Oysters join blue crabs as one of the most valuable species in the Chesapeake Bay. These bivalves have an incredible ability to filter water, which increases water clarity. It has been estimated that at their historic population peak, oysters filtered all of the Bay’s water in less than one week; it takes about one year for the current population to do so.
Oysters have also constituted one of the Bay’s most valuable commercial fisheries for more than a century. But historic overharvesting, pollution and the diseases Dermo and MSX have caused a severe decline in oyster numbers.
Learn more about oysters, oyster harvest and oyster restoration.
The goal is to achieve at least a tenfold increase in native oysters in the Chesapeake Bay by 2010, based on 1994 levels, which would equal 31.6 billion grams of oyster biomass.
*Note: The historic data featured in this indicator changed from that reported in the 2007 assessmentdue to revised data from Maryland, which replaced the previously reported data.
Long-term trend
Between 1994 and 2007, goal achievement has averaged 9.55 percent, and has ranged from 12.3 percent to 5.72 percent.
- Baywide: Between 1986 and 2007, decreased from 10 percent to 8.63 percent of goal achieved (from 3.16 to 2.73 billion grams)
- Maryland: Decreased from 2.65 to 1.96 billion grams
- Virginia: Increased from 0.514 to 0.771 billion grams
Short-term trend (10-year trend)
Between 1998 and 2007:
- Bay-wide: Decreased from 12.3 percent to 8.63 percent of goal achieved (from 3.89 to 2.73 billion grams)
- Maryland: Decreased from 3.3 to 1.96 billion grams
- Virginia: Decreased from 0.587 to 0.771 billion grams
Change from previous year (2006-2007)
- Bay-wide: No significant change (8.81 percent to 8.63 percent of goal achieved; from 2.79 to 2.73 billion grams)
- Maryland: No significant change (from 1.93 to 1.96 billion grams)
- Virginia: Decreased from 0.854 to 0.771 billion grams
Oyster Abundance Indicator Data
Revised historic data from Maryland became available in conjunction with the release of the Oyster Environmental Impact Statement (EIS) in October 2008. The new data was used in conjunction with the Virginia data (that did not change) to recalculate population estimates from 1994-2006 in relation to the tenfold increase goal.
Read additional information about the Chesapeake Bay Oyster Population Estimation project and the Virginia data used in the indicator.
2008 oyster abundance data will be available in 2010.
Mike Fritz at 800-968-7229 ext. 721