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The Gulf of Maine is simmering, but its lobsters seem fine — for now

The Gulf of Maine is warming faster than almost anywhere on Earth, putting the ecosystem at long-term risk

A lobster close-up photo at James Hook & Company in Boston Seaport. (Kevin Ambrose)
6 min

Many tourists visiting coastal Maine may at some point purchase a lobster roll, with big chunks of lobster meat, a dash of mayo and a bag of potato chips on the side. But as summers become hotter and sea temperatures rise in the Gulf of Maine, there’s concern that warmer waters will cause the cold water crustacean to move elsewhere, making it harder to satisfy lobster cravings for the region’s tourists.

The Gulf of Maine has been a hotspot for ocean warming, increasing at a rate of 0.8 degrees Fahrenheit each decade in the last 40 years — about three times the global average. At higher water temperatures, lobsters hit what is known as a “stress threshold,” where they become more vulnerable to disease and less likely to reproduce.

But at least in recent years, it seems, the lobster — and some locals who depend on them for their livelihoods — have found success even as their future in warming ocean waters is more uncertain.

The 2022 catch is strong so far, lobstermen told The Washington Post, although they note it’s too soon to know if it will match last year’s record season, when lobster landings exceeded 200 million pounds.

Patrice McCarron, executive director of Maine Lobstermen’s Association said some of the largest lobster populations have shifted northward since the 1970s or to deeper waters as temperatures in the Gulf of Maine rise.

Still, McCarron said, “lobsters are still in southern and Midcoast Maine, where we continue to have a slow but steady increase in landings.”

Adapting to warmer waters

Lobster season in the Gulf of Maine, which runs from the tip of Cape Cod up to Nova Scotia, peaks from June through November. The season was initially established to coincide with tourist season in New England. Years ago, when lobsters did not transport as well to consumers, the season was planned for when the customers could travel to them. With strong demand, Maine lobster products are now transported worldwide, fueling tourism and economic development in the region.

As summers become warmer, the lobster industry has taken steps to adapt to warmer temperatures, something that has so far helped to keep their business afloat amid a rapidly changing climate.

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“The industry has adapted in a variety of ways — from on-boat handling practices to keep lobsters alive and healthier in high temperatures, to more flexible transportation and processing capacities, and to a greater diversity of market outlets for lobster,” said Kathy Mills, a research scientist with the Gulf of Maine Research Institute.

In addition, many of the lobsters’ primary predators, such as cod and haddock, have decreased due to overfishing, McCarron said.

Size limits are also in place for lobster catches to protect small and oversized lobsters, generally over three pounds. Small lobsters are returned to the water to grow to maturity, and oversized lobsters are protected for life, which allows them to mate. Egg-bearing females are also returned to the water with a notch cut in their tails to indicate to other lobstermen to throw them back if caught again.

The Gulf of Maine also has a unique marine layer called the thermocline, where temperatures abruptly drop to much chillier levels at a depth typically shallower than 50 meters and the lobsters can thrive. While water temperatures at the surface continue to warm, temperatures at the bottom remain cold, reinforced by snow and ice melt each spring. Intense storms and even tropical systems can temporarily mix the warmer water to the bottom, but McCarron says that the lobster can tolerate short periods of warmer water.

An uncertain future

Although many lobsters are appearing to fare well this season, the summer heat hasn’t let up. This summer, a temperature of 68.8 degrees Fahrenheit was recorded in the Gulf of Maine, an all-time record. According to Gulf of Maine Research Institute, this year’s has been the fourth warmest summer on record overall, coming in behind 2021, 2012, and 2020.

Much of the summer temperature increases can be blamed on marine heat waves — a period of five or more days where sea surface temperatures are in the 90th percentile compared to average.

“A new [marine] heat wave event began on June 25 and has continued through today,” Adam Kemberling, a research technician from the Gulf of Maine Research Institute, said in early September. “The recent strong influence of the Gulf Stream will tend to keep temperatures here warmer relative to the past, but this area has a lot of seasonal and interannual variability; fall storms or other weather patterns could disrupt the current heat wave.”

The Gulf of Maine, warming faster than 96 percent of the world’s oceans, is uniquely vulnerable to these marine heat waves, which could portend a concerning future for area lobsters.

Past lobster seasons have already been affected by these heat waves.

In 2012, an early-season marine heat wave caused the lobster catch to ramp up earlier than normal in the spring, leading to a price collapse. The heat wave contributed to the warmest spring and second warmest year on record in the gulf. That summer forced the industry to adapt, and there has not been a marine heat wave-related disruption since.

While this summer’s temperature highs didn’t seem to disrupt the year’s catch, researchers are worried about future seasons.

Katie Wagner, a spokesperson for National Oceanic and Atmospheric Administration Fisheries, said projected warming over the next 80 years suggests deeper and colder areas of the Gulf of Maine will increasingly become the only areas suitable for lobster habitats. Lobster will be able to thrive to the north, further away from popular lobstering areas right off the coast of southern Maine.

“Warming ocean waters due to climate change are forcing American lobster populations to a deeper and more northerly distribution than ever before,” Wagner said. “Lobster populations are increasing at the cooler (northern) edge of their range, and declining at the warmer (southern) edge of the range due to reproductive failure — fewer juvenile lobsters living to adulthood to reproduce.”

Mills also warns that deeper water layers will also be impacted long-term by temperature rises, which could affect the thermocline layer.

Scientists see stronger evidence of slowing Atlantic Ocean circulation, an ‘Achilles’ heel’ of the climate

“Deep waters in the Gulf of Maine have been warming as well, and in much of the gulf, surface and bottom temperatures are correlated with one another,” Mills said.

In nearby areas without a protective thermocline layer, lobsters have already fled the area. In the coastal waters south of Cape Cod, warming sea temperatures from climate change have dramatically reduced lobster populations, leading to the collapse of the local lobster industry over the past four decades.

According to NOAA, registered lobster landings dipped by 97.7 percent in New York state from 1996 to 2014. In Connecticut and Rhode Island, lobster landings have dipped 96.6 percent and 70.3 percent from their most profitable years, respectively.