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Daily Rules, Proposed Rules, and Notices of the Federal Government

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R4-ES-2011-0050; 4500030113]

RIN 1018-AW92

Endangered and Threatened Wildlife and Plants; Determination of Endangered Species Status for the Alabama Pearlshell, Round Ebonyshell, Southern Kidneyshell, and Choctaw Bean, and Threatened Species Status for the Tapered Pigtoe, Narrow Pigtoe, Southern Sandshell, and Fuzzy Pigtoe, and Designation of Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.
ACTION: Final rule.
SUMMARY: We, the U.S. Fish and Wildlife Service, determine endangered species status for the Alabama pearlshell (Margaritifera marrianae), round ebonyshell (Fusconaia rotulata), southern kidneyshell (Ptychobranchus jonesi), and Choctaw bean (Villosa choctawensis), and threatened species status for the tapered pigtoe (Fusconaia burkei), narrow pigtoe (Fusconaia escambia), southern sandshell (Hamiota australis), and fuzzy pigtoe (Pleurobema strodeanum), under the Endangered Species Act of 1973, as amended (Act); and designate critical habitat for the eight mussel species. The effect of this regulation is to conserve these eight mussel species and their habitat under the Act.
DATES: This rule becomes effective on November 9, 2012.
ADDRESSES: This final rule, final economic analysis, and the coordinates from which the maps were generated are included in the administrative record for this critical habitat designation and are available on the Internet athttp://www.fws.gov/PanamaCityandhttp://www.regulations.govat Docket No. FWS-R4-ES-2011-0050, and at the Panama City FieldOffice. Any additional tools or supporting information that we may develop for this critical habitat designation will also be available at the Fish and Wildlife Service Web site and Field Office set out above, and may also be included in the preamble and/or athttp://www.regulations.gov. Comments and materials received, as well as supporting documentation used in preparing this final rule, are available for public inspection, by appointment, during normal business hours, at U.S. Fish and Wildlife Service, Panama City Field Office, 1601 Balboa Avenue, Panama City, FL 32405; telephone 850-769-0552; facsimile 850-763-2177.
FOR FURTHER INFORMATION CONTACT: Don Imm, Field Supervisor, U.S. Fish and Wildlife Service, Panama City Field Office, 1601 Balboa Avenue, Panama City, FL 32405; telephone 850-769-0552; facsimile 850-763-2177. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:

This document consists of: (1) A final rule to list the Alabama pearlshell (Margaritifera marrianae), round ebonyshell (Fusconaia rotulata), southern kidneyshell (Ptychobranchus jonesi), and Choctaw bean (Villosa choctawensis) as endangered species, and the tapered pigtoe (Fusconaia burkei), narrow pigtoe (Fusconaia escambia), southern sandshell (Hamiota australis), and fuzzy pigtoe (Pleurobema strodeanum) as threatened species; and (2) a final rule to designate critical habitat for the eight species.

Executive Summary

Why we need to publish a rule.Under the Endangered Species Act (Act), a species or subspecies may warrant protection through listing if it is an endangered or threatened species throughout all or a significant portion of its range. We are listing these eight mussels because they have disappeared from portions of their historic ranges or are very rare, and facing numerous ongoing threats. The Alabama pearlshell and southern kidneyshell no longer occur in 50 percent or more of the stream systems in which they were historically found. The round ebonyshell is extremely rare, and its distribution is restricted to the main channel of the Escambia-Conecuh River. Choctaw bean populations in the Escambia River drainage are fragmented, and the species' numbers are low throughout its range. The narrow pigtoe, fuzzy pigtoe, southern sandshell, and tapered pigtoe still occur in much of their known range but have disappeared from many of the tributary and main channel locations from which they were historically known. All are facing a variety of threats. However, habitat degradation and loss as a result of excessive sedimentation, bed destabilization, poor water quality, and environmental contaminants are considered the most significant threats to these eight mussels. We are also designating critical habitat under the Act. Critical habitat is designated on the basis of the best scientific information available after taking into consideration the economic impact, impact on national security, and any other relevant impact of specifying any particular area as critical habitat. In total, approximately 2,404 kilometers (km) (1,494 miles (mi.)) of stream and river channels in nine units in Bay, Escambia, Holmes, Jackson, Okaloosa, Santa Rosa, Walton, and Washington Counties, Florida; and Barbour, Bullock, Butler, Coffee, Conecuh, Covington, Crenshaw, Dale, Escambia, Geneva, Henry, Houston, Monroe, and Pike Counties, Alabama, are being designated.

The basis for our action.Under the Act, a species may be listed as an endangered or threatened species based on any of five factors: (A) The present destruction, modification, or curtailment of its habitat or range; (B) overutilizationfor commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its existence. These eight mussel species are facing threats due to three of these five factors (A, D and E). The Act also requires that the Service designate critical habitat at the time of listing to the maximum extent prudent and determinable. We have determined that the designation is prudent and critical habitat is determinable for each of the eight species (see Critical Habitat section below).

We prepared an economic analysis.To ensure that we consider the economic impacts, we prepared an economic analysis of the designation of critical habitat. We published an announcement and solicited public comments on the draft economic analysis. The analysis found that the estimated incremental economic cost of this critical habitat designation to be $1.70 million over a 20-year time frame. The majority of the economic impacts are associated with the transportation sector, particularly consultation costs associated with the replacement and maintenance of bridges and roads.

We requested peer review of the methods used in our proposed listing and critical habitat designation.We specifically requested that four knowledgeable individuals with scientific expertise on freshwater mussel conservation and biology, and who are familiar with the eight species and the three river basins in which they occur, review the scientific information and methods in the proposed rule. The peer reviewers generally concurred with our methods and conclusions and provided additional information,clarifications, and suggestions to improve the final rule.

We sought public comment on the designation.During the first comment period, we received five comment letters directly addressing the proposed listing and critical habitat designation. During the second comment period, we received four comment letters addressing the proposed listing and critical habitat designation, and the draft economic analysis.

Background

It is our intent to discuss in this final rule only those topics directly relevant to the listing and designation of critical habitat for the Alabama pearlshell, round ebonyshell, southern kidneyshell, Choctaw bean, tapered pigtoe, narrow pigtoe, southern sandshell, and fuzzy pigtoe under the Act (16 U.S.C. 1531et seq.). For more information on the biology, ecology, and critical habitat of these eight mussel species refer to the proposed rule published in theFederal Registeron October 4, 2011 (76 FR 61482). Information on the associated draft economic analysis for the proposed rule was published in theFederal Registeron March 27, 2012 (77 FR 18173).

Previous Federal Actions

On October 4, 2011, we published the proposed rule to list and designate critical habitat for these eight mussels (76 FR 61482). Federal actions for these species prior to October 4, 2011, are outlined in the proposed rule. Publication of the proposed rule opened a 60-day comment period, which closed on December 5, 2011. On March 27, 2012 (77 FR 18173), we reopened the comment period for 30 days, from March 27 through April 26, 2012, in order to announce the availability of and receive comments on a draft economic analysis, and to extend the comment period on the proposed listing and critical habitat designation.

Introduction

North American freshwater mussel fauna is the richest in the world and historically numbered around 300 species (Williamset al.1993, p. 6). Freshwater mussels are in decline, however, and in the past century have become more imperiled than any other group of organisms (Williamset al.2008, p. 55; Natureserve 2011). Approximately 66 percent of North America's freshwater mussel species are considered vulnerable to extinction or possibly extinct (Williamset al.1993, p. 6). Within North America, the southeastern United States is the hot spot for mussel diversity. Seventy-five percent of southeastern mussel species are in varying degrees of rarity or possibly extinct (Neveset al.1997, pp. 47-51). The central reason for the decline of freshwater mussels is the modification and destruction of their habitat, especially from sedimentation, dams, and degraded water quality (Neveset al.1997, p. 60; Bogan 1998, p. 376). These eight mussels, like many other southeastern mussel species, have undergone reductions in total range and population density.

These eight species are all freshwater bivalve mussels of the families Margaritiferidae and Unionidae. The Alabama pearlshell is a member of the family Margaritiferidae, while the round ebonyshell, southern kidneyshell, Choctaw bean, tapered pigtoe, narrow pigtoe, southern sandshell, and fuzzy pigtoe belong to the family Unionidae. These mussels are endemic to (found only in) portions of three Coastal Plain rivers that drain south-central and southeastern Alabama and northwestern Florida: the Escambia (known as the Escambia River in Florida and the Conecuh River in Alabama), the Yellow, and the Choctawhatchee. All three rivers originate in Alabama and flow across the Florida panhandle before emptying into the Gulf of Mexico, and are entirely contained within the East Gulf Coastal Plain Physiographic Region. The Alabama pearlshell is also known from three locations in the Mobile River Basin; however, only one of those is considered to be currently occupied.

General Biology

Freshwater mussels generally live embedded in the bottom of rivers, streams, and other bodies of water. They siphon water into their shells and across four gills that are specialized for respiration and food collection. Food items include detritus (disintegrated organic debris), algae, diatoms, and bacteria (Strayeret al.2004, pp. 430-431). Adults are filter feeders and generally orient themselves on or near the substrate surface to take in food and oxygen from the water column. Juveniles typically burrow completely beneath the substrate surface and are pedal (foot) feeders (bringing food particles inside the shell for ingestion that adhere to the foot while it is extended outside the shell) until the structures for filter feeding are more fully developed (Yeageret al.1994, pp. 200-221; Gatenbyet al.1996, p. 604).

Sexes in margaritiferid and unionid mussels are usually separate. Males release sperm into the water column, which females take in through their siphons during feeding and respiration. Fertilization takes place inside the shell. The eggs are retained in the gills of the female until they develop into mature larvae called glochidia. The glochidia of most freshwater mussel species, including all eight species addressed in this rule, have a parasitic stage during which they must attach to the gills, fins, or skin of a fish to transform into a juvenile mussel. Depending on the mussel species, females release glochidia either separately, in masses known as conglutinates, or in one large mass known as a superconglutinate. The duration of the parasitic stage varies by mussel species, water temperature, and perhaps host fish species. When the transformation is complete, the juvenile mussels drop from their fish host and sink to the stream bottom where, given suitable conditions, they grow and mature into adults.

Survey Data

Recent distributions are based on surveys conducted from 1995 to 2012. Historical distributions are based on collections made prior to 1995. Historical distribution data from museum records and surveys dated between the late 1800s and 1994 are sparse, and most of these species were more than likely present throughout their respective river basins. Knowledge of historical and current distribution and abundance data were summarized from Butler 1989; Williamset al.2000 (unpublished), Blalock-Herodet al.2002, Blalock-Herodet al.2005, Pilarczyket al.2006, and Gangloff, and Hartfield 2009. In addition, a status survey was conducted in 2010-2012 by M.M. Gangloff and the final report is in preparation. These studies represent a compilation of museum records and recent status surveys conducted between 1990 and 2007. We also used various other sources to identify the historical and current locations occupied by these species. These include surveys, reports, and field notes prepared by biologists from the Alabama Department of Conservation and Natural Resources, Marion, AL; Geological Survey of Alabama, Tuscaloosa, AL; Florida Fish and Wildlife Conservation Commission, Gainesville, FL; U.S. Geological Survey, Gainesville, FL; Alabama Malacological Research Center, Mobile, AL; Troy University, Troy, AL; Appalachian State University, Boone, NC; various private consulting groups; and the U.S. Fish and Wildlife Service, Daphne, AL, and Panama City, FL. In addition, we obtained occurrence data from the collection databases of the Museum of Fluviatile Mollusks (MFM), Athearn collection; Auburn University Natural History Museum (AUNHM),Auburn, AL; and Florida Museum of Natural History (FLMNH), Gainesville, FL.

Assessing Status

Assessing the state of a freshwater mussel population is challenging. We looked at trends in distribution (range) by comparing recent occurrence data to historical data, and we examined recent abundance (numbers). One difficulty of investigating population trends over time in these species is the lack of historical collection data within the drainages. Athearn (1964, p. 134) noted the streams of western Florida were inadequately sampled, particularly the lower Choctawhatchee, Yellow, and the lower Escambia Rivers. Blalock-Herodet al.(2005, p. 2) stated that little collecting effort had been expended in the Choctawhatchee River drainage as compared to other nearby river systems like the Apalachicola and Mobile river drainages. This paucity of historical occurrence data may create the appearance of an increase in the number of localities that support a species or an expanding range; however, this is likely due to increased sampling efforts and to better sampling methods, like the use of SCUBA gear.

Another difficulty is the lack basic information for some historical collections, including specific locality, total number of species or individuals collected, or collection date. For these reasons, the only accurate comparison that can be made of so many different sources of historical and recent collection data is whether a particular species was detected (present) or not (absent) during the survey. When examining occurrence data, we considered sampled areas in close proximity as the same sight. Generally, areas sampled that are within 2 river km (1.2 mi) (approximately) of each other are considered the same site, and sampled areas that are more than 2 km apart are considered different sites. Occurences are based on live animals and shell material. The occurrence data we examined using GIS mapping software. A summary historical and recent occurrence data, and current abundance is presented in Table 1.

Table 1—Eight Mussel Occurrence and Abundance by River Drainage—Occurrences Are Based on Live and Shell Material and Abundance Is Based on Live Individuals Species Drainage Historical (pre-1995) Historical sites Historical sites re-
  • surveyed
  • Historical sites
  • currently
  • occupied
  • Current (1995-2012) Current sites1 Total live collected Average abundance2 General
  • assessment
  • Margaritifera marrianaeAlabama pearlshell Alabama 3 3 0 0 0 0 Contracted range, limited distribution, very low numbers. Escambia 12 12 4 9 28 3.14 Fusconaia rotulataround ebonyshell Escambia 3 2 2 11 8 1.1 Limited distribution, very low numbers. Ptychobranchus jonesisouthern kidneyshell Escambia 10 5 0 0 0 0 Contracted range, limited distribution, very low numbers. Yellow 1 1 0 0 0 0 Choct 12 11 1 10 41 2.5 Villosa choctawensisChoctaw bean Escambia 7 7 1 7 14 1.4 Fragmented populations (Escambia), localized extirpations, low numbers. Yellow 4 3 2 4 15 3.0 Choct 11 10 3 37 143 3.9 Fusconaia burkeitapered pigtoe Choct 23 22 13 53 361 6.0 Limited distribution, localized extirpations. Fusconaia escambianarrow pigtoe Escambia 13 10 7 28 166 6.9 Localized extirpations, limited distribution, low numbers. Yellow 2 2 1 4 23 2.9 Hamiota australissouthern sandshell Escambia 6 4 1 6 20 4 Localized extirpations. Yellow 5 4 2 17 65 3.1 Choct 18 16 5 34 211 4.5 Pleurobema strodeanumfuzzy pigtoe Escambia 30 18 12 26 52 6.5 Nearly extirpated from Yellow drainage, localized extirpations. Yellow 4 4 1 1 1 1 Choct 18 15 8 59 587 9.9 1Includes all currently occupied sites, both historic and new. 2Average number of live individuals collected per site.

    We also considered each species' relative abundance in comparison to other mussel species with which they co-occur. In addition, we relied on various published documents whose authors are considered experts on these species. These publications either described the status of these species or assigned a conservation ranking, and include Williamset al.1993, Williams and Butler 1994; Mirarchiet al.2004, Blalock-Herodet al.2005, and Williamset al.2008.

    Most of the eight species have experienced a decline in populations and numbers of individuals within populations, but not all have experienced a decline in range. Recent, targeted surveys for the Alabama pearlshell and southern kidneyshell show a dramatic decline in historical range. The Choctaw bean, narrow pigtoe, fuzzy pigtoe, southern sandshell, and tapered pigtoe still occur in much of their historical range; however, they no longer occur at many locations at which they were historically known, and their numbers appear to be declining. The round ebonyshell's current range is larger than its historical range, but this is attributed to the use of dive equipment in recent surveys that allowed access to the species' deep, main channel habitat. Despite this range extension, the species still has a very limited distribution and is considered to be extremely rare.

    Taxonomy, Life History, and Distribution Alabama Pearlshell

    The Alabama pearlshell (Margaritifera marrianae,Johnson 1983) is a medium-sized freshwater mussel known from a few tributaries of the Alabama and Escambia River drainages in south-central Alabama (Johnson 1983, pp. 299-304; McGregor 2004, p. 40; Williamset al.2008, pp. 98-99). The pearlshell is oblong and grows up to 95 millimeters (mm) (3.8 inches (in)) in length. The outside of the shell (periostracum) is smooth and shiny and somewhat roughened along the posterior slope. The inside of the shell (nacre) is whitish or purplish and moderately iridescent (refer to Johnson 1983 for a full description).

    The Alabama pearlshell is one of five North American species in the family Margaritiferidae. The family is represented by only two genera,Margaritifera(Schumacher 1816) andCumberlandia(Ortmann 1912). In Alabama, each genus is represented by a single species—the spectaclecase (Cumberlandia monodonta) occurs in the Tennessee River Basin (Williamset al.2008, pp. 94-95), and the Alabama pearlshell occurs in the Escambia and Alabama river basins in south Alabama. Prior to 1983, the Alabama pearlshell was thought to be the same species as the Louisiana pearlshell (Margaritifera hembeliConrad 1838) (Simpson 1914; Clench and Turner 1956), a species now considered endemic to central Louisiana.

    The Alabama pearlshell typically inhabits small headwater streams with mixed sand and gravel substrates, occasionally in sandy mud, with slow to moderate current. Very little is known about the life-history requirements of this species. However, Shelton (1995, p. 5 unpub. report) suggests that the Alabama pearlshell, as opposed to the Louisiana pearlshell, which occurs in large colonies, typically occurs in low numbers. The Alabama pearlshell is also believed to occur in male-female pairs. Of the 68 Alabama pearlshell observed by Shelton (1995, p. 5 unpub. report), 85 percent occurred in pairs. Males were always located upstream of the females and were typically not more than 1 meter (m) apart, and juveniles were usually found just a few inches apart. The species is believed to be a long-term brooder, where gravid females have been observed in December. The host fish and other aspects of its life history are currently unknown.

    Historically, the Alabama pearlshell occurred in portions of the Escambia River drainage, and has also been reported from two systems in the Alabama River drainage. The Alabama pearlshell's known historical and current occurrences, by water body and county, are shown in Table 2 below.

    Table 2—Water Bodies With Known Historical and Current Occurrences of the Alabama Pearlshell Water body Drainage County State Historical or current Big Flat Creek Alabama Monroe AL Historical and Current. Brushy Creek Alabama Monroe AL Historical. Limestone Creek Alabama Monroe AL Historical. Amos Mill Creek Escambia Conecuh, Escambia AL Current. Autrey Creek Escambia Conecuh AL Historical. Beaver Creek Escambia Conecuh AL Historical. Bottle Creek Escambia Conecuh AL Historical and Current. Brushy Creek Escambia Conecuh AL Historical. Burnt Corn Creek Escambia Conecuh AL Historical and Current. Horse Creek Escambia Crenshaw AL Historical. Hunter Creek Escambia Conecuh AL Historical and Current. Jordan Creek Escambia Conecuh AL Historical and Current. Little Cedar Creek Escambia Conecuh AL Historical and Current. Murder Creek Escambia Conecuh AL Historical. Otter Creek Escambia Conecuh AL Historical and Current. Sandy Creek Escambia Conecuh AL Historical and Current.

    The Amos Mill population, discovered in 2010, represents a new record, and possibly the only known surviving population in the Sepulga River drainage. The Burnt Corn and Otter Creek populations reaffirm historical records that had not been reported in nearly 30 years. Two of the Sandy Creek locations, discovered in 2011, are new populations. Since the late 1990s, more than 70 locations within the Alabama River Basin were surveyed for mollusks (McGregoret al.1999, pp. 13-14; Powell and Ford 2010 pers. obs.; Buntin and Fobian 2011 pers. comm.), 35 of which were located in the Limestone and Big Flat Creek drainages, and no live Alabama pearlshell were reported. The last documented occurrence in Big Flat Creek was a fresh dead individual collected in 1995 (Shelton 1999 in litt.), and the last reported occurrence in the Limestone Creek drainage was 1974, where Williams (2009 pers. comm.) reported it as common. Despite numerous visits, the pearlshell has not been collected in this system since 1974. A fresh dead individual collected by Shelton in 1995,

    represents the most recent record from the Big Flat Creek drainage.

    Recent data suggest that, of the nine remaining populations, the largest may occur in Little Cedar and Otter Mill creeks. In 2011, Fobian and Pritchett reported new populations at two locations in an unnamed tributary to Sandy Creek. Although this is not the first report from the Sandy Creek basin, it is the first for the two unnamed tributaries. In 2010, Buntin and Fobian (2011 pers. comm.) reported 10 live individuals from Otter Creek. This is the first time since 1981 that the pearlshell has been reported from this drainage. Also in 2010, Powell and Ford reported three live individuals, and several relic shells, from Amos Mill Creek, in Escambia County, AL. This is the first report of the pearlshell from this drainage, and county, and the first live individual from the Sepulga River system in nearly 50 years. Little Cedar Creek supported good numbers of Alabama pearlshell in the late 1990's (54 individuals reported in 1998). However, during a qualitative search of the same area in 2005, only two live pearlshell were found (Powell 2005 pers. obs.), and in 2006, three live pearlshells were observed (Johnson 2006 in litt.). Live Alabama pearlshell have not been observed in Hunter Creek since 1998, when eight live individuals were reported (Shelton 1999 in litt.). During two visits to the stream in 1999, Shelton found no evidence of the species (Shelton 1999in litt.), and reported high levels of sedimentation. However, in 2005 the shells of three fresh dead Alabama pearlshells were reported from Hunter Creek, indicating the persistence of the species in that drainage (Powell, pers. obs. 2005).

    Evidence suggests that much of the rangewide decline of this species has occurred within the past few decades. Specific causes of the decline and disappearance of the Alabama pearlshell from historical stream localities are unknown. However, they are likely related to past and present land use patterns. Many of the small streams historically inhabited by the Alabama pearlshell are impacted to various degrees by nonpoint-source pollution.

    Round Ebonyshell

    The round ebonyshell (Fusconaia rotulata,Wright 1899) is a medium-sized freshwater mussel endemic to the Escambia River drainage in Alabama and Florida (Williamset al.2008, p. 320). The round ebonyshell is round to oval in shape and reaches about 70 mm (2.8 in.) in length. The shell is thick and the exterior is smooth and dark brown to black in color. The shell interior is white to silvery and iridescent (Williams and Butler 1994, p. 61; Williamset al.2008, p. 319). The round ebonyshell was originally described by B.H. Wright in 1899 and placed in the genusUnio.Simpson (1900) reexamined the type specimen and assigned it to the genusObovaria.Based on shell characters, Williams and Butler (1994, p. 61) recognized it as clearly a species of the genusFusconaia,and its placement in the genus is supported genetically (Lydeardet al.2000, p. 149).

    Very little is known about the habitat requirements or life history of the round ebonyshell. It occurs in small to medium rivers, typically in stable substrates of sand, small gravel, or sandy mud in slow to moderate current. It is believed to be a short-term brooder, and gravid females have been observed in the spring and summer. The fish host(s) for the round ebonyshell is currently unknown (Williamset al.2008, p. 320).

    The round ebonyshell is known only from the main channel of the Escambia-Conecuh River and is the only mussel species endemic to the drainage (Williamset al.2008, p. 320). Due to recent survey data, its known range was extended downstream the Escambia River to Molino, Florida (Gangloff 2012 pers. comm.), and upstream in the Conecuh River to just above the Covington County line in Alabama (Williamset al.2008, p. 320). The round ebonyshell's known historical and current occurrences, by water body and county, are shown in Table 3 below.

    Table 3—Water Bodies With Known Historical and Current Occurrences of the Round Ebonyshell Water body Drainage County State Historical or current Conecuh River Escambia Escambia, Covington AL Historical and Current. Escambia River Escambia Escambia, Santa Rosa FL Historical and Current.

    The round ebonyshell has a very restricted distribution (Williams and Butler 1994, p. 61), with its current range (based on live individuals and shell material) confined to approximately 144 km (89 mi) of the Escambia-Conecuh River main channel. The round ebonyshell is also considered to be extremely rare (Williamset al.2008, p. 320). Researchers collected a total of three live individuals during a 2006 dive survey (Sheltonet al.2007, pp. 8-10 unpub. report), and 4 more were collected during a dive survey in 2011 (Gangloff 2012 pers. comm). At stations where the species was present in the 2011 survey, 219 mussels were collected for every 1 round ebonyshell. Because its distribution is limited to the main channel of one river, the round ebonyshell is particularly vulnerable to catastrophic events such as flood scour and contaminant spills, and to activities that cause streambed destabilization like gravel mining, dredging, and de-snagging for navigation. Due to its limited distribution and rarity, McGregor (2004, p. 56) considered the round ebonyshell vulnerable to extinction, and classified it as a species of highest conservation concern in Alabama. Williamset al.(1993, p. 11) considered the round ebonyshell as endangered throughout its range.

    Southern Kidneyshell

    The southern kidneyshell (Ptychobranchus jonesi,van der Schalie 1934) is a medium-sized freshwater mussel known from the Escambia and Choctawhatchee River drainages in Alabama and Florida, and the Yellow River drainage in Alabama (Williamset al.2008, p. 624). The southern kidneyshell is elliptical and reaches about 72 mm (2.8 in.) in length. Its shell is smooth and shiny, and greenish yellow to dark brown or black in color, sometimes with weak rays. The shell interior is bluish white with some iridescence (Williams and Butler 1994, p. 126; Williamset al.2008, p. 624). The southern kidneyshell was described by H. van der Schalie (1934) asLampsilis jonesi.Following the examination of gills of gravid females, Fuller and Bereza (1973, p. 53) determined it belonged in the genusPtychobranchus.When gravid, the marsupial gills form folds along the outer edge, a characteristic unique to the genusPtychobranchus(Williamset al.2008, p. 609).

    Very little is known about the habitat requirements or life history of the southern kidneyshell. It is typically found in medium creeks to small rivers in firm sand substrates with slow to moderate current (Williamset al.2008,pp. 625). A recent status survey in the Choctawhatchee basin in Alabama found its preferred habitat to be stable substrates near bedrock outcroppings (Gangloff and Hartfield 2009, p. 25). The southern kidneyshell is believed to be a long-term brooder, with females gravid from autumn to the following spring or summer. Preliminary reproductive studies found that females release their glochidia in small conglutinates that are bulbous at one end and tapered at the other (Alabama Aquatic Biodiversity Center 2006, unpub. data). Host fish for the southern kidneyshell are currently unknown; however, darters serve as primary glochidial hosts to other members of the genusPtychobranchus(Luo 1993, p. 16; Haag and Warren 1997, p. 580).

    The southern kidneyshell is endemic to the Escambia, Choctawhatchee, and Yellow River drainages in Alabama and Florida (Williamset al.2008, p. 624), but is currently known only from the Choctawhatchee River drainage. The southern kidneyshell's known historical and current occurrences, by water body and county, are shown in Table 4 below.

    Table 4—Water Bodies With Known Historical and Current Occurrences of the Southern Kidneyshell Water body Drainage County State Historical or current Burnt Corn Creek Escambia Escambia AL Historical. Jordan Creek Escambia Conecuh AL Historical. Sepulga River Escambia Conecuh AL Historical. Conecuh River Escambia Covington, Crenshaw AL Historical. Patsaliga Creek Escambia Covington, Crenshaw AL Historical. Little Patsaliga Creek Escambia Crenshaw AL Historical. Hollis Creek Yellow Covington AL Historical. Choctawhatchee River Choctawhatchee Walton FL Historical. Sandy Creek Choctawhatchee Walton FL Historical. Holmes Creek Choctawhatchee Washington FL Current. Choctawhatchee River Choctawhatchee Geneva, Dale AL Historical and Current. Pea River Choctawhatchee Geneva, Coffee, Dale, Pike, Barbour AL Historical and Current. Flat Creek Choctawhatchee Geneva AL Historical. Whitewater Creek Choctawhatchee Coffee AL Historical. West Fork Choctawhatchee River Choctawhatchee Dale, Barbour AL Historical and Current. East Fork Choctawhatchee River Choctawhatchee Dale, Henry AL Historical.

    Since 1995, the southern kidneyshell has been detected at only 10 locations within the Choctawhatchee River drainage. The species appears to have been common historically (in 1964, H. D. Athearn collected 98 individuals at one site on the West Fork Choctawhatchee), but it is currently considered one of the most imperiled species in the United States (Blalock-Herodet al.2005, p. 16; Williamset al.2008, p. 625). In addition to a reduction in range, its numbers are very low. A 2006-2007 status survey in the Alabama portion of the Choctawhatchee basin found the southern kidneyshell was extremely rare. A total of 13 were encountered alive, and the species comprised less than 0.3 percent of the total mussel assemblage (Gangloff and Hartfield 2009, p. 249). It is classified as a species of highest conservation concern in Alabama by McGregor (2004, p. 83), and considered threatened throughout its range by Williamset al.(1993, p. 14)

    Choctaw Bean

    The Choctaw bean (Villosa choctawensis,Athearn 1964) is a small freshwater mussel known from the Escambia, Yellow, and Choctawhatchee River drainages of Alabama and Florida. The oval shell of the Choctaw bean reaches about 49 mm (2.0 in.) in length, and is shiny and greenish-brown in color, typically with thin green rays, though the rays are often obscured in darker individuals. The shell interior color varies from bluish white to smoky brown with some iridescence (Williams and Butler 1994, p. 100; Williamset al.2008, p. 758). The sexes are dimorphic, with females truncate or widely rounded posteriorly, and sometimes slightly more inflated (Athearn 1964, p. 137). The Choctaw bean was originally described by H.D. Athearn in 1964.

    Very little is known about the habitat requirements or life history of the Choctaw bean. It is found in medium creeks to medium rivers in stable substrates of silty sand to sandy clay with moderate current. It is believed to be a long-term brooder, with females gravid from late summer or autumn to the following summer. Its fish host is currently unknown (Williamset al.2008, p. 758).

    The Choctaw bean is known from the Escambia, Yellow, and Choctawhatchee River drainages in Alabama and Florida (Williamset al.2008, p. 758). The Choctaw bean's known historical and current occurrences, by water body and county, are shown in Table 5 below.

    Table 5—Water Bodies With Known Historical and Current Occurrences of the Choctaw Bean Water body Drainage County State Historical or current Escambia River Escambia Escambia, Santa Rosa FL Historical and Current. Burnt Corn Escambia Conecuh AL Current. Murder Creek Escambia Conecuh AL Historical. Pigeon Creek Escambia Butler AL Historical. Patsaliga Creek Escambia Crenshaw AL Historical and Current. Little Patsaliga Creek Escambia Crenshaw AL Historical. Olustee Creek Escambia Pike AL Current. Conecuh River Escambia Crenshaw, Pike AL Current. Yellow River Yellow Okaloosa FL Historical and Current. Five Runs Creek Yellow Covington AL Historical and Current. Yellow River Yellow Covington AL Historical and Current. Choctawhatchee River Choctawhatchee Walton, Washington, Holmes FL Historical and Current. Holmes Creek Choctawhatchee Washington FL Current. Bruce Creek Choctawhatchee Walton FL Current. Wrights Creek Choctawhatchee Holmes FL Current. Choctawhatchee River Choctawhatchee Geneva, Dale AL Historical and Current. Pea River Choctawhatchee Geneva, Coffee, Pike, Barbour AL Historical and Current. Limestone Creek Choctawhatchee Walton FL Current. Flat Creek Choctawhatchee Geneva AL Current. Whitewater Creek Choctawhatchee Coffee AL Current. Pea Creek Choctawhatchee Barbour AL Current. Big Sandy Creek Choctawhatchee Bullock AL Current. Claybank Creek Choctawhatchee Dale AL Current. West Fork Choctawhatchee River Choctawhatchee Dale, Barbour AL Historical and Current. Judy Creek Choctawhatchee Dale AL Current. Pauls Creek Choctawhatchee Barbour AL Current. East Fork Choctawhatchee River Choctawhatchee Henry, Barbour AL Historical and Current.

    The Choctaw bean persists in most of its historic range. However, it has experienced localized extirpations and its numbers are low, particularly in the Escambia and Yellow river drainages. Of 7 historical sites known to support the species within the Escambia River drainage, 1 location currently supports the species. Also, its numbers within the drainage are very low; a total of 14 individuals have been collected since 1995. Within the Yellow River drainage, the Choctaw bean is currently known from 4 locations which yielded 15 individuals total. In the Choctawhatchee River drainage, 3 of 10 historical sites examined recently continue to support the species. The Choctaw bean continues to persist in most areas and is currently known from a total of 37 locations throughout the drainage.

    Heard (1975, p. 17) assessed the status of the Choctaw bean in 1975 and stated that it was formerly abundant in the main channel of the Choctawhatchee River in Florida, but has become quite rare. McGregor (2004, p. 103) considered the Choctaw bean vulnerable to extinction due to its limited distribution and habitat degradation, and classified it as a species of high conservation concern in Alabama. Williamset al.(1993, p. 14) considered the Choctaw bean as threatened throughout its range.

    Tapered Pigtoe

    The tapered pigtoe (Fusconaia burkei,Walker 1922) is a small to medium-sized mussel endemic to the Choctawhatchee River drainage in Alabama and Florida (Williamset al.2008, p. 296). The elliptical to subtriangular shell of the tapered pigtoe reaches about 75 mm (3.0 in.) in length, and is sculptured with plications (parallel ridges) that radiate from the posterior ridge. In younger individuals, the shell exterior is greenish brown to yellowish brown in color, occasionally with faint dark-green rays, and with pronounced sculpture often covering the entire shell; in older individuals, the shell becomes dark brown to black with age, and sculpture is often subtle. The shell interior is bluish white (Williamset al.2008, p. 295). The tapered pigtoe was described by B. Walker (in Ortmann and Walker 1922) asQuincuncina burkei,a new genus and species. In the description, Ortmann noted the species had gill features characteristic of the genusFusconaia;however, this was dismissed based on the presence of sculpture on the shell. Genetic analysis by Lydeardet al.(2000, p. 149) determined it to be a sister taxon toFusconaia escambia.Based on soft anatomy similarity, Williamset al.(2008, p. 296) recognizedburkeias belonging to the genusFusconaia.Recent molecular studies by Campbell and Lydeard (2012, p. 28) support the distinctiveness ofburkeias a species and its assignment to the genusFusconaia.

    The tapered pigtoe is found in medium creeks to medium rivers in stable substrates of sand, small gravel, or sandy mud, with slow to moderate current (Williamset al.2008, p. 296). The reproductive biology of the tapered pigtoe was studied by Whiteet al.(2008). It is a short-term brooder, with females gravid from mid-March to May. The blacktail shiner (Cyprinella venusta) was found to serve as a host for tapered pigtoe glochidia in the preliminary host trial (Whiteet al.2008, p. 122-123).

    The tapered pigtoe is endemic to the Choctawhatchee River drainage in Alabama and Florida (Williamset al.2008, p. 296). Its historical and current distribution includes several oxbow lakes in Florida, some with a flowing connection to the main channel. The tapered pigtoe's known historical and current occurrences, by water body and county, are shown in Table 6 below.

    Table 6—Water Bodies With Known Historical and Current Occurrences of the Tapered Pigtoe Water body Drainage County State Historical or current Pine Log Creek Choctawhatchee Washington, Bay FL Current. Choctawhatchee River Choctawhatchee Walton, Washington, Holmes FL Historical and Current. Crews Lake Choctawhatchee Washington FL Current. Crawford Lake Choctawhatchee Washington FL Historical. Horseshoe Lake Choctawhatchee Washington FL Historical. Holmes Creek Choctawhatchee Washington, Holmes, Jackson FL Historical and Current. Bruce Creek Choctawhatchee Walton FL Current. Sandy Creek Choctawhatchee Walton FL Current. Blue Creek Choctawhatchee Holmes FL Current. Wrights Creek Choctawhatchee Holmes FL Current. Tenmile Creek Choctawhatchee Holmes FL Historical. West Pittman Creek Choctawhatchee Holmes FL Current. East Pittman Creek Choctawhatchee Holmes FL Historical and Current. Parrot Creek Choctawhatchee Holmes FL Current. Limestone Creek Choctawhatchee Walton FL Historical and Current. Eightmile Creek Choctawhatchee Walton FL Current. Flat Creek Choctawhatchee Geneva AL Historical and Current. Pea River Choctawhatchee Coffee, Dale, Pike, Barbour AL Historical and Current. Big Creek (Whitewater Creek tributary) Choctawhatchee Pike AL Current. Big Creek (Pea River tributary) Choctawhatchee Barbour AL Current. Pea Creek Choctawhatchee Barbour AL Current. Hurricane Creek Choctawhatchee Geneva AL Historical. Choctawhatchee River Choctawhatchee Dale AL Historical. Little Choctawhatchee River Choctawhatchee Dale, Houston AL Historical. Panther Creek Choctawhatchee Houston AL Historical. Bear Creek Choctawhatchee Houston AL Historical. West Fork Choctawhatchee River Choctawhatchee Dale, Barbour AL Historical and Current. Judy Creek Choctawhatchee Dale AL Current. Pauls Creek Choctawhatchee Barbour AL Current.

    The tapered pigtoe appears to be absent from portions of its historic range and found only in isolated locations (Blalock-Herodet al.2005, p. 17). The species was not detected at 9 of the 22 historical sites examined during recent status surveys. Most of those are in the middle portion of the drainage in Alabama, and the species appears to be declining in this portion of its range. The tapered pigtoe is currently known from a total of 53 locations within the Choctawhatchee River drainage. The species persists m