CLAMS AS FOOD
A) egg cockle; B) calico clam; C) zigzag scallop Clams are bivalve mollusks with two shells held together by a hinge. They have a soft body and siphon, which they use to filter-feed from the water. Clams can be divided into two types: hard-shell and soft-shell. Hard-shell clams are smaller and have thicker shells that are harder to open. Soft-shell clams are usually larger and have a thin, brittle outer shell.[Source: American Oceans]
For thousands of years clams have been a staple, sustainable food source for people living in coastal areas as evidenced by shell middens, collections of discarded shells, that can be many meters thick. Clams are a great source of protein and omega-3 fatty acids. In many places, people still enjoy digging for clams in the spring.
Clams can be eaten raw, steamed, boiled, baked, fried, or made into soups and clam chowder. Many edible clams such as palourde clams are ovoid or triangular, Razor clams have an elongated parallel-sided shell, like an old-fashioned straight razor.
Top Food Clams, Globally
Seafood Ranking — Common name(s) — Scientific name — Wild or Farmed — Harvest in tonnes (1000 kilograms)
5) Asari, Japanese littleneck, Manila clam, Filipino Venus, Japanese cockle, Japanese carpet shell — Venerupis philippinarum — Farmed — 3,785,311 tonnes This species is often the main ingredient in the so-called crab sticks.
29) Chinese razor clam, Agemaki clam — Sinonovacula constricta — Farmed — 720,466 tonnes
53) Blood cockle — Anadara granosa — Farmed — 391,574 tonnes
[Source: Food and Agriculture Organization of the United Nations (FAO), 2012; Wikipedia]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
U.S. farmed hard clams are a smart seafood choice because they are sustainably grown and harvested under U.S. state and federal regulations. Growing clams requires no feed — they filter phytoplankton directly from the water column. Shellfish toxins and bacteria occur naturally in the environment and can cause foodborne illnesses. State and federal regulations require monitoring of farmed clams to ensure they are safe to eat. [Source: NOAA]
Clams are grown in tidal areas. They can be grown directly on the beach bottom or in mesh bags, trays, or pens that are secured to the bottom. Some hatchery raised clams have dark, zigzag stripes across the shell known as “notata”. In the U.S., permitting for shellfish aquaculture is governed by federal, state and local governments. The federal agencies involved are NOAA, the Army Corps of Engineers, Fish and Wildlife Service, U.S. Department of Agriculture, the Environmental Protection Agency, the Food and Drug Administration, the Bureau of Ocean Energy Management, and the Coast Guard. Shellfish farms must adhere to federal regulations including those in the Magnuson-Stevens Fishery Conservation & Management Act, the Endangered Species Act, the National Environmental Policy Act, and the Clean Water Act.
About 70 percent of all the domestic clams consumed in Japan come from waters off Kashima in Ibaraki and Chiba Prefectures. The clams there are collected by three associations divided into five groups, with only one group allowed to gather clams at one time with a period of at least one week between the time the next group can depart. It is said clams are tastiest in the winter and spring when they put in fat before starting to lay eggs in June.
Types of Clams Eaten in the U.S.
Soft Shell Clams are also known as sand gaper or Essex clams. According to American Oceans: Commonly found in tidal flats, estuaries, and muddy areas, they are considered an invasive species in many areas, so eating them is an excellent way of controlling their population. A pot full of soft shell clams, with some wine and olive oil thrown in, is a delicious meal or snack. [Source: American Oceans]
Steamers or steamer clams are also known as long-neck clams and are a variety of soft-shell clams. They are oval and have distinctive long dark necks. These clams are delicate and tender, with a sweet and salty flavor. You can find them in the Atlantic Ocean and the east coast of Canada. As the name suggests, the best way to serve steamers is to steam or fry them.
Atlantic Jackknife Clam can be found in estuaries and shallow areas of the Atlantic Ocean. It is easily identified by its long, thin, pointed shell. The shells are often yellowish-brown and have distinctive black marks on them. It grows up to 15 centimeters (six inches) in length. One of the best ways to cook Atlantic jackknife clams is Vietnamese style. This recipe calls for you to grill them with fish sauce, olive oil, and lime juice.
Pacific Razor Clams are found in the Pacific Ocean from Alaska to California. They have long, thin shells and can grow up to 23 centimeters (9 inches) in length. They are sometimes confused with the Atlantic jackknife clam, but Pacific razors have a sharper edge, and you can identify them by their unique purple and yellow hues. You can serve pacific razor clams in many ways, but the best is by deep frying them.
Manila clams (Lajonkairia lajonkairii) are an edible species of saltwater clam in the family Veneridae, the Venus clams. Also known as Japanese littleneck clams, Japanese cockles, Japanese carpet shell and Bajirak (the Korean name for them), they are commercially harvested, and are the second most important bivalve grown in aquaculture worldwide. [Source: Wikipedia]
The Manila clam is native to the coasts of the Indian, Philippines and Pacific Oceans from Pakistan and India north to China, Japan, Korea and the Kuril Islands as well in the northeast Pacific Ocean. The shell is elongated, oval, and sculptured with radiating ribs. It is generally four ro 5.7 centimeters (two to 2.3 inches) wide, with a maximum width of 7.9 centimeters (3.1 inches). The shell varies in color and patterning, but generally is cream-colored to gray with concentric lines or patches. The inside surface of the shell is often white with purple edges. The siphons are separated at the tips.
Manila clams are among the world’s most common and widely eaten clams. Many farmers cultivate them. According to American Oceans: They are easy to tell from other clams due to their uniquely colored hard shells. The shells are often shades of blue, brown, and purple with unique geometric shapes. The best way to cook Manila Clams is to steam them. Although you can also bake, poach, or saute them. [Source: American Oceans]
Cockles are small hard-shell clams found in saltwater and brackish water. Although many small edible bivalves are loosely called cockles, true cockles are species in the family Cardiidae. True cockles live in sandy, sheltered beaches throughout the world. They have distinctive rounded shells that look heart-shaped when viewed from the end. Numerous scallop-like radial, ribs cover the shell.
Cockles are usually no bigger than five centimeters (two inches) wide and come in various colors, including brown and yellow. They are some of the most common clams in the world and can be found in most seafood restaurants. It is easy to prepare cockles. Serving them with brown butter and garlic sauce is said to bring out the flavor [Source: American Oceans]
Cockles are popular in Japan, Korea and China, They and whelks, both kinds of cold-water mollusk, are popular snacks at English seaside resorts. Billy Bryson of National Geographic described them as a "tasteless," "the limit for what could be classified as an edible substance" and said eating them was akin to "a wedge of chewing gum about the size of size of a Ping-Pong ball that you have been chewing for ten hours."
Quahogs are hard-shell clams in the Atlantic Ocean. They have thick shells and usually range in size from 5 to 12.5 centimeters (two to five inches). They have solid white meat that is firm and has a mild, sweet flavor. They are associated with New England and often used in clam chowder. They can also be eaten raw or steamed and served with garlic and butter. [Source: American Oceans]
Northern quahogs (Scientific name: Mercenaria mercenaria) also known as hard clams, quahogs, round clams and chowder clams. They have a gray shell and brown, black, and white line details. Native to the Atlantic Ocean and introduced to the Pacific Ocean, they live in intertidal zones at depths of up to 10 meters. Their native distribution is along the east coast of North America, from the Gulf of St. Lawrence into the Gulf of Mexico. Among the places they have been been introduced to are the coasts of California, England, Humboldt Bay, and Southern Brittany. Attempts have been to introduce the clam to the Etang de Thau on the south coast of France and around Sicily, but no populations have successfully taken hold in the Mediterranean Sea. There have been other attempts to introduce the clams but most don't result in a self-sustaining population. [Source: Bradford Burdette, Animal Diversity Web (ADW) /=]
Northern quahogs are found in the greats numbers in mud flats, mud and sand flats, and sand flats. However, soft muddy bottoms cannot support the weight of the heavy-shelled clams, causing sediments to be stirred up. Silt may block the siphon of the clam from filtering out the water. Tides play an important role being in new supplies of food and oxygen and to carrying away waste. Water that is too turbulent in the surf zone, may wash the clams away. The ideal salinity range for Northern quahogs larvae is 20 to 35 parts per thousand, Adults can put up with higher amounts of salt.
Types of Quahogs
Northern quahogs are sub classified by length. Chowders are the biggest measuring up to 7.5 centimeters (three inches) in width, Cherrystones are five to 7.5 centimeters (two to three inches), Top Necks are five centimeters (two inches( in width, and Little Necks are the smallest measuring one or two centimeters (1/3 to 2/3 of an inch).
Chowder Clams is a colloquial term used to describe various clams used to make chowder. Common chowder clams include cherrystone, quahog, and littleneck clams. According to American Oceans: These clams are all found on the eastern coast of the United States and are anywhere from 5 to 10 centimeters (2-4 inches) in size. The best way to serve chowder clams is in clam chowder. Start by sautéing onions, celery, and bacon in a soup pot. Add potatoes and the clams, along with chicken broth and milk. Simmer the chowder until the potatoes are tender, stirring occasionally. [Source: American Oceans]
Littleneck Clams look like Quahogs but are significantly smaller. You can find them in the Atlantic or Pacific oceans. Littleneck clams are usually about 2.5 to five centimeters (one to two inches) in size and have a slightly sweet flavor. Littleneck clams are great for a quick and easy meal. You can steam them in a delicious garlic-butter sauce or combine them with linguine and tomato sauce. Littleneck clams are also a great addition to salads and soups.
Cherrystone Clams are round and about five to 7.5 centimeters (two to three inches) in size. Their shells are off-white, and some of the smallest clams on this list. It can take up to 10 of them to make one pound of clams. They can be found mainly in the Atlantic Ocean. They range from the shores of Prince Edward Island in Canada to the Yucatan Peninsula in Mexico. Cherrystone clams have a sweet, delicate flavor and firm texture. The mild flavor of Cherrystone clams makes them a great addition to many types of dishes.
Ocean quahogs (Scientific name: Arctica islandica) make up a clam species with dark brown, hard, oval shells. Also known as clam, quahog, black clam and mahogany quahog, they are widely eaten and are found in the western Atlantic Ocean from Newfoundland to Cape Hatteras, North Carolina. While a small portion of those caught are sold as bait, most are processed for human consumption in soups, chowders, and stews. Most quahogs in U.S. waters have a shell width of 7 to 11 centimeters (2.8 to 4.3 inches). They are among the longest-lived marine organisms in the world — in some cases living for at least 200 years. They grow very slowly and do not start to reproduce until around age 6, and do not reach a commercially harvestable size until about age 20. [Source: NOAA]
Ocean quahogs are bivalve mollusks. They have two hinged shells that enclose their body. Their shells are thick and oval-shaped. Outside are a dull gray with growth rings that can be used to determine its age. The live in water between 8 and 396 meters (25 and 1,300 feet) deep. In the northern part of their range, they’re found in shallower water closer to shore. In U.S. waters they are generally found in waters 3 to 200 nautical miles from shore. They are rarely found where bottom water temperatures exceed 15.5̊C (60̊ F).
Ocean quahogs burrow in a variety of sediments, especially fine sand.. Ocean quahogs are filter feeders that primarily consume microscopic algae.. They bury themselves in the ocean floor and pump oxygen-filled water and food particles in through their siphons, which extend above the surface of the ocean floor. Many animals prey on juvenile ocean quahogs, including invertebrates such as rock crabs, sea stars, and other crustaceans, and fish such as longhorn sculpin, ocean pout, haddock, and cod. Once ocean quahogs have reached a certain size, they have a very low predation rate. They burrow in the sandy ocean floor and their thick shells close completely, providing substantial protection from potential predators..
Ocean quahogs spawn by releasing eggs and sperm into the water column where the eggs are fertilized. They spawn once a year, either in the summer or fall. The spawning season is sometimes extended over a number of months as quahogs release eggs and sperm a little at a time. Eggs and larvae are found in the water column and drift with the currents for at least 30 days until they develop into juveniles and settle to the bottom.
Ocean Quahog Fishing
In 2021, the ocean quahog fishery produced 6.8 million kilograms (15 million pounds) of clam meats, valued at $53.6 million, according to the NOAA Fisheries commercial fishing landings database. Commercial fishermen harvest ocean quahogs with hydraulic clam dredges, which use jets of water to dislodge ocean quahogs from the sandy ocean floor. A smaller “dry” dredge (without hydraulic jets) is used in Maine waters. [Source: NOAA]
Ocean quahogs burrow into sandy bottoms on the continental shelf, an environment that is thought to recover quickly after a hydraulic clam dredge passes over it. The bars on commercial clam dredges are spaced several inches apart so they do not collect anything but the targeted quahogs.
The quahog fishery is managed under an individual transferable quota program that slows the pace of the fishery and increases its efficiency, significantly reducing bycatch. The fishing rate is at recommended level. Fishing gear used to harvest quahogs has minimal impacts on habitat. Fishing gear used to harvest quahogs is designed to minimize bycatch.
Population Status: According to the 2020 stock assessment the ocean quahog stock is not overfished and is not subject to overfishing. Ocean quahogs are relatively unproductive and can only support low levels of fishing. Population levels are declining despite relatively low fishing rates, but remain above target levels. [Source: NOAA]
The U.S. fishery focuses on two regions: Maine and Long Island, New York. Dredge and hand harvest are authorized in the commercial fishery, with hydraulic clam dredges being the primary gear type used. The recreational fishery is limited to hand harvest. under the Surfclam-Ocean Quahog Fishery Management Plan: 1) Fishermen must have a permit for commercial harvest ocean quahogs. 2) Under individual transferable quota (catch shares) program — managers set an annual catch limit for federal waters and allocate it among individual fishermen or vessel owners. These individual quotas can be sold or leased. 3) Sometimes areas are closed due to environmental degradation or to toxins that cause paralytic shellfish poisoning (PSP). 4) Fishermen harvesting ocean quahogs from Georges Bank have additional requirements under the PSP testing protocol. 5) There is a mandatory vessel monitoring systems. Fishermen must maintain and submit logbooks of each fishing trip to document catch. The ocean quahog fishery off Maine is managed separately because of differences in biological, fishery, and market characteristics.
Geoducks (Scientific name: Panopea generosa) are giant burrowing clams and among the largest clams in the world. Native to the North American Pacific coast from Alaska to Baja California and particularly associated with the U.S. Pacific Northwest, they have long, thin shells that are usually yellowish-brown in color and large siphon (“neck”) that sticks out the clam and looks sort of like a large human penis, which is one reason why it is prized as an aphrodisiac in China,
Also known as king clams, elephant clams, gweducks, goeducks, and goiducks, geoducks (pronounced “gooey-ducks”) are harvested in the wild and produced in a growing geoduck aquaculture industry, particularly in Washington State. The majority of Washington's geoduck farming takes place in southern Puget Sound. [Source: NOAA]
Geoducks (pronounced “gooey-ducks”) weigh up to three kilograms (seven pounds). Their shell is typically 15 to 20 centimeters (6 to 8 inches) long. Geoducks are characterized by a small shell and very long siphon, or "neck." The siphon can be up to one meter (three feet) The long “neck” has two openings at the end — one for taking in oxygen and phytoplankton and one for releasing excess water.
Geoducks are long-lived; the oldest ever recorded was 168 years old. Theu burrow into the sediment about 30 centimeters (one foot) per year to a depth of one meter (3 feet). In the first 3-5 years, geoducks grow to 0.7 kilograms (1.5 pounds), and generally reach maximum size (about 3 kilograms, 7 pounds) at 15 years. Females release between 1 and 2 million eggs per spawn..
Geoduck is sometimes served as sashimi. American Indian tribes in the U.S. Pacific Northwest have made fortunes selling geoduck to markets in Hong Kong and southern China. The clams can weigh as much as 16 pounds and have a penis-like neck that can extend for three feet. Wealthy diners will pay up several hundred dollars in Hong Kong or Shanghai for a dish made with geoduck meat. Hoa Phuong Do Cooperative in Vietnam which is run by people living with HIV operates a farm raising Geoduck clams on Cat Ba island. The farm earned several thousand dollars a year in the late 2000s.
Surfclams, also known as surf clams, sea clams, hen clams or bar clams, are giant clams found in the Atlantic Ocean. You can easily recognize them by their large rounded shells and light purple or pink inner lining. Surfclams can weigh up to 1.5 kilograms (three pounds) and measure up to 20 centimeters (eight inches) in length. You can find them hiding in the sand on many beaches. Surf clams are eaten raw, steamed, fried, or baked. [Source: American Oceans]
Atlantic surfclams (Spisula solidissima) have a triangular shell with yellowish tan, rounded edges. In the U.S. they can be found in the western North Atlantic from the southern Gulf of St. Lawrence to Cape Hatteras, North Carolina. They’re most abundant on Georges Bank, the south shore of Long Island, New Jersey, and the Delmarva Peninsula. Their shells are thick, triangular, and yellowish-white with rounded edges and concentric ridges. Shells do not close fully and gape slightly. They grow up to 22.6 (8.9 inches), although clams larger than 7.9 inches are rare. [Source: NOAA]
Surfclams are the largest bivalves found in the western North Atlantic. They can live up to 35 years. Surfclams grow fast, reaching a harvestable size of about 12.5 centimeters (5 inches) in 5 to 7 years. Growth rates depend on water temperature — southern surfclam populations in warmer water grow more slowly than the more northern populations. On average, surfclams living in open water live longer than those living inshore.
Surfclams are planktivorous filter feeders, straining tiny plants out of the water to eat. Larval surfclams eat algal cells. Adults primarily feed on diatoms, green algae, and naked flagellates. Snails, crabs, shrimp, and fish, including haddock and cod, feed on surfclams.. Juveniles burrow in medium- to fine-grain sand in waters 30 to 80 feet deep.Adults prefer medium- to coarse-grain sand and gravel from beach zones to over 160 feet deep. Surfclams prefer more turbulent waters and bury themselves just below the sediment surface.. Surfclams spawn from late spring through early fall. They shed their eggs and sperm directly into the water column. Some are able to reproduce by age 1, but most spawn by the end of their second year. Larvae spend about 3 weeks in the water column as plankton before settling to the bottom to live.
Surfclams are the most important commercial clam species harvested in the United States. In 2021, the commercial landings in the U.S. of surfclam totaled 12.5 million (27.6 million pounds) and were valued at $24 million, according to the NOAA Fisheries commercial fishing landings database. Fishers generally concentrates on the populations off the coasts of New Jersey and the Delmarva Peninsula. Surfclams are generally processed for human consumption in soups, chowders, and stews; while a small portion of landings are also sold in the bait market.[Source: NOAA]
Commercial fishermen harvest surfclams with hydraulic clam dredges — essentially large, heavy sleds pulled along the sea floor. High-pressure jets blast water into the sediment, which temporarily liquefies it and allows a steel blade to pass through the first few inches of substrate and scoop the clams onto the dredge, where they are captured in a cage made of steel bars. Atlantic surfclams burrow into sandy bottoms on the continental shelf, an environment that is thought to recover quickly after a hydraulic clam dredge passes over it. The bars on commercial clam dredges are spaced several inches apart so they do not collect anything but the targeted surfclams.
The surfclam fishery is managed under an individual transferable quota program that provides fishermen with more flexibility on when to fish, slows the pace of the fishery, and increases its efficiency, significantly reducing bycatch. Dredge and hand harvest are authorized in the commercial fishery, with hydraulic clam dredges being the primary gear type used. The recreational fishery is limited to hand harvest.
There are above target population levels. The fishing rate is at recommended level. Fishing gear used to harvest surfclams has negative impacts to habitat, but the fishery is managed to minimize these impacts, particularly to sensitive habitat. Fishing gear used to harvest surfclams is designed to minimize bycatch.
Population Status: According to the 2020 stock assessment the surfclam stock is not overfished and is not subject to overfishing.NOAA Fisheries, the Mid-Atlantic Fishery Management Council, and state resource management agencies manage the surfclam fishery .under the Surfclam-Ocean Quahog Fishery Management Plan, which says: 1) Fishermen must have a permit to harvest surfclams. 2) Under individual transferable quota (catch shares) program — managers set an annual catch limit for federal waters and allocate it among individual fishermen or vessel owners. These quotas can be sold or leased. 3) There are minimum size limits, which can be suspended by managers if they can demonstrate the harvest of small surfclams is below a certain threshold, and closed areas due to environmental degradation or to toxins that cause paralytic shellfish poisoning (PSP). 4) Fishermen harvesting surfclams from Georges Bank have additional requirements under the PSP testing protocol that including mandatory vessel monitoring systems. Fishermen must maintain and submit logbooks of each fishing trip to document catch.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated April 2023