Crassostrea gigas (Thunberg, 1793)
(Giant) Japanese Oyster, Giant Pacific Oyster, Immigrant Oyster, or Miyagi Oyster
Phylum Mollusca
Class Bivalvia
Order Pterioida
Family Ostreidae
Genus Crassostrea
Species gigas
Inside of 3 shells Those same shells turned over
Two Whole Specimens, as found
Description: 25 to 30 cm long, 10 to 15 cm wide.; grayish-white to tan; shell rough and highly irregular (often with barnacles growing on shell), and fluted with obvious concentrically curved ridges.
Reproduction: Crassostrea gigas are protandric hermaphrodites
Range: Japan and Baja California to Southeast Alaska
Habitat: Marine: in bays, estuaries, and mud flats (when tide is down); on rocks, soft mud, firm sand, or gravel; in the intertidal zone.
Feeding: Filter feeders of phytoplankton, bacteria, and protozoa.
Predators: some crabs and starfish (ex: Japanese oyster drill, Dungeness crab, rock crab, and graceful crab), and humans.
Misc.: Crassostrea gigas was introduced to the North American Pacific coast as larvae in 1922 in order to create an industry of harvesting C. gigas in North America. When introduction first began, larvae was imported from Japan to North America every year, until, eventually, self-sustaining colonies established themselves in Washington and British Columbia. Now larvae are rarely imported because the established colonies produce enough offspring to adequately supply the industry.
Links:
Conservation Management Institute: http://fwie.fw.vt.edu/WWW/macsis/lists/M060003.htm
Pacific States Marine Fisheries Commission:
http://www.psmfc.org/habitat/edu_oyster_fact.html
eNature.com:
http://www.enature.com/fieldguide/showSpeciesSH.asp?curGroupID=9&shapeID=1077&curPageNum=2&recnum=SS0007
Suggested Reading: Kozloff, Eugene N., Seashore Life of the Northern Pacific Coast: An Illustrated Guide to Northern California, Oregon, Washington, and British Columbia, pp. 295-297, University of Washington Press, 1993.
Page and Photographs By: Matthew Abendroth, Invertebrate Zoology and Evolution, Spring 2004. Pictures taken at Evergreen Beach.