The American lobster, an economic anchor and cultural symbol of Maine, is shrinking, according to a forthcoming study to be published at Fisheries Research.
As ocean temperatures from Rhode Island to New Brunswick have risen over the previous decades, lobsters are maturing earlier and at smaller sizes. In the study led by scientists at Portland’s Gulf of Maine Research Institute, the research team used advanced mathematical modeling to project the effects of rapidly warming waters on the future growth of lobsters.
The research not only links shrinking lobsters to the rise in ocean temperatures, it even puts forth a mathematical model that estimates the size at which a lobster will mature. The study’s findings and its formula are intended to aid fisheries in adaptive management strategies that account for the effects of climate change.
“The study demonstrates that lobster growing in warmer weather mature at a smaller size,” says Arnault Le Bris, a co-author of the study. “If warming trends continue, you can expect lobster to grow at increasingly smaller sizes.”
Andrew Pershing, the chief scientific officer at the Gulf of Maine Research Institute, points to the impacts that have already hurt regional fisheries in southern New England and the mid-Atlantic.
“You look at Rhode Island and Long Island and the fishery there is basically shut down, and that looks very much like a temperature effect,” Pershing says. “They hit a point where the lobster population couldn’t thrive the way it used to thrive.”
Though the warming ocean temperatures have severely damaged the lobster economy to the south, those same rising temperatures have had the opposite effect in Maine, where the once cooler waters have for several years been at near ideal conditions for record lobster catches. But how long until the ocean temperatures along the coast of Maine reach the levels that doomed Rhode Island’s fishery?
The waters across the Gulf of Maine, Pershing explains, are warming at a rate four times the global average. Climate change effects are being felt in this region, and those effects are being reflected not only by the temperature of the water, but also the size of its lobster.
The data gathered by Le Bris, Pershing, and their colleagues show a decline in the size of mature female lobsters from Rhode Island to Maine, with New Brunswick’s colder waters allowing for larger lobsters to thrive. A portion of Maine’s coast, roughly from Rockland to Bar Harbor, showed a significant decrease in carapace length, as measured by the distance between the eye socket and the beginning of the tail.
In 2000, the average mature lobster in this region of Maine had a carapace 97.61 millimeters long. That number was estimated to be below 93 millimeters from 2007 to 2014, the last year with data presented in this study.
“Size at maturity is critical in terms of fishery management,” Le Bris says. “If climate change modifies the size of maturity in lobster, then you will need to adjust your management plan.”
Le Bris and Pershing agree that they are not prepared to offer concrete recommendations to fisheries on adjustment plans to this trend, such as lowering the minimum size requirement put in place by the fishery. Their study, instead, lays the groundwork for formulating a comprehensive management plan.
Cultural Heritage at Risk
The potential economic consequences for coastal communities in Maine are serious, but the lobster’s importance does not end there. It has been a centerpiece of the region’s cultural identity for decades. Pershing, who has lived in Portland, Maine, for more than 10 years, has witnessed the cultural significance of the lobster firsthand, and cites it as a motivating factor for further research.
Consider also the example of Rockland, a working water front town of 8,000 residents about a 90 minute drive north of Portland. For the past seventy years, the town has celebrated the Maine Lobster Festival, bringing tens of thousands of visitors to the small town, which serves up 20,000 pounds of lobster with the help of 1,100 volunteers.
While the scientists insist that more research must be done, there is concern for the potential cultural and economic repercussions as the waters in the Gulf of Maine continue to heat up.
“It is really important in terms of tourism. Lots of people come to Maine expecting to eat lobster,” says Le Bris. “A lot of coastal communities in Maine and the economy of the state can be threatened by the effect of climate change on lobster fisheries.”
–Tom Doherty is a senior at Northeastern University studying English/linguistics and journalism. His previous writing has appeared in the Newton TAB and a number of local newspapers on Massachusetts’ North Shore, where he grew up.
Photo Credit: Anders Pearson — Flickr