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Conservation Assessment and Habitat Notes for Three Rare Alabama Crayfishes: Cambarus cracens, Cambarus scotti, and Cambarus unestami
Stephanie L. Kilburn, Christopher A. Taylor, and Guenter A. Schuster

Southeastern Naturalist, Volume 13, Issue 1 (2014): 108–118

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Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 108 2014 SOUTHEASTERN NATURALIST 13(1):108–118 Conservation Assessment and Habitat Notes for Three Rare Alabama Crayfishes: Cambarus cracens, Cambarus scotti, and Cambarus unestami Stephanie L. Kilburn1, Christopher A. Taylor1,*, and Guenter A. Schuster2 Abstract - Over seventy percent of the world’s freshwater crayfish species are found within the United States, and much of this diversity is concentrated in the southeastern United States. Yet many of these species remain understudied. Of particular interest is the conservation status of these understudied taxa. We conducted fieldwork in 2011 across northeastern Alabama and northwestern Georgia to review the occurrence, habitat, and in some cases, local population densities of three crayfish species (Cambarus scotti, C. unestami, and C. cracens) to determine current distributions in relation to historical surveys. All three species occur in flowing small to medium-sized streams with firm substrates of gravel, cobble, and bedrock. Two species (C. scotti and C. unestami) have stable populations, occurring at 79% and 90% of sites surveyed, respectively. In contrast, surveys for the third crayfish species (C. cracens) indicated a need for conservation action, with this species occurring at a single site. Introduction The southeastern United States is well known for aquatic biodiversity (Abell et al. 2000). This area is known as the hotspot for freshwater fish and mussel species in North America and is the most diverse region in the world for freshwater crayfishes (Neves 1999, Taylor 2002, Warren et al. 2000). Because of this diversity, the region is an area of great conservation concern. A review by Taylor et al. (2007) found that nearly half of the crayfish in the Southeast were in need of some level of conservation attention. This concern is of particular importance for the state of Alabama and its 85 currently described species of crayfish, many of which are limited to a single drainage and remain substantially understudied (Taylor et al. 2007). To address conservation concerns, intensive field surveys for target species are often the best available tool, and this method was used in the following conservation assessments. Cambarus scotti Hobbs (Chattooga River Crayfish), C. unestami Hobbs and Hall (Blackbarred Crayfish), and C. cracens Bouchard and Hobbs (Slenderclaw Crayfish) have limited ranges and are confined to northeastern Alabama and northwestern Georgia. These species are vulnerable to population declines due to localized catastrophic events and are listed as either threatened (C. scotti and C. unestami) or endangered (C. cracens) according to American Fisheries Society criteria (Taylor et al. 2007). Following conservation priority criteria developed by the Alabama Department of Conservation and Natural Resources, C. scotti was classified as P4 (low 1Prairie Research Institute, Illinois Natural History Survey, 1816 South Oak, Champaign, IL 61820. 2305 Boone Way, Richmond, KY 40475. *Corresponding author - cataylor@ illinois.edu. Manuscript Editor: Paul M. Stewart Southeastern Naturalist 109 S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 conservation priority), C. unestami was classified as P2 (high conservation priority), and C. cracens was classified as P1 (highest conservation priority) species (Smith et al. 2011). These three species were the focus of the current study due to the need for distributional data and range-wide status assessments, and/or limited detection rates in past surveys (Smith et al. 2011). The four main objectives were to 1) sample all known historical locations for all three species to determine the presence of each species, 2) find additional populations of these species by sampling other streams with suitable habitat in northeastern Alabama and northwestern Georgia, 3) assess population sizes of the species at locations where appropriate quantitative methods can be employed, and 4) refine the description of suitable habitat for the three species by recording abiotic habitat variables at sites containing the species. Target species accounts Cambarus (Puncticambarus) scotti – The Chattooga River Crayfish is historically known from the Chattooga River basin in Chattooga and Walker counties, GA, and the Coosa River in Calhoun, Cherokee, and St. Clair counties, AL (Hobbs 1989). It occurs in streams with swift water flowing over rocky substrates. Its type locality is Clarks Creek,1.6 km north of Holland, in Chattooga County, GA. First-form males range in size from around 24.5 mm to 41.8 mm carapace length (CL) (Hobbs 1981). This species can closely resemble Cambarus coosae, but differs in possessing a long acuminate rostrum without marginal spines or tubercles (Hobbs 1981, Schuster and Taylor 2004). Taylor et al. (1996, 2007) listed this species as threatened. Cambarus (Jugicambarus) unestami – The Blackbarred Crayfish is known from tributaries of Chattanooga, Cole City, Lookout, and Long Island creeks of the Tennessee River basin of Walker and Dade counties, GA, and Jackson County, AL and from tributaries of the Little River of the Chattooga-Coosa Basin in Chattooga County, GA (Hobbs 1989). Its entire range is found within the Appalachian Plateau. The type locality for C. unestami is Daniel Creek, a tributary of Lookout Creek, 4.02 km west of the Walker County line on State Route 143, Dade County, GA. This species appears to be confined to those streams found on Lookout and Sand mountains between 333 and 500 m in altitude. Preferred streams have moderate to swift current with bedrock or rock-littered substrates for cover (Hobbs 1981). First-form males can range in size from 26.9 mm to 31.3 mm CL (Hobbs 1981, 1989). The species was listed as threatened by Taylor et al. (1996, 2007). Cambarus (Exilicambarus) cracens – Except for its original description by Bouchard and Hobbs (1976), very little is known of the Slenderclaw Crayfish; they reported its range to be limited to five sites in southeastern tributaries of Guntersville Lake (Tennessee River) in DeKalb and Marshall counties, AL. The type locality of the species is Short Creek at State Route 75, 1.77 km southwest of the junction with State Route 68 in Marshall County, AL (Hobbs 1989). Bouchard and Hobbs (1976) described the habitat at the type locality as a clear, slow-flowing stream with bedrock and sandy substrate, and large rocks throughout. First-form males range in size from 24.7 mm to 37.3 mm CL (Hobbs 1981, 1989). Cambarus cracens was listed as endangered by Taylor et al. (1996, 2007). Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 110 Methods During March, June, and October 2011, we conducted field surveys for the three crayfish species in streams of northeastern Alabama and northwestern Georgia. We chose fifty-five sites for either known historical occurrences or as potentially new occurrences based on the presence of suitable habitat. For C. cracens, all sites were repeat visits of localities surveyed in March 2009. We obtained historical siteselection and detailed locality information through museum database queries at the National Museum of Natural History Smithsonian Institution (USNM), Eastern Kentucky University Crustacean Collection (EKU), and Illinois Natural History Survey Crustacean Collection (INHS). We conducted sampling at most sites using a 3-m x 1.5-m kick net (3.2-mm mesh). At sites where a seine was employed, one person held the seine net below groupings of cobble, boulders, or woody debris as one or two others lifted and moved rocks while kicking and shuffling crayfish into the net. We collected all crayfish in that set and kept them in an aerated bucket until the sampling at that site was completed. The number of seine sets employed at sites ranged from 15 to 25 and was in direct relation to the amount of loose gravel or rock and woody debris present at sites. Some small stream sites (less than 2 m width) required only visual searches, which involved turning over cobble and boulders and hand capturing crayfish or handpicking those crayfish exposed. We sampled all microhabitats (riffle, runs, pools) present at sites during surveys, and recorded presence/absence of target species within those micohabitats. We estimated and recorded general in-stream habitat characteristics (riffle, run, pool presence), dominant substrate type, turbidity, general flow condition (slow, medium, fast), and percent of stream shaded by tree cover for each site. We measured depth at five within-site locations and calculated a site-average depth. We measured stream widths with a tape measure at the widest and narrowest parts of sampling locations. We estimated average substrate size by measuring a minimum of five rocks found across a stream transect. After we completed collection efforts, all crayfishes collected at the site were identified in the field, if possible, and recorded. We preserved voucher specimens of each species in 70% ethanol and returned the remaining individuals to the stream. At sites where density estimates were taken (see below), specimens were not returned to the stream until after we had made the estimates. We also vouchered specimens not identifiable in the field and transported them to the laboratory to verify identifications. We then catalogued voucher specimens into the INHS Crustacean Collection. We conducted density estimates at approximately five sampling sites where target species were detected. At each of these sites, we chose a wadeable reach known to contain the target species. We measured the length of that reach and its width at upstream and downstream termini, sampled the reach to depletion for the target species, and calculated the density of individuals/m2. Results The present survey sampled 55 stream sites across northeastern Alabama and northwestern Georgia in 2011(Table 1). Nineteen sites were sampled in March, 15 in June, and 21 in October. Stream sites consisted of both historical localities Southeastern Naturalist 111 S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 Table 1. Alabama and Georgia sampling locations and the number of individuals collected from the 2011 status survey. None = no target species found. Date Drainage State County Location Latitude (°N) Longitude (°W) Species Number 03/22/11 Tenn. River GA Dade Daniel Creek 34.8154 85.4912 C. unestami 5+ 03/22/11 Tenn. River GA Walker Rock Creek 34.9052 85.4019 C. unestami 13 03/22/11 Tenn. River GA Dade Lookout Creek 34.8626 85.5008 C. unestami 0 03/22/11 Tenn. River GA Dade Stephens Branch 34.9101 85.5522 C. unestami 11 03/22/11 Tenn. River AL Jackson Warren Creek 34.9566 85.6289 C. unestami 14 03/22/11 Tenn. River GA Dade Higdon Creek 34.8649 85.5744 C. unestami 1 03/23/11 Tenn. River GA Dade Bear Creek 34.8281 85.4591 C. unestami 24 03/23/11 Coosa River GA Chattooga Gilreath Creek 34.5679 85.4550 C. unestami 16 03/23/11 Coosa River GA Chattooga East Fork Little River 34.5225 85.5049 C. unestami 15 03/23/11 Coosa River AL DeKalb Brush Creek 34.5348 85.5320 C. unestami 15 03/23/11 Coosa River GA Chattooga Raccoon Creek 34.4537 85.3887 C. scotti 40 03/23/11 Coosa River GA Chattooga Mosteller Creek 34.4016 85.4095 C. scotti 4 03/23/11 Coosa River GA Chattooga Clarks Creek 34.3679 85.3659 C. scotti 27 03/24/11 Coosa River GA Chattooga Chappel Creek 34.5685 85.2860 C. scotti 37 03/24/11 Coosa River GA Chattooga Cane Creek 34.5607 85.3105 C. scotti 1 03/24/11 Coosa River GA Chattooga Cane Creek 34.5700 85.3084 C. scotti 1 03/24/11 Coosa River GA Walker Cane Creek 34.6240 85.2618 C. scotti 13 03/24/11 Coosa River GA Walker Chattooga River 34.6788 85.2942 C. scotti 11 03/24/11 Coosa River GA Walker Duck Creek 34.7044 85.3260 C. scotti 15 06/07/11 Coosa River AL Talladega Choccolocco Creek 33.5430 86.0416 C. scotti 1 06/07/11 Coosa River AL Talladega Talledega Creek 33.3782 86.0301 C. scotti 0 06/07/11 Coosa River AL Calhoun Choccolocco Creek 33.6000 85.7573 C. scotti 7 06/07/11 Coosa River AL Calhoun Choccolocco Creek 33.7899 85.6604 C. scotti 4 06/07/11 Coosa River AL Cleburne Cane Creek 33.7514 85.4804 C. scotti 0 06/07/11 Coosa River AL Cleburne Terrapin Creek 33.8965 85.4696 C. scotti 22 06/08/11 Coosa River AL Calhoun Tallasseehatchee Creek 33.7900 85.9446 C. scotti 8 06/08/11 Coosa River AL Calhoun Ohatchee Creek 33.8655 85.9152 C. scotti 0 06/08/11 Coosa River AL Calhoun Nances Creek 33.9041 85.6066 C. scotti 9 Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 112 Table 1, continued. Date Drainage State County Location Latitude (°N) Longitude (°W) Species Number 06/08/11 Coosa River AL Cherokee Little Creek 34.0597 85.6256 C. scotti 1 06/08/11 Coosa River AL Cherokee Spring Creek 34.2987 85.5879 C. scotti 8 06/08/11 Coosa River AL Cherokee Chattooga River 34.2898 85.5088 C. scotti 7 06/09/11 Coosa River AL St. Clair/Etowah Little Canoe Creek 33.9725 86.1834 C. scotti 20 06/09/11 Coosa River AL Etowah Clear Creek 34.0338 86.1191 C. scotti 0 06/09/11 Coosa River AL DeKalb Big Wills Creek 34.2135 85.9470 C. scotti 0 10/03/11 Tenn. River AL DeKalb Town Creek 34.5706 85.7049 C. cracens 0 10/03/11 Tenn. River AL DeKalb Bengis Creek 34.5734 85.7512 C. cracens 0 10/03/11 Tenn. River AL DeKalb Town Creek 34.4775 85.8089 C. cracens 0 10/03/11 Tenn. River AL Jackson Bryant Creek 34.6462 85.8437 C. cracens 0 10/03/11 Tenn. River AL Jackson Bryant Creek 34.6600 85.8042 C. cracens 0 10/04/11 Tenn. River AL Jackson Guntersville Reservoir 34.6325 85.9723 C. cracens 0 10/04/11 Tenn. River AL DeKalb Black Oak Creek 34.4348 86.0306 C. cracens 0 10/04/11 Tenn. River AL DeKalb Town Creek 34.3789 85.9895 C. cracens 0 10/04/11 Tenn. River AL DeKalb Scarham Creek 34.3308 85.9779 C. cracens 0 10/04/11 Tenn. River AL DeKalb Scarham Creek 34.3047 85.9924 C. cracens 0 10/04/11 Tenn. River AL DeKalb Scarham Creek 34.2950 86.0382 C. cracens 0 10/04/11 Tenn. River AL DeKalb Little Scarham Creek 34.3063 86.0655 C. cracens 0 10/04/11 Tenn. River AL DeKalb Shoal Creek 34.3480 86.1256 C. cracens 11 10/05/11 Tenn. River AL Marshall Short Creek 34.2939 86.1622 C. cracens 0 10/05/11 Tenn. River AL Marshall Short Creek 34.2134 86.1145 C. cracens 0 10/05/11 Tenn. River AL DeKalb Cross Creek 34.2389 86.0759 C. cracens 0 10/05/11 Locust Fork River AL Marshall Clear Creek 34.1284 86.2919 None 10/05/11 Locust Fork River AL Blount Big Spring Creek 34.2024 86.4232 None 10/06/11 Locust Fork River AL Blount Calvert Prong 33.9433 86.5588 None 10/06/11 Locust Fork River AL Blount Chitwood Creek 33.9530 86.5456 None 10/06/11 Locust Fork River AL Jefferson Gurley Creek 33.7942 86.6867 None Southeastern Naturalist 113 S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 (n = 21) and new locations that held the potential for harboring any of the three target species. Many of the historical sites referenced in Hobbs (1981) and Smith et al. (2011) for C. scotti and C. unestami were close in proximity (less than 8 km) to one another; thus not all were revisited. Cambarus scotti Of the 55 sampled sites, C. scotti was found at 19 locations (Fig. 1), 10 of which were historical. This species tended to occur in streams with sluggish to moderate flow, low turbidity, substrates consisting of mostly gravel and cobble with isolated Figure 1. Map representing survey locations where Cambarus scotti was currently present (circles) and all 2011 survey sampling locations (stars). Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 114 boulder patches, and depths and widths ranging from 0.1 to 0.7 m and 2 to 35 m, respectively. It was also found at some sites that had bedrock substrate. Density estimates made at six sites are presented in Table 2. Cambarus scotti occurred most often with Orconectes erichsonianus (Faxon) (Reticulate Crayfish). Cambarus unestami This species was found to occur at nine of 55 sites (Fig. 2), six of which were historical. Creeks where this species was found had sluggish to moderate current, gravel and cobble or gravel and boulder substrates, and depths and widths of 0.1 to Figure 2. Map representing survey locations where Cambarus unestami was currently present (circles) and all 2011 survey sampling locations (stars). Southeastern Naturalist 115 S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 0.5 m and 2 to 12 m, respectively. Density measurements were made at four sites and are presented in Table 2. Cambarus unestami occurred with a variety of other species including Cambarus striatus Hay (Ambiguous Crayfish), Procambarus lophotus Hobbs and Walton (Mane Crayfish), and Cambarus parvoculus Hobbs and Shoup (Mountain Midget Crayfish). Cambarus cracens The Slenderclaw Crayfish was found at only one of the 55 sampling sites (Fig. 3). None of the five historical sites reported by Bouchard and Hobbs (1976) Figure 3. Map representing survey locations where Cambarus cracens was currently present (circle) and all 2011 survey sampling locations (stars). Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 116 yielded the species. Specimens were found at Shoal Creek at CR 372, which had moderate flow, low turbidity, and a mix of sand, cobble, and boulders, and was 0.1 m to 0.5 m deep and about 6 m wide. The density estimate for the species at this location was 0.037/m² (Table 2). Discussion The current survey presents evidence that both Cambarus scotti and Cambarus unestami appear stable across their ranges. Though not all historical locations were visited, sites selected for sampling encompassed the entire native, historical ranges for both species. For example, our sampling efforts document the continued occurrence of C. scotti from the upper Chattooga River basin in Chattooga and Walker counties, GA, south to the Choccolocco Creek drainage in Talladega County, AL (Fig. 1). While density estimates were low at some sites, C. scotti and C. unestami were collected with minimal effort in most cases. No new populations were found for either species during our surveys. We do not believe that conservation action is warranted for C. scotti and C. unestami. The range of C. unestami is relatively small compared to that of C. scotti or other imperiled southeastern aquatic taxa (Hobbs, 1981, Smith et al. 2011, Warren et al. 2000); however, our results suggest that C. unestami has not experienced population declines or loss of habitat. At all stream sites containing the species, we observed low levels of turbidity, the absence of stream modifications, and intact riparian corridors. Density estimates for the ranges of each of these species were highly variable, and ranged from 0.04 to 1.06 individuals/m². While densities at the lower end of that range suggest that both species are uncommon at many sites, our field observations suggests that these densities are similar to mean densities of other members of the genus Cambarus found throughout Alabama. Habitat for C. scotti consisted of a variety of stream sizes, with this species occurring most often in slow to moderate flow streams, from 5 to 10 m wide and 0.1 Table 2. Density estimates from select streams for Cambarus scotti, Cambarus unestami and Cambarus cracens. Location Species Density Clarks Creek C. scotti 0.300/m² Cane Creek C. scotti 0.104/m² Duck Creek C. scotti 0.050/m² Choccolocco Creek C. scotti 0.040/m² Tallasseehatchee Creek C. scotti 0.080/m² Little Canoe Creek C. scotti 0.390/m² Daniel Creek C. unestami 1.060/m² Stephens Branch C. unestami 0.430/m² Bear Creek C. unestami 0.080/m² Gilreath Creek C. unestami 0.330/m² Brush Creek C. unestami 0.100/m² Shoal Creek C. cracens 0.037/m² Southeastern Naturalist 117 S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 to 0.3 m depth, and possessing substrates made up mostly of gravel with isolated cobble and boulder patches. Some specimens were found in larger streams with widths up to 35 m and depths reaching 1 m. Habitat for C. unestami were generally first- or second-order streams in the range of 1 to 5 m in width, though some sites reached 10 m. Flow was sluggish to moderate, and depths ranged from 0.1 to 0.5 m. The substrate was composed of sand and gravel with cobble or isolated boulders interspersed or fractured bedrock. The failure to find Cambarus cracens at any of the five historical sites reported by Bouchard and Hobbs (1976) indicates the need to place this species in a category of utmost concern. These results collaborate the findings of surveys conducted by Schuster in 2005 (unpubl. data) and Taylor and Schuster in 2009 (unpubl. data), which also failed to record the species at historical locations. In addition, the type locality was intensively sampled in 2007, and C. cracens was not collected by these efforts (C. Dillman, Virginia Institute of Marine Science, Gloucester Point, VA, pers. com.). Even with the addition of new survey points to supplement historical locations, no other populations have been found. Cambarus cracens is now thought to occur at a single site in Shoal Creek (Table 1), and was also found at this site by Taylor and Schuster during a visit in 2009 (Smith et al. 2011). Habitat at this site is comprised of gravel and cobble substrate intermixed with patches of sand and thus closely matched that described at the type locality that had been previously reported (Bouchard and Hobbs 1976). However, at 6 m wide, Shoal Creek is a smaller stream than the type locality. The reasons for the decline of C. cracens are unknown, since sampling locations included habitat with proper substrate and low siltation. Riparian vegetation along both banks was in place at all sites, and no obvious signs of high nutrient loads were present. Given these observations, we suggest that waterquality measurements such as nutrient loads, heavy metals, and bacterial levels be examined at sites within the species’ range as a possible source of habitat degradation for the species. We recommend that C. cracens be considered for listing under the Endangered Species Act of 1973 (as amended). This recommendation is based on three criteria: 1) the species has experienced a significant reduction of a previously severely restricted native range, 2) the species is now currently thought to exist at only a single site, and 3) intensive field efforts have been expended without success in attempts to collect C. cracens across its native range and in other nearby locations with suitable habitat. We recommend that efforts be undertaken to determine possible causes for the apparent decline of the species. Acknowledgments We thank Jeffrey W. Simmons (Tennessee Valley Authority) for field assistance and Jeffrey Powell (US Fish and Wildlife Service) for administrative assistance in initiating this project. Funding was provided by the US Fish and Wildlife Service through the Alabama Ecological Services Field Office, Daphne, AL. Southeastern Naturalist S.L. Kilburn, C.A. Taylor, and G.A. Schuster 2014 Vol. 13, No. 1 118 Literature Cited Abell, R.A., D.M. Olsen, E. Dinerstein, P.T. Hurley, J.T. Diggs, W. Eichbaum, S. Walters, W. Wettengel, T. Allnutt, C.J. Loucks, and P. Hedao. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC. Bouchard, R.W., and H.H. Hobbs, Jr. 1976. A new subgenus and two new species of crayfishes of the genus Cambarus (Decapoda: Cambaridae) from the southeastern United States. Smithsonian Contributions to Zoology 224:1–15. 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. Neves, R.J. 1999. Conservation and commerce: Management of fres hwater mussel (Bivalvia: Unionoidea) resources in the United States. Malacologica 4 1(2):461–474. Schuster, G.A., and C.A. Taylor. 2004. Report on the crayfishes of Alabama: Literature and museum database review, species list with abbreviated annotations, and proposed conservation statuses. Illinois Natural History Survey, Center for Biodiversity Technical Report 12. Champaign, IL. Smith, J.B., G.A. Schuster, C.A. Taylor, E.A.Wynn, and S.W. McGregor. 2011. A preliminary report on the distribution and conservation status of the Alabama crayfish fauna. Open File Report 1102, Geological Survey of Alabama, Tuscaloosa, AL. Taylor, C.A. 2002. Taxonomy and conservation of native crayfish stocks. Pp. 236–257, In D.M. Holdich (Ed.). Biology of Freshwater Crayfish. Blackwell Science Ltd., Oxford, UK. Taylor, C.A., M.L. Warren, Jr., J.F. Fitzpatrick, Jr., H.H. Hobbs, III, R.F. Jezerinac, W.L. Pflieger, and H.W. Robison. 1996. Conservation status of crayfishes of the United States and Canada. Fisheries 21:25–38. Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs, H.W. Robison, C.E. Skelton, and R.E. Thoma. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32(8):372–389. Warren, Jr., M.L., B.M. Burr, S.J., Walsh, H.L. Bart Jr., R.C. Cashner, D.A. Etnier, B.J. Freeman, B.R. Kuhajde, R.L. Mayden, H.W. Robison, and W.D. Starnes. 2000. Diversity, distribution, and conservation status of the native freshwater fishes of the southern United States. Fisheries 25(10):7–31.