natural pearls led to the creation of pearl fisheries in nearly every part of the world where pearl-producing mollusks were found.

• Most of these pearl fisheries were short-lived because the fishers soon over-exploited the natural stocks.

• Prompted by the high value and scarcity of natural pearls, Japanese researchers developed methods that brought pearl production under the control of humans in the early twentieth century.

Economic Importance• Importance To Cultivators

• Sell meat, shells, and mostly pearls

• Importance to Businesses• provide oysters to consumers in various ways:1. restaurant cooks and serves oysters2. jewelry business fashions oyster pearls into jewelry3. Stores sell oyster shells to be used with arts and crafts

• Importance To Government• In terms of oyster meat, the estimate of annual worldwide oyster

cultivation is 3.2 million bushels/$20 per bushel.• The cultivation of pearls is harder to put a price, but approximately 10

tons produced.

World Record

• AN EXCEEDINGLY RARE DOUBLE-STRAND NATURAL PEARL NECKLACE. $ 3.7 million

World Record (Cultured)

• $2.3 million at Sotheby’s in 1992

Where in the world…

• Japan (make up 80% of pearl industry)• Australia• Indonesia• Myanmar• China• India• Philippines• Tahiti

Life Cycle

Reproduction in Captivity

• Find a good location• Collect sperm larvae

• Thermal stimulation induces spawning.• Larvae are free-floating in the water • Larvae must be a few weeks old.

• Larvae develop into juveniles, move to a “nursery” area or juvenile net.

• Wait a few months, transfer juveniles to a bigger net

• Wait >2 years to graft oysters• Move to a bigger net and wait another 1 ½ year

to harvest pearls

Free - Floating Larvae

Grafting• A/n nucleus/irritant (usually mother of pearl) is

inserted with a piece of donor mantle tissue into the pearl pocket.

• If it is rejected then can create deformed “Keshis”• “Rejected” meaning no nucleus because the oyster got rid

of it, but the mantle tissue remains and eventually formed a baroque shaped form with no nucleus inside of it.

• Oysters may be seeded more than once (species specific)

Production methods• Raft Culturing• Mostly used in bays

Production Methods• Long-line culture method• Cages are hung from horizontal ropes or chains connected

to floats.• Oysters are threaded at onto a small thread or rope that is

hung from a raft.• Good for open ocean environments

Production Methods• On-bottom culture• Can only be used in areas of granite or coral sand

composition of the sea bottom.

Harvesting

• Pearls are harvested after 2 – 6 years except some that are ready around 8 months

• Harvesting is done in the winter months• X-ray’s determine pearl size before

harvesting• Harvested pearls are then cleaned,

polished, and treated

Extra Aquaculture Fun Facts

• Food is supplied by filtering water• In larval and nursery stage, fed with microalgae and algae.

• Little to no labor until grafting and harvesting time

Water Chemistry• Temperature• 20 – 25C

• Salinity• Prefer higher salinities, but tolerate wide range.

• Bottom• Gravelly• Avoid sandy or muddy bottoms, reduce pearl quality.

• Depth• Optimum depth at ~ 15m

ADVANTAGES

• Almost all new pearls come from aquaculture

• Almost any size, color, luminosity, shape, etc.

• Little labor

DISADVANTAGES

• Limited production of more expensive pearls.

• Expensive to start • Time consuming (2 years

before most harvesting is ready)

• In competition with imitation pearls.

• Can be effected by weather or natural disasters.

• Possibly dangerous harvest

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