Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough Hornsnail with Critical Habitat, 31114-31151 [E9-15236]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 74, Number 123 (Monday, June 29, 2009)]
[Proposed Rules]
[Pages 31114-31151]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-15236]



[[Page 31113]]

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Part II





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Proposed Endangered 
Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough 
Hornsnail with Critical Habitat; Proposed Rule

Federal Register / Vol. 74, No. 123 / Monday, June 29, 2009 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R4-ES-2008-0104; MO 9221050083]
RIN 1018-AU88


Endangered and Threatened Wildlife and Plants; Proposed 
Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, 
and Rough Hornsnail with Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
list the Georgia pigtoe mussel (Pleurobema hanleyianum), interrupted 
rocksnail (Leptoxis foremani), and rough hornsnail (Pleurocera 
foremani), as endangered species under the Endangered Species Act of 
1973, as amended (Act). The Georgia pigtoe, interrupted rocksnail, and 
rough hornsnail are endemic to the Coosa River drainage within the 
Mobile River Basin of Alabama, Tennessee, and Georgia. These three 
species have disappeared from large portions of their natural ranges 
due to extensive construction of dams that eliminated or reduced water 
currents and caused changes in habitat and water quality. The surviving 
populations are small, localized, and highly vulnerable to water 
quality and habitat deterioration.
    We are also proposing to designate critical habitat concurrently 
for the Georgia pigtoe, interrupted rocksnail, and rough hornsnail 
under the Act. In total, approximately 258 kilometers (km) (160 miles 
(mi)) of stream and river channels fall within the boundaries of the 
proposed critical habitat designation for the three species: 153 km (95 
mi) for the Georgia pigtoe, 101 km (63 mi) for the interrupted 
rocksnail, and 27.4 km (17 mi) for the rough hornsnail. The proposed 
critical habitat is located in Cherokee, Clay, Coosa, Elmore, and 
Shelby Counties, Alabama; Gordon, Floyd, Murray, and Whitfield 
Counties, Georgia; and Bradley and Polk Counties, Tennessee.
    These proposals, if made final, would implement Federal protection 
provided by the Act.

DATES: We will accept comments received on or before August 28, 2009. 
We must receive requests for public hearings, in writing, at the 
address shown in the FOR FURTHER INFORMATION CONTACT section by August 
13, 2009.

ADDRESSES: You may submit comments by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. Follow the instructions for submitting comments.
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: RIN 1018-AU88; Division of Policy and Directives Management; U.S. 
Fish and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, 
VA 22203.
    We will not accept e-mail or faxes. We will post all comments on 
https://www.regulations.gov. This generally means that we will post any 
personal information you provide us (see the Public Comments section 
below for more information).

FOR FURTHER INFORMATION CONTACT: Cary Norquist, Acting Field 
Supervisor, Mississippi Fish and Wildlife Office at 6578 Dogwood View 
Parkway, Suite A, Jackson, MS 39213 (telephone 601-321-1122; facsimile 
601-965-4340). If you use a telecommunications device for the deaf 
(TDD), you may call the Federal Information Relay Service (FIRS) at 
800-877-8339.

SUPPLEMENTARY INFORMATION:

Public Comments

    We intend that any final action resulting from this proposal will 
be as accurate and as effective as possible. Therefore, we are seeking 
comments or suggestions from the public, other concerned governmental 
agencies, the scientific community, industry, or any other interested 
party concerning this proposed rule. We particularly seek comments 
concerning:
    (1) Any biological, commercial trade, or other relevant data 
concerning any threat (or lack thereof) to the Georgia pigtoe mussel, 
interrupted rocksnail, and rough hornsnail;
    (2) Any additional information concerning the ranges, 
distributions, and population sizes of the species;
    (3) Land use designations and current or planned activities in the 
subject area and their possible impacts on these species or proposed 
critical habitats;
    (4) The reasons why any area should or should not be designated as 
critical habitat as provided by section 4 of the Act (16 U.S.C. 1531 et 
seq.), including whether the benefit of designation would outweigh 
threats to the species caused by designation such that the designation 
of critical habitat is prudent;
    (5) Specific information on the amount and distribution of habitat 
for the Georgia pigtoe, interrupted rocksnail, and rough hornsnail, 
including areas occupied at the time of listing and containing the 
features essential to the conservation of the species, and areas not 
occupied at the time of listing that are essential to the conservation 
of the species and why;
    (6) Any foreseeable economic, national security, or other potential 
impacts resulting from the proposed designation and, in particular, any 
impacts on small entities, and information about the benefits of 
including or excluding any areas that exhibit those impacts; and
    (7) Whether our approach to designating critical habitat could be 
improved or modified in any way to provide for greater public 
participation and understanding, or to assist us in accommodating 
public concerns and comments.
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We will not 
accept comments you send by e-mail or fax or to an address not listed 
in the ADDRESSES section.
    We will post your entire comment--including your personal 
identifying information--on https://www.regulations.gov. If you provide 
personal identifying information in addition to the required items 
specified in the previous paragraph, such as your street address, phone 
number, or e-mail address, you may request at the top of your document 
that we withhold this information from public review. However, we 
cannot guarantee that we will be able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on https://www.regulations.gov, or by 
appointment, during normal business hours, at the U.S. Fish and 
Wildlife Service, Mississippi Fish and Wildlife Office (see FOR FURTHER 
INFORMATION CONTACT).

Background

Georgia Pigtoe Mussel
    The Georgia pigtoe (Pleurobema hanleyianum) is a freshwater mussel 
in the family Unionidae. It was described in 1852 by I. Lea as Unio 
hanleyianum from the Coosawattee River in Georgia. It was placed in the 
genus Pleurobema by Simpson in 1900. The uniqueness of the Georgia 
pigtoe has been verified both morphologically (Williams et al. 2008, p. 
533) and genetically (Campbell et al. 2008, pp. 719-721).
    The shell of the Georgia pigtoe reaches about 50 to 65 millimeters 
(mm) (2 to 2.5 inches (in)) in length. It is oval to elliptical and 
somewhat inflated. The posterior ridge is low and evenly

[[Page 31115]]

rounded when evident. The anterior end is rounded, while the posterior 
margin is bluntly pointed below. Dorsal and ventral margins are curved, 
and the beaks rise slightly above the hinge line. The periostracum 
(membrane on the surface of the shell) is yellowish-tan to reddish-
brown and may have concentric green rings. The beak cavity is shallow, 
and the shell interior is white to dull bluish-white (Parmalee and 
Bogan 1998, p. 185; Williams et al. 2008, p. 533).
    Little is known about the habitat requirements or life history of 
the Georgia pigtoe; however, it is found in shallow runs and riffles 
with strong to moderate current and coarse sand-gravel-cobble bottoms. 
Unionid mussels, such as the Georgia pigtoe, filter-feed on algae, 
detritus, and bacteria from the water column. The larvae of most 
unionid mussels are parasitic, requiring a period of encystment on a 
fish host before they can develop into juvenile mussels. The fish host 
and glochidia (parasitic larvae) of Georgia pigtoe are currently 
unknown.
    The Georgia pigtoe was historically found in large creeks and 
rivers of the Coosa River drainage of Alabama, Georgia, and Tennessee 
(Johnson and Evans 2000, p. 106; Williams et al., 2008, p. 534). There 
are historical reports or museum records of the Georgia pigtoe from 
Tennessee (Conasauga River in Polk and Bradley Counties), Georgia 
(Conasauga River in Murray and Whitfield Counties, Chatooga River in 
Chatooga County; Coosa River in Floyd County, Etowah River in Floyd 
County), and Alabama (Coosa River in Cherokee County, Terrapin Creek in 
Cherokee County, Little Canoe and Shoal Creeks in St. Clair County, 
Morgan Creek in Shelby County, and Hatchet Creek in Coosa County) 
(Florida Museum of Natural History Malacology Database (FLMNH) 2006; 
Gangloff 2003, p. 45). Based on these historical records, the range of 
the Georgia pigtoe included more than 480 km (300 mi) of river and 
stream channels. Additional historical Coosa River tributary records 
credited to Hurd (1974, p. 64) (for example, Big Wills, Little Wills, 
Big Canoe, Oothcalooga, Holly Creeks) have been found to be 
misidentifications of other species (M. Gangloff in litt. 2006).
    In 1990, the Service initiated a status survey and review of the 
molluscan fauna of the Mobile River Basin (Hartfield 1991, p. 1). This 
led to extensive mollusk surveys and collections throughout the Coosa 
River drainage (Bogan and Pierson 1993a, pp. 1-27; P. Hartfield in 
litt. 1990-2001). At all localities surveyed in the Coosa River 
drainage, the freshwater mussel fauna had declined from historical 
levels, and at all but a few localized areas, the fauna proved to be 
completely eliminated or severely reduced due to a variety of impacts, 
including point and non-point source pollution, and channel 
modifications such as impoundment. Following a review of these efforts 
and observations, the Service reported 14 species of mussels in the 
genus Pleurobema, including the Georgia pigtoe, as presumed extinct, 
based on their absence from collection records, technical reports, or 
museum collections for a period of 20 years or more (Hartfield 1994, p. 
1).
    The Service and others continued to conduct surveys in the Coosa 
River drainage for mollusks (P. Hartfield in litt. 1990-2001; Williams 
and Hughes 1998, pp. 2-6; Johnson and Evans 2000, p. 106; Herod et al. 
2001, pp i-ii; Gangloff 2003, pp. 11-12; McGregor and Garner 2004, pp. 
1-18; Johnson et al. 2005, p. 1). Several freshly dead and live 
individuals of the Georgia pigtoe were collected during these mussel 
surveys in the Upper Conasauga River, Murray and Whitfield Counties, 
Georgia (Williams and Hughes 1998, p. 10; Johnson and Evans 2000, p. 
106). Gangloff (2003, pp. 11-12, 45) conducted mussel surveys of Coosa 
River tributaries in Alabama, including all known historical collection 
sites for the Georgia pigtoe, without relocating the species. McGregor 
and Garner (2004, p. 8) surveyed the Coosa River dam tailraces for 
mollusks without encountering the Georgia pigtoe.
    The Georgia pigtoe is currently known from a few isolated shoals in 
the Upper Conasauga River in Murray and Whitfield Counties, Georgia, 
and in Polk County, Tennessee (Johnson and Evans 2000, p. 106; Evans 
2001, pp. 33-34). All recent collection sites occur within a 43-km (27-
mi) reach of the river. Within this reach, the Georgia pigtoe is very 
rare (Johnson and Evans 2000, p. 106), and no population estimates are 
available.
Interrupted Rocksnail
    The interrupted rocksnail (Leptoxis foremani) is a small-to-medium-
sized freshwater snail that historically occurred in the Coosa River 
drainage of Alabama and Georgia. The shell grows to approximately 22 mm 
(1 in) in length and may be plicate (folds in the surface) with obscure 
striations (fine longitudinal ridges), subglobose (not quite 
spherical), thick, dark, brown to olive in color, and occasionally 
spotted. The spire (apex) of the shell is very low, and the aperture 
(opening) is large and subrotund (not quite round).
    The interrupted rocksnail, a member of the aquatic snail family 
Pleuroceridae, was described from the Coosa River, Alabama, by Lea in 
1843. Goodrich (1922, p. 13) placed the species in the ``Anculosa 
(=Leptoxis) picta (Conrad 1834) group,'' which also included the 
Georgia rocksnail (Leptoxis downei (Lea 1868)). L. foremani was 
considered to inhabit the Lower Coosa River, with L. downei inhabiting 
the Upper Coosa drainage (Goodrich 1922, pp. 18-19, 21-23). When a 
rocksnail population was rediscovered surviving in the Oostanaula 
River, Georgia, in 1997, it was initially identified as L. downei 
(Williams and Hughes 1998, p. 9; Johnson and Evans 2000, pp. 45-46); 
however, Burch (1989, p. 155) had previously placed L. downei within L. 
foremani as an ecological variation. Therefore, L. downei is currently 
considered an upstream phenotype of the interrupted rocksnail, and L. 
foremani is recognized as the valid name for the interrupted rocksnail 
(Turgeon et al. 1998, p. 67; Johnson 2004, p. 116).
    Rocksnails live in shoals, riffles, and reefs (bedrock outcrops) of 
small to large rivers. Their habitats are generally subject to moderate 
currents during low flows and strong currents during high flows. These 
snails live attached to bedrocks, boulders, cobbles, and gravel and 
tend to move little, except in response to changes in water level. They 
lay their adhesive eggs within the same habitat (Johnson 2004, p. 116). 
Interrupted rocksnails are currently found in shoal habitats with sand-
boulder substrate, at water depths less than 50 centimeters (cm) (20 
in), and in water currents less than 40 cm/second (sec) (16 in/sec) 
(Johnson 2004, p. 116). We know little of the life history of 
pleurocerid snails; however, they generally feed by ingesting 
periphyton (algae attached to hard surfaces) and biofilm detritus 
scraped off of the substrate by the snail's radula (a horny band with 
minute teeth used to pull food into the mouth) (Morales and Ward 2000, 
p. 1). Interrupted rocksnails have been observed grazing on silt-free 
gravel, cobble, and boulders (Johnson 2004, p. 116). They have survived 
as long as 5 years in captivity (Johnson in litt. 2006b).
    The interrupted rocksnail was historically found in colonies on 
reefs and shoals of the Coosa River and several of its tributaries in 
Alabama and Georgia. The range of the rocksnail formerly encompassed 
more than 800 km (500 mi) of river and stream channels, including the 
Coosa River (Coosa, Calhoun, Cherokee, Elmore, Etowah, Shelby, St. 
Clair, and Talladega

[[Page 31116]]

Counties), Lower Big Canoe Creek (St. Clair County), and Terrapin Creek 
(Cherokee County) in Alabama; and the Coosa and Lower Etowah Rivers 
(Floyd County), the Oostanaula River (Floyd and Gordon Counties), the 
Coosawattee River (Gordon County), and the Conasauga River (Gordon, 
Whitfield, and Murray Counties) in Georgia (Goodrich 1922, pp. 19, 21; 
Johnson 2004, p. 116; FLMNH 2006).
    Snail surveys conducted within the historical range of the 
interrupted rocksnail (Bogan and Pierson 1993a, pp. 1-27; Williams and 
Hughes 1998, pp. 1-21) resulted in the collection of only a single live 
specimen from the Oostanaula River, Floyd County, Georgia, during 1997 
(Williams and Hughes 1998, p. 9). Intensive surveys of the Oostanaula, 
Coosa, Coosawattee, Etowah, and Conasauga Rivers since 1999 have 
located the species in about 12 km (7.5 mi) of the Oostanaula River 
upstream of the Gordon-Floyd County line (Johnson and Evans 2000, pp. 
45-46; Johnson and Evans 2001, pp. 2, 25). A captive colony was 
maintained at the Tennessee Aquarium Research Institute (TNARI) from 
2000 through 2005 for study and propagation. In coordination with TNARI 
and the Service, the Alabama Department of Conservation and Natural 
Resources (ADCNR) developed a plan and strategy to reintroduce 
interrupted rocksnails from the TNARI colony into the Coosa River above 
Wetumpka, Elmore County, Alabama (ADCNR 2003, pp. 1-4). In 2003, 2004, 
and 2005, approximately 3,200, 1,200, and 3,000 juvenile snails, 
respectively, from the TNARI culture were released into the Lower Coosa 
River (ADCNR 2004, p. 33; P. Johnson in litt. 2005a). In 2005, ADCNR 
established the Alabama Aquatic Biodiversity Center (AABC) at the 
Marion State Fish Hatchery for the culture of imperiled mollusk 
species, and the interrupted rocksnail TNARI colony was transferred to 
that facility.
    Following its rediscovery, the interrupted rocksnail population 
size on shoals in the Oostanaula River declined from a high of 10 to 45 
snails per square meter (m\2\) (1.2 square yards (yd\2\) in 1999 
(Johnson and Evans 2001, p. 22) to only 20 snails found during 6 
search-hours in 2004 (P. Johnson in litt. 2003, 2004). The cause of 
decline was suspected to be some form of water contamination (P. 
Johnson in litt. 2003, 2004; P. Hartfield in litt. 2006). A July 2006 
search for adults to use as hatchery stock failed to locate any 
rocksnails in more than 2 search-hours (P. Hartfield in litt. 2006). 
However, a subsequent search in August 2006 under lower flow conditions 
resulted in the location of 89 snails in 4 search-hours at one shoal, 
and 2 rocksnails in 4 search-hours at another shoal (P. Johnson in 
litt. 2007a).
    Since their reintroduction into the Lower Coosa River of Alabama, a 
few of the 2003 hatchery-cultured interrupted rocksnails were observed 
in the vicinity of the release site in 2004 (Johnson in litt. 2005c). 
An alternative site was selected for release in August 2005, and 18 
snails were located 3 months following release (M. Pierson in litt. 
2005). During a 40-minute search of this release area in 2006, two 
interrupted rocksnails were found (P. Johnson in litt. 2007b). 
Observations of only small numbers of reintroduced snails may be due to 
habitat size and dispersal, low fecundity of the species, predation, 
reproductive failure due to dispersal, or habitat disturbance (Johnson 
in litt. 2005b).
Rough Hornsnail
    The rough hornsnail's (Pleurocera foremani) shell is elongated, 
pyramidal, and thick. Growing to about 33 mm (1.3 in) in length, the 
shell has as many as nine yellowish-brown whorls. The aperture is 
elongated, angular, channeled at the base, and usually white inside. 
The presence of prominent nodules or tubercles on the lower whorls 
above the aperture is the most distinctive feature that separates it 
from other hornsnails (Tryon 1873, p. 53). These tubercles, along with 
the size and shape of the shell, distinguish the species from all other 
pleurocerid snails (Elimia spp., Leptoxis spp., Pleurocera spp.) in the 
Mobile River Basin.
    The rough hornsnail is a member of the aquatic snail family of 
Pleuroceridae. The species was described in 1843 by Lea as Melania 
foremanii (=foremani) (Tryon 1873, p. 52). It was later placed in the 
genus Pleurocera by Tryon (1873, p. 52), who noted that P. foremani 
closely resembled species of that genus. Goodrich (1935, p. 3) reported 
a variation of a species of Pleurocera in the Cahaba River that 
resembled foremani, but later identified that variant as a ``mutation'' 
or form of brook hornsnail (P. vestitum) (Goodrich 1941, p. 12). This 
variant, however, is no longer extant in the Cahaba River (Bogan and 
Pierson 1993b, p. 12; Sides 2005, pp. 21-22, 28). Goodrich (1944, p. 
43) considered that the Coosa River P. foremani might also be 
eventually found to be simply a variant of smooth hornsnail (P. 
prasinatum), another more widely distributed species in the Coosa 
River.
    In a recent dissertation on the systematics of the Mobile River 
Basin Pleurocera, the rough hornsnail was found to be both 
morphologically and genetically distinct from other species in the 
genus (Sides 2005, pp. 26, 127). This analysis also found that the 
rough hornsnail was genetically more closely allied to a co-occurring 
species in the genus Elimia, and concluded that it should be recognized 
as Elimia foremani (Sides 2005, pp. 26-27). Although the Sides (2005, 
pp. 26-27) study provides some evidence that this species should be 
placed in the genus Elimia, this taxonomic change has not been formally 
peer-reviewed and published. Therefore, for the purposes of this 
action, we will continue to use currently recognized nomenclature for 
the rough hornsnail (Pleurocera foremani).
    Rough hornsnails are primarily found on gravel, cobble, and bedrock 
in moderate currents. They have been collected at depths of 1 m (3.3 
ft) to 3 m (9.8 ft) (Hartfield 2004, p. 132). The species appears to 
tolerate low-to-moderate levels of silt deposition (Sides 2005, p. 
127). Little is known regarding the life history characteristics of 
this species. Snails in the genus Pleurocera generally lay their eggs 
in a spiral arrangement on smooth surfaces (Sides 2005, pp. 26-27), 
whereas Elimia snails generally lay eggs in short strings (P. Johnson 
2006). Attempts to induce rough hornsnails to lay eggs in captivity 
have been unsuccessful (Sides 2005, p. 27).
    The rough hornsnail is endemic to the Coosa River system in 
Alabama. Goodrich (1944, p. 43) described the historical range as the 
Coosa River downstream of the Etowah River and at the mouths of a few 
tributaries. The Etowah River enters the Coosa River in Floyd County, 
Georgia; however, there are no known museum or site-specific records of 
the rough hornsnail that validate its range into the State of Georgia 
(P. Johnson in litt. 2006a). Historical museum records of the rough 
hornsnail in the Coosa River (FLMNH 2006, and elsewhere) indicate that 
they occurred from Etowah, St. Clair, Shelby, Talladega, and Elmore 
Counties, Alabama, a historical range of approximately 322 river km 
(200 river mi). There are also historical museum records of this 
species from nine Coosa River tributaries in Alabama, including Big 
Wills Creek in Etowah County; Kelly, Big Canoe, and Beaver Creeks in 
St. Clair County; Ohatchee Creek, Calhoun County; Choccolocco and 
Peckerwood Creeks in Talladega County; Yellowleaf Creek, Shelby County; 
and Yellow Leaf Creek in Chilton County (FLMNH 2006).
    The rough hornsnail is currently known to occur at two locations: 
Lower

[[Page 31117]]

Yellowleaf Creek in Shelby County, Alabama; and the Lower Coosa River 
below Wetumpka Shoals in Elmore County, Alabama (Sides 2005, p. 40). 
There are also museum records of the species from Wetumka Shoals in the 
early 1990s (FLMNH 2006); however, the species has not been collected 
from the shoal reach in recent surveys (Johnson 2002, pp. 5-9). 
Yellowleaf Creek is a moderately sized stream where rough hornsnails 
have been collected from about a 50-m (55-yd) length of the stream. At 
this location, rough hornsnails occur at densities of 8 to 32 m\2\ (1.2 
yd\2\) (Pierson in litt. 2006). The Lower Coosa River is a large river 
channel where rough hornsnails have been found in an area of about 100 
m\2\ (120 yd\2\) (P. Hartfield 2001). No quantitative estimates have 
been made at this site. Searches of unimpounded reaches of the Coosa 
River and the lower portions of tributaries to the Coosa have failed to 
locate the species elsewhere (Bogan and Pierson 1993a, pp. 1-27; 
Garner, pers. com. 2005; Hartfield in litt. 2006). The two known 
surviving populations are separated by three impoundments and about 113 
km (70 mi) of impounded channel habitat.

Previous Federal Action

    The interrupted rocksnail and rough hornsnail were first identified 
as candidates for protection under the Act in the November 21, 1991, 
Federal Register (56 FR 58804). They were assigned a category 2 status 
designation, which was given to those species for which there was some 
evidence of vulnerability, but for which additional biological 
information was needed to support a proposed rule to list as endangered 
or threatened. In the November 15, 1994, notice of candidate review (59 
FR 58982), the rough hornsnail was again assigned a category 2 status, 
while the status category for the interrupted rocksnail (Leptoxis 
foremani) was changed to 3A (taxa for which the Service has persuasive 
evidence of extinction).
    Assigning categories to candidate species was discontinued in 1996 
(Notice of Candidate Review; February 28, 1996; 61 FR 7596), and only 
species for which the Service has sufficient information on biological 
vulnerability and threats to support issuance of a proposed rule are 
now regarded as candidate species. Candidate species were also assigned 
listing priority numbers based on immediacy and the magnitude of 
threat, as well as their taxonomic status (48 FR 43098; Sept. 21, 
1983). Due to a need for taxonomic clarification, the rough hornsnail 
was dropped as a candidate species in 1996.
    In 1997, we received reports of a small population of the 
interrupted rocksnail surviving in the Ostanaula River, Georgia, along 
with reports of Georgia pigtoe collections in the Conasauga River of 
Georgia and Tennessee, and their status as candidates was reevaluated. 
In the 1999 (64 FR 57533), 2001 (66 FR 54808), 2002 (67 FR 40657), and 
2004 (69 FR 24876) Federal Register notices of candidate review, both 
the Georgia pigtoe and interrupted rocksnail (as Georgia rocksnail, 
Leptoxis downei) were identified as listing priority 5 candidate 
species. In the May 11, 2005, Federal Register notice of candidate 
review (70 FR 24870) the nomenclature was corrected for the interrupted 
rocksnail, and the listing priority for both species was changed from 5 
to 2, based on the continued rarity of the Georgia pigtoe and a decline 
in abundance of the interrupted rocksnail. The rough hornsnail was 
recognized as a listing priority 2 candidate in the September 12, 2006, 
Federal Register notice of candidate review (71 FR 53756), following 
clarification of its taxonomy, along with the interrupted rocksnail and 
Georgia pigtoe.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1533), and implementing regulations 
at 50 CFR part 424, set forth procedures for adding species to the 
Federal Lists of Endangered and Threatened Wildlife and Plants. Under 
section 4(a) of the Act, we may list a species on the basis of any of 
five factors, as follows: (A) The present or threatened destruction, 
modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; or (E) other natural or manmade factors 
affecting its continued existence. In making this finding, information 
regarding the status and trends of the Georgia pigtoe, interrupted 
rocksnail, and rough hornsnail are considered in relation to the five 
factors provided in section 4(a)(1) of the Act.
    Under section 3 of the Act, a species is ``endangered'' if it is in 
danger of extinction throughout all or a significant portion of its 
range and is ``threatened'' if it is likely to become endangered within 
the foreseeable future throughout all or a significant portion of its 
range. The word ``range'' refers to the range in which the species 
currently exists. Range is discussed further below in the Conclusion 
section of this proposed rule.
    Foreseeable future is determined by the Service on a case-by-case 
basis, taking into consideration a variety of species-specific factors 
such as lifespan, genetics, breeding behavior, demography, threat 
projection timeframes, and environmental variability.
    The average lifespan of the interrupted rocksnail in the wild is 
unknown; however, interrupted rocksnails have survived in captivity for 
as long as 5 years (Johnson in litt. 2006b). Heavy-shelled mussels are 
known to have long life spans, with many species living from 30 to 70 
years (Williams et al. 2008, p. 68). For the purposes of this analysis, 
we estimate a life span of 30 years for the Georgia pigtoe.
    Some percentage of rocksnails cultured in captivity have been 
observed ovipositing in their first year, but all are believed to 
become sexually mature in their second year. Less is known about the 
rough hornsnail; however, some pleurocerid snails in the genus Elimia 
may live up to 5 years (Dillon 1988, p. 113). It is also believed that 
most pleurocerid snails may begin reproducing within 1 year post-hatch, 
depending upon habitat and productivity (Johnson 2008).
    The age of sexual maturity for the Georgia pigtoe is unknown and 
varies widely among the genera of freshwater mussels. In general, thin-
shelled species reach sexual maturity earlier and have shorter 
lifespans than heavier-shelled species. In the Mobile River Basin, age 
at sexual maturity for mussels has been shown to vary from 1 to 2 years 
for the thin-shelled southern pocketbook (Lampsilis ornata), and 3 to 9 
years for the heavy-shelled Alabama orb (Quadrula asperata) (Haag and 
Staton 2003, pp. 2122-2123). The Georgia pigtoe is similar in shell 
size and thickness to the Alabama orb, so we are estimating sexual 
maturity for the Georgia pigtoe at age 5 years, and a generational time 
span of 5 years. Heavy-shelled mussels are also known to have long life 
spans, with many species living from 30 to 70 years (Williams et al. 
2008, p. 68).
    Threat projection timeframes for the Georgia pigtoe, interrupted 
rocksnail, and rough hornsnail include specific activities that can 
arise at any time (such as permitted discharges, construction 
activities, channel modifications, or random accidents and spills of 
toxic substances) and periodic weather events (such as droughts and 
floods).
    The following analysis examines all five factors currently 
affecting or that are likely to affect Georgia pigtoe,

[[Page 31118]]

interrupted rocksnail, and rough hornsnail snail. The five factors 
listed under section 4(a)(1) of the Act and their application to the 
Georgia pigtoe mussel (Pleurobema hanleyianum (Lea 1852)), interrupted 
rocksnail (Leptoxis foremani (Lea 1843)), and rough hornsnail 
(Pleurocera foremani (Lea 1843)) are as follows:

A. The present or threatened destruction, modification, or curtailment 
of its habitat or range.

    All three species have experienced significant curtailment of their 
occupied habitats (see ``Background'' above). The Georgia pigtoe has 
been eliminated from about 90 percent of its historical range of 480 
river km (298 river mi). It now inhabits only 43 river km (27 river 
mi). Interrupted rocksnail has been eliminated from 99 percent of a 
historical range of 800 river km (497 river mi), and is now known from 
12 river km (7 river mi). The rough hornsnail has disappeared from more 
than 99 percent of a historical range of 321 river km (199 river mi) 
and now occurs in less than 1 river km (0.6 river mi). The primary 
cause of range curtailment for all three species has been modification 
and destruction of river and stream habitats, primarily by the 
construction of large hydropower dams on the Coosa River. This was 
compounded by fragmentation and isolation of the remaining free-flowing 
portions of the Coosa River and its tributaries, as well as their 
increased vulnerability to local historical events of water quality and 
habitat degradation.
Dams and Impoundments
    Dams eliminate or reduce river flow within impounded areas, trap 
silts and cause sediment deposition, alter water temperature and 
dissolved oxygen levels, change downstream water flow and quality, 
affect normal flood patterns, and block upstream and downstream 
movement of species (Watters 1999, pp. 261-264; McAllister et al. 2000, 
p. iii; Marcinek et al. 2005, pp. 20-21). Within impounded waters, 
decline of freshwater mollusks has been attributed to sedimentation, 
decreased dissolved oxygen, and alteration in resident fish populations 
(Neves et al. 1997, pp. 63-64; Watters 1999, pp. 261-264; Marcinek et 
al. 2005, pp. 9-10). Below dams, mollusk declines are associated with 
changes and fluctuation in flow regime, scouring and erosion, reduced 
dissolved oxygen levels and water temperatures, and changes in resident 
fish assemblages (Williams et al. 1992b, p. 7; Neves et al. 1997, pp. 
63-64; Watters 1999, pp. 261-264; Marcinek et al. 2005, pp. 20-21). The 
decline and extinction of freshwater snails and mussels in the Mobile 
River Basin has been directly attributed to construction of numerous 
large impoundments in the major river systems (Williams et al. 1992b, 
pp. 1-8; Bogan et al. 1995, pp. 250-251; Lydeard and Mayden 1995, pp. 
803-804; Neves et al. 1997, pp. 62, 64; Marcinek et al. 2005, p. 9).
    The Georgia pigtoe, interrupted rocksnail, and rough hornsnail are 
all endemic to the Coosa River system. The Coosa River was impounded by 
six major dams constructed between 1928 and 1966. Today, more than 60 
percent of the Coosa River and its 19 largest tributaries are inundated 
or affected by flow regulation (Marcinek et al. 2005, pp. 12-16).
    Dam construction on the Coosa River had a secondary effect of 
fragmenting the ranges of aquatic mollusk species, leaving relict 
habitats and populations isolated by the structures as well as by 
extensive areas of uninhabitable, impounded waters. These isolated 
populations were left more vulnerable to, and affected by, natural 
events (such as droughts), runoff from common land-use practices (such 
as agriculture, mining, urbanization), discharges (such as municipal 
and industrial wastes), and accidents (such as chemical spills) that 
reduced population levels or eliminated habitat (Neves et al. 1997, pp. 
64-71; U.S. Fish and Wildlife Service 2000, pp. 14-15). As a result, 
many relict populations became locally extirpated, and many mollusk 
species were driven to extinction (Bogan et al. 1995, pp. 250-251; 
Lydeard and Mayden 1995, pp. 803-804; Neves et al. 1997, pp. 54, 62; 
U.S. Fish and Wildlife Service 2000, pp. 6-9). If conditions 
subsequently improved, the surviving mollusk species were unable to 
naturally recolonize suitable areas, due to impediments created by the 
dams and impounded waters.
    The only known natural population of the interrupted rocksnail 
occurs in the free-flowing Oostanaula River (Williams and Hughes 1998, 
p. 9; Johnson and Evans 2001, p. 25). The Oostanaula River is formed by 
the confluence of the Conasauga and Coosawatee Rivers. The Upper 
Coosawatee is impounded by Carters Dam, a hydropower dam which 
discharges into Carters Re-regulation Dam and from there into the 
Coosawatee River. Hydropower discharges from Carters Dam are believed 
to be implicated in the disappearance of the interrupted rocksnail from 
the Coosawattee River (Johnson and Evans 2001, p. 26). The effects of 
power generation discharges from Carters Dam, along with cold water 
temperatures are evident downstream (Williams and Hughes 1998, p. 11), 
even to the shoals on the Oostanaula River where the interrupted 
rocksnail is found (Johnson and Evans 2001, p. 26; Marcinek et al. 
2005, p. 15). A Federal Energy Regulatory Commission (FERC) license was 
issued to construct a hydroelectric facility on the Carters Re-
regulation Dam (FERC 2001, pp. 1-2). A notice of probable termination 
of license has been issued due to failure to commence construction in a 
timely manner (FERC 2005a, pp. 1-2). An appeal to the termination order 
was made (FERC 2005b, p. 1) but denied (FERC 2006a, pp. 1-3). However, 
the applicant has since applied for a preliminary permit to proceed 
with the hydroelectric facility (FERC 2006b, pp. 1-3).
    Rough hornsnails currently survive in Lower Yellowleaf Creek, at 
the transitional area between the flowing stream and the embayment 
created by Lay Dam, and in a small area of the Coosa River below the 
shoals along the Fall Line near Wetumpka, Alabama. Known from the main 
channel of the Coosa River and the mouths of some of the larger 
tributaries, all historical habitats, including those two where the 
rough hornsnail currently survives, are affected to some degree by 
impounded waters and hydropower releases.
    The Georgia pigtoe historically occurred in the Coosa River and 
many of its major tributaries. As noted above, the Coosa is impounded 
throughout most of its length by major hydropower dams. In addition, 
all historically occupied tributaries are isolated from each other by 
one or more of these dams and extensive reaches of impounded waters. 
The species is currently known to survive only in the Upper Conasauga 
River, far above the influence of the Coosa River impoundments.
Water and Habitat Quality
    The disappearance of shoal populations of rough hornsnail, 
interrupted rocksnail, and Georgia pigtoe from unimpounded relict 
habitats in the Coosa River drainage is likely due to historical 
pollution problems. Pleurocerid snails and freshwater mussels are 
highly sensitive to water and habitat quality (Havlik and Marking 1987, 
pp 1-15; Neves et al. 1997, pp. 64-69). Historical causes of water and 
habitat degradation in the Coosa River and its tributaries included 
drainage from gold mining activities, industrial and municipal 
pollution events, and construction and agricultural runoff (for 
example, Hurd 1974, pp. 38-40; Lydeard and Mayden 1995, pp. 803-804; 
Freeman et al. 2005, pp. 560-562).

[[Page 31119]]

    Prior to the passage of the Federal Clean Water Act (33 U.S.C. 1251 
et seq., 1972) and the adoption of State water quality regulations and 
criteria, water pollution was a significant factor in the disappearance 
of mollusks from unimpounded river and stream channels in the Mobile 
River Basin (Baldwin 1973, p. 23; Hurd 1974, pp. 38-40, 144-151). Hurd 
(1974, pp. 147-149), for example, noted the extirpation of freshwater 
mussel communities from the Conasauga River below Dalton, Georgia, 
apparently as a result of textile and carpet mill waste discharges. He 
also attributed the disappearance of the mussel fauna from the Etowah 
River and other tributaries of the Coosa River to organic pollution and 
siltation. Baldwin (1973, p. 23) documented the loss of mussel 
diversity in the Cahaba River and identified the primary causes as 
pollution from coalfields and industrial and urban wastes.
    Although Federal and State water quality laws and regulations have 
generally reduced the impacts of point source discharges, nonpoint 
source pollution continues to affect and possibly threaten the 
remaining populations of each of these mollusk species. Nonpoint source 
pollution has been identified as a concern in the Yellowleaf Creek and 
Lower Coosa River watersheds (Alabama Clean Water Partnership (ACWP) 
2005 Chapter 12). These drainages encompass historical habitat for the 
interrupted rocksnail and Georgia pigtoe, currently occupied habitat 
for the rough hornsnail, and a recent reintroduction of the interrupted 
rocksnail. Both Yellowleaf Creek and the eastern watershed of the Lower 
Coosa River have been designated as High Priority Watersheds by the 
ACWP (2005 Chap. 12), due to the high potential of nonpoint source 
pollution associated with expanding human population growth rates and 
urbanization. The headwaters of Yellowleaf Creek are about 5 km (3 mi) 
southeast of the greater metropolitan area surrounding Birmingham, and 
the watershed is highly dissected by county roads. The Lower Coosa 
River is about 16 km (10 mi) north of the Montgomery greater 
metropolitan area and is accessible by a four-lane highway. Both 
general areas are experiencing growth due to their proximity to major 
metropolitan areas.
    Nonpoint source pollution and habitat deterioration are also 
problems in the Upper Coosa River Basin, including the Conasauga and 
Oostanaula rivers (Georgia Department of Natural Resources (GDNR) 1998, 
pp. 4.27-4.42). In the reaches of the Conasauga River where the Georgia 
pigtoe continues to survive, overall molluscan abundance and diversity 
have experienced a general decline over the past two decades that has 
been primarily attributed to water or sediment toxicity and channel 
instability (Johnson and Evans 2000, pp. 171-173; Sharpe and Nichols 
2005, pp. 81-88). Sedimentation has been identified as a potential 
limiting factor for the interrupted rocksnails in the Oostanaula River 
(Johnson and Evans 2001, p. 26). Following its rediscovery, the 
interrupted rocksnail population size in the Oostanaula River has 
declined from a high of 10 to 45 snails per square meter (10.7 sq ft) 
in 1999 (Johnson and Evans 2001, p. 22) to only 20 snails found during 
6 search-hours in 2004 (P. Johnson in litt. 2003, 2004). The cause of 
decline is suspected to be some form of water contamination (P. Johnson 
in litt. 2003, 2004; P. Hartfield in litt. 2006).
    Nonpoint source pollution from land surface runoff originates from 
virtually all land use activities and includes sediments; fertilizer, 
herbicide, and pesticide residues; animal or human wastes; septic tank 
leakage and gray water discharge; and oils and greases (GDNR 1998, pp. 
4.27-4.42; ACWP 2005, Chap. 9). Nonpoint source pollution can cause 
excess sedimentation, nutrification, decreased dissolved oxygen 
concentration, increased acidity and conductivity, and other changes in 
water chemistry that can seriously impact aquatic mollusks. Land use 
types around the Georgia pigtoe, interrupted rocksnail, and rough 
hornsnail populations include pastures, row crops, timber, and urban 
and rural communities.
    Excessive sediments are believed to impact riverine mollusks 
requiring clean, stable streams (Ellis 1936, pp. 39-40; Brim Box and 
Mossa 1999, p. 99). Impacts resulting from sediments have been noted 
for many components of aquatic communities. For example, sediments have 
been shown to abrade or suffocate periphyton (organisms attached to 
underwater surfaces, upon which snails may feed); affect respiration, 
growth, reproductive success, and behavior of aquatic insects and 
mussels; and affect fish growth, survival, and reproduction (Waters 
1995, pp. 173-175). Potential sediment sources within a watershed 
include virtually all activities that disturb the land surface, and all 
localities currently occupied by these mollusks are affected to varying 
degrees by sedimentation.
    Land surface runoff also contributes nutrients to rivers and 
streams. Excessive nutrient input (for example, nitrogen and phosphorus 
from fertilizers, sewage, and animal manure) can result in effects that 
are detrimental to aquatic species. High levels of nutrients in surface 
runoff can promote excessive filamentous algal growth. Dense algal 
growth covers gravel, cobble, or bedrock substrates and interstices 
(spaces between bottom particles), and can seriously reduce dissolved 
oxygen in waters during dark hours due to algal respiration (Shepard et 
al. 1994, pp. 61-64), which affects feeding, reproduction, and 
respiration in adult and juvenile mussels and snails, and limits access 
to substrate interstices important to juvenile and adult mussels. Algal 
mats also provide cover for invertebrate predators of juvenile mollusks 
(such as flatworms, hydra, and chironomids) and increase their 
vulnerability to such predators. Filamentous algae may also displace 
certain species of fish, or otherwise affect fish-mussel interactions 
essential to recruitment (for example, Hartfield and Hartfield 1996, p. 
373). In hatcheries, filamentous algal growth reduces juvenile mussel 
survival by reducing flow, increasing sedimentation, and causing 
competition with and reduction of the unicellular algal community on 
which the mussels feed (R. Neves 2002). Nutrient and sediment pollution 
may have synergistic effects (when the toxic effect of two or more 
pollutants operating together is greater than the sum of the effects of 
the pollutants operating individually) on freshwater mollusks, as has 
been suggested for aquatic insects (Waters 1995, p. 67).
    Land surface runoff contributes the majority of human-induced 
sediments and nutrients to water bodies throughout the United States. 
The human population is expanding within the areas currently occupied 
by the Georgia pigtoe, interrupted rocksnail, and rough hornsnail, 
increasing the sediment and nutrient input to their riverine habitats, 
and leaving these mollusks vulnerable to progressive water and habitat 
degradation from land surface runoff.
    Accidental spills that may affect water or habitat quality also 
threaten surviving populations of each species. For example, on 
September 12, 2006, a train derailment spilled four tank cars of 
soybeans into a tributary of Yellowleaf Creek (Birmingham News in litt. 
2006). A large rain event flushed the decomposing soybeans into 
Yellowleaf Creek, resulting in a serious decline in dissolved oxygen in 
the stream, killing fishes, mussels (including two endangered species, 
southern pigtoe and triangular kidneyshell), and snails (including the 
endangered cylindrical

[[Page 31120]]

lioplax) (Johnson 2006). Fortunately, the location of the largest 
surviving population of rough hornsnail is in the lowest reaches of 
Yellowleaf Creek, remote from the spill, and no mortality was observed 
in this population as a result of the spill (Johnson 2006).
    In summary, the historical loss of habitat and range is currently, 
and projected to continue to be, a significant threat to the rough 
hornsnail, interrupted rocksnail, and Georgia pigtoe. Curtailment of 
habitat and range also amplifies threats from nonpoint source water and 
habitat quality degradation, accidental spills, or violation of 
permitted discharges. Due to the extremely limited extent of habitat 
currently occupied by each species, and the severity and magnitude of 
this threat, we have determined that the present or threatened 
destruction, modification, or curtailment of habitat and range 
represents an ongoing and significant threat to the rough hornsnail, 
interrupted rocksnail, and Georgia pigtoe.

B. Overutilization for commercial, recreational, scientific, or 
educational purposes.

    The Georgia pigtoe, interrupted rocksnail, and rough hornsnail are 
not commercially utilized. Each species has been taken for scientific 
and private collections in the past, yet collecting is not considered a 
factor in the decline of these species. While collection is not 
considered a current threat, the desirability of these species in 
scientific and commercial collections may increase as their existence 
and rarity becomes known, and their localized distributions and small 
population sizes leaves them vulnerable to overzealous recreational or 
scientific collecting.

C. Disease or predation.

    Diseases of freshwater mollusks are poorly known and are not 
currently considered to be a threat to the Georgia pigtoe, interrupted 
rocksnail, and rough hornsnail, or a factor in their decline. Aquatic 
snails and mussels are consumed by various vertebrate predators, 
including fishes, mammals, and possibly birds. Although predation by 
naturally occurring predators is a normal aspect of the population 
dynamics of a species and is not known to be a threat to any of these 
species, changes in water flows, depths, temperatures, and other 
environmental factors within some portions of their ranges may have led 
to increased numbers of native mollusk-eating fish, such as freshwater 
drum (Johnson in litt. 2005b). In addition, the potential now exists 
for the black carp (Mylopharyngodon piceus), a mollusk-eating Asian 
fish recently introduced into the waters of the United States (U.S. 
Fish and Wildlife Service 2002), 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.
    In summary, disease in freshwater mollusks is poorly known and not 
currently considered a threat. Although there is no direct evidence at 
this time that predation is detrimentally affecting the Georgia pigtoe, 
interrupted rocksnail, or rough hornsnail, their small populations and 
limited ranges leaves them vulnerable to threats of predation from 
natural or introduced predators. Therefore, we have concluded that 
predation currently represents a threat of low magnitude, but it could 
potentially become a significant future threat to the Georgia pigtoe, 
interrupted rocksnail, or rough hornsnail due to their small population 
sizes.

D. The inadequacy of existing regulatory mechanisms.

    The Alabama Department of Conservation and Natural Resources 
currently recognizes the rough hornsnail as a ``Priority 1'' species 
(Highest Conservation Concern) (Mirarchi et al. 2004, p. 117; ADCNR 
2005, p. 302). The interrupted rocksnail is considered ``Extirpated (in 
Alabama) - Conservation Action Underway'' (Mirarchi et al. 2004, p. 
114), and the Georgia pigtoe is listed as ``extinct'' (Mirarchi et al. 
2004, p. 13). While these classifications identify the status of 
imperiled species in the State of Alabama, they convey no legal 
protection. Interrupted rocksnail and Georgia pigtoe currently lack any 
official status recognition by the State of Georgia, but they have been 
nominated for inclusion on the State Protected Species List. The 
Georgia pigtoe is identified as a species of the Greatest Conservation 
Need by the State of Tennessee. NatureServe (2006) identifies the 
Georgia pigtoe, interrupted rocksnail, and rough hornsnail as G1 
critically imperiled species; however, no State or Federal protection 
is conveyed by these classifications. Without State or Federal 
protection, these three species are not currently given any specific 
special consideration under environmental laws when project impacts are 
reviewed, other than those provided for water quality.
    The mollusk fauna (including the Georgia pigtoe) of the Conasauga 
River and the interrupted rocksnail in the Oostanaula River have 
experienced significant declines in recent years, apparently due to 
water quality or sediment toxicity (Evans 2001, p. 3; Johnson in litt. 
2004; Sharpe and Nichols 2005, pp. 1-4; Konwick et al. 2008, pp. 2016-
2017). There is no specific scientific information on the sensitivity 
of the Georgia pigtoe, interrupted rocksnail, and rough hornsnail or 
their host fish species to common industrial and municipal pollutants, 
and little information on other freshwater mollusks. Current State and 
Federal regulations regarding pollutants are assumed to be protective 
of freshwater mollusks; however, these species may be more susceptible 
to some pollutants than test organisms commonly used in bioassays. For 
example, several recent studies have suggested that U.S. Environmental 
Protection Agency's (EPA) criteria for ammonia may not be protective of 
freshwater mussels (Augspurger et al. 2003, p. 2571; Augspurger et al. 
2007, p. 2026; Newton et al. 2003, pp. 2559-2560; Newton and Bartsch 
2007, p 2057; Ward et al. 2007, p. 2075).
    In a review of the effects of eutrophication on mussels, Patzner 
and Muller (2001, p. 329) noted that stenoecious (narrowly tolerant) 
species disappear as waters become more eutrophic. They also refer to 
studies that associate increased levels of nitrate with the decline and 
absence of juvenile mussels (Patzner and Muller 2001, pp. 330-333). 
Other studies have also suggested that early life stages of mussels are 
more sensitive to metals and such inorganic chemicals as chlorine and 
ammonia than are common bioassay test organisms (Keller and Zam 1991, 
pp. 543-545; Goudreau et al. 1993, p. 221; Naimo 1995, pp. 354-355). 
Therefore, it appears that inadequate research and data prevent 
existing regulations, such as the Clean Water Act (administered by the 
EPA and the U.S. Army Corps of Engineers), from being fully utilized or 
effective in the management and protection of these species.
    Rough hornsnails currently survive at localized sites in Yellowleaf 
Creek and in the Lower Coosa River below Wetumpka Shoals in Alabama. In 
addition, the interrupted rocksnail was recently reintroduced into 
Wetumpka Shoals. The Alabama Department of Environmental Management 
(ADEM) has designated the water use classification for some portions of 
Yellowleaf Creek as ``Swimming'' (S) and others as ``Fish and 
Wildlife'' (F&W). The F&W designation establishes minimum water quality 
standards that are believed to protect

[[Page 31121]]

existing species and water uses (for example, fishing, recreation, 
irrigation) within the designated area, while the S classification 
establishes higher water quality standards that are protective of human 
contact with the water. The Lower Coosa River below Wetumpka is 
currently designated as F&W by ADEM, and adjacent tributaries are 
classified as S. Both water bodies are currently believed to support 
their designated uses. However, Yellowleaf Creek and the eastern 
watershed of the Lower Coosa have been designated as High Priority 
Watersheds by the ACWP (2005, Chap. 12) due to a lack of monitoring 
data and the high potential of nonpoint source pollution in these 
drainages associated with expanding human population growth rates and 
urbanization.
    The reach of the Conasauga River at and below the Tennessee-Georgia 
State Line supports the only known surviving population of the Georgia 
pigtoe. This river reach is identified on Georgia's 303(d) list as 
partially supporting its designated use of Fishing-Drinking Water (GDNR 
2006, p. 35). The Georgia 303(d) list identifies high levels of fecal 
coliform bacteria and Fish Consumption Guidance (FCG) due to 
polychlorinated biphenyls (PCBs) as the reasons for this river reach's 
inclusion on the list, and nonpoint pollution is identified as the 
source of pollutants (GDNR 2006, p. 35). Recent studies have also 
implicated sediment and water toxicity in the decline of mollusks in 
the Conasauga River (Sharpe and Nichols 2005, pp. 81-88; Konwick et al. 
2008, pp. 2016-2017).
    States maintain water-use classifications through issuance of 
National Pollutant Discharge Elimination System (NPDES) permits to 
industries, municipalities, and others that set maximum limits on 
certain pollutants or pollutant parameters. For water bodies on the 
303(d) list, States are required under the Clean Water Act to establish 
a total maximum daily load (TMDL) for the pollutants of concern that 
will bring water quality into the applicable standard. The Georgia 
Department of Natural Resources has identified TMDLs for the Oostanaula 
River to address existing problems of PCBs and fecal coliform loads 
from nonpoint source and urban runoff sources.
    In summary, recent declines in mollusk communities within the 
ranges of each of these species has been attributed to poor water or 
sediment quality. Although regulatory mechanisms are in place to 
protect aquatic species, a lack of specific information on the 
sensitivity of the Georgia pigtoe, interrupted rocksnail, and rough 
hornsnail and their host fish to common industrial and municipal 
pollutants limits their application. Water and sediment quality is 
believed to currently affect (and is expected to continue to affect) 
the Georgia pigtoe and interrupted rocksnail and has been identified as 
a concern for the rough hornsnail in Yellowleaf Creek. Therefore, we 
have determined that the threat of inadequate existing regulatory 
mechanisms is an imminent threat of high magnitude to the Georgia 
pigtoe, interrupted rocksnail, and rough hornsnail.

E. Other natural or manmade factors affecting its continued existence.

    As noted under Factor A, above, the Georgia pigtoe, interrupted 
rocksnail, and rough hornsnail have been eliminated from 90 percent or 
more of their historical ranges. Surviving populations of each species 
are small, extremely localized, isolated, and vulnerable to habitat 
modification, toxic spills, and progressive degradation from land 
surface runoff (non-point source runoff) (see Factor A: Dams and 
Impoundments, Water and Habitat Quality; and Factor D: The inadequacy 
of existing regulatory mechanisms). These conditions also leave each 
species vulnerable to catastrophic changes to their habitats that may 
result from natural events such as flood scour and drought.
    There is a growing concern that climate change may lead to 
increased frequency of severe storms and droughts (for example, 
Golladay et al. 2004, p. 504; McLaughlin et al. 2002, p. 6074; Cook et 
al. 2004, p. 1015). During 2007-2008, 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 (U.S. Geological Survey 
2007). Although the effects of the drought on the Georgia pigtoe, 
interrupted rocksnail, and rough hornsnail have not been quantified, 
mollusk declines as a direct result of drought have been documented 
(for example, Golladay et al. 2004, p. 494; Haag and Warren 2008, p. 
1165). Reduction in local water supplies due to drought is also 
compounded by increased human demand and competition for surface and 
ground water resources for power production, irrigation, and 
consumption (Golladay et al. 2004, p. 504).
    Freshwater mussels and snails are capable of moving only short 
distances. As noted previously (see discussion under Factor A: Dams and 
Impoundments), there are numerous obstacles in the Coosa River drainage 
to long distance movement of snails, mussels, or the fish hosts of 
mussels, between relict patches of historically occupied and 
potentially suitable riverine habitats. Therefore, even if habitat 
conditions improve for the survival of the Georgia pigtoe, interrupted 
rocksnail, and rough hornsnail in historically occupied stream and 
river habitats, they will be unable to recolonize those areas without 
human assistance. Low numbers of individuals within these isolated 
populations also increases the risks and consequences of inbreeding and 
reduced genetic diversity (Lynch 1996, pp. 493-494).
    The Georgia pigtoe may be adversely affected by the loss or 
reduction in numbers of the fish host(s) essential to its parasitic 
glochidial stages. The specific fish host(s) for the glochidia of the 
Georgia pigtoe is unknown; therefore, specific impacts on this aspect 
of the mussels' life cycle cannot be evaluated. However, other species 
of mussels in the genus Pleurobema are known to parasitize various 
species of chubs, minnows, stonerollers, and other stream fish species.
    In summary, a variety of natural or manmade factors, such as 
droughts, storms, and toxic spills, threaten surviving populations of 
the Georgia pigtoe, interrupted rocksnail, and rough hornsnail due to 
the highly restricted and fragmented nature of their habitats and their 
small population sizes. Other factors, such as inbreeding, reduced 
genetic diversity, and loss or reduction of fish hosts for the Georgia 
pigtoe, may threaten each of the three species; however, the severity 
and magnitude of these threats are not currently known. Therefore, we 
have determined that other natural and manmade factors, such as 
accidental spills, floods, and droughts, currently pose an imminent and 
high degree of threat to the Georgia pigtoe, interrupted rocksnail, and 
rough hornsnail, and the levels of these threats are projected to 
continue or increase in the future.

Proposed Determination

    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the Georgia pigtoe, interrupted rocksnail, and rough hornsnail. 
Section 3(6) of the Act defines an endangered species as ``any species 
which is in danger of extinction throughout all or a significant 
portion of its range.'' Based on the severity and magnitude of the 
threats currently affecting each of these species, we

[[Page 31122]]

propose to list them as endangered species under the Act.
    The most significant historical factor affecting the current status 
of the interrupted rocksnail, rough hornsnail, and Georgia pigtoe was 
the extreme curtailment of their habitat and range, as discussed in 
Factor A (above). Curtailment of habitat and range, along with small 
population sizes, amplifies existing or impending threats from nonpoint 
source water and habitat quality degradation, accidental spills, 
violation of permitted discharges, inadequate knowledge to implement 
existing regulatory measures, floods, or droughts (described under 
Factors A, D, and E). These threats are imminent and high in magnitude 
(applicable to the entire range) for each species. As described in 
Factor C and E above, small populations are also at increased threat 
due to predation from natural or introduced predators, genetic 
isolation, and inbreeding depression; however, these threats are not 
currently known to be imminent.
    Only single, localized populations are known to exist of the 
interrupted rocksnail and Georgia pigtoe, and only two extremely 
localized populations of the rough hornsnail are known. Each species is 
faced with a tenuous future even with only the random variation of 
natural environmental factors. However, the additional threats of water 
and habitat quality degradation or destruction further threaten each 
species and this trend is expected to continue or increase.
    We believe that, when combining the effects of historical, current, 
and projected habitat loss and degradation, historical and ongoing 
drought, and the exacerbating effects of small population sizes and 
isolation, the interrupted rocksnail, rough hornsnail, and Georgia 
pigtoe are in danger of extinction throughout all of their ranges, as 
defined in the ``Summary of Factors Affecting the Species'' above. We 
believe these threats, particularly the threats resulting from habitat 
loss and fragmentation, small population sizes, and random natural or 
human induced events, are current and are projected to continue. We 
have determined that these threats are operating on each species and 
their respective habitats with a high degree of imminence, magnitude, 
and severity (rangewide), as discussed above.
    Based on the best available scientific and commercial information, 
we propose to list the Georgia pigtoe, interrupted rocksnail, and rough 
hornsnail as endangered species under the Act. Without the protection 
of the Act, these species are in danger of extinction throughout all of 
their ranges. This could occur within a few years, given recurring 
drought conditions, accidents, or other existing threats. Furthermore, 
because of their curtailed ranges, and immediate and ongoing 
significant threats to each species throughout their entire respective 
ranges, as described above in the five-factor analysis, we find that it 
is unnecessary to analyze whether there are any significant portions of 
ranges for each species that may warrant a different determination of 
status.
Critical Habitat
    Critical habitat is defined in section 3 of the Act as:
    (1) The specific areas within the geographical area occupied by a 
species, at the time it is listed in accordance with the Act, on which 
are found those physical or biological features
    (a) essential to the conservation of the species and
    (b) which may require special management considerations or 
protection; and
    (2) specific areas outside the geographical area occupied by a 
species at the time it is listed, upon a determination that such areas 
are essential for the conservation of the species.
    Conservation, as defined under section 3 of the Act, means to use 
and the use of all methods and procedures that are necessary to bring 
any endangered species or threatened species to the point at which 
measures provided under the Act are no longer necessary.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against Federal agencies carrying out, funding, 
or authorizing the destruction or adverse modification of critical 
habitat. Section 7(a)(2) of the