Catspaw

Epioblasma obliquata obliquata

Description

The catspaw, also known as the purple cat's paw pearlymussel, has a medium-sized shell that is subquadrate (roughly rectangular) in outline. The outside surface has numerous distinct growth lines, fine wavy green rays, a smooth and shiny surface, and is yellowish-green, yellow, or brownish in color. The inside of the shell is a lustrous purplish to deep purple.

Behavior

The specific food habits of the catspaw are unknown. Like other freshwater mussels, however, it probably filter-feeds on detritus, diatoms, phytoplankton, and zooplankton. As with other unionid bivalves, the larvae (or veligers) have a planktonic stage during which they are parasitic on species of fish. Afterwards, they settle to the bottom and adopt the sedentary, filter-feeding lifestyle of the adults.

Habitat

The catspaw inhabits large rivers with a sand/gravel substrate. It occurs in water of shallow to moderate depth, with a moderate to swift current. It inhabits boulder to sand substrates.

Distribution

The catspaw was once known from the Ohio, Cumberland, and Tennessee River Systems in Ohio, Illinois, Indiana, Kentucky, Tennessee, and Alabama.

Threats

The range and abundance of the catspaw are greatly reduced from former times. Most of its historical populations were lost through the conversion of extensive sections of its riverine habitat into a series of large impoundments (i.e., through the construction of dams). This greatly reduced the availability of riverine habitat, and also affected the distribution and availability of the fish hosts of the parasitic mussel larvae. The degradation of water quality is also a problem, including runoff from oil and gas exploration and production, the dredging of gravel, channel maintenance, and commercial fishing for other species of mussels. The rare catspaw is also threatened by the invasion of its habitat by an introduced alien species, the zebra mussel (Dreissena polymorpha ), which out-competes many native species of unionid bivalves. Only three populations of the catspaw survive. These are located in the middle Cumberland River in Smith County, Tennessee, and in the Green River in Warren and Butler Counties, Kentucky. However, two of these populations only have old animals, and appear to be non-reproducing.

Conservation and Recovery

Surveys are needed to determine whether any additional populations of the catspaw survive, and to monitor the known populations. The known populations must be protected from obvious threats, such as gravel mining. Unless additional reproducing populations can be found, or methods developed to maintain the three known populations or create new ones, the species will remain at great risk of extinction. Research is needed to better understand the life-history requirements of the rare catspaw, and to determine the threats to its existence so they can be alleviated.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1 Federal Drive
BHW Federal Building
Fort Snelling, Minnesota 55111
Telephone: (612) 713-5360
http://midwest.fws.gov/

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

U. S. Fish and Wildlife Service
330 Ridgefield Court Telephone:
Asheville, North Carolina 28806
(704) 665-1195

References

U. S. Fish and Wildlife Service. 2000. Cat's Paw Pearlymussel (Epioblasma [= Dysnomia] obliquata obliquata ).http://endangered.fws.gov/i/f/saf15.html

U.S. Fish and Wildlife Service. 10 July 1990. "Endangered and Threatened Wildlife and Plants: Purple Cat's Paw Pearlymussel Determined To Be An Endangered Species." Federal Register 55:132.