Cumberland Pigtoe

Pleurobema gibberum

Description

The Pleurobema gibberum (Cumberland pigtoe) is a small freshwater mussel, rarely exceeding 2.3 in (6 cm) in length. The heavy triangular shell is yellowish brown on young mussels, turning dark mahogany with age. The shell interior is peach to orange.

Behavior

The Cumberland pigtoe draws in water using its siphon, and filter-feeds on phytoplankton, tiny zoo-plankton, and organic detritus. Like other Unionid mussel, the female siphons male sperm from the water, and the eggs are fertilized and incubated in her gill chamber. The larvae are planktonic and parasitic on fish. They later settle to the sedentary adult lifestyle.

Habitat

Like many other freshwater mussels, the Cumberland pigtoe prefers stream riffle areas of gravel or sand (occasionally mud or cobble). Freshwater mussels feed by filtering food particles from the water.

Distribution

The Cumberland pigtoe is known only from the Caney Fork River system in Tennessee. Historical records indicate that the mussel has been collected from five Caney Fork tributaries, all above the Great Falls Reservoir, which was constructed in the 1910s. Historic mussel collection records are very limited and given the amount of suitable habitat that was flooded by the impoundment, it is very likely that the Cumberland pigtoe was more widely distributed.

At present there are four known populations of the Cumberland pigtoe on Caney Fork tributaries: Barren Fork (Warren County), Calfkiller River (White County), Cane Creek (Van Buren County), and Collins River (Warren and Grundy counties). A 1990 survery of the river system failed to find Cumberland pigtoe mussels in the main stem of Caney Fork or any other tributaries.

Threats

Decline of the Cumberland pigtoe mussel most likely began with the construction of the Great Falls Reservoir in the 1910s, which flooded a large portion of the mussel's preferred habitat. The species' distribution has declined over the years as a result of water pollution associated with coal mining, poor land use practices, and waster discharge.

Conservation and Recovery

Although no projects with federal involvement that would affect surviving Cumberland pigtoe populations are currently being planned, federal listing of the species ensures that any actions that might affect the species would face close examination. Such actions would include the construction of reservoirs, or hydroelectric and wastewater facilities, channel maintenance or stream alterations. The U. S. Fish and Wildlife Service published a Recovery Plan for the Cumberland pigtoe mussel in 1992. The aim of the Recovery Plan is to establish six viable, self-maintaining populations of the rare mussel so that it can be de-listed. This requires monitoring of its known populations, searching for new ones, and conducting research into its ecological needs and ways of improving its habitat (including reintroduction efforts).

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/

References

Anderson, R. M. 1990. "Status Survey of the Cumberland Pigtoe Pearly Mussel, Pleurobema gibberum." Tennessee Cooperative Fishery Research Unit, Tennessee Technological University, Cookeville, Tennessee.

U.S. Fish and Wildlife Service. 1992. "Cumberland Pigtoe Mussel (Pleurobema gibberum ) Recovery Plan." Atlanta, Georgia.