Endangered Freshwater Mussels Saved

Saving endangered mussels is vital, Neves says, because mussels are the natural biological filters in the river system. They remove sediment, contaminants, and particles, ingesting some and releasing the rest into mucus strings. Some water insects feed on these strings, and the mussels themselves serve as a food source for raccoons, muskrats, river otters, and diving ducks.

Virginia's freshwater mussels live up to 70 years. They are fertile for their entire life span, after beginning reproduction at about age 4 or 5. But many species are endangered because of water pollution and disturbance or destruction of their natural habitats.

"Mussels are excellent water quality monitors," Neves says. "Because they live so long and move so little, we can take a piece of tissue, analyze for contaminants, and tell what's been going on in the water system for 50 or more years."

He and his colleagues collect gravid females, using a hypodermic syringe to harvest the larvae. They then deposit larvae onto the gills of the type of fish that particular species of mussel prefers. The larvae, which are parasitic, must attach to fish, from which they extract the nutrients required for them to transform from the larval stage to the free-living juvenile stage.

Biologists can deposit mussel larvae from one female onto hundreds of fish, whereas only about a dozen fish can become hosts for the larvae from each gravid female in the wild. The hosts are likely to be small fish that they live on the shoals, which is also the habitat for the mussel.

"In the wild, each gravid female has from 30,000 to 2 million larvae," Neves says. "In the wild, 99 percent of these larvae never attach to a fish and are wasted."

The host fish are kept in holding tanks after they are "infested" with larvae. Carrying the larvae does not appear to negatively affect the hosts, Neves says. The larvae encyst on the gills of fish, where they remain until they are able to survive on their own. The tiny mussels -- smaller than the head of a pin when they drop off the fish -- are siphoned up and placed into tanks where they feed on algae grown in the lab and tailored to meet their nutritional needs.

Neves, who was a pioneer in this work, and graduate students designed an automated feeding system as well as the tanks in which the mussels grow and mature. The tanks are maintained through a recirculating, air-driven system, with the entire system run by a one horsepower motor.

In the tanks, the mussels triple or quadruple in size during the first few weeks. After growing for up to a year, they are returned to the wild to begin their work of improving water quality by filtering sediment and other water impurities.

Water quality in the river reaches to which mussels have been referred has improved considerably in the last 10 years. Federal and state water quality standards have been upgraded, and enforcement of those standards has dramatically reduced chronic water pollution. Elimination of chlorinated wastewater discharges into the Clinch River from sewage treatment plants by the department of Environmental Quality has removed this potentially lethal pollutants to downstream mussel populations in Virginia and Tennessee.

Neves' research is funded in part by grants from the National Fish and Wildlife Foundation, the Tennessee Wildlife Resource Agency, the Virginia Department of Game and Inland Fisheries, and U.S. Fish and Wildlife Service.

He also has received funding from the Virginia Agricultural Experiment Station and an ASPIRES Research Grant from Virginia Tech, which are helping to fund a new facility in which he can expand his mussel propagation work.

Once the work is moved into the new building this spring, Neves hopes to produce about 100,000 juvenile mussels each year. Currently, he has only been able to average about 50,000 per year, depending on the availability of the species with which he is working.

"People are always talking about saving endangered species., but we need to start with what's in our own backyard," Neves says. "The Southeastern United States has the world's highest diversity of aquatic invertebrates, including mussels and snails. We need to concentrate on saving our own world-class fauna."