Rampant Lobster Disease Mystifies Scientists
NARRAGANSETT, Rhode Island Scientists and fishermen tried to tackle the problem of Southern New England's dying lobsters yesterday afternoon, but after hours of talk it looked like they were stuck in the first 15 minutes of a crime-scene mystery. Any solution seemed a long way off.
Shell disease, a bacterial affliction of lobsters' shells, has always been around, scientists said. But it was usually a minor disfigurement.
Since 1996 in Rhode Island, water conditions have swung out of control. No one has seen the disease be so virulent and so common. It's believed to be killing vast numbers of lobsters. Those that survive are horribly scarred, and unsaleable.
The value of Rhode Island's lobster catch has declined from $30 million in 1999 to half that last year, according to Mark Gibson of the state Department of Environmental Management. The number of lobster fishermen has dropped from 420 to 279.
In parts of Narragansett Bay, up to 45 percent of the thousands of lobsters sampled were afflicted, according to DEM biologists.
The disease has increased the natural morbidity of lobsters from 15 percent each year to as much as half, biologists said.
None of the dozens of scientists and fishermen who attended a symposium at the University of Rhode Island's Coastal Institute yesterday pretended to understand what was going on. But several theories came up repeatedly: rising water temperature, chemicals in human wastes, or killer microbes from other lands.
There was general agreement that little more will be learned until someone finds more money for research.
Several fishermen insisted the disease coincided with the North Cape oil spill in the winter of 1996.
"I know to the last man in the Rhode Island fishing industry, everybody believes it's the oil spill," said Gibson. "But if that's the case, how do we explain Long Island Sound and Buzzards Bay and Cape Cod Bay. I realize it was a large loss, but I don't know how it could trigger change in all of Southern New England."
Other clues were offered.
In Rhode Island, the closer to shore, the more disease. Tom Angell, a DEM biologist, said the average rate of disease inshore is 25 to 30 percent. Offshore, it is only 5 percent.
Females are hit much harder than males.
More than half the egg-bearing females are afflicted. The theory is that they carry their shells longer than males, so there is more opportunity for the bacteria to attack.
The disease rate goes way down in the summer. That's when most lobsters molt and shed the disease along with their shells.
Bob Glenn, a biologist with the Massachusetts Division of Marine Fisheries, said that while Massachusetts has long seen minor problems with shell disease, it didn't start getting bad until 1997, when fishermen working around the Elizabeth Islands in Buzzards Bay started calling.
In 1998-99, conditions worsened in Buzzards Bay, Glenn said. In 2000, the disease moved into the Cape Cod Canal. Then it moved to Cape Cod Bay. By fall of 2000, it reached Boston Harbor.
In summer 2001, it showed up on the outer Cape. In 2002, it was found in Beverly, on the North Shore. In 2003, Glenn said the disease struck lobsters farther north, at Cape Ann.
The disease seemed to be spreading as if it was contagious.
There was a temptation to look at pollution as a cause, because Buzzards Bay has had its share, Glenn said, But he noted the worst spot in Buzzards Bay remained around the Elizabeth Islands, not close to cities such as Fall River or New Bedford. Also, Boston Harbor has not been a hot spot, despite the intense development that surrounds it.
Glenn says he wants to further investigate water temperature as a cause, because wherever the disease is worse, year-round water temperatures are the highest.
(Last fall teams of scientists concluded that the crash of the lobster fishery in western Long Island Sound in the fall of 1999 was due to a "Perfect Storm" of weather events that raised water temperature, lowered oxygen levels and created other stresses. Many afflicted lobsters there had shell disease, too.)
Roxanna Smolowitz, a veterinary pathologist at the Marine Biological Laboratory in Woods Hole, Mass., studied lobsters from Rhode Island, Massachusetts, Connecticut and Maine that were stricken with shell disease.
She determined the crustaceans were attacked by bacteria from outside their shells. In every case they were attacked by a single kind of bacteria that also causes skin infections in other animals.
Hans Laufer, from the Department of Molecular and Cell Biology at the University of Connecticut, said that in many of the lobsters he studied, and in sediments on the bottom, he found four kinds of alkylphenols, chemicals used in detergents, paints and plastics.
The chemicals are hormone disruptors, Laufer said, and could be disrupting lobster growth and making them susceptible to shell disease.
More than 500,000 tons of the chemicals are produced each year, and 60 percent end up in aquatic environments, Laufer said.
Kathleen Castro, the symposium organizer, cautioned that the disease remains a puzzle. "You understand we don't have the answers yet. We're starting to get some answers. But it's going to require a lot more work and a lot more money."
"You have to ask what happens when a long-lived species becomes a short-lived one," Castro added. "What do you do when they're dying faster than they're growing. Should you try to catch them before they die?"
Stan Cobb, a URI biologist, added, "I've been working on lobsters around Narragansett Bay for more than 30 years, and in that time nothing has given me as much concern as this last decade with the shell disease."
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