FRANKLIN TWP., NJ - Years ago, tiny “hitchhikers” went unnoticed in a tank of live carp shipped from China to a fish farm here.

The hitchhikers were the larvae of Chinese pond mussels (Sinanodonta woodiana). These highly invasive mussels have spread across Europe, but had not been documented in the U.S. until a discovery at the Huey farm on Joe Ent Road here in 2010.

Unseen, the larvae had established themselves in the muddy bottoms of ponds at the fish farm, which supplied carp to Asian restaurants in New York City.

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In 2007, Thomas and Gloria Huey decided to retire, and sold their farm to New Jersey Conservation Foundation for a nature preserve. Land stewards for New Jersey Conservation later discovered that the ponds contained bighead carp, an invasive species that could wreak havoc in natural systems if allowed to escape.

But the discoveries didn’t stop there. Biologists noticed something else in the mud: mature Chinese pond mussels, some as big as dinner plates.

“This was the first population discovered in North America, and as far as we know, the only one,” said Tim Morris, stewardship director for New Jersey Conservation Foundation. “We knew we had to keep them from spreading.”

Chinese pond mussels, he noted, “have taken over some rivers in Eastern Europe, where they outcompete native species. Poland has been very affected by them.”

With America as the top biodiversity hotspot in the world for freshwater mussels, they also threatened populations here. But because of work paid for by the U.S. Fish and Wildlife Service this year, the Chinese pond mussel population in Hunterdon has been eradicated, eliminating the danger of the species spreading to local waterways and, ultimately, the Delaware River.

“Under certain conditions, this invasive species could have spread across the eastern U.S., with New Jersey at the epicenter,” said Eric Schrading, the U.S. Fish and Wildlife Service’s New Jersey field office supervisor in a press release. “Early detection and eradication of the Chinese pond mussel likely saved us a tremendous amount of resources and damage to our rivers and native mussel populations. It’s a significant success in invasive species management.” 

The nine ponds at the former Huey farm were treated with a copper-based algaecide known as Earth Tec QZ, which is approved for killing invasive mussels.

“We searched extensively after the treatments and found shells but no live mussels,” said Melanie Mason, a land steward for New Jersey Conservation Foundation. “We feel pretty confident that they’re gone, but we will follow-up by doing environmental DNA testing of the water to make sure.”

The former fish farm is in the headwaters of the Wickecheoke Creek, a Delaware River tributary. It’s part of NJCF's Wickecheoke Creek Preserve. The Wickecheoke flows through Franklin, Raritan, Kingwood and Delaware townships, and meets the Delaware River at Prallsville Mills in Stockton.