Scientists Keep Wary Eye On Lobster Shell Disease

 By Aaron Porter

ELLSWORTH — The specter of lobster shell disease has loomed large over Maine’s lobster fishery for the past two years. The quick spread of the shell-destroying ailment in southern New England since the late 1990s has been one more source of worry for Maine’s lobstermen.

Shell disease pitted the shell of this Maine lobster in 2003.

PHOTO COURTESY OF MAINE DEPARTMENT OF MARINE RESOURCES

Meanwhile, the state’s fishery has been in the midst of an undeniable boom since the mid-1990s.

While lobstermen are generally pleased with the hand they’ve been dealt, they know their luck could change.

Shell disease has amounted to a string of bad luck for Massachusetts and Rhode Island lobstermen. However, Maine waters have yielded relatively few infected lobsters in the last few years.

Maine’s State Lobster Biologist Carl Wilson has maintained a guardedly optimistic outlook since shell disease became a widely discussed issue around 2002. That optimism is supported by the shell disease findings for 2004. In spite of increased vigilance on the part of Maine lobstermen, only 32 infected lobsters were found during sea sampling last year — down from 44 reported cases in 2003.

For practical purposes, the numbers for either year are negligible. Less that 0.1 percent of the total population, Wilson said. That doesn’t mean lobstermen of scientists are becoming complacent about the ailment.

“There’s a general sort of watchfulness,” Wilson said of the lobstermen out on the water tending their gear every day. Back in the laboratory the daily grind of science work continues.

Researcher Charles O’Kelley, who presented some of his work at the 2004 Maine Fishermen’s Forum, is still pursuing the single-celled organisms that live on  diseased shells.

At the forum, O’Kelley said he had isolated more than 200 cultures of amoebae, zooflagellates and diatoms from healthy and diseased Maine lobsters. Narrowing any cause down from such a wide field is a challenge O’Kelley is still working on.

There’s also a riddle of the disease to be solved.

Wilson said there isn’t an understanding of whether the lobster is weakened by something else, which than allows the bacteria and other organisms to thrive on the shell, or whether the actual infestation on the shell weakens the lobster. Whatever the case, he reminded that the symptoms recognized as shell disease can be found in healthy lobster populations. Even in last summer’s survey, diseased shells were seen from Kittery to Eastport with no particular “hot spots,” Wilson said.

Confirming reports from other states, 80 percent of those infected were female, Wilson said. In addition, most were more than 1˝ pounds. He said that all makes sense, because older females are more likely to delay shedding their shells. One way lobsters can be rid of the disease is to shed their way out of infected shells.

Wilson said what he’s been hearing from Massachusetts and Rhode Island that things are looking up for their hard-hit lobster fisheries.

Wilson said one of the factors researchers are looking at is seawater temperature in the region. He said the last two summers have seen lower temperatures than usual off much of the Maine coast.

“The last two years the molt has been delayed,” he said.  But to the question of whether the temperatures are normal or not he asked rhetorically, “what is normal?”

That’s not a bad question for a fishery that has fluctuated dramatically in recent decades along the length of the New England coast.

Patrice McCarron, executive director of the Maine Lobsterman’s Association confirmed that there was been a drop in shell disease reports in 2004. In the interest of keeping lobstermen informed and vigilant she’ organizing a lobster health symposium at the 2005 Maine Fishermen’s Forum in March.

McCarron said she’d have researchers from southern New England states on hand to tell where their investigations of shell disease and the Long Island Sound lobster die-off have led them.

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