Gray whale, long absent from the Atlantic Ocean, spotted off the coast of Massachusetts

Researchers at the New England Aquarium were conducting regular surveys of the waters south of Martha’s Vineyard and Nantucket in Massachusetts last week when something caught their attention.

What they saw, a whale with no dorsal fin, led researchers to think it might be a North Atlantic right whale, a critically endangered species that the aquarium keeps a close eye on. But the whale’s skin was spotty, and if it was a whale, something would have been wrong.

“I had a bit of a strange feeling about it,” Orla O’Brien, a senior university researcher, said in an interview. “Something seemed wrong.”

So when the whale resurfaced and Ms. O’Brien and her observation partner, Kate Laemmle, a research technician, could see its distinctly shaped head and mottled gray-white skin, they couldn’t believe their eyes: Could it be a gray whale are? whale? In the Atlantic Ocean?

“It was really hard to understand it mentally,” Ms O’Brien said.

But it was a gray whale, an aquarium sighting described in a statement Tuesday as “an incredibly rare event.”

Gray whales are regularly found in the North Pacific Ocean, but sightings in the Atlantic Ocean, where the whales disappeared in the 18th century, are extremely rare. Experts say it’s not clear why they disappeared, but whaling may have been a factor.

According to the aquarium, five gray whales have been sighted in the Atlantic Ocean and the Mediterranean Sea in the past 15 years. The most recent occurred off the coast of Florida in December, and the New England Aquarium believes the whale is the same gray whale that researchers spotted off Nantucket last week.

Scientists say climate change is largely responsible for the strange sightings. The Northwest Passage, which connects the Atlantic and Pacific Oceans between the Canadian mainland and the North Pole, has been ice-free during the summer months in recent years, partly due to rising global temperatures. Without ice, gray whales could swim through the passage, something that would not have been possible in the last century, the aquarium said.

The whale spotted by Ms. O’Brien and Ms. Laemmle did not appear to be in bad condition, and the two observed the whale feeding, “which is good,” Ms. O’Brien said.

“But you’re left asking, ‘How did it get to this?’ share,” she said. “Which is not a positive story overall, because these passageways are only being created to allow travel through due to warming temperatures.”

Ms O’Brien said she and Ms Laemmle were unable to assess the whale’s age or sex, but planned to send photos to researchers in the Pacific to help identify it. She also said the only way to track the whale would be to report other sightings.

Joshua Stuart, a quantitative ecologist at Oregon State University, who published a study on gray whales in Octobersaid the gray whale sighting in the Atlantic Ocean was “super cool,” but there were two important contextual elements.

First, whales can swim between ocean basins because of melted ice in the Arctic, which he said is “an expected outcome of climate change.”

Second, said Dr. Stuart, the gray whale comes from what is known as an “unusual mortality event” in the past four years, most likely due to prey loss in the Arctic. The most recent estimates estimate there are about 14,000 gray whales alive, up from 27,000 in 2019, he said.

Dr. Stuart said the mass extinction appears to be waning. During mass mortality events, gray whales begin feeding on things they don’t normally eat or appear in places where they are not normally seen, such as the Atlantic Ocean.

“There is a possibility that some of these unusual observations in the Atlantic Ocean could be a result of that,” he said. The gray whales in the Pacific and Arctic “just don’t get what they need to survive, so they look elsewhere for food, so we see them in all kinds of strange places.”

But the sporadic sightings of gray whales outside their usual habitat could be a sign of things to come, he said.

“What’s really cool is that we can track the recolonization of the Atlantic gray whale in real time,” said Dr. Stuart.

He said he did not expect a full recolonization of the Atlantic gray whale to occur anytime soon, noting that the process could take decades, even centuries. But because of the rapid warming of the water, Dr. Stuart, “we may be witnessing the very beginning of that.”

Still, Ms O’Brien said it was too early to say whether something like this would happen.

“The timeline goes beyond what we could observe,” she said. “It would take a very long time for that many whales to come and stay here.”