A $7 billion seafood species has become an invasive resident on the US East Coast - here's why scientists are concerned

An invasive clam species that supports a multibillion-dollar seafood industry worldwide has reached a major milestone in North America. Researchers have found that Manila clams (Ruditapes philippinarum) are now breeding successfully in Boston Harbor, making Massachusetts the first known site where the species has established a self-sustaining population along the northwestern Atlantic coast.

The discovery marks an uncommon turning point in invasion biology, when a non-native species transitions from occasional sightings to becoming a permanent resident capable of reproducing on its own.

The findings were published on July 4 in the journal Biological Invasions by biologists from the University of Massachusetts Amherst, the MIT Sea Grant Program and the Center for Coastal Studies.

How researchers discovered the breeding population

The northwestern Atlantic coast had remained the only Manila clam-free stretch of the Northern Hemisphere coastline until now. Native to waters around Sakhalin Island in Russia, Japan and southern China, the species has spread widely across other parts of the world and today supports a seafood industry worth an estimated $7 billion annually.

According to Phys.org, the first clue emerged during the summer of 2025, when an undergraduate attending a workshop on Spectacle Island in Boston Harbor sent researchers a message suggesting that a clam they had found might be a Manila clam.

That observation prompted further surveys. Researchers soon discovered tiny live Manila clams at Squantum in Quincy and Calf Pasture Park in Boston, while large numbers of shells were also found in the surrounding area.

Why researchers are concerned

Scientists say the discovery is important because invasive species become much harder to manage once they establish breeding populations.

Shellfish beds play a vital role in coastal ecosystems while also supporting fisheries, local economies, recreation, and habitat restoration efforts. A new invasive species capable of reproducing naturally could alter those systems over time.

Although Manila clams are highly valued as seafood, Phys.org reported that they may compete with native shellfish for habitat and resources and can also interbreed with related species. If their numbers continue to grow, researchers say they could place additional pressure on native species and habitats that conservation efforts are already trying to protect.

The researchers also identified one possible ecological benefit. Manila clams could become an additional food source for predators, potentially reducing some of the pressure that invasive green crabs place on native softshell clams. However, they caution that this possibility does not remove the broader ecological risks associated with a newly established invasive species.