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Procambarus verrucosusGrainy Crayfish
Federal Protection: No US federal protection
State Protection: Rare
Global Rank: G4
State Rank: S2
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 6
Habitat Summary for element in Georgia: Marshes and standing water(often temporary)adjacent to small, coastal plain creeks.
The dorsal surface of the Grainy Crayfish has an overall olive coloration with darker mottling. The sides are tan and orange. The carapace is often speckled with light colored spots that appear as though they had been etched into the surface. A broad, dorsal stripe down the center of the abdomen may range from brown to black. This stripe is bordered by alternating pairs of light and dark stripes, the last of which may contain the etched spots described above. Claws brown with dark markings on top and lighter brown to orange underneath. The claws appear rather delicate and weak, but male claws are larger and longer than female claws. The areola is moderately narrow. This species reaches a maximum total body length of over 75 mm (3.5 in).
The Sharpnose Crayfish (Procambarus acutissimus) is quite similar in appearance to the Grainy Crayfish. These two species occupy similar habitats and their ranges are contiguous, but not known to be overlapping. Definitive identification may require examination of male and female reproductive structures (see Hobbs 1989 for comparison).
The Grainy Crayfish has been found in a variety of lentic wetlands, ranging from beaver impoundments to marshy areas associated with creeks to roadside ditches. Specimens are commonly collected from aquatic macrophytes or inundated terrestrial plants. Observational data suggest that the distributions of the Grainy Crayfish and the Sharpnose Crayfish may be related to pH. Many of the streams south of Upatoi Creek are characterized by low pH (acidic) and are occupied by the Grainy Crayfish. Those wetlands supporting the Sharpnose Crayfish are more likely to be associated with creeks of near neutral pH.
No studies of the Grainy Crayfish diet are known. Crayfishes are considered opportunistic omnivores and likely feed on live and decaying vegetation, aquatic insect larvae, small fishes, and dead animal matter.
Crayfishes that inhabit open water 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. Egg-carrying females of Grainy Crayfish have not been observed in nature, although they have reproduced in the laboratory. It is inferred that females retreat to burrows after mating and then stay with their young until winter rains. The young are collected first in the spring, followed by adults. It is not unusual for the waters in which they live to dry up in the late summer and fall, which likely triggers burrowing behavior. Hobbs (1952) observed a sperm plug in a female in the early spring. This single observation concurs with laboratory observations made by Stanton.
Because this species occupies slow-moving streams and wetlands, dipnetting, seining, and trapping are recommended sampling methods. Sampling is more effective during late winter and spring when wetland habitats are inundated.
The Grainy Crayfish has been found in Chattahoochee and Stewart counties in Georgia. It is found in the Upatoi Creek catchment, but only within tributaries south of the mainstem. It is found in wetlands associated with Ochillee Creek and other small creeks south of Upatoi Creek in Chattahoochee County. It has also been found along Hannahatchee Creek in Stewart County.
The Grainy Crayfish is threatened in Georgia by its small geographic range. Disturbance or loss of wetland habitats is the most significant threat to the Grainy Crayfish. About half of the Georgia habitat for this species lies on Fort Benning Military Reservation. This habitat has been well protected in the past but could be threatened by increased military training occurring on base.
This species is considered to be stable at this time. In addition, Fort Benning has natural resource management programs in place and has the ability to provide considerable protection to this species.
Conservation of the Grainy Crayfish will require general watershed-level conservation practices, such as protection of riparian zones and adherence to best management practices for forestry, agriculture, and highway construction around stream and wetland habitats. Fort Benning should include this species in future conservation planning efforts. 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.
Bouchard, R.W. 1976. Crayfishes and shrimps. In: H. Boschung, ed., Endangered and Threatened Plants and Animals of Alabama. Bulletin of the Alabama Museum of Natural History 2:13-20. Page 14.
Hobbs, H.H., Jr. 1952. A new crayfish from Alabama, with notes on Procambarus lecontei (Hagen). Proceedings of the U.S. National Museum 102:209–219.
Stanton, G.E. 2003. First record of the crayfish Procambarus (Ortmannicus) verrucosus Hobbs in Georgia. Southeastern Naturalist 2:615–618.
Stanton, G.E. 2006. Evaluation of conservation status of six west Georgia, Chattahoochee-Flint River crayfish species. Columbus State University, report to the Georgia Department of Natural Resources, Georgia Natural Heritage Program. 60 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.
George E. Stanton
G. Stanton, 2008: original account