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Coosawattee Crayfish. Photo by Chris Lukhaup. Image may be subject to copyright.
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Cambarus coosawattae Hobbs, 1981

Coosawattee Crayfish

Federal Protection: No US federal protection

State Protection: Threatened

Global Rank: G2

State Rank: S2

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 28

Habitat Summary for element in Georgia: Riffle habitats in the Coosawattee River system


Description

The base color of the Coosawattee Crayfish is brownish to olive with a reddish or burgundy coloration on the posterior portion of the carapace and the posterior edge of each abdominal segment. Margins of the rostrum and postorbital ridges are orange to reddish. The claws can be quite large in relation to the body and there is a gap between the fingers of the claw when the claw is closed. There is usually a tuft of setae at the base of the fixed finger of the claw and a single row of flattened tubercles along the mesial margin of the palm. The rostrum tapers anteriorly and appears “pinched” near the middle. The areola is broad with sides that are nearly parallel. Cervical spines are absent. This species reaches a maximum total body length of about 75 mm (3 inches).

Similar Species

The only species that occurs with Coosawattee Crayfish which has a claw with a gap when the fingers are closes is the similar appearing Beautiful Crayfish (Cambarus speciosus). The Coosawattee Crayfish differs from Beautiful Crayfish by the lack of cervical spines and a rostrum that appears pinched in the middle compared to the nearly parallel-sided rostrum of the Beautiful Crayfish.

Habitat

Adults are typically found under rocks in relatively fast currents within streams. Juveniles may be found in leaves or woody debris in slower moving water.

Diet

No studies of the Coosawattee Crayfish are known. Crayfishes are considered opportunistic omnivores and are likely to feed on live and decaying vegetation, aquatic insect larvae, small fishes, and dead animal matter.

Life History

Stream dwelling crayfishes typically hide during the day and come out at night to feed. Reproduction usually occurs during the spring and fall, but males in reproductive condition may be found at any time during the year. When female crayfish are ready to lay eggs, they usually find a secure hiding place and hence are rarely encountered. When the eggs are released, the female attaches them to her swimmerets and is said to be “in berry.” Upon hatching, the juvenile crayfish are attached to the mother by a thread. After the juveniles molt for the second time, they are free of the mother, but stay close and will hold on to her for some time. Eventually they move off on their own. Crayfishes molt 6 or 7 times during their first year of life and most are probably able to reproduce by the end of that year. They molt once or twice a year for the remainder of their lives and live about 3 years. Male Coosawattee Crayfish in reproductive condition have been collected in April, June, September, and October and females carrying eggs were found in April and June. The number of eggs for 8 individuals ranged from 27–101 with egg diameters of 2.4–2.6 mm (about 1/8th inch).

Survey Recommendations

Since this species is usually found in swift water, it is most easily collected by holding a net perpendicular to the current downstream of a large rock, then lifting the rock and disturbing the substrate beneath it. If a crayfish is hiding underneath the rock, it will likely move into the net. Shocking downstream into a seine net with a backpack electroshocker is also effective, as is setting baited minnow traps overnight. Collections in spring or fall are more likely to produce males in reproductive condition, which can be helpful with identifications.

Range

The Coosawattee Crayfish is known only from the Coosawattee River system in Gilmer and Pickens counties, GA. The species was previously known only from streams and rivers upstream of Carter’s Lake (Gilmer County) but has now been collected from three locations in the headwaters of the Talking Rock system (Pickens County); both areas are within the Blue Ridge physiographic province (Hobbs 1981, Skelton 2016).

Threats

The small range of this species and the high development rates within that range are significant threats to the Coosawattee Crayfish. With more development comes an increase in impervious surfaces. This can lead to more frequent and severe stormwater flows that carry toxins and increase water temperatures; these threats are harmful to all aquatic life. Heavy sedimentation resulting from poor development and land management practices may cover substrates and other daytime hiding places on which crayfishes rely to avoid predation. The introduction of non-native crayfishes is a threat to all native crayfishes. Since this species is adapted to flowing water habitats, reservoir development in the Coosawattee River drainage would eliminate populations upstream of any new dams.

Georgia Conservation Status

Populations at collection locations were apparently secure during status surveys conducted in 2001 and 2013.

Conservation Management Recommendations

Conserving populations of the Coosawattee Crayfish will require general watershed level protection measures, including the protection of riparian zones, control of sediment and nutrient runoff from farms and construction sites, and limiting the amount of impervious cover (e.g., pavement) within occupied watersheds. Non-native crayfishes should never be used for bait. Instead, anglers should use crayfishes collected from the river system they will be fishing in and should never release unused bait crayfish back into Georgia waters.

References

Hobbs, H.H., Jr. 1981. The crayfishes of Georgia. Smithsonian Contributions to Zoology 318:1–549.

Hobbs, H.H., Jr. 1989. An illustrated checklist of the American crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Contributions to Zoology 480:1–236

Schuster, G.A. 2001. A study of the current status of two species of crayfishes, Cambarus coosawattae and Cambarus speciosus, both endemic to the Coosawattee River system in northern Georgia. Final Report, Georgia Forest Watch, Ellijay, Georgia. 9 pp.

Skelton, C.E. 2016 Status Assessment for 14 Crayfish Petitioned for Listing. Final Report. United State Fish and Wildlife Service, Athens, GA. 71 pp.

Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs III, H.W. Robison, C.E. Skelton, and R.F. Thoma. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32:372–389.

Authors of Account

Christopher E. Skelton

Date Compiled or Updated

C. Skelton, June 2008: original account

C. Skelton, December 2018: general update of account.