In yesterday's editions, a chart showing oyster harvests transposed the data for the Gulf states and the Chesapeake Bay. The correct version appears above.
The Sun regrets the errors.
Seafood lovers have cherished the oyster's briny taste for centuries, never imagining that the unassuming appetizer plays a key role in keeping the Chesapeake Bay healthy.
It reduces the sea nettle population, encourages the growth of underwater grass and filters pollutants and silt out of the water.
FOR THE RECORD - CORRECTION
At least that's what the oyster was able to do before it was ravaged by disease and overfishing. Today, Chesapeake oysters are barely able to keep their shells above the bay's muddy bottom.
With new evidence that oysters are crucial to the bay's recovery, a number of scientists and environmentalists are calling for more aggressive measures to protect and rebuild the remaining oyster population.
Some say oystering should be prohibited in the most productive areas.
Others, including some Virginia watermen, believe Maryland should turn to what they believe is a hardier, faster-growing Japanese oyster.
But Maryland watermen and the state Department of Natural Resources say there is no good evidence that shutting down an industry that produces 400,000 bushels of oysters a year and keeps at least 1,000 people employed would make the species more abundant.
In the 1880s, oysters grew in reefs that extended as far as five miles and that were high enough to break the surface of the water. Colonial ship captains complained they were always running aground on the reefs.
But being closer to the water's surface was a blessing for the oyster, said William Hargis, a professor at the Virginia Institute of Marine Science at the College of William and Mary. The oyster could more easily catch the tiny organisms it feeds on -- phytoplankton and bacterioplankton -- as they swirled by in the currents.
The bivalves were less susceptible to disease and, best of all, they didn't lie in their own excrement, absorbing its poisons.
Growing by the billions in these reefs, oysters filtered the entire volume of the bay's water through their gills in only four days. (By contrast, the oyster population of 1991 takes 245 days to do the same job). That filtering reduced the amount of certain types of tiny microscopic organisms in the bay -- limiting the food supply for nettlesome nettles.
The process also promoted the growth of bay grasses -- which nearly disappeared from the bay in the 1970s and 1980s. And the oyster also used up nutrients from sewage plants, farms and city streets.
"It is one of a few key organisms in the bay," said Robert Ulanowicz, a professor at the Chesapeake Bay Laboratory in Solomons. "We may cut back on nutrients and still not get back what people remember and want to see in the bay."
Harvesting these reefs, which are also known as bars or rocks, began in the 1820s, but it wasn't until the 1880s that sailing fleets of skipjacks began dragging mechanical equipment called dredges along the rocks. They broke up the reefs as tens of millions of bushels of oysters were mined from the bay every year.
From about 1930 on, the oyster harvest in Maryland hovered around 1 million or 2 million bushels a year. But since 1985, the harvest has plummeted to an all-time low in 1987 of 363,000 bushels.
Why the harvest is declining is the question now being pondered by a host of scientists. Here are two viewpoints:
"Disease is the predominant problem," said Peter Jensen, chief of fisheries at the DNR.
"It is not disease, positively, absolutely, not," said Dr. Hargis, who has been researching oysters since the 1950s and will publish a paper on overfishing this year.
Mr. Jensen's view predominated throughout the 1980s as two parasitic diseases, MSX and dermo -- which are deadly to the oyster but have no effect on humans -- swept through the bay.
But several scientists have concluded in recent months that the plunder of the oyster population is more responsible for its decline than the diseases.
"We are starting to move away from the simplistic assumptions that fishing is not an important factor," said William Goldsborough, a fisheries biologist with the Chesapeake Bay Foundation.
The foundation called for a ban on oystering this summer, an idea that infuriated watermen and was swiftly dismissed by the DNR.
Some scientists, such as Dr. Hargis, have called for an approach more moderate than an outright ban, including harvest quotas ++ and prohibitions on working some of the most productive bars. "There hasn't been any effective management for over 100 years in Maryland or Virginia," Dr. Hargis said.
"There can be no more of what we have -- allowing everyone and his brother going to any bed they want."
That is exactly what is happening near Rock Hall this fall, where hundreds of oystermen have clustered on a good bar, harvesting at a rate that is likely to leave it nearly bare within a few months.