The eastern oyster’s range encompasses the east coast of North America from the Gulf of St. Lawrence in Canada to Key Biscayne, Florida and south through the Caribbean to the Yucatan Peninsula of Mexico and to Venezuela. The Chesapeake Bay provides optimal environmental conditions for the species; however, oyster productivity varies within the Bay system, depending on salinity, water quality, habitat conditions, and disease.

Stimulated by increases in water temperature to 18-20 degrees Celsius, oysters generally spawn (release eggs and sperm) from May through September in the Chesapeake Bay. Fertilized eggs hatch into free-swimming larvae that settle to the bottom two to three weeks after hatching. They attach (set) to hard surfaces such as the shells of other oysters. The newly attached oysters-- called spat--begin to grow at the rate of about an inch per year. Growth rates can be affected by temperature, food quantity, salinity, and disease. Shell growth usually occurs in the spring and soft body tissue growth occurs after spawning. Oysters usually reach market size (3 inches in Maryland and Virginia) three to five year after spat settlement.

Oysters are filter feeders, consuming phytoplankton and improving water quality while filtering the water for food. As generations of oysters settle on top of each other and grow they form reefs that provide structured habitat for many fish species and crabs. Chesapeake Bay, which means "Great Shellfish Bay" in Algonquin, was once known for its abundance of oysters. Currently the number of oysters in the Bay is about one percent of what it once was. Much of this decline is due to decades of overharvest and habitat destruction. More recently two parasitic diseases, MSX and Dermo have devastated the remaining oyster populations in most areas of the Bay and its tributaries.

It has been estimated that oysters were once able to filter all the water in the Bay in three days. The sharp decrease in the number of oysters means that it now takes the current oyster population one year to filter the same amount of water. Since the oyster serves such an important function as a filter feeder it has been hypothesized that their decrease has contributed to an apparent shift in the food web in the Bay, and an increase in zooplankton and their predators (ctenophores and jellyfish).