A federal experiment in restoring oysters to the Chesapeake Bay this summer unexpectedly turned into an underwater buffet for shellfish-loving predators, with about $45,000 worth of oysters quickly eaten, scientists said yesterday.
In June, the U.S. Army Corps of Engineers dumped about 1 million oysters into Virginia's Great Wicomico River. But within weeks, about 750,000 of the oysters were consumed by a creature called the cownose ray.
The cownose ray is partial to oysters, as the U.S. Army Corps of Engineers learned in an expensive lesson as part of its bay restoration effort.
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Corps of Engineers leaders said they had no idea that the rays would cause so much damage. But that was cause for chortling in the seafood business, where oyster growers say they have dealt with the predator for years.
"The rays show up every year at the same time, in the same place. They go through the shellfish beds, and they love oysters," said Rich Pelz, president of the Circle C Oyster Ranch in Ridge, St. Mary's County.
"It's not something they should have missed," Pelz said.
The demise of the oysters, first reported yesterday by the Virginian-Pilot in Norfolk, is not the first time that nature has crossed scientists' attempts to revive wildlife in the bay.
In 1985, for instance, a moratorium was imposed to protect the declining population of rockfish. That was good news for rockfish, but it turned out to be bad news for blue crabs, one of the fish's favorite meals.
The bay's native oysters are in worse shape than rockfish or crabs: A combination of disease, pollution and heavy harvesting has driven their numbers to record low levels. The situation is so bad that many people want to write off the native oyster and bring an Asian species to the bay.
The Corps of Engineers, however, is testing to see whether the bay could be reseeded with native oysters that have been genetically engineered to prevent disease.
One of the testing grounds is in the Great Wicomico River, which flows into the bay on Virginia's Northern Neck, said Doug Martin, the program manager for oyster work in Virginia.
Before releasing oysters there, Martin said, scientists prepared for the oyster's top predator -- the blue crab -- by bringing in oysters more than 40 millimeters in size, thought to be too hefty a meal for a crab.
But he said no one had prepared them for the cownose ray, a relative of the stingray that migrates into the bay during the summer.
The ray, which can grow to a wingspan of several feet, sucks clams, oysters and other shellfish off the bottom, smashes them in its mouth and spits out the shells -- something like a baseball player eating a sunflower seed.
"The cownose ray was never identified to be a major, major problem," Martin said.