In 1701, a visitor to Chesapeake Bay wrote that oysters were so numerous that the reef they made posed a hazard to navigation. By the late 1800s, the bay was yielding 15 million bushels of oysters a year, making it world’s largest oyster fishery and the most valuable fishery in the United States.
Today, Chesapeake’s oysters hover on the brink of extirpation. The authors of a University of Maryland study say that an immediate halt to fishing in Maryland’s waters is the only way to save the oysters there—and even that might not be enough for some areas.
“The magnitude of the decline raises concerns about the potential for continued loss of natural oyster beds throughout much of Maryland waters,” Michael Wilberg, the study’s lead author told Darryl Fears of The Washington Post. “We recommend a moratorium on fishing until reefs and self-sustaining populations are restored.”
Researchers said that oyster populations in the bay have plummeted by 99.7% in the three centuries since that early voyager marveled at their numbers. They have dropped by 92% since 1980 alone. In some recent years, harvests have fallen below 100,000 bushels. (There are about 350 mature oysters in a bushel.) Although disease has taken a toll, the scientists say that overfishing is putting greater pressure on populations than sickness. And efforts to build up populations in protected areas have not been sufficient to compensate for the oysters that are caught each year or die from natural causes.
Disappearing oysters is bad news for the entire Chesapeake ecosystem. An adult oyster can filter as much as 50 gallons of water per day, according to the Chesapeake Bay Foundation, removing the sediment and excess nitrogen that have polluted much of the bay. At one time, oysters filtered the entire volume of water in the bay every week. Now it takes more than a year.
In addition to cleaning the water, oysters provide habitat in the nooks and crannies between their shells for marine life such as grass shrimp, anemones, barnacles, mussels, and mud crabs. Many of these serve as food for striped bass, weakfish, black drum, croakers, blue crabs and other animals people catch for food.
Wilberg said that complete extinction of the bay oyster isn’t likely because the same species lives along much of the Atlantic coast. But if the decline continues, oysters will disappear from large sections of areas of the Chesapeake that were once prime habitat for the tasty and environmentally critical bivalves.