ANNAPOLIS — University of Maryland researchers are dropping a species of oyster originally from Asia into the Chesapeake Bay this week, the first introduction of nonnative oysters into Maryland’s portion of the estuary, the project’s supervisor said yesterday.
The 5,200 Crassostrea ariakensis, bred to be as sterile as possible, are being placed in underwater cages in sites along the Choptank, Patuxent and Severn rivers, as well as the York River in Virginia.
The experiment, more than a year in the works, is an attempt to find out how well the rugged Asian mollusks will survive compared with the few remaining native oysters, the Crassostrea virginica. State officials said they hope in less than a year to scatter reproducing nonnative oysters throughout the Bay.
At stake is an oyster fishery that this year pulled in a harvest one Department of Natural Resources official called “virtually nonexistent” — about 19,000 bushels. The previous record-low harvest, set last year, was 53,000 bushels. In the late 1800s, Chesapeake oystermen harvested more than 1 million pounds of healthy oysters every year.
The giant clusters of mollusks that once filtered Bay water and hosted their own ecosystems have been devastated by overharvesting and disease.
Alongside the lab-raised foreign oysters, researchers are dropping cages of the Bay’s native oysters, so they can compare how well the two perform.
“The reports are that ariakensis grows much more rapidly than virginica and is much less prone to disease. So we want to test that in Maryland,” said the project’s supervisor, Kennedy Paynter of the Marine Estuarine Environmental Sciences graduate program at the university.
Mr. Paynter’s oysters were bred in laboratories at the Virginia Institute of Marine Sciences (VIMS) with an odd number of chromosomes, to render them as sterile as possible. Oysters reproduce by releasing free-swimming eggs and sperm.
There is a danger the Asian oysters could regain the ability to breed as they age, Mr. Paynter said, but precautions with the brood stock minimized risks.
The experiment drew resistance from officials in Anne Arundel County, home of the Severn site, who said they fear the new oysters would become invasive, crowding out the native oysters and dominating the Bay’s ecosystem.
Oyster specialists nationwide are advising Maryland to study carefully the risks of ariakensis before introducing breeding oysters.
DNR is accelerating studies for an environmental impact statement, with the goal of introducing ariakensis into the Bay as early as this year. Gov. Robert L. Ehrlich Jr., a Republican, says the nonnative oysters are the Bay’s last, best hope for oyster restoration.
But some researchers are concerned about that timeline. At a workshop late last year, specialists from across the country concluded that about five years of research would be needed to fully assess the risks and benefits of introducing a new reproducing species. That timeline mirrors one set by the National Academy of Sciences in a report released last summer.
Not enough is known about the diseases Asian oysters could carry, how fast they spread or how they would affect the ecology of the Bay, scientists at the workshop concluded.
Meanwhile, a project similar to Mr. Paynter’s is being conducted by Standish Allen of VIMS. He released 1 million of his lab-bred ariakensis in the fall, an endeavor he calls the “million oyster march.”
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