Warming ocean waters are not only making it difficult for oysters to develop the shells critical to their survival, but now the heat is also making it easier for diseases to spread that can get under lobsters’ shells and cause lesions, killing them.
The lobsters’ epizootic shell disease is found in warm waters, where bacteria can move quicker. In one recent study, researchers found that the disease bacteria responsible for the rapid deterioration of lobster shells, is first detected around 50 degrees Fahrenheit, at which it moves slowly. Between 60 and 68 degrees, the bacteria spreads at an even greater intensity, and can infect new lobster shells as soon as an old shell is molted.
The disease itself is not always fatal, but leaves affected lobsters more susceptible to invaders. In the most extreme cases, lobsters can die from the disease if the bacterial infection stresses the lobster, preventing it from molting. Even if a lobster survives, its discolored shell makes it unmarketable.
According to a 2015 study on epizootic shell disease in lobsters, the disease is most common in southern New England, the Long Island Sound, Connecticut, and Rhode Island. However, “since 2000, the prevalence of disease in these affected areas increased 20 to 38 percent annually. Marine biologists and lobster fishery personnel fear that the disease will eventually spread to more northern waters, including those along Cape Cod, Maine, and Nova Scotia, which are home to the largest and most economically important lobster breeding grounds.”
Previous studies on the effect of rising ocean temperatures in the Gulf of Maine — where scientists previously recorded the waters to be heating up 99 percent faster than the rest of the oceans — found that the temperatures are changing the types of species that show up in fishermen’s nets, as lobster, shrimp, cod, and herring, move up north, while species like blue crabs and squid show up in Maine.
“Shell disease has devastated the southern New England lobster fisher[ies], and now with warming, it’s created a situation where the Maine lobster industry may be at risk,” said Jeff Shields, a professor of marine science at the Virginia Institute of Marine Science. “Scientists are working with us to look out for increased lobster shell disease levels this spring.”