Oyster species and what makes them so different

The not so secret secret to good oysters – is safehandling. From the moment you purchase, insure that they are kept cold and fresh – on ice or covered with a damp cloth in the fridge to keep them moist. Fresh oysters must be alive just before consumption or cooking. Tap on the shell– a live oyster will close up and is safe to eat.

Below is a handy guide to the local oyster species -- it may surprise you many of the favorite varieties that you crave are just trade names of the Pacific! It is the water they live in that makes all the difference!

Olympia

Olympia Oyster

The native oyster to Washington State, the Olympia oyster is a half dollar size with a metallic finish. The Olympia oyster fishery ran from the mid-1800s until about 1915 supplying California’s demand for oysters. The oysters were harvested from shallow bays of southern Puget Sound and Willapa Bay until pollution and over harvesting caused a collapse of the wild fishery.

Pacific

Pacific Oyster

Native to Japan, farmers began experimenting with the Pacific oyster in 1904. Washington began importing seed in commercial quantities in the 1930s. This practice of importing seed lasted for over 45 years. The Pacific is now the most important commercial species on the West Coast.

Beginning in the 1950s researchers began to study Pacific reproduction to reduce the dependence on seed imports. Since the 1970s local shellfish growers have relied on hatcheries for the production to meet the demand for NW oysters.

Kumamoto

The Kumamoto has a small deep cup and a sweet meat that is prized by raw oyster consumers. Brought to WA from Japan’s Kumamoto Prefecture, they are unable to reproduce in Northwest waters so growers rely exclusively on hatchery stock. The prized cup of the Kumamoto oyster and its

limited supply has growers altering growing practices to create cupped Pacific oysters to meet half shell market demands. Growers use flip or tumble bags to chip the shell of the Pacific and force it into a deeper cup. Specialty oysters with names such as Kusshi, Shigoku, Sea Cow, Blue Pools, Chelsea Gems, and Baywater Sweets, are the result.

Kumamoto Oyster

Virginica

The decline of the Olympia oyster opened the door for the import of the Virginica from the east coast in the early 1900s. The eastern oysters did not adapt well to NW waters and experienced large die off when transplanted. There are still beds of Virginicas raised by WA shellfish farmers.

How does your oyster grow?

Have you ever wondered how the same species of oyster, Pacific for example, can have such varied flavors or textures? Like different wines with a terrior, oysters have a merrior – growing area and method make all the difference!

Not all beaches are created equal – some are muddy, some sandy and some rocky. Each type of growing ground has opportunities and limitations for success. Oysters grown on top of muddy ground often sink into the mud suffocating them for they aren’t able to circulate water and food into their bodies. Muddy bays have led to culture techniques that suspend the oysters above the mud such as long lines, stakes, suspended nets, and racks and bags. Firm sandy and rocky bays allow for oysters to be grown on the bottom as well as using the off bottom techniques described for muddy areas.

In addition to substrate type, location of the oysters on the beach will determine how long the oyster will take to achieve a marketable size. Oysters grown in the intertidal area are exposed to daily tidal inundation will have well developed adductor muscles and thicker shells thus being heartier for shipment. Oysters suspended in the water column for growing will have the benefit of a constant food source and thus grow quickly but will have delicate shells and be susceptible to the elements. (continued next page)

Often times suspended oysters are placed in the high energy inter-tidal environment for a few weeks prior to market to harden the shells for shipment and condition the oysters to hold their shells shut.

The method of growth can greatly change the shape of the oyster. A Pacific allowed to grow naturally on the beach will have a sturdy irregular shell with a great deal of frills. The regular exposure to low tide exposure, strengthening the shell, protects the meat from heat and predators like sea stars and crabs. In Europe, where there is very limited tidal change, some farmers manually pull the oysters from the water for periods of time to mimic the tidal action.

The tumble bag creates an altered but very marketable shape for cultured oysters. Oysters are placed in the bag as small seed and the tide does the rest. The tidal flip and roll chip off the fragile off the fragile shell lips and force the oyster to curve. The result is a deep cup in its lower shell.

Each bay has its own selection of phytoplankton yielding oysters with different meat colors and flavors.

Pacific oysters grown in Willapa Bay have a different “merrior” from those grown in Samish Bay. Hood Canal oysters are claimed to be more briny than the sweeter cucumber flavored bivalves grown in Hammersley Inlet or South Puget Sound waterways. Just like the well attuned vintners of the Rhone Valley, oyster connoisseurs are able to detect the subtleties of each bay by tasting the meat and observing the shell.