Published in Erie National Wildlife Refuge’s newsletter, InsidErie, December 2009
The female Northern Riffleshell Mussel, an endangered species found on Erie National Wildlife Refuge, is a master of catch-and-release fishing. Periodically, these mussels emerge from their hiding places within rocky or sandy creek beds and open their shells, revealing a white mantle and a frilly lure.
When a fish approaches, they snap their shells around the fish’s head and implant their larvae – called glochidia. Slowly, they release the fish. The glochidia grow on the fish’s gills for about two weeks until they drop into the creek bed to begin their lives as young mussels.
Less is known about the reproductive tactics of the clubshell mussel, the refuge’s other known endangered species, although they also rely on host fish for their glochidia.
Mussels benefit their fish hosts as well. They filter rivers and streams by consuming nutrients from the water. This helps sunlight penetrate the water and algae to grow along the riverbed, providing food for fish. The many glochidia that fail to latch onto a host fish are another food source.
“We probably don’t know all the ecological services that mussels provide,” says Robert Anderson, a biologist with the U.S. Fish and Wildlife Field Office in State College, Pennsylvania. “The role they play is being revealed as we study them.”
Freshwater mussels were once common in rivers and streams throughout the Midwest and eastern United States. Now, 35 native species are believed to be extinct and others, like the Northern riffleshell and clubshell mussels, are found in just 5 percent of their former range.
River and stream re-channeling and dams, and water pollution have decimated entire populations of freshwater mussels. Heavy sediment in the water can suffocate them, and mussels rely on clean, moving water to bring them food and oxygen. Runoff from wastewater treatment plants or mining, sediment from land development, and fertilizer and pesticides can kill them.
The French Creek and Allegheny River boast the healthiest remaining populations of both species — a tribute to their water quality and ecosystems. Anderson attributes the mussel’s continued success here to relatively light development, extensive swaths of adjacent conservation lands like the Allegheny National Forest, and the large amount of pure groundwater that flows into French Creek.
The clubshell and Northern riffleshell mussels are both listed as endangered under the Endangered Species Act (ESA). This act, created in 1973, was passed out of concern that many of our nation’s native plants and animals were in danger of becoming extinct. Under the ESA it is unlawful to harm, harass or kill species listed as “endangered” or “threatened.” The U.S. Fish and Wildlife Service and the National Fisheries Marine Service administer the law, and determine —using scientific studies and peer review—which species should be listed.
The ESA defines “endangered” species as in imminent danger of becoming extinct throughout all or most of their range. “Threatened” species are in imminent danger of becoming endangered. Scientists develop recovery plans for many of the listed species aimed at protecting and reestablishing them until they no longer need protection under the law.
Erie’s endangered mussels are in Muddy Creek, a French Creek tributary on the Seneca Division. Their presence has made revegetating stream banks and restoring the area’s natural hydrology— waterflow patterns — a high priority. “We would also like to study the refuge’s mussels more to determine if there are viable, reproducing populations,” says Deputy Refuge Manager Patty Nagel.
The mussels’ endangered status makes them a focus for conservation on the refuge along with other trust species like migratory birds, Refuge Manager Tom Roster notes. “Our first and foremost consideration should be those species. If we have habitat we can restore that will potentially benefit the species, then we should do that.”
While few of us will have a chance to see the Northern riffleshell’s fishing tactics or even to spot a clubshell mussel in a creek, their presence is important, Roster adds. “These mussels are part of the diversity of the area and show its high quality. Once you start losing endangered species from the ecosystem, then the whole ecosystem starts to break down.”