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Cambarus halli Hobbs, 1968

Slackwater crayfish

Federal Protection: No US federal protection

State Protection: No Georgia state protection

Global Rank: G3G4

State Rank: S2S3

SWAP High Priority Species (SGCN): No

Element Occurrences (EOs) in Georgia: 12

Habitat Summary for element in Georgia: Lotic habitats in debris or among roots along undercut banks


Description

The overall color of the Slackwater Crayfish is grayish blue. The pigment is lighter on the carapace than the abdomen and may include pinkish hues. The edges of the rostrum are orange and the antennae may be pinkish to orangish in color. There is an orangish band at the posterior edge of each abdominal segment and orangish tubercles on the claw where the movable finger connects. The areola is fairly wide and the rostrum is nearly parallel sided and usually exhibits marginal spines or tubercles. There are two rows of tubercles along the mesial margin of the palm and a single cervical spine is usually present. This species reaches a maximum total body length of about 75 mm (3 in).

Similar Species

The Slackwater Crayfish occurs with its close relative, the Tallapoosa Crayfish, Cambarus englishi. In life the two can be separated by the color of the antennae; whitish in the Tallapoosa Crayfish and pinkish or orangish in the Slackwater Crayfish. Additionally, the rostrum of Tallapoosa Crayfish appears to be more tapered and pinched in the middle, whereas the rostrum of the Slackwater Crayfish is more parallel-sided. The Variable Crayfish (Cambarus latimanus) can also be found with the Tallapoosa Crayfish, but it is a drab species with an areola that is narrower and hence more hourglass shaped than that of the Tallapoosa Crayfish.

Habitat

The Slackwater Crayfish is a stream dweller and can occur in most available habitats. It is more commonly found in quieter waters in root mats or associated with undercut banks (Hobbs 1981).

Diet

No studies of the Slackwater Crayfish are known. Crayfishes are considered opportunistic omnivores and likely 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 Slackwater Crayfish in reproductive condition have been collected in Georgia in all months except June-August (Dennard et al. 2009). Seven females carrying eggs were found in April and number of eggs ranged from 94 to 182. Dennard et al. (2009) reported ovigerous females from March through June. The smallest male from Georgia is about 60 mm (2.4 in) and the smallest female with eggs is about 43 mm (1.7 in) in length (Hobbs 1981).

Survey Recommendations

Flipping larger rocks or woody debris in just about any habitat in a stream could turn up this species. The animal can be pinned by hand or gently driven into a dipnet. Dipnetting through leaf packs and undercut banks could yield some specimens as well.

Range

The Slackwater Crayfish is known only from the Tallapoosa River system in Georgia and Alabama (Hobbs 1981).

Threats

This species is apparently secure across its range, although it appears to be somewhat rare in Georgia. Urbanization in the upper Tallapoosa River system is an emerging threat to the Slackwater Crayfish and other rare and endemic aquatic species. 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 Tallapoosa River drainage would eliminate populations upstream of any new dams.

Georgia Conservation Status

Although no populations are known to be protected, this species is considered to be stable.

Conservation Management Recommendations

Conserving populations of the Slackwater 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 where they will be fishing. Unused bait of any kind should not be released back into Georgia waters.

References

Dennard, S., J.T. Peterson, and E.S. Hawthorne. 2009. Life history and ecology of Cambarus halli (Hobbs). Southeastern Naturalist 8:479–494.

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

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, August 2012: original account

C. Skelton, January 2019: general update of account.