Pleurobema hanleyianum - (I. Lea, 1852)
Georgia Pigtoe
Taxonomic Status: Accepted
Related ITIS Name(s): Pleurobema aldrichianum Goodrich (TSN 80116) ;Pleurobema hanleyianum (I. Lea, 1852) (TSN 80101)
Unique Identifier: ELEMENT_GLOBAL.2.116006
Element Code: IMBIV35160
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Pleurobema
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
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Concept Reference: Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.
Concept Reference Code: B98TUR01EHUS
Name Used in Concept Reference: Pleurobema hanleyianum
Taxonomic Comments: Spelling of the name follows the original publication (Turgeon et al., 1998). It is difficult to differentiate this species from Pleurobema georgianum and Pleurobema trochelianum in the field due to similar shell characteristics (Parmalee and Bogan, 1998), but some morphological features of each are outlined in USFWS (2003). Recent genetic studies were unable to distinguish the painted clubshell from the southern clubshell (listed as endangered), or populations of Georgia pigtoe and Alabama clubshell from southern pigtoe (listed as endangered) (P. Johnson, Tennessee Aquarium, pers. comm. 2002). The uniqueness of the species has been verified morphologically (Williams et al., 2008) and genetically (Campbell et al., 2008).
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 23Dec2011
Global Status Last Changed: 30Aug2000
Rounded Global Status: G1 - Critically Imperiled
Reasons: This species has experienced a tremendous reduction in number of locations and population size recently to the point where it was officially declared extinct by the IUCN in 1994. Recently, a single subpopulation with only a few live individuals was found in a very localized portion of the upper Conasauga River in Georgia. Otherwise, a collection of recently dead shells (1997-1998) and a recently discovered population in the Upper Conasauga River are all that remain of the global population of this species which has experienced an extensive reduction in former range. It has recently been listed by USFWS as an endangered species and Critical Habitat designated. Up until recently, it had formerly been thought extinct.
Nation: United States
National Status: N1 (30Aug2000)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (SX), Georgia (S1), Tennessee (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (02Nov2010)
Comments on USESA: USFWS (Federal Register, 02 November 2010) listed this species as endangered and designated approximately 258 kilometers (km) (160 miles (mi)) of stream and river channels as critical habitat, in Cherokee, Clay, Coosa, Elmore, and Shelby Counties, Alabama; Gordon, Floyd, Murray, and Whitfield Counties, Georgia; and Bradley and Polk Counties, Tennessee.
U.S. Fish & Wildlife Service Lead Region: R4 - Southeast
IUCN Red List Category: CR - Critically endangered
American Fisheries Society Status: Endangered (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: <100 square km (less than about 40 square miles)
Range Extent Comments: This species was historically found in the Conasauga River in Tennessee and Georgia, the Coosawatee, Oostanaula, Coosa, and Etowah Rivers in Georgia, and the Coosa River and following tributaries in Alabama: Big Wills, Terrapin, Big Canoe, Yellowleaf, Waxahatchee, Talledega, and Hatchet creeks (USFWS, 1999; 2003; 2009; 2010). In the Coosa River basin in Georgia, it is known historically from the Coosa, Etowah, Oostanaula, Conasauga, and Coosawattee River drainages (Williams and Hughes, 1998). Recently, fresh dead shells were collected in the upper Conasauga River above Dalton, Georgia (USFWS, 1999; 2003) and a single large specimen found alive also in the Conasauga River in Georgia (P. Johnson, TN Aquarium Research Institute, pers. comm.). The species has been extirpated from Alabama (Mirarchi et al., 2004; Mirarchi, 2004) where it was endemic to the Mobile basin; and nearly so in Tennessee (see Johnson et al., 2005) and Georgia (Williams et al., 2008).

Area of Occupancy: 3-125 4-km2 grid cells
Area of Occupancy Comments: It currently only occupies small stretches within a a 43 km reach of the Upper Conasauga River in Murray and Whitfield Cos., Georgia, and in Polk Co., Tennessee (USFWS, 2010).

Number of Occurrences: 1 - 5
Number of Occurrences Comments: Recent survey efforts have been extensive since 1990 when the USFWS initated a status survey in the Mobile River Basin. The species was, at the time, presumed extinct, but recent collections yielded a few fresh dead shells from localized portions of the Upper Conasauga River in Murray and Whitfield Counties, Georgia (Williams and Hughes, 1998; Johnson and Evans, 2000; Evans, 2001; USFWS, 2010). This species has been recently reported as a relict shell from the Conasauga River inside and adjacent to the Cherokee and Chattahoochee National Forests, Polk Co., Tennessee (Johnson et al., 2005). Williams and Hughes (1998) cite potential records for Pleurobema perovatum in the Conasauga River drainage in Georgia, but both Paul Johnson and Paul Hartfiled believe that Georgia records for Pleurobema perovatum actually represent another Pleurobema (believed to be Pleurobema hanleyianum) (see USFWS, 2010). Gangloff (2003) surveyed all known historical sites for the species in Coosa River tributaries in Alabama without relocating the species. Similarly, McGregor and Garner (2004) surveyed the Coosa River dam tailraces without locating it either.

Population Size: 1 - 1000 individuals
Population Size Comments: Currently this species is only known from a few recently dead shells (USFWS, 2003) and a recently discovered population represented by a single live individual indicating populations are likely no longer viable or extremely small (Johnson and Evans, 2000; USFWS, 2010).

Number of Occurrences with Good Viability/Integrity: None (zero)
Viability/Integrity Comments: It is highly unlikely that the 1 remaining occurrences show good viability.

Overall Threat Impact: Very high - high
Overall Threat Impact Comments: Much of the information contained herein was derived from USFWS (2003; 2010):
About 50 percent (161 km (100 miles)) of the historic habitat of this species is affected by dams. Rivers impounded by dams have reduced water velocities, allowing sediments to accumulate on river channel habitats behind dams. Impounded waters also experience changes in water chemistry, which can affect survival or reproduction of riverine snails. The disappearance of shoal populations from unimpounded relict habitats in the Coosa River drainage is likely due to historical pollution problems. Prior to the passage of the Clean Water Act and the adoption of State water quality criteria, water pollution may have been a significant factor in the disappearance of populations from unimpounded portions of river channels. Short-term and long-term impacts of point and non-point source water and habitat degradation continue to be a primary concern for the survival of this species. Point source discharges and land surface runoff (non-point pollution) can cause nutrification, decreased dissolved oxygen concentration, increased acidity and conductivity, and other changes in water chemistry that are likely to seriously impact aquatic snails. Point sources of water quality degradation include municipal and industrial effluents. Non-point source pollution from land surface runoff can originate from virtually any ground-disturbing land use activity and may include sediments, fertilizers, herbicides, pesticides, animal wastes, septic tank and gray water leakage, and oils and greases. This species is not commercially utilized and scientific collecting is not considered a factor in the decline of the species. The potential now exists for the black carp (Mylopharyngodon piceus), a mollusk-eating Asian fish recently introduced into the waters of the United States, to eventually enter and disperse through the Mobile River Basin via the Tennessee-Tombigbee Waterway, or by their accidental release from catfish farms or other aquaculture facilities. There is a growing concern that climate change may lead to increased frequency of severe storms and droughts. During 2007 and 2008, a severe drought affected the Coosa River watershed in Alabama and Georgia. Streamflow for the Conasauga River at Tilton, Georgia, during September 2007, was the lowest recorded for any month in 69 years. Although the effects of the drought have not been quantified, mollusk declines as a direct result of drought have been documented. Because these animals are only capable of moving short distances and there are numerous obstacles in the Coosa River drainage preventing long distance movement of freshwater mollusks between relict patches of historically occupied and potentially suitable riverine habitats, following potential climate change events, populations will likely be unable to recolonize those areas without human assistance.

Causes of the decline can be attributed to extensive impoundment of the Coosa River and its primary tributaries, and the effects of point and non-point source pollution on the surviving isolated populations. Isolated populations are vulnerable to land surface runoff that affects water quality or the suitability of aquatic habitats within a watershed. Blocked from avenues of emigration to less affected watersheds, they gradually perish if changes in land use activities cause aquatic habitat conditions to deteriorate. While the detrimental effect of any one source or land use activity may be insignificant by itself, the combined effects of land use runoff within a watershed may result in gradual and cumulative adverse impacts to isolated populations and their habitats. Excessive nutrient input from multiple sources (e.g, nitrogen and phosphorus from fertilizer, sewage waste, animal manure, etc.) into an aquatic system can also have negative cumulative effects (USFWS, 2003; 2010).

Short-term Trend: Decline of >70%
Short-term Trend Comments: This species is thought to be extirpated from over 90 percent of its historic range (USFWS, 1999; 2003; 2009). In 1990, the U.S. Fish and Wildlife Service initiated a status survey and review of the molluscan fauna of the Mobile River Basin reported 14 species of mussels in the genus Pleurobema, including the painted clubshell, Georgia pigtoe, and Alabama clubshell, as presumed extinct in the Mobile River Basin, based on their absence from collection records, technical reports, or museum collections for a period of 20 years or more (USFWS, 1994). The species was considered extinct by the IUCN (Baillie and Groombridge, 1996) in 1994. Recent occurrences are only represented at 1 or 2 localities and only by a handfull of live individuals, dead, or recently dead shell material a 43 km reach of the Upper Conasauga River in Murray and Whitfield Cos., Georgia, and in Polk Co., Tennessee (USFWS, 2010).

Long-term Trend: Decline of >90%
Long-term Trend Comments: The Georgia pigtoe was historically reported from the Conasauga River in Tennessee and Georgia; the Coosawatee, Oostanaula, Coosa, and Etowah Rivers in Georgia; and the Coosa River and tributaries Big Wills, Terrapin, Big Canoe, Yellowleaf, Waxahatchee, Talledega, and Hatchet Creeks, in Alabama. Historical range included more than 480 km of river and stream channels but has declined to where it now occupies only a 43 km reach of the Upper Conasauga River in Murray and Whitfield Cos., Georgia, and in Polk Co., Tennessee. Pleurobema hanleyianum has been extirpated from well over 90 percent of their historic range (USFWS, 2010).

Intrinsic Vulnerability: Highly vulnerable
Intrinsic Vulnerability Comments: Threats are compounded by their restricted range and low numbers. This species is vulnerable to random catastrophic events (e.g., flood scour, drought, toxic spills, etc.). Limited range and low numbers also make the species vulnerable to land use changes within the Conasauga River watershed that would result in increases in non-point source pollution impacts (USFWS, 2003; 2010).

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Other NatureServe Conservation Status Information

Protection Needs: The U.S. Fish and Wildlife Service is working to establish a National Wildlife Refuge in the upper Conasauga River. Watershed management outreach has been conducted. The Nature Conservancy has conducted a watershed impact analysis for the Conasauga River watershed. Surveys are ongoing, and genetic studies will be continuing to clarify and confirm taxonomy of this species.

Distribution
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Global Range: (<100 square km (less than about 40 square miles)) This species was historically found in the Conasauga River in Tennessee and Georgia, the Coosawatee, Oostanaula, Coosa, and Etowah Rivers in Georgia, and the Coosa River and following tributaries in Alabama: Big Wills, Terrapin, Big Canoe, Yellowleaf, Waxahatchee, Talledega, and Hatchet creeks (USFWS, 1999; 2003; 2009; 2010). In the Coosa River basin in Georgia, it is known historically from the Coosa, Etowah, Oostanaula, Conasauga, and Coosawattee River drainages (Williams and Hughes, 1998). Recently, fresh dead shells were collected in the upper Conasauga River above Dalton, Georgia (USFWS, 1999; 2003) and a single large specimen found alive also in the Conasauga River in Georgia (P. Johnson, TN Aquarium Research Institute, pers. comm.). The species has been extirpated from Alabama (Mirarchi et al., 2004; Mirarchi, 2004) where it was endemic to the Mobile basin; and nearly so in Tennessee (see Johnson et al., 2005) and Georgia (Williams et al., 2008).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States ALextirpated, GA, TN

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
GA Murray (13213), Whitfield (13313)
TN Polk (47139)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Conasauga (03150101)+, Coosawattee (03150102)*, Oostanaula (03150103)*, Etowah (03150104)*, Upper Coosa (03150105)*, Middle Coosa (03150106)*, Lower Coosa (03150107)*, Lower Tallapoosa (03150110)*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: a freshwater mussel
Reproduction Comments: The glochidial host is not known.

Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): High gradient, MEDIUM RIVER, Moderate gradient, Riffle
Special Habitat Factors: Benthic
Habitat Comments: This species inhabits stretches of a medium sized river with good current and a sand/gravel substrate A substrate composed of coarse sand and gravel in stretches of rivers with good current provides the most suitable habitat (Parmalee and Bogan, 1998). It is found in shallow runs and riffles with strong to moderate current and coarse sand-gravel-cobble bottom (USFWS, 2010).
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: This species was recently designated as endangered by the U.S. Fish and Wildlife Service with 148 km of Critical Habitat designated.
Population/Occurrence Delineation
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Group Name: Freshwater Mussels

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached and/or nacre still glossy and iridescent without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Based on the separation distances outlined herein, for freshwater mussels in STANDING WATER (or backwater areas of flowing water such as oxbows and sloughs), all standing water bodies with either (1) greater than 2 km linear distance of unsuitable habitat between (i.e. lotic connections), or (2) more than 10 km of apparently unoccupied though suitable habitat (including lentic shoreline, linear distance across water bodies, and lentic water bodies with proper lotic connections), are considered separate element occurrences. Only the largest standing water bodies (with 20 km linear shoreline or greater) may have greater than one element occurrence within each. Multiple collection or observation locations in one lake, for example, would only constitute multiple occurrences in the largest lakes, and only then if there was some likelihood that unsurveyed areas between collections did not contain the element.

For freshwater mussels in FLOWING WATER conditions, occurrences are separated by a distance of more than 2 stream km of unsuitable habitat, or a distance of more than 10 stream km of apparently unoccupied though suitable habitat. Standing water between occurrences is considered suitable habitat when calculating separation distance for flowing water mussel species unless dispersal barriers (see Separation Barriers) are in place.

Several mussel species in North America occur in both standing and flowing water (see Specs Notes). Calculation of separation distance and determination of separation barriers for these taxa should take into account the environment in which the element was collected. Juvenile mussels do not follow this pattern and juveniles are typically missed by most standard sampling methods (Hastie and Cosgrove, 2002; Neves and Widlak, 1987), therefore juvenile movement is not considered when calculating separation distance.

Separation Barriers: Separation barriers within standing water bodies are based solely on separation distance (see Separation Distance-suitable, below). Separation barriers between standing water bodies and within flowing water systems include lack of lotic connections, natural barriers such as upland habitat, absence of appropriate species specific fish hosts, water depth greater than 10 meters (Cvancara, 1972; Moyle and Bacon, 1969) or anthropogenic barriers to water flow such as dams or other impoundments and high waterfalls.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: None
Separation Justification: Adult freshwater mussels are largely sedentary spending their entire lives very near to the place where they first successfully settled (Coker et al., 1921; Watters, 1992). Strayer (1999) demonstrated in field trials that mussels in streams occur chiefly in flow refuges, or relatively stable areas that displayed little movement of particles during flood events. Flow refuges conceivably allow relatively immobile mussels to remain in the same general location throughout their entire lives. Movement occurs with the impetus of some stimulus (nearby water disturbance, physical removal from the water such as during collection, exposure conditions during low water, seasonal temperature change or associated diurnal cycles) and during spawning. Movement is confined to either vertical movement burrowing deeper into sediments though rarely completely beneath the surface, or horizontal movement in a distinct path often away from the area of stimulus. Vertical movement is generally seasonal with rapid descent into the sediment in autumn and gradual reappearance at the surface during spring (Amyot and Downing, 1991; 1997). Horizontal movement is generally on the order of a few meters at most and is associated with day length and during times of spawning (Amyot and Downing, 1997). Such locomotion plays little, if any, part in the distribution of freshwater mussels as these limited movements are not dispersal mechanisms. Dispersal patterns are largely speculative but have been attributed to stream size and surface geology (Strayer, 1983; Strayer and Ralley, 1993; van der Schalie, 1938), utilization of flow refuges during flood stages (Strayer, 1999), and patterns of host fish distribution during spawning periods (Haag and Warren, 1998; Watters, 1992). Lee and DeAngelis (1997) modeled the dispersal of freshwater into unoccupied habitats as a traveling wave front with a velocity ranging from 0.87 to 2.47 km/year (depending on mussel life span) with increase in glochidial attachment rate to fish having no effect on wave velocity.

Nearly all mussels require a host or hosts during the parasitic larval portion of their life cycle. Hosts are usually fish, but a few exceptional species utilize amphibians as hosts (Van Snik Gray et al., 2002; Howard, 1915) or may metamorphose without a host (Allen, 1924; Barfield et al., 1998; Lefevre and Curtis, 1911; 1912). Haag and Warren (1998) found that densities of host generalist mussels (using a variety of hosts from many different families) and displaying host specialists (using a small number of hosts usually in the same family but mussel females have behavioral modifications to attract hosts to the gravid female) were independent of the densities of their hosts. Densities of non-displaying host specialist mussels (using a small number of hosts usually in the same family but without host-attracting behavior) were correlated positively with densities of their hosts. Upstream dispersal of host fish for non-displaying host specialist mussels could, theoretically, transport mussel larvae (glochidia) over long distances through unsuitable habitat, but it is unlikely that this occurs very often. D. Strayer (personal communication) suggested a distance of at least 10 km, but a greater distance between occurrences may be necessary to constitute genetic separation of populations. As such, separation distance is based on a set, though arbitrary, distance between two known points of occurrence.

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Contact Jay Cordeiro (jay_cordeiro@natureserve.org) for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 23Dec2011
NatureServe Conservation Status Factors Author: Cordeiro, J. (2011); Morrison, M. (2000)
Management Information Edition Date: 03Nov2010
Management Information Edition Author: Cordeiro, J.
Element Ecology & Life History Edition Date: 23Dec2011
Element Ecology & Life History Author(s): Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
Help
  • Campbell, D.C., P.D. Johnson, J.D. Williams, A.K. Rindsberg, J.M. Serb, K.K. Small, and C. Lydeard. 2008. DNA barcoding: Identificatio of 'extinct' freshwater mussel species using DNA barcoging. Molecular Ecology Resources, 8: 711-724.

  • Howard, A.D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.

  • Johnson, P.D., C. St. Aubin, and S.A. Ahlstedt. 2005. Freshwater mussel survey results for the Cherokee and Chattahoochee districts of the United States Forest Service in Tennessee and Georgia. Report to the U.S. Fish and Wildlife Service, Daphne, Alabama. 32 pp.

  • Lefevre, G. and W.T. Curtis. 1912. Studies on the reproduction and artificial propogation of fresh-water mussels. Bulletin of the Bureau of Fisheries 30:102-201.

  • Mirarchi, R.E., J.T. Garner, M.F. Mettee, and P.E. O'Neil. 2004b. Alabama wildlife. Volume 2. Imperiled aquatic mollusks and fishes. University of Alabama Press, Tuscaloosa, Alabama. xii + 255 pp.

  • Mirarchi, R.E., et al. 2004a. Alabama Wildlife. Volume One: A Checklist of Vertebrates and Selected Invertebrates: Aquatic Mollusks, Fishes, Amphibians, Reptiles, Birds, and Mammals. University of Alabama Press: Tuscaloosa, Alabama. 209 pp.

  • Moyle, P. and J. Bacon. 1969. Distribution and abundance of molluscs in a fresh water environment. Journal of the Minnesota Academy of Science 35(2/3):82-85.

  • Parmalee, P.W. and A.E. Bogan. 1998. The Freshwater Mussels of Tennessee. University of Tennessee Press: Knoxville, Tennessee. 328 pp.

  • Parmalee, P.W. and A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville, Tennesee. 328 pp.

  • Strayer, D. 1983. The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A. Freshwater Biology 13:253-264.

  • Strayer, D.L. 1999a. Use of flow refuges by unionid mussels in rivers. Journal of the North American Benthological Society 18(4):468-476.

  • Strayer, D.L. and J. Ralley. 1993. Microhabitat use by an assemblage of stream-dwelling unionaceans (Bivalvia) including two rare species of Alasmidonta. Journal of the North American Benthological Society 12(3):247-258.

  • Turgeon, D.D., A.E. Bogan, E.V. Coan, W.K. Emerson, W.G. Lyons, W.L. Pratt, C.F.E. Roper, A. Scheltema, F.G. Thompson, and J.D. Williams. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. American Fisheries Society Special Publication 16: viii + 277 pp., 12 pls.

  • Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.

  • U.S. Fish and Wildlife Service (USFWS). 1999. Candidate and listing priority assignment forms.

  • U.S. Fish and Wildlife Service (USFWS). 2003. Candidate assessment and listing priority assignment form- Pleurobema chattanoogaense, Pleurobema hanleyanum, Pleurobema troshelianum. U.S. Fish and Wildlife Service, Jacksonville, Mississippi. 8 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2004. Endangered and Threatened Widlife and plants; designation of critical habitat for three threatened mussels and eight endangered mussels in the Mobile River basin; final rule. Federal Register, 69(126): 40083-40171.

  • U.S. Fish and Wildlife Service (USFWS). 2009. Endangered and threatened wildlife and plants; proposed endangered status for the Georgia pigtoe mussel, interrupted rocksnail, and rough hornsnail with Critical Habitat. Federal Register 74(123):31114-31151.

  • U.S. Fish and Wildlife Service (USFWS). 2010. Endangered and threatened wildlife and plants; determination of endangered status for the Georgia pigtoe mussel, interrupted rocksnail, and rough hornsnail and designation of critical habitat. Federal Register 75(211):67512-67550.

  • U.S. Fish and Wildlife Service. 2014. Recovery plan for the Georgia pigtoe mussel, interrupted rocksnail, and rough hornsnail. U.S. Fish and Wildlife Service, Atlanta, Georgia. 55 pages.

  • Van der Schalie, H. 1938a. The naiad fauna of the Huron River in southeastern Michigan. Miscellaneous Publication of the Museum of Zoology, University of Michigan 40:7-78.

  • Watters, G.T. 1992a. Unionids, fishes, and the species-area curve. Journal of Biogeography 19:481-490.

  • Williams, J. D., A. E. Bogan, and J. T Garner. 2008. Freshwater mussels of Alabama & the Mobile Basin in Georgia, Mississippi, & Tennessee. University of Alabama Press, Tuscaloosa, Alabama. 908 pages.

  • Williams, J.D., M.L. Warren, Jr., K.S. Cummings, J.L. Harris, and R.J. Neves. 1993b. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.

  • Williams, James, Arthur Bogan, and Jeffrey Garner. 2008. Freshwater Mussels of Alabama and the Mobile Basin in Georgia, Mississippi, and Tennessee. University of Alabama Press, Tuscaloosa, AL. pp 908

References for Watershed Distribution Map
  • Williams, J.D. and M.H. Hughes. 1998. Freshwater mussels of selected reaches of the main channel rivers in the Coosa drainage of Georgia. U.S. Geological report to U.S. Army Corps of Engineers, Mobile District, Alabama. 21 pp.

  • Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater Mussels of Alabama & the Mobile Basin in Georgia, Mississippi & Tennessee. University of Alabama Press: Tuscaloosa, Alabama. 908 pp.

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http://www.natureserve.org/library/mammalsDistributionmetadatav1.pdf.

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