Scuba-diving scientists are tagging and relocating tens of thousands of rare mussels on the Allegheny River to make way for two bridge projects that the bivalve discovery has delayed for years.

	Darby Creek Association, Inc. Clubshell mussels Click photo for larger image.

It's a twist from the usual environmental clash, when a construction project has to be moved or abandoned when an endangered species is found. This time, it is the endangered species that is being moved.

In a five-year survey that covers 80 miles of the river from the Kinzua Dam in Warren County to Tionesta, Forest County, scientists have found the largest population of Northern Riffleshell and Clubshell mussels in North America. The section is where the Pennsylvania Department of Transportation wants to replace two river spans, the West Hickory and Hunter Station bridges. That means moving every mussel from the riverbed by hand upstream.

Each mussel must be tagged first -- a process that involves dabbing each mussel shell with Crazy Glue, then affixing a tiny plastic tag. In one Forest County spot alone, at Hunter Station, about 20,000 Northern Riffleshells and Clubshells were discovered. At West Hickory, where scientists are working now, 5,000 have been found, and survey crews are still counting.

"It's crazy huge," said Glenn Nelson, an ecologist from the U.S. Geological Survey, which is leading the study for PennDOT. "It's like an Easter egg hunt."

What started as an effort to clear the bridge sites for construction has turned into the largest survey of its kind in the country, with federal scientists inventorying mussels at 70 randomly selected sites in the free-flowing wild and scenic stretch of water.

But it isn't a matter of just counting what is there, although scientists are documenting the size, shape and location of each little bivalve, using waterproof pencils to record data underwater. They are also tagging and relocating the mussels.

"A couple of people are joking they'll be retired before this is over," Nelson said.

The endangered mussels are part of a much larger population being studied because 22 species, including some with names like Yellow Pocketbook, Rabbit's Foot, and Snuffbox, dwell in the upper Allegheny.

"We're finding them all sizes from large adults to very small juveniles," said Rita Villella, the U.S. Geological Survey's lead ecologist on the project. "That tells me this portion of the river is very, very healthy."

At West Hickory, all mussels, endangered or not, are being scooped by hand from the substrate of the river, measured, dropped into netted bags, and then carried to shore where trained volunteers dab them with glue and affix tags to them that will enable scientists to monitor their survival years from now. Because divers working at depths of 6 feet can't always distinguish between endangered mussels and others, all of the mussels at West Hickory are being moved and a portion of non-endangered mussels are also getting tagged.

"We've had a lot of stuck-together fingers," said Alison McKechie, a water quality specialist who runs the northeast office of the Pennsylvania Environmental Council, a conservation group, and one of many volunteers on the mussel project. "You've got to be careful not to glue the mussels closed."

College students have been helping, although, as they head back to school, the survey squads get smaller. The change in seasons is also sending mussels deeper, which further compounds the labor intensity of the project.

"We're snorkeling or diving 7 a.m. to 7 p.m.," said Nelson, who digs 6 inches into the substrate with his gloved hands, then records data on an armband with waterproof pencil. He works in 15-by-6-foot cells on a river grid, recording where he finds each bivalve. They range in size from a 1 inch to 8 inches.

At West Hickory, once mussels are processed for data, they are placed in coolers and wash tubs and transported a quarter mile upstream where they are individually tucked into the riverbed.

"Mussels have this little bubble, where it seems they don't want other mussels around them. You've got to give them their space," said Nelson. "The simple fact is, they don't want to compete for food."

"You're also dealing with pea gravel and rocks. What you want is to put each one back into the substrate."

Despite these efforts, about 15 percent of the moved mussels will probably die, based on follow-up studies done at Kennerdell, Venango County, where mussels were moved five years ago for the first bridge replacement in the area.

Northern Riffleshells and Clubshells were added to the endangered list 12 years ago when the U.S. Fish and Wildlife Service determined that they had been reduced to all but 5 percent of their native range by pollution, dredging and other factors. Until the Allegheny River survey, the best North American populations were believed to be on the Tippecanoe River in Indiana, which is part of the same Mississippi Drainage as the Allegheny, and Canada's Sydenham River, north of Toronto.

"Most people think a mussel is a mussel is a mussel," said Nelson. "None of them are warm and fuzzy. They don't have sensory organs, no eyes, ears, mouth. Whether they have a brain is a good question. But without them, you won't have your crayfish, your tadpoles, your other species."

Mussels provide food for raccoon and muskrats, who leave piles of shells along the riverbanks, and they were once part of the diet of Native Americans. But bivalves are prized mostly as indicators of water quality. They consume phytoplankton and other nutrients by filtering water -- as much as one liter an hour, said Villella. "Young mussels in particular are extremely sensitive. In polluted areas, you wind up with an old population that eventually dies out because the young ones aren't able to survive."

Part of what makes the northern Allegheny a mussel stronghold, said Villella, is that it is surrounded by national forestlands and state game lands, although a spike in new home construction on the riverbanks is raising red flags. McKechie said homeowners are removing vegetation needed to keep riverbanks stable, and more pavement and dirt roads are exacerbating runoff, sending silt into the water that could smother mussels. McKechie is encouraging landowners to leave an unmowed buffer zone between their backyards and the river, and to plant native trees, flowers and shrubs.

Ironically, the piers of the bridges that PennDOT plans to replace, including the historic metal truss span at West Hickory, may have played a role in the mussel proliferation, said Nelson. "The piers allow for back eddies. Mussels in general like where water is moving and turning over, because it mixes up what they're going to feed on."

The survey and mussel relocation at West Hickory alone is costing PennDOT about $400,000, Minnich said, and has delayed new bridge construction for years, though he is hoping it will finally begin in 2006.

"We can't build until we have minimized impacts to threatened and endangered species, which can be an extremely complicated process."

Hunter Station construction is several years away, he said, because the mussels haven't even been moved from there yet, and that's where the majority have been found.

There has been some public criticism of the monumental effort to save creatures few folks give much thought to.

"People call them rocks that breathe," said Nelson. "They can't understand why we're going to all this trouble."

"What I say is, we don't know enough about a lot of things we give ourselves credit for being experts in. But if we can minimize the impact of a known problem, if we can give those animals the chance to live their life out, maybe we'll get answers some day."

"Henry David Thoreau said, 'You can't take one thing out of the environment without affecting the rest of nature.'"