Oyster Culture in North AmericaOyster Culture in North America

•SRAC 0432 The Cultivation of American Oysters

•SRAC 0433 Biology and Culture of the Hard Clam (Mercenaria mercenaria)

•SRAC 0434 Aquacultured Oyster Products: Inspection, Quality, Handling, Storage, Safety

•SRAC 4300 Extensive Culture of Crassostrea virginica in the Gulf of Mexico Region

•SRAC 4301 Hard Clam Hatchery and Nursery Production

•SRAC 4302 Oyster Hatchery Techniques

The eastern oyster, Crassostrea virginica, is native to the East coast of Canada and United States, Gulf of Mexico and Caribbean, and as far south as the Northern coast of South America.

The pacific oyster, Crassostrea gigas, was introduced from Japan and extends from Alaska to Baja California

pacific oyster

eastern oyster

DistributionDistribution

Feeding Habits – feed on anything 3-12 microns in size by filtering from the water and receive nutritional value from phytoplankton and detritus

Water temperature – 25 to 30oC for best growth

Growth to 15 cm – 9 to 12 months in the Gulf of Mexico

Salinity – 10 to 22 ppt for best growth

Oyster BiologyOyster Biology

1. Reach sexual maturity at 1 year of age.

3. Water temperatures above 25oC trigger spawning in the Gulf of Mexico.

4. Salinity above 10 ppt.

5. Spawn between March and November

Larval period is 14 to 21 days

2. Protandric - Young oysters are usually male and change to female after first spawning season.

Life HistoryLife History

Sperm triggers females to release eggs. Females can release millions of eggs!millions of eggs!

sperm

Larvae with a muscular foot looking for a site to set.

Spawning & FertilizationSpawning & Fertilization

1. Seed Production - wildSeed can be collected from the wild on shells and artificial substrates (cultch) placed near spawning grounds.

Wild-CaughtWild-Caught

2. Seed Production - hatchery

Adults are induced to spawn and the larvae are fed algae until they are ready to set.

Hatchery-RearedHatchery-Reared

Triploid oysters that can not reproduce are produced in a hatchery. Triploid oysters grow faster than normal diploid oysters and have good flavor (high glycogen content) during the summer spawning season.

gonad

Triploid OystersTriploid Oysters

Larvae ready to set can be placed in upwellers containing crushed shell or tanks with bags of shell

larvae

upwellers

tanks

crushed shell

Eyed LarvaeEyed Larvae

Spat on crushed shell are single set and spat on whole shells are multiple or cultch set.

Cultchless & Spat on ShellCultchless & Spat on Shell

Spat can be placed in protected intertidal zones to grow and harden for several months.

Exposing the oysters to the air protects them from predators.

NurseryNursery

Spat on whole shell are grown: 1. On the bottom in reefs 2. On ropes suspended off the bottom

Shells with spat are moved from spawning or nursery grounds to growout areas. Little care is given to the oysters. Culture is extensive.

Growout of Spat on Whole ShellGrowout of Spat on Whole Shell

2. Cultchless or single oysters are grown in:

trays bags

CultchlessCultchless Growout Growout

Trays and bags are suspended off the bottom by ropes tied to rafts and floats or on stationary platforms. Culture is extensive.

platform raft

floats

Oyster density and sizes, predators and fouling are controlled.

Cultchless GrowoutCultchless Growout

Oysters are graded several times to assure uniform growth and size at harvest.

Shaker table grader

Variable sizes Uniform sizes

GradingGrading

Predators are controlled by exposing the oysters to air, keeping the oyster off the bottom and manual cleaning.

starfish

black drum

oyster drill

crabs

Control of PredatorsControl of Predators

Removed by drying, pressure spraying, manual cleaning and dipping in a toxic solution.

Fouling organisms compete for space and food with oysters and restrict water flow through enclosures

fouled cleanedControl ofControl of Fouling Fouling

Reef oysters are harvested from the bottom with tongs and dredges. Oysters are ready for harvest in 1 to 5 years depending on water temperatures.Dying lifestyle in Florida!!

Harvest of Reef OystersHarvest of Reef Oysters

Oysters cultured in bags, trays and on ropes are harvested mechanically because of their weight.

Harvest of Farmed OystersHarvest of Farmed Oysters

Oysters are often contaminated by bacteria and viruses harmful to the consumer of raw oysters. Oysters can be purged by moving them to clean water in the ocean or on land.

PurgingPurging

Oysters are sold live, fresh and frozen on the half shell and shucked, canned and smoked.

Frozen on half shellFresh on half shellcanned

shucked

live MarketMarket

about 3,944,000 mt in 2000

France152,129

China2,284,663

Korea185,339

Japan222,853

United States 125,870

World Yield of OystersWorld Yield of Oysters

Wild and farmed harvest of oyster meat was 12,587 mt.

Eastern oyster meat was 9,109 mt (72%) of total harvest.Pacific oyster meat was 3,478 mt (28%) of total harvest.

Meat is 10% of the whole oyster weight!

1999 U.S. Oyster Yields1999 U.S. Oyster Yields

The EndThe End

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