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30-Jul-2009

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Native oysters, back in the Chesapeake




After many years of effort, a team of researchers has finally been able to restore native oysters to their home in the Chesapeake Bay, Virginia. This new "metapopulation" of oysters is made up of many different populations, separated by distance and the researchers say that it is the largest metapopulation of native oysters in the world. This study proves that recovery efforts in the Chesapeake can be successful, and it also provides hope for other conservation efforts around the world.

Over-fishing and habitat destruction have destroyed native oyster populations worldwide, and in the Chesapeake Bay, populations of the oysters had dropped to only one percent of what they used to be.

To address this problem, in 2004, David Schulte and colleagues from the Virginia Institute of Marine Science built different types of native oyster reefs called "high-relief" and "low-relief" reefs on about 86.5 acres of river bed in nine different protected areas of the Great Wicomico River in Virginia. Their high-relief reefs lie 25 to 45 centimeters above the river bottom, while the low-relief reefs rest eight to 12 centimeters above the river bottom.

In 2007, Schulte and his team found about 185 million oysters, young and old, had found homes on their reefs. This number is close to the total number of oysters in all of Maryland's waters, which is estimated to be 200 million.

The researchers found that the height of the reefs above the river bottom were the key to saving the oysters. Their high-relief reefs flourished, but the low-relief reefs struggled.

Generally, these low-relief reefs have been used by fishery management agencies, but these new findings suggest that high-relief reefs are much more successful at restoring native oyster populations there, in the Chesapeake Bay. Schulte and his colleagues recommend abandoning the low-relief reefs and using only high-relief reefs in the future.

Now, in 2009, the researchers say that their oysters are still healthy and thriving.

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This research appears in the 30 July 2009 Science Express.