Media coverage this summer on the lobster industry in Maine has focused on the rise of shell disease in the state, according to Penobscot East Resource Center Fisheries, Science & Leadership Advisor Carla Guenther.
Guenther opened the final Penobscot East summer series talk on Thursday, August 29, with a reminder to those present that shell disease prevalence is still less than 1 percent. In southern New England—off the coast of Rhode Island and Massachusetts—the rate of shell disease is as much as 30 percent.
Shell disease is a bacterial infection found on some lobsters that creates pock marks and other deformities on the shell of the lobster. While the meat remains unharmed and is safe for human consumption, the shell’s less-than-appealing appearance devalues the product. Lobsters can shed the disease when they molt, and their new shells won’t necessarily have the disease. It is most often seen on older lobsters and on females who have skipped a season of molting because they were producing their eggs—that is, animals that have had their shell for longer.
Kathleen Reardon, who coordinates the lobster sea sampling program for the Maine Department of Marine Resources, spoke about shell disease in Maine’s lobster population. The sea sampling program makes 21 trips per month in June, July and August, three each in the seven zones and on more than 100 boats, to collect data on the lobster population.
“Sixty-five percent of the ex-vessel value of all fisheries landings in the state are from lobster,” Reardon said. This is why it is so important to keep tabs on the health of the lobster population. The program counts discard rates of sublegal and oversize lobsters, as well as v-notch lobsters and counts sex ratios of the lobsters.
“Right now there’s an abundance of sublegal [short] lobsters,” said Reardon. This means there is likely a very large lobster population on bottom.
Shell disease is a concern because of the damage it does to the value of the lobster. There is a lot of misinformation about shell disease, said Reardon. Shell disease is caused by bacteria, but that bacteria is found on nearly all lobsters, not just ones with shell disease. Likely, stressed lobsters are susceptible. Warm water and pollution can contribute to stress for lobsters, said Reardon, which could explain why the rate of disease is so much higher in the warmer, more traveled waters down in southern New England.
Shell disease is not contagious from lobster-to-lobster, said Reardon, though many fishermen don’t believe it.
“I was having dinner with an 80-year-old fisherman the other day and he was telling me that he kills every shell disease lobster he sees,” said Stonington fisherman John Williams.
Shell disease has been around for years, but it has become more noticeable for several reasons, said Reardon. First, the rate of shell disease in southern New England. Second, Maine is landing more lobsters than ever, and therefore landing more lobsters with shell disease.
That said, Reardon continued, the rate of shell disease in Maine has tripled, though it remains under 1 percent of the total catch statewide, and less than 1 percent in all zones except for Zone G, the most southerly zone. In Zone C, only approximately 3.5 out of every 1,000 lobsters caught have shell disease.
The increase may be due, in part, to 2012’s unusually mild winter and very warm summer, which broke records.