Anthony's Riversnail

Athearnia anthonyi

Description

This relatively large freshwater snail, which grows to about 1 in (2.5 cm) in length, is ovate and olive green to yellowish brown in color.

Behavior

This species eats diatoms and plant debris, which it grazes along mud surfaces, rocky surfaces and macrophytes. Anthony's riversnail has an annual life cycle.

Habitat

Anthony's riversnail is a big-river species that was historically associated with the shoal areas in the main stem of the Tennessee River and the lower reaches of some of its tributaries. Presently, only two small populations are known to survive-one in the Sequatchie River, Marion County, Tennessee; and one in Limestone Creek, Limestone County, Alabama.

Distribution

Anthony's riversnail is a big-river species that was historically associated with the shoal areas in the main stem of the Tennessee River and the lower reaches of some of its tributaries. There are historical records of the species from the following rivers in Tennessee: lower French Broad, Nolichucky, Clinch, Beaver Creek, Little Tennessee, Tellico, Sequatchie, Little Sequatchie, Battle Creek; in Georgia from South Chickamauga and Tiger Creeks; and in Alabama from Limestone Creek.

Presently, only two small populations are known to survive-one in the Sequatchie River, Marion County, Tennessee; and one in Limestone Creek, Limestone County, Alabama.

Because this species has an annual life cycle, the number of individuals varies from year to year, and the precise number of individuals is unknown. The Anthony's riversnail has an extremely limited distribution and low numbers.

Threats

Many populations were lost when much of the Tennessee River and the lower reaches of its tributaries were impounded. The general water quality deterioration that has resulted from siltation and other pollutants contributed by coal mining, poor land use practices, and waste discharges was likely responsible for the species' further decline. These factors continue to impact the Sequatchie River and Limestone Creek populations. Further, timber harvesting for wood chip mills proposed for southeastern Tennessee and northeastern Alabama could impact this species.

Both existing populations inhabit short river reaches; thus, they are very vulnerable to extirpation from accidental toxic chemical spills. As the Sequatchie River and Limestone Creek are isolated by impoundments from other Tennessee tributaries, recolonization of any extirpated populations would be unlikely without human intervention. Additionally, because these populations are isolated, their long-term genetic viability is questionable.

Because this species is very rare, with populations restricted to extremely short stream reaches, unregulated taking for any purpose could threaten its continued existence. Therefore, the U.S. Fish and Wildlife Service decided not to designate critical habitat since the publication of precise population locations would increase the collection threat. FWS also determined that there was little advantage to the snail to designate critical habitat.

FWS notified Federal agencies that could have a program affecting this species. No specific proposed Federal actions were identified that would likely affect the species. Federal activities that could occur and impact the species include, but are not limited to, the carrying out or the issuance of permits for reservoir construction, stream alteration, waste-water facility development, pesticide registration, and road and bridge construction.

Conservation and Recovery

The Anthony's riversnail only survives in two small, isolated populations. Its critical habitat is in short reaches of the Sequatchie River, Tennessee, and in Limestone Creek, Alabama. This habitat is in watercourses running through privately owned land. Its conservation requires the protection of its critical habitats from potential impoundment, and from pollution associated with coal mining and land-use practices in the watershed that cause erosion and inputs of nutrients and other chemicals. The populations of the Anthony's riversnail must be monitored, and research undertaken into its basic biology and ecological requirements. If suitable habitat can be found, additional populations should be established.

Contacts

U.S. Fish and Wildlife Service
Ecological Services Field Office
446 Neal Street
Cookeville, Tennessee 38501-4027
Telephone: (931) 528-6481
Fax: (931) 528-7075

Ecological Services Field Office
P.O. Box 1190
Daphne, Alabama 36526-1190
Telephone: (334) 441-5181
Fax: (334) 441-6222

Reference

U.S. Fish and Wildlife Service. 15 April 1994 "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for the Royal Snail and Anthony's Riversnail." Federal Register 59: 17994-17998.