Pacific Oyster        Crassostrea gigas



Looking like a white rock among the cobbles, this Pacific oyster is unusual in that it is not in a clump of other oysters on a muddy sand beach.    Originally from Japan, this large mollusk was imported in the early 1900's first to Samish Bay near Bellingham area than subsequently to Willapa Bay and south Puget Sound.  It is distinguished from our native Olympia oyster by it's white color, large size and flutes or ruffles on the shell. The Pacific oyster, also referred to as the Japanese oyster, is faster growing than the Olympia oyster reaching harvest size in four to six years while the Pacific oyster takes only two. The Pacific oyster can grow to 10 inches, but the Olympia oyster only grows to 3.5 inches.  Both oysters are filter feeders straining plankton from the water.  The larger Pacific oyster can pump up to 60 gallons of water a day.


Oysters differ from clams that dig in the sediment for protection or scallops that can swim away from predators by depending on a thick shell to ward off an attack by a crab or gull.  However small individuals are still vulnerable and crabs can be a problem.  In addition Ghost shrimp can affect oyster beds due to their burrowing activity which softens the sediment.  Oyster growers use various management tools to reduce the impact of predators or competitors on oyster beds.  Because oysters grow best in the low intertidal and shallow subtidal areas, growers usually spread seed or harvest using specially designed barges at high tide.  However some growers hang oysters from beach structures and must tend them at low tide.


Seed oysters are obtained today from both oyster hatcheries and natural reproduction.  However because the Pacific oyster requires warm water to mature and spawn, it does not do so on a regular basis in Washington.  As a result for many years seed oysters were imported from Japan (except during the second world war).  


The culture of oysters is the most valuable aquaculture activity in Washington at around $58,000,000 per year in 2000 as estimated by the Pacific Coast Shellfish Growers Association. The culture of oysters and clams has been very important to Washington for a long time as witnessed by the fact that the first Washington State legislative session after statehood passed several major laws that dealt with sale and use of tidelands for aquaculture.