Introduction:
The European oyster goes by the Latin name Ostrea edulis. It has a great
reputation and is served in fine restaurants all over the world. Although
native to northern Europe and the Moroccan coast of North Africa since
Roman times, the European oyster was only introduced to Nova Scotia in
1973. The shell is similar to the American oyster, but flakier in texture
and more evenly rounded with a wavy edge. The European oyster is pinkish
white in color, sometimes with purplish pink margins.
Reproduction:
European oysters are usually ready to spawn when they
are two years old. Spawning is seasonally controlled and
gonad (reproductive gland) development occurs in late spring.
A unique feature of this species is its ability to develop
both male and female gonads in the same spawning season.
If food remains available and temperature is adequate an
oyster may develop eggs after having spawned as a male,
or vice versa. When spawning occurs, females retain the
eggs within their shells. Males release sperm into the water
which is drawn in by the female and fertilization occurs.
Life Cycle:
After fertilization the eggs remain in the female's shell
for one or two weeks living off food stored in the egg.
When they are about 0.18 mm in size the female releases
the larvae and they begin feeding. They continue to feed
and develop until they are approximately 0.32 mm in size
and ready to set on a suitable surface. The larvae are now
called spat and undergo metamorphosis. During metamorphosis
they lose some of their larval organs and develop adult
organs such as gills. After this change, the juvenile oysters
resemble adults and grow according to food availability
and temperature.
Feeding Habits:
European oysters are filter feeders. As water passes over
their gills, particles in the water (such as phytoplankton)
are trapped on the gill surfaces. This is transferred to
the labial palps where it is sorted for digestion.
Growing Techniques:
European oyster culture begins in a hatchery. Fertilization
takes place in tanks and plastic discs are provided for
the larval oysters to set on. About 12 hours after setting
on the discs, the oysters are scraped off. These juvenile
oysters are now about 0.35 mm in size and they are moved
to upweller tanks where they feed on algae. They usually
remain here for two or three weeks until they reach 5-15
mm. In June the oysters are placed in seed trays in the
ocean. They spend 1-2 months growing in these wooden trays
until they are 2-5 cm in size. For final grow-out they are
placed in lantern nets or mesh bags. It usually takes between
36 and 48 months for oysters to grow from hatchery to market
size.
Farming Areas:
In Nova Scotia, European oysters are farmed in the area
from Halifax to Yarmouth. This is an area known for its
good currents and warm water temperatures, conditions that
make it suitable for growing this species. Select areas
on the eastern shore may also be suitable for European oyster
farming, where environmental conditions are optimum.
Conclusion:
For more information, contact Aquaculture
(aquaculture@gov.ns.ca).
Nova Scotia Fisheries and Aquaculture
P.O. Box 2223
Halifax, Nova Scotia
Canada B3J 3C4
Phone: (902) 424-0356
Fax: (902) 424-4671
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