Maine Fishing Industry

Maine sees uptick in shell disease

Posted:  Wednesday, August 14, 2013 - 5:00pm

Although not widespread, there is a precedent for a blight that has started infecting Maine lobsters.

A shell disease, which has become widespread in the warmer waters south of Cape Cod, has shown an increased presence in the Gulf of Maine.

Although the number of lobsters it has effected in Maine is small, in recent years it has started to spread and grow.

Dr. Richard Wahle, University of Maine School of Marine Sciences research professor, has done research on the effects and trends of shell disease in lobster populations in Southern New England.

“In a nutshell in (Rhode Island) we used to be able to predict trends in the abundance of lobsters entering the fishery solely on the basis of a larval settlement index,” he said. “When shell disease hit we had to include shell disease prevalence in the breeders as a second variable in the predictive model for it to be accurate.”

The disease does not render the lobster inedible, but Wahle noted that a pitted, diseased lobster is a harder sell.

“It's a bacterial infection often with secondary infections that create ugly pits in the lobster shell,” he said. “It is not contagious to humans. But severe cases can and do kill lobsters. To my knowledge there is no effective treatment that is not also harmful to the lobster.”

Maine's population of lobsters with shell disease is believed to be less than 1 percent of the total population. Rates in southern states, such as Rhode Island, feature populations where nearly one-in-five lobsters have the disease.

While Maine's disease rate is small, it has increased in recent years, though the percentage is still relatively tiny compared to Maine's southern neighbors.

Wahle said rising ocean temperatures link with the disease, and that as water temperatures rise, so do occurrences of the disease.

“The prevalence of shell disease does correlate with patterns of temperature in New England,” he said. It is most prevalent in the warm waters of southern New England, south of Cape Cod and falls to lower rates the further north you go in the Gulf of Maine.”

There is a precedent for the disease to follow warmer weather, Wahle said.

“The onset in southern New England back in the late 1990s occurred after a consecutive series of warmer-than-average years,” he said. “The recent uptick of shell disease in (Maine) over the past couple of years has come at a time when we have seen the warmest sea temperatures on record.”

Ben Bulkeley can be reached at 207-633-4620 or Follow him on Twitter: @BBRegisterBen.