How to Distinguish from Similar Species: This is the largest local oyster; and usually the most commonly encountered one. The other introduced oyster (Crassostrea virginica) and the native Olympic oyster (Ostrea lurida) do not have the conspicuous frills on the valves and grow to no larger than 15 cm in height.
Geographical Range: Widely introduced on the west coast (and worldwide) from Japan. Prince William Sound, AK to Newport Bay, CA. Scattered in many bays where oyster culture has taken place. Very common in Willapa Bay on the SW Washington coast, and in Departure Bay and the Georgia Strait in British Columbia.
Depth Range: Intertidal to 6m
Habitat: Firm sediment or rocky beaches
Biology/Natural History: The shape of this oyster is quite variable. The species was introduced from Japan in the early 1900's (to Washington and British Columbia in 1922) and is the most important aquacultured species on the US West Coast. The japanese littleneck clam Tapes japonica and the Japanese oyster drill Ceratostoma inornatum, as well as the intestinal parasitic copepod Mytilicola orientalis were apparently introduced to our coast along with this species. May live 20 years or more. Often contains irregular, non-lustrous pearls. Predators include predatory oyster drill snails, the crabs Cancer magister, Cancer productus, Cancer oregonensis, Hemigrapsus nudus, and H. oregonensis, some sea stars, and the black oystercatcher (bird). The blue mud shrimp Upogebia pugettensis is a problem on commercial beds of this oyster because it digs sediment from its burrows and smothers the oysters with sediment. The oyster typically attaches to hard substrates, such as rocks or the shells of other oysters. The oysters are imported as very small individuals (spat) and raised in commercial oyster beds. They are said to poorly reproduce in California, so are found only in the oyster beds. I have seen many oysters in apparently natural conditions here in Washington, so they must be able to reproduce at least a bit better here. Sexes are separate in this species, but an individual may change sexes (especially in the winter) and may alternate being male and female. Natural populations in Japan tend to favor protandry, and the largest individuals are likely to be females, especially if they are alone instead of in an aggregation (Yasuoka and Yusa, 2016). A few are simultaneous hermaphrodites (both male and female at the same time). Spawning occurs from May to October (Suquet et al., 2016). They outgrow native oysters, probably partly because they are more efficient filter feeders, and can feed on nannoplankton, which native oysters cannot do. Occasionally they are influenced by a red tide (usually by the dinoflagellate Gonyaulax catanella) and become toxic to eat. Warm temperatures of 25 C or greater and salinities well over 39 ppt increase their production of heat shock proteins. 37 C is sublethal and 44 C is lethal (Yang et al., 2016).
Larvae of this species are very sensitive to increases
carbon dioxide in the water (Barton
et al., 2012). Lower seawater pH triggers smaller size and
in survival in the larvae, but increased temperature of the seawater
mitigates this effect. However, this mitigation is
increased production of enzymes used to detoxify reactive oxygen
suggesting that the larvae are still under increased metabolic stress
at lowered pH and increased temperature (Harney
et al., 2016).
Flora and Fairbanks, 1966
Kozloff 1987, 1996
Smith and Carlton, 1975
Charifi, Mohcine, Mohamedou Sow, Pierre Ciret, Soumaya Benomar, and Jean-Charles Massabau, 2017. The sense of hearing in the Pacific oyster, Magallana gigas. PLOS one 12(10): e0185353. https://doi.ort/10.1371/journal.pone.0185353
Harney, Ewan, Sebastien Artigaud, Pierrick Le Souchu, Philippe Miner, Charlotte Corporeau, Hafida Essid, Vianney Pichereau, and Flavia L.D. Nunes, 2016. Non-additive effects of ocean acidification in combination with warming on the larval proteome of the Pacific oyster, Crassostrea gigas. Journal of Proteomics 135: pp 151-161
Ruesink, Jennifer L., B.E. Feist, C.J. Harvey, J.S. Hong, A.C. Trimble, and L.M. Wisehart, 2006. Changes in productivity associated with four introduced species: ecosystem transformation of a 'pristine' estuary. Marine Ecology Progress Series 311: pp 203-215. doi 10.3354/meps311203
Salvi, D. and P. Mariottini, 2016. Molecular taxonomy in 2D: a novel ITS2 rRNA sequence-structure approach guides the description of the oysters' subfamily Sacconstreinae and the genus Magallana (Bivalvia: Ostreidae). Zoological Journal of the Linnean Society 179:2 pp 263-276. https://doi.org/10.1111/zoj.12455
Suquet, Mark; Florent Malo, Isabelle Queau, Dominique Ratiskol, Claudie Quere, Jacqueline Le Grand, and Christian Fauvel, 2016. Seasonal variation of sperm quality in Pacific Oyster (Crassostrea gigas). Aquaculture 464: pp 638-641
Yang, C.-Y.; M.T. Sierp, C.A. Abbott, Li Yan, and J.G. Qin, 2016. Responses to thermal and salinity stress in wild and farmed Pacific Oysters Crassostrea gigas. Comparative Biochemistry and Physiology A-Molecular & Integrative Physiology 201: pp 22-29
Yasuoka, Noriko and Yoichi Yusa, 2016. Effects of size and gregariousness on individual sex in a natural population of the Pacific oyster Crassostrea gigas. Journal of Molluscan Studies 82: pp 485-491
General Notes and Observations: Locations, abundances, unusual behaviors:
Authors and Editors of Page:
Dave Cowles (2005): Created original page