Populations of Maryland oysters have dropped to 0.3 percent of their estimated high, prompting conservation efforts.
It's long been known that there are far fewer oysters in the bay than there used to be, but research from the University of Maryland suggests the drop is even more severe than earlier estimates.
The native oyster has fallen to an estimated 0.3 percent of historic levels in the upper Chesapeake Bay since the early 1800s. The decline is due primarily to over-harvesting, loss of habitat and disease.
The University of Maryland's Center for Environmental Sciences used data from long-term surveys to create a population model to come up with the number. It matches up with accounts of early explorers who wrote of oyster reefs so high they stuck out of the water at low tide and were a hazard for ships.
Michael Wilberg, who developed the models, says the collapse of the eastern oyster is among the largest documented declines of any marine species.
There is positive news for the oyster, however. The state of Maryland has created more oyster sanctuaries and is promoting aquaculture. Groups such as the Chesapeake Bay Foundation are trying to create artificial reefs. And some research shows oysters are evolving limited disease resistance.