Like many seafood delicacies, the clam, at first glance, is not something that begs to be eaten. It is not pretty or inviting. Buried as it is in layers of sand and/or mud it is not easily accessible. And the texture of the thing? Well, the first person to eat a clam had to be either very hungry or answering to some pre-historic round of truth or dare.
But for many, particularly those with the sea coast in their history or in their veins, the clam is not only delicious, it is rich with memories of summers at the shore, steaming mugs of chowder on a wintery New England day or the low-key hunter gatherer activity of digging for your own dinner.
Each year more than 112 million pounds of clams are harvested so, looks aside, a lot of eaters are digging their clams.
A Brief History of Clam Consumption
Clams are bivalves, a group of animals that have two shells (the valves) connected by at least one abductor muscles. Other bivalves include mussels, oysters and scallops. Bivalves are subset of mollusks, a group which also includes abalone, snails, slugs, squids and octopi.
Clams are ancient. Fossils first appear in rocks that date to the middle of the Cambrian Period, about 510 million years ago. Clams became increasingly abundant about 400 million years ago during the Devonian Period. But their population really took off during the Permian extinction, around two hundred and fifty two million years ago. In this period, ninety five percent of marine life was obliterated. Clam-like animals called brachiopods, which had previously dominated the oceans, were nearly wiped out. The bivalve clam flourished in its absences and has been with us ever since.
Clams have long been a reliable food source. Giant shell middens (piles of discarded shells), some scaling twenty-five feet high and seventy feet in base diameter, have been found from as far back as the Paleolithic period. Evidence of five thousand year old clam garden walls, a version of clam farming, suggest that Native Americans on the West Coast relied heavily on shellfish as a staple food source.
Today, there are more than fifteen thousand different species of clams worldwide. They are enjoyed in cuisines that span the globe.
Clams also offer a window into the history of our oceans. Clams have become vital resources in sclerochronology, the study of physical and chemical variations in the hard tissues of organisms. Like the rings in a tree trunk, the markings on a clam shell give scientists information about the state of the oceans' health. Since clams can live for hundreds of years, they serve as a long-term record of fluctuations in water conditions.
- Although oysters are better known for their pearl creating abilities, clams can create the lustrous beauties as well, as one Massachusetts policeman discovered.
- "Ming" is the nickname given to the oldest living mollusk ever harvested. This hard-shell clam was dredged off the coast of Iceland in 2006 and was dated at over five hundred years old. It has been studied as a record of the ocean's health over centuries.
- The Latin name for hard-shell clams, Mercenaria, is derived from the use of the shell for making wampum, or Native American money. "Clams" is also a slang term for dollars that most likely evolved from the bivalve's history of being used as currency.
- "Happy as a clam" is a shortened version of "Happy as a clam at high tide," the time of day when the clam is safely ensconced in the sand with the least risk of being harvested.
Cultivation and Harvesting Clams
Wild clams spawn when the water temperatures are favorable. Both male and female clams broadcast sperm and eggs into the water. The current does the rest. Of the millions of eggs that are excreted, only a few actually make it to adulthood. Most are never fertilized and a large percentage of young clams are eaten or are destroyed by molds or bacteria. Those that do survive will grow to adult hood well away from their spawning site.
Clam digging is a recreational seaside activity. It doesn't require a lot of equipment - a rake and a bucket; some wellies if you don't want sandy feet. However, you do need a license in some areas, so best to check with the local authorities before you gear up. You may also want to check for any area closures due to conservation or contamination such as red tide, a harmful algae bloom that can compromise the wholesomeness of your catch and your health.
Hand digging clams starts by locating holes in the sand, called the "show," that indicate a subterranean clam. One must dig or rake down to catch the burrowing bivalve. Give your catch a good rinse in sea water and you've got dinner.
Some commercial clammers boat out to heavily populated clam beds and use hand-held rakes that reach more than twenty feet into the water to scratch at the ocean floor and capture clams in an attached basked. It's a painstaking process that causes some disturbance to the environment but isn't terribly disruptive.
Hydraulic dredgers, however, are a bit more controversial. These machines pump water into the sand to loosen it and a mechanical rake follows behind, gathering clams and other sea life that get caught in the machinery. Proponents say that hydraulic dredgers are used in shallow waters that experience this type of upheaval on a regular basis during storms, for example, and easily and regularly rebound from it. Detractors believe that the force of the process is too disruptive to animal life and habitat producing grasses that are essential to a vibrant ecosystem.
Clam farmers start with "spats," baby clams that don't yet have a shell. These are spread on an area of sea floor, usually in a bay or estuary that has a strong tide but no crashing waves. The spats are then covered with netting to discourage predation. Because they are filter feeders, clams clean the water they inhabit. They rely on the miniscule organisms that the tide brings their way so, unlike farmed fin fish, they don't require any inputs - not even food and certainly not antibiotics - to thrive.
Environmental Impact of Clamming
By and large, clams are considered one of the most sustainable types of seafood to eat. The populations are healthy and, unless they are mechanically dredged, there is little bycatch in the harvest. Farmed clams don't have the detrimental environmental impact of fin fish farming, such as pollution from fish waste and feed and run off from prophylactic antibiotic use; they actually leave the water better off for living in it.
Seafood Watch recommends that you eat farmed clams ("hamaguri" in sushi). If you're buying wild clams, look for "Best Choice" sources of geoduck, Northern quahog, Northern razor and soft-shell clams that reflect best harvesting practices.
Anatomy of a Clam
In clams, two tube-like structures, called syphons, one incurrent and one excurrent, draw in and discharge seawater. The buried animals are able to extend these tubes above the sea floor to pull in food and expel waste and sperm and eggs. The deeper the clam digs, the longer the tubes.
A muscular projection (the foot) enables the clam to burrow into the sandy bottom. It also offers the clam a bit of mobility and can be used to "hop" along the sea floor.
The valves (shells) are held together by two adductor muscles that slowly contract and relax to pump water into the shell. When disturbed, the muscles snap the two-sided shell together, enclosing all organs inside for protection.
There are lots of different kinds of clams from which to choose, but no matter which variety you seek, there are a few rules that apply across the board. You never want a broken clam; shells should be in good shape. The clams should smell of the sea and nothing else, so any "fishy" odor or whiff of ammonia should send up a red flag. Clams should show some vigor. Hard shell varieties should be firmly closed or snap shut when disturbed. A touch to any visible siphons should cause the clam to retract them immediately, as if they were offended by the gesture.
Types of Clams
Hard-shell clams (Mercenaria mercenaria) come from the Atlantic Ocean along the East Coast of the US and Canada in intertidal areas. They are often called by different names to connote their size. Littlenecks are the smallest, then topnecks, cherrystones and chowders. To confuse the matter, "chowders" are also called "quahogs," though all hard-shell clams can be called quahogs, too.
Manila clams (Venerupis philippinarum) were accidentally introduced in Washington State in the 1920s. They are widely farmed in the Pacific Northwest, mostly in Washington State and British Columbia. Their sweet flavor often makes them the preferred clam for cooking.
Soft-shell clams (Mya arenaria) aren't really soft as much as they are simply brittle. They are commonly called steamers or Ipswich clams and have more of an oblong shell than hard-shell clams. Soft-shell clams live in tidal flats on the eastern shore of Canada and the US as well as across the Atlantic in the UK, where they are also known as Essex clams. Soft-shell clams are notoriously sandy. Often served steamed, eaters give them a rinse in a cup of broth served alongside to give them a final bath to remove any lingering grit before eating.
Razor clams (Siliqua patula) are popular in Oregon and Washington. They have long, thin shells and plant themselves in the sand vertically. The east coast variety (Ensis directus), is often called jackknife clam.
Geoducks (Panopea abrupta or Panopea generosa) are found on the Northwest coast of the US and Canada. They are popular in several Asian cuisines. They are rumored to have aphrodisiac properties.
Ocean quahogs (Arctica islandica) are different from quahogs of the East Coast. They nest on the ocean floor and do not burrow. They have a distinctive black shell.
Surf clams (Spisula solida) live on the eastern coast of the US and Canada from South Carolina up to Nova Scotia. They are often used in clam strips and chowder.
The giant clam of Asia (Tridacna gigas) has a shell big enough to wrap your arms around, with a frilly edge and bright colors that make it look like an iconic image from a kids' cartoon. The harvesting of wild giant clams for their meat and impressive shells has led to horrible destruction of marine habitat, such as natural reefs, which are often ground by poachers' boat propellers to release the gorgeous shells that can become encased in the reef's structure.
Clam Nutrition and Effects on the Body
A three-ounce serving (85.04 grams) of steamed clams contains 22 grams protein, four grams of carbohydrates, and less than two grams of fat. The same serving has 18 milligrams of Vitamin C, as well as Vitamins A and B12, calcium, potassium, selenium and zinc, along with 24 milligrams of iron. They are high in omega-3 fatty acids and, being low on the food chain, are free from high levels of mercury. However, clams are naturally high in sodium (three ounces contain 1,022 milligrams) and have 57 milligrams of cholesterol.
What to Do with Clams and How to Cook Them
The general rule when eating clams is that the smaller clams are eaten raw, larger clams are better cooked. But they can be served in any number of ways: grilled, steamed, in ceviche or in soups. And of course, having lived in Connecticut, my favorite way to enjoy clams is in a classic New England chowder (see below).
But first, you have to open them!
Storing Live Clams
You can keep clams the in the refrigerator, but for no more than two days, tops. Place them in a colander set over a bowl and cover with a damp paper towel and a layer of ice. You can layer seaweed under and over them for optimal freshness. You want to keep them protected but make sure they can breathe.
Soft shell and razor clams need to be purged of the sand that they not only live in, but also eat. An overnight soak in salted water will flush this out of their digestive system.
Just before using, scrub the shells with a brush and rinse thoroughly.
Clams are often canned commercially. Clams can be frozen shucked or in the shell. You can pressure can your own clams, but never use the Boiling Water Method for meat, fish, dairy or any non-acidic preparation.
Recipe: Classic New England Clam Chowder
I love a hot bowl of chowder on a blustery day, ideally at a seaside pub with a pint of local suds. I like my chowder creamy and thick with nice bites of bacon and potato in it -a real rib sticker. But this dish isn't out of place in the summer, either, particularly on a rainy summer afternoon. If you have some local corn, you can sneak that into the pot, too.
1 cup dry white wine
16 ounces bottled clam juice
2 pounds of clams, preferably large quahog (also called chowder clams) or medium cherrystones or topnecks, scrubbed
4 slices thick cut bacon, cut into 1" squares
1 onion, finely chopped
2 ribs celery, diced
Salt and pepper
1 tablespoon butter
¼ cup flour
1 pound russet potatoes, peeled and cut into 1/2" dice
1 cup heavy cream
1 cup corn kernels, optional
In a large pot with a lid, bring the wine and clam juice to a boil. Add the clams, lower the heat to a simmer, cover the pot with the lid and steam until the clams pop open, about ten minutes for medium clams, a bit longer for chowder clams. Use tongs to remove the clams from the broth, tipping the cooking liquid from each clam back into the pot as you go and setting them aside to cool. Strain the liquid through a double layer of cheese cloth and set aside. When the clams are cool enough to handle, remove the meat from the shells, dice if you prefer and set aside. (You can boil the shells and use them as serving pieces in the future.)
Return the pot to medium heat and render the bacon until crisp. Remove the bacon with a slotted spoon. Add the onion and celery to the pan, season with salt and pepper and sauté in the bacon drippings until translucent, about 3-5 minutes. Add the butter and flour and whisk to form a thick paste. Slowly drizzle in the reserved clam broth, whisking continually until it is all incorporated. Thin with water if necessary. Add the potatoes and simmer until tender, about 5-7 minutes, stirring occasionally to keep the thickened broth from scorching. Add the cream, the reserved bacon, clams and corn, if using, and simmer until thickened and flavors combine, about five minutes. Serve with oyster crackers.