Aly Putnam and Carolina Bastidas were on Spectacle Island in Boston Harbor last summer when a photo from El Fernekees Hartshorn helped point them toward the Manila clam Atlantic Coast invasion. The New England coastline, including Cape Cod and Boston Harbor, is now part of the species’ range.
Researchers writing in Biological Invasions said the region had been the Northern Hemisphere’s last holdout against the Manila clam, known as Ruditapes philippinarum. Putnam said, "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".
Biological Invasions and the first tip
The first clue came last summer, when Hartshorn sent Putnam a photo of a suspected shell. After that tip, the researchers found many more Manila clams. A separate Center for Coastal Studies team had also started investigating reports of weird clams near Provincetown, Massachusetts, and the two teams then worked together.
Carlton said, "I realized that this was a golden opportunity to not only combine forces, but also to catch a detailed snapshot of the moment a new invasive species establishes itself". That collaboration turned scattered sightings into a clearer picture of how the clams are taking hold along New England.
Cape Cod and Boston Harbor
The species is native to Russia’s Sakhalin Islands and the coasts of Japan and southern China, and it was introduced intentionally and accidentally to North America and Europe during the early 20th century. It has spread across coastlines in North America and Europe for at least the last century, and the food industry turned it into a $7 billion-a-year industry.
Putnam and Bastidas were leading a biodiversity workshop on Spectacle Island in Boston Harbor when they began paying attention to the coastlines. The first discovery did not come from a single sweep or a formal survey alone; it started with a photo, then expanded as the researchers kept looking.
New England shellfish habitats
The clams can take over habitats of local shellfish and can hybridize with similar species. Dense colonies can adversely impact local ecologies, including habitats that support softshell clams. Bastidas said, "On the positive side, because Manila clams can become a source of food for other animals, they can relieve pressure on native species—-for example, the predator pressure of green crabs on softshell clams".
The practical next step for New England is observation, not alarm. Ecologists now have a real chance to track how quickly the species spreads through the coastline and how far the new colonies reach beyond Cape Cod and Boston Harbor.
