Southern quahogs range from New Jersey to the Gulf of Mexico and are especially abundant on Florida’s Gulf coast, particularly in bays and estuaries. Northern quahogs are found from the Gulf of St. Lawrence, along the East Coast, around the Florida peninsula, and into the Gulf coast of Texas; however, they are rare on the Gulf coast of Florida.
Quahogs spend most their life buried in sand or sandy mud bottoms from the mean high tide line to under 50 feet of water. They prefer moderately salty water but will tolerate a variety of salinities. In bays and estuaries, clams live near seagrass beds and algal mats, but in the Gulf, they’re also found on bare sand flats. They generally live near the mouths of bays and estuaries, where tides and currents deliver food and oxygen-rich water to them.
Quahogs grow quickly in Florida waters—up to nearly three inches in diameter in two years. As they grow, they form ridges on their shell, roughly one a year. Scientists examine a cross section of the shell to determine a clam’s age like growth rings on a tree. Southern quahogs grow up to seven inches in diameter and live at least 22 years in Florida waters; northern quahogs grow to more than four inches and live up to 30 or so years.
Quahogs can reproduce when they’re about one year old. They begin life as males, but about half change to females usually by the end of their first year. They spawn in the spring and fall. Males release sperm into the water, stimulating females to release their eggs. Females can spawn several times a year, producing millions of eggs. Sperm and eggs unite by chance. Fertilized eggs hatch and turn into free-swimming larva within about a day. As the clam begins to develop its shell, organs, and foot, it drops to the seafloor, sending out thin filaments (the developing foot) to hold it in place. As the foot develops, the clam uses it to bury into sand or mud, leaving only its siphons protruding.
Clams use one of their siphons to pump seawater with tiny plants and animals into their shell. They filter these plants and animals over the gills and pass suitable items to their mouth. They expel unwanted items through their other siphon. Predators include whelks, moon snails, and oyster drills—they can easily penetrate the clam’s shell to reach the clam inside. Crabs, pufferfish, drums, sea trout, skates, and rays also eat clams. Clams protect themselves from predators by burrowing deeper; their shell also offers some protection, especially when they’re larger.
Clams are bivalve mollusks—they have two hinged shells connected by a ligament and two adductor muscles that close the shells. The shells encase a soft-bodied clam. Clams have two siphons and a hatchet-shaped foot. Quahog shells are brownish gray to white. Both have symmetrical, oval-shaped shells, but the southern quahog’s shells tend to be thicker. The outside of the shells is ridged, except for smooth area near the hinge on the northern quahog’s shell. The inside is white and smooth with two marks where the adductor muscles attach to the shell. The inside of the northern quahog’s shell is deep purple near the outer edge and hinge.