Asian oysters missing in Severn

UM officials say boat anchor broke up experimental population's cage

September 05, 2007|By Rona Kobell | Rona Kobell,Sun reporter

About 100 sterile Asian oysters that were part of a University of Maryland experiment in the Severn River are missing after a boat anchor smashed into their cage, university officials said yesterday.

The oysters were in a huge steel cage in the Severn River, near the Naval Academy -- part of a multimillion-dollar experiment over several years to determine whether Maryland and Virginia should introduce a non-native oyster species into the Chesapeake Bay. Results of the comprehensive study are expected next year.

Between 600 and 700 oysters were in the cage when a boat pilot dropped anchor over it, inadvertently dragged it several feet and jostled the trays, said Kennedy Paynter, an associate professor at the University of Maryland Center for Environmental Science. Paynter was running the experiment with a colleague in Virginia.

Researchers immediately combed the area and recovered 557 live oysters, Paynter said. He believes very few of the missing oysters have survived -- they were likely pulverized on impact or have been covered in sediment.

The incident occurred in July but was disclosed only yesterday because Paynter and his team wanted to make sure there was no risk that the sterile oysters could become reproductive. A small percentage of the species, known as Crassostrea ariakensis, can revert to being reproductive after sterilized. Scientists estimate there is a 1-in-3,000 chance that any of the missing oysters, if still alive, could reproduce.

The experiment, which studies survival rates of the Asian and native oysters in the wild and was also being conducted in the Patuxent River, was to end next month.

Donald F. Boesch, president of the University of Maryland Center for Environmental Science, said yesterday that the researchers decided to end their work now because of the incident and because they've collected most of the needed data.

"It's raised our concerns about how we can secure these sites," he said. "This was a site that was chosen because it is a no-anchor zone, and marked as such."

It's not the first time that Paynter's cages have faced trouble in the bay. Last year, oystermen in the Patuxent inadvertently damaged the cages with patent tongs, though the cages remained intact. And the researchers decided to remove their cages from the York River last year because of high wave conditions.

Even so, Paynter said the experiment has been a success, with the scientists gathering crucial information about growth and survival rates.

"It's been a very well-organized experiment," he said. "Our problems have been with external factors."

rona.kobell@baltsun.com

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