Hard Clam

Mercenaria mercenaria

The hard clam is a bivalve mollusk with thick, ridged shells that vary in color from brownish to grayish or white.

• Hard clam shells are egg- or heart-shaped.
• The interior of the clam's shells is usually white with dark purple patches.
• The shells, or valves, are joined at the hinge by a thick brown external ligament.
• A hatchet-shaped foot and two short siphons periodically extend from the clam's soft interior.

Hard clams can grow to about 4 inches.

Where does the hard clam live?

Hard clams use their foot to bury themselves in sand or muddy sand along the shoreline to depths of about 60 feet.

• The bulk of the Bay's hard clams are located in Virginia waters.
• In the Maryland portion of the Bay, hard clam populations are restricted to Tangier and Pocomoke sounds.

What does the hard clam eat?

Hard clams are filter-feeders on planktonic algae.

• While buried in the sand, the clam's two siphons stick up above the surface.
• The clam draws water down through its inhalant siphon.
• Food particles in the water are filtered out by the clam's gill cilia.
• Unused particles are periodically ejected through the exhalent siphon.

How does the hard clam reproduce?

Hard clams spawn better May and October, once the clams produce ripe gametes and water temperature rise above 68 to 73 degrees.

• Females can release 16 to 24 million eggs per spawn. Eggs are fertilized in the water column.
• Free-swimming larvae develop over a period of a week to 24 days. During this time they develop a foot, which is used to crawl and “explore” a surface before settling.
• When they find a suitable surface to settle on, the clam larvae anchor themselves by thin threads secreted from a gland on the foot.
• The settled clam slowly metamorphoses into a juvenile hard clam, developing siphons, digestive viscera and gills.

Other facts about the hard clam:

• The hard clam is a long-lived species; individuals have been aged at more than 30 years.
• Native Americans used to use hard clam shells as wampum.
• Hard clams are also called "quahogs," "littlenecks," "cherrystones" or "chowder clams." The various commercial names are based on the size of the clam.