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Nature Notes: Soft-shell Clams

Ed Robinson
January 28, 2019
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Soft-shell clams

You’ve seen them out there in the coves and bays, just like mailmen in their disregard for the sun, wind, cold and rain. They are bent over double with a short-handled, long-tined rake or hoe in hand, digging up row after row of wet, heavy mud. Their rubber hip boots are covered in slippery mud and they place their harvest in a large bucket. Of course, I am referring to the clam diggers: those hardy souls who work to the rhythm of the tides, hauling their buckets or bags of clams to shore with plastic sleds or air boats and then drive to a nearby distributor. The reward for this back breaking labor is a few bushels of soft-shell clams, and with any luck, a good payday.

The clams go by many local names, from “softshells,” to “longnecks,” even “piss clams,” but the most common handle among folks who love to eat them is simply “steamers.” No matter what you call them, this saltwater bivalve mollusk has a firm spot on many restaurant menus in New England and well beyond, and a large base of customers who can’t imagine a traditional shoreline feast without a bag of clams to start the festivities. There are many ways to prepare the clams, but steamed in a pot until the shells open, then dipped in clam juice, butter and lemon is hard to beat.

Mya arenaria is an ancient creature, with fossil records going back almost two million years. Some scientists believe the soft-shell clam was native to the Pacific Northwest and Northern Europe but was eliminated during repeat and extended ice ages that dramatically altered the climate. More recent evidence from middens found in Denmark dating to 1245 A.D. suggest that Vikings reintroduced the clams to Europe after voyages to the New World. The reintroduction could have been deliberate or more likely accidental by transport of larvae in the bilge water of their long boats. It appears that clams from the Eastern United States were introduced to San Francisco Bay in the 1870s and became dominant, crowding out some native clams and extending their range all the way to Alaska.

Today you can find these clams living from Labrador to the Carolinas and in most coastal areas of the northern Atlantic and Pacific Oceans. The population is limited in the southeastern states when water temperatures go above 82 degrees for extended periods. Their choice of habitat is sand, mud or clay soils on tidal flats, where there is a regular flow of seawater over the beds. Clams lay buried six to 12 inches in the sand. Because the calcium carbonate shell is thin and easily broken by predators, the soft-shell clam burrows much deeper than the thicker-shelled quahog clam.

To feed, the clam extends a pair of siphons up to the surface of the sand, drawing seawater in to filter out oxygen and food and then expelling it. When you walk or jump on the sand near their burrows, the clams will often shoot a stream of water in the air, revealing their hiding spot to diggers. The clams may also be found in sub-tidal areas to as deep as 600 feet.

The shell of the clam is oval and ranges in color from off-white to dark gray, depending upon its habitat. At maturity it might reach four to six inches in length. The shell does not close all the way, so the clam needs to be in water or moist sand to avoid drying out. The clam has a pair of gills for respiration and feeding, and a “foot” muscle that allows the clam to dig into the sea floor. Clams are very efficient filter feeders, removing organic materials such as plankton, algae, jellies and fish larvae from the water they take in through their siphons. The clams can filter as many as 12 gallons of water each day.

Soft-shelled clams spawn annually, generally in the early summer as waters warm to a range of 45 to 60 degrees. The fertilized eggs, up to one million for a female, hatch within 12 hours into tiny larvae that are on their own after birth and drift along with other plankton. Most of the larvae end up as food for creatures like jellies and small fish, but the surviving juvenile clams settle on hard surfaces and use an adhesive secreted by their foot to anchor in place. After a few weeks, the clam will detach from this anchor and burrow into a soft substrate to live out its life. The bedded clam is totally dependent upon the availability of clean seawater and food of sufficient quality to sustain life. Therefore the clam is at risk from periods of low water and many kinds of pollution – chemical, bacterial and fungal. The clam will need three to four years to reach the legal two inch size for harvest, and their life span is reported at a maximum of 25 years.

In our region, the soft-shell is often prey for northern moon snails, sandworms and the newly invasive green crabs. Sharks, flounder, cod, sculpin, waterfowl, otters and raccoons also dine on clams. Gulls carry clams aloft and drop them on rocks to crack the shell. In recent years, green crabs have devastated the clam population in much of Maine, with a resulting economic impact on harvesters, distributors and restaurants alike. Conservation measures are in place in many areas to limit harvests, to seed mud flats with juvenile clams, and to shield growing clams from predation where possible.

Clam harvests are tightly controlled by regulatory authorities, both to protect the species and to ensure public health and safety. Clammers may work year round, but there is less demand during the cold months of the year when tourists are mostly absent from Maine. Landings reports show that the clam harvest peaked in the late 1970s just short of 40 million pounds annually, but more recently the harvests have been 10 million pounds or less. Preliminary 2017 figures from the Division of Marine Resources show just under eight million pounds harvested, with a value of more than $12 million.

The clams should survive out of the sand for several days if refrigerated, and many chefs place them in saltwater with cornmeal or vinegar to encourage the clams to disgorge sand and other debris from their systems. It is no fun to bite down on an appetizing steamer only to grind your teeth on a bunch of sand! Clams are prepared and served using a wide array of techniques including raw on the half shell, deep fried, steamed, baked and added to stews or chowders. Discard clams with broken shells, or those that do not open while cooking. Also make sure to remove the tough, dark-colored neck skin before eating the clam. Clams on their own are good for you − low in fat and calories, with plenty of omega-3 fatty acids, iron, vitamin B-12, selenium and zinc. They are not considered at risk for high levels of mercury.

So get the pot ready, have your cornmeal at hand and prepare for a delicacy. Whether combined with other seafood like lobsters or on their own, the soft-shell clam is a great reason to live in Maine. Let us hope they prosper for millennia to come.

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