Imperiled Freshwater Mussels Found in Urban Delaware River

Imperiled Freshwater Mussels Found in Urban Delaware River

PHILADELPHIA, Pennsylvania, November 16, 2010 (ENS) – Beds of native freshwater mussels were discovered this summer in an urban stretch of the Delaware River near Philadelphia, scientists announced today. Two of the seven species found were thought to have vanished from both Pennsylvania and New Jersey.

Scientists with the Partnership for the Delaware Estuary and The Academy of Natural Sciences found the mussels in the river between Chester, Pennsylvania and Trenton, New Jersey.

“Until this discovery, our surveys for freshwater mussels in southeastern Pennsylvania during the past 10 years have painted a grim picture. Only one species seems to still be prevalent in the area’s streams, and even that species is found in only a handful of locations anymore,” said Roger Thomas, staff scientist at The Academy of Natural Sciences’ Patrick Center for Environmental Research in Philadelphia.

The alewife floater mussel was thought extinct in Pennsylvania and New Jersey. (Photo courtesy North Carolina Wildlife Resources Commission)

“These recently-discovered beds of mussels can be used to help support mussel reintroduction into other areas where they have been lost,” he said.

Freshwater mussels can live to be 100 years old, yet they are among the most imperiled of all plants and animals in North America. Nearly three-quarters of the continent’s 300 freshwater mussel species are in decline, and many have either disappeared or are headed toward extinction.

In the Delaware River Basin, most of the 12 native mussel species are classified as reduced, threatened, or locally extinct. One of these species is considered endangered at the federal level and others are listed as endangered at the state level.

“Freshwater mussels are very sensitive to a variety of problems, including pollution, dams, water flows, loss of forests, and harvesting for their shells and as bait,” said Dr. Danielle Kreeger, science director at the Partnership for the Delaware Estuary.

“We have so few mussels left in almost all of our streams in the area, so to find seven species living together in dense communities right near Philadelphia was unexpected and cause for celebration,” said Kreeger.

One reason freshwater mussels may be doing better in the Delaware River compared to surrounding tributaries is the fact that the Delaware is the longest free-flowing river east of the Mississippi, the scientists speculated.

Mussels rely on fish to carry their larvae to new areas where they can grow, but where dams block fish, the cycle is interrupted. Pennsylvania has more dams than any other state, many located in Delaware Valley streams. The only exception is the Delaware River.

Of the seven species of native freshwater mussels discovered this past summer:

• Two species were thought to be extinct in Pennsylvania and New Jersey: the alewife floater, Anodonta implicata, and the tidewater mucket, Leptodea ochracea.
• Two species are considered critically-imperiled: the pond mussel, Ligumia nasuta, and yellow lampmussel, Lampsilis cariosa
• Two species are considered vulnerable: the creeper, Strophitus undulates, and the eastern floater, Pyganodon cataracta
• One species is listed as common: the eastern elliptio, Elliptio complanata

Dr. Kreeger is part of a group working to expand the fledgling Freshwater Mussel Recovery Program with support from funders including ConocoPhillips, the National Fish and Wildlife Foundation, and the Pennsylvania Coastal Resources Management Program.

The program aims to increase mussel populations throughout the Delaware River Basin by breeding them in a hatchery or relocating adults to targeted streams during breeding season.

Since 2007, Kreeger, Thomas and colleagues have been experimenting on various methods with Cheyney University, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey.

“Dense beds of mussels filter pollutants and make conditions better for fish and other aquatic life, improving water quality downstream in the estuary,” said Jennifer Adkins, executive director of the Partnership for the Delaware Estuary.

“We may have these beds of mussels to thank for keeping certain types of pollution, like nutrients, low in this part of the river,” she said. “This helps make our waters more inviting for everyone.”

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