Stimulated by increases in water temperature to 64-68°F (18-20°C), 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 years after spat settlement.
