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Oysters

Japanese oyster
Photo © 1998 Madelon Mottet
Japanese oyster grown in hanging culture in Sitka, Alaska, showing the fluting of the light shell.

Japanese oyster

The Japanese oyster Crassostrea gigas is the species that is commonly cultured on most of the Wast Coast of North America, and in many other places in the world. It is noted for fast growth and disease resistance, though it is generally considered to be inferior in taste to native species. It is highly variable in its growth characteristics and depending on the culture method may be long and narrow or oval and deeply cupped. The shell may be thick and chalky or light and fluted, and many colors are possible. I have harvested beautifully fluted specimens with light pink shells that looked more like decorations than food.

The cold waters of the north coast inhibits spawning, though specimens may still go spawny in August. In North America, most of the seed of this species comes from hatcheries. They can be received in the form of eyed larvae that can still swim, as in the picture below, or as much larger seed (up to about 20 mm).

Crassostrea gigas larvae
Photo © 1999 Madelon Mottet
Larvae of Crassostrea gigas that is still swimming with its ciliated velum but is ready to set. It about 0.3 mm (just about the size of the period at the end of this sentence).

In Washington State the market for shucking oysters is supplied by bottom culture which is a much cheaper culture method than the hanging methods that have generally been used further north. (There are no further areas that can be used for bottom culture in Washington. Metlakatla has grow-out information that shows bottom culture is also possible on their extensive beaches. The North Coast is at a competitive disadvantage in established markets because of extra shipping costs. The availability of extensive areas usable for inexpensive bottom culture may supply the competitive advantage required to establish a large oyster industry.

Japanese oyster served
Photo © 1999 Madelon Mottet
Japanese oyster grown in hanging culture in Sitka, Alaska.

Hanging oysters in the water column makes them grow faster, but these methods are expensive. Moreover,over time there may be increasing problems from fouling. An example is an invasive colonial tunicate that has been introduced into northern waters which can rapidly coat culture gear. The larvae of tunicates typically attach within minutes of being released in the water, so once gear is infected the problem can rapidly escalate.

introduced colonial tunicate
Photo © 2000 Madelon Mottet
Colonial tunicate covering oyster culture bag.




Website
© 2008 Madelon Mottet

Contact information:
RAM Marine Station
333 9th Ave. W, Prince Rupert, British Columbia V8J 2S6, Canada
Telephone/Fax 1-250-624-2097
email: madelon.mottet@gmail.com or Allen Johnson at abalone55@hotmail.com