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Cambarus stockeriCocoa Crayfish
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: GNR
State Rank: S3
SWAP High Priority Species (SGCN): No
Element Occurrences (EOs) in Georgia: 5
Habitat Summary for element in Georgia: Complex burrows adjacent to streams and ditches or in low areas where the water table is near the surface of the ground.
The overall color of the Cocoa Crayfish varies from a pale greenish-brown to brown; occasionally with some mottling on the carapace and paired spots on the anterior portion of the abdomen. The tips of the claws are orangish and the legs and tail fan may have a bluish cast. The claws of this species are fairly diagnostic; the mesial margin of the palm has at least three rows of tubercles and there are additional scattered tubercles on the top and underside of the claw. The areola is very narrow, but not obliterated. The Cocoa Crayfish reaches a maximum total body length of about 90 mm (3.5 in).
Within its range the species can be separated from all others (except Thornytail Crayfish, Cambarus acanthura) by the presence of more than two tubercle rows along the mesial margin of the palm. The Thornytail Crayfish has a spine that extends beyond the margin of the mesial ramus of the uropod; this spine does not extend past the margin on Cocoa Crayfish.
Adults inhabit complex burrows adjacent to streams and ditches or in low areas where the water table is near the surface of the ground.
No studies of the Cocoa Crayfish are known and the diets of burrowing crayfishes in general are poorly understood. Crayfishes are considered opportunistic omnivores and likely feed on a variety of items, both plant and animal, living or dead. Burrowing crayfishes may forage around the mouths of their burrows, eat organisms that crawl or fall into the burrow, or eat worms that inadvertently tunnel through a burrow wall.
Burrowing crayfishes inhabit a system of tunnels that may be very complex with several openings to the surface. Openings to the tunnels are often marked by piles of dirt or mud pellets (chimneys). Depending on the soil type and moisture content, these chimneys can reach heights of 6 inches or more. These crayfishes are typically confined to their burrows, but a male must leave its burrow to search for females during the reproductive season. As mentioned above, they may also forage near the opening of their burrow. Active burrows with fresh soil are seen from late spring to late fall, particularly after rain events. During the dry part of the summer, burrow openings may be plugged to help conserve moisture in the burrow. Reproduction probably occurs during the spring and fall, but males in reproductive condition may be found at any time during the year. It is rare to find more than one adult crayfish in the same burrow. When a female crayfish releases her eggs, she 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. Multiple juveniles are occasionally found in a single burrow. 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. Although it is difficult to study burrowing crayfishes, some researchers believe they may live up to 10 years. Male Cocoa Crayfish in breeding condition have been collected in April and October but no females with eggs have been found (Thoma 2011). The smallest male in breeding condition is about 60 mm (2.6 in). The largest specimen collected is a female about 90 mm (3.5 in) in total length (Thoma 2011).
Burrowing crayfishes may be collected by direct excavation of their burrows, by trapping, and during night surveys. Excavating burrows is time consuming and can be very difficult. It also results in destruction of the animals’ burrow. Traps made with PVC pipes or mist nets can be effective, but only when crayfishes are in an active period. Burrowing crayfishes are sometimes captured around the openings of their burrows on damp nights. It is possible to find active burrows from about mid-March to mid-November if the water table is within about 2 feet of the surface of the ground. However, most activity is seen in the spring from mid-March to mid-May and in the fall from mid-September to mid-November.
The range of this species is poorly understood. In Georgia, the Cocoa Crayfish is known from the northwestern portion of the state in the Conasauga River system. Outside of Georgia, it is found in southeastern Tennessee in the Conasauga and Hiwassee river systems.
The small range of this species, and small size of individual populations, make it vulnerable to land disturbing activities that could destroy burrows and alter groundwater hydrology.
Although the species is known from only a few locations, it is probably not imperiled at this time. There is a population on the Conasauga River Natural Area which is owned and managed by the State of Georgia and therefore somewhat protected.
Areas with burrows should be protected from land disturbing activities and activities that could alter groundwater resources. Additional surveys and life history studies are needed to better define the range of the Cocoa Crayfish and help predict its response to environmental change. Environmental education programs should include information about burrowing crayfishes and encourage protection of burrows.
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.
Thoma, R.F. 2011. Cambarus (Tubericambarus) stockeri (Decapoda: Cambaridae) a new species of plesiomorphic Cambarus from Georgia and Tennessee with zoogeographic affinity to Cambarus (Depressicambarus) cymatilis. Proceedings of the Biological Society of Washington 124:318–325.
Christopher E. Skelton
C. Skelton, August 2017: original account
C. Skelton, January 2019: general update of account.