DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
RIN 1018-AI73

Endangered and Threatened Wildlife and Plants; Proposed Designation of Critical Habitat for Three Threatened Mussels and Eight Endangered Mussels in the Mobile River Basin

AGENCY:  Fish and Wildlife Service, Interior.

ACTION:  Proposed rule.

SUMMARY:  We, the U.S. Fish and Wildlife Service (Service), propose designation of critical habitat for three threatened (fine-lined pocketbook, orange-nacre mucket, and Alabama moccasinshell) and eight endangered freshwater mussels (Coosa moccasinshell, ovate clubshell, southern clubshell, dark pigtoe, southern pigtoe, triangular kidneyshell, southern acornshell, and upland combshell), listed in 1993 under the Endangered Species Act of 1973, as amended (Act). We propose to designate 26 river and stream segments (units) in the Mobile River Basin as critical habitat for these 11 mussel species. These units encompass a total of approximately 1,760 kilometers (km) (1,093 miles (mi)) of river and stream channels. Proposed critical habitat includes portions of the Tombigbee River drainage in Mississippi and Alabama; portions of the Black Warrior River drainage in Alabama; portions of the Alabama River drainage in Alabama; portions of the Cahaba River drainage in Alabama; portions of the Tallapoosa River drainage in Alabama and Georgia; and portions of the Coosa River drainage in Alabama, Georgia, and Tennessee.

Critical habitat identifies specific areas that are essential to the conservation of a listed species, and that may require special management considerations or protection. If this proposal is made final, section 7(a)(2) of the Act requires that Federal agencies ensure that actions they fund, authorize, or carry out are not likely to jeopardize the continued existence of an endangered or threatened species or result in the destruction or adverse modification of critical habitat. State or private actions, with no Federal involvement, are not affected.

Section 4 of the Act requires us to consider the economic and other relevant impacts of specifying any area as critical habitat. We hereby solicit data and comments from the public on all aspects of this proposal, including data on the economic and other impacts of the designation. We will conduct an analysis of the economic impacts of designating these areas as critical habitat prior to a final determination. That economic analysis will be conducted in a manner that is consistent with the ruling of the 10^th Circuit Court of Appeals in N.M. Cattle Growers Ass’n v. USFWS. When the draft economic analysis is completed, we will announce its availability with a notice in the Federal Register. With publication of the notice of availability, a comment period will be opened for a minimum of 30 days to allow for public comments on the draft economic analysis and proposed rule concurrently.

DATES:  We will consider comments received by June 24, 2003. We must receive requests for public hearings, in writing, at the address shown in the “ADDRESSES” section by May 12, 2003.

ADDRESSES:  If you wish to submit comments and information, you may submit your comments and information by any one of several methods:

1. You may submit written comments and information to the Field Supervisor, U.S. Fish and Wildlife Service, 6578 Dogwood View Parkway, Suite A, Jackson, MS 39213.
2. You may hand-deliver written comments and information to our Mississippi Fish and Wildlife Office, at the above address, or fax your comments to 601/965-4340.
3. You may send comments by electronic mail (e-mail) to paul_hartfield@fws.gov. For directions on how to submit electronic filing of comments, see the “Public Comments Solicited” section.

Comments and materials received, as well as supporting documentation used in the preparation of this proposed rule, will be available for public inspection, by appointment, during normal business hours at the above address.

FOR FURTHER INFORMATION CONTACT:  Paul Hartfield at the above address (telephone 601/321-1125, facsimile 601/965-4340).

SUPPLEMENTARY INFORMATION:

Background

This proposed rule addresses 11 bivalve mollusks or mussels (possessing a soft body enclosed by 2 shells) in the family Unionidae that are native to the Mobile River basin. The mussels addressed in this rule are the threatened fine-lined pocketbook (Lampsilis altilis), orange-nacre mucket (Lampsilis perovalis), and Alabama moccasinshell (Medionidus acutissimus), and the endangered Coosa moccasinshell (Medionidus parvulus), southern clubshell (Pleurobema decisum), dark pigtoe (Pleurobema furvum), southern pigtoe (Pleurobema georgianum), ovate clubshell (Pleurobema perovatum), triangular kidneyshell (Ptychobranchus greeni), upland combshell (Epioblasma metastriata), and southern acornshell (Epioblasma othcaloogensis). Unionid mussels, in general, live embedded in the bottom (sand, gravel, and/or cobble substrates) of rivers, streams, and other bodies of water. These mussels siphon water into their shells and across four gills that are specialized for respiration and food collection. Sexes in unionid mussels are usually separate. Males release sperm into the water; the sperm are then taken in by the females through their siphons during feeding and respiration. Eggs are held in the gills of the female where they come into contact with the sperm. Once eggs are fertilized, females retain them in their gills until the larvae (glochidia) fully develop. The change (metamorphosis) of the larvae of most unionid species into juvenile mussels requires that the larvae undergo a stage of parasitism on the fins, gills, or skin of a fish. Mature mussel glochidia are released into the water and they must find and attach to a suitable host fish species in order to develop into a juvenile mussel. Glochidia may be released separately or in masses termed conglutinates. The duration of the parasitic stage varies with water temperature, mussel species, and, perhaps, host fish species. Developed juvenile mussels normally detach from their fish host and sink to the stream bottom, where they continue to develop, provided they land in a suitable substrate with correct water conditions. Because of the dependence on this life stage and transport/dispersal process, unionid mussels usually only parasitize one or a few suitable host fish species that occupy similar habitats as the mussels. Consequently, the presence of suitable host fish species is considered an essential element in the life cycle of unionid mussels.

These 11 mussel species are historically native to portions of the Mobile River Basin (Basin). The Basin is composed of seven major river systems (Mobile, Tombigbee, Black Warrior, Alabama, Cahaba, Coosa, and Tallapoosa) and drains portions of the states of Alabama, Mississippi, Georgia, and Tennessee. Biological factors relevant to these freshwater mussels’ habitat requisites are discussed in the Primary Constituent Elements portion of this proposed rule.

Taxonomy, Life History, and Distribution

Fine-lined Pocketbook (Lampsilis altilis (Conrad 1834))

The fine-lined pocketbook is a medium-sized mussel, suboval in shape, and rarely exceeds 100 millimeters (mm) (4 inches (in)) in length. The ventral margin (bottom) of the shell is often angled posteriorly in females, resulting in a pointed posterior margin. The periostracum (skin of the shell) is yellow-brown to blackish and has fine rays on the posterior half. The nacre (shell interior) is white, becoming iridescent posteriorly.

Gravid females (females with larvae) have been observed March through June. Fine-lined pocketbooks have also been observed releasing glochidia in a single large conglutinate (Haag et al., 1999), termed a superconglutinate (Haag et al., 1995). Redeye bass (Micropterus coosa), spotted bass (M. puctulatus), largemouth bass (M. salmoides), and green sunfish (Lepomis cyanellus) have been identified as suitable hosts (Haag et al., 1999).

The fine-lined pocketbook was historically reported from the Tombigbee, Black Warrior, Cahaba, Alabama, Tallapoosa, and Coosa Rivers and many of their tributaries in Alabama, Georgia, Mississippi, and Tennessee. The species has apparently disappeared from the Tombigbee and Alabama River drainages, and possibly from the Black Warrior River drainage. Since publication of the final rule listing the fine-lined pocketbook, this mussel continues to survive in the upper Cahaba River and the Little Cahaba River (Jefferson/Shelby/Bibb Counties, Alabama); Coosa River (Cherokee County, Alabama) and its tributaries, including Duck Creek (Walker County, Georgia), Euharlee Creek (Bartow County, Georgia), Conasauga River (Murray/Whitfield County, Georgia; Polk County, Tennessee), and Holly Creek (Murray County, Georgia), Terrapin Creek, and South Fork Terrapin Creek (Cleburne County, Alabama); Yellowleaf Creek and its tributary Muddy Prong (Shelby County, Alabama); Kelly Creek and its tributary Shoal Creek (Shelby/St. Clair County, Alabama), Choccolocco Creek (Calhoun County, Alabama) and its tributaries Cheaha Creek (Talladega/Clay County, Alabama), Shoal Creek (Cleburne County, Alabama), Hatchet Creek (Coosa/Clay County, Alabama), and Tallasahatchee Creek (Talladega County, Alabama); and the Tallapoosa River and tributaries, including Uphapee Creek (Macon County, Alabama), Choctafaula Creek (Macon/Lee County, Alabama), Chewacla Creek (Macon/Lee County, Alabama), Opintlocco Creek (Macon County, Alabama), Cane and Little Cane Creeks (Cleburne County, Alabama), Muscadine Creek (Cleburne County, Alabama), Big Creek (Haralson County, GA), and McClendon Creek (Paulding County, Georgia). Populations are small and localized within these streams (Dodd et al., 1986; Evans, 2001; Feminella and Gangloff, 2000; Haag et al., 1999; Herod et al., 2001; E. Irwin, U.S. Geological Survey, in litt. 2000; Irwin et al., 1998; Johnson and Evans, 2000; L. McDougal, U.S. Forest Service, in litt. 1994; McGregor, M. 1993; McGregor et al. 2000; Pierson, 1991a, 1992b, 1993; Shepard et al., 1994; Williams and Hughes 1998).

Orange-nacre Mucket (Lampsilis perovalis (Conrad 1834))

The orange-nacre mucket is a medium-sized mussel, 50 to 90 mm (2.0 to 3.6 in) in length. The shell is oval in shape, moderately thick, and inflated. The posterior margin of the shell of mature females is obliquely truncate (shortened). The nacre is usually colored orange, rose, pink, or occasionally white. The periostracum varies from yellow to dark reddish brown, and with or without green rays.

The orange-nacre mucket expels mature glochidia in a single superconglutinate (Haag et al. 1995). Discharge of superconglutinates has been observed between March and June, with releases appearing concentrated in early April (Hartfield and Butler 1997). Redeye bass, spotted bass, and largemouth bass have been identified as suitable host fish for the orange-nacre mucket (Haag and Warren 1997).

The orange-nacre mucket was historically known from the Alabama, Tombigbee, Black Warrior, and Cahaba Rivers and their tributaries in Alabama and Mississippi. The species has disappeared from the mainstem Tombigbee, Black Warrior, and Alabama Rivers, but continues to survive in Tombigbee tributaries, including the Buttahatchee River (Lowndes/Monroe County, Mississippi; Lamar County, Alabama), and East Fork Tombigbee River (Itawamba/Monroe County, Mississippi), Luxapalila Creek and tributaries Yellow Creek (Monroe County, Mississippi; Lamar County, Alabama) and Cut Bank Creek (Lamar County, Alabama), Sipsey River (Greene/Pickens/Tuscaloosa County, Alabama), Coalfire, Lubbub, and Trussels Creeks (Pickens County, Alabama); Black Warrior River tributaries, including North River (Tuscaloosa/Fayette County, Alabama) and its tributary Clear Creek (Fayette County, Alabama), Locust and Blackburn Forks of the Black Warrior River (Blount County, Alabama), Sipsey Fork of the Black Warrior (Winston/Lawrence County, Alabama) and tributaries Thompson, Flannagin, and Borden Creeks (Lawrence County, Alabama), and Caney, North Fork Caney, Brushy, Capsey, Rush, Brown, and Beech Creeks (Winston/Lawrence County, Alabama); Cahaba River (Bibb/Jefferson/Shelby County, Alabama) and Little Cahaba River (Bibb/Shelby County, Alabama); and Alabama River tributaries Limestone Creek (Monroe County, Alabama) and Bogue Chitto Creek (Dallas County, Alabama). The orange-nacre mucket is locally common in the Sipsey Fork and several of its tributaries. All other populations are small and localized (Alabama Malacological Research Center, in litt., 1996; Dodd et al. 1986; Haag and Warren 2001; Hartfield and Bowker 1992; Hartfield and Jones 1989, 1990; Jones 1991; Jones and Majure 1999; McGregor 1992; McGregor et al. 1996; McGrego 2000; McGregor et al. 2000; McGregor and Pierson 1999; McGregor and Haag in prep.; Miller 2000; MS Museum of Natural Science collection records 1989-1999; Pierson 1991a, b, 1992a; Shepard et . 1998; Vittor and Associates 1993; Warren and Haag 1994; Yokley 2001).

Alabama Moccasinshell (Medionidus acutissimus (Lea 1831))

The Alabama moccasinshell is a small, delicate species, approximately 30 mm (1.2 in) in length. The shell is narrowly elliptical, and thin, with a well-developed acute posterior ridge that terminates in an acute point on the posterior ventral margin. The posterior slope is finely corrugated. The periostracum is yellow to brownish yellow, with broken green rays across the entire surface of the shell. The thin nacre is translucent along the margins and salmon-colored in the umbos (beak cavity).

Alabama moccasinshell females are gravid from October to June. This species lives completely embedded in stream bottoms for most of the year. Gravid females migrate to the surface of the stream bottom between March and June, anchor themselves to gravel by a bysal thread (protein thread), and lie exposed, displaying a black mantle lure apparently to attract potential host fish (P. Hartfield pers. obs. 1994; Haag and Warren 2001). Blackspotted topminnows (Fundulus olivaceus), Tuskaloosa darter (Etheostoma douglasi), redfin darter (E. whipplei), blackbanded darter (Percina nigrofaciata), naked sand darter (Ammocrypta beani), southern sand darter (A. meridiana), johnny darter (E. nigrum), speckled darter (E. stigmaeum), saddleback darter (Percina vigil), and logperch (P. caprodes) have been identified as suitable host fish (Haag and Warren 1997, 2001).

The Alabama moccasinshell was historically known from the Alabama, Tombigbee, Black Warrior, Cahaba, and Coosa Rivers and their tributaries in Alabama, Mississippi, Georgia, and Tennessee. The species has disappeared from the mainstems of all of these rivers, but continues to survive in Tombigbee River tributaries, including Bull Mountain Creek (Itawamba County, Mississippi), Luxapalila Creek (Lowndes County, Mississippi) and tributary Yellow Creek (Lowndes County, Mississippi; Lamar County, Alabama), Buttahatchee River (Lowndes/Monroe County, Mississippi, Lamar County, Alabama), and tributary Sipsey Creek (Monroe County, Mississippi), Lubbub Creek (Pickens County, Alabama), and Sipsey River (Greene/Pickens County, Alabama); Black Warrior River tributaries, including the Sipsey Fork and tributaries (Winston/Lawrence County, Alabama); and Holly Creek (Murray County, Georgia) in the Coosa River drainage (Dodd et al.1986; Evans 2001; Hartfield and Bowker 1992; Hartfield and Jones 1989, 1990; Johnson and Evans 2000; Jones 1991; Jones and Majure 1999; McGregor 1992; McGregor et al. 1996; McGregor 2000; McGregor et al. 2000; MS Museum of Natural Science collection record 1984-2001; Pierson 1991a, b; Warren and Haag 1994; Yokley 2001). Except for the Sipsey Fork, populations are small and localized. Highest densities observed during field surveys have been from the Sipsey Fork and its headwater tributaries in Bankhead National Forest, where quantitative samples from selected sites estimated Alabama moccasinshells densities from 0 to 2.8/10 m² (Warren and Haag 1994).

Coosa Moccasinshell (Medionidus parvulus (Lea 1860))

The Coosa moccasinshell is a small species occasionally exceeding 40 mm (1.6 in) in length. The shell is thin and fragile, elongate and elliptical to rhomboidal in outline. The posterior ridge is inflated and smoothly rounded, terminating in a broadly rounded point; the posterior slope is finely corrugated. The periostracum is yellow-brown to dark brown and has fine green rays. The nacre is blue, occasionally with salmon-colored spots.

Coosa moccasinshells are usually completely buried in the stream bottom. Because this species is apparently closely related to the Alabama moccasinshell, gravid females of this species likely migrate to the surface of the stream bottom during spring glochidial release periods, as do gravid Alabama moccasinshell females. Coosa moccasinshell glochidia are known to use blackbanded darters as hosts; however, other species of darters are also likely to be used (P. Johnson, Tennessee Aquarium Research Institute, pers. comm. 2002).

The Coosa moccasinshell has been historically reported from the Cahaba River, the Sipsey Fork of the Black Warrior River, and the Coosa River, and their tributaries, in Alabama, Georgia, and Tennessee. Since the species was listed, its presence has been confirmed only in the Conasauga River (Murray/Whitfield County, Georgia; Bradley County, Tennessee), and its tributary, Holly Creek (Murray County, Georgia) (Johnson and Evans, 2000, Williams and Hughes 1998). It has apparently been eliminated from the Cahaba and Black Warrior River drainages, as well as from the Coosa River and many of its tributaries.

Ovate Clubshell (Pleurobema perovatum (Conrad 1834))

The ovate clubshell is a small to medium-sized mussel that rarely exceeds 50 mm (2.0 in) in length. The shell is oval to elliptical in shape, and has nearly terminal, inflated umbos. The posterior ridge is well-developed, broadly rounded, and often concave. The posterior slope is produced well beyond the posterior ridge. Periostracum color varies from yellow to dark brown, and occasionally has broad green rays that may cover most of the umbo and posterior ridge. The nacre is white. Gravid females of this species have been observed in June and July. Glochidia are released in well formed, white conglutinates (W.R. Haag unpublished data). Host fishes for this species are unknown.

The ovate clubshell was historically distributed in the Tombigbee, Black Warrior, Alabama, Cahaba, and Coosa Rivers and their tributaries in Mississippi, Alabama, Georgia, and Tennessee; and in Chewacla, Uphapee and Opintlocco Creeks in the Tallapoosa River drainage, Alabama. It has disappeared from the Black Warrior, Cahaba, and Alabama River drainages, as well as the mainstem Tombigbee River and Uphapee and Opintlocco Creeks. Currently, the species is known to survive in several Tombigbee River tributaries, including Buttahatchee River (Lowndes/Monroe County, Mississippi), Luxapalila Creek and its tributary Yellow Creek (Lowndes County, Mississippi), Sipsey River (Greene/Pickens/Tuscaloosa County, Alabama), Sucarnoochee River (Sumter County, Alabama), and Coalfire Creek (Pickens County, Alabama); and Chewacla Creek (Macon County, Alabama) in the Tallapoosa River drainage; and a short reach of the Coosa River below the mouth of Terrapin Creek (Cherokee County, Alabama) (Dodd et al. 1986, Feminella and Gangloff 2000, Hartfield and Bowker 1992, Hartfield and Jones 1990, Jones 1991, McGregor 1992, McGregor 1993, McGregor et al. 1996, McGregor 2000, McGregor and Haag in prep., Miller 2000, Pierson, 1991a, b; Yokley 2001). Populations are small and localized.

Southern Clubshell (Pleurobema decisum (Lea 1831))

The southern clubshell is a medium sized mussel about 70 mm (2.8 in) long, with a thick shell, and heavy hinge plate and teeth. The shell outline is roughly rectangular, produced posteriorly with the umbos terminal with the anterior margin, or nearly so. The posterior ridge is moderately inflated and ends abruptly with little development of the posterior slope at the dorsum of the shell. The periostracum is yellow to yellow-brown with occasional green rays or spots on the umbo in young specimens.

Gravid southern clubshell females with mature glochidia have been collected in June and July. Glochidia are released in well formed conglutinates orange or white in coloration (Haag and Warren 2001). Blacktail shiner (Cyprinella venusta), Alabama shiner (C. callistia), and tricolor shiner (C. trichroistia) have been identified as fish host (Haag and Warren 2001, P. Johnson pers. comm. 2002).

With the exception of the Tensas/Mobile River, the southern clubshell was formerly known from every major river system in the Mobile River Basin, including the Alabama, Tombigbee, Black Warrior, Cahaba, Tallapoosa, and Coosa Rivers and many of their tributaries in Mississippi, Alabama, Georgia, and Tennessee. This species has disappeared from the Cahaba River drainage, the main channels of the Tombigbee and Black Warrior Rivers, and from a number of tributaries in all of the drainages. Southern clubshell continues to inhabit the East Fork Tombigbee River (Itawamba/Monroe County, Mississippi), Bull Mountain Creek (Itawamba County, Mississippi), Buttahatchee River (Monroe/Lowndes County, Mississippi), Luxapalila and Yellow Creeks (Lowndes County, Mississippi), Lubbub Creek (Pickens County, Alabama), and Sipsey River (Greene/Pickens/Tuscaloosa County, Alabama) in the Tombigbee drainage; a short reach of the Alabama River and Bogue Chitto Creek (Dallas County, Alabama); Chewacla Creek (Macon County, Alabama) in the Tallapoosa drainage; Coosa River (Dead River) below Weiss Dam (Cherokee County, Alabama) and tributaries Kelly Creek (Shelby County, Alabama), Big Canoe Creek (St. Clair County, Alabama), Terrapin Creek (Cherokee County, Alabama), and Conasauga River (Murray/Whitfield County, Georgia) (Alabama Department of Conservation and Natural Resources/U.S. Fish and Wildlife Service collection records, 1998, 1999; Evans 2001; Feminella and Gangloff 2000; Hartfield and Bowker 1992; Hartfield and Jones 1989, 1990; Herod et al. 2001; Jones 1991; Jones and Majure 1999; McGregor 1993, 1999; McGregor et al. 1996; Miller 2000; Miller and Hartfield, 1988; Pierson, 1991a, b; Yokley 2001). The southern clubshell is relatively common in localized reaches of the Buttahatchee and Sipsey Rivers. Average density at four sites in the Coosa River below Weiss Dam was 0.19/square meter (Herod et al. 2001). It is rare to uncommon in other occupied streams.

Dark Pigtoe (Pleurobema furvum (Conrad 1834))

The dark pigtoe is a small to medium-sized mussel, occasionally reaching 60 mm (2.4 in) in length. The shell is oval in outline, and moderately inflated. Beaks are located in the anterior portion of the shell. The posterior ridge is abruptly rounded and terminates in a broadly rounded, subcentral, posterior point. The periostracum is dark, reddish brown with numerous and closely spaced, dark growth lines. The hinge plate is wide and the teeth are heavy and large, especially in older specimens. The nacre approaches white in the umbos, and is highly iridescent on the posterior margin. This species is gravid in June and releases glochidia in peach to pink-colored conglutinates (Haag and Warren 1997). The largescale stoneroller (Campostoma oligolepis), Alabama shiner, blacktail shiner, creek chub (Semotilus atromaculatus), and blackspotted topminnow have been confirmed as suitable hosts (Haag and Warren 1997).

The historic distribution of the dark pigtoe was probably restricted to the Black Warrior River system above the fall line (natural contour that marks a drop in land level). Since listing, the presence of the dark pigtoe has been confirmed in the Black Warrior River drainage from Sipsey Fork and its tributaries Caney, Brown, Rush, and Capsey Creeks (Winston/Lawrence County, Alabama); and from the North River and its tributary Clear Creek (Fayette County, Alabama) (Alabama Malacological Research Center, in litt., 1996; Dodd et al. 1986; McGregor 1992; Pierson 1992a; Shepard et al. 1998; Vittor and Associates 1993; Warren and Haag 1994). Badly weathered shells have also been found in the Locust Fork of the Black Warrior River near the Jefferson-Blount County line. Populations are small and localized. Highest densities measured during field surveys have been from the Sipsey Fork and its headwater tributaries in Bankhead National Forest, where quantitative samples from selected sites estimated dark pigtoe densities from 0 to 4.8/10 m² (Warren and Haag 1994).

Southern Pigtoe (Pleurobema georgianum (Lea 1841))

The southern pigtoe is a small to medium-sized mussel occasionally exceeding 60 mm (2.4 in) in length. The shell is elliptical to oval in outline and somewhat compressed. The posterior slope is smoothly rounded. The pseudocardinal teeth (protrusions on the dorsal interior surface of the shell) are small but well-developed, and the nacre is white. The periostracum is yellow to yellow-brown. Growth lines are numerous and may be dark brown. Small specimens may have green spots at the growth lines along the posterior ridge and near the umbo. Host fish are Alabama shiner, blacktail shiner, and tricolor shiner (P. Johnson pers. comm. 2002).

The historic range of the southern pigtoe included the Coosa River and its tributaries in Alabama, Georgia, and Tennessee. The species is currently known to survive in the Conasauga River (Murray/Whitfield County, Georgia, Bradley County, Tennessee), Holly Creek (Murray County, Georgia), Shoal Creek (Cleburne County, Alabama), Big Canoe Creek (St. Clair County, Alabama), and Cheaha Creek (Talladega County, Alabama) (Evans 2001, Feminella and Gangloff 2000, Johnson and Evans, 2000; Pierson 1992b, 1993; Williams and Hughes 1998). Populations are small and localized.

Triangular Kidneyshell (Ptychobranchus greeni (Conrad 1834))

The triangular kidneyshell is oval to elliptical in outline, and may approach 100 mm (4.0 in) in length. The shell is generally compressed, and may be flattened ventral to the umbos. The posterior ridge is broadly rounded and terminates in a broad round point post-ventrally. The pseudocardinal teeth are heavy, and the laterals are heavy, gently curved and short. The periostracum is straw-yellow in young specimens, but becomes yellow-brown in older ones. It may have fine and wavy, or wide and broken, green rays anterior to the posterior ridge.

Gravid triangular kidneyshell females were observed in March 1994 and April 1996. Glochidia are packaged into conglutinates that mimic small aquatic fly larvae (Hartfield and Hartfield 1996) or fish eggs (Haag and Warren 1997). Suitable fish hosts have been identified as Warrior darter (Etheostoma bellator), Tuskaloosa darter, blackbanded darter and logperch (Haag and Warren 1997).

The historic range of the triangular kidneyshell included the Black Warrior, Cahaba, Alabama, and Coosa Rivers and tributaries in Alabama, Georgia, and Tennessee. The species has disappeared from the Alabama River, and from the primary channels of the Black Warrior and Coosa Rivers. Triangular kidneyshell is currently known to inhabit the Sipsey Fork and tributaries (Winston/Lawrence County, Alabama) and Locust Fork (Blount County, Alabama) of the Black Warrior; Cahaba River (Bibb County, Alabama); and Coosa tributaries Shoal Creek (Cleburne County, Alabama), Kelly Creek (Shelby County, Alabama), Big Canoe Creek (St. Clair County, Alabama), Conasauga River (Murray/Whitfield County, Georgia, Bradley County, Tennessee), Holly Creek (Murray County, Georgia), Coosawattee River (Gordon County, Georgia), and Oostanaula River (Floyd/Gordon County, Georgia). Populations are small and localized (Dodd et al. 1986, Evans 2001, Feminella and Gangloff 2000, Haag and Warren 1997, Johnson and Evans 2000, McGregor 1992, McGregor et al. 2000, Shepard et al. 1994, 1998; Warren and Haag 1994, Williams and Hughes 1998).

Southern Acornshell (Epioblasma othcaloogensis (Lea 1857))

The southern acornshell is a small mussel that may grow up to 30 mm (1.2 in) in shell length. The shells are round to oval in outline and sexually dimorphic, with a swollen posterior ridge in females. The periostracum is smooth, shiny, and yellow in color. Life history and host fish are unknown.

Historically, the southern acornshell occurred in the upper Coosa River system and the Cahaba River above the fall line in Alabama, Georgia, and Tennessee. The most recent records for the southern acornshell were from tributaries of the Coosa River in the early 1970s, and the Cahaba in the 1930s (58 FR 14330). It was our determination at the time of listing, with consensus of the malacological (mollusk research) community, that this species was likely to persist in low numbers in the upper Coosa River drainage, and possibly in the Cahaba River. Surveys of Coosa River tributaries have been conducted by Service biologists, as well as Bogan and Pierson (1993a), Evans (2001), Feminella and Gangloff (2000), Johnson and Evans (2000), Pierson (1993, pers. comm. 1994), Williams and Hughes (1998), and others. Surveys of the Cahaba River have been conducted by Service biologists, Bogan and Pierson (1993b), McGregor et al. (2000), Shepard et al. (1994, 1998), and others. Despite these repeated surveys of historic habitat in the Coosa and Cahaba River drainages, no living animals or fresh shells of this species have been located in recent years (Evans 2001, Feminella and Gangloff 2000, Johnson and Evans 2000, McGregor et al. 2000, Pierson 1993, Shepard et al. 1994, 1998, Williams and Hughes 1998). Not withstanding the results of these surveys, this species’ historic range includes thousands of miles of river and stream habitat in the Mobile River Basin, and there are many miles of stream which have not been adequately surveyed. Mussels are cryptic species, living buried in the stream bottom under water, and rare mussels are difficult to locate.

Upland Combshell (Epioblasma metastriata (Conrad 1838))

The upland combshell is a bivalve mollusk that rarely exceeds 60 mm (2.4 in) in length. The shells are rhomboidal to quadrate in outline and are sexually dimorphic. Males are moderately inflated with a broadly curved posterior ridge. Females are considerably inflated, with a sharply elevated posterior ridge that swells broadly post-ventrally forming a well-developed sulcus (the groove anterior to the posterior ridge). The posterior margin of the female is broadly rounded and comes to a point anterior to the posterior extreme. Periostracum color varies from yellowish-brown to tawny, and may or may not have broken green rays or small green spots. Hinge teeth are well-developed and heavy. This species likely releases glochidia during late spring or early summer (Service 2000). The host fish for this species have not been identified.

The historic range of the upland combshell included portions of the Black Warrior, Cahaba, and Coosa Rivers of the Mobile River Basin and some of their tributaries in Alabama, Georgia, and Tennessee. The most recent records for the upland combshell were from the Conasauga River, Georgia, in 1988, and from the Cahaba River, Alabama, in the early 1970s (58 FR 14330). When listed, the species was believed to be restricted to the Conasauga River in Georgia, and possibly portions of the upper Black Warrior and Cahaba River drainages. Surveys of Coosa River tributaries have been conducted by Service biologists, as well as Bogan and Pierson (1993a), Evans (2001), Feminella and Gangloff (2000), Johnson and Evans (2000), Pierson (1993, pers. comm. 1994), Williams and Hughes (1998), and others. Surveys of the Cahaba River have been conducted by Service biologists, Bogan and Pierson (1993b), McGregor et al. (2000), Shepard et al. (1994), and others. Surveys in the upper Black Warrior drainage have been done by Service biologists, Alabama Malacological Research Center, (in litt. 1996), Sheppard et al. (1998), Vittor and Associates (1993), Warren and Haag (1994), and others. However, these surveys of the Conasauga River and other historic habitat in the Coosa, Cahaba, and Black Warrior River drainages since the mussel was listed have failed to locate any evidence of the upland combshell (Evans 2001, Feminella and Gangloff 2000, Johnson and Evans 2000, McGregor 1992, McGregor et al. 2000, Pierson 1991a, Shepard et al. 1994, 1998, Vittor and Associates 1993, Warren and Haag 1994, Williams and Hughes 1998). Not withstanding the results of these surveys, this species’ historic range includes thousands of miles of river and stream habitat in the Mobile River Basin, and there are many miles of stream which have not been adequately surveyed. Mussels are cryptic species, living buried in the stream bottom under water, and rare mussels are difficult to locate.

The summary of these 11 mussel species, presented above, represents our current understanding of their historic and current range and distribution. There has been some confusion in species identification in recent reports. For example, some survey reports have identified mussel populations from Black Warrior River tributaries, Cahaba River, and Bogue Chitto Creek as fine-lined pocketbook, while others have identified the same populations as orange-nacre mucket. Although there may be some overlap in these species’ current ranges, we believe that this confusion originated from collectors unfamiliar with one or both species. There is also some confusion surrounding recently rediscovered populations of clubshell in the Coosa River drainage. Some biologists believe these populations may include painted clubshell (Pleurobema chattanoogaense), a form that we considered the same as southern clubshell (Pleurobema decisum) in the March 17, 1993, final rule listing for these 11 mussels (58 FR 14330). There is some morphological evidence that recognition of painted clubshell as a species may be warranted, however, recent genetic studies were unable to discriminate between the 2 forms. Therefore, at this time, we consider populations of clubshell in the Coosa River drainage to be southern clubshell. The distributions presented above, are based upon shell morphology as described and currently recognized in the scientific literature. Therefore, we will consider these species’ current ranges as outlined above, until presented with new information.

Summary of Decline and Threats to Surviving Populations

The disappearance of these 11 mussel species from significant portions of their ranges is primarily due to changes in river and stream channels caused by dams, dredging, or mining, and historic or episodic pollution events (58 FR 14330). More than 1,700 km (1,100 mi) of large and small river habitat in the Basin have been impounded by dams for navigation, flood control, water supply, and/or hydroelectric production purposes. None of the 11 species are known to survive in impounded waters. Riverine mussels are killed during construction of dams, they may be suffocated by sediments that accumulate behind the dams; and the reduced water flow behind dams limits food and oxygen available to mussels. Many fish species that serve as hosts to mussel larvae are also eliminated by dams and impounded waters.

Other forms of habitat modification — such as channelization, channel clearing and desnagging (woody debris removal), and gold and gravel mining — caused stream bed scour and erosion, increased turbidity, reduction of groundwater levels, and sedimentation, often resulting in severe local impacts to, and even extirpation of, mussel species. Sedimentation may also eliminate or reduce recruitment of juvenile mussels (Negus 1966), and suspended sediments can also interfere with feeding (Dennis 1984).

Water pollution from coal mines, carpet mills, fabric dying mills, large industrial plants, inadequately treated sewage, and land surface runoff also contributed to the demise of the species in certain portions of their historic ranges. Freshwater mussels, especially in their early life stages, are extremely sensitive to many pollutants (e.g., chlorine, ammonia, heavy metals, high concentrations of nutrients) commonly found in municipal and industrial wastewater effluents (Havlik and Marking 1987, Goudreau et al. 1988, Keller and Zam 1991). Stream discharges from these sources may result in decreased dissolved oxygen concentration, increased acidity and conductivity, and other changes in water chemistry, which may impact mussels or their host fish.

The historic activities discussed above, especially dam construction, had a second major impact on mussel species by isolating surviving populations within limited portions of the Basin’s major drainages. The Mobile River Basin Aquatic Ecosystem Recovery Plan (U.S. Fish and Wildlife Service 2000) recognized habitat fragmentation as one of the primary threats to the Basin’s imperiled aquatic species. Small isolated mussel populations are more vulnerable to natural random events, such as droughts or floods, as well as to changes in human activities and land use practices that impact aquatic habitats (Neves et al. 1997). A number of the Basin’s imperiled mussel populations that became restricted to small tributaries or river segments eventually disappeared because of individual or cumulative impacts of land uses such as urbanization, industrialization, mining, and certain agricultural activities and practices that resulted in sedimentation, eutrophication (an aquatic condition in which the increase in mineral and organic nutrients reduces dissolved oxygen producing an environment that favors plant life over animal life), or other negative effects to stream and river habitats (58 FR 14330, U.S. Fish and Wildlife Service 2000).

Human populations and associated needs for housing, commerce, recreation, water, electricity, forest and agricultural products, waste disposal, and mineral exploitation continue to increase in the Basin (U.S. Fish and Wildlife Service 2000). Currently surviving populations of endangered and threatened mussels remain vulnerable to habitat loss, population isolation, and the cumulative effects of these land use activities on aquatic environments (U.S. Fish and Wildlife Service 2000). More detailed information on threats to these species can be found in the March 17, 1993, final listing determination (58 FR 14330) and in the Mobile River Basin Aquatic Ecosystem Recovery Plan (U.S. Fish and Wildlife Service 2000).

Previous Federal Actions

Federal actions began when the orange-nacre mucket was included as a category 2 species (May 22, 1984, 49 FR 21675). We applied category 2 designations to those species for which some evidence of vulnerability existed, but for which we needed additional biological information to support a proposed rule to list as endangered or threatened. In the January 6, 1989, Notice of Review (54 FR 578-579), this species was again included as a category 2 species. In the same Notice of Review, the upland combshell, southern acornshell, and fine-lined pocketbook were additionally included as category 2 species. A status review completed in 1991 for these four species, and seven other mussels endemic to the Basin, recommended listing the upland combshell, southern acornshell, Coosa moccasinshell, southern clubshell, dark pigtoe, southern pigtoe, ovate clubshell, and triangular kidneyshell as endangered species, and the fine-lined pocketbook, orange-nacre mucket, and Alabama moccasinshell as threatened species (Hartfield 1991).

We proposed the 11 mussel species for protection under the Act on November 19, 1991 (56 FR 58339). In that proposed rule, we stated that critical habitat was not prudent because of the threat of illegal commercial harvest. Legal notices announcing the proposal and requesting public comments were published in The Clarion-Ledger (Jackson, Mississippi) on December 6, 1991; the Mobile Press Register (Mobile, Alabama) on December 7, 1991; and The Atlanta Constitution (Atlanta, Georgia), the Commercial Dispatch (Columbus, Mississippi), and the Montgomery Advertiser (Montgomery, Alabama) on December 8, 1991. We published a final rule on March 17, 1993 (58 FR 14330), listing the fine-lined pocketbook, orange-nacre mucket, and Alabama moccasinshell as threatened species, and the Coosa moccasinshell, ovate clubshell, southern clubshell, dark pigtoe, southern pigtoe, triangular kidneyshell, upland combshell, and southern acornshell as endangered species.

New mussel harvest regulations adopted by the State of Alabama, and other information received in public comments during the open comment period, removed our concerns about illegal commercial harvest, and in the final rule, we determined that critical habitat was prudent but not determinable for the 11 mussel species. The not determinable finding was because of insufficient information on distribution and the biological needs of these species. Section 4(b)(6)(C) of the Act provides that a concurrent critical habitat determination is not required with a final regulation implementing endangered or threatened status and that the final designation may be postponed for 1 additional year beyond the period specified in section 4(b)(6)(A), if a prompt determination of endangered or threatened status is essential to the conservation of the species, or if critical habitat is not then determinable. We found that prompt determination of status was essential to the conservation of these species and stated that we would attempt to evaluate critical habitat needs through research and recovery actions.

In late 1994, a Technical/Agency draft Mobile River Basin Aquatic Ecosystem Recovery Plan that included recovery objectives for the 11 mussels, among other listed species, was released for public review and comment. High levels of interest in details of the plan were expressed by the State of Alabama, certain environmental groups, and a number of water-and timber-related industries. As a result of a series of discussions sponsored by the Alabama Department of Economic and Community Affairs, a Mobile River Basin Coalition composed of various governmental, environmental, and industry representatives was organized for the purpose of reviewing, revising, and eventually implementing the recovery plan. A revised Technical/Agency draft was subsequently released for public review in 1998, and the final Mobile River Basin Aquatic Ecosystem Recovery Plan was published in 2000 (U.S. Fish and Wildlife Service 2000).

On October 12, 2000, the Southern Appalachian Biodiversity Project filed a lawsuit in U.S. District Court for the Eastern District of Tennessee against the Service, the Director of the Service, and the Secretary of the Department of the Interior, challenging our not determinable findings regarding critical habitat for 9 listed mussels. These 9 mussels represent 9 of the 11 Mobile River Basin mussels that were listed in 1993, and are listed as follows: upland combshell, southern acornshell, Coosa moccasinshell, southern clubshell, southern pigtoe, ovate clubshell, triangular kidneyshell, fine-lined pocketbook, and Alabama moccasinshell. On November 8, 2001, the District Court issued an order directing us to make a proposed critical habitat designation for these 11 Mobile River Basin mussels no later than March 17, 2003, and the final designation by March 17, 2004.

This proposal is the product of our reexamination of our 1993 not determinable finding for 11 mussels in the Mobile River drainage. The 2000 lawsuit did not include the dark pigtoe or the orange-nacre mucket, but we are considering them because they were a part of the original 1993 listing, they overlap in range with some of the other 9 species, and they occupy similar habitats within that range. It reflects our interpretation of the recent judicial opinions on critical habitat designation and the standards placed on us for making a prudency determination. If additional information becomes available on these species’ biology, distribution, or threats to the species, we may reevaluate this proposal to propose additional critical habitat, propose boundary refinements that substantially changes existing proposed critical habitat, or withdraw our proposal to designate critical habitat. If boundary refinements of existing proposed critical habitat are required for a single unit or on a similar small scale based on additional information, we will allow additional time for public comment within the constraints of our court order.

Critical Habitat

Critical habitat is defined in section 3(5)(A) of the Act as (i) the specific areas within the geographic 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 (I) essential to the conservation of the species and (II) that may require special management considerations or protection; and (ii) specific areas outside the geographic 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” is defined in section 3(3) of the Act as the use of all methods and procedures that are necessary to bring any endangered or threatened species to the point at which listing under the Act is no longer necessary.

In order for habitat to be included in a critical habitat designation, the habitat features must be “essential to the conservation of the species.” Such critical habitat designations identify, to the extent known using the best scientific data available, habitat areas that provide essential life cycle needs of the species (i.e., areas on which are found the primary constituent elements, as defined at 50 CFR 424.12(b)).

Regulations at 50 CFR 424.02(j) define special management considerations or protection to mean any methods or procedures useful in protecting the physical and biological features of the environment for the conservation of listed species. If any areas containing the primary constituent elements are currently being managed to address the conservation needs of these mussel species, they may not require special management or protection, and, therefore, may not meet the definition of critical habitat in section 3(5)(A)(i) of the Act.

When we designate critical habitat, we may not have the information necessary to identify all habitat areas which are essential for the conservation of the species. Nevertheless, we are required to designate those areas we consider to be essential, using the best information available to us.

Within the geographic area of the species, we will designate only currently known essential areas. We will not speculate about what areas might be found to be essential if better information became available, or what areas may become essential over time. If the information available at the time of designation does not show that an area provides essential life cycle needs of the species, then the area will not be included in the critical habitat designation. Our regulations state that, “The Secretary shall designate as critical habitat areas outside the geographic area presently occupied by the species only when a designation limited to its present range would be inadequate to ensure the conservation of the species” (50 CFR 424.12(e)). Accordingly, when the best available scientific data do not demonstrate that the conservation needs of the species require designation of critical habitat outside of occupied areas, we will not designate critical habitat in areas outside the geographic area occupied by the species.

Section 4(b)(2) of the Act requires that we take into consideration the economic impact, and any other relevant impact, of specifying any particular area as critical habitat. We may exclude areas from critical habitat designation when the benefits of exclusion outweigh the benefits of including the areas within critical habitat, provided the exclusion will not result in extinction of the species.

Our Policy on Information Standards Under the Endangered Species Act, published on July 1, 1994 (59 FR 34271), provides guidance to ensure that our decisions are based on the best scientific and commercial data available. It requires that our biologists, to the extent consistent with the Act and with the use of the best scientific and commercial data available, use primary and original sources of information as the basis for recommendations to designate critical habitat. When determining which areas are critical habitat, information that should be considered includes the listing package for the species, the recovery plan, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys, studies, and biological assessments, unpublished materials, and expert opinion or personal knowledge.

Section 4 of the Act generally requires that we designate critical habitat at the time of listing and based on what we know at the time of designation. If we make a not determinable finding regarding critical habitat at the time of listing, section 4(b)(6)(C) of the Act requires that the Service publish a final regulation by not more than 1 additional year, based on such data as may be available at that time, designating, to the maximum extent prudent, such habitat. There are several thousands of miles of perennial streams in the Mobile River Basin. Most of these flow through private property, and may not have been adequately surveyed for mussels. Mussels are cryptic species, living buried in the stream bottom under water, and rare mussels are difficult to locate. We recognize that additional small, limited populations for some of these species could exist in some of these streams and may be discovered over time. Furthermore, we recognize that designation of critical habitat may not include all of the habitat areas that may eventually be determined to be necessary for the recovery of the species. Therefore, critical habitat designations do not signal that habitat outside the designation is unimportant or may not be required for recovery. Areas outside the critical habitat designation will continue to be subject to conservation actions that may be implemented under section 7(a)(1) of the Act and to the regulatory protections afforded by the section 7(a)(2) jeopardy standard and the take prohibitions pursuant to section 9 of the Act, as determined on the basis of the best available information at the time of the action. It is possible that federally funded or assisted projects affecting listed species outside their designated critical habitat areas could jeopardize those species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans, or other species conservation planning and recovery efforts if new information available to these planning efforts calls for a different outcome.

Methods used to Identify Proposed Critical Habitat for 11 Mussel Species

As required by section 4(b)(2) of the Act and implementing regulations (50 CFR 424.12), we used the best scientific and commercial information available to determine critical habitat areas that contain the physical and biological features that are essential for the conservation of the Coosa moccasinshell, southern clubshell, dark pigtoe, southern pigtoe, ovate clubshell, triangular kidneyshell, southern acornshell, upland combshell, fine-lined pocketbook, orange-nacre mucket, and Alabama moccasinshell. We reviewed the available information pertaining to the historic and current distributions, life histories, host fishes, and habitats of, and threats to these species. The information used in the preparation of this proposed designation includes: our own site-specific species and habitat information; unpublished survey reports, notes, and communications with other qualified biologists or experts; peer reviewed scientific publications; the final listing rule for 11 mussels in the Mobile River Basin (58 FR 14330); and the Mobile River Basin Aquatic Ecosystem Recovery Plan (U.S. Fish and Wildlife Service, 2000). In determining the areas that are essential to the conservation of the 11 mussels we considered all streams currently or historically known to be occupied by one or more of the species (see “Taxonomy, Life History, and Distribution” above). It is likely that other occupied stream or stream segments exist that may be essential to the survival and conservation of these mussels, but we do not currently know where these are, and therefore cannot include them in this proposed critical habitat designation.

Primary Constituent Elements

In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas to propose as critical habitat, we are required to base critical habitat determinations on the best scientific data available and to focus on those physical and biological features (primary constituent elements) that are essential to the conservation of the species and that may require special management considerations or protection. Such requirements include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, and rearing of offspring; and habitats that are protected from disturbance or are representative of the historical geographical and ecological distribution of a species.

Based on the best available information, primary constituent elements essential for the conservation of these 11 mussel species include the following: 

1. Geomorphically stable stream and river channels and banks;
2. A flow regime (i.e., the magnitude, frequency, duration, and seasonality of discharge over time) necessary for normal behavior, growth, and survival of all life stages of mussels and their fish hosts in the river environment;
3. Water quality, including temperature, pH, hardness, turbidity, oxygen content, and other chemical characteristics, necessary for normal behavior, growth, and viability of all life stages;
4. Sand, gravel, and/or cobble substrates with low to moderate amounts of fine sediment, low amounts of attached filamentous algae, and other physical and chemical characteristics necessary for normal behavior, growth, and viability of all life stages;
5. Fish hosts with adequate living, foraging, and spawning areas for them; and,
6. Few or no competitive nonnative species present.

In considering and identifying primary constituent elements, we have taken into account the dynamic nature of riverine systems. We recognize that riparian areas and floodplains are integral parts of the stream ecosystem, important in maintaining channel geomorphology, and providing nutrient input, and buffering from sediments and pollution; and that side channel and backwater habitats may be important in the life cycle of fish that serve as hosts for mussel larvae.

Analysis Used to Delineate Critical Habitat

Currently, the greatest general threat to the survival and recovery of these 11 Mobile River Basin mussel species is the small size, extent, and isolation of their remaining populations. With the exception of the dark pigtoe, which is believed to be naturally restricted to streams and rivers in the Black Warrior drainage, these mussel species were once widespread in the Basin, found in a continuum of small streams to large rivers in 2 or more major drainages. As discussed under the “Summary of Decline and Threats to Surviving Populations,” and the Mobile River Basin Aquatic Ecosystem Recovery Plan (U.S. Fish and Wildlife Service 2000), 30 major dams were constructed in the Basin during the 20^th century. These dams and their impounded waters present physical barriers to the natural dispersal of mussels (they prevent emigration (dispersal) of host fishes), and effectively isolate surviving mussel populations in limited portions of the Basin’s major drainages. Small isolated aquatic populations are subject to natural random events (droughts, floods), and to changes in human activities and land use practices (urbanization, industrialization, mining, certain agricultural activities and practices, etc.), that may severely impact aquatic habitats (Neves et al. 1997). Without avenues of emigration to less affected watersheds, mussel populations gradually disappear where land use activities result in deterioration of aquatic habitats. Local random events, and changes in human activities within the Basin’s unimpounded watersheds are believed to have caused or contributed to the disappearance of mollusks from significant portions of isolated stream habitats, resulting in the extinction of as many as 13 mussels, as well as a number of freshwater snail species (U.S. Fish and Wildlife Service 2000).

Most of the 11 mussel species considered in this proposed designation are currently represented by one or more small, restricted, and isolated populations. These surviving populations have been isolated from one another by dams and impounded reaches for 20 to 50 years, and remain vulnerable to the progressive degradation of their habitats from land surface runoff or random natural events such as droughts. In many of these surviving populations, there is also evidence of local population decline during the same time period (e.g., Evans 2001, Hartfield and Jones 1990, Williams and Hughes, 1998, McGregor et al. 2000).

The Mobile River Basin Aquatic Ecosystem Recovery Plan (U.S. Fish and Wildlife Service 2000), recognized the complexity of conserving the Basin’s imperiled species, and considered that downlisting or delisting these 11 mussels was unlikely in the foreseeable future because of the extent of their decline, the fragmentation and isolation of their habitats, and continuing impacts upon their habitats. Compounding these problems is a lack of information on specific habitat and life history requirements of these species, or on the physical threats that confront them (e.g., sediment, nutrient, and other pollutant sensitivities, etc.). Threats compounded by habitat fragmentation and isolation can be reduced by increasing the number, expanding the range, and increasing the density of populations. Preventing the extinction of those species listed as endangered, and arresting the continued decline of those species listed as threatened are the recovery objectives outlined in the recovery plan for these 11 mussels. The recovery plan emphasizes: (1) protection of surviving populations of these mussels and their stream and river habitats; (2) enhancement and restoration of habitats; (3) and population management, including augmentation and reintroduction of the 11 mussels into portions of their historic ranges to obtain these recovery objectives. In determining which areas to propose as critical habitat for these 9 mussels, we considered the factors discussed in the recovery plan, as well as the mussels’ historical distributions and the extent of current occupied habitats and their management potential.

We began our analysis by considering the historic ranges of the 11 mussel species. A large proportion of the Basin’s streams and rivers that historically supported these mussels has been modified by existing dams and their impounded waters. Therefore, extensive portions of the upper Tombigbee River, Black Warrior River, Tallapoosa River, Alabama River, and Coosa River cannot be considered essential to the conservation of these species because they no longer provide the physical and biological features that are essential for their conservation (see “Primary Constituent Elements” section).

Free-flowing river segments and their tributaries peripheral to the known historic range of the 11 mussels, and without any records of the species also cannot be considered to be essential to the conservation of these species (e.g., Mobile/Tensas River, lower Tombigbee River, etc.) and so were not considered further. Several streams with single site occurrence records of a single species were also not considered essential because of limited habitat availability, isolation, degraded habitat, and/or low management value or potential (e.g., Etowah River, Big Wills Creek, Little River, Armuchee Creek, Euharlee Creek, Limestone Creek, etc.).

We then evaluated streams and rivers within the historic ranges of these 11 species which had evidence that these mussels had occurred there at some point (i.e., collection records). We eliminated from consideration areas from which there have been no collection records for several decades and/or are remote from currently occupied areas (e.g., portions of the lower Alabama River, lower Cahaba River, Mulberry Fork, Noxubee River, Talladega Creek, and others). In evaluating streams for the upland combshell and southern acornshell, specifically, we considered their historic ranges (Black Warrior, Cahaba, and Coosa River drainages). We selected those areas which have the best potential for and we believe are essential to the conservation of these two mussels based on collection history, surviving mussel species assemblages, and habitat conditions.

This analysis resulted in the identification of 25 of the 26 stream or river reaches within the Basin (habitat units) occupied by 1 or more of the 11 species and that contain the primary constituent elements as indicated by the presence and persistence of one or more of the listed mussels (Figure 1, Units 1 to 25). We believe that these areas also support darters, minnows, and other fishes that have been identified as hosts or potential hosts for one or more of the mussels, as evidenced by fish collection records (Mettee et al. 1996), the persistence of the mussels over extended periods of time, or field evidence of recruitment (Evans 2001, Hartfield and Jones 1990, and Herod et al. 2001, etc.). We consider all of these 25 of the 26 reaches essential for the conservation of these species. As discussed in the Recovery Plan, long-term conservation of these 11 mussels is unlikely in their currently reduced and fragmented state. Therefore, at a minimum, it is essential to include in this designation the reaches within the historic range that still contain mussels and the primary constituent elements of the habitat.

We then considered whether this essential area was adequate for the conservation of each of the 11 mussel species. Given that threats to the species are compounded by their limited distribution and isolation, it is unlikely that currently occupied habitat is adequate for the conservation of all 11 species. Conservation of these species requires expanding their ranges into currently unoccupied portions of their historic habitat because small, isolated, aquatic populations are subject to chance catastrophic events and to changes in human activities and land use practices that may result in their elimination. Larger, more contiguous populations can reduce the threat of extinction due to habitat fragmentation and isolation.

Click on below for larger map

Because portions of the historic range of each of the 11 mussels were shared with 4 or more of the other mussel species, there is considerable overlap between species’ current and historical distributions within 25 of the 26 habitat units. This offers opportunities to increase each species’ current range and number of extant populations into units currently occupied by other listed species included in this designation. For example, the Alabama moccasinshell historically inhabited 16 of the units, and currently inhabits 7; fine-lined pocketbook was known from 12 of the units, and currently inhabits 10; orange-nacre mucket historically occupied 15 units, and is currently found in 12; and Coosa moccasinshell historically occupied 9 of the units, but is currently found in only 1. Successful reintroduction of the species into units that they historically occupied (and that are currently occupied by 1 or more of the 11 species) would expand the number of populations, thereby reducing threat of extinction. Each of the 25 of the 26 habitat units (Units 1-25) are currently occupied by 1 or more of the listed mussels. Only two occupied habitat units and one unoccupied habitat unit are proposed for the dark pigtoe because its range was naturally restricted to the Black Warrior drainage, and we are unable to identify any other unoccupied habitat units in the drainage that provide constituent elements.

As noted above, conservation of these species requires expanding their ranges into unoccupied portions of historic habitat. Therefore, in addition to these 25 habitat units, we also propose to designate the Coosa River below Jordan Dam (Unit 26) as critical habitat for 9 of the 11 mussel species. Shells of the fine-lined pocketbook were last collected from this reach in 1989 (Pierson 1991a), and it is also within the historic range of 8 other species. This is the only unit currently not occupied by at least 1 of the 11 species (Johnson 2002). This area has recently been identified as presenting high potential for the successful reintroduction of imperiled mussels in the Coosa River drainage (Johnson 2002). In 1990, the Alabama Power Company initiated a 2000 cubic feet per second minimum flow into the Coosa River below Jordan Dam (Federal Energy Regulatory Commission (FERC) 1990), greatly improving aquatic habitat quality. The lower Coosa River not only offers high-quality riverine habitat, but due to local geology it is relatively protected from non-point runoff, a major threat to all existing populations of these species. There are historic records of fine-lined pocketbook and southern clubshell from this 13 km (8 mi) reach of river (Johnson 2002, Pierson 1991a), and it is within the historic range of Alabama moccasinshell, Coosa moccasinshell, ovate clubshell, southern pigtoe, triangular kidneyshell, southern acornshell, and upland combshell. As noted above, threats to these species can be reduced by expanding their current ranges through reintroduction into suitable habitats. Since the Coosa River below Jordan Dam is recognized as presenting the best opportunity for reestablishing populations of 9 of the 11 species and is viewed by experts as a high-quality example of remaining mussel habitat in the Basin, we believe it is also essential for their conservation, and propose to designate it as unoccupied habitat for these 9 mussel species.

As a result, we have defined 26 habitat units encompassing approximately 1,760 km (1,093 mi) of stream and river channels in Alabama, Mississippi, Georgia, and Tennessee, for these 11 mussel species (Figure 1). Although this represents only a small proportion of each species’ historic range, these habitat units include a significant proportion of the Basin’s remaining, highest quality, free-flowing rivers and streams, and reflect the variety of small stream to large river habitats historically occupied by each species. Because mussels are naturally restricted by certain physical conditions within a stream or river reach (i.e., flow, substrate), they may be unevenly distributed within these habitat units. Uncertainty on upstream and downstream distributional limits of some populations may have resulted in small areas of occupied habitat excluded from, or areas of unoccupied habitat included in the designation.

We recognize that both historic and recent collection records upon which we relied are incomplete, and that there are river segments or small tributaries not included in this proposed designation that may harbor small, limited populations of one or more of the 11 species considered in this proposed designation, or that others may become suitable in the future. The exclusion of such areas does not diminish their potential individual or cumulative importance to the conservation of these species. However, we believe that with proper management each of the 26 habitat units are capable of supporting 1 or more of these 11 species, and will serve as source populations for artificial reintroduction into designated stream units, as well as assisted or natural migration into adjacent undesignated streams within the Basin.

At this time, the habitat areas contained within the units described below constitute our best evaluation of areas needed for the conservation of these species. Proposed critical habitat may be revised for any or all of these species should new information become available prior to the final rule, and existing critical habitat may be revised if new information becomes available after the final rule.

Need for Special Management Consideration or Protection

An area designated as critical habitat contains one or more of the primary constituent elements that are essential to the conservation of the species (see “Primary Constituent Elements” section), and that may require special management considerations or protection. Various activities in or adjacent to each of the critical habitat units described in this proposed rule may affect one or more of the primary constituent elements that are found in the unit. These activities include, but are not limited to, those listed in the “Effects of Critical Habitat” section as “Federal Actions That May Affect Critical Habitat and Require Consultation.” None of the proposed critical habitat units is presently under special management or protection provided by a legally operative plan or agreement for the conservation of these mussels. Therefore, we have determined that the proposed units may require special management or protection.

Proposed Critical Habitat Designation

The areas that we are proposing for designation as critical habitat for the 11 mussel species provide one or more of the primary constituent elements described above. In accordance with the Mobile River Aquatic Ecosystem Recovery Plan (2000), protection of the habitat in these units and their surviving populations is essential to the conservation of these 11 mussel species. All of the proposed areas require special management considerations to ensure their contribution to the conservation of these mussels. For each stream reach proposed as a critical habitat unit, the up- and downstream boundaries are described in general detail below; more precise estimates are provided in the Regulation Promulgation of this rule.

Critical Habitat Unit Descriptions

The critical habitat units described below include the stream and river channels within the ordinary high water line. As defined in 33 CFR 329.11, the ordinary high water line on nontidal rivers is the line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank; shelving; changes in the character of soil; destruction of terrestrial vegetation; the presence of litter and debris; or other appropriate means that consider the characteristics of the surrounding areas. We are proposing the following areas for designation as critical habitat for the 11 mussel species (Refer to Table 1 for the location and extent of proposed critical habitat for each species and more specifically to § 17.95, Critical habitat-fish and wildlife, at the end of this rule).

TABLE 1*:
APPROXIMATE RIVER DISTANCES, BY DRAINAGE, FOR OCCUPIED AND UNOCCUPIED PROPOSED CRITICAL HABITAT FOR THE 11 MUSSEL SPECIES