New model predicts Downturn in lobster landings

Lobstermen may see a decline in their lobster landings in the near future, according to a study published in the journal Ecological Applications in October. The lead author of the paper, titled “The cresting wave: larval settlement and ocean temperatures predict change in the American lobster harvest,” is Noah Oppenheim, now executive director of The Institute for Fishery Resources in California, and former graduate student of University of Maine Lobster Institute director Richard Wahle, a co-author.
The study draws on a computer model based on data from the American Lobster Settlement Index, an annual survey of juvenile lobsters at 62 near-shore sites from Rhode Island to New Brunswick, Canada. The forecasts cited in the study are based on an improved version of a model which incorporated local bottom temperatures and the prevalence of diseases, such as shell disease, with the settlement data. “On the strength of these analyses, we project landings within the next decade to decline to near historical levels in the Gulf of Maine and no recovery in the south [New England],” the authors stated. Specifically, the study predicts that landings will fall 20% to 40% in the next four to five years in much of eastern Maine, and by more than 90% in eastern Penobscot Bay.
Such a decline would come as a shock to many lobstermen who have pursued their livelihood during two decades when lobster landings in Maine jumped dramatically. Up until 1990, Maine lobstermen landed around 20 million pounds each year. After that year, the figure began to climb: 30 million pounds in 1991; 50 million in 1999; 80 million pounds in 2009; 132 million pounds in 2016; 119 million pounds in 2018. A drop of 20% to 40% would have far-reaching economic impacts throughout Downeast Maine.

As the Gulf of Maine has warmed, habitat suitable for juvenile lobsters has expanded into deeper water while settlement has declined in nearshore areas. MLMC photo.

“No one expects lobster landings to continue to increase forever,” said Patrice McCarron, executive director of the Maine Lobstermen’s Association. “But you have to put this study into a broader context. The Settlement Index may not be capturing everything because it is conducted very close to shore and the state’s other lobster monitoring surveys, including the ventless trap and trawl surveys, have not detected a decline.”
Lobstermen are still seeing many juvenile lobsters in their traps. That could be due to the upward climb in water temperatures throughout the Gulf of Maine. The Settlement Index sites are in shallow areas in water temperatures above 54oF. where young lobsters typically settle after completing their larval stages. But a second paper, “The brighter side of climate change: How local oceanography amplified a lobster boom in the Gulf of Maine”which came out in the journal Global Change Biology this month, suggests that as the Gulf has warmed, the extent of underwater habitat suitable for young lobsters has expanded. In eastern Maine, where strong tides churn warm surface water down to the seafloor, there are more deep-water places where a young lobster can settle down and thrive.
“… We argue that ocean warming drove a northeastward [lobster] population surge in the Gulf resulting from an expansion of the area of seabed across a biologically important thermal threshold for larval settlement. We suggest this northeastward expansion largely contributed to the historic six-fold increase in lobster harvests that has elevated the fishery to its high national ranking in value,” the paper’s authors, one of whom is Wahle, stated.