E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Crassostrea gigas Thunberg 1793
Japanese Oyster; Pacific Oyster
Family: Ostreidae
Photo of species

© Rick Harbo  Email the photographer   (Photo ID #12563)

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Distribution of Crassostrea gigas in British Columbia
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The Japanese or Pacific Oyster is an introduced bivalve species in British Columbia waters. Carl and Guiget (1958) documented its arrival on the Pacific Coast:

"The Japanese or "Pacific" Oyster was first introduced into the Puget Sound area in 1902, and the first shipment of seed oysters to be planted in British Columbia arrived in 1914. By 1926 a considerable industry had developed in Samish Bay near Bellingham, Washington, and success had been attained by plantings in Ladysmith Harbour, Vancouver Island. By 1932 about four million seed oysters had been imported into British Columbia and planted mostly in Ladysmith Harbour. In subsequent years, seed was also planted in Boundary Bay (Crescent Beach), Pender Harbour, Baynes Sound, Cortes Island and other areas."

"Natural spawning [in BC] was first observed in 1926 (Ladysmith Harbour), but it may have taken place earlier than this date, possibly in other areas where fishermen may have planted oysters for their own use. The first major spawnings followed by heavy spatfalls occurred in 1932 and 1936 in Ladysmith Harbour, and in subsequent years scattered individuals were found many miles from this centre. Since then breeding has been irregular. Extensive breeding in Baynes Sound and Pender Harbour in 1942 resulted in the distribution of the Pacific oyster throughout northern Georgia Strait."

Species Information

The shell of the Pacific Oyster is very variable in shape, and is often rough and sharp. The appearance is influenced by where it grows. The two halves of the shell (valves) are slightly different in size and shape, and one valve is cup-shaped. The colour of the shell in this species is variable but is usually pale white or off-white. It has large, rounded radial folds. Mature Pacific Oysters can range from 80 mm to 400 mm in size.



Pacific Oysters need a temperature of about 20° Celsius or higher in order to reproduce. Larvae are planktonic and spend several weeks in the free swimming phase, once an acceptable location has been found the oyster attaches itself to its chosen surface and spends the first year of its life as male before eventually becoming female. Unharvested oysters may live up to 30 years.


The Pacific Oyster can be found in intertidal and subtidal zones. They prefer to attach to a hard or rocky surfaces in shallow or sheltered waters but have been known to attach to muddy or sandy areas when the preferred habitat is scarce. They can also be found on the shells of other shellfish. Larvae often settle on the shells of adults, and great masses of oysters can grow together to form oyster reefs.


Global Distribution

Native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand.
Distribution in British Columbia

In British Columbia, this species is reported from Georgia Strait, including Mayne Island, Saturna Island, Ladysmith Harbour and the mouth of the Nickomekl River. It is also reported from Haida Gwaii (Queen Charlotte Islands).


The Pacific Oyster has been introduced around the world and now ranges from North America to Australia and Europe. It is an important commercial harvest in many places, including Washington State. it is considered an invasive species by many, as it out-competes native species (e.g. the Olympia oyster in Puget Sound, Washington, and the blue mussel (Mytilus edulis) in the Wadden Sea).

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References

Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-05-18 6:57:15 PM]
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© E-Fauna BC 2021: An initiative of the Spatial Data Lab, Department of Geography, UBC