Chesapeake oysters doing better

State survey finds reproduction up, diseases and deaths down

February 07, 2011|By Timothy B. Wheeler, The Baltimore Sun

The Chesapeake Bay's beleaguered oyster population spawned a bumper crop of babies last year, state officials announced Monday, and there are signs that the diseases that have ravaged the bay's bivalves for more than two decades might have loosened their stranglehold.

Gov. Martin O'Malley heralded the "exciting new evidence" from the state's recently completed survey of Maryland waters, adding in a statement that there is "reason to be more optimistic than ever about the recovery of this iconic species."

Others, while encouraged, were more cautious, noting that the bay's oysters have dwindled to 1 percent or 2 percent of their historic abundance, and that at least some of the apparent rebound may stem from favorable weather conditions over the past several years, which are unlikely to last forever.

The two-month survey by the Department of Natural Resources found an average of nearly 80 baby oysters, called spat, in every bushel of shells dredged up from 260 locations checked throughout the bay and its rivers. That's the highest tally recorded since 1997.

The two diseases infecting oysters also appear to be easing, according to an interim report from the federal-state fisheries laboratory in Oxford, officials reported. While Dermo remains widespread, its frequency and intensity are below average for the eighth straight year. MSX appears to be declining again after a spike in 2009.

Though harmless to humans who might eat an infected oyster, the two parasitic diseases tend to starve young bivalves before they can reach harvestable size. At their worst in 2002, the diseases were blamed for killing 58 percent of the state's oysters. But DNR biologists found the lowest percentage of dead oysters last fall — 12 percent — that they've seen since 1985, before the outbreak began.

The bay's oysters are closely watched as an indicator of the bay's struggling health because they filter the bay's water as they feed. The bivalves once sustained a thriving seafood industry, but have declined over the past 130 years from overharvesting, destruction of their reef habitat and — in the last several decades — disease. Before the onset of MSX and Dermo in the 1980s, annual harvests still exceeded 1 million bushels. The catch has averaged 100,000 bushels in recent years.

State fisheries director Tom O'Connell said the fall survey results show "some evidence that the native oyster may be establishing some disease resistance." He said the young bivalves that were produced last year will help seed the sanctuaries the state set up last year in an attempt to rebuild the bay's population.

The O'Malley administration expanded the network of sanctuaries placed off-limits to commercial harvest from 9 percent of the remaining oyster bars to 24 percent. It also opened up new areas of the bay for leasing by private oyster farmers.

Since last fall, 26 people have applied for 35 new leases to raise oysters, officials said. The state plans to distribute more than $2 million in startup assistance for such aquaculture ventures.

William Goldsborough, senior fisheries scientist with the Chesapeake Bay Foundation, said the news shows the merit of continuing to try to restore the bay's native Eastern oyster. Two years ago, officials from Maryland and Virginia and the federal government rejected proposals to introduce disease-resistant Asian oysters in the bay, saying the risk of ecological disruption was too great.

Kennedy T. Paynter Jr., an oyster researcher with the University of Maryland, said the state survey matches his own findings in the state's sanctuary areas.

But he cautioned that the positive trends were still too short-lived to support the conclusion that the oyster population is coming back after decades of decline. The bay's remaining oysters have benefited from nearly 10 years of relatively rainy weather, he pointed out, which has kept the salinity of the water down and depressed the diseases.

He said the oysters' disease resistance won't really be tested until another severe drought brings conditions conducive to the diseases.

"We've still got a long road," Paynter said, "but I think this is definitely a step in the right direction."

tim.wheeler@baltsun.com

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