If you order littleneck or cherrystone clams in a restaurant, you're eating the same species. The difference between the two is simply a matter of size. Mercenaria mercenaria, the hard shell clam, also is known as the quahog. Native Americans used the shells as wampum. Quahog harvesting still means money for commercial clammers.
Clam Size Differences
At harvesting, littleneck clams range between 1 7/8 and 2 1/8 inches in length, while the much larger cherrystone spans between 2 3/8 and 3 1/8 inches in size. The smallest size is the button, those under 1 7/8 inches long. These little clams aren't legal to harvest. The topneck falls in between the littleneck and cherrystone, ranging from 2 1/8 inches to 2 3/8 inches. Chowders, the largest clams, grow more than 3 1/8 inches long and some can reach 5 inches or more.
Quahogs sport heavy shells ranging from pale gray to light brown. Growth rings cover most of the outer shell. The inner shell has a dark purple lining around the back and on the hinge. These bivalves have a muscular foot, with which they burrow into the sand. They survive on plankton, filtering these microscopic plants into their bodies through a siphon-like organ.
Where They Live
Hard-shelled clams are found along the eastern seaboard of the United States, ranging from the Gulf of Mexico to the Gulf of St. Lawrence. They dwell in mud and sands along bays and beaches. Since clams prefer less salinity than that found in ocean waters, they often are found in estuaries, where salt water meets fresh water. While quahogs are able to burrow, their motion is quite limited. Once burrowed, they generally stay put unless disturbed. If you're digging for clams -- make sure you have any necessary permits -- you'll find them in the low tide line, within the top 3 inches of sand or mud.
Cherrystone clams aren't just larger than littlenecks -- they're also older. You can figure out a clam's age by counting the shell's growth rings. Clams reaching chowder size might be 40 years old or more. Younger clams grow more quickly than older ones. Clams start reproducing about the age of 1, spawning in summer. They don't stop laying eggs until they die or are harvested. While you can probably count the rings on a littleneck's shell, it's harder to determine a cherrystone's age since by that stage the rings grow fairly close together and are less distinct. Figure that your plate of littlenecks were probably 4 years old at harvesting and the cherrystones about 8 years old.
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