Nashville Crayfish

Orconectes shoupi

Description

The Nashville crayfish, Orconectes shoupi, is a decapod crustacean that grows as large as 6 in (15 cm). Crayfish have four pairs of walking legs and two large claws in front, which are used to capture prey. The pinchers are elongated and the tips have a distinctive orange and black coloration. The hard shell terminates in a sharp point between the eyes. The general body coloration varies from green to dark brown. However, most specimens have displayed an area of lighter coloration on the mid-back region extending down along the sides toward the head.

Behavior

Very little is known about the biology of this species. It is an efficient bottom scavenger and feeds on plant and animal detritus, small invertebrates, and fish eggs. Males probably begin molting into the reproductive state in late summer with copulation in late summer or fall. Egg laying likely occurs in late winter and early spring. Most males molt back into the nonreproductive form during April. Parental care may occur as females with eggs and young have been observed in the spring.

Sex ratio and size of males and females appear to be about equal. Individuals appear to establish territories whose size is dependent upon the size of the individual and availability and size of cover, and the degree of crowding pressures exerted by such conditions as drought, lack of available habitat, and density. Densities have been reported from 0.6-11.9 individuals per square yard or square meter.

Habitat

The Nashville crayfish has been found in a wide range of aquatic habitats in Tennessee, including swift-flowing cobble runs and deep, still pools with mud bottoms. It often hides along the stream banks under limestone slabs. Crayfish require very high-quality water and have a low tolerance for pollution and siltation.

Distribution

The Nashville crayfish has been collected from four Tennessee localities—Mill Creek watershed (Davidson and Williamson counties), Big Creek in the Elk River system (Giles County), South Harpeth River (Davidson County), and Richland Creek, a Cumberland River tributary (Davidson County). Surveys conducted in 1985 suggest that the Nashville crayfish has been eliminated from all but the Mill Creek watershed.

The Nashville crayfish is currently found only in the Mill Creek basin in Davidson and Williamson counties, Tennessee. There are no current population estimates.

Threats

The Nashville crayfish has been eliminated from much of its former range by residential and urban development, which has contributed to a steep decline in water quality. Contaminants carried by rainwater runoff, silt from land clearing and residential construction, and diversion of groundwater have degraded many former portions of the cray-fish's habitat. The lower Mill Creek basin lies within the Nashville metropolitan area, and it is estimated that more than 40% of the watershed has already been developed. Construction of a proposed waste-water management facility and a reservoir would seriously jeopardize the survival of this species. The upper Mill Creek basin has been degraded by silt and chemicals from agricultural runoff.

Crayfish are frequently used for bait by sports fishermen, and this rare species is often taken along with the more common crayfish. To counter this threat, personnel from the Tennessee Department of Conservation, Tennessee Wildlife Resources Agency, Army Corps of Engineers, and U. S. Fish and Wildlife Service (FWS) collaborated to develop a public awareness program to enable sports fishermen to identify the Nashville crayfish.

Conservation and Recovery

The FWS Nashville Crayfish Recovery Plan recommends that a second self-sustaining population be established outside of the immediate Mill Creek basin to guard against any accidental catastrophic event, such as a toxic chemical spill. If the Mill Creek population stabilizes and a second population proves stable for at least 10 years, the FWS would consider reclassifying this species as Threatened. Because of its low numbers and limited range, it is doubtful whether the Nashville crayfish could ever be completely removed from the protection of the Endangered Species Act.

Contact

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

References

Bouchard, R. W. 1984. "Distribution and Status of the Endangered Crayfish Orconectes shoupi (Decapoda: Cambaridae)." Tennessee Technical University, Cookeville.

Hobbs, H. H., Jr. 1948. "On the Crayfishes of the Limosus Section of the Genus Orconectes (Decapoda, Astycidae)." Journal of the Washington Academy of Science 38(1):14-21.

O'Bara, C. J. 1985. "Status Survey of the Nashville Crayfish (Orconectes shoupi )." Report. U.S. Fish and Wildlife Service, Asheville, North Carolina.

U.S. Fish and Wildlife Service. 1987. "The Nashville Crayfish Recovery Plan." U.S. Fish and Wildlife Service, Atlanta.