While the Bay's salinity is ideal for oysters and the oyster fishery was at one time the Bay's most commercially viable, the population has in the last fifty years been devastated.
 Maryland once had roughly 200,000 acres (810 km²) of oyster reefs.
 Today it has about 36,000.
 It has been estimated that in pre-colonial times, oysters could filter the entirety of the Bay in about 3.3 days; by 1988 this time had increased to 325 days.
 The harvest's gross value decreased 88% from 1982 to 2007.
One report suggested the Bay had fewer oysters in 2008 than 25 years earlier.

The primary problem is overharvesting.
 Lax government regulations allow anyone with a license to remove oysters from state-owned beds, and although limits are set, they are not strongly enforced.
 The overharvesting of oysters has made it difficult for them to reproduce, which requires close proximity to one another.
 A second cause for the oyster depletion is that the drastic increase in human population caused a sharp increase in pollution flowing into the Bay.
The Bay's oyster industry has also suffered from two diseases: MSX and Dermo.

The depletion of oysters has had a particularly harmful effect on the quality of the Bay.
Oysters serve as natural water filters, and their decline has further reduced the water quality of the Bay.
 Water that was once clear for meters is now so turbid that a wader may lose sight of his feet while his knees are still dry.

Efforts of federal, state and local governments, working in partnership through the Chesapeake Bay Program, and the Chesapeake Bay Foundation and other nonprofit environmental groups, to restore or at least maintain the current water quality have had mixed results.
One particular obstacle to cleaning up the Bay is that much of the polluting substances arise far upstream in tributaries lying within states far removed from the Bay.
Despite the state of Maryland spending over $100 million to restore the Bay, conditions have continued to grow worse.
Twenty years ago, the Bay supported over 6,000 oystermen.
There are now fewer than 500.

Efforts to repopulate the Bay via hatcheries have been carried out by a group called the Oyster Recovery Partnership, with some success.
They recently placed 6 million oysters on eight acres (32,000 m²) of the Trent Hall sanctuary.
Scientists from the Virginia Institute of Marine Science at the College of William & Mary claim that experimental reefs created in 2004 now house 180 million native oysters, Crassostrea virginica, which is far fewer than the billions that once existed.
While the Bay's salinity is ideal for oysters and the oyster fishery was at one time the Bay's most commercially viable, the population has in the last fifty years been devastated.  Maryland once had roughly 200,000 acres (810 km²) of oyster reefs.  Today it has about 36,000.  It has been estimated that in pre-colonial times, oysters could filter the entirety of the Bay in about 3.3 days; by 1988 this time had increased to 325 days.  The harvest's gross value decreased 88% from 1982 to 2007. One report suggested the Bay had fewer oysters in 2008 than 25 years earlier.
The primary problem is overharvesting.  Lax government regulations allow anyone with a license to remove oysters from state-owned beds, and although limits are set, they are not strongly enforced.  The overharvesting of oysters has made it difficult for them to reproduce, which requires close proximity to one another.  A second cause for the oyster depletion is that the drastic increase in human population caused a sharp increase in pollution flowing into the Bay. The Bay's oyster industry has also suffered from two diseases: MSX and Dermo.
The depletion of oysters has had a particularly harmful effect on the quality of the Bay. Oysters serve as natural water filters, and their decline has further reduced the water quality of the Bay.  Water that was once clear for meters is now so turbid that a wader may lose sight of his feet while his knees are still dry.
Efforts of federal, state and local governments, working in partnership through the Chesapeake Bay Program, and the Chesapeake Bay Foundation and other nonprofit environmental groups, to restore or at least maintain the current water quality have had mixed results. One particular obstacle to cleaning up the Bay is that much of the polluting substances arise far upstream in tributaries lying within states far removed from the Bay. Despite the state of Maryland spending over $100 million to restore the Bay, conditions have continued to grow worse. Twenty years ago, the Bay supported over 6,000 oystermen. There are now fewer than 500.
Efforts to repopulate the Bay via hatcheries have been carried out by a group called the Oyster Recovery Partnership, with some success. They recently placed 6 million oysters on eight acres (32,000 m²) of the Trent Hall sanctuary. Scientists from the Virginia Institute of Marine Science at the College of William & Mary claim that experimental reefs created in 2004 now house 180 million native oysters, Crassostrea virginica, which is far fewer than the billions that once existed.
Chesapeake Bay