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Bivalves 101

(article, Margarett Waterbury)

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In January, on one of the shortest, coldest days of the year, I found myself knee-deep in the Pacific Ocean in pitch-black darkness, peering into the freezing and frothy surf with the sole visual aid of an old Coleman lantern with just one working mantle. 

Under my arm I carried a cumbersome length of PVC pipe with a small handle welded onto the end. My uncle’s warning echoed through my mind: "Watch out for sneaker waves!" I was driven not by necessity or stupidity but by plain old desire: to catch my limit of razor clams. 


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That night was too dark and too cold, and the clams got the better of me; in the end, I got just half my allotted limit of 15. But seven razor clams are better than nothing, and once I got warmed up and into dry clothing, the future started to look as if it could be bright once again. 

Bivalves are some of the most recognizable and widely enjoyed culinary shellfish in the world. The word "valve" refers to any type of shell that moves in an articulated, hinged, or sliding fashion; bivalve, then, refers to animals with two valves, or shells. There are more than 10,000 species of bivalve cataloged today, representing a dizzying range of beautiful shapes, colors, and sizes.  

In the North American kitchen, we use a few different varieties of bivalves: clams, mussels, oysters, and scallops. Shellfish, including bivalves, differ greatly from one area of the sea to another, resulting in the pronounced regional variation we see between the seafood cultures of the East Coast, West Coast, and the South (or, from quahog to shining Pismo clam). 

While these four culinary bivalves have a lot in common, they each have unique methods of preparation that suit them best.

[%image reference-image float=right width=400 caption="Manila clams are a popular, easy-to-cook bivalve."]

h3. Clams and mussels

For coastal residents, the chance to flip clams out of the sand or wrench mussels from pier pilings is never very far away. The sense of joy and satisfaction that comes from collecting food straight from the outdoors is utterly addictive — and enhanced by the knowledge that, according to Seafood Health Facts, clams and their close culinary cousin, mussels, are two of the most sustainable and healthy marine resources in the United States. 

For those who don’t live near a coast, farmed clams and mussels are likewise free from the environmental concerns plaguing fish or shrimp farms. In fact, clam and mussel cultivation may actually improve the ecosystem by actively filtering water and consuming algae and plankton that reduce water oxygen levels.  

Clams and mussels belong to two different species, and look quite different from one another. Clams are short and squat in shape, and often have a soft neck that protrudes from their shells. They live buried in the sand or sea bed; many can dig and move freely (even speedily), part of the reason the sweet, scallop-like razor clam is so elusive. 

Mussel shells are dark blue or green, and shaped like an elongated teardrop. They grow firmly attached to pilings, rocks, boats, and other structures in the intertidal zone. Once attached, marine mussels cannot move, instead relying on a tight seal between their two shells to protect themselves from predators and desiccation.   

Both are normally sold live, and both should remain tightly closed until cooked; those that don’t stay closed may be dead or diseased, and shouldn’t be eaten. 

We don’t eat a lot of raw clams or mussels in the United States, instead preferring to cook them, typically in a moist-heat environment, such as a steamer basket or a pan of simmering liquid.  

Both clams and mussels benefit from being steamed in wine or beer, and are good with acidic things like tomato and lemon. As they cook, they open and release their liquor into the pan, flavoring the steaming liquid. 

Both are versatile in terms of the intensity of flavors they can support, from spicy Thai curry to a simple broth of wine, lemon, butter, and water. 

[%image mussels float=left width=400 caption="The blue shells of freshly steamed mussels open to reveal orange meat."]

Some clams, like razor clams, geoducks, and surf clams, are just too big to cook or eat whole. These all need to be cleaned before consuming; while each requires a slightly different cleaning technique, a crude but serviceable approach is to blanch them in order to open the shells, then select the parts that look the most edible. Depending on the variety, the neck, mantle, or foot of the clam can all be muscular, edible bits.

A note on safety: All bivalves are indicator species susceptible to toxins, pollutants, and minute changes in environmental conditions. As a child in Washington state's Puget Sound area, with what Bill Buford calls “a barefoot taste for the bounty of the intertidal beaches,” I spent a lot of time digging for geoducks, those leviathan clams that can grow up to seven pounds and live for well over 100 years.  

But first, always, came the call to the Washington Department of Fish and Wildlife. The number of the Puget Sound Red Tide Report hotline is still written in my grandfather’s light, block-printed pencil inside the cover of my copy of [%amazonProductLink asin=B000OBJTFW "Edible? Incredible!"], one of the most earnest and enthusiastic cooking pamphlets to ever make it to press. (Sample text: “Be willing to try everything that you can at least once . . . if you must wade or swim such as when collecting abalone, the salt water will caress, cleanse, tone and condition your body. Have you ever heard of anyone needing a tranquilizer after swimming?”) 

If you’re gathering your own, always consult with local authorities to ensure your safety and learn about any required limits and licenses. 

h3. Oysters

Sensual, elegant, and simultaneously representative of simplicity and moneyed ostentation, oysters inspire us in a way other foods can only dream of. When Seamus Heaney wrote that “my tongue was a filling estuary, my palate hung with starlight” in 1979, he wasn’t talking about the humble clam. And “the world’s mine mussel” was never uttered on the stage of The Globe.  

[%image oysters float=right width=400 caption="Freshly shucked raw oysters, served on a bed of ice."]

There’s something different about oysters. Indeed, some claim that we owe our very intellects to oysters. Large midden piles found near some of the earliest human settlements in South Africa have led scientists to theorize that easy access to the abundant fatty acids found in oysters actually supported brain development among early Homo sapiens, making large, metabolically expensive brains possible. 

More than any other shellfish, oysters, like wine, exhibit what Tobias Hogan, the co-owner of  EaT: An Oyster Bar in Portland, Oregon, calls “marroir” — a direct expression of the oceanic conditions in which they lived. 

Dissolved minerals, algae, phytoplankton, salinity, and temperature all have a significant effect on the taste and texture of oysters. Most oysters grown in the United States are one of just a few main varieties; the differences in taste are created entirely by the environment in which they grow.

On the East Coast, the majority of oysters are the mild Virginica variety, with some growers experimenting with the strongly minerally, almost crunchy European flat oysters (sometimes called the Belon) and the beloved Pacific Kumamoto (the oyster most commonly recommended to beginners due to its small size and sweet-nutty taste). Southern oysters are exclusively Virginicas, which thrive and grow huge in the warmer waters of the Gulf of Mexico, while the West Coast is home to the tiny and sweet Pacific, Kumamoto, and Native oysters. 

While oysters can be served with a wide range of sauces, toppings, and accents, Hogan recommends tasting them with nothing more than a bit of lemon or other citrus, which complements rather than hides their flavor.  

During the summer months, oysters breed, which causes them to turn somewhat soft, milky, and unappealing, although not totally inedible. (Hence the adage that oysters are at their best during the months with the letter “r” in them.) According to Hogan, it’s not the presence of a certain letter that triggers oyster reproduction, but an increase in water temperature above 60 degrees. During the summer months, oysters from colder Canadian waters become available; scientists have also developed a sterile triploid oyster that does not experience changes in quality in response to water temperatures.  

When purchasing oysters, select tightly closed individuals that have been stored in a dry environment, such as a mesh bag. Because oysters acquire so much flavor from their surroundings, storing them in water or a chemical solution after they have been harvested changes the way they taste, even causing two oysters from completely different areas to take on an identical flavor after time spent in the same liquid storage.  

When kept cold, oysters will stay good for up to three weeks in dry storage; however, oysters from the store may have already spent considerable time in transit and distribution, so it’s best to use them as soon as possible. 

Shucking oysters can be tricky. That’s why, whenever a bag of those rocky little gray gems comes across my path, I’ve put on my most charming face and offered to slice the lemons. Yes, I’ve never shucked an oyster, managing to avoid it simply because I rarely eat them alone. 

In all fairness, somebody has to open the Champagne, which, next to a mild dry Irish stout, is the ideal companion for a plate of oysters. Bolder cooks than I, however, can find detailed shucking instructions online. You can also ask your fishmonger to do the shucking for you.

h3. Scallops

Scallops are certainly the most accessible shellfish, and arguably the most delicious, too. In the U.S., we eat only the central adductor muscle of the scallop, which is responsible for opening and closing the shells. Although all bivalves have an adductor muscle, scallop adductors are much more developed, allowing them to actually swim their way, clapping and flapping, through the water like strange, exoskeletal birds. Scallop meat is the same firm texture all the way through, much like a fish fillet, which can help soothe the oogie response that some people feel about eating an entire organism like a clam or oyster.  

[%image scallops float=left width=400 caption="Raw dry-pack scallops, ready for searing."]

At the grocery store, you can usually purchase two kinds of scallop: bay scallops, which are small, about the size of a thumbnail; and sea scallops, which can vary in size from a silver dollar to nearly the size of your palm. Like shrimp, scallops are graded according to how many make up a pound. The label "50/70" indicates that between 50 and 70 scallops make up a pound, while the largest U-10 (under 10) sea scallops can weigh a couple of ounces each.  

Always, always buy scallops labeled “dry pack” or “chemical free.” Unscrupulous distributors often soak scallops in a solution designed to plump them with water and phosphates, increasing their weight and, thus, the price you pay for them. Not only are these treated scallops less tasty and a poor value, they’re also impossible to sear. The instant they hit a hot surface, extra liquid is driven out and into the pan, steaming the meat instead of creating a beautiful, caramelized surface.  


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High-quality dry-pack scallops are amazingly easy to cook, and heartbreakingly easy to overcook. I’ve found that the key elements to turning out perfectly seared scallops are a near-smoking hot pan, plenty of fat, and blind faith in my kitchen timer even when my instincts are screaming at me to turn, flip, or otherwise meddle.  

No matter which you choose, bivalves are fast to prepare, tasty enough to make any occasion feel special, and a wise choice for both personal and global health. And if you have the opportunity to muck about for them yourself at that happy point where sand, sea, and sky all meet, so much the better. 

p(bio). Margarett Waterbury is an Oregon-based writer, editor, and employee at Gathering Together Farm.

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