Studies: Warming waters, local conditions contribute to Maine's lobster stock changes

Photo / Laurie Schreiber A pair of new studies say that warming ocean waters contribute to the rise and fall of lobster populations in the Gulf of Maine. Wharfs along Maine’s coast remain busy through the fishing season.

Write a Comment

By Staff

Two new studies published by University of Maine scientists point to the role of a warming ocean and local oceanographic differences in the rise and fall of lobster populations along the coast from southern New England to Atlantic Canada.

Maine's lobster catch was valued at $484.5 million last year, according to the state Department of Marine Resources. It is the state's largest fishery by far, accounting for 76% of the $637 million fishing industry — making the findings that much more significant.

One study suggests the Gulf of Maine lobster fishery may be entering a period of decline, as a “cresting wave” of lobster abundance heads northward in response to the region’s changing climate.

Published in the scientific journal “Ecological Applications,” the study was led by Noah Oppenheim, who completed his research as a UMaine graduate student in 2016, with co-authors Richard Wahle, Damian Brady and Andrew Goode from UMaine’s School of Marine Sciences, and Andrew Pershing from the Gulf of Maine Research Institute.

But the other study says that baby lobsters, which later reach a harvestable size, appear to be finding refuge from warming waters in cooler deep-water habitats. That, perhaps, provides a buffer from declines in Maine’s lobster fishery.

Published in the journal “Global Change Biology,” the study was led by current UMaine marine science Ph.D. student Andrew Goode and co-authored by Brady, Wahle and Robert Steneck, all of the School of Marine Sciences.

Both studies take advantage of the American Lobster Settlement Index, according to a news release.

Initiated in 1989, the index is an annual monitoring program that quantifies newly settled lobsters at more than 100 sites along the New England and Atlantic Canada coast.

Quantifying the number of baby lobsters is considered useful as a predictor of future trends of adult lobsters in the fishery.

The index was founded by Wahle, who besides serving as a UMaine research professor is director of the Lobster Institute. The index is a collaboration of government marine resource agencies, academic institutions and industry members who undertake and pay for the divers and boats needed to conduct the survey. Wahle’s lab serves as the data hub.

“No one has a crystal ball, but in a field where sweeping statements are made about the global impacts of climate change, these studies underscore the importance of having a fine-scale, local understanding of both oceanography and organism biology as we project the impacts of a changing climate on the future of our coastal communities and economy,” Wahle said in the release.

Cresting wave

The “cresting wave” study report that the numbers of young-of-year lobsters populating shallow coastal nursery habitats each year, along with temperature, provide a reasonably accurate prediction of trends in the lobster fishery some four to six years later.

The model predicted regional differences in the recent record-breaking lobster harvests over the past decade. But it now suggests the Gulf of Maine lobster fishery may be entering a period of decline.

“Our model projects that the Gulf of Maine’s lobster landings will return to previous historical levels,” Oppenheim, who is now executive director of the Pacific Coast Federation of Fishermen’s Associations and the Institute for Fisheries Resources in San Francisco, said in the release.

“These results don’t suggest a lobster crash, but this tool could give the fishing industry and policymakers additional lead time as they make decisions about their businesses and communities in the years ahead.”

Brighter side

The second study underscores the importance of local differences in the oceanography of the Gulf of Maine for understanding where the lobster boom occurred. The analysis suggests there’s a complex interplay between lobster larval settlement behavior, climate change and local oceanographic conditions.

The authors observed that an expanded area of thermally suitable habitat for larval settlement in the eastern Gulf of Maine may have helped drive and amplify the lobster boom in the region over the last decade, a boom that elevated the fishery to its current status as the most valuable single-species fishery in the nation.

Although the paper points to a “brighter side of climate change” in this case, it does not deny the adverse effects of a warming ocean south of Cape Cod for other species.

Maine lobster landings peaked in 2016, when 132.6 million pounds were harvested, after four years in the range of 122 million to 127 million pounds. In 2018, Maine's lobster harvesters landed 119.64 million pounds, the seventh time in history that landings exceeding 110 million pounds.