Lobster Shell Disease Moving Toward Maine

Portland, ME — A disease that eats away at the shells of lobster is moving northward toward Maine.

Only three out of every 1,000 lobsters sampled in the state last year had the disease, which is caused by bacteria, but scientists and lobstermen are concerned that number will grow. From 2010 to 2012, the prevalence of lobster shell disease grew fivefold.

Lobster shell disease isn’t harmful to humans, nor does it taint the lobster’s meat. It does, however, make the shell so unappealing that they are unappetizing to serve whole. It also stresses the lobsters and can sometimes kill them. If the disease gets very bad, it can stop Lobsters affected by the shell disease can still be processed and used for canning.

The disease usually goes away when the lobster sheds its shell. But larger female lobsters are the most severely affected by the disease, since they retain their shells for longer periods while carrying eggs. The disease can weaken the lobster so much that it is unable to carry its eggs to term.

Kathy Castro, a fisheries biologist at the University of Rhode Island Fisheries Center, said the disease can be linked to factors such as rising water temperatures, low oxygen levels in the water, and pollution.

The disease is less prevalent in the colder water of the Gulf of Maine, which stretches from Cape Cod to Nova Scotia, than it is in southern New England.

“It’s certainly something to keep an eye on. But in terms of our perspective of Gulf of Maine shell disease, we don’t see it as something to get particularly concerned about,” said Tracy Pugh, a fisheries biologist with the Massachusetts Division of Marine Fisheries. “The rates are pretty low. We don’t see a pattern.”

Carl Wilson, the state of Maine lobster biologist with the Department of Marine Resources, said it is too soon to say if the increase in Maine is the beginning of an upward trend. It could be an anomaly based on the record-high ocean temperature in the state last year. From 2008 to 2010, about one in every 2,000 lobsters sampled in Maine had the disease. In 2011, it was four in every 2,000. In 2012, six in every 2,000 lobsters had the shell disease.

Climate change may also be to blame for the rise in lobster cannibalism. As waters grow warmer, lobsters produce more offspring and they grow larger. The cannibalism occurs when there are too many lobsters and not enough natural food.

[Photo credit: Rhode Island Sea Grant]