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.
ANearly 75 percent of historically known river populations of scaleshells have disappeared,@ said Bill Hartwig, the Service=s regional director for the Great Lakes-Big Rivers region. "The species once inhabited 55 rivers or streams in 13 states, but now is limited to14 rivers in Arkansas, Missouri, and Oklahoma."
AThe decline of the scaleshell is an all-too-common trend in freshwater mussels in the United States,@ Hartwig said. AFreshwater 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.
Additional rivers that supported the species historically include Myatt Creek, Cossatot River, Saline River, Little Missouri River in Arkansas and Gates Creek in Oklahoma and the Missouri River below Gavins Point Dam, bordering South Dakota and Nebraska, and in Gasconade County, Missouri. The status of these populations is unknown because of the lack of information on habitat conditions in those streams.
"With the best scientific information we have available to us today, we consider the South Dakota/Nebraska population of the scaleshell mussel to be extinct, but as research continues, the possibility of finding some individuals always exists," said Ralph Morgenweck, Director of the Service
