Weird Clams Invade New England: Manila Clams Establish Along the U.S. Northeast Coast

Manila clams (Ruditapes philippinarum) are one of the most widely farmed and traded seafood species in the world, supporting an industry worth roughly $7 billion annually. Native to the coastal waters from Russia's Sakhalin Islands through Japan and southern China, they have been introduced — both intentionally and accidentally — to the Pacific coast of North America and to Europe over the past century. But one major gap remained: the northeastern Atlantic coast of the United States.

That gap has now closed. A team of biologists led by the University of Massachusetts Amherst, in collaboration with MIT Sea Grant and the Center for Coastal Studies, has confirmed that Manila clams are reproducing in Massachusetts waters. The findings were published in Biological Invasions.

The discovery began with something as ordinary as a text message. During the summer of 2025, marine scientist Aly Putnam was leading a workshop on Spectacle Island in Boston Harbor when a colleague sent her a photograph of an unfamiliar clam shell. The shell turned out to belong to a Manila clam. Further searches revealed large numbers of empty shells blanketing the intertidal zone. Meanwhile, a separate group at the Center for Coastal Studies had been hearing reports from local clammers since 2023 about "weird clams" around Provincetown on Cape Cod.

The team confirmed that the clams are not just surviving but reproducing — they found tiny juveniles, evidence that a breeding population has established itself. Dense populations of Manila clams can compete with native shellfish, hybridize with related species, and alter local ecological communities. At the same time, they provide abundant food for seabirds, crabs, and raccoons.

Knowledge takeaway: Manila clams have established reproducing populations along the Massachusetts coast, filling the last major gap in their Northern Hemisphere range; the detection started with a text message photograph of an unfamiliar shell in Boston Harbor; the species can compete with native shellfish but also provides food for local predators.