Empty Manila clam shells pictured in the intertidal zone at Boston Harbor's Spectacle Island. (Courtesy of Aly Putnam via SHNS)

It all started with reports of "weird clams" around Provincetown in 2023.

Then a 2025 text message led to a two-pronged investigation that ultimately confirmed the suspicions of researchers: the invasive Manila clam has established itself along the northwestern Atlantic coastline.

On Tuesday, a team of biologists led by the University of Massachusetts Amherst announced their confirmation, which was part of a report published in Biological Invasions. The coastlines of the Northeast states were the "last place in the northern hemisphere to have remained Manila-clam free," UMass said. The species was based in a range from Russia's Sakhalin Islands through Japan and southern China before being spread both accidentally and intentionally.

Though invasive, the researchers said the presence of the Manila clam is not all bad news. Besides being "a delicious clam" that has grown into a $7 billion industry, the Manila clam could also take some pressure off native species by providing a new food source for seabirds, crabs and other animals that feed on shellfish.

"Given that Manila clams are everywhere else in the northern hemisphere, it was only a matter of time before they showed up here, and we’ve been keeping an eye out for them," Aly Putnam, a marine scientist and postdoctoral researcher at UMass Amherst and lecturer at Smith College, said.

Putnam co-authored the paper on the findings. The discovery was the result of a the convergence of two parallel tracks: one that began in 2023 when a group led by the Center for Coastal Studies heard reports from local clammers of "weird clams" in Provincetown and around the Cape; and another that really kicked off when Putnam got a picture of a clam via text from El Fernekees Hartshorn, a recent University of Rhode Island undergraduate who had worked with Putnam before, suggesting it could be a Manila clam.

Putnam was leading a mini workshop on intertidal biodiversity on Spectacle Island in Boston Harbor at the time and was with Carolina Bastidas, research scientist with MIT Sea Grant. The pair decided they would keep an eye out for Manila clams at Spectacle Island and they found their shells "in abundance." They later dug at other locations and found live clams, as well as evidence of reproduction. An inquiry into the "weird clams" off Provincetown turned up evidence of female Manila clams that had reproduced, too.

Fernekees Hartshorn and Bastidas were co-authors on the paper.

"Finding the species is only the beginning. Now we are working to understand its distribution, if these populations are expanding and how these clams interact with other species in New England coastal systems. This research will help us determine whether this newcomer becomes a minor addition to the ecosystem or a more influential player in the years ahead," Putnam said.

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