Oyster 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
Distribution
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.
pacific
oyster
The pacific oyster,
Crassostrea gigas, was
introduced from Japan and
extends from Alaska to Baja
California
eastern
oyster
Oyster Biology
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
Salinity – 10 to 22
ppt for best growth
Growth to 15 cm
– 9 to 12 months in
the Gulf of Mexico
Life History
1. Reach sexual maturity at 1 year of age.
2. Protandric - Young
oysters are usually male
and change to female after
first spawning season.
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
Spawning & Fertilization
Sperm triggers females to
release eggs. Females can
release millions of eggs!
sperm
Larvae with a
muscular foot
looking for a
site to set.
Wild-Caught
1. Seed Production - wild
Seed can be collected
from the wild on shells
and artificial substrates
(cultch) placed near
spawning grounds.
Hatchery-Reared
2. Seed Production - hatchery
Adults are induced to spawn and the
larvae are fed algae until they are ready
to set.
Triploid Oysters
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
Eyed Larvae
Larvae ready to set can be
placed in upwellers
containing crushed shell
or tanks with bags of shell
tanks
larvae
upwellers
crushed shell
Cultchless & Spat on Shell
Spat on crushed shell are single set and spat on
whole shells are multiple or cultch set.
Nursery
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.
Growout of Spat on Whole Shell
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.
Cultchless
Growout
2. Cultchless or single
oysters are grown in:
trays
bags
Cultchless 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.
Shaker table grader
Grading
Oysters are graded
several times to
assure uniform
growth and size at
harvest.
Variable sizes
Uniform sizes
Control of Predators
Predators are controlled by exposing the oysters to air,
keeping the oyster off the bottom and manual cleaning.
starfish
black
drum
crabs
oyster drill
Control of
Fouling
fouled
cleaned
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
Harvest of Reef Oysters
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 Farmed Oysters
Oysters cultured in bags, trays
and on ropes are harvested
mechanically because of their
weight.
Purging
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.
Market
live
shucked
Oysters are sold live, fresh and frozen on the half
shell and shucked, canned and smoked.
Fresh on half shell
canned
Frozen on half shell
World Yield of Oysters
about 3,944,000 mt in 2000
United States
125,870
France
152,129
China
2,284,663
Korea
185,339
Japan
222,853
1999 U.S. Oyster Yields
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!
The End
http://pars.ifas.ufl.edu/Technical%20Session/03-0129ShirleyBaker/CLAMMRS02-Web_files/frame.htm