Hundreds of varieties yet only five species | Oysters explained

How does your Oyster Grow?

Have you ever wondered how the same species of oyster can have such varied flavors or textures? How does an oyster grown on Hood Canal taste brinier than one from South Puget Sound? The word to remember for your next oyster social occasion is “merrior.”

Like different wines with a “terrior,” oysters have a merrior, illustrating the fact that growing area and method make all the difference when it comes to flavor profile for your next Pacific oyster.

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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. Muddy ground can inhibit the oysters’ ability to circulate water and food into their bodies. This had led to the adoption of culture techniques that suspend the oysters above the mud in long lines, stakes, nets or racks, and bags, while firm, sandy, or rocky bays allow for oysters to be grown right on the beach.

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. Often times, suspended oysters are placed in the high energy intertidal 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 at low tide strengthens 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 lips and force the oyster to curve. The result is a deep cup in its lower shell.

“Eat shellfish to provide a healthy diet. Shellfish are low in saturated fats, containing the essential omega-3 fatty acids; are excellent protein sources; and are good sources of iron, zinc, copper and vitamin B-12.”

wsg.washington.edu

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.

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Know your oysters

There are over 150 varieties of oysters harvested and sold in North America, yet they comprise a total of only 5 species of oysters.

1. Olympia

OSTREA LURIDA /OSTREA CONCHAPHILA

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.

2. Pacific

CRASSOSTREA GIGAS

Native to Japan, farmers began experimenting with the Pacific in 1904. Washington began importing commercial seed in the 1930’s and now it is now the most important commercial species on the West Coast. Beginning in the 1950’s researchers began to study Pacific reproduction to reduce the dependence on seed imports. Since the 1970’s local shellfish growers have relied on hatcheries for the production to meet the demand for Northwest oysters.

3. Virginica

CRASSOSTREA VIRGINICA

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

4. European Flats

OSTREA EDULIS

European Flats have smooth, round, saucer-like, flat shells with a shallow cup and seaweed-green color. They have a bold flavor with a meaty, almost crunchy texture, and intense mineral bite with a long-lasting seaweed flavor and gamey finish. There are not many farmers cultivating Flats.

5. Kumamoto

CRASSOSTREA SIKAMEA

The Kumamoto has a small deep cup and a sweet meat. Brought from Japan’s Kumamoto Prefecture, they are unable to reproduce in our cold waters so growers rely on hatchery stock. The prized cup of the Kumamoto and its limited supply has growers working with Pacifics to meet half shell demands. Growers use tumble bags to force the Pacific into a deeper cup. Oysters with names such as Kusshi, Shigoku, Sea Cow, Blue Pools, Chelsea Gems, and Baywater Sweets, are the result.


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Why is it required to shuck oysters on the beach at public tidelands?

Oysters taken on public tidelands must be shucked on the beach and the shells left behind for the following conservation-based reasons according to the Washington Dept of Fish & Wildlife website, wdfw.wa.gov:

Oyster shells provide the best growing substrate for juvenile oysters. Removing the shells from a beach reduces the overall amount of setting surface. In addition, Pacific oyster shell provides an excellent setting surface for the native Olympia oyster. This is especially true in places like southern Puget Sound where the natural setting surface - Olympia oyster shells - was eliminated years ago by overharvest.

Another concern is that removing large Pacific oyster shells removes tiny oysters which are attached to the larger shells. Thus, removing a legal limit of 18 oysters may actually remove three to five times that number of oysters - young oysters which would otherwise remain on the beach and grow to edible size.

Removing oyster shells from beaches containing Japanese oyster drills (an oyster predator) may result in the inadvertent spread of these predators. Sport harvesters are unlikely to recognize these tiny predatory snails - or their egg cases - which attach to oyster shells and can survive long periods away from water. Once shucked, these shells often end up being returned to a nearby beach by well-meaning harvesters, potentially increasing the spread of the Japanese oyster drill in Washington by depositing the “hitchhikers” on a new beach.

Many public beaches already have these tiny predators, but the goal is to minimize the spread to other uninfected beaches. The surest way to prevent oyster drills or their eggs leaving an infected beach is to require oyster shells to remain on the beach.

So head to the beach and get shucking! You will need a shellfish license, an oyster knife and gloves. Adults may shuck a child's daily limit so long as the child participates in some way in the gathering. For illustrated details on two popular shucking methods, visit wdfw.wa.gov/fishing/shellfish.