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U.S. Fish and Wildlife Service Lists Scaleshell Mussel as Endangered Species


October 9, 2001

Christine Eustis, 404/679-7287

The U.S. Fish and Wildlife Service today announced its decision to list the scaleshell mussel, a freshwater species once found in many rivers in the eastern United States, as endangered under the Endangered Species Act. A plant or animal is designated as endangered if it is in danger of extinction throughout all or a significant portion of its range.

"Nearly 75 percent of historically known river populations of scaleshells have disappeared," said Sam D. Hamilton, the Service's Southeast Regional Director. "The species once inhabited 55 rivers or streams in 13 states, but now is limited to 14 rivers in Arkansas, Missouri, and Oklahoma."

"The decline of the scaleshell is an all-too-common trend in freshwater mussels in the United States," Hamilton said. "Freshwater mussels are valuable members of aquatic ecosystems, and act as excellent indicators of the quality of the water they inhabit -- water we all depend upon. Mussels are one of the most endangered groups of animals in the country, and we need to take extraordinary steps, like this endangered designation, to ensure their survival."

The scaleshell is a relatively small freshwater mussel species measuring 1 to 4 inches in width with a thin, fragile shell and faint green rays. The species inhabits medium-sized and large rivers with stable channels and good water quality.

Scaleshells currently exist in Missouri (Meramec, Big, Bourbeuse, Osage, and Gasconade rivers); Arkansas (St. Francis, Spring, South Fork Spring, South Fourche LaFave, and White rivers, and Frog Bayou ); and Oklahoma (Kiamichi River, Little River, and Mountain Fork). Of these 14 populations, 13 are thought to be declining. Biologists have been able to find no more than 35 individuals in any of these populations and only one individual in most of them.

An additional six rivers supported the species historically (Myatt Creek, Cossatot River, Saline River, and Little Missouri River in Arkansas and Gates Creek in Oklahoma). The status of these populations is unknown because of the lack of information on habitat conditions in those streams.

Threats to the scaleshell, as with many other mussel species, include poor water quality due to pollution and sedimentation, loss and alteration of habitat through damming of waterways, dredging and channelization of rivers, sand and gravel mining, and competition with non-native species like the zebra mussel. In particular, pollutants from industrial sources, sewage, and spills can kill mussels, and sedimentation from dredging and erosion along rivers and streams can cover them and impair respiration and feeding. Mussels are particularly vulnerable because they tend to stay in one place and cannot move away from threats.

The scaleshell's range overlaps those of several other mussel species that have previously been federally listed as endangered or threatened. They include the pink mucket in the Meramec, Big, Gasconade, Spring, Strawberry, and Little Missouri rivers; the fat pocketbook in the St. Francis River; the Curtis pearly mussel in the South Fork Spring River; the Ouachita rock-pocketbook in the Kiamichi River; the Arkansas fatmucket in the Saline River; and the winged mapleleaf in the Little Missouri.

Because the threats to the scaleshell are the same as those for other listed mussels, the steps needed to conserve the scaleshell are similar to measures already in place for other mussels in its range. In general, recovery actions will focus on best management practices and existing technology to control pollutants, erosion, and sedimentation to minimize their impacts on mussels.

The Service's decision was made after a thorough review of the available scientific data on the species and its habitat. This review included a 60-day comment period that was later reopened for an additional 39 days to accommodate a public hearing. The comments from numerous mussel experts were important factors in the Service's final decision to grant endangered species status to the scaleshell.

The scaleshell will now benefit from the protections and recovery actions provided by the Endangered Species Act. Species listed as endangered are protected from direct and indirect take, which includes killing, harming, or harassing. Federal agencies must consult with the Service to ensure that any action they authorize, fund, or carry out does not jeopardize the continued existence of the species. In addition, the Service will assemble a recovery team to identify and implement actions to restore populations so that extinction is no longer a threat.

The Service published the decision to designate the scaleshell as an endangered species in today's Federal Register. The notice can be viewed at the website

The U.S. Fish and Wildlife Service is the principal federal agency responsible for conserving, protecting, and enhancing fish, wildlife, and plants and their habitats for the continuing benefit of the American people. The Service manages the 94-million-acre National Wildlife Refuge System that encompasses more than 535 national wildlife refuges, thousands of small wetlands, and other special management areas. It also operates 70 national fish hatcheries, 64 fishery resource offices, and 78 ecological services field stations. The agency enforces federal wildlife laws, administers the Endangered Species Act, manages migratory bird populations, restores nationally significant fisheries, conserves and restores wildlife habitat such as wetlands, and helps foreign governments with their conservation efforts. It also oversees the Federal Aid program that distributes hundreds of millions of dollars in excise taxes on fishing and hunting equipment to state fish and wildlife agencies.

National News Releases
Scaleshell Mussel (Leptodea leptodon) Fact Sheet
Final Rule to list Scaleshell Mussel as Endangered Species
Status Assessment Summary
Status Assessment (.pdf file 173K)

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Atlanta, GA 30345

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2001 News Releases

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