Chesapeake's Rockfish Overrun by Disease
Saturday, March 11, 2006
A wasting disease that kills rockfish and can cause a severe skin infection in humans has spread to nearly three-quarters of the rockfish in the Chesapeake Bay, cradle of the mid-Atlantic's most popular game fish.
The mycobacteriosis epidemic could carry profound implications for the rockfish, also known as striped bass. The fish fuel a $300 million industry in Maryland and Virginia, but because the bacteria kill slowly, effects on the stock are only now emerging.
The disease also sends a grim message about the entire bay ecosystem. The rockfish remains bay conservationists' only success story -- a species nearly wiped out, then revived by fishing limits.
But as the number of rockfish surged, the fish remained in a body of water too polluted to support the level of life it once did. That made them vulnerable to a malady researchers did not see coming -- a signal, some scientists say, that controlling fish harvests is no longer enough to ensure long-term survival of a species.
"We used to think that if you got hold of fishing, all your problems would be solved," said James H. Uphoff Jr., a biologist at the Maryland Department of Natural Resources. "But now all these ecological problems crop up, and we don't understand them."
Indeed, nearly a decade after mycobacteriosis first appeared, scientists remain utterly baffled about its implications, including those for humans. Researchers know that the Chesapeake, where most rockfish spawn, also breeds the bacterium and is the epicenter of the disease. Yet they don't know how or why it appeared, whether it will spread to other species or if the infection it causes is always fatal.
A new study suggests that since the illness was discovered among bay rockfish, non-fishing mortality among them has tripled in the upper bay. But scientists cannot explain why, at the same time, anglers are catching plenty of fish.
In humans who touch the fish, the microbe can cause a skin infection known as fish handler's disease, which is not life-threatening but can lead to arthritis-like joint problems if untreated. Watermen say the only sick fish they see are in small, overcrowded rivers and streams. The netting season that ended Feb. 28 "was a super-good season as far as catching, and a good season as far as the price," said Larry Simns, president of the Maryland Watermen's Association. With no evidence of health risk from eating the fish, watermen say, prices have remained stable.
But at Ristorante Tosca in downtown Washington, "some people ask, 'Is it safe?' " chef Massimo Fabbri said of the rockfish on the menu. Such questions have prompted Fabbri to buy the restaurant's wild rockfish from Northern Europe and Ecuador, paying about three times what he would for local bass. "Wouldn't you?" he asked.
As researchers test a long list of hypotheses, they say their search for the bacterium's source and implications highlights the limitations of modern science when pitted against the complexities of the wild.
"Scientists attempt to unravel things [and] are supposed to follow the information wherever it leads us," said Victor Crecco of the Connecticut Department of Environmental Protection, author of the mortality study. "We're going to have to do more work to explain these contradictions."
For centuries, striped bass fishing has been as rich in lore as it was in quality. In ideal conditions, rockfish can live up to 30 years: The biggest on record was a 125-pound female, landed off North Carolina in 1891. In this region, charter boat operators tell of swimsuit-wearing amateurs landing dozens of the silver-scaled fighters in a day -- the fish longer than one's arm, bellies made fat on the teeming schools of menhaden that are a chief food source.