Appalachian Elktoe

Alasmidonta raveneliana

Description

The Alasmidonta raveneliana (Appalachian elktoe) has a thin, but not fragile, kidney-shaped shell, reaching up to about 3.2 in (8 cm) in length, 1.4 in (3.5 cm) in height, and 1 in (2.5 cm) in width. Juveniles generally have a yellowish-brown periostracum (outer shell surface) while the periostracum of the adults is usually dark brown to greenish-black in color. Although rays are prominent on some shells, particularly in the posterior portion of the shell, many individuals have only obscure greenish rays. The shell nacre (inside shell surface) is shiny, often white to bluish-white, changing to a salmon, pinkish, or brownish color in the central and beak cavity portions of the shell; some specimens may be marked with irregular brownish blotches.

Behavior

The Appalachian elktoe is a filter-feeder of algae, tiny zooplankton, and organic detritus, which are siphoned from overlying water. The male releases sperm into the water. These are siphoned by the female, and used to fertilize eggs in the gill chamber. The mature larvae are planktonic and parasitic on species of fish. The larvae metamorphose into the sedentary, adult stage of the life-history.

Habitat

The Appalachian elktoe has been reported from relatively shallow, medium-sized creeks and rivers with cool, well-oxygenated, moderate to fast-flowing water. It has been observed in gravelly substrates often mixed with cobble and boulders, in cracks in bedrock, and occasionally in relatively silt-free, coarse, sandy substrates.

Distribution

Only two populations of the species are known to survive. The healthiest of these populations exists in the main stem of the Little Tennessee River between Emory Lake at Franklin, Macon County,North Carolina, and Fontana Reservoir in Swain County, North Carolina. The second population occurs in the Nolichucky River system. This population appears to be restricted to scattered locations within a short reach of the Toe River and the main stem of the Nolichucky River in Yancey and Mitchell Counties, North Carolina, extending down river into the vicinity of Erwin, Unicoi County, Tennessee. A single specimen of the Appalachian elktoe has also been found in the Cane River, a major tributary to the Nolichucky River, in Yancey County, North Carolina. The complete historic range of the Appalachian elktoe is unknown, but available information suggests it was once widely distributed throughout Upper Tennessee River system in western North Carolina, including the French Broad River, Little River (French Broad River system), Pigeon River (French Broad River system), Swan-nanoa River (French Broad River system), and Talula Creek (Little Tennessee River system). In Tennessee, the species is known only from its present range in the main stem of the Nolichucky River.

Threats

Water quality and habitat degradation resulting from impoundments, stream channelization projects, and point and non-point sources of siltation and other pollutants appear to be major factors in reducing the species' distribution and reproductive capacity.

The most immediate threats to both remaining populations of the species currently appear to be associated with sedimentation and other pollutants (fertilizers, pesticides, heavy metals, oil, salts, organic wastes) from non-point sources. Much of the Nolichucky River in North Carolina contains heavy loads of sediments from past land disturbance activities within its watershed, and suitable habitat for the Appalachian elktoe appears to be limited in this river system. Also, the Little Tennessee River above Lake Emory (above the reach of the river supporting the Appalachian elktoe) carries a high load of unstable sediments and is without mussels. It is believed that Lake Emory has served in the past, and continues serve to a lesser degree, as a sediment trap that has helped to protect the integrity of the river below the Town of Franklin. However, the lake is rapidly filling in with sediment and large sediment accumulations in the river below the lake are become increasing common.

Conservation and Recovery

Assuring the long-term survival of the Appalachian elktoe will require, at a minimum (1) protecting the existing water and habitat quality of the reaches of the Little Tennessee and Nolichucky River systems where the species is still surviving; and, (2) improving degraded portions of the species habitat and, reestablishing and protecting additional populations of the species within portions of its historic range. This will require compliance with existing State and Federal regulations and assistance from the public and local governments and industries in implementing recovery actions. Also, additional research on the threats to the species, the environmental requirements of the elktoe and fish host(s), and propagation and reintroduction techniques for freshwater mussels is needed.

Contacts

U.S. Fish and Wildlife Service
Asheville Ecological Services Field Office
160 Zillicoa Street
Asheville, North Carolina, 28801-1082
Telephone: (828) 258-3939
Fax: (828) 258-5330

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

Reference

U.S. Fish and Wildlife Service. 23 November 1994. "Appalachian Elktoe Determined to be an Endangered Species." Federal Register 59(225): 60324-60334.