A surprising discovery of mussels in the Delaware

If not for the heat of a summer day, one of the major biological finds in the Delaware River in recent years might not have occurred.

It was June, and researchers were scouring the banks and shallows of the river between Trenton and Philadelphia for evidence of freshwater mussels, important water-filtering organisms that are becoming increasingly hard to find in the region's streams.

Danielle Kreeger, science director of the nonprofit Partnership for the Delaware Estuary, had spotted shells along the banks during a wetlands project, and she wanted to see if live mussels were in the river nearby.

So far, no luck.

But Kreeger, who was out on the river in a boat, got hot. Putting on her mask and snorkel, she slipped into the river and swam through the murky water toward the bottom.

Suddenly, she saw them. The riverbed was studded with mussels. They weren't the edible kind, but it was better still - a seven-species mother lode including two species thought to be locally extinct. One, the tidewater mucket, hasn't been seen in this area for more than half a century. The discovery bodes well for the mussels and the river itself.

"I stayed underwater for quite a while, sort of not believing my eyes," she said. Then she got busy. She had a mesh bag, and between gulps of air, she began stuffing it with specimens.

Many species are difficult to differentiate, so they were sent to a U.S. Geological Survey lab, where recently their identities were confirmed.

Kreeger won't be more specific about where the mussels are because she wants to protect them. Conceivably, they could influence development in that part of the river.

Historically, at least a dozen species of freshwater mussels were known in this region. Their folksy common names - alewife floater and squawfoot, for instance - hint at their importance to earlier cultures.

But in a decade of searching, Kreeger has been hard pressed to find more than one species in smaller streams.

In only two Pennsylvania streams south of the Schuylkill - the Brandywine and Ridley Creeks - has she found any at all.

"All of a sudden, it's far more interesting than we could have imagined," said Roger Thomas, an Academy of Natural Sciences fisheries biologist who also was in the boat that day.