During the Triassic Period, approximately 190 million years ago, Crassostrea virginica, the eastern oyster, first appeared and has remained relatively unchanged since that time. In the past, this mollusk was found throughout much of the Chesapeake Bay in water depths up to 100 feet. Now, they are rarely found below 30 feet and their numbers have been greatly reduced. The adaptive nature of the oyster in a changing estuarine environment allowed it to survive and flourish, but environmental pressures are taking a toll and many scientists are concerned about the decline in the number of oysters in the Bay.
Efforts are currently underway to replenish oysters at various sites in the Bay.