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Importance

Oysters are a valuable species because they improve water quality, provide habitat for aquatic life and contribute to the region’s economy.

Oysters filter water as they feed, which increases water clarity. It is 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. Pollution, historic overharvesting, and the diseases MSX and Dermo have caused the oyster population to decline severely.

Goal

The goal is to achieve an oyster biomass of 31.6 billion grams. This would represent a tenfold increase in native oysters based on 1994 levels.

Trends

*Note: The historic data featured in this indicator changed from that reported in the 2008 assessment. Revised data from Virginia replaced the previously reported provisional data.

Long-term trend

There is no statistically discernable trend away from the 1994 baseline. Oyster abundance remains at a very low level.

Between 1994 and 2008, goal achievement has averaged 9.61 percent and has ranged from 12.3 percent to 5.72 percent.

• Bay-wide: Between 1994 and 2008, oyster biomass increased from 3.16 to 3.24 billion grams (from 10 percent to 10.25 percent of goal achieved)
• Maryland: Between 1994 and 2008, oyster biomass decreased from 2.65 to 2.09 billion grams
• Virginia: Between 1994 and 2008, oyster biomass increased from 0.514 to 1.15 billion grams

Short-term trend (10-year trend)

There is no statistically discernable trend. Oyster abundance remains at a very low level.

Between 1999 and 2008:

• Bay-wide: Oyster biomass decreased from 3.89 to 3.24 billion grams (from 12.3 percent to 10.25 percent of goal achieved)
• Maryland: Oyster biomass decreased from 3.29 to 2.09 billion grams
• Virginia: Oyster biomass increased from 0.596 to 1.15 billion grams

Change from previous year (2007-2008)

• Bay-wide: Oyster biomass increased from 2.73 to 3.24 billion grams (from 8.62 percent to 10.25 percent of goal achieved)
• Maryland: Oyster biomass increased from 1.96 to 2.09 billion grams
• Virginia: Oyster biomass increased from 0.769 to 1.15 billion grams

Additional Information

The information reported in this indicator:

• Gauges success toward restoring the ecological contribution oysters make to the Bay’s water quality and aquatic life.
• Indicates the abundance of the oyster population, which the commercial oyster industry and the region’s economy depend on.
• Measures results of the priority and budgetary commitments that have been placed on oyster restoration.

Learn more about the Chesapeake Bay Oyster Population Estimation project, which provides the data used in this indicator.

The 2008 data are the most current data available. 2009 oyster abundance data will be available in 2011.

Contact

Bruce Vogt
National Oceanic and Atmospheric Administration (NOAA)
(410) 267-5655

Source of Data

Virginia Institute of Marine Science