In this Jan. 6, 2012, file photo, gulls follow a shrimp fishing boat as crewmen haul in their catch in the Gulf of Maine. Credit: Robert F. Bukaty / AP

Scientists said the highest water temperatures ever in the Gulf of Maine were recorded last year.

The gulf is one of the fastest-warming bodies of water on the planet, and fishermen are noticing signs of the change.

Data released by the Gulf of Maine Research Institute show that last year surface water temperatures in the gulf were on average a half-degree higher than the previous record, with record highs recorded on 169 days — almost half the year.

The gulf experienced what scientists now call a “marine heatwave” for the entire year.

“As unusually warm as 2021 was in a historical context, it’s likely to be one of the coolest years we’ll experience going forward, especially if we’re not able to reduce greenhouse gas emission globally,” the institute’s David Reidmiller said.

Reidmiller said the latest data punctuate a decades-long trend that shows no sign of abating.

“The warming trend is unequivocal in the Gulf of Maine. It’s been going on now for decades, and from a climatological sense we are assuredly in a new regime,” Reidmiller said.

The gulf extends from Cape Cod to Canada, and is warming partly due to massive ice-melt from the Arctic. That pulse of cold, fresh water is changing the course of long-established ocean currents, allowing relatively warm Gulf Stream waters to push closer to New England’s coast.

The high surface-water temperatures are an indicator of change observers are seeing throughout the gulf’s ecosystems. Steve Train harvests lobster and grows seaweed off Casco Bay’s Long Island.

“My kids have been catching squid off the dock at night, for years now. I never caught squid off the dock,” he said.

Ten years ago, newly-abundant squid may have played a decisive role in the collapse of a local population of cold-water Maine shrimp that likely were already stressed by warming temperatures.

In 2012 — the previous record-holder for hottest in the gulf’s waters — scientists said evidence shows that voracious longfin squid feasted on the shrimp, which have yet to recover.

Train said a variety of more southerly species are showing up these days, and not just in summer.

“We’re catching sea bass in our traps, frequently. Not occasionally, not just in the month of June or something. Last time we went out hauled we had two sea bass in 45 fathom of water. We didn’t, we didn’t use to see that,” he said.

What’s the latest species fishermen are seeing come around more often, even in winter? What the South knows as Chesapeake blue crab.

“I think that very much the Gulf of Maine is going to be the crystal ball showing us the future of ocean management,” said Gib Brogan, a fisheries analyst at Oceana, an international conservation group.

He said that as marine species shift their territory in response to climate change, regulators will be challenged to keep up. He adds that fisheries decisions in the Gulf of Maine already are some of the most contentious in the world.

“Whether it’s lobster or groundfish … herring management. If a progressive, climate-ready strategy can be adopted in the Gulf of Maine, I think that bodes well for applying it elsewhere,” he said.

And with the Gulf of Maine warming almost three times as fast as the planet’s oceans overall, the researchers say, it provides a glimpse of the future not just for commercial fisheries, but for ocean ecosystems and coastal economies worldwide.

Preliminary data indicate that Gulf surface water temperatures remain high in 2022 — hovering around three degrees above the historical norm — and that the marine heatwave continues.

This article appears through a media partnership with Maine Public.