[Federal Register Volume 76, Number 194 (Thursday, October 6, 2011)]
[Proposed Rules]
[Pages 62166-62212]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-25471]



[[Page 62165]]

Vol. 76

Thursday,

No. 194

October 6, 2011

Part II





Department of the Interior





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Fish and Wildlife Service





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50 CFR Part 17





Endangered and Threatened Wildlife and Plants; 12-Month Finding on a 
Petition To List Texas Fatmucket, Golden Orb, Smooth Pimpleback, Texas 
Pimpleback, and Texas Fawnsfoot as Threatened or Endangered; Proposed 
Rule

  Federal Register / Vol. 76 , No. 194 / Thursday, October 6, 2011 / 
Proposed Rules  

[[Page 62166]]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R2-ES-2011-0079; MO 92210-0-0008 B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List Texas Fatmucket, Golden Orb, Smooth Pimpleback, 
Texas Pimpleback, and Texas Fawnsfoot as Threatened or Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list five mussel species in Texas as 
threatened or endangered and to designate critical habitat under the 
Endangered Species Act of 1973, as amended (Act). The five species are 
Texas fatmucket (Lampsilis bracteata), golden orb (Quadrula aurea), 
smooth pimpleback (Q. houstonensis), Texas pimpleback (Q. petrina), and 
Texas fawnsfoot (Truncilla macrodon). After review of all available 
scientific and commercial information, we find that listing these five 
mussel species is warranted. Currently, however, listing of these 
species is precluded by higher priority actions to amend the Federal 
Lists of Endangered and Threatened Wildlife and Plants. Upon 
publication of this 12-month petition finding, we will add these five 
species to our candidate species list. We will develop a proposed rule 
to list these species as our priorities allow. We will make any 
determination on critical habitat during development of the proposed 
listing rule. In any interim period, we will address the status of the 
candidate taxa through our annual Candidate Notice of Review.

DATES: The finding announced in this document was made on October 6, 
2011.

ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R2-ES-2011-0079. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, 1505 Ferguson Lane, Austin, TX 78754. Please 
submit any new information, materials, comments, or questions 
concerning this finding to the above address.

FOR FURTHER INFORMATION CONTACT: Gary Mowad, Texas State Administrator, 
U.S. Fish and Wildlife Service (see ADDRESSES); by telephone at 512-
927-3557; or by facsimile at 512-927-3592. If you use a 
telecommunications device for the deaf (TDD), please call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.) requires 
that, for any petition to revise the Federal Lists of Endangered and 
Threatened Wildlife and Plants that contains substantial scientific or 
commercial information that listing the species may be warranted, we 
make a finding within 12 months of the date of receipt of the petition. 
In this finding, we will determine that the petitioned action is: (1) 
Not warranted, (2) warranted, or (3) warranted, but the immediate 
proposal of a regulation implementing the petitioned action is 
precluded by other pending proposals to determine whether species are 
threatened or endangered, and expeditious progress is being made to add 
or remove qualified species from the Federal Lists of Endangered and 
Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires 
that we treat a petition for which the requested action is found to be 
warranted but precluded as though resubmitted on the date of such 
finding, that is, requiring a subsequent finding to be made within 12 
months. We must publish these 12-month findings in the Federal 
Register.

Previous Federal Actions

    This 12-month petition finding covers five species of mussels that 
are grouped together because of their overlapping or proximate ranges 
within the river basins of central Texas. The petitions for listing 
these five species were parts of two multi-species petitions, dated 
June 18, 2007, and October 9, 2008. The other species from those 
petitions, including other Texas mussels, will be considered in 
separate petition findings.
    On June 25, 2007, we received a formal petition dated June 18, 
2007, from Forest Guardians (now WildEarth Guardians), requesting that 
we: (1) Consider all full species in our Southwest Region ranked as G1 
or G1G2 by the organization NatureServe, except those that are 
currently listed, proposed for listing, or candidates for listing; and 
(2) List each species as either threatened or endangered with critical 
habitat. The petitioned group of species included four Texas mussels, 
two of which are included in this finding: the Texas fatmucket and 
golden orb. Two additional mussels from eastern Texas, the Texas 
heelsplitter (Potamilus amphichaenus) and Salina mucket (P. 
metnecktayi), were also included in this petition. The petition 
incorporated all analyses, references, and documentation provided by 
NatureServe in its online database at http://www.natureserve.org/ into 
the petition. Included in NatureServe was supporting information 
regarding the species' taxonomy and ecology, historical and current 
distribution, present status, and actual and potential causes of 
decline. We sent a letter dated July 11, 2007, to Forest Guardians 
acknowledging receipt of the petition and stating that the petition was 
under review by staff in our Southwest Regional Office.
    On October 15, 2008, we received a petition dated October 9, 2008, 
from WildEarth Guardians, requesting that the Service list as 
threatened or endangered and designate critical habitat for six species 
of freshwater mussels, including the smooth pimpleback, Texas 
pimpleback, and Texas fawnsfoot. Two additional mussels from the Rio 
Grande basin, the false spike (Quincuncina mitchelli) and Mexican 
fawnsfoot (Truncilla congata), were also included in this petition. In 
addition to other information, the petition incorporated all analyses, 
references, and documentation provided by NatureServe in its online 
database at http://www.natureserve.org/. In a November 26, 2008, letter 
to the petitioner, we acknowledged receipt of the second petition and 
stated that the petition for the six mussel species was under review by 
staff in our Southwest (Region 2) and Southeast (Region 4) Regional 
Offices. The southern hickorynut (Obovaria jacksoniana) was also 
included in this 2008 petition, and on March 23, 2010 (75 FR 13717), we 
found that the petition did not present substantial information 
supporting that that species may be endanagered or threatened.
    On December 15, 2009, we published our 90-day finding that the 
petitions presented substantial scientific information indicating that 
listing nine Texas mussels may be warranted (74 FR 66260). As a result 
of the finding, we initiated a status review for all nine species. This 
notice constitutes the 12-month finding on the June 18, 2007, petition 
to list the Texas fatmucket and golden orb and the October 9, 2008, 
petition to list the smooth pimpleback, Texas pimpleback, and Texas 
fawnsfoot as threatened or endangered. Our petition findings for the 
remaining Texas mussel species will be published at a later time.

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Summary of Procedures for Determining the Listing Status of Species

Review of Status Based on Five Factors
    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
(50 CFR part 424) set forth procedures for adding species to, removing 
species from, or reclassifying species on the Federal Lists of 
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of 
the Act, a species may be determined to be endangered or threatened 
based on any of the following five factors:
    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;
    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.
    In making these findings, we discuss below information pertaining 
to each species in relation to the five factors provided in section 
4(a)(1) of the Act. In considering what factors might constitute 
threats to a species, we must look beyond the exposure of the species 
to a particular factor to evaluate whether the species may respond to 
the factor in a way that causes actual impacts to the species. If there 
is exposure to a factor and the species responds negatively, the factor 
may be a threat, and during the status review, we attempt to determine 
how significant a threat it is. The threat is significant if it drives 
or contributes to the risk of extinction of the species such that the 
species warrants listing as endangered or threatened as those terms are 
defined by the Act. However, the identification of factors that could 
impact a species negatively may not be sufficient to compel a finding 
that the species warrants listing. The information must include 
evidence sufficient to suggest that the potential threat has the 
capacity (i.e., it should be of sufficient magnitude and extent) to 
affect the species' status such that it meets the definition of 
endangered or threatened under the Act.
Evaluation of the Status of Each of the Five Mussel Species
    In this finding, we first provide a description of general mussel 
biology. Then, for each of the five species, we describe the species, 
its life history, and habitat; evaluate listing factors for that 
species; and present our finding that the petitioned action is 
warranted or not for that species. We follow these descriptions, 
evaluations, and findings with a discussion of the priority and 
progress of our listing actions.

General Mussel Biology

    All five species are freshwater mussels in the family Unionidae and 
occur only in Texas, in portions of the Colorado, Guadalupe, Nueces-
Frio, and Brazos River systems (Howells et al. 1996, p. 1). Adult 
freshwater mussels are suspension feeders, drawing in food and oxygen 
through their incurrent siphon (tube that draws water into the shell). 
They may also feed on organic particles in sediment using the large, 
muscular foot (an organ used to anchor the mussel in the substrate or 
for locomotion) (Raikow and Hamilton 2001, p. 520). Adults feed on 
algae, bacteria, detritus (dead organic material), microscopic animals, 
and dissolved organic matter (Fuller 1974, pp. 221-222; Silverman et 
al. 1997, p. 1862; Nichols and Garling 2000, pp. 874-876; Christian et 
al. 2004, p. 109). For their first several months, as they inhabit 
interstitial spaces (small spaces between sediment particles) within 
the substrate, juvenile mussels feed using cilia (fine hairs) on the 
foot to capture suspended as well as depositional material, such as 
algae and detritus (Yeager et al. 1994, pp. 253-259). Mussels tend to 
grow relatively rapidly for the first few years, and then slow 
appreciably at sexual maturity, when energy presumably is being 
diverted from growth to reproductive activities (Baird 2000, pp. 66-
67).
    As a group, mussels are extremely long lived, living from two to 
several decades (Rogers et al. 2001, p. 592), and possibly up to 200 
years in extreme instances (Bauer 1992, p. 427). Most mussel species, 
including the five in this finding, have distinct forms of males and 
females. During reproduction, males release clouds of sperm into the 
water column, which females draw in through their siphons. 
Fertilization takes place internally, and the resulting eggs develop 
into specialized larvae (called glochidia) within the female gills. The 
females release matured glochidia individually, in small groups, or 
embedded in larger mucus structures called conglutinates.
    The glochidia of freshwater mussels are obligate parasites (cannot 
live independently of their hosts) on the gills or fins of fishes 
(Vaughn and Taylor 1999, p. 913). Glochidia die if they fail to find a 
host fish, attach to a fish that has developed immunity from prior 
infestations, or attach to the wrong location on a host fish (Neves 
1991, p. 254; Bogan 1993, p. 299). Glochidia encyst (enclose in a cyst-
like structure) on the host's tissue and develop into juvenile mussels 
weeks or months after attachment (Arey 1932, pp. 214-215). Mussels 
experience their primary opportunity for dispersal and movement within 
the stream as glochidia attached to a host fish (Smith 1985, p. 105). 
Upon release from the host, newly transformed juveniles drop to the 
substrate on the bottom of the stream. Those juveniles that drop in 
unsuitable substrates die because their immobility prevents them from 
relocating to more favorable habitat. Juvenile freshwater mussels 
burrow into interstitial substrates and grow to a larger size that is 
less susceptible to predation and displacement from high flow events 
(Yeager et al. 1994, p. 220). Throughout the rest of their life cycle, 
mussels generally remain within the same small area where they released 
from the host fish.

Species Information for Texas Fatmucket

Species Description

    The Texas fatmucket is a large, elongated mussel that reaches a 
maximum length of 100 millimeters (mm) (3.94 inches (in)) (Howells 
2010c, p. 2). The shell is oval to elliptical or somewhat rhomboidal 
and tan to greenish-yellow with numerous irregular, wavy, and broad and 
narrow dark brown rays, with broad rays widening noticeably as they 
approach the ventral (underside) margin. The nacre (inside of the 
shell) is white with occasional yellow or salmon coloration and 
iridescent posteriorly (Howells 2010c, p. 2). Females have mantle flaps 
(extensions of the tissue that covers the visceral mass) that often 
resemble minnows, including eye spots, lateral line, and fins (Howells 
2010c, p. 2).

Taxonomy

    The Texas fatmucket was first described in 1855 by Gould as Unio 
bracteatus and later moved to the genus Lampsilis by Simpson (1900, p. 
543). Some forms found in headwater streams were historically split 
into a different species, L. elongatus, but they have since been 
determined to be ecophenotypes (individuals whose shape is determined 
by their environment) of L. bracteata (Howells 2010c, p. 5). The Texas 
fatmucket is recognized by the Committee on Scientific and Vernacular 
Names of Mollusks of the Council of Systematic Malacologists, American 
Malacological Union (Turgeon et al. 1998, p. 34), and we recognize it 
as a valid species.

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Biology and Life History

    Although there is no specific information on age and size of 
maturity of the Texas fatmucket, it is likely similar to a related 
species, the Louisiana fatmucket (L. hydiana), which reaches sexual 
maturity around 36 mm (1.4 in) (Howells 2000b, pp. 35-48; Howells 
2010c, p. 3). Texas fatmucket females have been found gravid (with 
glochidia in the gill pouch) from July through October, although 
brooding may continue throughout much of the year (Howells 2010c, p. 
3). Texas fatmucket females display a mantle lure to attract host fish, 
releasing glochidia when the lure is bitten or struck by the fish. 
Bluegill (Lepomis macrochirus) and green sunfish (L. cyanellus) have 
been successful hosts in laboratory studies (Howells 1997b, p. 257). 
Hosts such as these sunfishes are common, widely distributed species in 
Texas that occur in an array of habitat types (Hubbs et al. 2008, p. 
45) and would not generally be expected to be a limiting factor in 
Texas fatmucket reproduction and distribution (Howells 2010c, p. 3).

Habitat

    The Texas fatmucket occurs in moderately sized rivers in mud, sand, 
or gravel, or mixtures of these substrates (Howells 2010c, p. 4) and 
sometimes in narrow crevices between bedrock slabs (Howells 1995, p. 
21). Live individuals have been found in relatively shallow water, 
rarely more than 1.5 meters (m) (4.9 feet (ft)) deep, and usually less. 
Remaining populations typically occur at sites where one or both banks 
are relatively low, allowing floodwaters to spread out over land and 
thereby reducing damage from scouring (Howells 2010c, p. 4). The 
species does not occur in ponds, lakes, or reservoirs, suggesting that 
it is intolerant of deep, low-velocity water created by artificial 
impoundments.

Distribution and Abundance

Historical Distribution
    The Texas fatmucket historically had populations in at least 18 
rivers in the upper Colorado, Guadalupe, and San Antonio River systems 
in the Texas Hill Country and east-central Edwards Plateau region of 
central Texas. In the Colorado River, it ranged from Travis County 
upstream approximately 320 kilometers (km) (200 miles (mi)) to Runnels 
County in the Colorado River. It was also found in many tributaries, 
including the Pedernales, Llano, San Saba, and Concho Rivers, and Jim 
Ned, Elm, and Onion Creeks (Howells et al. 1996, p. 61).
    In the Guadalupe-San Antonio River basin, the Texas fatmucket 
occupied approximately 240 km (150 mi) of the Guadalupe River, from 
Gonzales County upstream to Kerr County, including the North Guadalupe 
River, Johnson Creek, and the Blanco River. In the San Antonio River, 
it ranged from its confluence with the Medina River in Bexar County 
upstream to the City of San Antonio, as well as in the Medina River and 
Cibolo Creek (Howells et al. 1996, p. 61; Howells 2010c, p. 6). 
Strecker (1931, pp. 66-68) reported Texas fatmucket from a lake in 
Victoria County in the lower Guadalupe River drainage (Howells 2010c, 
p. 6), but this is probably a misidentified Louisiana fatmucket, which 
occurs in lakes or impoundments. A Salado Creek record from Bell County 
(Strecker 1931, pp. 62-63) is also probably a misidentified Louisiana 
fatmucket, since the Texas fatmucket is not known to occur in the 
Brazos River basin or its western tributaries (Howells et al. 1996, p. 
61; Howells 2010c, p. 6).
Current Distribution
    Based on historical and current data, the Texas fatmucket has 
declined significantly rangewide and is now known from only nine 
streams in the Colorado and Guadalupe River systems in very limited 
numbers. All existing populations are represented by only one or two 
individuals and are likely not stable or recruiting (juvenile mussels 
joining the adult population). In the streams where the species is 
extant (surviving), populations are highly fragmented and restricted to 
short reaches with few exceptions. The Texas fatmucket has been 
considered a species of special concern by some malacologists for 
several decades (Athearn 1970, p. 28).
Colorado River System
    The Texas fatmucket was historically known to occur throughout the 
Colorado River and numerous tributaries (Randklev et al. 2010c, p. 4). 
However, in the mainstem Colorado River, the Texas fatmucket has not 
been found, live or dead, in several decades despite numerous surveys 
(Howells 1994, p. 4; 1995, pp. 20-21, 25, 29; 1996, pp. 20, 23; 1997a, 
pp. 27, 31, 34-35; 1998, p. 10; 1999, p. 18; 2000a, pp. 25-27; 2002a, 
pp. 6-7; 2004, pp. 7, 10-11; 2005, p. 6; Johnson 2009, p. 1; Burlakova 
and Karatayev 2010a, p. 12), and thus is considered extirpated 
(eliminated from) from the Colorado River mainstem. Within this system, 
the species is only known from sparse populations in Colorado River 
tributaries, including the South Concho River, Spring Creek, Llano 
River (including Threadgill Creek), Pedernales River (including Live 
Oak Creek), Onion Creek, Jim Ned Creek, Elm Creek, and the San Saba 
River.
    Evidence of persisting Texas fatmucket populations has been found 
in Spring Creek, a tributary to the Middle Concho River, which flows 
into the Concho River, a large tributary of the Colorado River. 
Historically, Spring Creek harbored Texas fatmucket in Irion and Tom 
Green Counties (Randklev et al. 2010c, p. 1). In 1993, discovery of 
shell material prompted additional surveys, and in 1997, one live 
individual was found in Irion County (Howells 1998, p. 13). Farther 
downstream, in Tom Green County, two live individuals were recorded in 
1997, upstream of Twin Buttes Reservoir (Howells 1998, pp. 13-14), but 
no evidence of this population was found in 2008 (Burlakova and 
Karatayev 2010a, p. 12). Spring Creek was reported to have dried in 
1999 and 2000, which may have eliminated the population there (Howells 
et al. 2003, p. 5).
    In the Llano River, there are three areas that are currently known 
to contain Texas fatmucket populations. The species occurred throughout 
the length of the river historically (Ohio State University Museum 
(OSUM) 2011a, p. 1). A single shell was collected in Llano County in 
1992 (Howells 1994, p. 6), and eight live individuals were found in 
2011 (Burlakova and Karatayev 2011, p. 1). Individuals were small in 
size, indicating a potentially reproducing population. The species also 
persists in Mason County, where two shell fragments of recently dead 
Texas fatmucket were found in 1995 (Howells 1996, p. 22), and two live 
individuals were collected at the same site in 2009 (Burlakova and 
Karatayev 2010a, pp. 12-13). The species also appears to persist in 
Kimble County, where one live Texas fatmucket was recorded in 2009 
(Burlakova and Karatayev 2010a, pp. 12-13).
    In 2004, four live Texas fatmucket were recorded from Threadgill 
Creek, a tributary to the Llano River in Gillespie and Mason Counties 
(Howells 2005, pp. 6-7). This population is on private land, which 
limits survey access, but Howells (2009, p. 5) indicates it likely 
persists due to favorable land management.
    Live Oak Creek, a tributary to the Pedernales River in Gillespie 
County, also contains a sparse Texas fatmucket population. In 2002, 11 
shells were discovered, and in 2003, one live individual was recorded, 
confirming the species persisted in low numbers (Howells 2003, p. 10; 
Howells 2004, pp. 8-9). Since that time, surveys have been

[[Page 62169]]

conducted in Live Oak Creek on a fairly regular basis. The stream was 
visited in two different occasions in 2004, with only shell material 
found (Howells 2005, pp. 7-8), and again in 2005, when two live 
individuals were recorded (Burlakova and Karatayev 2010a, p. 12). The 
stream was surveyed in 2007 and 2008, but no evidence of the species 
was found (Howells 2009, p. 5). This population is presumed to be small 
but persisting.
    Original records of speckled pocketbook (Lampsilis streckeri) from 
Onion Creek in Travis County in 1931 are now believed to have been 
misidentified; instead they represent records of Texas fatmucket 
(Howells 2010c, p. 6; Randklev et al. 2010c, p. 4). The stream was 
surveyed in 1993, and no live freshwater mussels were found (Howells 
1995, p. 28). However, in 2010, several live Texas fatmucket were found 
during a survey near Highway 71 (Groce 2011, pers. comm.), indicating 
the species persists there.
    Elm Creek, a tributary to the Colorado River, has been known to 
harbor a Texas fatmucket population since 1993, when 10 live 
individuals were recorded (Howells 1995, p. 21). Since that time, the 
population has declined, with two individuals found in 1995 (Howells 
1996, pp. 19-20), and no live individuals found in 2001 or 2005 
(Howells 2002a, p. 5; 2006, p. 63). In 2008, additional sites 
downstream of the known population were surveyed and one live 
individual was recorded after 15 person-hours of searching (Burlakova 
and Karatayev 2010a, p. 12), indicating that the species continues to 
persist in Elm Creek, although in very low numbers.
    Texas fatmucket also persist in the San Saba River, where the 
species has been known to occur historically (Randklev et al. 2010c, p. 
2; OSUM 2011a, p. 1). The river was surveyed in 1997, and three live 
individuals were found (Howells 1998, p. 16). In 2000 and 2004, no 
Texas fatmucket were found in this stretch of river (Howells 2001, p. 
29; Howells 2005, pp. 8-9). One live individual was found in 2005 
(Howells 2006, p. 64), and, in 2008, only one shell of a recently dead 
individual was found (Burlakova and Karatayev 2010a, p. 12). In 2005, 
the number of mussels of all species collected was about 40 percent of 
the 1997 numbers (Howells 2006, p. 64), indicating an overall decline 
in the freshwater mussel fauna. Aquatic macrophyte (aquatic plants 
larger than algae) abundance has increased in this river, confounding 
survey efforts and degrading mussel habitat (Howells 2006, p, 64).
    Texas fatmucket have not been found alive in the Pedernales River 
since 1978 (Howells 1999, p. 16). In 1992, a thorough search of the 
habitat yielded no live Texas fatmuckets, with only very old dead shell 
material collected in the banks above the normal high water line 
(Howells 1994, p. 4). Because the species was documented from Blanco 
County by museum records (OSUM 2011a, p. 1), additional sections of the 
river were also surveyed in 1992, with no evidence of Texas fatmucket 
found, although in 1993, very old Texas fatmucket shell fragments were 
discovered in Pedernales Falls State Park (Howells 1995, p. 28). Mussel 
habitat in this area is poor, and it is unlikely the species persists 
there. Subsequent searches of the river in 1998 yielded only dead shell 
material (Howells 1999, p. 16).
    The Texas fatmucket is considered extirpated from the South Concho 
River and Jim Ned Creek. In the South Concho River, old Texas fatmucket 
shell fragments were found in gravel bars in Tom Green County in 1997, 
but there has been no additional evidence of the species (Howells 1998, 
p. 12). Additionally, three live individuals were recorded from Jim Ned 
Creek in Brown County in 1979 (Randklev et al. 2010c, p. 3), but the 
species has not been found in this stream since then (Howells 1997a, 
pp. 29-30).
Guadalupe River System
    While the Texas fatmucket was never widely distributed in the 
Guadalupe River system, the only remaining populations are in the 
mainstem Guadalupe River and possibly the North Fork Guadalupe River. 
It is presumed extirpated from the entire San Antonio River system, as 
well as the Blanco River and Johnson Creek.
    In the mainstem Guadalupe River, Texas fatmucket historically 
occurred in Kerr County (OSUM 2011a, p. 1). In 1992 and 1995, surveys 
yielded no evidence of the species (Howells 1994, pp. 7-8; Howells 
1996, p. 25), although shell fragments collected in 1993 in Guadalupe 
County may have been Texas fatmucket but were too weathered for an 
accurate determination (Howells 1995, p. 31). In 1996, two live 
individuals were recorded in Kerr County directly below a dam (Howells 
1997a, p. 36), and in 1997, three shells were found at the same site 
following a flood (Howells 1998, p. 18). No Texas fatmucket or other 
freshwater mussels have been found at that site since, and it is 
unlikely that Texas fatmucket persist there (Howells 2006, p. 71). 
However, 20 recently dead individuals were discovered approximately 1 
km (0.6 mi) downstream in Louise Hayes Park during a drawdown (Howells 
1999, pp. 18-19), and 6 live individuals were found at the same 
location in 2005 (Howells 2006, pp. 71-72). Surveys in 2007 and 2008 
yielded no live or recently dead individuals (Burlakova and Karatayev 
2010a, p. 12). It is likely that the species persists in the vicinity. 
There has been no other evidence of Texas fatmucket in the mainstem 
Guadalupe River in recent years.
    In 1999, two recently dead Texas fatmucket were found in North Fork 
Guadalupe River (Howells 2000a, p. 27). This river was surveyed again 
in 2000 and 2003 at several sites, and no Texas fatmucket were found 
(Howells 2001, p. 31; Howells 2004, pp. 13-14).
    Johnson Creek was a historical location for Texas fatmucket, but no 
live freshwater mussels of any species have been found in this stream 
for decades (Howells 1996, p. 25; Howells 1998, p. 18; Howells 2002a, 
p. 8). Additionally, the Blanco River has been surveyed extensively 
since 1992, and no evidence of Texas fatmucket has been collected, nor 
is suitable habitat present (Howells 1994, p. 9; Howells 1995, pp. 32-
33; Howells 1996, p. 28; Johnson 2011, p. 1). The last collection of 
Texas fatmucket from the Blanco River occurred in the 1970s or 1980s 
(Howells 2005, p. 10).
    Texas fatmucket have also been extirpated from the entire San 
Antonio River system. The mainstem San Antonio River was surveyed in 
1993 and 1996, and no live or dead Texas fatmucket were found (Howells 
1995, p. 35; 1997a, pp. 41-42). It was known from the Medina River, a 
tributary to the San Antonio River, historically (Randklev et al. 
2010c, p. 3), but no mussels of any species have been found in this 
river in recent years (May 2011, pers. comm.). Additionally, although 
Texas fatmucket were collected from Cibolo Creek historically (OSUM 
2011a, p. 1) and shell material, likely from Texas fatmucket, was found 
in 1993 (Howells 1995, p. 36), no live freshwater mussels have been 
found in Cibolo Creek since (Howells 1997a, pp. 40-41).
Summary
    Based on historical and current data, the Texas fatmucket has 
declined significantly rangewide and has been extirpated from most of 
the Guadalupe River system and hundreds of miles of the Colorado River, 
as well as from numerous tributaries. Extant populations are 
represented by only a few individuals, and they are highly disjunct and 
restricted to short reaches. Two of the populations considered extant 
in recent years may now be

[[Page 62170]]

extirpated, and the remaining seven populations are extremely small and 
likely not stable. No evidence of recent recruitment has been found in 
any of the populations, with the possible exception of the Llano River.

Species Information for Golden Orb

Species Description

    The golden orb is small, usually less than 82 mm (3.2 in), with an 
oval to nearly round, smooth, and unsculptured shell, except for 
concentric growth rings (Howells 2002b, p. 6). External shell 
coloration varies from yellow-brown, gold, or orangish-brown to dark 
brown or black, and some individuals may show faint greenish rays. 
Internally, the nacre is white to bluish-white (Howells 2002b, p. 6).

Taxonomy

    The golden orb was originally described as Unio aureas by Lea in 
1859 and later moved to the genus Quadrula in 1900 (Simpson 1900, p. 
783). Graf and Cummings (2007, p. 18) have proposed moving it to the 
genus Amphinaias, but other freshwater mussel taxonomists recommend 
waiting for additional work to be completed on members of Quadrula 
before splitting the genus (Bogan 2011, pers. comm.). Because the 
golden orb can exhibit an elongated shell structure in headwater 
riffles, old records of Unio bolli in the Colorado River (Dall 1882, p. 
956) are very likely elongated forms of golden orb (Howells 2010a, p. 
5). The golden orb is recognized by the Committee on Scientific and 
Vernacular Names of Mollusks of the Council of Systematic 
Malacologists, American Malacological Union (Turgeon et al. 1998, p 
36), and we recognize it as a valid species.

Biology and Life History

    There is no specific information on age, size of maturity, or host 
fish use for golden orb. Other species in the genus Quadrula 
successfully parasitize catfish, and it is likely golden orb do as well 
(Howells 2010a, p. 3). Gravid females have been found from May through 
August (Howells 2000b, p. 38). Mussels in the genus Quadrula are short-
term brooders, which are species that hold fertilized eggs and 
glochidia for a short period, usually 3 to 6 weeks, before releasing 
glochidia (Gorden and Layzer 1989, p. 6; Garner et al. 1999, p. 277).

Habitat

    The golden orb has been found almost exclusively in flowing waters 
in moderately sized rivers (Howells 2010a, p. 3). It has been found in 
only one reservoir in the lower Nueces River (Lake Corpus Christi), 
where wave action may simulate flowing water conditions (Howells 2010a, 
p. 3). This species is found in substrates of firm mud, sand, and 
gravel, and it does not appear to tolerate more unstable substrates 
such as loose sand or silt (Howells 2002b, p. 6).

Distribution and Abundance

Historical Distribution
    The golden orb is endemic (native) to nearly the entire lengths of 
the Guadalupe, San Antonio, and Nueces-Frio River basins in central 
Texas (Howells 2010a, p. 5), including the Guadalupe, Medina, San 
Antonio, Frio, and Nueces Rivers and Cibolo Creek. It was originally 
reported from four sites in the Brazos River system (Strecker 1931, p. 
63), but these are almost certainly misidentified smooth pimpleback 
(Howells 2002b, p. 5) based on numerous mussel surveys throughout the 
Brazos River system since the 1970s that failed to find any golden orb. 
The species has not been found in studies of archaeological specimens 
from the Brazos River (Howells 2010a, p. 5), further indicating golden 
orb did not historically occur in the Brazos River system.
    The golden orb has also been reported from the upper Colorado River 
drainage (Howells et al. 1996, pp. 108-109; Randklev et al. 2010c, p. 
4), but these appear to have been misidentified Texas pimpleback 
(Howells 2010a, p. 5). Since no other golden orb have been reported 
from the Colorado River system, we do not believe it occurred in that 
basin.
Current Distribution
    Based on historical and current data, the golden orb has declined 
significantly rangewide and is now known from only four streams in 
disjunct locations. Despite mussel surveys across the historical range, 
since 1995 golden orb has only been found in Lake Corpus Christi and 
the Guadalupe, lower San Marcos, and lower San Antonio Rivers. The 
species has been extirpated from the entire Nueces-Frio River basin, 
except at the extreme downstream end of the Nueces River, where a 
population persists in Lake Corpus Christi. Aside from the upper 
Guadalupe River, all existing populations occur in the lower portion of 
occupied basins in a small geographical area; only about 130 km (80 mi) 
separate the farthest two populations. Only four populations appear to 
be relatively stable and recruiting, while the remaining five 
populations are represented by only a few individuals.
Guadalupe River System
    In the Guadalupe River system, the golden orb historically ranged 
throughout the length of the Guadalupe, San Antonio, and San Marcos 
Rivers. Currently in this basin, the species only persists in the 
uppermost Guadalupe River and lower San Marcos, San Antonio, and 
Guadalupe Rivers. The lower portion of this basin (within approximately 
120 km (75 mi) of the Gulf of Mexico) harbors all four of the large, 
presumably reproducing populations of golden orb.
    Historically known from the mainstem Guadalupe River (Howells 
2002a, p. 8), the golden orb was not seen in the upper Guadalupe River 
in Kerr County again, despite repeated surveys (Howells 1994, pp. 7-8; 
1996, p. 30; 1997a, p. 36), until 1997, when three shells were 
discovered (Howells 1998, p. 18). No live freshwater mussels of any 
species have been found in this area, just downstream of a dam, since 
1997 (Howells 1999, p. 18; Howells 2006, p. 71), and it is unlikely 
golden orb persists there. However, upstream of this area, above the 
dam and impounded reach, a single recently dead individual was found in 
1998 during an extended drawdown of the river to construct a footbridge 
in a local park (Howells 1999, pp. 18-19). In 2005, two live 
individuals were also found at this site (Howells 2006, pp. 71-72), 
showing that the species had survived the drawdown and persists at the 
site.
    Golden orb also occurs farther downstream in the mainstem Guadalupe 
River, near Lake Gonzales in Gonzales County. Upstream of the 
reservoir, subfossil shells (very old shells that are brittle, 
crumbling, and with extensive erosion) were found in 1993 (Howells 
1995, p. 31), but the species has not been found there since. However, 
below the reservoir, one recently dead individual was collected in 1995 
(Howells 1996, pp. 26-27), and in 1996, 25 live golden orb were 
recorded at two sites in this area (Howells 1997a, pp. 37-38). Later, 
in 2006, three live golden orb were also found in this area (Howells 
2006, pp. 85-86). A small population apparently continues to persist 
below Lake Gonzales.
    A large golden orb population occurs farther downstream in the 
mainstem Guadalupe River, below Lake Wood, also in Gonzales County. 
Although none were found during a survey in 1995 (Howells 1996, p. 27), 
36 live golden orb were found at two sites below Lake Wood in 1996 
(Howells 1997a, pp. 38-40). Density estimates were calculated based on 
the quantitative information collected from these surveys, but they

[[Page 62171]]

were not considered statistically valid (Howells 1997a, p. 40) and so 
are not reported here. Only one live golden orb was found at this site 
in 2002 (Howells 2003, p. 11), but a relatively large population 
continues to persist; a total of around 100 live golden orb were found 
at three sites within 2 km (1.2 mi) of the Lake Wood Dam in 2006 
(Howells 1996, pp. 87-91). Also, in 2008, 33 golden orb were recorded 
alive downstream of Lake Wood (Burlakova and Karatayev 2010a, p. 14). 
This portion of the Guadalupe River supports a relatively large 
population of golden orb, and it also contains one of the most abundant 
freshwater mussel communities in Texas (Burlakova and Karatayev 2010a, 
p. 14).
    In 2009, a large population of golden orb was discovered farther 
downstream in the mainstem Guadalupe River in Victoria County, when 
over 100 individuals were found (Johnson 2009, p. 1). Multiple size 
classes were observed, including juveniles, indicating this population 
is reproducing and recruiting new individuals into the population. A 
large number of shells was collected upstream of this site in 1994 
(Burlakova and Karatayev 2010c, p.1), but no golden orb were seen alive 
until 2009.
    The San Marcos River, a tributary to the Guadalupe River, also 
supports a large golden orb population near its confluence with the 
tailwaters (outflow) of Lake Wood Dam. Although much of the San Marcos 
River has been extensively surveyed, with very few freshwater mussels 
present of any species (Howells 1995, pp. 33-34; 1997a, p. 40; 2004, 
pp. 15-16, 18; 2005, p. 10), one old golden orb shell was found near 
the town of Staples (Howells 1998, p. 19), and a single live individual 
was found near the town of Luling (Howells 1999, p. 28). Downstream 
from these locations, a large population persists in the vicinity of 
Palmetto State Park in Gonzales County. In 1995, a recently dead 
individual was discovered downstream of the park, indicating the recent 
presence of the species (Howells 1996, p. 28), and, based on surveys 
from 2000-2006, a relatively large population was confirmed to be in 
the area (Howells 2001, pp. 32-33; 2006, pp. 72-73; 2006, p. 91; 
Burlakova and Karatayev 2010a, pp. 14-15).
    Historically, golden orb were numerous in the San Antonio River in 
Karnes County (OSUM 2011b, p. 1), but only a single subfossil shell was 
found at each of two sites in Karnes County in 1996 (Howells 1997a, pp. 
41-42). No live animals have been found there since, although abundant 
shell material remains present (Karatayev and Burlakova 2008, p. 40).
    The lower portion of the San Antonio River supports the largest 
known golden orb population. In 2007, 37 live golden orb were recorded 
near Goliad in Goliad County, both within and downstream of Goliad 
State Park (Howells 2009, p. 11). The following year, 285 live golden 
orb were found within the park and downstream surrounded by private 
lands (Burlakova and Karatayev 2010a, p. 15). This site represents the 
largest known population of golden orb.
    In 2009, a single live golden orb was discovered in the lower San 
Antonio River south-southwest of Victoria in Victoria County (Johnson 
2009, p. 1); this site has not been surveyed since. We presume golden 
orb may persist in this stretch of river.
    The golden orb appears to have been extirpated from the Medina 
River. The species historically occurred in Medina and Bexar Counties 
(Randklev et al. 2010b, p. 4; OSUM 2011b, p. 1), but no live or dead 
mussels of any species have been found in this river in recent years 
(May 2011, pers. comm.).
    Cibolo Creek, a tributary to the San Antonio River, was extensively 
surveyed in the 1990s, with only old golden orb shells collected in 
Wilson County (Howells 1995, pp. 35-37; 1997a, pp. 40-41). In 2006 and 
2007, Burlakova and Karatayev (2010b, p. 1) surveyed this same general 
area and found only shell material. It is unlikely golden orb remain in 
Cibolo Creek.
Nueces-Frio River System
    Information is limited on the occurrence of golden orb in the 
Nueces River. Other than a population that occurs in a reservoir on the 
lower Nueces River (Lake Corpus Christi), the species appears to be 
extirpated from the remainder of the basin.
    Historically, the golden orb occurred in the Nueces River in Live 
Oak County (OSUM 2011b, p. 1). It was last seen alive in the Nueces 
River in 1993, when unreported numbers were found in the same area 
(Burlakova and Karatayev 2010c, p. 1). A shell was collected in the 
same general area in 1995 (Burlakova and Karatayev 2010c, p. 1), but 
additional surveys in 1996 and 1997 found no evidence of the species 
(Howells 1997a, pp. 43-44; 1998, p. 20). We presume the species no 
longer occurs in the upper portions of the Nueces River.
    An anomalous (odd) population of golden orb has persisted in Lake 
Corpus Christi Reservoir in the lower Nueces River. While the species 
does not typically inhabit lentic (ponded) water, wave action is 
presumed to simulate flowing water conditions and has supported a 
golden orb population since at least the 1970s (OSUM 2011b, p. 1). A 
few live individuals of golden orb have been found within the reservoir 
consistently since 1994 (Howells 1995, p. 39; 1996, pp. 30-31; 
Burlakova and Karatayev 2010c, p. 1). Numbers of golden orb collected 
increased in 1996, when 86 live golden orb were found at three 
different locations within the reservoir (Howells 1996, pp. 30-31). 
However, a drawdown of the lake in 1996 resulted in large numbers of 
golden orb stranded and killed (Howells 2010a, p. 9), and in 1998 no 
live individuals were found (Howells 1999, p. 19). Again in 2005, no 
live individuals were found during surveys, but in 2006, a total of 
nine were collected at three different sites within the reservoir 
(Howells 2006, pp. 73-76, 91-93). A small golden orb population likely 
persists in the reservoir.
    Very little information is available on the distribution of golden 
orb in the Frio River. Shells were last seen in McMullen County in 1994 
(Burlakova and Karatayev 2010c, p. 1), but no evidence of the species 
has been found in this river since (Howells 1995, pp. 37-38; 1996, p. 
29; 2002a, pp. 9-10; 2004, pp. 19-20).
Summary
    Based on historical and current data, the golden orb has declined 
rangewide and is now known from only nine populations in four rivers 
and has been eliminated from nearly the entire Nueces-Frio River 
system. Four of these populations appear to be stable and reproducing; 
the remaining five populations are small and isolated and show no 
evidence of recruitment. Only the populations in the middle Guadalupe 
River and lower San Marcos River are likely connected; the remaining 
extant populations are highly fragmented and restricted to short 
reaches.

Species Information for Smooth Pimpleback

Species Description

    The smooth pimpleback is a nearly round, thick-shelled freshwater 
mussel that generally reaches at least 60 mm (2.6 in) in length 
(Howells 2010b, p. 4). It is moderately thick, solid, and inflated. 
Externally, the smooth pimpleback, like its name suggests, is 
relatively smooth with minute sculpturing; it may or may not have a few 
small pustules (raised bumps) (Howells 2010b, p. 2). The external 
coloration of the shell ranges from tan

[[Page 62172]]

to light brown, dark brown, and black with no rays (Howells 2010b, p. 
4).

Taxonomy

    The smooth pimpleback was originally described by Lea in 1859 as 
Unio houstonensis. It was later placed in the genus Margaron and 
ultimately moved to Quadrula by Simpson (1900, p. 782). Graf and 
Cummings (2007, p. 18) have proposed moving it to the genus Amphinaias, 
but other freshwater mussel taxonomists recommend waiting for 
additional work to be completed on members of Quadrula before splitting 
the genus (Bogan 2011, pers. comm.). The smooth pimpleback is 
recognized by the Committee on Scientific and Vernacular Names of 
Mollusks of the Council of Systematic Malacologists, American 
Malacological Union (Turgeon et al. 1998, p 37), and we recognize it as 
a valid species.

Biology and Life History

    There is no specific information on age, size of maturity, or host 
fish use for smooth pimpleback. Numerous individuals were examined for 
gravidity between June and November, with no evidence of eggs or 
glochidia (Howells 2000b, p. 38). Other species in the genus Quadrula 
successfully parasitize catfish, and it is likely smooth pimpleback 
does as well (Howells 2010b, p. 2); additionally, mussels in the genus 
Quadrula are typically short-term brooders (Gorden and Layzer 1989, p. 
6; Garner et al. 1999, p. 277), and we expect the same of the smooth 
pimpleback.

Habitat

    The smooth pimpleback has been found in mud, sand, and fine gravel 
in medium-to-large rivers and some reservoirs (Howells 2010b, p. 3). 
Unlike most other Quadrula species in central Texas, smooth pimpleback 
do occur in some reservoirs (Howells 2002b, p. 8; 2010b, p. 3).

Distribution and Abundance

Historical Distribution
    The smooth pimpleback is native to the central and lower Brazos and 
Colorado Rivers and their tributaries in central Texas (Howells 2010b, 
p. 4). The smooth pimpleback has also been reported from the Trinity 
River and other drainages in Texas, as well as from areas outside of 
Texas, including southern Arkansas and the Verdigris River in Kansas. 
These reports are likely misidentifications of other pimpleback species 
that can sometimes closely resemble smooth pimpleback (Howells 2010b, 
pp. 4-5). The smooth pimpleback was historically uncommon where it 
occurred; from the 1960s through the 1990s, experts failed to find 
large populations persisting throughout its range (Howells 2009, p. 
12).
    In the Colorado River, historical reports indicate that the smooth 
pimpleback occurred from San Saba County downstream to Wharton County, 
as well as in the Llano River and Onion and Skull Creeks. Within the 
Brazos River basin, the species historically occurred throughout the 
length of the mainstem of the Brazos River (Howells 2009, p. 12), as 
well as in the Clear Fork Brazos, Leon, Navasota, Little Brazos, San 
Gabriel, Lampasas, and Little Rivers and Yegua Creek (Howells 2010b, 
pp. 4-6; Randklev et al. 2010b, p. 20).
Current Distribution
    The smooth pimpleback has been nearly extirpated from the Colorado 
River basin, and a few small populations persist in the Brazos River 
basin. Recent surveys suggest a greater abundance and distribution of 
the smooth pimpleback in the central Brazos River drainage than was 
indicated by collections from the past 40 years, with five populations 
represented by more than a few individuals.
Colorado River System
    The smooth pimpleback historically occurred throughout the mainstem 
Colorado River as well as several tributaries, but it is currently 
restricted to one mainstem reservoir, two sites on the mainstem 
Colorado River, and the San Saba River. Populations in all of the other 
historically occupied tributaries and two reservoirs appear to have 
been extirpated.
    In the mainstem Colorado River, smooth pimpleback were historically 
known from much of the length of the river (Howells 1996, p. 21; 1997a, 
pp. 34-35; Randklev et al. 2010c, p. 4; OSUM 2011c, p. 1). Numerous 
surveys in many locations on the Colorado River occurred between 1993 
and 2009, and no evidence of smooth pimpleback was found (Howells 1995, 
p. 29; 1996, p. 23; 1997a, pp. 27, 31; 2002a, p. 6; 2004, p. 7, 11; 
2005, p. 6; Burlakova and Karatayev 2010a, pp. 15-16), except for in 
Colorado County in 1999, when three live smooth pimpleback were found 
(Howells 2000a, p. 27). During two surveys in 2009, live smooth 
pimpleback were found in the same general area as in 1999 (Burlakova 
and Karatayev 2010a, p. 16; Johnson 2009, p. 1). Farther downstream, in 
Wharton County, live smooth pimpleback were found at two sites in 2009 
(Burlakova and Karatayev 2010a, p. 16), despite having been surveyed in 
1995 and none found (Howells 1996, p. 23).
    Inks Lake is a small mainstem reservoir on the Colorado River in 
Burnet County. Several live smooth pimpleback were found in 1992 
(Howells 1994, p. 4); however, since that time only shell material has 
been found during four separate surveys between 1996 and 2005 (Howells 
1997a, pp. 32-33; 1999, p. 16; 2005, p. 8; 2006, p. 67). Frequent 
drawdowns in this lake appear to have affected all species of 
freshwater mussels, as there has been a sharp decline in the overall 
mussel community (Howells 1999, p. 16).
    One live smooth pimpleback was found in Lake Lyndon B. Johnson, a 
large mainstem reservoir on the Colorado River, in 2001, but no live 
individuals have been found since (Howells 2002a, pp. 6-7; 2006, pp. 
68-69). Farther downstream, in Lake Marble Falls, 13 live smooth 
pimpleback were found in 1995 during a drawdown of lake levels (Howells 
1996, p. 22), but subsequent surveys in 1996 failed to find any 
additional living animals (Howells 1997a, p. 33). The small recent 
survey effort is not sufficient to conclude that the smooth pimpleback 
no longer occur in these lakes, and small populations may still persist 
there.
    Smooth pimpleback were recently found in the San Saba River in San 
Saba County, when 29 individuals were found at two locations (Burlakova 
and Karatayev 2011, p. 5). Various size and age classes were 
represented, indicating a reproducing, recruiting population (Burlakova 
and Karatayev 2011, p. 5). Even more recently, 206 smooth pimpleback, 
including adults and juveniles, were recorded in this same area in 
riffle and pool habitat (Randklev 2011b, p. 1).
    No smooth pimpleback populations remain in any of the Colorado 
River tributaries in which the species was historically known to occur, 
including the full length of the Llano River (Howells 1996, pp. 21-22; 
1998, p. 17; 2000a, p. 25; 2005, p. 8; Randklev et al. 2010c, p. 4; 
OSUM 2011c, p. 1). A single subfossil shell, likely a smooth 
pimpleback, was found in the Llano River in Kimble County in 1995 
(Howells 1996, pp. 21-22), but no other evidence of the species has 
been found in the Llano River in recent years. Additionally, although 
Onion and Skull Creeks were historically occupied by smooth pimpleback 
(Randklev et al. 2010c, p. 4), the species has not been found recently 
in either stream (Howells 1995, pp. 28-29).

[[Page 62173]]

Brazos River System
    The smooth pimpleback historically occurred in the Brazos River 
system from Palo Pinto County downstream to Austin and Waller Counties, 
as well as in numerous tributaries. The species has been extirpated 
from the upstream half of the mainstem Brazos River and from at least 
three tributaries. Substantial populations persist in the Leon River, 
Navasota River, and Yegua Creek, and small populations remain in the 
lower Brazos and Little Brazos Rivers.
    In the mainstem Brazos River, surveys in Palo Pinto, Somervell, and 
Bosque Counties between 1996 and 2000 indicate that the smooth 
pimpleback has been extirpated from the upstream portion of the river 
(Howells 1997a, pp. 16, 18-19; 1999, pp. 11-12; 2001, p. 19). Despite 
surveys in 1996 and 1998 in which no individuals were found (Howells 
1997a, p. 21; 1999, p. 12), a single live smooth pimpleback was found 
in McLennan County in the middle Brazos River in 2005 (Howells 2010b, 
p. 5), and two live individuals were recorded in Falls County in 2006 
(Karatayev and Burlakova 2008, pp. 6-10).
    Although not extirpated from the middle Brazos River, the smooth 
pimpleback occurs only in low numbers. In Milam and Robertson Counties, 
no smooth pimpleback were found in 1998 (Howells 1999, p. 13), but 
eight live individuals were found in 2006 (Burlakova and Karatayev 
2010b, p. 1). More recently, in 2008, 13 live smooth pimpleback were 
found at the same site (Randklev et al. 2009, p. 18). Additionally, 
downstream in Burleson and Brazos Counties, which were historically 
occupied by the smooth pimpleback (OSUM 2011c, p. 1), a small 
population persists. In 1995, one live and one recently dead individual 
were collected within Brazos County (Howells 1996, pp. 17-18). Although 
none were found here in 1999 (Howells 2000a, pp. 21-22), in 2006 a 
single live smooth pimpleback was collected at this site (Karatayev and 
Burlakova 2008, pp. 6-10). Additionally, further downstream in Grimes 
and Waller Counties, a single live individual was found in 2006 
(Burlakova and Karatayev 2010b, p. 1) and again in 2008 (Randklev et 
al. 2009, p. 18). Smooth pimpleback are more numerous in the lower 
mainstem Brazos River, in Austin and Waller Counties, where 38 live 
individuals were found in 2006 (Karatayev and Burlakova 2008, pp. 6-
10).
    Tributaries to the Brazos River also contain smooth pimpleback 
populations. The Leon River, in the Little River drainage of the 
Brazos, historically contained smooth pimpleback throughout its length 
in Hamilton, Coryell, and Bell Counties (Howells 1994, p. 19, 1997a, p. 
20; Randklev et al. 2010c, p. 4; OSUM 2011c, p. 1). Currently, a smooth 
pimpleback population persists in Hamilton County, where numerous live 
individuals were found in 2006 and 2011 (Howells 2006, pp. 82-83; 
Randklev 2011a, p. 1), as well as several locations in Coryell County, 
where numerous individuals were also recently found (Randklev 2011a, p. 
1).
    Only subfossil smooth pimpleback shells have been found in the 
Lampasas River in Bell County in 1996 (Howells 1997a, pp. 20, 23). 
Subsequent surveys of the river in both Bell and Lampasas Counties 
yielded no evidence of smooth pimpleback (Howells 1999, p.14; 2001, p. 
20), and the species has likely been extirpated from the Lampasas 
River.
    The Little River in Milam County is also a historical location for 
the smooth pimpleback (Randklev et al. 2010c, p. 4). Old shells were 
found at this site in 1996 (Howells 1997a, p. 22), and a single live 
individual was found here in 2006 (Karatayev and Burlakova 2008, p. 6). 
Farther downstream, at the confluence with the Brazos River, none have 
been found (Howells 1996, p. 17).
    A single old smooth pimpleback shell has been found in the San 
Gabriel River in Milam County (Howells 1997a, p. 23), and it is likely 
the species has been extirpated from this Brazos River tributary as 
well.
    In the Little Brazos River, the smooth pimpleback appears to 
persist in low numbers. Although none were found in Robertson County in 
1993 and there had appeared to be a die off of numerous freshwater 
mussel species (Howells 1995, p. 18), one live smooth pimpleback was 
found during a 2006 survey (Karatayev and Burlakova 2008, p. 6). 
Farther downstream in Brazos County, recently dead individuals were 
discovered in 2001 (Howells 2002a, pp. 4-5). The species occurred in 
this area historically (Randklev et al. 2010c, p. 4), and reports of 
mussels in the Little Brazos River from the 1950s described the 
freshwater mussel community as numerous, including smooth pimpleback 
(Gentner and Hopkins 1966, pp. 458-459), but no live individuals have 
been collected in this area in recent years (Howells 1996, p. 18; 1999, 
p. 14).
    The smooth pimpleback has been extirpated from the Clear Fork 
Brazos River. Although this species was originally documented from this 
river in Shackelford County in 1893 (Randklev et al. 2010c, p. 4), none 
have been found in this stream since (Howells 1999, p. 19).
    In the Navasota River, smooth pimpleback historically occurred in 
Leon, Brazos, Grimes, and Washington Counties (Randklev et al. 2010c, 
p. 4; OSUM 2011c, p. 1). Currently, the species persists in each of 
those counties, with a large population occurring in the lower river. 
In Leon County three recently dead smooth pimpleback shells were found 
in 2000 (Howells 2001, p. 23), indicating that a few individuals may 
persist in the area. However, one of the largest known populations 
occurs farther downstream near the confluence of the Navasota and 
Brazos Rivers. Nine live individuals were found in this area in 2006 
(Karatayev and Burlakova 2008, pp. 6-10), and in 2008 a total of 117 
live smooth pimpleback were recorded at 3 different locations within 
Washington and Grimes Counties (Randklev et al. 2009, pp. 6, 18). A 
large population continues to persist in the Navasota River, with a 
total of 314 smooth pimpleback recorded at two sites in 2011 (Randklev 
2011a, p. 1).
    In Yegua Creek, no smooth pimpleback were found during several 
surveys between 1996 and 2003 (Howells 1997a, pp. 24-26; 2001, p. 22; 
2004, p. 6), although subfossil shells were found in Washington County 
in 1996. However, in 2006, a live individual was discovered (Karatayev 
and Burlakova 2008, pp. 6-10), which prompted further surveys in 2008. 
Numerous smooth pimpleback were found during subsequent surveys at four 
different locations within Washington and Burleson Counties (Randklev 
et al. 2009, pp. 16-18; Randklev 2011a, p. 1), indicating the presence 
of a potentially large population in this stream.
Summary
    Based on historical and current data, the smooth pimpleback has 
declined rangewide and is now known from only nine locations. The 
species has been eliminated from nearly the entire Colorado River and 
all but one of its tributaries, as well as from the upper Brazos River 
and several tributaries. The San Saba River, lower Brazos River, 
Navasota River, Leon River, and Yegua Creek populations appear to be 
stable and reproducing, but the remaining populations are small, 
isolated, and represented by only a few individuals.

Species Information for Texas Pimpleback

Species Description

    The Texas pimpleback is a large pimpleback species with a 
moderately

[[Page 62174]]

inflated shell that generally reaches 60-90 mm (2.4-3.5 in) (Howells 
2002b, pp. 3-4). With the exception of growth lines, the shell of the 
Texas pimpleback is generally smooth and moderately thick (Howells 
2002b, p. 4). Externally, coloration ranges from yellowish-tan to dark 
brown with some individuals mottled or with dark green rays. 
Internally, the nacre is white and iridescent posteriorly (Howells 
2002b, p. 4).

Taxonomy

    The Texas pimpleback was originally described as Unio petrinus by 
Gould in 1855. It was placed in the genus Margaron by Lea in 1870 and 
ultimately moved to Quadrula by Simpson in 1900 (Simpson 1900, p. 783). 
Graf and Cummings (2007, p. 18) have proposed moving it to the genus 
Amphinaias, but other freshwater mussel taxonomists recommend waiting 
for additional work to be completed on members of Quadrula before 
splitting the genus (Bogan 2011, pers. comm.). The Texas pimpleback is 
recognized by the Committee on Scientific and Vernacular Names of 
Mollusks of the Council of Systematic Malacologists, American 
Malacological Union (Turgeon et al. 1998, p. 37), and we recognize it 
as a valid species.

Biology and Life History

    There is very little specific information on age, size of maturity, 
or host fish use for Texas pimpleback. Gravid females have been found 
from June through August, and the smallest documented gravid female was 
45 mm (1.8 in) long (Howells 2000b, p. 38). Glochidia are hookless and 
elliptical in shape (Howells et al. 1996, p. 120). To date, no host 
fish have been confirmed for the Texas pimpleback; however, glochidia 
have been reported attached to and encysted on flathead catfish 
(Pylodictis olivaris), yellow bullhead (Ameiurus natalis), and bluegill 
in laboratory settings, although none transformed to the juvenile stage 
(Howells 2010e, p. 3). This is consistent with other species in the 
genus Quadrula, which also parasitize catfish species.

Habitat

    The Texas pimpleback typically occurs in moderately sized rivers, 
usually in mud, sand, gravel, and cobble, and occasionally in gravel-
filled cracks in bedrock slab bottoms (Horne and McIntosh 1979, p. 122; 
Howells 2002b, p. 4). The species has not been found in water depths 
over 2 m (6.6 ft). Texas pimpleback have not been found in reservoirs, 
which indicates that this species is intolerant of deep, low-velocity 
waters created by artificial impoundments (Howells 2002b, p. 4). In 
fact, Texas pimpleback appear to tolerate faster water more than many 
other mussel species (Horne and McIntosh 1979, p. 123).

Distribution and Abundance

Historical Distribution
    The Texas pimpleback is endemic to the Colorado and Guadalupe-San 
Antonio River basins of central Texas (Howells 2002b, p. 3). In the 
Colorado River basin, Texas pimpleback occurred throughout nearly the 
entire mainstem, as well as numerous tributaries, including the Concho, 
North Concho, San Saba, Llano, and Pedernales Rivers, and Elm and Onion 
Creeks (Howells 2010e, p. 5; Randklev et al. 2010c, p. 4; OSUM 2011d, 
p. 1). Within the Guadalupe-San Antonio River basin, it occurred 
throughout most of the length of the Guadalupe River, as well as in the 
San Antonio, San Marcos, Blanco, and Medina Rivers (Horne and McIntosh 
1979, p. 122; Howells 2010e, p. 5; OSUM 2011d, p. 1).
Current Distribution
    The Texas pimpleback has declined significantly rangewide, and only 
four streams--the San Saba River, Concho River, Guadalupe River, and 
San Marcos River--are known to harbor persisting Texas pimpleback 
populations. These populations are disjunct, small, and isolated. The 
species has been extirpated from the remainder of its historical range.
Colorado River System
    In the Colorado River system, Texas pimpleback once occurred 
throughout the mainstem and in many major tributaries. Currently, the 
species has been extirpated from the Pedernales, North Concho, and 
Llano Rivers, as well as Onion Creek. It has also likely been 
extirpated from the mainstem Colorado River and Elm Creek. The Concho 
River contains the most abundant population of Texas pimpleback and one 
of only two populations of the species likely to be remaining in the 
Colorado River system, but most individuals are old and there has been 
very little evidence of recruitment.
    In the mainstem Colorado River, Texas pimpleback historically 
occurred from Runnels County downstream to Colorado County (Howells 
2010e, p. 5; Randklev et al. 2010c, pp. 3-4; OSUM 2011d, p. 1). 
However, surveys in numerous locations along the river yielded no 
evidence of the species anywhere except in Runnels and San Saba 
Counties (Howells 1995, pp. 20, 29; 1997a, pp. 27, 31, 35; 2000a, p. 
27; 2002a, p. 7). In Runnels County, Texas pimpleback shells were found 
in 1993 (Howells 1995, p. 20), but several subsequent surveys between 
1996 and 2008 detected no further evidence of the species (Howells 
1997a, p. 27; 1998, p. 10; 2002a, p. 7; 2004, p. 7; Burlakova and 
Karatayev 2010a, p. 10). In San Saba County, a single shell was 
collected in 1989 (Howells 2002b, p. 6), and three recently dead 
individuals were found in 1999 (Howells 2000a, pp. 25-26). An 
additional shell was collected in 2001 (Howells 2002a, p. 6). No live 
individuals have been collected from this reach of the Colorado River.
    In Runnels County, Elm Creek once supported a Texas pimpleback 
population. Small numbers of Texas pimpleback were found in 1993 and 
1995 (Howells 1995, p. 21; 1996, p. 20), but none were found in 1997, 
2001, or 2003 (Howells 1998, p. 11; 2002a, p. 5; 2004, p. 7). In 2005 
and 2008, only dead individuals were collected (Howells 2006, pp. 63-
64; Burlakova and Karatayev 2010a, p. 10). No live individuals have 
been found in over a decade despite repeated sampling efforts, and it 
is likely the Texas pimpleback has been extirpated from this stream.
    The Concho River in Concho County supports the largest Texas 
pimpleback population. Thirteen and 28 individuals were collected in 
1993 and 1994, respectively (Howells 1995, pp. 24-25; 2006, p. 61). 
However, low water and high temperatures in 1997 killed large numbers 
of many freshwater mussel species in the area up and downstream of 
Paint Rock, and 63 recently dead Texas pimpleback were found (Howells 
1998, pp. 14-15). A severe drought in 1999 resulted in this area of the 
Concho River being reduced to a series of small pools. Few live Texas 
pimpleback were collected during this drought, in addition to many 
recently dead individuals (Howells 2000a, p. 23). No evidence of the 
species was found in 2004 (Howells 2005, p. 9), but eight live 
individuals were found in 2005 (Howells 2006, p. 60), evidence that the 
species had survived the extreme dewatering of the river. In 2008, 61 
live Texas pimpleback were collected in this same area, and the 
population was estimated to contain approximately 4,000 individuals 
(Burlakova and Karatayev 2010a, p. 10; 2010b, p. 1). However, the 
average length of individuals collected at this site was over 90 mm 
(3.5 in), indicating that reproduction is limited in this population. 
Further, although no mussel surveys occurred in 2009 and 2010, the

[[Page 62175]]

river was reported to be extremely low during this time (Howells 2010e, 
p. 6); the result of this additional dewatering on the population is 
unknown.
    The San Saba River historically contained Texas pimpleback 
(Randklev et al. 2010c, p. 2), but no live individuals had been 
collected in over a decade until recently when shells were collected in 
1992 and 1995 (Howells 1994, p. 7; 1996, p. 21), and five live 
individuals were collected in 1997 (Howells 1998, p. 16). However, 
subsequent surveys were conducted in 2000, 2004, and 2005, with only 
shell material being found in 2000 (Howells 2001, pp. 28-29), and no 
evidence of Texas pimpleback was found in 2004 and 2005 (Howells 2005, 
pp. 8-9; 2006, pp. 64-65). A single shell was collected in 2008 
(Burlakova and Karatayev 2010b, p. 1). However, in 2011, 39 live 
individuals were found at two sites in San Saba County (Burlakova and 
Karatayev 2011, p. 3). The individuals found were of various sizes and 
ages, indicating a reproducing population (Burlakova and Karatayev 
2011, p. 4). Further surveys at this site confirm a large population in 
the area, with 140 individuals, including many juveniles, found here 
(Randklev 2011b, p. 1).
    The Texas pimpleback also historically occurred in the North 
Concho, Pedernales, and Llano Rivers, as well as Onion Creek (Howells 
2010e, p.5; Randklev et al. 2010c, p. 4; OSUM 2011d, p. 1); all are 
tributaries within the Colorado River system. In the North Concho 
River, all freshwater mussels are presumed extirpated from historically 
occupied areas (Howells 1995, pp. 22-23). The Pedernales River 
historically harbored a Texas pimpleback population (OSUM 2011d, p. 1), 
but only old shells have been collected in this river in recent years 
(Howells 1994, p. 5). Since 1993, no evidence of Texas pimpleback has 
been found (Howells 1995, pp. 27-28; 1999, p. 16), and the species is 
presumed to be extirpated. Additionally, repeated surveys in the Llano 
River in Kimble and Mason Counties consistently failed to collect live 
Texas pimpleback, with shells found only in Llano County in 1997 
(Howells 1996, pp. 21-22; 1998, p. 17; 2005, p. 8). The Texas 
pimpleback is likely extirpated from all of these streams.
Guadalupe River System
    In the Guadalupe River system, the Texas pimpleback has been 
extirpated from nearly the entire reach of the mainstem Guadalupe, San 
Antonio, and Blanco Rivers. Very small populations remain only in the 
lower Guadalupe and San Marcos Rivers, represented by one or two 
individuals in each.
    In the mainstem Guadalupe River, the Texas pimpleback was 
historically known throughout the length of the river, from as long ago 
as 1905 (Randklev et al. 2010c, p. 1; OSUM 2011d, p. 1). Numerous 
surveys between 1992 and 2005 have not yielded any evidence of the 
species anywhere but in Victoria County (Howells 1994, pp. 7-9; 1995, 
pp. 30-32; 1996, pp. 25-27; 1997a, pp. 37-40; 1999, pp. 18-19; 2002a, 
p. 8; 2003, pp. 15, 17; 2006, pp. 71-72; Johnson 2009, p. 1), where two 
live individuals were collected in 2009. A small population may remain 
in the lower Guadalupe River.
    In the San Marcos River near the confluence with the Blanco River 
in Hays County, repeated surveys between 1992 and 2000 yielded no 
evidence of Texas pimpleback (Howells 1994, pp. 9-10; 1995, pp. 33-34; 
1996, p. 27; 1997a, p. 40; 2000a, p. 28; 2001, pp. 32-33). However, in 
2003 two shells were collected (Howells 2004, p. 16), and in 2004, a 
single live individual was found (Howells 2005, p. 10). The Texas 
pimpleback likely persists in this river in very low numbers.
    The Texas pimpleback appears to be extirpated from the San Antonio 
River, with only shell fragments found near the City of San Antonio in 
Bexar County in 1993 (Howells 1995, p. 35). No evidence of the species 
was found downstream in Karnes County in 1996 (Howells 1997a, pp. 41-
42).
    The Texas pimpleback was once described as abundant in the Blanco 
River just upstream of its confluence with the San Marcos River in Hays 
County (Horne and Mcintosh 1979, p. 126), but repeated surveys of this 
area between 1992 and 1995 yielded no recent evidence of the species 
(Howells 1994, p. 9; 1995, pp. 32-33; 1996, p. 27), with only a 
subfossil shell collected in 1993 (Howells 1995, p. 33). No shell 
material or live individuals were found in additional surveys in 2011 
(Johnson 2011, p. 1).
Summary
    The Texas pimpleback has been eliminated from long reaches of 
former habitat in hundreds of miles of the Colorado and Guadalupe River 
systems. Only two populations appear large enough to be stable, but 
evidence of recruitment in the Concho River population is limited. The 
San Saba River population may be the only remaining recruiting 
population of Texas pimpleback. Two additional populations are 
represented by one or two individuals; all populations are highly 
disjunct.

Species Information for Texas Fawnsfoot

Species Description

    The Texas fawnsfoot is a small, relatively thin-shelled freshwater 
mussel that can reach 60 mm (2.4 in) in length but is usually much 
smaller (Howells 2010d, p. 2). The shell is long and oval, generally 
free of external sculpturing, with external coloration that varies from 
yellowish- or orangish-tan, brown, reddish-brown, to smoky-green with a 
pattern of broken rays or irregular blotches (Howells 2010d, p. 2). The 
nacre is bluish-white or white and iridescent posteriorly (Howells 
2010d, p. 2).

Taxonomy

    The Texas fawnsfoot was first described as Unio macrodon by Lea in 
1859 and was subsequently placed in the genus Margaron by Lea in 1870 
and then moved to Plagiola by Simpson (1900, p. 605). Ultimately the 
species was placed in the genus Truncilla by Strecker (1931, pp. 63, 
65). The Texas fawnsfoot is recognized by the Committee on Scientific 
and Vernacular Names of Mollusks of the Council of Systematic 
Malacologists, American Malacological Union (Turgeon et al. 1998, p. 
37), and we recognize it as a valid species.

Biology and Life History

    There is no specific information on age, size of maturity, or host 
fish use for Texas fawnsfoot. However, other species in the genus 
Truncilla parasitize freshwater drum (Aplodinotus grunniens) (OSUM 
2011f, p. 1), and it is likely the Texas fawnsfoot does as well. 
Freshwater drum are ubiquitous throughout the range of Texas fawnsfoot 
(Hubbs et al. 2008, p. 53).

Habitat

    Since Texas fawnsfoot were not found alive for many years, very 
little information is available about its habitat preferences. In the 
past only Texas fawnsfoot shells and recently dead individuals were 
occasionally found along rivers following drought-related dewatering or 
bank deposition after high floods. These shells and recently dead 
individuals indicated that the Texas fawnsfoot occurs in flowing water, 
as it was never found in ponds, lakes, or reservoirs, suggesting that 
it is intolerant of deep, low-velocity waters created by artificial 
impoundments (Howells 2010d, p. 3). The recently discovered live 
population in the Brazos River indicates that the species occurs in 
rivers with soft, sandy sediment with moderate water flow (Randklev and

[[Page 62176]]

Lundeen 2010, p. 1; Randklev et al. 2010a, p. 298; Johnson 2011, p. 1).

Distribution and Abundance

Historical Distribution
    The Texas fawnsfoot is endemic to the Brazos and Colorado Rivers of 
central Texas (Howells et al. 1996, p. 143; Randklev et al. 2010a, p. 
297). From the 1960s to the 1990s, malacologists working in central 
Texas found few individuals and few new population locations (Howells 
2010d, p. 6). Historical records suggest the Texas fawnsfoot inhabited 
much of the Colorado River, from Wharton County upstream as far as the 
North Fork Concho River in Sterling County, as well as throughout the 
Concho, San Saba, and Llano Rivers and Onion Creek within the Colorado 
River basin (Howells 2010d, p. 4; Randklev et al. 2010b, p. 24). In the 
Brazos River, the species occurred from Fort Bend County upstream to 
the lower reaches of the Clear Fork Brazos River in Shackelford County, 
as well as in the Leon River, Little River, San Gabriel River, Deer 
Creek, and Yegua Creek (Howells 2010d, pp. 4-5; Randklev et al. 2010b, 
p. 24). Species reports from the Trinity River and other east Texas 
locations are of misidentified fawnsfoot (Truncilla donaciformis) 
(Howells 2010d, p. 4).
Current Distribution
    Relatively few Texas fawnsfoot have been documented since this 
species was first described in 1859, and very few live individuals have 
been found in recent decades (Randklev et al. 2010a, p. 297). All of 
these animals were flood deposited on gravel bars and near death just 
prior to collection (Randklev et al. 2010a, p. 297), preventing 
information from being gathered about population size, preferred 
habitat, and other parameters. A live population of Texas fawnsfoot was 
not discovered until 2008 in the Brazos River near its confluence with 
the Navasota River (Randklev et al. 2010a, p. 297). A second live 
population was found in 2009 in the Colorado River (Johnson 2009, p. 
1). These two locations contain the only confirmed populations of the 
species to date. Evidence of other remnant populations has also been 
found in the Clear Fork Brazos River, San Saba River, and Deer Creek.
Colorado River System
    The Texas fawnsfoot has been eliminated from almost all of the 
Colorado River system. Live individuals were found in the lower 
mainstem Colorado River in 2009, and the only other evidence of current 
occurrence of Texas fawnsfoot in the Colorado River basin is in the San 
Saba River, where a population persists.
    In the mainstem Colorado River, the Texas fawnsfoot historically 
occurred from Wharton County upstream into the headwaters (Randklev et 
al. 2010c, p. 4; OSUM 2011e, p. 1). Surveys throughout the upper 
Colorado River between 1993 and 2009 yielded no evidence of Texas 
fawnsfoot (Howells 1994, pp. 20-21, 29; 1996, pp. 20-21, 23; 1997a, pp. 
27, 31, 34-35; 1998, p. 10; 2000a, p. 27; 2002a, p. 6; 2004, p. 7; 
Burlakova and Karatayev 2010a, p. 16), except for one recently dead 
individual found in 1999 in San Saba County when the entire river was 
dewatered and all mussels were eliminated from the area (Howells 2000a, 
pp. 25-26; 2009, p. 17). The lack of evidence of the species since that 
time indicates that the population may have been lost. In the lower 
Colorado River in Colorado County, several old shells of Texas 
fawnsfoot were found at several sites in 1996 (Howells 1997a, p. 35), 
and, subsequently in 2009, two live individuals were discovered 
(Johnson 2011, p. 1). The population was later estimated to be 
approximately 2,800 individuals, with individuals ranging in size from 
21 to 38 mm (0.8-1.5 in) (Burlakova and Karatayev 2010a, p. 17), 
indicating that reproduction and recruitment is occurring.
    Texas fawnsfoot were not known to occur in the San Saba River until 
a single live individual was collected in 2011 (Burlakova and Karatayev 
2011, p. 6). Additional surveys yielded 16 Texas fawnsfoot of various 
ages collected at the site (Randklev 2011b, p. 1), indicating a 
persistent, recruiting population.
    Texas fawnsfoot is presumed extirpated from the remainder of the 
Colorado River basin. Although historical records exist in the North 
Concho, Concho, and Llano Rivers and in Onion Creek (Randklev et al. 
2010c, p. 4), numerous surveys of these streams indicate the 
extirpation of the species (Howells 1994, pp. 5-6; 1995, pp. 22-25, 28-
29; 1996, pp. 21-22; 1998, pp. 14-17; 1999, pp. 15-16; 2000a, pp. 23, 
25; 2001, p. 27; 2005, p. 9; Burlakova and Karatayev 2011, p. 6).
Brazos River System
    In the Brazos River system, the Texas fawnsfoot persists in the 
mainstem Brazos River, Clear Fork Brazos River, Navasota River, and 
possibly in Deer Creek. The species has been extirpated from the Leon 
River, Little River, San Gabriel River, and Yegua Creek.
    In the mainstem Brazos River, the Texas fawnsfoot historically 
occurred throughout the length of the river, from Palo Pinto County 
downstream to Fort Bend County (Randklev et al. 2010c, pp. 2-4; 
Burlakova and Karatayev 2010b, p. 1; OSUM 2011e, p. 1). While the 
species appears to have retained its range through the length of the 
Brazos River, occurrences are represented by very few live or recently 
dead individuals. In the upper Brazos River in Palo Pinto and Parker 
Counties, two live individuals were found at each of two sites in 1996, 
as well as numerous shells (Howells 1997a, pp. 16, 17). A survey in 
2000 yielded no evidence of Texas fawnsfoot in this area (Howells 2001, 
p. 19). Nearby, in Somervell County, four recently dead individuals 
were found in the mainstem Brazos River in 1996 (Howells 1997a, pp. 18-
19. In 2007, only one old shell was found in the same area (Burlakova 
and Karatayev 2010b, p. 1).
    Surveys in Milam and Falls Counties have not yielded any evidence 
of Texas fawnsfoot, indicating the species has been extirpated from 
this section of the Brazos River (Howells 1995, p. 17; 1999, pp. 12-
13).
    In the middle Brazos River, Texas fawnsfoot persists in low numbers 
in the vicinity of Brazos County. One live individual was found in 1994 
(Howells 1996, pp. 17-18), representing the first live collection of 
the species anywhere since the 1970s. In 1999, numerous recently dead 
Texas fawnsfoot of mixed sizes and ages were found at several sites in 
Burleson and Brazos Counties (Howells 2000a, pp. 21-22), indicating a 
recruiting population existed in the area. The species has been 
documented here in repeated surveys in 2000, 2003, and 2006 (Howells 
2001, p. 22; Karatayev and Burlakova 2008, p. 7; Howells 2009, p. 17), 
indicating that the species continues to persist in the area.
    The first account of a living population of Texas fawnsfoot 
(animals living in situ rather than deposited on or near the banks by 
floods) occurred in 2008 in the lower Brazos River near its confluence 
with the Navasota River (Randklev et al. 2010a, p. 297). Ten live 
individuals were collected, and all were small, indicating successful 
reproduction and recent recruitment. An additional Texas fawnsfoot was 
found in this area in 2011 (Randklev 2011a, p. 1).
    The farthest downstream collection of Texas fawnsfoot in the Brazos 
River in recent years was in Austin and Waller Counties, when one live 
individual was found in 2006 (Karatayev and Burlakova 2008, p. 39). It 
is likely the species occurs sporadically through the section of the 
Brazos River between Brazos and Austin Counties.

[[Page 62177]]

    Texas fawnsfoot was first discovered in the Navasota River in 2011, 
when three individuals were found in Washington and Grimes Counties 
(Randklev 2011a, p. 1). Previous surveys had not yielded evidence of 
the species in this river (Howells 2001, p. 23).
    In Deer Creek, a tributary to the Brazos River in Falls County, a 
recently dead Texas fawnsfoot was collected in 2006 (Burlakova and 
Karatayev 2010b, p.1), despite previous surveys that yielded no 
evidence of the species (Howells 1999, p. 12).
    Additionally, a Texas fawnsfoot population persists in the Clear 
Fork Brazos River. Recently dead Texas fawnsfoot have been collected in 
several locations along the length of the river, in Shackelford, 
Stephens, and Young Counties (Randklev et al. 2010c, p. 4; Randklev 
2011, pers. comm.). Several other tributaries to the Brazos River that 
historically contained Texas fawnsfoot appear to no longer support the 
species after numerous surveys reveal no living or dead individuals, 
including the Leon River (Howells 1994, pp. 18-20; 1997a, pp. 19-20), 
the Little River (Howells 1997a, pp. 22-23), the San Gabriel River 
(Howells 1997a, p. 23), and Yegua Creek (Howells 1997a, pp. 24, 25-26; 
1999, p. 14; 2001, p. 22; 2004, p. 6).
Summary
    The Texas fawnsfoot has declined rangewide and is now known from 
only five populations. The species has been extirpated from nearly all 
of the Colorado River basin and from much of the Brazos River basin. Of 
the populations that remain, only the Colorado, San Saba, and Brazos 
River populations are likely to be stable and recruiting; the remaining 
populations are disjunct and restricted to short stream reaches.

Five-Factor Evaluation and Findings

    Texas fatmucket, golden orb, smooth pimpleback, Texas pimpleback, 
and Texas fawnsfoot all occur in central Texas across four major river 
basins (Brazos, Colorado, Guadalupe, and Nueces-Frio River basins). 
These species depend on similar physical and biological features and on 
the successful functioning of riverine ecosystems to survive. Many of 
the species face the same or very similar threats. For each species, we 
identified and evaluated all the factors that may be threatening the 
species. However, to avoid redundancy of information when the analysis 
of the threats is the same between species, we referenced the reader to 
the initial description of the common threats. For example, the 
degradation of habitat and habitat loss due to dams and impoundments is 
a common threat to all five species, so a full description of the 
threat was provided for the Texas fatmucket, and for the remaining 
species the initial description was referenced with species-specific 
information provided, as available.

Five-Factor Evaluation for Texas Fatmucket

    Information pertaining to the Texas fatmucket in relation to the 
five factors provided in section 4(a)(1) of the Act is discussed below.
    Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range.
    The decline of mussels in Texas and across the United States is 
primarily the result of habitat loss and degradation (Neves 1991, pp. 
252, 265; Howells et al. 1996, pp. 21-22). Chief among the causes of 
mussel decline in Texas are the effects of impoundments, sedimentation, 
dewatering, sand and gravel mining, and chemical contaminants (Neck 
1982a, pp. 33-35; Howells et al. 1996, pp. 21-22; Winemiller et al. pp. 
17-18). These threats are discussed below.
Impoundments
    A major factor in the decline of freshwater mussels across the 
United States has been the large-scale impoundment of rivers (Vaughn 
and Taylor 1999, p. 913). Dams are the source of numerous threats to 
freshwater mussels: They block upstream and downstream movement of 
species by blocking host fish movement; they eliminate or reduce river 
flow within impounded areas, thereby trapping silts and causing 
sediment deposition; and dams change downstream water flow timing and 
temperature, decrease habitat heterogeneity, and affect normal flood 
patterns (Layzer et al. 1993, pp. 68-69; Neves et al. 1997, pp. 63-64; 
Watters 2000, pp. 261-264; Watters 1996, p. 80). Within reservoirs (the 
impounded waters behind dams), the decline of freshwater mussels has 
been attributed to sedimentation, decreased dissolved oxygen, and 
alteration of resident fish populations (Neves et al. 1997, pp. 63-64; 
Pringle et al. 2000, pp. 810-815; Watters 2000, pp. 261-264). Dams 
significantly alter downstream water quality and stream habitats (Allan 
and Flecker 1993, p. 36; Collier et al. 1996, pp. 1, 7) resulting in 
negative effects to tailwater (the area downstream of a dam) mussel 
populations (Layzer et al. 1993, p. 69; Neves et al. 1997, p. 63; 
Watters 2000, pp. 265-266). Below dams, mussel declines are associated 
with changes and fluctuation in flow regime, scouring and erosion of 
stream channels, reduced dissolved oxygen levels and water 
temperatures, and changes in resident fish assemblages (Williams et al. 
1992, p. 7; Layzer et al. 1993, p. 69; Neves et al. 1997, pp. 63-64; 
Pringle et al. 2000, pp. 810-815; Watters 2000, pp. 265-266). Numerous 
dams have been constructed throughout the Colorado, Guadalupe, Brazos, 
and Nueces-Frio River systems within the range of all five mussels 
addressed in this finding (Stanley et al. 1990, p. 61).
    Population losses due to the effects of dams and impoundments have 
likely contributed more to the loss of diversity and abundance of 
freshwater mussels across Texas, including the Texas fatmucket, than 
any other factor. Stream habitat throughout nearly all of the range of 
Texas fatmucket has been affected by numerous impoundments, leaving 
generally short, isolated patches of remnant habitat between dams. 
Impoundments have resulted in profound changes to the nature of the 
rivers, primarily replacing free-flowing river systems with a series of 
large reservoirs.
    There are no natural lakes within the range of the Texas fatmucket, 
nor has it ever been found in reservoirs. Surveys of the reservoirs on 
the Guadalupe and Colorado Rivers have been ongoing since at least 
1992, and no evidence of live or dead Texas fatmucket has been found in 
any reservoir (Howells 1994, pp. 1-20; 1995, pp. 1-50; 1996, pp. 1-45; 
1997a, pp. 1-58; 1998, pp. 1-30; 1999, pp. 1-34; 2000a, pp. 1-56; 2001, 
pp. 1-50; 2002a, pp. 1-28; 2003, pp. 1-42; 2004, pp. 1-48; 2005, pp. 1-
23; 2006, pp. 1-106; Karatayev and Burlakova 2008, pp. 1-47; Burlakova 
and Karatayev 2010a, pp. 1-30; 2011, pp. 1-8), further indicating this 
species is not tolerant of impoundments.
    Impoundments occur throughout the range of the Texas fatmucket. The 
majority of the Nueces-Frio, Guadalupe, San Antonio, Colorado, and 
Brazos Rivers, as well as many tributaries, are now impounded. There 
are 31 major reservoirs within the Colorado River basin, with another 
reservoir (Goldthwaite Reservoir) being considered on the Colorado 
River in Mills and San Saba Counties; this reservoir was the number one 
recommendation in the water plan for the region (Texas Water 
Development Board (TWDB) 2011, p. 4-85). There are 29 reservoirs 
throughout the Guadalupe River basin and 34 reservoirs throughout the 
San Antonio River basin, each with a storage capacity of 3000 acre-feet 
or more, and many smaller reservoirs (Exelon 2010, p. 2.3-4). The 
majority of the large dams were

[[Page 62178]]

constructed for power generation, flood control, and water supply, 
primarily by the Lower Colorado River and Guadalupe-Blanco River 
Authorities, beginning in the early twentieth century (Guadalupe-Blanco 
River Authority 2011, p. 1; Lower Colorado River Authority (LCRA) 
2011a, p. 1). These, and numerous smaller dams, occur throughout the 
Colorado and Guadalupe River basins and have resulted in ongoing 
destruction and modification of Texas fatmucket habitat and the 
curtailment of its range.
    Dams threaten freshwater mussels in several ways. First, they can 
prevent the movement of freshwater mussel host fish. The overall 
distribution of mussels is a function of the dispersal of their hosts 
(Watters 1996, p. 83). For example, Watters (1996, p. 80) found that 
the distributions of the fragile papershell (Leptodea fragilis) and 
pink heelsplitter (Potamilus alatus) in five midwestern rivers were 
determined by the presence of low-head dams. These dams were non-
navigable (without locks), lacked fish ladders, and varied in height 
from 1 to 17.7 m (3 ft to 58 ft), and the host fish could not disperse 
through them. Although the distribution of mussels may depend on many 
ecological factors, the evidence presented in Watters (1996, pp. 79-85) 
illustrates that dams as small as 1 m (3 ft) high can limit the 
distribution of mussels. There are many dams that occur throughout the 
range of the Texas fatmucket that lack fish ladders and may be a 
barrier to the movement of fish hosts and, therefore, the distribution 
of mussels. Because the Texas fatmucket populations are all separated 
by dams of various sizes that are not passable by fish, the mussel is 
unable to disperse from its current occupied range through host fish 
migration.
    Dams also alter aquatic habitat within the resulting impoundments. 
It is well documented that many mussel species that are adapted to 
flowing water stream environments do poorly in the altered aquatic 
conditions found within impoundments (Williams et al. 1992, p. 7; 
Vaughn and Taylor 1999, p. 913). Once a dam is constructed, the 
original river channel upstream remains intact but under much deeper 
water with much lower velocities. As water velocity decreases, water 
loses its ability to carry sediment; sediment falls to the substrate, 
eventually smothering mussels that cannot adapt to soft substrates 
(Watters 2000, p. 263). Over time, the original mussel species 
composition of the stream channel may be eliminated or changed in favor 
of silt-tolerant species (Watters 2000, p. 264). The mussel community 
may be altered from one with many different species to a community 
dominated by one to several very common species (Neck 1982b, p. 174). 
Texas fatmucket does not occur in reservoirs, indicating it is not 
tolerant of lentic conditions, and it is now extirpated from impounded 
areas where it occurred prior to inundation. The inundation of stream 
habitat by impoundments is a likely cause of the reduction in the 
distribution of the Texas fatmucket. The presence of the impoundments 
has caused the permanent loss of Texas fatmucket habitat throughout its 
range.
    The loss of seven freshwater mussel species native to Texas, 
including Texas fatmucket and golden orb, due to impoundment 
construction was documented on the Medina River (Neck 1989, p. 323). 
The Medina River was impounded in 1913 by construction of Medina Dam, 
and now only three different species of mussels, all of which are 
tolerant of lentic habitats, occur in the impounded area. The bottom of 
Medina Lake now consists of moderate and steep limestone slopes and 
excessive silt deposits, whereas before it was most likely made up of a 
combination of silt, sand, and gravel substrates. Most mussels native 
to the Medina River were unable to adapt to the change in flowing water 
and substrate conditions (Neck 1989, p. 323), including the Texas 
fatmucket, which is no longer found in the river.
    Mussels downstream of impoundments are often affected through 
changes in fish host availability, water quality (particularly lower 
water temperatures), habitat structure, and stream channel scouring 
(Vaughn and Taylor 1999, p. 916). The release of cold water from the 
hypolimnion (deeper and colder layer of water in reservoirs) can 
decrease the occurrence of fish species adapted to warm water and 
increase the occurrence of fish species adapted to colder water 
(Edwards 1978, pp. 73-75). This changes the species composition of 
suitable host fish and may prevent mussels from completing an essential 
part of their reproductive cycle. This has been demonstrated by the 
extirpation of mussel species from several rivers on the eastern 
seaboard of the United States, which has been linked to the 
disappearance of appropriate host fish; the reintroduction of the host 
fish to rivers has enabled mussel species to recolonize areas (Kat and 
Davis 1984, p. 174). In addition, because mussel reproduction is 
temperature dependent (Watters and O'Dee 1999, pp. 455-456), it is 
likely that individual mussels living in cold waters downstream of dam 
releases may reproduce less frequently, if at all (Layzer et al. 1993, 
p. 69). Low water temperatures can also significantly delay or prevent 
metamorphosis (Watters and O'Dee 1999, pp. 454-455) and glochidial 
release, which is often triggered by water temperature (Watters and 
O'Dee 2000, p. 136).
    Similar changes in water temperatures downstream of dams may be 
responsible for the loss of some Texas fatmucket populations. For 
example, Canyon Reservoir on the Guadalupe River in Comal County is a 
deep impoundment built in 1964 that has hypolimnetic water releases. 
Temperature monitoring stations throughout the Guadalupe River basin 
show that maximum temperatures above Canyon Reservoir averaged 29.6 
degrees Celsius ([deg]C) (85.3 degrees Fahrenheit ([deg]F)); the 
maximum stream temperatures below the reservoir averaged only 19.7 
[deg]C (67.5 [deg]F) (Edwards 1978, p. 72). After impoundment, 
dissolved oxygen and water temperature dropped, with an accompanying 
drop in mussel numbers and species diversity (Young et al. 1976, p. 
216). According to historical museum records analyzed by Randklev et 
al. (2010b, pp. 1-32), the Texas fatmucket once occurred in this area 
of the Guadalupe River prior to the construction of Canyon Reservoir. 
The Guadalupe River and Canyon Lake in Comal and Kendall Counties were 
surveyed in 2009, and no live or recently dead Texas fatmucket were 
found (Burlakova and Karatayev 2010a, pp. 12-13). We reasonably 
conclude that the loss of the Texas fatmucket from this area was caused 
by the changes to the aquatic habitat of the Guadalupe River from the 
effects of Canyon Reservoir. Many of the dams throughout the range of 
Texas fatmucket have hypolimnetic water releases, including Canyon 
Reservoir on the Guadalupe River (Magnelia 2001, p. 1), and Inks Lake, 
Lake LBJ (Schnoor and Fruh 1979, p. 506), and Lake Travis (Texas 
Natural Resource Conservation Commission 2001, p. 4) on the Colorado 
River, among others. We anticipate that changes in water temperatures 
from water released by these and other reservoirs also alter mussel 
habitats in streams, causing the elimination of mussel populations 
downstream.
    In addition to the temperature of water released from dams, highly 
fluctuating, turbulent tailwaters devoid of sediment will scour the 
riverbed downstream of dams, rendering the area without mussel habitat 
(Layzer et al. 1993, p. 69). Depending on the use of the dam, water 
levels may fluctuate on a regular interval (for hydroelectric purposes) 
or at random (for flood

[[Page 62179]]

control) (Watters 2000, p. 265). On the Colorado River, Inks Lake, Lake 
Marble Falls, Lake Buchanan, Lake Austin, Lake Travis, and Lady Bird 
Lake are each used for one or both of these purposes. Mortality of 
another rare mussel species in Texas, the Texas heelsplitter (Potamilus 
amphichaenus) was attributed to scheduled dewatering of the Neches 
River below B.A. Steinhagen Reservoir in east Texas (Neck and Howells 
1994, p. 15).
    Fluctuating water levels below dams also result in dramatic changes 
in water velocity. Downstream of Lake Livingston on the Trinity River 
in east Texas, for example, high-volume water discharges and abrupt 
stoppages of flow resulted in a river bed composed of large rocks and 
shifting sand (Neck and Howells 1994, p. 14); these kinds of habitat 
changes would be inhospitable to Texas fatmucket below the dams within 
its range. In some rivers this unstable zone may be extensive. For 
example, on the Brazos River downstream of Possum Kingdom Reservoir in 
Texas exhibited unstable substrate for 150 km (240 mi) below the dam 
(Yeager 1993, p. 68).
    In one study of the downstream effects of dams, Vaughn and Taylor 
(1999, p. 915) found a strong, gradual, linear increase in mussel 
species richness and abundance at sites on the Little River in Oklahoma 
downstream from Pine Creek Reservoir. Their research revealed that 
mussel species richness and total abundance did not begin to rebound 
until 20 km (12 mi) downstream of the impoundment and did not peak 
until 53 km (33 mi) downstream. They noted the most obvious difference 
since reservoir construction has been the alteration of the flow and 
temperature regimes, which gradually return to pre-impoundment levels 
with downstream distance from the dam. These alterations appear to have 
produced an extinction gradient of mussels that is most severe near the 
dam (Vaughn and Taylor 1999, p. 915). We expect similar effects on the 
Texas fatmucket and other Texas mussels downstream of dams.
    In one area on the Guadalupe River in Kerr County, a Texas 
fatmucket population once existed directly below a small dam (Howells 
1997a, p. 36), indicating the effects of the dam construction and 
closure were not immediately lethal. However, the population has been 
presumed extirpated since 1998 (Howells 2006, p. 71), and it is likely 
that fluctuating downstream flows from the dam contributed to the loss 
of this population.
    Dam construction also fragments the range of Texas fatmucket, 
leaving remaining habitats and populations isolated by the structures 
as well as by extensive areas of deep uninhabitable, impounded waters. 
These isolated populations are unable to naturally recolonize suitable 
habitat that may be impacted by temporary but devastating events, such 
as severe drought, floods, or pollution. Dams impound river habitats 
throughout almost the entire range of the species, and these 
impoundments have left short and isolated patches of remnant habitat, 
typically between impounded reaches.
    In summary, the widespread construction of dams has affected the 
Texas fatmucket throughout its range by significantly altering stream 
habitat both upstream and downstream of the dams by changing fish 
assemblages, water depths and velocities, water temperature, dissolved 
oxygen, substrate, and stream channels. The effects of dams are ongoing 
and continue to negatively impact the Texas fatmucket rangewide. 
Because of this loss of habitat and its effects on the populations, we 
find that the effects of impoundments are a threat to the Texas 
fatmucket.
Sedimentation
    Siltation and general sediment runoff is a pervasive problem in 
streams and has been implicated in the decline of stream mussel 
populations (Ellis 1936, pp. 39-40; Vannote and Minshall 1982, p. 4105; 
Dennis 1984, p. ii; Brim Box and Mossa 1999, p. 99; Fraley and Ahlstedt 
2000, pp. 193-194). Specific biological effects on mussels from 
excessive sediment include reduced feeding and respiratory efficiency 
from clogged gills (Ellis 1936, p. 40), disrupted metabolic processes, 
reduced growth rates, increased substrate instability, limited 
burrowing activity (Marking and Bills 1979, pp. 208-209; Vannote and 
Minshall 1982, p. 4106), physical smothering, and disrupted host fish 
attractant mechanisms (Hartfield and Hartfield 1996, p. 373). The 
primary effects of excess sediment on mussels are sublethal, with 
detrimental effects not immediately apparent (Brim Box and Mossa 1999, 
p. 101).
    The physical effects of sediment on mussel habitats are multifold 
and include changes in suspended material load; changes in streambed 
sediment composition from increased sediment production and runoff in 
the watershed; changes in the form, position, and stability of stream 
channels; changes in water depth or the width-to-depth ratio, which 
affects light penetration and flow regime; actively aggrading (filling) 
or degrading (scouring) channels; and changes in channel position that 
may leave mussels stranded (Brim Box and Mossa 1999, pp. 109-112).
    Increased sedimentation and siltation may explain, in part, why 
Texas fatmucket appear to be experiencing recruitment failure in some 
streams. Interstitial spaces (small openings between rocks and gravels) 
in the substrate provide essential habitat for juvenile mussels. When 
clogged with sand or silt, interstitial flow rates and spaces may 
become reduced (Brim Box and Mossa 1999, p. 100), thus reducing 
juvenile habitat availability. Juvenile freshwater mussels, including 
Texas fatmucket juveniles, burrow into interstitial substrates, making 
it particularly susceptible to degradation of this habitat.
    Even in 1959, both the Colorado and Guadalupe Rivers were noted as 
having high sedimentation rates from agricultural activities (Soil 
Conservation Service 1959, pp. 56, 59). Approximately 40 percent of 
U.S. river miles do not meet Clean Water Act standards due to excessive 
sediment loads (Environmental Protection Agency (EPA) 2000, p. 1), with 
agricultural activities being the primary source of sediment in streams 
(Waters 1995, p. 170). In general, sedimentation, resulting from 
unrestricted access by livestock, has been shown to be a significant 
threat to many streams and their mussel populations (Fraley and 
Ahlstedt 2000, p. 193). A primary land use throughout the range of the 
Texas fatmucket is grazing by cattle, sheep, and goats (Hersh 2007, p. 
11). Soil compaction, which reduces vegetative growth, from intensive 
grazing may reduce infiltration rates and increase runoff and erosion, 
and trampling of riparian vegetation increases the probability of 
erosion (Armour et al. 1994, p.10; Brim Box and Mossa 1999, p. 103).
    Another cause of increased sediments in streams is widespread brush 
removal, such as that of the native plant, Juniperus ashei (Ashe 
juniper), throughout central Texas. Juniperus ashei removal can cause a 
marked increase in sediment runoff into streams (Greer 2005, p. 76). 
The Texas State Soil and Water Conservation Board has a funding program 
specifically for Juniperus ashei removal in Blanco, Gillespie, Kerr, 
Kendall, and Travis Counties (Gillespie County Soil and Water 
Conservation District 2011, p. 1), which includes the watersheds of 
three known Texas fatmucket populations in Live Oak Creek, Threadgill 
Creek, and the upper Guadalupe River. In one example, Howells (2010f, 
p. 6) noted

[[Page 62180]]

increased sediment deposition after widespread Juniperus ashei removal 
upstream of the Texas fatmucket population in Live Oak Creek.
    Sedimentation may become an increasing threat to the Texas 
fatmucket in the Colorado and Guadalupe River basins as the Austin and 
San Antonio metro areas continue to expand. Activities associated with 
urbanization, such as road construction and increased impervious 
surfaces (surfaces that do not allow infiltration of rain water), can 
be detrimental to stream habitats (Couch and Hamilton 2002, p. 1). 
Runoff from increased impervious surfaces increases sediment loads in 
streams and destabilizes stream channels (Pappas et al. 2008, p. 151). 
Impervious surfaces also result in channel instability by accelerating 
stormwater runoff, which increases bank erosion and bed scouring, 
thereby further increasing downstream sedimentation (Brim Box and Mossa 
1999, p. 103). While erosion and sedimentation associated with road 
construction may be temporary, the existence of road crossings is shown 
to have ongoing impacts to mussel habitat. For example, in the 
Guadalupe River, road crossings were found to cause a long-term 
increase in sedimentation both upstream and downstream, as channel 
constriction reduced flow upstream, causing sediment deposition, and 
runoff from the road increased sedimentation downstream (Keen-Zebert 
and Curran 2009, p. 301). Urban development activities may also affect 
streams and their mussel fauna where adequate streamside buffers are 
not maintained and erosion from adjacent land is allowed to enter 
streams (Brainwood et al. 2006, p. 511).
    Large projects that reduce vegetative cover within the watersheds 
supporting Texas fatmucket populations can also increase sedimentation 
flowing into streams. For example, the Lower Colorado River Authority 
Transmission Services Corporation (LCRA TSC) is proposing to construct 
two new 345-kilovolt (kV) electric transmission line facilities between 
Tom Green (in the Colorado River basin near San Angelo) and Kendall 
Counties (in the Guadalupe River basin north of San Antonio) to provide 
electrical power to accommodate increased human populations (Clary 
2010, p. 1). All of the proposed project routes occur within the range 
of the Texas fatmucket. Two proposed segments would cross through Live 
Oak Creek, one through the San Saba River, and one through the upper 
Guadalupe River; all of these streams contain populations of the Texas 
fatmucket. The proposed project could negatively affect Texas fatmucket 
habitat if construction or maintenance of the transmission line 
requires removal of vegetation within the riparian zone and that 
removal results in an increase in sediment runoff into Live Oak Creek 
and the Guadalupe and San Saba Rivers (Clary 2010, pp. 7, 9, 15). 
Similar infrastructure development activities to accommodate Texas 
population growth are expected to be undertaken across the species' 
range and will likely lead to additional sources of sediment in the 
streams inhabited by the Texas fatmucket.
    Streams occupied by Texas fatmucket are subject to increasing 
levels of sedimentation from agricultural activities, instream sand and 
gravel mining, vegetation removal, and urbanization. All of these 
activities are ongoing throughout the range of the Texas fatmucket and 
are unlikely to decrease, resulting in significant threats to the Texas 
fatmucket.
Dewatering
    River dewatering can occur in several ways: Anthropogenic 
activities such as surface water diversions and groundwater pumping, 
and natural events, such as drought. Surface water diversions and 
groundwater pumping can lower water tables, reducing river flows and 
reservoir levels. When water levels in streams and reservoirs are 
lowered dramatically, it can result in mussels being stranded and dying 
in previously wetted areas. This is a particular concern within and 
below reservoirs where water levels are managed for purposes that 
result in water levels in the reservoir or downstream to rise or fall 
in very short periods of time, such as when hydropower facilities 
release water during peak energy demand periods. Rivers can also be 
dewatered to expedite construction activities, which happened in the 
upper Guadalupe River in Kerr County in 1998 for bridge construction; 
numerous Texas fatmuckets were exposed and desiccated (dried out and 
died) (Howells 1999, pp. 18-19).
    Drought can also severely affect Texas fatmucket populations. For 
example, near-record dry conditions in 2008, followed by a pattern of 
below-normal rainfall during the winter and spring of 2009, led to one 
of the worst droughts in recorded history for most of central Texas, 
including the range of the Texas fatmucket (Nielsen-Gammon and 
McRoberts 2009, p. 2). This drought's severity was exacerbated by 
abnormally high air temperatures, a likely effect of climate change, 
which has increased average air temperatures in Texas by at least 1 
[deg]C (1.8 [deg]F) (Nielsen-Gammon and McRoberts 2009, p. 22). The 
reservoirs within the Colorado River basin were extremely low during 
this time due to the drought (Clean Water Action 2011, p. 1), as were 
river levels. Minimal to no flow was recorded at numerous sites within 
the basin (U.S. Geological Survey (USGS) 2011a, p. 1). Four of the five 
current sites of the Texas fatmucket may have had very low flows during 
the 2009 drought, including populations in the San Saba, Llano, 
Pedernales, and Guadalupe Rivers (Howells 2010c, pp. 9-10). As low 
flows persist, mussels face oxygen deprivation, increased water 
temperature, and, ultimately, stranding (Golladay et al. 2004, p. 501). 
Only the Llano River has been surveyed since 2009, and the species 
persists in that river (Burlakova and Karatayev 2011, p. 1). Central 
Texas is currently experiencing another extreme drought, with rainfall 
between October 2010 and July 2011 being the lowest on record during 
those months (LCRA 2011c, p. 1), and the effects of this drought are 
being observed but are not yet fully known. As of the date of 
publication of this finding, the Llano River has nearly stopped flowing 
(Mashhood 2011, p. 1); this has undoubtedly affected Texas fatmucket 
populations in this river.
    We do not know the extent of the impacts of stream dewatering on 
the Texas fatmucket; however, because this species' populations are so 
small and isolated, the loss of numerous individuals at a site can have 
dramatic consequences to the population. Hydropower facilities, 
construction, surface water diversions, groundwater pumping, and 
drought are occurring throughout the range of the Texas fatmucket; 
therefore, the effects of dewatering are ongoing and unlikely to 
decrease in the future, resulting in significant threats to the Texas 
fatmucket.
Sand and Gravel Mining
    Sand and gravel mining (removing bed materials from streams) has 
been implicated in the destruction of mussel populations across the 
United States (Hartfield 1993, pp. 136-138). Sand and gravel mining 
causes stream instability by increasing erosion and turbidity (a 
measure of water clarity) and causing subsequent sediment deposition 
downstream (Meador and Layher 1998, pp. 8-9). These changes to the 
stream can result in large-scale changes to aquatic fauna, by altering 
habitat and affecting spawning of fish, mussels, and other aquatic 
species (Kanehl and Lyons 1992, pp. 4-11).
    Sedimentation and increased turbidity can accrue from instream 
mining activities. In the Brazos River, a gravel dredging operation was

[[Page 62181]]

documented as depositing sediment as far as 1.6 km (1 mi) downstream 
(Forshage and Carter 1973, p. 697). Accelerated streambank erosion and 
downcutting of streambeds are common effects of instream sand and 
gravel mining, as is the mobilization of fine sediments during sand and 
gravel extraction (Roell 1999, p. 7).
    Mining activities may threaten some local Texas fatmucket 
populations. Currently, one mining operation is permitted near the 
population in Onion Creek (TPWD 2008c, p. 1), and another in the Llano 
River watershed in Kimble County (TPWD 2008a, p. 1). The permits allow 
for repeated removal of sand and gravel at various instream locations. 
Two additional mining operations occur in historical habitat for the 
species--the mainstem Colorado River (U.S. Army Corps of Engineers 
(USACE) 2010, p. 2) and Johnson Creek (TPWD 2007a, p. 1).
    In areas where repeated mining occurs, an upstream progression of 
channel degradation and erosion (called headcutting) can occur (Meador 
and Layher 1998, p. 8). Headcutting may move miles upstream in a 
zipper-like fashion as the upper boundary of the modified area 
collapses. Headcutting can be found within the majority of rivers and 
streams in Texas, including within the Texas fatmucket's current and 
historical range (Kennon et al. 1967, p. 22). Headcuts induced by sand 
and gravel mining can cause dramatic changes in streambank and channel 
shape that may affect instream flow, water chemistry and temperature, 
bank stability, and siltation (Meador and Layher 1998, p. 8), all of 
which are harmful to freshwater mussels. Mussels are particularly 
vulnerable to channel degradation and sedimentation processes 
associated with headcutting due to their immobility (Pringle 1997, p. 
429).
    In addition to headcutting, mines that are located near stream 
channels are subject to the gravel pit being captured by the stream 
during flood events or due to gradual channel migration (Simmang and 
Curran 2006, p. 1). For example, two gravel mines along the Colorado 
River downstream of Austin were inundated; one by stream channel 
migration in 1984, one by stream capture in 1991 (Simmang and Curran 
2006, p. 1). Once captured by the mainstem river, gravel mines 
contribute large amounts of suspended sediment to the river, causing 
additional turbidity and sedimentation and further degrading mussel 
habitat.
    Two Texas fatmucket populations in the mainstem Colorado River and 
Johnson Creek may be currently affected by sand and gravel mining. 
These activities occur over a long period of time, destabilizing 
habitat and altering substrates and banks both upstream and downstream. 
Altered habitat will cause a decrease in the likelihood of 
recolonization by mussels after the activity has been completed. 
Therefore, the effects of sand and gravel mining are an ongoing threat 
to the Texas fatmucket.
Chemical Contaminants
    Chemical contaminants are ubiquitous throughout the environment and 
are a major reason for the decline of freshwater mussel species 
nationwide (Richter et. al. 1997, p. 1081; Strayer et al. 2004, p. 436; 
Wang et al. 2007a, p. 2029). Chemicals enter the environment through 
both point and nonpoint discharges, including spills, industrial 
sources, municipal effluents, and agriculture runoff. These sources 
contribute organic compounds, heavy metals, pesticides, herbicides, and 
a wide variety of newly emerging contaminants to the aquatic 
environment. As a result, water quality can be degraded to the extent 
that mussel populations are adversely affected.
    Chemical and oil spills can be especially devastating to mussels 
because they may result in exposure of a relatively immobile species to 
elevated concentrations that far exceed toxic levels. Acute and chronic 
exposure to oil spills in freshwater systems is largely understudied; 
therefore, little information is available on effects of oil spills on 
freshwater ecosystems (Harrel 1985, p. 223; Bhattacharyya et al. 2002, 
p. 205). Oil is retained much longer in marshes and other low-energy 
environments, such as slow-moving streams and rivers, than on wave-
swept coasts (Bhattacharyya et al. 2002, p. 205). Oils have been found 
in sediments at low energy sites as much as 5 years after the 
occurrence of spills, and they may be released into the water column 
long after the initial spill. Oil may have various chronic effects on 
water-column and benthic (bottom-dwelling) species. These effects 
include sensory disruption, behavioral and developmental abnormalities, 
and reduced fertility (Bhattacharyya et al. 2002, p. 205). Oil spilled 
on the water surface may also limit oxygen exchange, coat the gills of 
aquatic organisms, and cause pathological lesions on respiratory 
surfaces, thereby affecting respiration in aquatic organisms. Effects 
of oil on freshwater mussels may result from oil settling on the 
sediment surfaces and accumulating in the sediment. This can prevent 
invertebrate colonization (Bhattacharyya et al. 2002, p. 205). Complete 
recovery of benthic communities may be a matter of years, with 
communities in the meantime consisting solely of pollutant-tolerant 
organisms (Bhattacharyya et al. 2002, p. 205). Oil spills can occur 
from on-site accidents (tank, pipeline spills) or from tanker truck 
accidents within watersheds occupied by Texas fatmucket. For example, 
450 gallons of oil were spilled into Lake Bastrop, a reservoir on a 
tributary to the Colorado River, in February 2011 (Cihock 2011, p. 1).
    Exposure of mussels to persistent low concentrations of 
contaminants likely to be found in aquatic environments can also 
adversely affect mussels and their populations. Such concentrations may 
not be immediately lethal, but over time can result in mortality, 
reduced filtration efficiency, reduced growth, decreased reproduction, 
changes in enzyme activity, and behavioral changes to all mussel life 
stages (Naimo 1995, pp. 351-352; Baun et al. 2008, p. 392). Frequently, 
procedures that evaluate the ``safe'' concentration of an environmental 
contaminant (for example, national water quality criteria) do not have 
data for freshwater mussel species or do not consider data that are 
available for freshwater mussels (March et al. 2007, pp. 2066-2067, 
2073).
    One chemical that is particularly toxic to early life stages of 
mussels is ammonia. Sources of ammonia include agricultural activities 
(animal feedlots and nitrogenous fertilizers), municipal wastewater 
treatment plants, and industrial waste (Augspurger et al. 2007, p. 
2026), as well as precipitation and natural processes (decomposition of 
organic nitrogen) (Goudreau et al. 1993, p. 212; Hickey and Martin 
1999, p. 44; Augspurger et al. 2003, p. 2569; Newton 2003, p. 2543). 
Therefore, ammonia is considered a limiting factor for survival and 
recovery of some mussel species due to its ubiquity in aquatic 
environments, high level of toxicity, and because the highest 
concentrations typically occur in mussel microhabitats (Augspurger et 
al. 2003, p. 2574). In addition, studies have shown that ammonia 
concentrations increase with increasing temperature and low-flow 
conditions (Cherry et al. 2005, p. 378; Cooper et al. 2005, p. 381), 
which may be exacerbated during low-flow events in streams. Within the 
range of Texas fatmucket, high ammonia levels are common, either 
chronically, such as in Elm Creek, which is listed as impaired due to 
high ammonia concentrations (Texas Commission on Environmental Quality 
(TCEQ) 2010a, p. 294), or due to spills. A wastewater leak in August 
2010 spilled approximately 380,000

[[Page 62182]]

liters (L) (100,000 gallons (gal)) of sewage into Elm Creek (Bramlette 
and Cosel 2010, p. 1); ammonia is present in high concentrations in 
sewage, among other pollutants. Additionally, a sewage spill in 2008 in 
Onion Creek discharged nearly 380,000 L (100,000 gal), and another 
sewage spill occurred in April 2011 in Quinlan Creek, a tributary to 
the Guadalupe River near the Kerr County population (MacCormack 2011, 
p. 1). High ammonia levels from chronic sources as well as from spills 
may be affecting Texas fatmucket populations.
    In addition to ammonia, agricultural sources of chemical 
contaminants include two broad categories that have the potential to 
adversely affect mussel species: Nutrients and pesticides. High amounts 
of nutrients, such as nitrogen and phosphorus, in streams can stimulate 
excessive plant growth (algae and periphyton, among others), which in 
turn can reduce dissolved oxygen levels when dead plant material 
decomposes. Nutrient over-enrichment in streams is primarily a result 
of runoff of fertlizer and animal manure from livestock farms, 
feedlots, and heavily fertilized row crops (Peterjohn and Correll 1984, 
p. 1471). Over-enriched conditions are exacerbated by low-flow stream 
conditions, such as those experienced during typical summer season 
flows. Bauer (1988, p. 244) found that excessive nitrogen 
concentrations can be detrimental to the adult freshwater pearl mussel 
(Margaritifera margaritifera), as was evident by the positive linear 
relationship between mortality and nitrate concentrations. Also, a 
study of mussel life span and size (Bauer 1992, p. 425) showed a 
negative correlation between growth rate and high nutrient 
concentrations, and longevity was reduced as the concentration of 
nitrates increased. Juvenile mussels in interstitial habitats are 
particularly affected by depleted dissolved oxygen levels resulting 
from nutrient over-enrichment (Sparks and Strayer 1998, p. 133). The 
Texas fatmucket occurs within the Concho River watershed, which has 
been documented as having particularly high nitrates for nearly 20 
years, likely due to intensive agriculture in the area (Texas Clean 
Rivers Program 2008, p. 2), which may be affecting the Texas fatmucket 
population.
    Mussels are also affected by metals (Keller and Zam 1991, p. 543) 
such as cadmium, chromium, copper, mercury, and zinc, which can 
negatively affect biological processes such as growth, filtration 
efficiency, enzyme activity, valve closure, and behavior (Keller and 
Zam 1991, p. 543; Naimo 1995, pp. 351-355; Jacobson et al. 1997, p. 
2390; Valenti et al. 2005, p. 1244). Metals occur in industrial and 
wastewater effluents and are often a result of atmospheric deposition 
from industrial processes and incinerators. Studies have shown that 
copper can have toxic effects on glochidia and juvenile freshwater 
mussels (Wang et al. 2007a, pp. 2036-2047; Wang et al. 2007b, pp. 2048-
2056). In the range of Texas fatmucket, high copper concentrations have 
been recorded in fish in the lower Guadalupe River and San Antonio 
River (Lee and Schultz 1994, p. 8). While these high levels of copper 
in fish are not directly informative of the level of copper within the 
habitat of the Texas fatmucket, these observations demonstrate that 
copper levels are likely high in the lower Guadalupe and San Antonio 
Rivers. Because we know that copper contamination in water can lead to 
death of mussels, we conclude that the copper may be adversely 
affecting Texas fatmucket.
    Mercury is another heavy metal that has the potential to negatively 
affect mussel populations, and it is widely distributed in the 
environment. Mercury has been detected throughout aquatic environments 
as a product of municipal and industrial waste and atmospheric 
deposition from coal burning plants. Rainbow mussel (Villosa iris) 
glochidia have been demonstrated to be more sensitive to mercury than 
juvenile mussels, with the median lethal concentration value of 14 
parts per billion (ppb) for glochidia, compared to 114 ppb for the 
juvenile life stages (Valenti 2005, p. 1242). The chronic toxicity 
tests conducted determined that juveniles exposed to mercury greater 
than or equal to 8 ppb exhibited reduced growth. Acute mercury toxicity 
was determined to be the cause of extirpation of a diverse mussel 
community for a 112 km (70 mi) portion of the North Fork Holston River 
in Virginia (Brown et al. 2005, pp. 1455-1457). Mercury has been 
documented throughout the Guadalupe and San Antonio Rivers, with 
particularly high concentrations in fish in the upper reaches of both 
rivers (Lee and Schultz 1994, p. 8). As with copper, we do not have 
information on the concentration of mercury that Texas fatmucket is 
being exposed to in these streams, but the higher than expected levels 
in fish indicate high mercury levels in the area, which may be 
adversely affecting Texas fatmucket.
    Pesticides are another source of contaminants in streams. Elevated 
concentrations of pesticides frequently occur in streams due to 
pesticide runoff, overspray application to row crops, and lack of 
adequate riparian buffers. The timing of agricultural pesticide 
applications in the spring often coincides with the reproductive and 
early life stages of mussels, which may increase the vulnerability of 
mussels to pesticides (Bringolf et al. 2007a, p. 2094). Little is known 
regarding the effect of currently used pesticides to freshwater mussels 
even though some pesticides, such as glyphosate (active ingredient in 
Roundup[supreg]), are used globally. Recent studies tested the toxicity 
of glyphosate, its formulations, and a surfactant (MON 0810) used in 
several glyphosate formulations, to early life stages of the fatmucket 
(Lampsilis siliquoidea) (Bringolf et al. 2007a, p. 2094), a freshwater 
mussel closely related to the Texas fatmucket. Studies conducted with 
fatmucket juveniles and glochidia determined that the surfactant was 
the most toxic of the compounds tested and that fatmucket glochidia 
were the most sensitive organisms tested to date (Bringolf et al. 
2007a, p. 2094). Roundup[supreg], technical grade glyphosate 
isopropylamine salt, and isopropylamine were also acutely toxic to 
juveniles and glochidia (Bringolf et al. 2007a, p. 2097). These 
commonly applied pesticides may be adversely affecting Texas fatmucket 
populations.
    The effects of other widely used pesticides, including atrazine, 
chlorpyrifos, and permethrin, on glochidia and juvenile life stages 
have also recently been studied (Bringolf et al. 2007b, p. 2101). 
Environmentally relevant concentrations (concentrations that may be 
found in streams) of permethrin and chlorpyrifos were found to be toxic 
to glochidia and juvenile fatmucket (Bringolf et al. 2007b, pp. 2104-
2106). Commonly applied pesticides are a threat to mussels as a result 
of their widespread use. All of these pesticides are commonly used on 
agricultural lands throughout the range of the Texas fatmucket, which 
may be adversely affecting the species.
    A potential, but undocumented, threat to freshwater mussels, 
including Texas fatmucket, are compounds referred to as ``emerging 
contaminants'' that are being detected in aquatic ecosystems at an 
increasing rate. These include pharmaceuticals, hormones, and other 
organic contaminants that have been detected downstream from urban 
areas and livestock production (Kolpin et al. 2002, p. 1202) and have 
been shown to affect fish behavior (TCEQ 2010b, p. 3). In samples of 
the Trinity River, for example, compounds such as antidepressants, 
antihistamines, blood pressure lowering medication, anti-seizure 
medication, and antimicrobial compounds were all detected during a 2006 
study (TCEQ 2010b, pp. 27-28). A

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large potential source of these emerging contaminants is wastewater 
being discharged through both permitted (National Pollutant Discharge 
Elimination System (NPDES)) and non-permitted sites within the Colorado 
and Guadalupe River systems. Although streams within the range of Texas 
fatmucket have not been tested for these emerging contaminants, 
permitted discharge sites are ubiquitous in watersheds with Texas 
fatmucket populations, providing many opportunities for contaminants to 
impact the species.
    A study in the Blanco River found that mussels may be adversely 
affected by sewage effluent (Horne and McIntosh 1979, p. 132). Ammonia 
levels below the outfall were three times higher than the levels above 
the outfall and were higher than recently determined toxicity values of 
ammonia for mussels (Augsperger et al. 2003, p. 2572). The river was 
nutrient-enriched for miles downstream, and mussels were less abundant 
below the outfall than above (Horne and McIntosh 1979, pp. 124-125, 
132). Texas fatmucket have not been found alive in the Blanco River 
since 1978.
    Texas Commission on Environmental Quality (TCEQ) data for 2010 
indicated that 26 of the 98 assessed water bodies within the Texas 
fatmucket's historical and current range did not meet surface water 
quality standards and were classified as impaired water bodies under 
the Clean Water Act (Texas Clean Rivers Program 2010a, p. 5; 2010b, p. 
13), including Elm Creek, due to high ammonia. These water bodies were 
impaired with dissolved solids, nitrates, bacteria, low dissolved 
oxygen, aluminum, sulfates, selenium, chloride, and low pH associated 
with agricultural, urban, municipal, and industrial runoff. Of these, 
nitrates and low dissolved oxygen pose the greatest threat to Texas 
fatmucket, as discussed above. Chemical contaminants, such as oil, 
ammonia, copper, mercury, nutrients, pesticides, and other compounds, 
are currently a threat to the Texas fatmucket. The species is 
vulnerable to acute contamination from spills, which have been 
documented in four of the seven remaining populations, as well as 
chronic contaminant exposure, which is occurring rangewide.
Summary of Factor A
    The reduction in numbers and range of the Texas fatmucket is 
primarily the result of the long-lasting effects of habitat alterations 
such as the effects of impoundments, sedimentation, dewatering, sand 
and gravel mining, and chemical contaminants. Impoundments occur 
throughout the range of the species and have far-reaching effects both 
up- and downstream. Both the Colorado and Guadalupe River systems have 
experienced a large amount of sedimentation from agriculture, mining, 
urban development, and widespread Juniperus ashei removal. Sand and 
gravel mining affects Texas fatmucket habitat by increasing 
sedimentation and channel instability downstream and causing 
headcutting upstream. Finally, chemical contaminants have been 
documented throughout the range of the species and are significant 
concern to Texas fatmucket. Based upon our review of the best 
commercial and scientific data available, we conclude that the present 
or threatened destruction, modification, or curtailment of its habitat 
or range is an immediate threat of high magnitude to the Texas 
fatmucket.
    Factor B. Overutilization for Commercial, Recreational, Scientific, 
or Educational Purposes.
    The Texas fatmucket is not a commercially valuable species and has 
never been harvested in Texas as a commercial mussel species (Howells 
2010c, p. 11), although in the Llano River shells were found that were 
apparently collected by anglers for use as bait (Howells 1996, p. 22; 
2010c, p. 11). Additionally, the Elm Creek population is suspected to 
have declined in part due to the publication of detailed location 
information, which may have inspired collectors to visit the site 
(Howells 2009, pp. 5-6). Scientific collecting is not likely to be a 
significant threat to the status of the species, although disturbing 
gravid females can result in glochidial loss and subsequent 
reproductive failure. Additionally, handling has been shown to reduce 
shell growth in other mussel species, including several other species 
of Lampsilis (Haag and Commens-Carson 2008, pp. 505-506). Repeated 
handling by researchers may adversely affect Texas fatmucket 
individuals, but these activities are occurring rarely and are not 
likely to be a threat to populations. Handling for scientific purposes 
contributes to the long-term conservation of the species.
    We do not have any evidence of risks to the Texas fatmucket from 
overutilization for commercial, recreational, scientific, or 
educational purposes, and we have no reason to believe this factor will 
become a threat to the species in the future. Based upon the best 
scientific and commercial information available, we conclude that 
overutilization for commercial, recreational, scientific, or 
educational purposes does not pose a significant threat to the Texas 
fatmucket.
    Factor C. Disease and Predation.
Disease
    Little is known about disease in freshwater mussels. However, 
disease is believed to be a contributing factor in documented mussel 
die-offs in other parts of the United States (Neves 1987, pp. 11-12). 
Diseases have not been documented or observed during any studies of 
Texas fatmucket.
Predation
    Raccoons have preyed on individual Texas fatmuckets stranded by low 
waters or deposited in shallow water or on bars following flooding or 
low water periods (Howells 2010c, p. 12). Predation of Texas fatmucket 
by raccoons may be occurring occasionally but there is no indication it 
is a significant threat to the status of the species.
    Some species of fish feed on mussels, such as common carp (Cyprinus 
carpio), freshwater drum, and redear sunfish (Lepomis microlophus), all 
of which are common throughout the range of Texas fatmucket (Hubbs et 
al. 2008, pp. 19, 45, 53). Common species of flatworms are voracious 
predators of newly metamorphosed juvenile mussels of many species 
(Zimmerman et al. 2003, p. 30), including other species in the genus 
Lampsilis (Delp 2002, pp. 12-13). Predation is a normal aspect of the 
population dynamics of a healthy mussel population; however, predation 
may amplify declines in small populations.
Summary of Factor C
    Disease in freshwater mussels is poorly known, and we do not have 
any information indicating it is a threat to the Texas fatmucket. 
Additionally, while predation is likely occurring within Texas 
fatmucket populations, it is a natural ecological interaction and we 
have no information indicating the extent of such predation is large 
enough to be a threat to populations of Texas fatmucket. Based upon the 
best scientific and commercial information available, we conclude that 
disease or predation is not a threat to the Texas fatmucket.
    Factor D. The Inadequacy of Existing Regulatory Mechanisms.
    The Act requires us to examine the adequacy of existing regulatory 
mechanisms with respect to threats that may place the Texas fatmucket 
in danger of extinction or increase its likelihood of becoming so in 
the future. Existing regulatory mechanisms that could affect threats to 
the Texas

[[Page 62184]]

fatmucket include State and Federal laws such as the Texas Threatened 
and Endangered Species regulations, Texas freshwater mussel 
sanctuaries, State and Federal sand and gravel mining regulations, and 
regulation of point and non-point source pollution.
Texas Threatened and Endangered Species Regulations
    On January 8, 2010, the Texas Parks and Wildlife Commission placed 
15 species of freshwater mussels, including the Texas fatmucket, on the 
State threatened list (Texas Register 2010, pp. 6-10). Section 68.002 
of the Texas Parks and Wildlife (TPW) Code and Section 65.171 of the 
Texas Administrative Code (TAC) prohibit the direct take of a 
threatened species, except under issuance of a scientific collecting 
permit. ``Take'' is defined in Section 1.101(5) of the TPW Code as 
collect, hook, hunt, net, shoot, or snare, by any means or device, and 
includes an attempt to take or to pursue in order to take. While this 
law protects individuals from take, it is difficult to enforce and does 
not provide any protection for Texas fatmucket habitat. Moreover, our 
assessment finds that the species is not threatened by take (see Factor 
B above). There are no State provisions under the Texas Threatened and 
Endangered Species Regulations for reducing or eliminating the threats 
(see Factor A above) that may adversely affect Texas fatmucket or its 
habitat. In addition, these State regulations do not call for 
development of a recovery plan that will restore and protect existing 
habitat for the species. For these reasons, we find that existing Texas 
regulatory mechanisms for State-listed threatened species are currently 
inadequate to protect Texas fatmucket and its habitat or to prevent 
further decline of the species.
Freshwater Mussel Sanctuaries
    The TPWD has designated specific areas of streams and reservoirs as 
no-harvest mussel sanctuaries (31 TAC, part 2, chapter 57, subpart B, 
Rule 57.157). The locations of the designated mussel sanctuaries were 
selected because they support populations of rare and endemic mussel 
species or are important for maintaining, repopulating, or allowing 
recovery of mussels in watersheds where they have been depleted. As a 
result of the designation of mussel sanctuaries, four of the Texas 
fatmucket populations are protected from harvesting disturbance of 
other species (Howells 2010f, p. 12). Unfortunately, mussel sanctuaries 
only restrict the harvest of mussels and do not address other 
activities that may affect mussels or their habitats. Therefore, these 
designations provide no regulatory mechanisms to protect Texas 
fatmucket from habitat alteration.
State Sand and Gravel Mining Regulations
    TPWD has been responsible for regulating the ``disturbance of 
taking'' streambed materials since 1911 (Meador and Layher 1998, p. 11) 
and has issued several permits for ongoing activities within the Texas 
fatmucket range (for more information on the effects of sand and gravel 
mining on Texas fatmucket, please refer to ``Sand and Gravel Mining'' 
under Factor A in Five-Factor Evaluation for Texas Fatmucket). In 
addition to authorized activities, there are ongoing unauthorized sand 
and gravel mining activities within the range of Texas fatmucket. For 
example, the LCRA, which monitors water quality permit applications 
submitted through other agencies (LCRA 2011b, p. 1), found unpermitted 
sand removal from the Llano River in Llano County during a site visit 
in 2010 (Lehman 2010, p. 1). This site is located upstream from a known 
population of the Texas fatmucket and other rare mussels (Howells 1994, 
p. 6), and the sand removal may have increased turbidity and 
sedimentation downstream within Texas fatmucket habitat. Sand and 
gravel mining may be one of the least regulated of all mining 
activities (Meador and Layher 1998, p. 10).
Clean Water Act
    The U.S. Army Corps of Engineers (USACE) retains oversight 
authority and requires a permit for gravel and sand mining activities 
that deposit fill into streams under section 404 of the Clean Water Act 
(33 U.S.C. 1251 et seq.). Additionally, a permit is required under 
section 10 of the Rivers and Harbors Act (33 U.S.C. 401 et seq.) for 
navigable waterways. However, many mining operations do not fall under 
these two categories. For example, nationwide permits are issued by the 
USACE for types of projects that are presumed to have minimal 
environmental impacts. However, projects permitted by nationwide 
permits, such as small mining operations, may have cumulative effects 
on aquatic species like the Texas fatmucket through increased 
sedimentation and channel instability.
    Point source discharges of potential contaminants within the range 
of the Texas fatmucket have been reduced since the inception of the 
Clean Water Act, but this reduction may not provide adequate protection 
for filter-feeding organisms that can be affected by extremely low 
levels of contaminants (see ``Chemical Contaminants'' under Factor A in 
the Five-Factor Evaluation for Texas Fatmucket section). The EPA's 
established water quality criteria may not be protective of mussels. 
Current water quality standards applied by EPA were established to be 
protective of aquatic life; however, freshwater mussels were not used 
to develop these standards (EPA 2005, p. 5), and current research 
reveals mussels to be more sensitive to many aquatic pollutants than 
the tested organisms (Augsperger et al. 2007, p. 2025). For example, 
Augspurger et al. (2003, p. 2572) and Sharpe (2005, p. 28) suggested 
that the criteria for ammonia may not be sufficient to prevent impacts 
to mussels under current and future climate conditions. In addition, 
chronic copper concentrations lethal to juvenile freshwater mussels 
have been shown to be less than the EPA's 1996 chronic water quality 
criterion for copper (Wang et al. 2007b, pp. 2052-2055), and, as stated 
above (see ``Chemical Contaminants'' under Factor A in Five-Factor 
Evaluation for Texas Fatmucket), high copper concentrations have been 
documented in the lower Guadalupe and San Antonio Rivers (Lee and 
Schultz 1994, p. 8). Based on this information, the existing EPA water 
quality criteria may not be sufficient to prevent negative effects to 
the Texas fatmucket.
    Nonpoint source pollution such as sedimentation and chemical 
contaminantation is considered a significant threat to Texas fatmucket 
habitat; however, the Clean Water Act does not adequately protect Texas 
fatmucket habitat from nonpoint source pollution, because most 
activities that cause nonpoint source pollution are not regulated under 
the Clean Water Act.
Summary of Factor D
    Despite some State and Federal laws protecting the species and 
water quality, the Texas fatmucket continues to decline due to the 
effects of habitat destruction, poor water quality, contaminants, and 
other factors. The regulatory measures described above are not 
sufficient to significantly reduce or remove the threats to the Texas 
fatmucket. Based upon our review of the best commercial and scientific 
data available, we conclude that the lack of existing regulatory 
mechanisms is an immediate threat of moderate magnitude to the Texas 
fatmucket.
    Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence.
    Other natural and manmade factors that threaten the Texas fatmucket

[[Page 62185]]

include climate change, population fragmentation and isolation, and 
nonnative species.
Climate Change
    It is widely accepted that changes in climate are occurring 
worldwide (International Panel on Climate Change (IPCC) 2007, p. 30). 
Understanding the effects of climate change on the Texas fatmucket is 
important because the disjunct nature of the remaining Texas fatmucket 
populations, coupled with the limited ability of mussels to migrate, 
makes it unlikely that the Texas fatmucket can adjust its range in 
response to changes in climate (Strayer 2008, p. 30). For example, 
changes in temperature and precipitation can increase the likelihood of 
flooding or increase drought duration and intensity, resulting in 
direct effects to freshwater mussels like the Texas fatmucket (Hastie 
et al. 2003, pp. 40-43; Golloday et al. 2004, p. 503). Because the 
range of the Texas fatmucket has been reduced to isolated locations 
with low population numbers in small rivers and streams, the Texas 
fatmucket is vulnerable to climatic changes that could decrease the 
availability of water or produce more frequent scouring flood events. 
Indirect effects of climate change may include declines in host fish 
populations, habitat reduction, and changes in human activity in 
response to climate change (Hastie et al. 2003, pp. 43-44).
    For the next two decades, a warming of about 0.2 [deg]C (0.4 
[deg]F) per decade is projected across the United States (IPCC 2007, p. 
12), and hot extremes, heat waves, and heavy precipitation and flooding 
are expected to increase in frequency (IPCC 2007, p. 18). As with many 
areas of North America, central Texas is projected to experience an 
overall warming trend in the range of 2.5 to 3.3 [deg]C (4.5 to 6 
[deg]F) over the next 50 to 200 years (Mace and Wade 2008, p. 656). 
Even under lower greenhouse gas emission scenarios, recent projections 
forecast a 2.8 [deg]C (5 [deg]F) increase in temperature and a 10 
percent decline in precipitation in central Texas by 2080-2099 (Karl et 
al. 2009, pp. 123-124). Based on our current understanding of climate 
change, air temperatures are expected to rise and precipitation 
patterns are expected to change in areas occupied by the Texas 
fatmucket. Karl et al. (2009, p. 12) also suggests that climate change 
impacts on water resources in the southern Great Plains (including 
central Texas) are expected as rising temperatures and decreasing 
precipitation exacerbate an area already plagued by low rainfall, high 
temperatures, and unsustainable water use practices.
    One preliminary study forecasting the possible hydrological impacts 
of climate change on the annual runoff and its seasonality in the upper 
Colorado River watershed was conducted by CH2M HILL (2008). In this 
initial evaluation, four modeling scenarios (chosen to represent a 
range of possible future climatic conditions) were each run under a 
2050 and 2080 time scenario, producing annual surface water runoff 
estimates at multiple sites with stream gages in the Colorado River 
basin. For the 2050 scenarios, the results from all four climate change 
scenarios predicted significant decreases in annual runoff totals 
compared to historic averages (CH2M HILL 2008, pp. 7-30--7-32). For the 
2080 scenarios, one model predicted increases in annual runoff; the 
other three 2080 scenarios predicted decreases in annual runoff (CH2M 
HILL 2008, pp. 7-30--7-33). The modeling efforts from this study focus 
on annual averages and cannot necessarily account for the seasonal 
variations in flooding events or long periods of drought. However, the 
study demonstrates the potential effects of climate change on surface 
water availability, which is forecasted to result in an overall decline 
in stream flows in the region where the Texas fatmucket occurs.
    In summary, climate change could affect the Texas fatmucket through 
the combined effects of global and regional climate change, along with 
the increased probability of long-term drought. Climate change 
exacerbates threats such as habitat degradation from prolonged periods 
of drought, increased water temperature, and the increased allocation 
of water for municipal, agricultural, and industrial use. As such, 
climate change, in and of itself, may affect the Texas fatmucket, but 
the magnitude and imminence (when the effects occur) of the effects 
remain uncertain. Based upon our review of the best commercial and 
scientific data available, we conclude that the effects of climate 
change in the future will likely exacerbate the current and ongoing 
threats of habitat loss and degradation caused by other factors, as 
discussed above.
Population Fragmentation and Isolation
    All of the remaining populations of the Texas fatmucket are small 
and geographically isolated and thus are susceptible to genetic drift 
(change of gene frequencies in a population over time), inbreeding 
depression, and random or chance changes to the environment, such as 
toxic chemical spills (Watters and Dunn 1995, pp. 257-258) or 
dewatering. Inbreeding depression can result in death, decreased 
fertility, smaller body size, loss of vigor, reduced fitness, and 
various chromosomal abnormalities (Smith 1974, pp. 350). Despite any 
evolutionary adaptations for rarity, habitat loss and degradation 
increase a species' vulnerability to extinction (Noss and Cooperrider 
1994, pp. 58-62). Numerous authors (including Noss and Cooperrider 
1994, pp. 58-62; Thomas 1994, p. 373) have indicated that the 
probability of extinction increases with decreasing habitat 
availability. Although changes in the environment may cause populations 
to fluctuate naturally, small and low-density populations are more 
likely to fluctuate below a minimum viable population (the minimum or 
threshold number of individuals needed in a population to persist in a 
viable state for a given interval) (Gilpin and Soule 1986, pp. 25-33; 
Shaffer 1981, p. 131; Shaffer and Samson 1985, pp. 148-150).
    The Texas fatmucket was widespread throughout much of the Colorado 
and Guadalupe River systems when few natural barriers existed to 
prevent migration (via host species) among suitable habitats. 
Construction of dams, however, likely destroyed many Texas fatmucket 
populations through drastic habitat changes and isolated the remnant 
populations from each other. For fertilization, Texas fatmucket females 
need an upstream male to release sperm; populations with few 
individuals reduce the likelihood that females will be exposed to sperm 
while siphoning. Therefore, recruitment failure is a potential problem 
for many small populations rangewide, a potential condition exacerbated 
by its reduced range and increasingly isolated populations. If downward 
population trends continue, further significant declines in total Texas 
fatmucket population size and consequent reduction in long-term 
survivability may soon become apparent.
    The small, isolated nature of the Texas fatmucket's remaining 
populations also increases the species' vulnerability to stochastic 
(random) natural events. When species are limited to small, isolated 
habitats, as the Texas fatmucket is, they are more likely to become 
extinct due to a local event that negatively effects the population 
(McKinney 1997, p. 497; Minckley and Unmack 2000, pp. 52-53; Shepard 
1993, pp. 354-357). While the populations' small, isolated nature does 
not represent an independent threat to the species, it does 
substantially increase the risk of extirpation from the effects of all 
other threats, including those addressed in

[[Page 62186]]

this analysis, and those that could occur in the future from unknown 
sources.
    Based upon our review of the best commercial and scientific data 
available, we conclude that fragmentation and isolation of small 
remaining populations of the Texas fatmucket exacerbate ongoing threats 
to the species throughout all of its range and are expected to 
continue.
Nonnative Species
    Various nonnative species of aquatic organisms are firmly 
established within the range of the Texas fatmucket and pose a threat 
to the species. Golden algae (Prymnesium parvum) is a microscopic algae 
considered to be one of the most harmful algal species to fish and 
other gill-breathing organisms (Lutz-Carrillo et al. 2010, p. 24). 
Golden algae was first discovered in Texas in 1985 and is presumed to 
have been introduced from western Europe (Lutz-Carrillo et al. 2010, p. 
30). Since its introduction, golden algae has been found in Texas 
rivers and lakes, including two lakes in central Texas (Baylor 
University 2009, p. 1). Under certain environmental conditions, this 
algae can produce toxins that can cause massive fish and mussel kills 
(Barkoh and Fries 2010, p. 1; Lutz-Carrillo et al. 2010, p. 24). 
Evidence shows that golden algae probably caused fish kills in Texas as 
early as the 1960s, but the first documented fish kill due to golden 
algae in inland waters of Texas occurred in 1985 on the Pecos River in 
the Rio Grande basin (TPWD 2002, p. 1). The range of golden algae has 
increased to include portions of the Brazos and Colorado River basins, 
among others, and it has been responsible for killing more than 8 
million fish in the Brazos River since 1981 and more than 2 million 
fish in the Colorado River since 1989 (TPWD 2010a, p. 1). Although 
actual mussel kills in Texas due to golden algae have not been recorded 
in the past, the toxin can kill mussels. Therefore, the elimination of 
host fish and the poisonous nature of the toxin to mussels make future 
golden algae blooms a threat to the Texas fatmucket.
    An additional nonnative species, the zebra mussel (Dreissena 
polymorpha), poses a potential threat to the Texas fatmucket. This 
invasive species has been responsible for the extirpation of freshwater 
mussels in other regions of the United States, including the Higgin's 
eye (Lampsilis higginsii) in Wisconsin and Iowa (Service 2006, pp. 9-
10). Zebra mussels attach in large numbers to the shells of live native 
mussels and are implicated in the loss of entire native mussel beds 
(Ricciardi et al. 1998, p. 615). This fouling impedes locomotion (both 
laterally and vertically), interferes with normal valve movements, 
deforms valve margins, and essentially suffocates and starves the 
native mussels by depleting the surrounding water of oxygen and food 
(Strayer 1999, pp. 77-80). Heavy infestations of zebra mussels on 
native mussels may overly stress the animals by reducing their energy 
reserves. Zebra mussels may also filter the sperm and possibly 
glochidia of native mussels from the water column, thus reducing 
reproductive potential. Habitat for native mussels may also be degraded 
by large deposits of zebra mussel pseudofeces (undigested waste 
material passed out of the incurrent siphon) (Vaughan 1997, p. 11).
    Zebra mussels are not currently found within the range of the Texas 
fatmucket. However, a live adult zebra mussel was first documented in 
Lake Texoma on the Red River (on the north Texas border with Oklahoma) 
in 2009 (TPWD 2009a, p. 1). Since that time, additional zebra mussels 
have been reported from Lake Texoma, where they are now believed to be 
well established (TPWD 2009c, p. 1). Zebra mussels are likely to spread 
to many other Texas reservoirs through accidental human transport 
(Schneider et al. 1998, p. 789). Although zebra mussels tend to 
proliferate in reservoirs or large pools, released zebra mussel larvae, 
called veligers, float downstream and attach to any hard surface 
available, rendering downstream Texas fatmucket populations extremely 
vulnerable to attachment and fouling. Because zebra mussels are so 
easily introduced to new locations, the potential for zebra mussels to 
continue to expand in Texas and invade the range of the Texas fatmucket 
is high. If this occurs, the Texas fatmucket is vulnerable to zebra 
mussel attachment and subsequent deprivation of oxygen, food, and 
mobility.
    A molluscivore (mollusk eater), the black carp (Mylopharyngodon 
piceus) is a potential threat to the Texas fatmucket. The species has 
been commonly used by aquaculturists to control snails or for research 
in fish production in several States, including Texas (72 FR 59019, 
October 18, 2007). Black carp can reach more than 1.3 m (4 ft) in 
length and 150 pounds (68 kilograms (kg)) (Nico and Williams 1996, p. 
6). Foraging rates for a 4-year-old fish average 3 to 4 pounds (1.4 
to1.8 kg) a day, indicating that a single individual could consume 10 
tons (9,072 kg) of native mollusks over its lifetime (Mississippi 
Interstate Cooperative Resource Association (MICRA) 2005, p. 1). Black 
carp can escape from aquaculture facilities. For example, in 1994 30 
black carp escaped from an aquaculture facility in Missouri during a 
flood. Other escapes into the wild by non-sterile carp are likely to 
occur. Because of the high risk to freshwater mussels and other native 
mollusks, the Service recently listed black carp as an injurious 
species under the Lacey Act (72 FR 59019, October 18, 2007), which 
prevents importations and interstate transfer of this harmful species, 
but does not prevent its release into the wild once it is in the State. 
If the black carp were to escape within the range of the Texas 
fatmucket, it would likely negatively affect native mussels, including 
the Texas fatmucket.
    Based upon our review of the best commercial and scientific data 
available, we conclude that golden algae is an ongoing threat to the 
Texas fatmucket, and other nonnative species, such as zebra mussels and 
black carp, are a potential future threat to the Texas fatmucket that 
is likely to increase as these exotic species expand their occupancy 
within the range of the Texas fatmucket.
Summary of Factor E
    The effects of climate change, while difficult to quantify at this 
time, are likely to exacerbate the current and ongoing threat of 
habitat loss caused by other factors, and the small sizes and 
fragmented nature of the remaining populations render them more 
vulnerable to extirpation. In addition, nonnative species, such as 
golden algae, currently threaten the Texas fatmucket, and the potential 
introduction of zebra mussels and black carp are potential future 
threats. Based upon our review of the best commercial and scientific 
data available, we conclude that other natural or manmade factors are 
immediate threats of moderate magnitude to the Texas fatmucket.

Finding for Texas Fatmucket

    As required by the Act, we considered the five factors in assessing 
whether Texas fatmucket is threatened or endangered throughout all of 
its range. We examined the best scientific and commercial information 
available regarding the past, present, and future threats faced by the 
Texas fatmucket. We reviewed the petition, information available in our 
files, and other available published and unpublished information, and 
we consulted with recognized Texas fatmucket experts and other Federal 
and State agencies.
    This status review identified threats to the Texas fatmucket 
attributable to Factors A, D, and E. The primary threat to the species 
is from habitat destruction and modification (Factor A) from

[[Page 62187]]

impoundments, which scour riverbeds, thereby removing mussel habitat, 
decrease water quality, modify stream flows, and prevent fish host 
migration and distribution of freshwater mussels, as well as 
sedimentation, dewatering, sand and gravel mining, and chemical 
contaminants. Additionally, most of these threats may be exacerbated by 
the current and projected effects of climate change (discussed in 
Factor E). Threats to the Texas fatmucket and its habitat are not being 
adequately addressed through existing regulatory mechanisms (Factor D). 
Because of the limited distribution of this endemic species and its 
lack of mobility, these threats are likely to result in the extinction 
of the Texas fatmucket in the foreseeable future.
    On the basis of the best scientific and commercial information 
available, we find that the petitioned action to list the Texas 
fatmucket under the Act is warranted. We will make a determination on 
the status of the species as threatened or endangered when we complete 
a proposed listing determination. When we complete a proposed listing 
determination, we will examine whether the species may be endangered or 
threatened throughout all of its range or whether the species may be 
endangered or threatened in a significant portion of its range. 
However, as explained in more detail below, an immediate proposal of a 
regulation implementing this action is precluded by higher priority 
listing actions, and progress is being made to add or remove other 
qualified species from the Lists of Endangered and Threatened Wildlife 
and Plants.
    We reviewed the available information to determine if the existing 
and foreseeable threats render the Texas fatmucket at risk of 
extinction now such that issuing an emergency regulation temporarily 
listing the species under section 4(b)(7) of the Act is warranted. We 
determined that issuing an emergency regulation temporarily listing the 
species is not warranted for the Texas fatmucket at this time, because 
we have not identified a threat or activity that poses a significant 
risk, such that losses to the species during the normal listing process 
would endanger the continued existence of the entire species. However, 
if at any time we determine that issuing an emergency regulation 
temporarily listing Texas fatmucket is warranted, we will initiate this 
action at that time.
Listing Priority Number for Texas Fatmucket
    The Service adopted guidelines on September 21, 1983 (48 FR 43098), 
to establish a rational system for utilizing available resources for 
the highest priority species when adding species to the Lists of 
Endangered and Threatened Wildlife and Plants or reclassifying species 
listed as threatened to endangered status. These guidelines, titled 
``Endangered and Threatened Species Listing and Recovery Priority 
Guidelines,'' address the immediacy and magnitude of threats, and the 
level of taxonomic distinctiveness by assigning priority in descending 
order to monotypic genera (genus with one species), full species, and 
subspecies (or equivalently, distinct population segments of 
vertebrates).
    As a result of our analysis of the best available scientific and 
commercial information, we have assigned the Texas fatmucket a Listing 
Priority Number (LPN) of 2, based on our finding that the species faces 
threats that are of high magnitude and are imminent. These threats 
include habitat loss and degradation from impoundments, sedimentation, 
sand and gravel mining, and chemical contaminants; other natural or 
manmade factors such as climate change, small, isolated populations, 
and nonnative species; and the fact that the threats to the species are 
not being adequately addressed by existing regulatory mechanisms. Our 
rationale for assigning the Texas fatmucket an LPN of 2 is outlined 
below.
    Under the Service's guidelines, the magnitude of threat is the 
first criterion we look at when establishing a listing priority. The 
guidance indicates that species with the highest magnitude of threat 
are those species facing the greatest threats to their continued 
existence. These species receive the highest listing priority. We 
consider the threats that the Texas fatmucket faces to be high in 
magnitude. Habitat loss and degradation from impoundments, 
sedimentation, sand and gravel mining, and chemical contaminants are 
widespread throughout the range of the Texas fatmucket and profoundly 
affect its survival and recruitment. Remaining populations are small, 
isolated, and highly vulnerable to stochastic events.
    Under our LPN guidelines, the second criterion we consider in 
assigning a listing priority is the immediacy of threats. This 
criterion is intended to ensure that the species facing actual, 
identifiable threats are given priority over those for which threats 
are only potential or that are intrinsically vulnerable but are not 
known to be presently facing such threats. We consider the threats to 
the Texas fatmucket as described under Factors A, D, and E in the Five-
Factor Evaluation for Texas Fatmucket section to be imminent because 
these threats have affected the species in the past, are ongoing, and 
will continue in the foreseeable future. Habitat loss and destruction 
have already occurred and will continue as the human population 
continues to grow in central Texas. Texas fatmucket populations may 
already be below the minimum viable population requirement, which would 
cause a reduction in the number of populations and an increase in the 
species' vulnerability to extinction. These threats are exacerbated by 
climate change, which will increase the frequency and magnitude of 
droughts. Therefore, we consider these threats to be imminent.
    The third criterion in our Listing Priority Number guidance is 
intended to devote resources to those species representing highly 
distinctive or isolated gene pools as reflected by taxonomy. The Texas 
fatmucket is a valid taxon at the species level and, therefore, 
receives a higher priority than subspecies, but a lower priority than 
species in a monotypic genus. Therefore, we assigned Texas fatmucket an 
LPN of 2.
    We will continue to monitor the threats to the Texas fatmucket and 
the species' status on an annual basis, and should the magnitude or 
imminence of the threats change, we will revisit our assessment of the 
LPN.
    While we conclude that listing the Texas fatmucket is warranted, an 
immediate proposal to list this species is precluded by other higher 
priority listings, which we address in the Preclusion and Expeditious 
Progress section below. Because we have assigned the Texas fatmucket an 
LPN of 2, work on a proposed listing determination for the species is 
precluded by work on higher priority listing actions with absolute 
statutory, court-ordered, or court-approved deadlines and final listing 
determinations for those species that were proposed for listing with 
funds from Fiscal Year (FY) 2011. This work includes all the actions 
listed in the tables below under Preclusion and Expeditious Progress.

Five-Factor Evaluation for Golden Orb

    Information pertaining to the golden orb in relation to the five 
factors provided in section 4(a)(1) of the Act is discussed below.
    Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range.
    As discussed above, the decline of mussels in Texas and across the 
United States is primarily the result of habitat

[[Page 62188]]

loss and degradation. Chief among the causes of decline of the golden 
orb in Texas are the effects of impoundments, dewatering, 
sedimentation, sand and gravel mining, chemical contaminants, and off-
road vehicle use. These threats are discussed below.
Impoundments
    For general information on the effects of impoundments on 
freshwater mussels, please refer to ``Impoundments'' under Factor A in 
Five-Factor Evaluation for Texas Fatmucket. Golden orb occur in one 
impoundment, Lake Corpus Christi, indicating that inundation may not be 
as detrimental to this species as it is to other, more flow-dependent 
mussel species. However, dams continue to fragment golden orb 
populations. There are 29 reservoirs, each with a storage capacity of 
3,000 acre-feet or more, within the Guadalupe River basin and 34 within 
the San Antonio River basin, in addition to many other smaller 
reservoirs in these basins (Exelon 2010, p. 2.3-4). Three large 
reservoirs exist within the Nueces River basin.
    Historical records showed that the golden orb once occurred in the 
Guadalupe River in Comal County before the Canyon Reservoir was 
constructed in 1964 (Randklev et al. 2010c, p. 4). No live or recently 
dead golden orb have been found in this reach since the reservoir was 
completed (Burlakova and Karatayev 2010a, pp. 14-15), and we presume 
the species is extirpated from this reach because of the effects of the 
reservoir. Surveys of the reservoirs in the Guadalupe River system have 
been ongoing since at least 1992, and no evidence of live or dead 
golden orb has been found in any of the reservoirs (Howells 1994, pp. 
1-20; 1995, pp. 1-50; 1996, pp. 1-45; 1997a, pp. 1-58; 1998, pp. 1-30; 
1999, pp. 1-34; 2000a, pp. 1-56; 2001, pp. 1-50; 2002a, pp. 1-28; 2003, 
pp. 1-42; 2004, pp. 1-48; 2005, pp. 1-23; 2006, pp. 1-106; Karatayev 
and Burlakova 2008, pp. 1-47; Burlakova and Karatayev 2010a, pp. 1-30; 
2011, pp. 1-8).
    For species such as golden orb that may be able to survive the 
initial inundation of reservoirs, conditions within the reservoir are 
likely to become uninhabitable. The deep water in reservoirs is very 
cold and often devoid of oxygen and necessary nutrients (Watters 2000, 
p. 264). Cold water (less than 11 [deg]C (52 [deg]F)) has been shown to 
stunt mussel growth (Hanson et al. 1988, p. 352). Because mussel 
reproduction is temperature dependent (Watters and O'Dee 1999, p. 455), 
it is likely that individuals living in the constantly cold hypolimnion 
in these channels may never reproduce, or reproduce less frequently 
(Watters 2000, p. 264). Any golden orb that survived the initial 
inundation may have been unable to reproduce, eventually eliminating 
the species from large areas of the reservoir. The same would be true 
for mussels living in cold-water discharges downstream of large 
impoundments (Watters 2000, p. 264).
    Dam construction also fragments the range of golden orb, leaving 
remaining habitats and populations isolated by the structures, as well 
as by extensive areas of deep, uninhabitable, impounded waters. These 
isolated populations are unable to naturally recolonize suitable 
habitat that may be impacted by temporary but devastating events, such 
as severe drought, chemical spills, or unauthorized discharges. Dams 
impound river habitats throughout almost the entire range of the 
species. These impoundments have left short and isolated patches of 
remnant habitat, typically in between impounded reaches, such as the 
golden orb population on the Guadalupe River within about one mile (1.6 
km) downstream of Lake Wood. This population is subject to dramatic 
flow fluctuations from the hydroelectric facility associated with the 
dam (Howells 2010a, p. 4), which can leave individuals stranded when 
water levels are quickly lowered or wash individuals downstream when 
flow is increased.
    The widespread construction of dams throughout the range of golden 
orb has significantly altered stream habitat both upstream and 
downstream of the dams by changing fish assemblages, temperature, 
dissolved oxygen, and substrate. The effects of dams on the golden orb 
are expected to be ongoing decades after construction and are presumed 
to be continuing today. Because of this loss of habitat and its 
widespread effects on the populations, we conclude that the effects of 
dams are a threat to the golden orb.
Sedimentation
    For general information on the effects of sedimentation on 
freshwater mussels like the golden orb, please refer to 
``Sedimentation'' under Factor A in Five-Factor Evaluation for Texas 
Fatmucket.
    As with other freshwater mussel species, the golden orb is affected 
by excessive sedimentation in streams. Even in 1959, the Guadalupe 
River was noted as having high sedimentation rates from agricultural 
activities (Soil Conservation Service 1959, p. 59). Turbidity has also 
been recorded as high in the Guadalupe River near Victoria (Exelon 
2010, p. 2.3-186), indicating a large amount of suspended sediment 
where a small golden orb population was recently found. Sedimentation 
can occur from agricultural activities, sand and gravel mining, urban 
runoff, and construction activities, among other sources.
    One example of a proposed project that could lead to localized 
increases in sedimentation within the range of the golden orb is the 
LCRA TSC. This project proposes to construct two new, 345-kV electric 
transmission line facilities between Tom Green (in the Colorado River 
basin near San Angelo) and Kendall Counties (in the Guadalupe River 
basin north of San Antonio) to provide electrical power to accommodate 
increased human populations (Clary 2010, p. 1). One of the proposed 
transmission lines would cross the upper Guadalupe River in Kerr 
County, which contains a small population of golden orb. The proposed 
project could negatively affect golden orb habitat by clearing land 
within the riparian zone and may increase sediment runoff into the 
Guadalupe River (Clary 2010, p. 7). Similar activities to accommodate 
Texas population growth are expected to be undertaken across the 
species' range and will likely lead to additional sources of sediment 
in the streams inhabited by the golden orb.
    Streams occupied by golden orb are subject to increasing levels of 
sedimentation from agriculture, urbanization, and sand and gravel 
mining. Agriculture is a common land use in the Guadalupe and San 
Antonio River basins. Sedimentation may become an increasing threat to 
the golden orb in the Guadalupe River basin as the San Antonio metro 
area continues to expand. Activities associated with urbanization, such 
as road construction, increased impervious surfaces, and road 
construction can be detrimental to stream habitats (Couch and Hamilton 
2002, p. 1), and the City of San Antonio, the second largest city in 
Texas, continues to grow (City of San Antonio 2010, p. 5). 
Sedimentation from agriculture, urbanization, and sand and gravel 
mining is widespread in the range of the golden orb will continue to 
threaten the species.
Dewatering
    River dewatering can occur in several ways: anthropogenic 
activities such as surface water diversions and groundwater pumping, 
and natural events, such as drought, which can result in mussels 
stranded in previously wetted areas. This is a particular concern 
within and below reservoirs, whose water levels are managed for

[[Page 62189]]

various purposes that can cause water levels in the reservoir or 
downstream to rise or fall in very short periods of time, such as when 
hydropower facilities release water during peak energy demand periods. 
For example, Lake Corpus Christi reservoir has experienced several 
drawdowns of lake levels to reduce salinity levels in the reservoir, 
such as in 1996 and 2006. Golden orb have been stranded above the water 
line during both drawdowns, killing the exposed mussels (Howells 2006, 
pp. 75-76). Rivers can also be dewatered to facilitate construction 
activities, such as in the upper Guadalupe River in Kerr County, which 
was dewatered in 1998 for bridge construction, which exposed and killed 
golden orb (Howells 1999, pp. 18-19).
    Drought can also severely impact golden orb populations. Central 
Texas, including the Guadalupe River basin, experienced a major drought 
in the late 1970s (Lewis and Oliveria 1979, p. 243). Near record dry 
conditions in 2008 followed by a pattern of below-normal rainfall 
during the winter and spring of 2009 led to one of the worst droughts 
in recorded history for most of central Texas, including the range of 
the golden orb (Nielsen-Gammon and McRoberts 2009, p. 2). This 
drought's severity was exacerbated by abnormally high air temperatures, 
a likely effect of climate change, which has already increased average 
air temperatures in Texas by at least 1 [deg]C (1.8 [deg]F) (Nielsen-
Gammon and McRoberts 2009, p. 22). The Guadalupe River in Kerr County 
experienced minimal to no flow during periods of the 2009 drought (USGS 
2011b, p. 2), which may have negatively affected this golden orb 
population. Central Texas is currently experiencing another extreme 
drought, with rainfall between October 2010 and July 2011 being the 
lowest on record during those months (LCRA 2011c, p. 1); the effects of 
this drought are being observed but are not yet fully known.
    We do not know the extent of the impacts of stream dewatering on 
the golden orb; however, because several populations are small and 
isolated, the loss of numerous individuals at a site can have dramatic 
consequences to the population. Hydropower facilities, construction, 
and drought are occurring throughout the range of the golden orb; 
therefore, the effects of dewatering are ongoing and unlikely to 
decrease, resulting in significant threats to the golden orb.
Sand and Gravel Mining
    For general information on the effects of sand and gravel mining on 
freshwater mussels, please refer to ``Sand and Gravel Mining'' under 
Factor A in Five-Factor Evaluation for Texas Fatmucket.
    In 1995, the reach of the Guadalupe River near Victoria, which 
contains a golden orb population, was described as having numerous 
current and abandoned sand and gravel mining areas (USACE 1995, p. 7). 
Currently, TPWD has permitted one sand mining activity within the 
existing range of golden orb, in the Guadalupe River basin in Comal 
County (TPWD 2009b, p. 1); golden orb populations occur upstream and 
downstream of this area in the Guadalupe River. The permit allows for 
the repeated removal of sand and gravel at various locations within the 
stream.
    Headcuts from sand and gravel mining operations have been 
documented in the San Antonio River basin in Karnes County from as 
early as 1967, with downstream channels having steep, eroded banks 
(Kennon et al. 1967, p. 22). The golden orb has not been documented 
from this area since 1996, and only an old, eroded shell was collected 
at that time (Howells 1997a, pp. 41-42).
    The golden orb populations in the Guadalupe River may be currently 
threatened by sand and gravel mining. These activities occur over a 
long period of time, destabilizing habitat both upstream and 
downstream, which decreases the likelihood of recolonization after the 
activity has been completed. Therefore, the effects of sand and gravel 
mining are an ongoing threat to the golden orb.
Chemical Contaminants
    For general information on the effects of chemical contaminants on 
freshwater mussels, please refer to ``Chemical Contaminants'' under 
Factor A in Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussel species, the golden orb is also 
threatened by chemical contaminants. TCEQ water quality standards for 
2010 indicated the majority of the assessed water bodies within the 
golden orb's historical and current range did not meet surface water 
quality standards and were classified as impaired water bodies (Nueces 
River Authority 2010, pp. 1-37; Texas Clean Rivers Program 2010b, p. 
13). These water bodies were impaired with dissolved solids, nitrates, 
bacteria, low dissolved oxygen, sulfates, phosphates, chloride, 
chlorophyll-a, and low pH associated with agricultural, urban, 
municipal, and industrial runoff. Of these, nitrates and low dissolved 
oxygen pose the greatest threat to the golden orb. Additionally, 
several streams within the range of the golden orb have been listed as 
impaired due to high ammonia concentrations, including Elm Creek in the 
Guadalupe River basin (TCEQ 2010a, p. 294). High copper concentrations 
have been recorded in the lower Guadalupe and San Antonio Rivers (Lee 
and Schultz 1994, p. 8), and mercury has been documented throughout the 
Guadalupe and San Antonio Rivers, with particularly high concentrations 
found in fish tissues from the upper reaches of both rivers (Lee and 
Schultz 1994, p. 8). Row crop agriculture and wastewater discharges are 
prominant within the range of the golden orb. These activities result 
in chronic contamination from agricultural pesticides and emerging 
contaminants of rivers inhabited by the species and are a threat to 
golden orb.
    Numerous spills of potential contaminant materials have occurred 
within the range of the golden orb. These can occur from on site 
accidents (tank, pipeline spills) or from tanker truck accidents within 
watersheds occupied by golden orb. For example, 100,000 gallons of 
sewage spilled into the San Antonio River near the City of San Antonio 
when a pipeline collapsed in October 2010 (San Antonio Water System 
2010, p. 1). The largest known golden orb population occurs downstream 
of this location. Raw sewage contains very high ammonia levels, which 
is toxic to freshwater mussels, as well as other pollutants. 
Additionally, 300 gallons of diesel fuel spilled into the San Antonio 
River near the same location in May 2011 (Serna 2011, p. 1). Another 
sewage spill occurred in April 2011 in Quinlan Creek, a tributary to 
the Guadalupe River near the Kerr County population of golden orb 
(MacCormack 2011, p. 1). The actual effects on the golden orb of spills 
such as these recent examples are unknown, but there are likely to be 
negative consequences.
    Because of the risk of spills as well as chronic contamination, 
chemical contaminants, such as oil, ammonia, copper, mercury, 
nutrients, pesticides, and other compounds are currently a threat to 
the golden orb. The species is vulnerable to acute contamination from 
spills as well as chronic contaminant exposure, which is occurring 
rangewide.
Summary of Factor A
    The reduction in numbers and range of the golden orb is primarily 
the result of the long-lasting effects of habitat alterations such as 
the effects of impoundments, sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. Impoundments occur throughout the 
range of the species and have far-reaching effects both up- and

[[Page 62190]]

downstream. Both the Colorado and Guadalupe River systems experience a 
large amount of sedimentation from agriculture, instream mining, and 
urban development. Sand and gravel mining affects golden orb habitat by 
causing headcutting upstream, increasing sedimentation concentrations 
in the water downstream, and causing channel instability downstream. 
Chemical contaminants have been documented throughout the range of the 
species and may represent a significant threat to the golden orb. 
However, the large populations in the middle and lower Guadalupe River, 
lower San Antonio River, and San Marcos River indicate that some golden 
orb populations are not currently as vulnerable to habitat loss as 
others. Based upon our review of the best commercial and scientific 
data available, we conclude that the present or threatened destruction, 
modification, or curtailment of its habitat or range is an immediate 
threat of moderate magnitude to golden orb populations rangewide.
    Factor B. Overutilization for Commercial, Recreational, Scientific, 
or Educational Purposes.
    The golden orb is not a commercially valuable species and has never 
been harvested in Texas as a commercial mussel species (Howells 2010a, 
p. 12). Some scientific collecting occurs but is not likely to be a 
significant threat to the species because it occurs only rarely. 
However, handing mussels can disturb gravid females and result in 
glochidial loss and subsequent reproductive failure (Waller et. al 
1995, p. 205). Additionally, handling has also been shown to reduce 
shell growth across mussel species, including several species of 
Lampsilis (Haag and Commens-Carson 2008, pp. 505-506). Repeated 
handling by researchers may adversely affect golden orb individuals, 
but these activities are occurring rarely and are not likely to 
threaten populations. Handling for scientific purposes contributes to 
the long-term conservation of the species.
    We do not have any evidence of risks to the golden orb from 
overutilization for commercial, recreational, scientific, or 
educational purposes, and we have no reason to believe this factor will 
become a threat to the species in the future. Based upon the best 
scientific and commercial information available, we conclude that 
overutilization of the golden orb for commercial, recreational, 
scientific, or educational purposes does not pose a significant threat 
to the species rangewide.
    Factor C. Disease and Predation.
Disease
    Little is known about disease in freshwater mussels. However, 
disease is believed to be a contributing factor in documented mussel 
die-offs in other parts of the United States (Neves 1987, pp. 11-12). 
Diseases have not been documented or observed during any studies of 
golden orb.
Predation
    Raccoons will prey on freshwater mussels stranded by low waters or 
deposited in shallow water or on bars following flooding or low water 
periods (Howells 2010c, p. 12). Predation of golden orb by raccoons may 
be occurring occasionally but there is no indication it is a 
significant threat to the status of the species.
    Some species of fish feed on mussels, such as common carp, 
freshwater drum, and redear sunfish, all of which are common throughout 
the range of golden orb (Hubbs et al. 2008, pp. 19, 45, 53). Common 
species of flatworms are voracious predators of newly metamorphosed 
juvenile mussels of many species (Zimmerman et al. 2003, p. 30). 
Predation is a normal factor influencing population dynamics of a 
healthy mussel population; however, predation may amplify declines in 
small populations primarily caused by other factors.
Summary of Factor C
    Disease in freshwater mussels is poorly known, and we do not have 
any information indicating it is a threat to the golden orb. 
Additionally, predation is a natural ecological interaction and we have 
no information indicating the extent of any predation is a threat to 
populations of golden orb. Based upon the best scientific and 
commercial information available, we conclude that disease or predation 
is not a threat to the golden orb.
    Factor D. The Inadequacy of Existing Regulatory Mechanisms.
    Existing regulatory mechanisms that could have an effect on threats 
to the golden orb include State and Federal laws such as Texas 
Threatened and Endangered Species regulations and freshwater mussel 
sanctuaries, State and Federal sand and gravel mining regulations, and 
regulation of point and non-point source pollution. For more 
information on the effects of these regulations on the threats to 
freshwater mussels in central Texas, please refer to Factor D under 
Five-Factor Evaluation for Texas Fatmucket.
Summary of Factor D
    Despite State and Federal laws protecting the species and water 
quality, the golden orb continues to decline due to the effects of 
habitat destruction, poor water quality, contaminants, and other 
factors. The regulatory measures described above have been insufficient 
to significantly reduce or remove the threats to the golden orb. Based 
upon our review of the best commercial and scientific data available, 
we conclude that the lack of existing regulatory mechanisms is an 
immediate threat of moderate magnitude to the golden orb.
    Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence.
    Natural and manmade factors that threaten the golden orb include 
climate change, population fragmentation and isolation, and nonnative 
species.
Climate Change
    For more general information on the effects of climate change on 
freshwater mussels in central Texas, please refer to ``Climate Change'' 
under Factor E in Five-Factor Evaluation for Texas Fatmucket. Because 
the range of the golden orb has been reduced to isolated locations, 
many with low population numbers in small rivers and streams, the 
golden orb is vulnerable to climatic changes that could decrease the 
availability of water.
    The disjunct nature of the remaining golden orb populations, 
coupled with the limited ability of mussels to migrate, makes it 
unlikely that golden orb can adjust their range in response to changes 
in climate (Strayer 2008, p. 30). Climate change could affect the 
golden orb through the combined effects of global and regional climate 
change, along with the increased probability of long-term drought. 
Climate change exacerbates threats such as habitat degradation from 
prolonged periods of drought, increased water temperature, and the 
increased allocation of water for municipal, agricultural, and 
industrial uses. Climate change may be a significant stressor that 
exacerbates existing threats by increasing the likelihood of prolonged 
drought. As such, climate change, in and of itself, may affect the 
golden orb, but the magnitude and imminence of the effects remain 
uncertain. Based upon our review of the best commercial and scientific 
data available, we conclude that the effects of climate change in the 
future will likely exacerbate the current and ongoing threats of 
habitat loss and degradation caused by other factors, as discussed 
above.
Population Fragmentation and Isolation
    For general information on the effects of population fragmentation 
and isolation on freshwater mussels in

[[Page 62191]]

central Texas, please refer to ``Population Fragmentation and 
Isolation'' under Factor E in Five-Factor Evaluation for Texas 
Fatmucket. As with many freshwater mussels, several of the remaining 
populations of the golden orb are small and geographically isolated and 
thus are more susceptible to genetic drift, inbreeding depression, and 
random or chance changes to the environment, such as toxic chemical 
spills (Watters and Dunn 1995, pp. 257-258) or dewatering. 
Historically, the golden orb was widespread throughout much of the 
Guadalupe River system and in portions of the Nueces-Frio River system 
when few natural barriers existed to prevent migration (via host 
species) among suitable habitats. The extensive impoundment of the 
Nueces, Guadalupe, and San Antonio River basins by the construction of 
dams has fragmented the few remaining golden orb populations throughout 
these river systems.
    Small golden orb populations, including those in Lake Corpus 
Christi Reservoir, the upper Guadalupe River in Kerr County, and the 
San Antonio River in Victoria County, may now be below the minimum 
population size required to maintain population viability into the 
future, since they are less likely to be able to recover through 
recruitment from events that reduce but do not extirpate populations. 
Additionally, these small populations are more vulnerable to 
extirpation from stochastic events, as the lack of connectivity among 
populations does not permit nearby populations to recolonize areas 
affected by intense droughts, toxic spills, or other isolated events 
that result in significant mussel dieoffs. While the small, isolated 
populations do not represent an independent threat to the species, the 
situation does substantially increase the risk of extirpation from the 
effects of all other threats, including those addressed in this 
analysis, and those that could occur in the future from unknown 
sources.
    Based upon our review of the best commercial and scientific data 
available, we conclude that fragmentation and isolation of small 
remaining populations of the golden orb are occurring and are ongoing 
threats to the species throughout all of its range.
Nonnative Species
    For general information on the effects of nonnative species on 
freshwater mussels of central Texas, please refer to ``Nonnative 
Species'' under Factor E in Five-Factor Evaluation for Texas Fatmucket. 
Various nonnative aquatic species pose a threat to the golden orb, 
including golden algae, zebra mussels, and black carp. Zebra mussels 
and black carp are not currently found within the range of golden orb, 
but they are likely to be introduced within its range in the future.
    Based upon our review of the best commercial and scientific data 
available, we conclude that golden algae is an ongoing threat to the 
golden orb, and other nonnative species, such as zebra mussels and 
black carp, are a potential threat to the golden orb that is likely to 
increase as these exotic species expand their occupancy to include the 
range of the golden orb.
Summary of Factor E
    The effects of climate change, while difficult to quantify at this 
time, are likely to exacerbate the current and ongoing threat of 
habitat loss caused by other factors, and the small sizes and 
fragmented nature of the remaining populations render them more 
vulnerable to extirpation. In addition, nonnative species, such as 
golden algae, currently threaten the golden orb, and the potential 
introduction of zebra mussels and black carp are potential future 
threats. Based upon our review of the best commercial and scientific 
data available, we conclude that other natural or manmade factors are 
immediate threats of moderate magnitude to the golden orb.
Finding for Golden Orb
    As required by the Act, we considered the five factors in assessing 
whether the golden orb is threatened or endangered throughout all of 
its range. We examined the best scientific and commercial information 
available regarding the past, present, and future threats faced by the 
golden orb. We reviewed the petition, information available in our 
files, and other available published and unpublished information, and 
we consulted with recognized golden orb experts and other Federal and 
State agencies.
    This status review identifies threats to the golden orb 
attributable to Factors A, D, and E. The primary threat to the species 
is from habitat destruction and modification (Factor A) from 
impoundments, which scour riverbeds, thereby removing mussel habitat, 
decrease water quality, modify stream flows, and restrict fish host 
migration and distribution of freshwater mussels. Additional threats 
under Factor A include sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. Also, most of these threats may be 
exacerbated by the current and projected effects of climate change, 
population fragmentation and isolation, and the anticipated threat of 
nonnative species (discussed under Factor E). Threats to the golden orb 
are not being adequately addressed through existing regulatory 
mechanisms (Factor D). Because of the limited distribution of this 
endemic species and its lack of mobility, these threats are likely to 
lead to the extinction of the golden orb in the foreseeable future.
    On the basis of the best scientific and commercial information 
available, we find that the petitioned action to list the golden orb 
under the Act is warranted. We will make a determination on the status 
of the species as threatened or endangered when we complete a proposed 
listing determination. When we complete a proposed listing 
determination, we will examine whether the species may be endangered or 
threatened throughout all of its range or whether the species may be 
endangered or threatened in a significant portion of its range. 
However, as explained in more detail below, an immediate proposal of a 
regulation implementing this action is precluded by higher priority 
listing actions, and progress is being made to add or remove qualified 
species from the Lists of Endangered and Threatened Wildlife and 
Plants.
    We reviewed the available information to determine if the existing 
and foreseeable threats render the golden orb at risk of extinction now 
such that issuing an emergency regulation temporarily listing the 
species under section 4(b)(7) of the Act is warranted. We determined 
that issuing an emergency regulation temporarily listing the species is 
not warranted for the golden orb at this time, because we have not 
identified a threat or activity that poses a significant risk, such 
that losses to the species during the normal listing process would 
endanger the continued existence of the entire species. However, if at 
any time we determine that issuing an emergency regulation temporarily 
listing the golden orb is warranted, we will initiate this action at 
that time.
Listing Priority Number for Golden Orb
    The Service adopted guidelines on September 21, 1983 (48 FR 43098), 
to establish a rational system for utilizing available resources for 
the highest priority species when adding species to the Lists of 
Endangered and Threatened Wildlife and Plants or reclassifying species 
listed as threatened to endangered status. These guidelines, titled 
``Endangered and Threatened Species Listing and Recovery Priority 
Guidelines'' address the immediacy and magnitude of threats, and the 
level of taxonomic distinctiveness by assigning

[[Page 62192]]

priority in descending order to monotypic genera (genus with one 
species), full species, and subspecies (or equivalently, distinct 
population segments of vertebrates).
    As a result of our analysis of the best available scientific and 
commercial information, we have assigned the golden orb a Listing 
Priority Number (LPN) of 8, based on our finding that the species faces 
threats that are of moderate magnitude and are imminent. These threats 
include habitat loss and degradation from impoundments, sedimentation, 
sand and gravel mining, and chemical contaminants; other natural or 
manmade factors such as climate change, small, isolated populations, 
and nonnative species; and the fact that the threats to the species are 
not being adequately addressed by existing regulatory mechanisms. Our 
rationale for assigning the golden orb an LPN of 8 is outlined below.
    Under the Service's guidelines, the magnitude of threat is the 
first criterion we look at when establishing a listing priority. The 
guidance indicates that species with the highest magnitude of threat 
are those species facing the greatest threats to their continued 
existence. These species receive the highest listing priority. We 
consider the threats that the golden orb faces to be moderate in 
magnitude. Habitat loss and degradation from impoundments, 
sedimentation, sand and gravel mining, and chemical contaminants are 
widespread throughout the range of the golden orb, but several large 
populations remain, including one that was recently discovered, 
suggesting that the threats are not high in magnitude.
    Under our LPN guidelines, the second criterion we consider in 
assigning a listing priority is the immediacy of threats. This 
criterion is intended to ensure that the species facing actual, 
identifiable threats are given priority over those for which threats 
are only potential or that are intrinsically vulnerable but are not 
known to be presently facing such threats. We consider the threats to 
the golden orb as described in Factors A, D, and E under the Five-
Factor Evaluation for Golden Orb to be imminent because these threats 
are ongoing and will continue in the foreseeable future. Habitat loss 
and destruction has already occurred and will continue as the human 
population continues to grow in central Texas. Several golden orb 
populations may already be below the minimum viable population 
requirement, which would cause a reduction in the number of populations 
and an increase in the species' vulnerability to extinction. These 
threats are exacerbated by climate change, which will increase the 
frequency and magnitude of droughts. Therefore, we consider these 
threats to be imminent.
    The third criterion in our Listing Priority Number guidance is 
intended to devote resources to those species representing highly 
distinctive or isolated gene pools as reflected by taxonomy. The golden 
orb is a valid taxon at the species level and, therefore, receives a 
higher priority than subspecies, but a lower priority than species in a 
monotypic genus. Therefore, we assigned golden orb an LPN of 8.
    We will continue to monitor the threats to the golden orb and the 
species' status on an annual basis, and should the magnitude or 
imminence of the threats change, we will revisit our assessment of the 
LPN.
    While we conclude that listing the golden orb is warranted, an 
immediate proposal to list this species is precluded by other higher 
priority listings, which we address in the Preclusion and Expeditious 
Progress section below. Because we have assigned the golden orb an LPN 
of 8, work on a proposed listing determination for the species is 
precluded by work on higher priority listing actions with absolute 
statutory, court-ordered, or court-approved deadlines and final listing 
determinations for those species that were proposed for listing with 
funds from Fiscal Year (FY) 2011. This work includes all the actions 
listed in the tables below under Preclusion and Expeditious Progress.

Five-Factor Evaluation for Smooth Pimpleback

    Information pertaining to the smooth pimpleback in relation to the 
five factors provided in section 4(a)(1) of the Act is discussed below.
    Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range.
    As discussed above, the decline of mussels in Texas and across the 
United States is primarily the result of habitat loss and degradation. 
Chief among the causes of decline of the smooth pimpleback in Texas are 
the effects of impoundments, sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants.
Impoundments
    For general information on the effects of impoundments on 
freshwater mussels, please refer to ``Impoundments'' under Factor A in 
Five-Factor Evaluation for Texas Fatmucket. As with golden orb, smooth 
pimpleback are able to tolerate some impoundment conditions. Smooth 
pimpleback have been known to occur in three mainstem reservoirs on the 
Colorado River, although all but one population is likely extirpated 
(Howells 1997a, pp. 32-33; 1999, p. 16; 2005, p. 8; 2006, p. 67). Dams 
continue to fragment smooth pimpleback populations, and the downstream 
effects of dams are detrimental to smooth pimpleback habitat. There are 
74 major reservoirs and numerous smaller impoundments within the 
historical and current range of the smooth pimpleback. Thirty-one of 
the 74 major reservoirs are located within the Colorado River basin and 
the remaining 43 reservoirs are located within the Brazos River basin. 
There are also eleven new reservoirs that have been recommended for 
development as feasible alternatives to meet future water needs within 
the Brazos River basin (Brazos G Regional Water Planning Group 2010, p. 
4B.12-1). In addition, six new off-channel reservoirs are also being 
considered for future development (Brazos G Regional Water Planning 
Group 2010, p. 4B.13-2). At least one of the proposed reservoir sites 
on the Little River in Milam County is in the vicinity of where a 
single live smooth pimpleback was found in 2006 (Karatayev and 
Burlakova 2008, p. 6).
    Dam construction fragments the range of smooth pimpleback, leaving 
remaining habitats and populations isolated by the structures as well 
as by extensive areas of deep, uninhabitable, impounded waters. These 
isolated populations are unable to naturally recolonize suitable 
habitat that may be impacted by temporary but devastating events, such 
as severe drought, chemical spills, or unauthorized discharges. Dams 
impound river habitats throughout almost the entire range of the 
species. These impoundments have left short and isolated patches of 
remnant habitat, typically in between impounded reaches. Habitat 
downstream of dams may be impaired for many miles; in the Brazos River 
downstream of Possum Kingdom Reservoir, substrate was unstable for 150 
km (240 mi) below the dam (Yeager 1993, p. 68).
    For species such as smooth pimpleback that may be able to survive 
the initial inundation of reservoirs, conditions within the reservoir 
are likely to become uninhabitable. The deep water in reservoirs is 
very cold and often devoid of oxygen and necessary nutrients (Watters 
2000, p. 264). Cold water (less than 11 [deg]C (52 [deg]F)) has been 
shown to stunt mussel growth (Hanson et al. 1988, p. 352). Because 
mussel reproduction is temperature dependent (Watters and O'Dee 1999, 
p. 455), it is

[[Page 62193]]

likely that individuals living in the constantly cold hypolimnion in 
these channels may never reproduce, or reproduce less frequently 
(Watters 2000, p. 264). Any smooth pimpleback that survived the initial 
inundation may have been unable to reproduce, eventually eliminating 
the species from large areas of the reservoir. The same would be true 
for mussels living in cold-water discharges downstream of large 
impoundments (Watters 2000, p. 264).
    The widespread construction of dams throughout the range of smooth 
pimpleback has significantly altered stream habitat both upstream and 
downstream of the dams by changing fish assemblages, temperature, 
dissolved oxygen, and substrate. The effects of dams are ongoing, 
decades after construction. In addition, the construction of new 
reservoirs is also being considered within the species' range that 
could result in additional habitat loss. Because of this loss of 
habitat and its effects on the populations, we conclude that the 
effects of impoundments are a threat to the smooth pimpleback.
Sedimentation
    For general information on the effects of sedimentation on 
freshwater mussels, please refer to ``Sedimentation'' under Factor A in 
Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussel species, the smooth pimpleback is 
also threatened by sedimentation. The dominant land use in the Colorado 
River basin is grazing (Hersh 2007, p. 11). Soil compaction from 
intensive grazing may reduce infiltration rates and increase runoff, 
and trampling of riparian vegetation increases the probability of 
erosion (Armour et al. 1994, p. 10; Brim Box and Mossa 1999, p. 103). 
Additionally, much of the Brazos River basin is grazed or farmed for 
row crops, which often contributes large amounts of sediment to the 
basin (Brazos River Authority 2007, p. 4). Reservoir construction in 
the upper portion of the basin has been attributed with the erosion and 
subsequent sedimentation of the lower river (USGS 2001, p. 30), as 
sediment-poor tailwaters scour the riverbanks below the dam and deposit 
sediment farther downstream. In 2004, sedimentation was high enough in 
the Brazos River below Possum Kingdom Reservoir to cause residents to 
raise concerns to the Brazos River Authority (Brazos River Authority 
2006, p. 2), and elevated suspended sediment levels have been reported 
throughout the basin (Brazos River Authority 2006, p. 8).
    Sedimentation may become an increasing threat to the smooth 
pimpleback in the Colorado and Brazos River basins as the Austin 
metropolitan area continues to expand. Activities associated with 
urbanization, such as road construction, increased impervious surfaces, 
and road construction can be detrimental to stream habitats (Couch and 
Hamilton 2002, p. 1). The City of Austin, population approximately 
800,000 people (Austin City Connection 2011, p. 1) lies within the 
Colorado River basin, and 3.9 million people live within the Brazos 
River basin (Brazos River Authority 2007, p. 1). Both of these basins 
have undergone substantial urbanization providing sources of increased 
sediment runoff into habitats of the smooth pimpleback.
    The range of the smooth pimpleback receives sediment from 
increasing levels of sedimentation from agriculture, urbanization, and 
sand and gravel mining; sedimentation is likely to continue to threaten 
the smooth pimpleback.
Dewatering
    River dewatering can occur in several ways: Anthropogenic 
activities such as surface water diversions and groundwater pumping, 
and natural events, such as drought, which can result in mussels 
stranded in previously wetted areas. This is a particular concern for 
smooth pimpleback within and below reservoirs, where water levels are 
managed for various purposes that can cause water levels in the 
reservoir or downstream to rise or fall in very short periods of time, 
such as when hydropower facilities release water during peak energy 
demand periods. The three impoundments on the Colorado River with 
records of smooth pimpleback all experience periodic water level 
drawdowns, which may have contributed to the species' apparent 
extirpation from Inks Lake and Lake Marble Falls. In fact, smooth 
pimpleback have been found stranded (which leads to death) after 
drawdowns in both of these reservoirs (Howells 1996, p. 22; 1999, p. 
16).
    Drought can also severely impact smooth pimpleback populations. For 
example, the Little Brazos River, which once contained a diverse and 
numerous freshwater mussel community that included smooth pimpleback 
(Gentner and Hopkins 1966, p. 458), experienced a severe drought from 
about 1950 to 1956 that reduced the river to a series of small, 
stagnant pools. The results of this habitat degradation from the low 
water nearly eliminated the mussel community and killed many smooth 
pimpleback (Gentner and Hopkins 1966, p. 458). Later, central Texas, 
including the Colorado and Brazos River basins, experienced a major 
drought in the late 1970s (Lewis and Oliveria 1979, p. 243). Near 
record dry conditions in 2008 followed by a pattern of below-normal 
rainfall during the winter and spring of 2009 led to one of the worst 
droughts in recorded history for most of central Texas, including the 
range of the smooth pimpleback (Nielsen-Gammon and McRoberts 2009, p. 
2). This drought's severity was exacerbated by abnormally high air 
temperatures, a likely effect of climate change, which has already 
increased average air temperatures in Texas by at least 1 [deg]C (1.8 
[deg]F) (Nielsen-Gammon and McRoberts 2009, p. 22). Instream flows 
throughout the Brazos River basin during this drought were 
significantly reduced (USGS 2011c, p. 1) and smooth pimpleback 
populations in areas with reduced water levels, such as in the middle 
Brazos River, may have been negatively affected. Central Texas is 
currently experiencing another extreme drought, with rainfall between 
October 2010 and July 2011 being the lowest on record during those 
months (LCRA 2011c, p. 1); the effects of this drought are being 
observed but are not yet fully known. Droughts result in a decrease in 
water depth and flow velocity in streams inhabited by smooth 
pimpleback, which reduces the availability of food and dissolved oxygen 
and reduces survivability. As droughts persist, mussels face hypoxia, 
elevated water temperature and, ultimately, death due to stranding 
(Golladay et al. 2004, p. 501).
Sand and Gravel Mining
    For general information on the effects of sand and gravel mining on 
freshwater mussels, please refer to ``Sand and Gravel Mining'' under 
Factor A in Five-Factor Evaluation for Texas Fatmucket.
    The Brazos River has a long history of sand mining, particularly in 
the lower river, and channel morphology changes have been attributed to 
destabilization due to instream sand mining in the area (USGS 2001, p. 
27). The removal of sand from within the river creates sediment traps 
during periods of high flow, which causes scouring and erosion 
downstream (USGS 2001, p. 27). One gravel dredging operation in the 
Brazos River was documented depositing sediment as far as 1.6 km (1 
mile) downstream (Forshage and Carter 1973, p. 697). Accelerated stream 
bank erosion and downcutting of streambeds are common effects of 
instream sand and gravel mining, as is the mobilization of fine 
sediments during sand and gravel extraction (Roell 1999, p. 7).

[[Page 62194]]

    Within the range of the smooth pimpleback, TPWD has issued permits 
for four current sand mining activities within the Brazos River 
(Austin, Bosque, and Fort Bend Counties) (TPWD 2004, p. 1; 2007b, p. 1, 
2008b, p. 1; 2010b, p. 1). The permits allow for the repeated removal 
of sand and gravel at various locations within the Brazos River. The 
lower Brazos River, where these mining activities occur, contains one 
of the more numerous populations of smooth pimpleback.
    The smooth pimpleback population in the lower Brazos River may be 
currently affected by sand and gravel mining. These activities occur 
over a long period of time, destabilizing mussel habitat both upstream 
and downstream, which decreases the likelihood of recolonization after 
the activity has been completed. Therefore, the effects of sand and 
gravel mining are an ongoing threat to the smooth pimpleback and are 
expected to continue to occur throughout the range of the species.
Chemical Contaminants
    For general information on the effects of chemical contaminants on 
freshwater mussels, please refer to ``Chemical Contaminants'' under 
Factor A in Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussels, the smooth pimpleback is also 
threatened by chemical contaminants. TCEQ data for 2010 indicated that 
26 of the 98 assessed water bodies within Colorado River basin and 81 
of approximately 124 assessed water bodies within Brazos River basin 
did not meet surface water quality standards and were classified as 
impaired water bodies (Texas Clean Rivers Program 2010a, p. 5; TCEQ 
2010c, pp. 1-106). These water bodies were impaired with dissolved 
solids, nitrites, nitrates, bacteria, low dissolved oxygen, aluminum, 
sulfates, selenium, chloride, orthophosphorus, phosphorus, Chlorophyll 
a, and low pH associated with agricultural, urban, municipal, and 
industrial runoff. Of these, nitrites and low dissolved oxygen are 
known to be harmful to freshwater mussels. Agricultural pesticides and 
emerging contaminants are likely also present in streams inhabited by 
smooth pimpleback. There are 53 wastewater treatment plants permitted 
to discharge more than one million gallons per day into the Brazos 
River basin (Valenti and Brooks 2008, p. 12); the outfalls of these 
treatment plants have not been tested to determine if they contain 
contaminants of note.
    Examples of the exposure of smooth pimpleback to chemical 
contaminants include an event in 1993 when an unknown substance was 
dumped into a segment of the Little Brazos River upstream from a smooth 
pimpleback population. This site once supported an abundant and diverse 
number of mussel species, including the smooth pimpleback, but when it 
was revisited in 1993, a massive die-off of freshwater mussels had 
occurred (Howells 2010b, p. 11). In another instance in 2010, crude oil 
overflowed from a failed storage tank into Keechi Creek in Leon County, 
a tributary to the Navasota River (National Response Center 2010, p. 
2). This location is near a small population of smooth pimpleback and 
upstream of one of the largest known populations of the species.
    Numerous other spills have occurred within the range of the smooth 
pimpleback. These occurred from on-site accidents (storage tank or 
pipeline spills) or from tanker truck accidents within watersheds 
occupied by smooth pimpleback. For example, oil has spilled into the 
Brazos River a number of times. As much as 320,000 L (84,000 gal) of 
crude oil was spilled in the Brazos River in Knox County in 1991 
(Associated Press 1991, p. 1). In June 2010, flooding of holding ponds 
adjacent to oil drilling operations leaked oil into Thompson Creek and 
subsequently into the Brazos River (Lewis 2010, p. 1). Also, in July 
2010, oil pipelines burst and released approximately 165 barrels of 
crude oil into the upper Double Mountain Fork of the Brazos River in 
Garza County (Joiner 2010, p. 1). Although no analyses were conducted 
of the specific effects of these spills on smooth pimpleback, we expect 
that if the mussels are exposed to even moderate levels of toxic 
chemical contaminants, such as crude oil, adverse effects (both direct 
mortality and indirect effects to food source availabity) are likely to 
occur.
    Releases of chemical contaminants, such as oil, ammonia, copper, 
mercury, nutrients, pesticides, and other compounds into the habitat of 
the smooth pimpleback are an ongoing threat to the smooth pimpleback. 
The species is vulnerable to acute contamination from spills, as well 
as chronic contaminant exposure, which has occurred and is expected to 
continue to occur throughout the range of the smooth pimpleback.
Summary of Factor A
    The reduction in numbers and range of the smooth pimpleback is 
primarily the result of the long-lasting effects of habitat alterations 
such as the effects of impoundments, sedimentation, dewatering, sand 
and gravel mining, and chemical contaminants. Impoundments occur 
throughout the range of the species and have far-reaching effects to 
riverine habitat both upstream and downstream of the dams. Both the 
Colorado and Brazos River systems have experienced a large amount of 
sedimentation from agriculture, instream mining, and urban development. 
Sand and gravel mining affects smooth pimpleback habitat by increasing 
sedimentation and channel instability downstream and by causing 
headcutting upstream. Chemical contaminants exceeding the standards 
developed to support aquatic life have been documented throughout the 
range of the species and may represent a significant threat to the 
smooth pimpleback. However, the large populations in the San Saba 
River, lower Brazos River, Navasota River, Leon River, and Yegua Creek 
indicate that some smooth pimpleback populations are not currently as 
vulnerable to habitat loss as others. Therefore, based upon our review 
of the best commercial and scientific data available, we conclude that 
the present or threatened destruction, modification, or curtailment of 
its habitat or range is an immediate threat of moderate magnitude to 
the smooth pimpleback.
    Factor B. Overutilization for Commercial, Recreational, Scientific, 
or Educational Purposes.
    The smooth pimpleback is not a commercially valuable species and 
has never been harvested in Texas as a commercial mussel species 
(Howells 2010b, p.12). Some scientific collecting occurs but is not 
likely to be a significant threat to the species because it occurs only 
rarely. However, handling mussels can disturb gravid females and result 
in glochidial loss and subsequent reproductive failure. Additionally, 
handling has also been shown to reduce shell growth across mussel 
species, including several species of Lampsilis (Haag and Commens-
Carson 2008, pp. 505-506). Repeated handling by researchers may 
adversely affect smooth pimpleback individuals, but these activities 
are occurring rarely and are not likely to be a threat to populations. 
Handling for scientific purposes contributes to the long-term 
conservation of the species.
    We do not have any evidence of risks to the smooth pimpleback from 
overutilization for commercial, recreational, scientific, or 
educational purposes, and we have no reason to believe this factor will 
become a threat to the species in the future. Based upon the best 
scientific and commercial information available, we conclude that 
overutilization for commercial, recreational, scientific, or 
educational

[[Page 62195]]

purposes does not pose a threat to the smooth pimpleback rangewide.
    Factor C. Disease and Predation.
Disease
    Little is known about disease in freshwater mussels. However, 
disease is believed to be a contributing factor in documented mussel 
die-offs in other parts of the United States (Neves 1987, pp. 11-12). 
Diseases have not been documented or observed during any studies of 
smooth pimpleback.
Predation
    Raccoons will prey on freshwater mussels stranded by low waters or 
deposited in shallow water or on bars following flooding or low water 
periods (Howells 2010c, p. 12). Predation of smooth pimpleback by 
raccoons may be occurring occasionally, but there is no indication it 
is a significant threat to the status of the species.
    Some species of fish feed on mussels, such as common carp, 
freshwater drum, and redear sunfish, all of which are common throughout 
the range of smooth pimpleback (Hubbs et al. 2008, pp. 19, 45, 53). 
Common species of flatworms are voracious predators of newly 
metamorphosed juvenile mussels of many species (Zimmerman et al. 2003, 
p. 30). Predation is a normal factor influencing the population 
dynamics of a healthy mussel population; however, predation may amplify 
declines in small populations primarily caused by other factors.
Summary of Factor C
    Disease in freshwater mussels is poorly known, and we do not have 
any information indicating it is a threat to the smooth pimpleback. 
Additionally, predation is a natural ecological interaction and we have 
no information indicating the extent of any predation is a threat to 
populations of smooth pimpleback. Based upon the best scientific and 
commercial information available, we conclude that disease or predation 
is not a threat to the smooth pimpleback.
    Factor D. The Inadequacy of Existing Regulatory Mechanisms.
    Existing regulatory mechanisms that could have an effect on threats 
to the smooth pimpleback include State and Federal laws such as Texas 
Threatened and Endangered Species regulations and freshwater mussel 
sanctuaries, State and Federal sand and gravel mining regulations, and 
regulation of point and non-point source pollution. For more 
information on the effects of State and Federal laws on the threats to 
freshwater mussels in central Texas, please refer to Factor D under 
Five-Factor Evaluation for Texas Fatmucket.

Summary of Factor D

    Despite State and Federal laws protecting the species and water 
quality, the smooth pimpleback continues to decline due to the effects 
of habitat destruction, poor water quality, contaminants, and other 
factors. The regulatory measures described under Factor D in the Five-
Factor Evaluation for Texas Fatmucket have been insufficient to 
significantly reduce or remove the threats to the smooth pimpleback. 
Based upon our review of the best commercial and scientific data 
available, we conclude that the lack of existing regulatory mechanisms 
is an immediate and ongoing threat of moderate magnitude to the smooth 
pimpleback.
    Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence.
    Natural and manmade factors that threaten the smooth pimpleback 
include climate change, population fragmentation and isolation, and 
nonnative species.
Climate Change
    For general information on the effects of climate change on 
freshwater mussels of central Texas, please refer to ``Climate Change'' 
under Factor E in Five-Factor Evaluation for Texas Fatmucket. Because 
the range of the smooth pimpleback has been reduced to isolated 
locations, many with low population numbers, in small rivers and 
streams, the smooth pimpleback is vulnerable to climatic changes that 
could decrease the availability of water.
    The disjunct nature of the remaining smooth pimpleback populations, 
coupled with the limited ability of mussels to migrate, makes it 
unlikely that smooth pimpleback can adjust their range in response to 
changes in climate (Strayer 2008, p. 30). Climate change exacerbates 
threats to the smooth pimpleback, such as habitat degradation from 
prolonged periods of drought; increased water temperature; and the 
increased allocation of water for municipal, agricultural, and 
industrial uses The magnitude and imminence of these effects, however, 
remain uncertain. Based upon our review of the best commercial and 
scientific data available, we conclude that the effects of climate 
change in the future will likely exacerbate the current and ongoing 
threats of habitat loss and degradation caused by other factors, as 
discussed in Factor A.
Population Fragmentation and Isolation
    For general information on the effects of population fragmentation 
and isolation on freshwater mussels of central Texas, please refer to 
``Population Fragmentation and Isolation'' under Factor E in Five-
Factor Evaluation for Texas Fatmucket. As with many freshwater mussels, 
several of the remaining populations of the smooth pimpleback are small 
and geographically isolated and thus are susceptible to genetic drift, 
inbreeding depression, and random or chance changes to the environment, 
such as toxic chemical spills (Watters and Dunn 1995, pp. 257-258), or 
dewatering. Historically, the smooth pimpleback was widespread 
throughout much of the Colorado and Brazos River systems when few 
natural barriers existed to prevent migration (via host species) among 
suitable habitats. The extensive impoundment of the Brazos and Colorado 
River basins has fragmented smooth pimpleback populations throughout 
these river systems.
    Small smooth pimpleback populations, including those in Lake LBJ 
Reservoir and the middle Brazos, Little, and Little Brazos Rivers, may 
be below the minimum population size required to maintain population 
viability into the future, therefore making these populations more 
vulnerable to extirpation since they are less likely to be able to 
recover through recruitment from events that reduce but do not 
extirpate populations. Additionally, these small populations are more 
vulnerable to extirpation from stochastic events, as the lack of 
connectivity among populations does not permit nearby populations to 
recolonize areas affected by intense droughts, toxic spills, or other 
isolated events that result in significant mussel die-offs. While the 
small, isolated populations do not represent an independent threat to 
the species, the situation does substantially increase the risk of 
extirpation from the effects of all other threats, including those 
addressed in this analysis, and those that could occur in the future 
from unknown sources.
    Based upon our review of the best commercial and scientific data 
available, we conclude that fragmentation and isolation of small 
remaining populations of the smooth pimpleback are occurring and are 
ongoing threats to the species throughout all of its range. Further, 
stochastic events may play a magnified role in extirpation of small, 
isolated populations.

[[Page 62196]]

Nonnative Species
    For general information on the effects of nonnative species on 
freshwater mussels of central Texas, please refer to ``Nonnative 
Species'' in Factor E under Five-Factor Evaluation for Texas Fatmucket. 
As with other freshwater mussels, the smooth pimpleback is threatened 
by nonnative species. Various nonnative aquatic species pose a threat 
to the smooth pimpleback, including golden algae, zebra mussels, and 
black carp. Of these, golden algae has been responsible for killing 
more than eight million fish in the Brazos River since 1981 and more 
than two million fish in the Colorado River since 1989 (TPWD 2010a, p. 
1). Although mussel kills due to golden algae have not been recorded, 
we expect golden algae to negatively affect mussel populations through 
loss of host fish and direct toxicity. Zebra mussels and black carp do 
not currently occur within the range of the smooth pimpleback, although 
both are found in Texas and could be introduced to the Brazos and 
Colorado Rivers in the forseeable future. Based on population responses 
of other mussel species that overlap with zebra mussels and black carp 
in similar river conditions, we conclude that the introduction of zebra 
mussels or black carp into the range of smooth pimpleback would be 
devastating to the species.
    Based upon our review of the best commercial and scientific data 
available, we conclude that golden algae is an ongoing threat to the 
smooth pimpleback, and other nonnative species, such as zebra mussels 
and black carp, are a potential threat to the smooth pimpleback that is 
likely to increase as these exotic species expand their occupancy to 
include the range of the smooth pimpleback.
Summary of Factor E
    The effects of climate change, while difficult to quantify at this 
time, are likely to exacerbate the current and ongoing threat of 
habitat loss caused by other factors, and the small sizes and 
fragmented nature of the remaining populations render them more 
vulnerable to extirpation. In addition, nonnative species, such as 
golden algae, currently threaten the Texas fatmucket, and the potential 
introduction of zebra mussels and black carp are potential future 
threats. Based upon our review of the best commercial and scientific 
data available, we conclude that other natural or manmade factors are 
immediate and ongoing threats of moderate magnitude to the smooth 
pimpleback.

Finding for Smooth Pimpleback

    As required by the Act, we considered the five factors in assessing 
whether the smooth pimpleback is threatened or endangered throughout 
all of its range. We examined the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by the smooth pimpleback. We reviewed the petition, information 
available in our files, and other available published and unpublished 
information, and we consulted with recognized smooth pimpleback experts 
and other Federal and State agencies.
    This status review identifies threats to the smooth pimpleback 
attributable to Factors A, D, and E. The primary threat to the species 
is from habitat destruction and modification (Factor A) from 
impoundments, which scour riverbeds, thereby removing mussel habitat, 
decreases water quality, modifies stream flows, and restricts fish host 
migration and distribution of freshwater mussels. Additional threats 
under Factor A include sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. Also, most of these threats may be 
exacerbated by the current and projected effects of climate change 
(discussed under Factor E). Threats to the smooth pimpleback are not 
being adequately addressed through existing regulatory mechanisms 
(Factor D). Because of the limited distribution of this endemic species 
and its lack of mobility, these threats are likely to lead to the 
extinction of the smooth pimpleback in the foreseeable future.
    On the basis of the best scientific and commercial information 
available, we find that the petitioned action to list the smooth 
pimpleback under the Act is warranted. We will make a determination on 
the status of the species as threatened or endangered when we complete 
a proposed listing determination. When we complete a proposed listing 
determination, we will examine whether the species may be endangered or 
threatened throughout all of its range; or whether the species may be 
endangered or threatened in a significant portion of its range. 
However, as explained in more detail below, an immediate proposal of a 
regulation implementing this action is precluded by higher priority 
listing actions, and progress is being made to add or remove qualified 
species from the Lists of Endangered and Threatened Wildlife and 
Plants.
    We reviewed the available information to determine if the existing 
and foreseeable threats render the smooth pimpleback at risk of 
extinction now such that issuing an emergency regulation temporarily 
listing the species under section 4(b)(7) of the Act is warranted. We 
determined that issuing an emergency regulation temporarily listing the 
species is not warranted for the smooth pimpleback at this time, 
because we have not identified a threat or activity that poses a 
significant risk, such that losses to the species during the normal 
listing process would endanger the continued existence of the entire 
species. However, if at any time we determine that issuing an emergency 
regulation temporarily listing the smooth pimpleback is warranted, we 
will initiate this action at that time.

Listing Priority Number for Smooth Pimpleback

    The Service adopted guidelines on September 21, 1983 (48 FR 43098), 
to establish a rational system for utilizing available resources for 
the highest priority species when adding species to the Lists of 
Endangered and Threatened Wildlife and Plants or reclassifying species 
listed as threatened to endangered status. These guidelines, titled 
``Endangered and Threatened Species Listing and Recovery Priority 
Guidelines'' address the immediacy and magnitude of threats, and the 
level of taxonomic distinctiveness by assigning priority in descending 
order to monotypic genera (genus with one species), full species, and 
subspecies (or equivalently, distinct population segments of 
vertebrates).
    As a result of our analysis of the best available scientific and 
commercial information, we have assigned the smooth pimpleback an LPN 
of 8, based on our finding that the species faces threats that are of 
moderate magnitude and are imminent. These threats include habitat loss 
and degradation from impoundments, sedimentation, sand and gravel 
mining, and chemical contaminants; other natural or manmade factors 
such as climate change, small, isolated populations, and nonnative 
species; and the fact that the threats to the species are not being 
adequately addressed by existing regulatory mechanisms. Our rationale 
for assigning the smooth pimpleback an LPN of 8 is outlined below.
    We consider the threats that the smooth pimpleback faces to be 
moderate in magnitude. Habitat loss and degradation from impoundments, 
sedimentation, sand and gravel mining, and chemical contaminants are 
widespread throughout the range of the smooth pimpleback, but several 
large populations remain, including one that was recently discovered, 
indicating the threats are not high in magnitude.

[[Page 62197]]

    Under our LPN guidelines, the second criterion we consider in 
assigning a listing priority is the immediacy of threats. We consider 
the threats to the smooth pimpleback as described under ``Factor A. The 
Present or Threatened Destruction, Modification, or Curtailment of Its 
Habitat or Range,'' ``Factor D. The Inadequacy of Existing Regulatory 
Mechanisms,'' and ``Factor E. Other Natural Or Manmade Factors 
Affecting Its Continued Existence'' under the Five-Factor Evaluation 
for Smooth Pimpleback to be imminent because these threats are ongoing 
and will continue in the foreseeable future. Habitat loss and 
destruction has already occurred and will continue as the human 
population continues to grow in central Texas. Several smooth 
pimpleback populations may already be below the minimum viable 
population requirement, which would cause a reduction in the number of 
populations and an increase in the species' vulnerability to 
extinction. These threats are exacerbated by climate change, which will 
increase the frequency and magnitude of droughts. Therefore, we 
consider these threats to be imminent.
    Thirdly, the smooth pimpleback is a valid taxon at the species 
level and, therefore, receives a higher priority than subspecies, but a 
lower priority than species in a monotypic genus. Therefore, we 
assigned smooth pimpleback an LPN of 8. We will continue to monitor the 
threats to the smooth pimpleback and the species' status on an annual 
basis, and should the magnitude or imminence of the threats change, we 
will revisit our assessment of the LPN.
    While we conclude that listing the smooth pimpleback is warranted, 
an immediate proposal to list this species is precluded by other higher 
priority listings, which we address in the Preclusion and Expeditious 
Progress section below. Because we have assigned the smooth pimpleback 
an LPN of 8, work on a proposed listing determination for the species 
is precluded by work on higher priority listing actions with absolute 
statutory, court-ordered, or court-approved deadlines and final listing 
determinations for those species that were proposed for listing with 
funds from Fiscal Year (FY) 2011. This work includes all the actions 
listed in the tables below under Preclusion and Expeditious Progress.

Five-Factor Evaluation for Texas Pimpleback

    Information pertaining to the Texas pimpleback in relation to the 
five factors provided in section 4(a)(1) of the Act is discussed below.
    Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range.
    As discussed above, the decline of mussels in Texas and across the 
United States is primarily the result of habitat loss and degradation. 
Chief among the causes of decline of the Texas pimpleback are the 
effects of impoundments, sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. These threats are discussed below.
Impoundments
    For general information on the effects of impoundments on 
freshwater mussels, please refer to ``Impoundments'' in Factor A under 
Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussel species, the Texas pimpleback is 
also threatened by impoundments. There are 37 major reservoirs and 
numerous smaller impoundments within the historical and current range 
of the Texas pimpleback. There are 31 major reservoirs within the 
Colorado River basin, with another reservoir (Goldthwaite Reservoir) 
proposed for the Colorado River in San Saba County near a Texas 
pimpleback population; this reservoir was the number one recommendation 
in the water plan for the region (TWDB 2011, pp. 4-85). There are 29 
reservoirs within the Guadalupe River basin and 34 within the San 
Antonio River basin, each with a storage capacity of 3,000 acre-feet or 
more, and many other smaller reservoirs (Exelon 2010, p. 2.3-4). The 
majority of the large dams were constructed for power generation, flood 
control, and water supply by the Lower Colorado River and Guadalupe-
Blanco River Authorities beginning as early as 1935 (Guadalupe-Blanco 
River Authority 2011, p. 1; LCRA 2011a, p. 1). These and numerous 
smaller dams occur throughout the Colorado and Guadalupe River basins, 
fragmenting habitat and populations of Texas pimpleback.
    There are no natural lakes within the range of the Texas 
pimpleback, nor has it ever been found in reservoirs. Historically, the 
Texas pimpleback could be found in areas of the Guadalupe River in 
Comal County (Randklev et al. 2010c, p. 4), but it has not been found 
in the area since the construction of Canyon Reservoir (Burlakova and 
Karatayev 2009, p. 6). We presume the species is extirpated from this 
reach because of the effects of the reservoir. Surveys of other 
reservoirs on the Guadalupe and Colorado Rivers have been ongoing since 
at least 1992, and no evidence of live or dead Texas pimpleback has 
been found in any reservoir (Howells 1994, pp. 1-20; 1995, pp. 1-50; 
1996, pp. 1-45; 1997a, pp. 1-58; 1998, pp. 1-30; 1999, pp. 1-34; 2000a, 
pp. 1-56; 2001, pp. 1-50; 2002a, pp. 1-28; 2003, pp. 1-42; 2004, pp. 1-
48; 2005, pp. 1-23; 2006, pp. 1-106; Karatayev and Burlakova 2008, pp. 
1-47; Burlakova and Karatayev 2010a, pp. 1-30; 2011, pp. 1-8), further 
indicating that this species is not tolerant of impoundments.
    Texas pimpleback populations downstream of dams are affected as 
well. Cold water (less than 11 [deg]C (52 [deg]F)) has been shown to 
stunt mussel growth (Hanson et al. 1988, p. 352) and reduce or inhibit 
reproduction, because mussel reproduction is temperature dependent 
(Watters and O'Dee 1999, pp. 455). Texas pimpleback living in cold-
water discharges downstream of large impoundments are unlikely to 
reproduce (Watters 2000, p. 264).
    Dam construction also fragments the range of Texas pimpleback, 
leaving remaining habitats and populations isolated by the structures 
as well as by extensive areas of deep, uninhabitable, impounded waters. 
These isolated populations are unable to naturally recolonize suitable 
habitat that may be impacted by temporary but devastating events, such 
as severe drought, chemical spills, or unauthorized discharges. Dams 
impound river habitats throughout almost the entire range of the 
species. These impoundments have left short and isolated patches of 
suitable habitat, typically in between impounded reaches.
    The widespread construction of dams throughout the range of Texas 
pimpleback has significantly altered stream habitat both upstream and 
downstream of the dams by changing fish assemblages, temperature, 
dissolved oxygen, and substrate. The effects of dams are ongoing 
decades after construction. Because of this loss of habitat and its 
effects on the populations, we conclude that the effects of dams are a 
threat to the Texas pimpleback.
Sedimentation
    For general information on the effects of sedimentation on 
freshwater mussels, please refer to ``Sedimentation'' in Factor A under 
Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussel species, the Texas pimpleback is 
affected by sedimentation. The dominant land use in the Colorado River 
basin is grazing (Hersh 2007, p. 11); soil compaction from intensive

[[Page 62198]]

grazing may reduce infiltration rates and increase runoff, and 
trampling of riparian vegetation increases the probability of erosion 
(Armour et al. 1994, p. 10; Brim Box and Mossa 1999, p. 103). Even in 
1959, the Guadalupe River was noted as having high sedimentation rates 
from agricultural activities (Soil Conservation Service 1959, p. 59). 
Turbidity has also been recorded as high in the Guadalupe River near 
Victoria (Exelon 2010, p. 2.3-186), indicating a large amount of 
suspended sediment where a small Texas pimpleback population was 
recently found.
    Streams occupied by Texas pimpleback are subject to increasing 
levels of sedimentation from agriculture, urbanization, and sand and 
gravel mining. Agriculture is a common land use in the Guadalupe and 
San Antonio River basins, and the city of San Antonio, the second 
largest city in Texas, continues to grow (City of San Antonio 2010, p. 
5). Sedimentation from agriculture, urbanization, and sand and gravel 
mining will continue to threaten the Texas pimpleback in the 
foreseeable future.
Dewatering
    River dewatering can occur in several ways: Anthropogenic 
activities such as surface water diversions and groundwater pumping, 
and natural events, such as drought, which can result in mussels 
stranded in previously wetted areas. This is a particular concern below 
reservoirs, whose water levels are managed for various purposes that 
can cause water levels in the reservoir or downstream to rise or fall 
in very short periods of time, such as when hydropower facilities 
release water during peak energy demand periods.
    Drought can also severely impact Texas pimpleback populations. 
Central Texas, including the Colorado and Guadalupe River basins, 
experienced a major drought in the late 1970s (Lewis and Oliveria 1979, 
p. 243). Near record dry conditions in 2008 followed by a pattern of 
below-normal rainfall during the winter and spring of 2009 led to one 
of the worst droughts in recorded history for most of central Texas, 
including the range of the Texas pimpleback (Nielsen-Gammon and 
McRoberts 2009, p. 2). This drought's severity was exacerbated by 
abnormally high air temperatures, a likely effect of climate change, 
which has already increased average air temperatures in Texas by at 
least 1 [deg]C (1.8 [deg]F) (Nielsen-Gammon and McRoberts 2009, p. 22). 
Instream flows throughout the Colorado River basin during this drought 
were significantly reduced (USGS 2011c, p. 1) and Texas pimpleback 
populations in areas with reduced water levels may have been negatively 
affected. Central Texas is currently experiencing another extreme 
drought, with rainfall between October 2010 and July 2011 being the 
lowest on record during those months (LCRA 2011c, p. 1); the effects of 
this drought are being observed but are not yet fully known. Droughts 
result in a decrease in water depth and flow velocity, which reduces 
food and oxygen delivery. As droughts persist, mussels face hypoxia, 
elevated water temperature and, ultimately, stranding (Golladay et al. 
2004, p. 501).
    We do not know the extent of the impacts of stream dewatering on 
the Texas pimpleback; however, because several populations are small 
and isolated, the loss of numerous individuals at a site can have 
dramatic consequences to the population. Hydropower facilities, 
diversions associated with construction, and drought are occurring 
throughout the range of the Texas pimpleback; therefore, the effects of 
dewatering are ongoing and unlikely to decrease, resulting in 
significant threats to the Texas pimpleback.
Sand and Gravel Mining
    For general information on the effects of sand and gravel mining on 
freshwater mussels, please refer to ``Sand and Gravel Mining'' in 
Factor A under Five-Factor Evaluation for Texas Fatmucket.
    In 1995, the reach of the Guadalupe River near Victoria, which 
contains a Texas pimpleback population, was described as having 
numerous current and abandoned sand and gravel mining areas (USACE 
1995, p. 7). Currently, TPWD has permitted one sand mining activity 
within the current range of Texas pimpleback, in the Guadalupe River 
basin in Comal County (TPWD 2009b, p. 1); a small Texas pimpleback 
population occurs downstream of this area in the Guadalupe River. The 
permit allows for the repeated removal of sand and gravel at various 
locations within the stream.
    Headcuts from sand and gravel mining operations have been 
documented in the San Antonio River basin in Karnes County from as 
early as 1967, with downstream channels having steep, eroded banks 
(Kennon et al. 1967, p. 22). There has been no evidence of Texas 
pimpleback in Karnes County in recent years (Howells 1997a, pp. 41-42), 
and the effects of sand mining may have been a factor in the species' 
extirpation.
    The Texas pimpleback population in the Guadalupe River may be 
currently threatened by sand and gravel mining. These activities occur 
over a long period of time, destabilizing habitat both upstream and 
downstream, which decreases the likelihood of recolonization after the 
activity has been completed. Therefore, the effects of sand and gravel 
mining are an ongoing threat to the Texas pimpleback.
Chemical Contaminants
    For general information on the effects of chemical contaminants on 
freshwater mussels, please refer to ``Chemical Contaminants'' in Factor 
A under Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussels, the Texas pimpleback is affected 
by chemical contaminants. TCEQ data for 2010 indicated that 26 of the 
98 assessed water bodies within the historical and current range of the 
Texas pimpleback did not meet surface water quality standards and were 
classified as impaired water bodies under the Clean Water Act (Texas 
Clean Rivers Program 2010a, p. 5). These water bodies were impaired 
with dissolved solids, nitrates, bacteria, low dissolved oxygen, 
aluminum, sulfates, selenium, chloride, and low pH associated with 
agricultural, urban, municipal, and industrial runoff. Additionally, 
the Concho River near Paint Rock has been repeatedly documented as 
having high nitrates (Texas Clean Rivers Program 2008, p. 2); a 
significant Texas pimpleback population occurs just upstream of this 
site. Nitrates and low dissolved oxygen pose the greatest threat to 
Texas pimpleback.
    Within the range of Texas pimpleback, several streams have been 
listed as impaired due to high ammonia concentrations, including Elm 
Creek in the Guadalupe River basin (TCEQ 2010a, p. 294). Additionally, 
high copper concentrations have been recorded in the lower Guadalupe 
and San Antonio Rivers (Lee and Schultz 1994, p. 8), and mercury has 
been documented throughout the Guadalupe and San Antonio Rivers, with 
particularly high concentrations in fish in the upper reaches of both 
rivers (Lee and Schultz 1994, p. 8). Agricultural pesticides and 
emerging contaminants are likely also present in streams inhabited by 
Texas pimpleback.
    Chemical contaminants, such as ammonia, copper, mercury, nutrients, 
pesticides, and other compounds are currently a threat to the Texas 
pimpleback. The species is vulnerable to acute contamination from 
spills as well as chronic contaminant exposure, which is occurring 
rangewide.
Summary of Factor A
    The reduction in numbers and range of the Texas pimpleback is 
primarily the

[[Page 62199]]

result of the long-lasting effects of habitat alterations such as the 
effects of impoundments, sedimentation, sand and gravel mining, and 
chemical contaminants. Impoundments occur throughout the range of the 
species and have far-reaching effects both up and downstream. Both the 
Colorado and Guadalupe River systems have experienced a large amount of 
sedimentation from agriculture, instream mining, and urban development. 
Sand and gravel mining affects Texas pimpleback habitat by increasing 
sedimentation and channel instability downstream and causing 
headcutting upstream. Chemical contaminants have been documented 
throughout the range of the species and may represent a significant 
threat to the Texas pimpleback. Based upon our review of the best 
commercial and scientific data available, we conclude that the present 
or threatened destruction, modification, or curtailment of its habitat 
or range is an immediate threat of high magnitude to the Texas 
pimpleback.
    Factor B. Overutilization for Commercial, Recreational, Scientific, 
or Educational Purposes.
    The Texas pimpleback was historically harvested occasionally but 
never experienced high levels of collecting pressure (Howells 2010e, 
p.10). Although levels were light enough that commercial harvest was 
likely not a threat to populations, all commercial collecting became 
illegal when Texas pimpleback was listed as threatened by TPWD; 
therefore, commercial harvest is not a current threat to Texas 
pimpleback. Some scientific collecting occurs but is not likely to be a 
significant threat to the species because it occurs only rarely. 
However, handling mussels can disturb gravid females and result in 
glochidial loss and subsequent reproductive failure. Additionally, 
handling has been shown to reduce shell growth across mussel species, 
including several species of Lampsilis (Haag and Commens-Carson 2008, 
pp. 505-506). Repeated handling by researchers may adversely affect 
Texas pimpleback individuals, but these activities are occurring rarely 
and are not likely to be a threat to populations. Handling for 
scientific purposes contributes to the long-term conservation of the 
species.
    We do not have any evidence of risks to the Texas pimpleback from 
overutilization for commercial, recreational, scientific, or 
educational purposes, and we have no reason to believe this factor will 
become a threat to the species in the future. Based upon the best 
scientific and commercial information available, we conclude that 
overutilization for commercial, recreational, scientific, or 
educational purposes does not pose a significant threat to the Texas 
pimpleback rangewide.
    Factor C. Disease and Predation.
Disease
    Little is known about disease in freshwater mussels. However, 
disease is believed to be a contributing factor in documented mussel 
die-offs in other parts of the United States (Neves 1987, pp. 11-12). 
Diseases have not been documented or observed during any studies of 
Texas pimpleback.
Predation
    Raccoons will prey on freshwater mussels stranded by low waters or 
deposited in shallow water or on bars following flooding or low water 
periods (Howells 2010c, p. 12). Predation of Texas pimpleback by 
raccoons may be occurring occasionally but there is no indication it is 
a significant threat to the status of the species.
    Some species of fish feed on mussels, such as common carp, 
freshwater drum, and redear sunfish, all of which are common throughout 
the range of Texas pimpleback (Hubbs et al. 2008, pp. 19, 45, 53). 
Common species of flatworms are voracious predators of newly 
metamorphosed juvenile mussels of many species (Zimmerman et al. 2003, 
p. 30). Predation is a normal factor influencing the population 
dynamics of a healthy mussel population; however, predation may amplify 
declines in small populations primarily caused by other factors.
Summary of Factor C
    Disease in freshwater mussels is poorly known, and we do not have 
any information indicating it is a threat to the Texas pimpleback. 
Additionally, predation is a natural ecological interaction and we have 
no information indicating the extent of any predation is a threat to 
populations of Texas pimpleback. Based upon the best scientific and 
commercial information available, we conclude that disease or predation 
is not a threat to the Texas pimpleback.
    Factor D. The Inadequacy of Existing Regulatory Mechanisms.
    Existing regulatory mechanisms that could have an effect on threats 
to the Texas pimpleback include State and Federal laws such as Texas 
Threatened and Endangered Species regulations and freshwater mussel 
sanctuaries, State and Federal sand and gravel mining regulations, and 
regulation of point and non-point source pollution. For more 
information on the effects of State and Federal laws on the threats to 
freshwater mussels in central Texas, please refer to Factor D under 
Five-Factor Evaluation for Texas

Fatmucket

Summary of Factor D
    Despite State and Federal laws protecting the species and water 
quality, the Texas pimpleback continues to decline due to the effects 
of habitat destruction, poor water quality, contaminants, and other 
factors. The regulatory measures described above have been insufficient 
to significantly reduce or remove the threats to the Texas pimpleback. 
Based upon our review of the best commercial and scientific data 
available, we conclude that the lack of existing regulatory mechanisms 
is an immediate threat of moderate magnitude to the Texas pimpleback.
    Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence.
    Natural and manmade factors that threaten the Texas pimpleback 
include climate change, population fragmentation and isolation, and 
nonnative species.
Climate Change
    For general information on the effects of climate change on 
freshwater mussels of central Texas, please refer to``Climate Change'' 
in Factor E under Five-Factor Evaluation for Texas Fatmucket. Because 
the range of the Texas pimpleback has been reduced to isolated 
locations with low population numbers in small rivers and streams, the 
Texas pimpleback is vulnerable to climatic changes that could decrease 
the availability of water.
    The disjunct nature of the remaining Texas pimpleback populations, 
coupled with the limited ability of mussels to migrate, makes it 
unlikely that Texas pimpleback can adjust their range in response to 
changes in climate (Strayer 2008, p. 30). Climate change could affect 
the Texas pimpleback through the combined effects of global and 
regional climate change, along with the increased probability of long-
term drought. Climate change exacerbates threats such as habitat 
degradation from prolonged periods of drought, increased water 
temperature, and the increased allocation of water for municipal, 
agricultural, and industrial use. Climate change may be a significant 
stressor that exacerbates existing threats by increasing the likelihood 
of prolonged drought. As such, climate change, in and of itself, may 
affect the Texas

[[Page 62200]]

pimpleback, but the magnitude and imminence of the effects remain 
uncertain. Based upon our review of the best commercial and scientific 
data available, we conclude that the effects of climate change in the 
future will likely exacerbate the current and ongoing threats of 
habitat loss and degradation caused by other factors, as discussed 
above.
Population Fragmentation and Isolation
    For more information on the effects of population fragmentation and 
isolation on freshwater mussels of central Texas, please refer to 
``Population Fragmentation and Isolation'' in Factor E under Five-
Factor Evaluation for Texas Fatmucket. As with many freshwater mussels, 
most of the remaining populations of the Texas pimpleback are small and 
geographically isolated and thus are susceptible to genetic drift, 
inbreeding depression, and random or chance changes to the environment, 
such as toxic chemical spills (Watters and Dunn 1995, pp. 257-258) or 
dewatering. Historically, the Texas pimpleback was once widespread 
throughout much of the Colorado and Guadalupe River systems when few 
natural barriers existed to prevent migration (via host species) among 
suitable habitats. The extensive impoundment of the Colorado and 
Guadalupe River basins has fragmented Texas pimpleback populations 
throughout these river systems.
    Small Texas pimpleback populations, including those in the lower 
Guadalupe River, mainstem Colorado River, and San Marcos River, may be 
below the minimum population size required to maintain population 
viability into the future. These populations are more vulnerable to 
extirpation since they are less likely to be able to recover through 
recruitment from events that reduce but do not extirpate populations. 
Additionally, these small populations are more vulnerable to 
extirpation from stochastic events, as the lack of connectivity among 
populations does not permit nearby populations to recolonize areas 
affected by intense droughts, toxic spills, or other isolated events 
that result in significant mussel die-offs. While the small, isolated 
populations do not represent an independent threat to the species, the 
situation does substantially increase the risk of extirpation from the 
effects of all other threats, including those addressed in this 
analysis, and those that could occur in the future from unknown 
sources.
    Based upon our review of the best commercial and scientific data 
available, we conclude that fragmentation and isolation of small 
remaining populations of the Texas pimpleback are occurring and are 
ongoing threats to the species throughout all of its range. Further, 
stochastic events may play a magnified role in extirpation of small, 
isolated populations.
Nonnative Species
    For general information on the effects of nonnative species on 
freshwater mussels of central Texas, please refer to ``Nonnative 
Species'' in Factor E under Five-Factor Evaluation for Texas Fatmucket. 
As with other freshwater mussels, the Texas pimpleback is threatened by 
nonnative species. Various nonnative aquatic species pose a threat to 
the Texas pimpleback, including golden algae, zebra mussels, and black 
carp. Of these, golden algae has been responsible for killing more than 
two million fish in the Colorado River since 1989 (TPWD 2010a, p. 1). 
Although mussel kills due to golden algae have not been recorded, we 
expect golden algae to negatively affect mussel populations through 
loss of host fish and direct toxicity. Zebra mussels and black carp do 
not currently occur within the range of the Texas pimpleback, although 
both are found in Texas and could be introduced to the Colorado and 
Guadalupe Rivers in the forseeable future. Their introduction into the 
range of Texas pimpleback would be devastating.
    Based upon our review of the best commercial and scientific data 
available, we conclude that golden algae is an ongoing threat to the 
Texas pimpleback and other nonnative species, such as zebra mussels and 
black carp, are a potential threat to the Texas pimpleback that is 
likely to increase as these exotic species expand their occupancy 
within the range of the Texas pimpleback.
Summary of Factor E
    The effects of climate change, while difficult to quantify at this 
time, are likely to exacerbate the current and ongoing threat of 
habitat loss caused by other factors, and the small sizes and 
fragmented nature of the remaining populations render them more 
vulnerable to extirpation. In addition, nonnative species, such as 
golden algae, currently threaten the Texas fatmucket, and the potential 
introduction of zebra mussels and black carp are potential future 
threats. Based upon our review of the best commercial and scientific 
data available, we conclude that other natural or manmade factors are 
immediate threats of moderate magnitude to the Texas pimpleback.

Finding for Texas Pimpleback

    As required by the Act, we considered the five factors in assessing 
whether the Texas pimpleback is threatened or endangered throughout all 
of its range. We examined the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by the Texas pimpleback. We reviewed the petition, information 
available in our files, and other available published and unpublished 
information, and we consulted with recognized Texas pimpleback experts 
and other Federal and State agencies.
    This status review identifies threats to the Texas pimpleback 
attributable to Factors A, D, and E. The primary threat to the species 
is from habitat destruction and modification (Factor A) from 
impoundments, which scour riverbeds, thereby removing mussel habitat, 
decrease water quality, modify stream flows, and restrict fish host 
migration and distribution of freshwater mussels. Additional threats 
under Factor A include sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. Also, most of these threats may be 
exacerbated by the current and projected effects of climate change 
(discussed under Factor E). Threats to the Texas pimpleback are not 
being adequately addressed through existing regulatory mechanisms 
(Factor D). Because of the limited distribution of this endemic species 
and its lack of mobility, these threats are likely to lead to the 
extinction of the Texas pimpleback in the foreseeable future.
    On the basis of the best scientific and commercial information 
available, we find that the petitioned action to list the Texas 
pimpleback under the Act is warranted. We will make a determination on 
the status of the species as threatened or endangered when we complete 
a proposed listing determination. When we complete a proposed listing 
determination, we will examine whether the species may be endangered or 
threatened throughout all of its range or whether the species may be 
endangered or threatened in a significant portion of its range. 
However, as explained in more detail below, an immediate proposal of a 
regulation implementing this action is precluded by higher priority 
listing actions, and progress is being made to add or remove qualified 
species from the Lists of Endangered and Threatened Wildlife and 
Plants.
    We reviewed the available information to determine if the existing 
and foreseeable threats render the Texas

[[Page 62201]]

pimpleback at risk of extinction now such that issuing an emergency 
regulation temporarily listing the species under section 4(b)(7) of the 
Act is warranted. We determined that issuing an emergency regulation 
temporarily listing the species is not warranted for the Texas 
pimpleback at this time, because we have not identified a threat or 
activity that poses a significant risk, such that losses to the species 
during the normal listing process would endanger the continued 
existence of the entire species. However, if at any time we determine 
that issuing an emergency regulation temporarily listing the Texas 
pimpleback is warranted, we will initiate this action at that time.

Listing Priority Number for Texas Pimpleback

    The Service adopted guidelines on September 21, 1983 (48 FR 43098), 
to establish a rational system for utilizing available resources for 
the highest priority species when adding species to the Lists of 
Endangered and Threatened Wildlife and Plants or reclassifying species 
listed as threatened to endangered status. These guidelines, titled 
``Endangered and Threatened Species Listing and Recovery Priority 
Guidelines'' address the immediacy and magnitude of threats, and the 
level of taxonomic distinctiveness by assigning priority in descending 
order to monotypic genera (genus with one species), full species, and 
subspecies (or equivalently, distinct population segments of 
vertebrates).
    As a result of our analysis of the best available scientific and 
commercial information, we have assigned the Texas pimpleback an LPN of 
2, based on our finding that the species faces threats that are of high 
magnitude and are imminent. These threats include habitat loss and 
degradation from impoundments, sedimentation, sand and gravel mining, 
and chemical contaminants; other natural or manmade factors such as 
climate change, small, isolated populations, and nonnative species; and 
the fact that the threats to the species are not being adequately 
addressed by existing regulatory mechanisms. Our rationale for 
assigning the Texas pimpleback an LPN of 2 is outlined below.
    We consider the threats that the Texas pimpleback faces to be high 
in magnitude. Habitat loss and degradation from impoundments, 
sedimentation, sand and gravel mining, and chemical contaminants are 
widespread throughout the range of the Texas pimpleback and profoundly 
affect its habitat, and remaining populations are small, isolated, and 
highly vulnerable to stochastic events.
    Under our LPN guidelines, the second criterion we consider in 
assigning a listing priority is the immediacy of threats. We consider 
the threats to the Texas pimpleback as described under Factors A, D, 
and E in the Five-Factor Evaluation for Texas Pimpleback section to be 
imminent because these threats are ongoing and will continue in the 
foreseeable future. Habitat loss and destruction has already occurred 
and will continue as the human population continues to grow in central 
Texas. The Texas pimpleback populations may already be below the 
minimum viable population requirement, which would cause a reduction in 
the number of populations and an increase in the species' vulnerability 
to extinction. These threats are exacerbated by climate change, which 
will increase the frequency and magnitude of droughts. Therefore, we 
consider these threats to be imminent.
    Thirdly, the Texas pimpleback is a valid taxon at the species level 
and, therefore, receives a higher priority than subspecies, but a lower 
priority than species in a monotypic genus. Therefore, we assigned 
Texas pimpleback an LPN of 2. We will continue to monitor the threats 
to the Texas pimpleback and the species' status on an annual basis, and 
should the magnitude or imminence of the threats change, we will 
revisit our assessment of the LPN.
    While we conclude that listing the Texas pimpleback is warranted, 
an immediate proposal to list this species is precluded by other higher 
priority listings, which we address in the Preclusion and Expeditious 
Progress section below. Because we have assigned the Texas pimpleback 
an LPN of 2, work on a proposed listing determination for the species 
is precluded by work on higher priority listing actions with absolute 
statutory, court-ordered, or court-approved deadlines and final listing 
determinations for those species that were proposed for listing with 
funds from Fiscal Year (FY) 2010. This work includes all the actions 
listed in the tables below under Preclusion and Expeditious Progress.

Five-Factor Evaluation for Texas Fawnsfoot

    Information pertaining to the Texas fawnsfoot in relation to the 
five factors provided in section 4(a)(1) of the Act is discussed below.
    Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range.
    As discussed above, the decline of mussels in Texas and across the 
United States is primarily the result of habitat loss and degradation. 
Chief among the causes of decline of the Texas fawnsfoot in Texas are 
the effects of impoundments, sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. These threats are discussed below.
Impoundments
    For general information on the effects of impoundments on 
freshwater mussels, please refer to ``Impoundments'' in Factor A under 
Five-Factor Evaluation for Texas Fatmucket. Impoundments and numerous 
smaller dams occur throughout the Colorado and Guadalupe River basins, 
fragmenting habitat and populations of Texas fawnsfoot. There are 74 
major reservoirs and numerous smaller impoundments within the 
historical and current range of the smooth pimpleback. Thirty-one of 
the 74 major reservoirs are located within the Colorado River basin and 
the remaining 43 reservoirs are located within the Brazos River basin. 
There are also eleven new reservoirs that have been recommended for 
development as feasible alternatives to meet future water needs within 
the Brazos River basin (Brazos G Regional Water Planning Group 2010, p. 
4B.12-1). In addition, six new off-channel reservoirs are also being 
considered for future development (Brazos G Regional Water Planning 
Group 2010, p. 4B.13-2).
    There are no natural lakes within the range of the Texas fawnsfoot, 
nor has it ever been found in reservoirs. Surveys of the reservoirs on 
the Brazos and Colorado Rivers have been ongoing since at least 1992, 
and no evidence of live or dead Texas pimpleback has been found in any 
reservoir (Howells 1994, pp. 1-20; 1995, pp. 1-50; 1996, pp. 1-45; 
1997a, pp. 1-58; 1998, pp. 1-30; 1999, pp. 1-34; 2000a, pp. 1-56; 2001, 
pp. 1-50; 2002a, pp. 1-28; 2003, pp. 1-42; 2004, pp. 1-48; 2005, pp. 1-
23; 2006, pp. 1-106; Karatayev and Burlakova 2008, pp. 1-47; Burlakova 
and Karatayev 2010a, pp. 1-30; 2011, pp. 1-8), further indicating that 
this species is not tolerant of impoundments.
    Texas fawnsfoot populations downstream of dams are affected as 
well. Cold water (less than 11 [deg]C (52 [deg]F)) has been shown to 
stunt mussel growth (Hanson et al. 1988, p. 352) and reduce or inhibit 
reproduction, because mussel reproduction is temperature dependent 
(Watters and O'Dee 1999, pp. 455). Texas fawnsfoot living in cold-water 
discharges downstream of large

[[Page 62202]]

impoundments are unlikely to reproduce (Watters 2000, p. 264).
    Dam construction also fragments the range of Texas fawnsfoot, 
leaving remaining habitats and populations isolated by the structures 
as well as by extensive areas of deep, uninhabitable, impounded waters. 
These isolated populations are unable to naturally recolonize suitable 
habitat that may be impacted by temporary but devastating events, such 
as severe drought, chemical spills, or unauthorized discharges. Dams 
impound river habitats throughout almost the entire range of the 
species. These impoundments have left short and isolated patches of 
remnant habitat, typically in between impounded reaches. Habitat 
downstream of dams may be impaired for many miles; in the Brazos River 
downstream of Possum Kingdom Reservoir, substrate was unstable for 150 
km (240 mi) below the dam (Yeager 1993, p. 68).
    The widespread construction of dams throughout the range of Texas 
fawnsfoot has significantly altered stream habitat both upstream and 
downstream of the dams by changing fish assemblages, temperature, 
dissolved oxygen, and substrate. The effects of dams are ongoing 
decades after construction. Because of this loss of habitat and its 
effects on the populations, we conclude that the effects of dams are a 
threat to the Texas fawnsfoot.
Sedimentation
    For general information on the effects of sedimentation on 
freshwater mussels, please refer to ``Sedimentation'' in Factor A under 
Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussel species, the Texas fawnsfoot is 
also threatened by sedimentation. The dominant land use in the Colorado 
River basin is grazing (Hersh 2007, p. 11); soil compaction from 
intensive grazing may reduce infiltration rates and increase runoff, 
and trampling of riparian vegetation increases the probability of 
erosion (Armour et al. 1994, p. 10; Brim Box and Mossa 1999, p. 103). 
Additionally, much of the Brazos River basin is grazed or farmed for 
row crops, which can contribute large amounts of sediment to the basin 
(Brazos River Authority 2007, p. 4). Reservoir construction in the 
upper portion of the basin has been attributed with the erosion and 
subsequent sedimentation of the lower river (USGS 2001, p. 30), as 
sediment-poor tailwaters scour the riverbanks below the dam and deposit 
sediment farther downstream. In 2004, sedimentation was high enough in 
the Brazos River below Possum Kingdom Reservoir to cause residents to 
raise concerns to the Brazos River Authority (Brazos River Authority 
2006, p. 2). Elevated suspended sediment levels have been reported 
throughout the basin (Brazos River Authority 2006, p. 8).
    The LCRA TSC is proposing to construct two new 345-kV electric 
transmission line facilities between Tom Green (in the Colorado River 
basin near San Angelo) and Kendall Counties (in the Guadalupe River 
basin north of San Antonio) to provide electrical power to accommodate 
increased demand (Clary 2010, p. 1). One of the proposed project lines 
would cross the San Saba River, which contains one of the more numerous 
Texas fawnsfoot populations. The proposed project could negatively 
affect Texas fawnsfoot habitat by clearing land within the riparian 
zone and may increase sediment runoff into the San Saba River (Clary 
2010, p. 9). Similar activities to accommodate Texas population growth 
and demands are expected to be undertaken across the species' range and 
will likely lead to additional sources of sediment in the streams 
inhabited by the Texas fawnsfoot.
    The City of Austin lies within the Colorado River basin, and 3.9 
million people live within the Brazos River basin (Brazos River 
Authority 2007, p. 1). The range of the Texas fawnsfoot receives 
sediment from agriculture, urbanization, and sand and gravel mining. 
Sedimentation will continue to threaten the Texas fawnsfoot in the 
foreseeable future.
Dewatering
    River dewatering can occur in several ways: anthropogenic 
activities such as surface water diversions and groundwater pumping, 
and natural events, such as drought, which can result in mussels 
stranded in previously wetted areas. This is a particular concern below 
reservoirs, whose water levels are managed for various purposes that 
can cause water levels in the reservoir or downstream to rise or fall 
in very short periods of time, such as when hydropower facilities 
release water during peak energy demand periods.
    Drought can also severely impact Texas fawnsfoot populations. 
Central Texas, including the Colorado and Brazos River basins, 
experienced a major drought in the late 1970s (Lewis and Oliveria 1979, 
p. 243). Near record dry conditions in 2008 followed by a pattern of 
below-normal rainfall during the winter and spring of 2009 led to one 
of the worst droughts in recorded history for most of central Texas, 
including the range of the Texas fawnsfoot (Nielsen-Gammon and 
McRoberts 2009, p. 2). This drought's severity was exacerbated by 
abnormally high air temperatures, a likely effect of climate change, 
which has already increased average air temperatures in Texas by at 
least 1 [deg]C (1.8 [deg]F) (Nielsen-Gammon and McRoberts 2009, p. 22). 
Instream flows throughout the Colorado River basin during this drought 
were significantly reduced (USGS 2011c, p. 1), and Texas fawnsfoot 
populations in areas with reduced water levels may have been negatively 
affected. Central Texas is currently experiencing another extreme 
drought, with rainfall between October 2010 and July 2011 being the 
lowest on record during those months (LCRA 2011c, p. 1); the effects of 
this drought are being observed but are not yet fully known. Droughts 
result in a decrease in water depth and flow velocity, which reduces 
food and oxygen delivery. As droughts persist, mussels face hypoxia, 
elevated water temperature and, ultimately, stranding (Golladay et al. 
2004, p. 501).
    We do not know the extent of the impacts of stream dewatering on 
the Texas fawnsfoot; however, because several populations are small and 
isolated, the loss of numerous individuals at a site can have dramatic 
consequences to the population. Hydropower facilities, construction, 
and drought are occurring throughout the range of the Texas fawnsfoot; 
therefore, the effects of dewatering are ongoing and unlikely to 
decrease, resulting in significant threats to the Texas fawnsfoot.
Sand and Gravel Mining
    For general information on the effects of sand and gravel mining on 
freshwater mussels, please refer to ``Sand and Gravel Mining'' in 
Factor A under Five-Factor Evaluation for Texas Fatmucket.
    The Brazos River has a long history of sand mining, particularly in 
the lower river, and channel morphology changes have been attributed to 
destabilization due to instream sand mining in the area (USGS 2001, p. 
27). The removal of sand from within the river creates sediment traps 
during periods of high flow, which causes scouring and erosion 
downstream (USGS 2001, p. 27). A gravel dredging operation in the 
Brazos River has been documented as depositing sediment as far as 1.6 
km (1 mile) downstream (Forshage and Carter 1973, p. 697). Accelerated 
stream bank erosion and downcutting of streambeds are common effects of 
instream sand and gravel mining, as is the mobilization of fine 
sediments during sand and gravel extraction (Roell 1999, p. 7).

[[Page 62203]]

    Within the current range of Texas fawnsfoot, TPWD has issued 
permits for four sand mining activities in the Brazos River basin 
(Austin, Bosque, and Fort Bend Counties) (TPWD 2004, p. 1; 2007b, p. 1; 
2008b, p. 1; 2010b, p. 1). All of the permits allow for the repeated 
removal of sand and gravel at various locations within a stream. The 
lower Brazos River, near where these mining activities are occurring, 
contains a small Texas fawnsfoot population.
    The Texas fawnsfoot population in the lower Brazos River is likely 
threatened by sand and gravel mining. These activities occur over a 
long period of time, destabilizing habitat both upstream and 
downstream, which decreases the likelihood of recolonization after the 
activity has been completed. Therefore, the effects of sand and gravel 
mining are an ongoing threat to the Texas fawnsfoot.
Chemical Contaminants
    For general information on the effects of chemical contaminants on 
freshwater mussels, please refer to ``Chemical Contaminants'' under 
Factor A under Five-Factor Evaluation for Texas Fatmucket.
    As with other freshwater mussels, the Texas fawnsfoot is also 
affected by chemical contaminants. TCEQ data for 2010 indicated that 26 
of the 98 assessed water bodies within Colorado River basin and 81 of 
approximately 124 assessed water bodies within Brazos River basin did 
not meet surface water quality standards and were classified as 303(d) 
impaired Water Bodies (Texas Clean Rivers Program 2010a, p. 5; TCEQ 
2010c, pp. 1-106). These water bodies were impaired with dissolved 
solids, nitrites, nitrates, bacteria, low dissolved oxygen, aluminum, 
sulfates, selenium, chloride, orthophosphorus, phosphorus, Chlorophyll 
a, and low pH associated with agricultural, urban, municipal, and 
industrial runoff. Of these, nitrates and low dissolved oxygen pose a 
threat to Texas fawnsfoot, as discussed above.
    In 2010, crude oil overflowed into Keechi Creek in Leon County, a 
tributary to Navasota River (National Response Center 2010, p. 2). This 
location is upstream of one of the few remaining Texas fawnsfoot 
populations. Numerous other spills have occurred within the range of 
the Texas fawnsfoot. These can occur from on site accidents (tank, 
pipeline spills) or from tanker truck accidents within watersheds 
occupied by Texas fawnsfoot. For example, oil has spilled into the 
Brazos River a number of times. As much as 320,000 L (84,000 gal) of 
crude oil was spilled in the Brazos River in 1991 (Associated Press 
1991, p. 1). In June 2010, flooding of holding ponds adjacent to oil 
drilling operations leaked oil into Thompson Creek and subsequently 
into the Brazos River. Also, in July 2010, oil pipelines burst and 
released approximately 165 barrels of crude oil into the upper Brazos 
River (Joiner 2010, p. 1).
    Agricultural pesticides and emerging contaminants are likely also 
present in streams inhabited by Texas fawnsfoot. There are 53 
wastewater treatment plants permitted to discharge into the Brazos 
River basin (Valenti and Brooks 2008, p. 12); the outfalls from these 
treatment plants have not been tested to determine if they contain 
contaminants of note.
    Chemical contaminants, such as oil, ammonia, copper, mercury, 
nutrients, pesticides, and other compounds are currently a threat to 
the Texas fawnsfoot. The species is vulnerable to acute contamination 
from spills as well as chronic contaminant exposure, which is occurring 
rangewide.
Summary of Factor A
    The reduction in numbers and range of the Texas fawnsfoot is 
primarily the result of the long-lasting effects of habitat alterations 
such as the effects of impoundments, sedimentation, sand and gravel 
mining, and chemical contaminants. Impoundments occur throughout the 
range of the species and have far-reaching effects both up- and 
downstream. Both the Colorado and Brazos River systems have experienced 
a large amount of sedimentation from agriculture, sand and gravel 
mining, and urban development. Sand and gravel mining affects Texas 
fawnsfoot habitat by increasing sedimentation and channel instability 
downstream and causing headcutting upstream. Chemical contaminants have 
been documented throughout the range of the species and may represent a 
significant threat to the Texas fawnsfoot. Based upon our review of the 
best commercial and scientific data available, we conclude that the 
present or threatened destruction, modification, or curtailment of its 
habitat or range is an immediate and ongoing threat of high magnitude 
to the Texas fawnsfoot.
    Factor B. Overutilization for Commercial, Recreational, Scientific, 
or Educational Purposes.
    The Texas fawnsfoot is not a commercially valuable species and has 
never been harvested in Texas as a commercial mussel species (Howells 
2010d, pp. 9-10). Some scientific collecting occurs but is not likely 
to be a significant threat to the species because it occurs only 
rarely. However, handling mussels can disturb gravid females and result 
in glochidial loss and subsequent reproductive failure. Additionally, 
handling has been shown to reduce shell growth across mussel species, 
including several species of Lampsilis (Haag and Commens-Carson 2008, 
pp. 505-506). Repeated handling by researchers may adversely affect 
Texas fawnsfoot individuals, but these activities are occurring rarely 
and are not likely to be a threat to populations. Handling for 
scientific purposes contributes to the long-term conservation of the 
species.
    We do not have any evidence of risks to the Texas fawnsfoot from 
overutilization for commercial, recreational, scientific, or 
educational purposes, and we have no reason to believe this factor will 
become a threat to the species in the future. Based upon the best 
scientific and commercial information available, we conclude that 
overutilization for commercial, recreational, scientific, or 
educational purposes does not pose a significant threat to the Texas 
fawnsfoot rangewide.
    Factor C. Disease and Predation.
Disease
    Little is known about disease in freshwater mussels. However, 
disease is believed to be a contributing factor in documented mussel 
die-offs in other parts of the United States (Neves 1987, pp. 11-12). 
Diseases have not been documented or observed during any studies of 
Texas fawnsfoot.
Predation
    Raccoons will prey on freshwater mussels stranded by low waters or 
deposited in shallow water or on bars following flooding or low water 
periods (Howells 2010c, p. 12). Predation of Texas fawnsfoot by 
raccoons may be occurring occasionally but there is no indication it is 
a significant threat to the status of the species.
    Some species of fish feed on mussels, such as common carp, 
freshwater drum, and redear sunfish, all of which are common throughout 
the range of Texas fawnsfoot (Hubbs et al. 2008, pp. 19, 45, 53). 
Common species of flatworms are voracious predators of newly 
metamorphosed juvenile mussels of many species (Zimmerman et al. 2003, 
p. 30). Predation is a normal factor influencing the population 
dynamics of a healthy mussel population; however, predation may amplify 
declines in small populations primarily caused by other factors.
Summary of Factor C
    Disease in freshwater mussels is poorly known, and we do not have 
any information indicating it is a threat to

[[Page 62204]]

the Texas fawnsfoot. Additionally, predation is a natural ecological 
interaction and we have no information indicating the extent of any 
predation is a threat to populations of Texas fawnsfoot. Based upon the 
best scientific and commercial information available, we conclude that 
disease or predation is not a threat to the Texas fawnsfoot.
    Factor D. The Inadequacy of Existing Regulatory Mechanisms.
    Existing regulatory mechanisms that could have an effect on threats 
to the Texas fawnsfoot include State and Federal laws such as Texas 
Threatened and Endangered Species regulations and freshwater mussel 
sanctuaries, State and Federal sand and gravel mining regulations, and 
regulation of point and non-point source pollution. For more 
information on the effects of State and Federal laws on the threats to 
freshwater mussels in central Texas, please refer to Factor D under 
Five-Factor Evaluation for Texas Fatmucket.
Summary of Factor D
    Despite State and Federal laws protecting the species and water 
quality, the Texas fawnsfoot continues to decline due to the effects of 
habitat destruction, poor water quality, contaminants, and other 
factors. The regulatory measures described in Factor D under Five-
Factor Evaluation for Texas Fatmucket have been insufficient to 
significantly reduce or remove the threats to the Texas fawnsfoot. 
Based upon our review of the best commercial and scientific data 
available, we conclude that the lack of existing regulatory mechanisms 
is an immediate threat of moderate magnitude to the Texas fawnsfoot.
    Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence.
    Natural and manmade factors that threaten the Texas fawnsfoot 
include climate change, population fragmentation and isolation, and 
nonnative species.
Climate Change
    For general information on the effects of climate change on 
freshwater mussels in central Texas, please refer to ``Climate Change'' 
in Factor E under Five-Factor Evaluation for Texas Fatmucket. Because 
the range of the Texas fawnsfoot has been reduced to isolated 
locations, many with low population numbers, in small rivers and 
streams, the Texas fawnsfoot is vulnerable to climatic changes that 
could decrease the availability of water.
    The disjunct nature of the remaining Texas fawnsfoot populations, 
coupled with the limited ability of mussels to migrate, makes it 
unlikely that Texas fawnsfoot can adjust their range in response to 
changes in climate (Strayer 2008, p. 30). Climate change could affect 
the Texas fawnsfoot through the combined effects of global and regional 
climate change, along with the increased probability of long-term 
drought. Climate change exacerbates threats such as habitat degradation 
from prolonged periods of drought, increased water temperature, and the 
increased allocation of water for municipal, agricultural, and 
industrial use. Climate change may be a significant stressor that 
exacerbates existing threats by increasing the likelihood of prolonged 
drought. As such, climate change, in and of itself, may affect the 
Texas fawnsfoot, but the magnitude and imminence of the effects remain 
uncertain. Based upon our review of the best commercial and scientific 
data available, we conclude that the effects of climate change in the 
future will likely exacerbate the current and ongoing threats of 
habitat loss and degradation caused by other factors, as discussed 
above.
Population Fragmentation and Isolation
    For general information on the effects of population fragmentation 
and isolation on freshwater mussels in central Texas, please refer to 
``Population Fragmentation and Isolation'' in Factor E under Five-
Factor Evaluation for Texas Fatmucket. As with many freshwater mussels, 
most of the remaining populations of the Texas fawnsfoot are small and 
geographically isolated and thus are susceptible to genetic drift, 
inbreeding depression, and random or chance changes to the environment, 
such as toxic chemical spills (Watters and Dunn 1995, pp. 257-258) or 
dewatering. Historically, the Texas fawnsfoot was once widespread 
throughout much of the Colorado and Brazos River systems when few 
natural barriers existed to prevent migration (via host species) among 
suitable habitats. The extensive impoundment of the Colorado and Brazos 
River basins has fragmented Texas fawnsfoot populations throughout 
these river systems.
    Small Texas fawnsfoot populations, including those in the Brazos 
River, Clear Fork Brazos River, Navasota River, and Deer Creek, may be 
below the minimum population size required to maintain population 
viability into the future. These populations are more vulnerable to 
extirpation since they are less likely to be able to recover through 
recruitment from events that reduce but do not extirpate populations. 
Additionally, these small populations are more vulnerable to 
extirpation from stochastic events, as the lack of connectivity among 
populations does not permit nearby populations to recolonize areas 
affected by intense droughts, toxic spills, or other isolated events 
that result in significant mussel dieoffs. While the small, isolated 
populations do not represent an independent threat to the species, the 
situation does substantially increase the risk of extirpation from the 
effects of all other threats, including those addressed in this 
analysis, and those that could occur in the future from unknown 
sources.
    Based upon our review of the best commercial and scientific data 
available, we conclude that fragmentation and isolation of small 
remaining populations of the Texas fawnsfoot are occurring and are 
ongoing threats to the species throughout all of its range; these 
threats will continue. Further, stochastic events may play a magnified 
role in extirpation of small, isolated populations.
Nonnative Species
    For general information on the effects of nonnative species on 
freshwater mussels in central Texas, please refer to ``Nonnative 
Species'' in Factor E under Five-Factor Evaluation for Texas Fatmucket. 
As with other freshwater mussels, the Texas fawnsfoot is threatened by 
nonnative species. Various nonnative aquatic species pose a threat to 
the Texas fawnsfoot, including golden algae, zebra mussels, and black 
carp. Of these, golden algae has been responsible for killing more than 
two million fish in the Colorado River since 1989 (TPWD 2010a, p. 1). 
Although mussel kills due to golden algae have not been recorded, we 
expect golden algae to negatively affect mussel populations through 
loss of host fish and direct toxicity. Zebra mussels and black carp do 
not currently occur within the range of the Texas fawnsfoot, although 
both are found in Texas and could be introduced to the Brazos and 
Colorado Rivers in the future. Based on population responses of other 
mussel species that overlap with zebra mussels and black carp in 
similar river conditions, we conclude that the introduction of zebra 
mussels or black carp into the range of smooth pimpleback would be 
devastating to the species.
    Based upon our review of the best commercial and scientific data 
available, we conclude that golden algae is an ongoing threat to the 
Texas fawnsfoot, and other nonnative species, such as zebra mussels and 
black carp,

[[Page 62205]]

are a potential threat to the Texas fawnsfoot that is likely to 
increase as these exotic species expand their occupancy within the 
range of the Texas fawnsfoot.
Summary of Factor E
    The effects of climate change, while difficult to quantify at this 
time, are likely to exacerbate the current and ongoing threat of 
habitat loss caused by other factors, and the small sizes and 
fragmented nature of the remaining populations render them more 
vulnerable to extirpation. In addition, nonnative species, such as 
golden algae, currently threaten the Texas fatmucket, and the potential 
introduction of zebra mussels and black carp are potential future 
threats. Based upon our review of the best commercial and scientific 
data available, we conclude that other natural or manmade factors are 
immediate threats of moderate magnitude to the Texas fawnsfoot.

Finding for Texas Fawnsfoot

    As required by the Act, we considered the five factors in assessing 
whether the Texas fawnsfoot is threatened or endangered throughout all 
of its range. We examined the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by the Texas fawnsfoot. We reviewed the petition, information 
available in our files, and other available published and unpublished 
information, and we consulted with recognized Texas fawnsfoot experts 
and other Federal and State agencies.
    This status review identifies threats to the Texas fawnsfoot 
attributable to Factors A, D, and E. The primary threat to the species 
is from habitat destruction and modification (Factor A) from 
impoundments, which scour riverbeds, thereby removing mussel habitat, 
decrease water quality, modify stream flows, and restrict fish host 
migration and distribution of freshwater mussels. Additional threats 
under Factor A include sedimentation, dewatering, sand and gravel 
mining, and chemical contaminants. Also, most of these threats may be 
exacerbated by the current and projected effects of climate change 
(discussed under Factor E). Threats to the Texas fawnsfoot are not 
being adequately addressed through existing regulatory mechanisms 
(Factor D). Because of the limited distribution of this endemic species 
and its lack of mobility, these threats are likely to lead to the 
extinction of the Texas fawnsfoot in the foreseeable future.
    On the basis of the best scientific and commercial information 
available, we find that the petitioned action to list the Texas 
fawnsfoot under the Act is warranted. We will make a determination on 
the status of the species as threatened or endangered when we complete 
a proposed listing determination. When we complete a proposed listing 
determination, we will examine whether the species may be endangered or 
threatened throughout all of its range or whether the species may be 
endangered or threatened in a significant portion of its range. 
However, as explained in more detail below, an immediate proposal of a 
regulation implementing this action is precluded by higher priority 
listing actions, and progress is being made to add or remove qualified 
species from the Lists of Endangered and Threatened Wildlife and 
Plants.
    We reviewed the available information to determine if the existing 
and foreseeable threats render the Texas fawnsfoot at risk of 
extinction now such that issuing an emergency regulation temporarily 
listing the species under section 4(b)(7) of the Act is warranted. We 
determined that issuing an emergency regulation temporarily listing the 
species is not warranted for the Texas fawnsfoot at this time, because 
we have not identified a threat or activity that poses a significant 
risk, such that losses to the species during the normal listing process 
would endanger the continued existence of the entire species. However, 
if at any time we determine that issuing an emergency regulation 
temporarily listing the Texas fawnsfoot is warranted, we will initiate 
this action at that time.

Listing Priority Number for Texas Fawnsfoot

    The Service adopted guidelines on September 21, 1983 (48 FR 43098), 
to establish a rational system for utilizing available resources for 
the highest priority species when adding species to the Lists of 
Endangered and Threatened Wildlife and Plants or reclassifying species 
listed as threatened to endangered status. These guidelines, titled 
``Endangered and Threatened Species Listing and Recovery Priority 
Guidelines'' address the immediacy and magnitude of threats, and the 
level of taxonomic distinctiveness by assigning priority in descending 
order to monotypic genera (genus with one species), full species, and 
subspecies (or equivalently, distinct population segments of 
vertebrates).
    As a result of our analysis of the best available scientific and 
commercial information, we have assigned the Texas fawnsfoot an LPN of 
2, based on our finding that the species faces threats that are of high 
magnitude and are imminent. These threats include habitat loss and 
degradation from impoundments, sedimentation, sand and gravel mining, 
and chemical contaminants; other natural or manmade factors such as 
climate change, small, isolated populations, and nonnative species; and 
the fact that the threats to the species are not being adequately 
addressed by existing regulatory mechanisms. Our rationale for 
assigning the Texas fawnsfoot an LPN of 2 is outlined below.
    We consider the threats that the Texas fawnsfoot faces to be high 
in magnitude. Habitat loss and degradation from impoundments, 
sedimentation, sand and gravel mining, and chemical contaminants are 
widespread throughout the range of the Texas fawnsfoot and profoundly 
affect its habitat. Remaining populations are small, isolated, and 
highly vulnerable to stochastic events.
    Under our LPN guidelines, the second criterion we consider in 
assigning a listing priority is the immediacy of threats. We consider 
the threats to the Texas fawnsfoot as described under Factors A, D, and 
E in the Five-Factor Evaluation for Texas Fawnsfoot section to be 
imminent because these threats are ongoing and will continue in the 
foreseeable future. Habitat loss and destruction has already occurred 
and will continue as the human population continues to grow in central 
Texas. The Texas fawnsfoot populations may already be below the minimum 
viable population requirement, which would cause a reduction in the 
number of populations and an increase in the species' vulnerability to 
extinction. These threats are exacerbated by climate change, which will 
increase the frequency and magnitude of droughts. Therefore, we 
consider these threats to be imminent.
    Thirdly, the Texas fawnsfoot is a valid taxon at the species level 
and, therefore, receives a higher priority than subspecies, but a lower 
priority than species in a monotypic genus. Therefore, we assigned 
Texas fawnsfoot an LPN of 2. We will continue to monitor the threats to 
the Texas fawnsfoot and the species' status on an annual basis, and 
should the magnitude or imminence of the threats change, we will 
revisit our assessment of the LPN.
    While we conclude that listing the Texas fawnsfoot is warranted, an 
immediate proposal to list this species is precluded by other higher 
priority listings, which we address in the Preclusion and Expeditious 
Progress section below. Because we have assigned the Texas fawnsfoot an 
LPN of 2, work on a proposed listing

[[Page 62206]]

determination for the species is precluded by work on higher priority 
listing actions with absolute statutory, court-ordered, or court-
approved deadlines and final listing determinations for those species 
that were proposed for listing with funds from Fiscal Year (FY) 2011. 
This work includes all the actions listed in the tables below under 
Preclusion and Expeditious Progress.

Preclusion and Expeditious Progress

    Preclusion is a function of the listing priority of a species in 
relation to the resources that are available and the cost and relative 
priority of competing demands for those resources. Thus, in any given 
fiscal year (FY), multiple factors dictate whether it will be possible 
to undertake work on a listing proposal regulation or whether 
promulgation of such a proposal is precluded by higher priority listing 
actions.
    The resources available for listing actions are determined through 
the annual Congressional appropriations process. The appropriation for 
the Listing Program is available to support work involving the 
following listing actions: Proposed and final listing rules; 90-day and 
12-month findings on petitions to add species to the Lists of 
Endangered and Threatened Wildlife and Plants (Lists) or to change the 
status of a species from threatened to endangered; annual 
``resubmitted'' petition findings on prior warranted-but-precluded 
petition findings as required under section 4(b)(3)(C)(i) of the Act; 
critical habitat petition findings; proposed and final rules 
designating critical habitat; and litigation-related, administrative, 
and program-management functions (including preparing and allocating 
budgets, responding to Congressional and public inquiries, and 
conducting public outreach regarding listing and critical habitat). The 
work involved in preparing various listing documents can be extensive 
and may include, but is not limited to: Gathering and assessing the 
best scientific and commercial data available and conducting analyses 
used as the basis for our decisions; writing and publishing documents; 
and obtaining, reviewing, and evaluating public comments and peer 
review comments on proposed rules and incorporating relevant 
information into final rules. The number of listing actions that we can 
undertake in a given year also is influenced by the complexity of those 
listing actions; that is, more complex actions generally are more 
costly. The median cost for preparing and publishing a 90-day finding 
is $39,276; for a 12-month finding, $100,690; for a proposed rule with 
critical habitat, $345,000; and for a final listing rule with critical 
habitat, $305,000.
    We cannot spend more than is appropriated for the Listing Program 
without violating the Anti-Deficiency Act (see 31 U.S.C. 
1341(a)(1)(A)). In addition, in FY 1998 and for each fiscal year since 
then, Congress has placed a statutory cap on funds that may be expended 
for the Listing Program, equal to the amount expressly appropriated for 
that purpose in that fiscal year. This cap was designed to prevent 
funds appropriated for other functions under the Act (for example, 
recovery funds for removing species from the Lists), or for other 
Service programs, from being used for Listing Program actions (see 
House Report 105-163, 105th Congress, 1st Session, July 1, 1997).
    Since FY 2002, the Service's budget has included a critical habitat 
subcap to ensure that some funds are available for other work in the 
Listing Program (``The critical habitat designation subcap will ensure 
that some funding is available to address other listing activities'' 
(House Report No. 107-103, 107th Congress, 1st Session, June 19, 
2001)). In FY 2002 and each year until FY 2006, the Service has had to 
use virtually the entire critical habitat subcap to address court-
mandated designations of critical habitat, and consequently none of the 
critical habitat subcap funds have been available for other listing 
activities. In some FYs since 2006, we have been able to use some of 
the critical habitat subcap funds to fund proposed listing 
determinations for high-priority candidate species. In other FYs, while 
we were unable to use any of the critical habitat subcap funds to fund 
proposed listing determinations, we did use some of this money to fund 
the critical habitat portion of some proposed listing determinations so 
that the proposed listing determination and proposed critical habitat 
designation could be combined into one rule, thereby being more 
efficient in our work. At this time, for FY 2011, we plan to use some 
of the critical habitat subcap funds to fund proposed listing 
determinations.
    We make our determinations of preclusion on a nationwide basis to 
ensure that the species most in need of listing will be addressed first 
and also because we allocate our listing budget on a nationwide basis. 
Through the listing cap, the critical habitat subcap, and the amount of 
funds needed to address court-mandated critical habitat designations, 
Congress and the courts have in effect determined the amount of money 
available for other listing activities nationwide. Therefore, the funds 
in the listing cap, other than those needed to address court-mandated 
critical habitat for already listed species, set the limits on our 
determinations of preclusion and expeditious progress.
    Congress identified the availability of resources as the only basis 
for deferring the initiation of a rulemaking that is warranted. The 
Conference Report accompanying Public Law 97-304 (Endangered Species 
Act Amendments of 1982), which established the current statutory 
deadlines and the warranted-but-precluded finding, states that the 
amendments were ``not intended to allow the Secretary to delay 
commencing the rulemaking process for any reason other than that the 
existence of pending or imminent proposals to list species subject to a 
greater degree of threat would make allocation of resources to such a 
petition [that is, for a lower-ranking species] unwise.'' Although that 
statement appeared to refer specifically to the ``to the maximum extent 
practicable'' limitation on the 90-day deadline for making a 
``substantial information'' finding, that finding is made at the point 
when the Service is deciding whether or not to commence a status review 
that will determine the degree of threats facing the species, and 
therefore the analysis underlying the statement is more relevant to the 
use of the warranted-but-precluded finding, which is made when the 
Service has already determined the degree of threats facing the species 
and is deciding whether or not to commence a rulemaking.
    In FY 2011, on April 15, 2011, Congress passed the Full-Year 
Continuing Appropriations Act (Pub. L. 112-10), which provides funding 
through September 30, 2011. The Service has $20,902,000 for the listing 
program. Of that, $9,472,000 is being used for determinations of 
critical habitat for already listed species. Also $500,000 is 
appropriated for foreign species listings under the Act. The Service 
thus has $10,930,000 available to fund work in the following 
categories: Compliance with court orders and court-approved settlement 
agreements requiring that petition findings or listing determinations 
be completed by a specific date; section 4 (of the Act) listing actions 
with absolute statutory deadlines; essential litigation-related, 
administrative, and listing program-management functions; and high-
priority listing actions for some of our candidate species. In FY 2010, 
the Service received many new petitions and a single petition to list 
404 species. The receipt of petitions for a large number of species is 
consuming the

[[Page 62207]]

Service's listing funding that is not dedicated to meeting court-
ordered commitments. Absent some ability to balance effort among 
listing duties under existing funding levels, the Service is only able 
to initiate a few new listing determinations for candidate species in 
FY 2011.
    In 2009, the responsibility for listing foreign species under the 
Act was transferred from the Division of Scientific Authority, 
International Affairs Program, to the Endangered Species Program. 
Therefore, starting in FY 2010, we used a portion of our funding to 
work on the actions described above for listing actions related to 
foreign species. In FY 2011, we anticipate using $1,500,000 for work on 
listing actions for foreign species, which reduces funding available 
for domestic listing actions; however, currently only $500,000 has been 
allocated for this function. Although there are no foreign species 
issues included in our high-priority listing actions at this time, many 
actions have statutory or court-approved settlement deadlines, thus 
increasing their priority. The budget allocations for each specific 
listing action are identified in the Service's FY 2011 Allocation Table 
(part of our record).
    For the above reasons, funding proposed listing determinations for 
the Texas fatmucket, golden orb, smooth pimpleback, Texas pimpleback, 
and Texas fawnsfoot is precluded by court-ordered and court-approved 
settlement agreements, listing actions with absolute statutory 
deadlines, and work on proposed listing determinations for those 
candidate species with a higher listing priority (i.e., candidate 
species with LPNs of 1).
    Based on our September 21, 1983, guidelines for assigning an LPN 
for each candidate species (48 FR 43098), we have a significant number 
of species with a LPN of 2. Using these guidelines, we assign each 
candidate an LPN of 1 to 12, depending on the magnitude of threats 
(high or moderate to low), immediacy of threats (imminent or 
nonimminent), and taxonomic status of the species (in order of 
priority: monotypic genus (a species that is the sole member of a 
genus); species; or part of a species (subspecies, or distinct 
population segment)). The lower the listing priority number, the higher 
the listing priority (that is, a species with an LPN of 1 would have 
the highest listing priority).
    Because of the large number of high-priority species, we have 
further ranked the candidate species with an LPN of 2 by using the 
following extinction-risk type criteria: International Union for the 
Conservation of Nature and Natural Resources (IUCN) Red list status/
rank, Heritage rank (provided by NatureServe), Heritage threat rank 
(provided by NatureServe), and species currently with fewer than 50 
individuals, or 4 or fewer populations. Those species with the highest 
IUCN rank (critically endangered), the highest Heritage rank (G1), the 
highest Heritage threat rank (substantial, imminent threats), and 
currently with fewer than 50 individuals, or fewer than 4 populations, 
originally comprised a group of approximately 40 candidate species 
(``Top 40''). These 40 candidate species have had the highest priority 
to receive funding to work on a proposed listing determination. As we 
work on proposed and final listing rules for those 40 candidates, we 
apply the ranking criteria to the next group of candidates with an LPN 
of 2 and 3 to determine the next set of highest priority candidate 
species. Finally, proposed rules for reclassification of threatened 
species to endangered species are lower priority, because as listed 
species, they are already afforded the protections of the Act and 
implementing regulations. However, for efficiency reasons, we may 
choose to work on a proposed rule to reclassify a species to endangered 
if we can combine this with work that is subject to a court-determined 
deadline.
    With our workload so much bigger than the amount of funds we have 
to accomplish it, it is important that we be as efficient as possible 
in our listing process. Therefore, as we work on proposed rules for the 
highest priority species in the next several years, we are preparing 
multi-species proposals when appropriate, and these may include species 
with lower priority if they overlap geographically or have the same 
threats as a species with an LPN of 2. In addition, we take into 
consideration the availability of staff resources when we determine 
which high-priority species will receive funding to minimize the amount 
of time and resources required to complete each listing action.
    As explained above, a determination that listing is warranted but 
precluded must also demonstrate that expeditious progress is being made 
to add and remove qualified species to and from the Lists of Endangered 
and Threatened Wildlife and Plants. As with our ``precluded'' finding, 
the evaluation of whether progress in adding qualified species to the 
Lists has been expeditious is a function of the resources available for 
listing and the competing demands for those funds. (Although we do not 
discuss it in detail here, we are also making expeditious progress in 
removing species from the list under the Recovery program in light of 
the resource available for delisting, which is funded by a separate 
line item in the budget of the Endangered Species Program. So far 
during FY 2011, we have completed delisting rules for three species.) 
Given the limited resources available for listing, we find that we are 
making expeditious progress in FY 2011 in the Listing Program. This 
progress included preparing and publishing the following 
determinations:

                                        FY 2011 Completed Listing Actions
----------------------------------------------------------------------------------------------------------------
      Publication date                 Title                   Actions                      FR Pages
----------------------------------------------------------------------------------------------------------------
10/6/2010...................  Endangered Status for    Proposed Listing        75 FR 61664-61690
                               the Altamaha             Endangered.
                               Spinymussel and
                               Designation of
                               Critical Habitat.
10/7/2010...................  12-Month Finding on a    Notice of 12-month      75 FR 62070-62095
                               Petition to list the     petition finding, Not
                               Sacramento Splittail     warranted.
                               as Endangered or
                               Threatened.
10/28/2010..................  Endangered Status and    Proposed Listing        75 FR 66481-66552
                               Designation of           Endangered
                               Critical Habitat for     (uplisting).
                               Spikedace and Loach
                               Minnow.
11/2/2010...................  90-Day Finding on a      Notice of 90-day        75 FR 67341-67343
                               Petition to List the     Petition Finding, Not
                               Bay Springs Salamander   substantial.
                               as Endangered.
11/2/2010...................  Determination of         Final Listing           75 FR 67511-67550
                               Endangered Status for    Endangered.
                               the Georgia Pigtoe
                               Mussel, Interrupted
                               Rocksnail, and Rough
                               Hornsnail and
                               Designation of
                               Critical Habitat.
11/2/2010...................  Listing the Rayed Bean   Proposed Listing        75 FR 67551-67583
                               and Snuffbox as          Endangered.
                               Endangered.

[[Page 62208]]

 
11/4/2010...................  12-Month Finding on a    Notice of 12-month      75 FR 67925-67944
                               Petition to List         petition finding,
                               Cirsium wrightii         Warranted but
                               (Wright's Marsh          precluded.
                               Thistle) as Endangered
                               or Threatened.
12/14/2010..................  Endangered Status for    Proposed Listing        75 FR 77801-77817
                               Dunes Sagebrush Lizard.  Endangered.
12/14/2010..................  12-Month Finding on a    Notice of 12-month      75 FR 78029-78061
                               Petition to List the     petition finding,
                               North American           Warranted but
                               Wolverine as             precluded.
                               Endangered or
                               Threatened.
12/14/2010..................  12-Month Finding on a    Notice of 12-month      75 FR 78093-78146
                               Petition to List the     petition finding,
                               Sonoran Population of    Warranted but
                               the Desert Tortoise as   precluded.
                               Endangered or
                               Threatened.
12/15/2010..................  12-Month Finding on a    Notice of 12-month      75 FR 78513-78556
                               Petition to List         petition finding,
                               Astragalus microcymbus   Warranted but
                               and Astragalus           precluded.
                               schmolliae as
                               Endangered or
                               Threatened.
12/28/2010..................  Listing Seven Brazilian  Final Listing           75 FR 81793-81815
                               Bird Species as          Endangered.
                               Endangered Throughout
                               Their Range.
1/4/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 304-311
                               Petition to List the     Petition Finding, Not
                               Red Knot subspecies      substantial.
                               Calidris canutus
                               roselaari as
                               Endangered.
1/19/2011...................  Endangered Status for    Proposed Listing        76 FR 3392-3420
                               the Sheepnose and        Endangered.
                               Spectaclecase Mussels.
2/10/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 7634-7679
                               Petition to List the     petition finding,
                               Pacific Walrus as        Warranted but
                               Endangered or            precluded.
                               Threatened.
2/17/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 9309-9318
                               Petition to List the     Petition Finding,
                               Sand Verbena Moth as     Substantial.
                               Endangered or
                               Threatened.
2/22/2011...................  Determination of         Final Listing           76 FR 9681-9692
                               Threatened Status for    Threatened.
                               the New Zealand-
                               Australia Distinct
                               Population Segment of
                               the Southern
                               Rockhopper Penguin.
2/22/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 9722-9733
                               Petition to List         petition finding,
                               Solanum conocarpum       Warranted but
                               (marron bacora) as       precluded.
                               Endangered.
2/23/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 9991-10003
                               Petition to List         petition finding, Not
                               Thorne's Hairstreak      warranted.
                               Butterfly as
                               Endangered.
2/23/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 10166-10203
                               Petition to List         petition finding,
                               Astragalus hamiltonii,   Warranted but
                               Penstemon flowersii,     precluded & Not
                               Eriogonum soredium,      Warranted.
                               Lepidium ostleri, and
                               Trifolium friscanum as
                               Endangered or
                               Threatened.
2/24/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 10299-10310
                               Petition to List the     Petition Finding, Not
                               Wild Plains Bison or     substantial.
                               Each of Four Distinct
                               Population Segments as
                               Threatened.
2/24/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 10310-10319
                               Petition to List the     Petition Finding, Not
                               Unsilvered Fritillary    substantial.
                               Butterfly as
                               Threatened or
                               Endangered.
3/8/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 12667-12683
                               Petition to List the     petition finding,
                               Mt. Charleston Blue      Warranted but
                               Butterfly as             precluded.
                               Endangered or
                               Threatened.
3/8/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 12683-12690
                               Petition to List the     Petition Finding,
                               Texas Kangaroo Rat as    Substantial.
                               Endangered or
                               Threatened.
3/10/2011...................  Initiation of Status     Notice of Status        76 FR 13121-13122
                               Review for Longfin       Review.
                               Smelt.
3/15/2011...................  Withdrawal of Proposed   Proposed rule           76 FR 14210-14268
                               Rule to List the Flat-   withdrawal.
                               tailed Horned Lizard
                               as Threatened.
3/15/2011...................  Proposed Threatened      Proposed Listing        76 FR 14126-14207
                               Status for the           Threatened; Proposed
                               Chiricahua Leopard       Designation of
                               Frog and Proposed        Critical Habitat.
                               Designation of
                               Critical Habitat.
3/22/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 15919-15932
                               Petition to List the     petition finding,
                               Berry Cave Salamander    Warranted but
                               as Endangered.           precluded.
4/1/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 18138-18143
                               Petition to List the     Petition Finding,
                               Spring Pygmy Sunfish     Substantial.
                               as Endangered.
4/5/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 18684-18701
                               Petition to List the     petition finding, Not
                               Bearmouth                Warranted and
                               Mountainsnail, Byrne     Warranted but
                               Resort Mountainsnail,    precluded.
                               and Meltwater Lednian
                               Stonefly as Endangered
                               or Threatened.
4/5/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 18701-18706
                               Petition to List the     Petition Finding,
                               Peary Caribou and        Substantial.
                               Dolphin and Union
                               population of the
                               Barren-ground Caribou
                               as Endangered or
                               Threatened.
4/12/2011...................  Proposed Endangered      Proposed Listing        76 FR 20464-20488
                               Status for the Three     Endangered; Proposed
                               Forks Springsnail and    Designation of
                               San Bernardino           Critical Habitat.
                               Springsnail, and
                               Proposed Designation
                               of Critical Habitat.
4/13/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 20613-20622
                               Petition to List         Petition Finding,
                               Spring Mountains         Substantial.
                               Acastus Checkerspot
                               Butterfly as
                               Endangered.
4/14/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 20911-20918
                               Petition to List the     Petition Finding,
                               Prairie Chub as          Substantial.
                               Threatened or
                               Endangered.
4/14/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 20918-20939
                               Petition to List         petition finding,
                               Hermes Copper            Warranted but
                               Butterfly as             precluded.
                               Endangered or
                               Threatened.
4/26/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 23256-23265
                               Petition to List the     Petition Finding,
                               Arapahoe Snowfly as      Substantial.
                               Endangered or
                               Threatened.

[[Page 62209]]

 
4/26/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 23265-23271
                               Petition to List the     Petition Finding, Not
                               Smooth-Billed Ani as     substantial.
                               Threatened or
                               Endangered.
5/12/2011...................  Withdrawal of the        Proposed Rule,          76 FR 27756-27799
                               Proposed Rule to List    Withdrawal.
                               the Mountain Plover as
                               Threatened.
5/25/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 30082-30087
                               Petition to List the     Petition Finding,
                               Spot-tailed Earless      Substantial.
                               Lizard as Endangered
                               or Threatened.
5/26/2011...................  Listing the Salmon-      Final Listing           76 FR 30758-30780
                               Crested Cockatoo as      Threatened.
                               Threatened Throughout
                               its Range with Special
                               Rule.
5/31/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 31282-31294
                               Petition to List         petition finding,
                               Puerto Rican Harlequin   Warranted but
                               Butterfly as             precluded.
                               Endangered.
6/2/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 31903-31906
                               Petition to Reclassify   Petition Finding,
                               the Straight-Horned      Substantial.
                               Markhor (Capra
                               falconeri jerdoni) of
                               Torghar Hills as
                               Threatened.
6/2/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 31920-31926
                               Petition to List the     Petition Finding,
                               Golden-winged Warbler    Substantial.
                               as Endangered or
                               Threatened.
6/7/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 32911-32929
                               Petition to List the     petition finding,
                               Striped Newt as          Warranted but
                               Threatened.              precluded.
6/9/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 33924-33965
                               Petition to List         petition finding, Not
                               Abronia ammophila,       Warranted and
                               Agrostis rossiae,        Warranted but
                               Astragalus               precluded.
                               proimanthus, Boechera
                               (Arabis) pusilla, and
                               Penstemon gibbensii as
                               Threatened or
                               Endangered.
6/21/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 36049-36053
                               Petition to List the     Petition Finding, Not
                               Utah Population of the   substantial.
                               Gila Monster as an
                               Endangered or a
                               Threatened Distinct
                               Population Segment.
6/21/2011...................  Revised 90-Day Finding   Notice of 90-day        76 FR 36053-36068
                               on a Petition to         Petition Finding, Not
                               Reclassify the Utah      substantial.
                               Prairie Dog From
                               Threatened to
                               Endangered.
6/28/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 37706-37716
                               Petition to List         petition finding, Not
                               Castanea pumila var.     warranted.
                               ozarkensis as
                               Threatened or
                               Endangered.
6/29/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 38095-38106
                               Petition to List the     Petition Finding,
                               Eastern Small-Footed     Substantial.
                               Bat and the Northern
                               Long-Eared Bat as
                               Threatened or
                               Endangered.
6/30/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 38504-38532
                               Petition to List a       petition finding, Not
                               Distinct Population      warranted.
                               Segment of the Fisher
                               in Its United States
                               Northern Rocky
                               Mountain Range as
                               Endangered or
                               Threatened with
                               Critical Habitat.
7/12/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 40868-40871
                               Petition to List the     Petition Finding,
                               Bay Skipper as           Substantial.
                               Threatened or
                               Endangered.
7/19/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 42631-42654
                               Petition to List Pinus   petition finding,
                               albicaulis as            Warranted but
                               Endangered or            precluded.
                               Threatened with
                               Critical Habitat.
7/19/2011...................  Petition to List Grand   Notice of 12-month      76 FR 42654-42658
                               Canyon Cave              petition finding, Not
                               Pseudoscorpion.          warranted.
7/26/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 44547-44564
                               Petition to List the     petition finding, Not
                               Giant Palouse            warranted.
                               Earthworm (Drilolerius
                               americanus) as
                               Threatened or
                               Endangered.
7/26/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 44566-44569
                               Petition to List the     petition finding, Not
                               Frigid Ambersnail as     warranted.
                               Endangered.
7/27/2011...................  Determination of         Final Listing           76 FR 45054-45075
                               Endangered Status for    Endangered,
                               Ipomopsis polyantha      Threatened.
                               (Pagosa Skyrocket) and
                               Threatened Status for
                               Penstemon debilis
                               (Parachute
                               Beardtongue) and
                               Phacelia submutica
                               (DeBeque Phacelia).
7/27/2011...................  12-Month Finding on a    Notice of 12-month      76 FR 45130-45162
                               Petition to List the     petition finding,
                               Gopher Tortoise as       Warranted but
                               Threatened in the        precluded.
                               Eastern Portion of its
                               Range.
8/2/2011....................  Proposed Endangered      Proposed Listing        76 FR 46218-46234
                               Status for the           Endangered.
                               Chupadera Springsnail
                               (Pyrgulopsis
                               chupaderae) and
                               Proposed Designation
                               of Critical Habitat.
8/2/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 46238-46251
                               Petition to List the     Petition Finding, Not
                               Straight Snowfly and     substantial.
                               Idaho Snowfly as
                               Endangered.
8/2/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 46251-46266
                               Petition to List the     petition finding, Not
                               Redrock Stonefly as      warranted.
                               Endangered or
                               Threatened.
8/2/2011....................  Listing 23 Species on    Proposed Listing        76 FR 46362-46594
                               Oahu as Endangered and   Endangered.
                               Designating Critical
                               Habitat for 124
                               Species.
8/4/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 47123-47133
                               Petition to List Six     Petition Finding, Not
                               Sand Dune Beetles as     substantial and
                               Endangered or            substantial.
                               Threatened.
8/9/2011....................  Endangered Status for    Final Listing           76 FR 48722-48741
                               the Cumberland Darter,   Endangered.
                               Rush Darter,
                               Yellowcheek Darter,
                               Chucky Madtom, and
                               Laurel Dace.
8/9/2011....................  12-Month Finding on a    Notice of 12-month      76 FR 48777-48788
                               Petition to List the     petition finding, Not
                               Nueces River and         warranted.
                               Plateau Shiners as
                               Threatened or
                               Endangered.

[[Page 62210]]

 
8/9/2011....................  Four Foreign Parrot      Proposed Listing        76 FR 49202-49236
                               Species [crimson         Endangered and
                               shining parrot, white    Threatened; Notice of
                               cockatoo, Philippine     12-month petition
                               cockatoo, yellow-        finding, Not
                               crested cockatoo].       warranted.
8/10/2011...................  Proposed Listing of the  Proposed Listing        76 FR 49408-49412
                               Miami Blue Butterfly     Endangered Similarity
                               as Endangered, and       of Appearance.
                               Proposed Listing of
                               the Cassius Blue,
                               Ceraunus Blue, and
                               Nickerbean Blue
                               Butterflies as
                               Threatened Due to
                               Similarity of
                               Appearance to the
                               Miami Blue Butterfly.
8/10/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 49412-49417
                               Petition to List the     Petition Finding,
                               Saltmarsh Topminnow as   Substantial.
                               Threatened or
                               Endangered Under the
                               Endangered Species Act.
8/10/2011...................  Proposed Listing of the  Proposed Listing        76 FR 49408-49412
                               Miami Blue Butterfly     Endangered and
                               as Endangered, and       Similarity of
                               Proposed Listing of      Appearance.
                               the Cassius Blue,
                               Ceraunus Blue, and
                               Nickerbean Blue
                               Butterflies as
                               Threatened Due to
                               Similarity of
                               Appearance to the
                               Miami Blue Butterfly.
8/10/2011...................  Emergency Listing of     Emergency Listing       76 FR 49542-49567
                               the Miami Blue           Endangered and
                               Butterfly as             Similarity of
                               Endangered, and          Appearance.
                               Emergency Listing of
                               the Cassius Blue,
                               Ceraunus Blue, and
                               Nickerbean Blue
                               Butterflies as
                               Threatened Due to
                               Similarity of
                               Appearance to the
                               Miami Blue Butterfly.
8/11/2011...................  Listing Six Foreign      Final Listing           76 FR 50052-50080
                               Birds as Endangered      Endangered.
                               Throughout Their Range.
8/17/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 50971-50979
                               Petition to List the     Petition Finding,
                               Leona's Little Blue      Substantial.
                               Butterfly as
                               Endangered or
                               Threatened.
9/01/2011...................  90-Day Finding on a      Notice of 90-day        76 FR 54423-54425
                               Petition to List All     Petition Finding,
                               Chimpanzees (Pan         Substantial.
                               troglodytes) as
                               Endangered.
9/6/2011....................  12-Month Finding on      Notice of 12-month      76 FR 55170-55203
                               Five Petitions to List   petition finding,
                               Seven Species of         Warranted but
                               Hawaiian Yellow-faced    precluded.
                               Bees as Endangered.
9/8/2011....................  12-Month Petition        Notice of 12-month      76 FR 55623-55638
                               Finding and Proposed     petition finding,
                               Listing of               Warranted; Proposed
                               Arctostaphylos           Listing Endangered.
                               franciscana as
                               Endangered.
9/8/2011....................  90-Day Finding on a      Notice of 90-day        76 FR 55638-55641
                               Petition to List the     Petition Finding, Not
                               Snowy Plover and         substantial.
                               Reclassify the
                               Wintering Population
                               of Piping Plover.
9/13/2011...................  90-Day Finding on a      Notice of 90-day        76 FR
                               Petition to List the     Petition Finding,
                               Franklin's Bumble Bee    Substantial.
                               as Endangered.
9/13/2011...................  90-Day Finding on a      Notice of 90-day        76 FR
                               Petition to List 42      Petition Finding,
                               Great Basin and Mojave   Substantial and Not
                               Desert Springsnails as   substantial.
                               Threatened or
                               Endangered with
                               Critical Habitat.
----------------------------------------------------------------------------------------------------------------

    Our expeditious progress also includes work on listing actions that 
we funded in FY 2010 and FY 2011 but have not yet been completed to 
date. These actions are listed below. Actions in the top section of the 
table are being conducted under a deadline set by a court. Actions in 
the middle section of the table are being conducted to meet statutory 
timelines, that is, timelines required under the Act. Actions in the 
bottom section of the table are high-priority listing actions. These 
actions include work primarily on species with an LPN of 2, and, as 
discussed above, selection of these species is partially based on 
available staff resources, and when appropriate, include species with a 
lower priority if they overlap geographically or have the same threats 
as the species with the high priority. Including these species together 
in the same proposed rule results in considerable savings in time and 
funding, when compared to preparing separate proposed rules for each of 
them in the future.

       Actions Funded in FY 2010 and FY 2011 But Not Yet Completed
------------------------------------------------------------------------
                  Species                              Action
------------------------------------------------------------------------
           Actions Subject to Court Order/Settlement Agreement
------------------------------------------------------------------------
4 parrot species (military macaw, yellow-   12-month petition finding.
 billed parrot, red-crowned parrot,
 scarlet macaw) \5\.
4 parrot species (blue-headed macaw, great  12-month petition finding.
 green macaw, grey-cheeked parakeet,
 hyacinth macaw) \5\.
Longfin smelt.............................  12-month petition finding.
------------------------------------------------------------------------
                    Actions with Statutory Deadlines
------------------------------------------------------------------------
Casey's june beetle.......................  Final listing determination.
5 Bird species from Colombia and Ecuador..  Final listing determination.
Queen Charlotte goshawk...................  Final listing determination.
Ozark hellbender \4\......................  Final listing determination.
Altamaha spinymussel \3\..................  Final listing determination.
6 Birds from Peru & Bolivia...............  Final listing determination.

[[Page 62211]]

 
Loggerhead sea turtle (assist National      Final listing determination.
 Marine Fisheries Service) \5\.
2 mussels (rayed bean (LPN = 2), snuffbox   Final listing determination.
 No LPN) \5\.
CA golden trout \4\.......................  12-month petition finding.
Black-footed albatross....................  12-month petition finding.
Mojave fringe-toed lizard \1\.............  12-month petition finding.
Kokanee--Lake Sammamish population \1\....  12-month petition finding.
Cactus ferruginous pygmy-owl \1\..........  12-month petition finding.
Northern leopard frog.....................  12-month petition finding.
Tehachapi slender salamander..............  12-month petition finding.
Coqui Llanero.............................  12-month petition finding/
                                             Proposed listing.
Dusky tree vole...........................  12-month petition finding.
Leatherside chub (from 206 species          12-month petition finding.
 petition).
Platte River caddisfly (from 206 species    12-month petition finding.
 petition) \5\.
3 Texas moths (Ursia furtiva, Sphingicampa  12-month petition finding.
 blanchardi, Agapema galbina) (from 475
 species petition).
3 South Arizona plants (Erigeron            12-month petition finding.
 piscaticus, Astragalus hypoxylus,
 Amoreuxia gonzalezii) (from 475 species
 petition).
14 parrots (foreign species)..............  12-month petition finding.
Mohave Ground Squirrel \1\................  12-month petition finding.
Western gull-billed tern..................  12-month petition finding.
OK grass pink (Calopogon oklahomensis) \1\  12-month petition finding.
Ashy storm-petrel \5\.....................  12-month petition finding.
Honduran emerald..........................  12-month petition finding.
Eagle Lake trout \1\......................  90-day petition finding.
32 Pacific Northwest mollusks species       90-day petition finding.
 (snails and slugs) \1\.
Spring Mountains checkerspot butterfly....  90-day petition finding.
10 species of Great Basin butterfly.......  90-day petition finding.
404 Southeast species.....................  90-day petition finding.
American eel \4\..........................  90-day petition finding.
Aztec gilia \5\...........................  90-day petition finding.
White-tailed ptarmigan \5\................  90-day petition finding.
San Bernardino flying squirrel \5\........  90-day petition finding.
Bicknell's thrush \5\.....................  90-day petition finding.
Sonoran talussnail \5\....................  90-day petition finding.
2 AZ Sky Island plants (Graptopetalum       90-day petition finding.
 bartrami & Pectis imberbis) \5\.
I'iwi \5\.................................  90-day petition finding.
Humboldt marten...........................  90-day petition finding.
Desert massasauga.........................  90-day petition finding.
Western glacier stonefly (Zapada glacier).  90-day petition finding.
Thermophilic ostracod (Potamocypris         90-day petition finding.
 hunteri).
Sierra Nevada red fox \5\.................  90-day petition finding.
Boreal toad (eastern or southern Rocky Mtn  90-day petition finding.
 population) \5\.
Alexander Archipelago wolf \5\............  90-day petition finding.
------------------------------------------------------------------------
                      High-Priority Listing Actions
------------------------------------------------------------------------
20 Maui-Nui candidate species \2\ (17       Proposed listing.
 plants, 3 tree snails) (14 with LPN = 2,
 2 with LPN = 3, 3 with LPN = 8).
8 Gulf Coast mussels (southern kidneyshell  Proposed listing.
 (LPN = 2), round ebonyshell (LPN = 2),
 Alabama pearlshell (LPN = 2), southern
 sandshell (LPN = 5), fuzzy pigtoe (LPN =
 5), Choctaw bean (LPN = 5), narrow pigtoe
 (LPN = 5), and tapered pigtoe (LPN = 11))
 \4\.
Umtanum buckwheat (LPN = 2) and white       Proposed listing.
 bluffs bladderpod (LPN = 9) \4\.
Grotto sculpin (LPN = 2) \4\..............  Proposed listing.
2 Arkansas mussels (Neosho mucket (LPN =    Proposed listing.
 2) & Rabbitsfoot (LPN = 9)) \4\.
Diamond darter (LPN = 2) \4\..............  Proposed listing.
Gunnison sage-grouse (LPN = 2) \4\........  Proposed listing.
Coral Pink Sand Dunes Tiger Beetle (LPN =   Proposed listing.
 2) \5\.
Lesser prairie chicken (LPN = 2)..........  Proposed listing.
4 Texas salamanders (Austin blind           Proposed listing.
 salamander (LPN = 2), Salado salamander
 (LPN = 2), Georgetown salamander (LPN =
 8), Jollyville Plateau (LPN = 8)) \3\.
5 SW aquatics (Gonzales Spring Snail (LPN   Proposed listing.
 = 2), Diamond Y springsnail (LPN = 2),
 Phantom springsnail (LPN = 2), Phantom
 Cave snail (LPN = 2), Diminutive amphipod
 (LPN = 2)) \3\.
2 Texas plants (Texas golden gladecress     Proposed listing.
 (Leavenworthia texana) (LPN = 2), Neches
 River rose-mallow (Hibiscus dasycalyx)
 (LPN = 2)) \3\.
4 AZ plants (Acuna cactus (Echinomastus     Proposed listing.
 erectocentrus var. acunensis) (LPN = 3),
 Fickeisen plains cactus (Pediocactus
 peeblesianus fickeiseniae) (LPN = 3),
 Lemmon fleabane (Erigeron lemmonii) (LPN
 = 8), Gierisch mallow (Sphaeralcea
 gierischii) (LPN = 2)) \5\.
FL bonneted bat (LPN = 2) \3\.............  Proposed listing.
3 Southern FL plants (Florida semaphore     Proposed listing.
 cactus (Consolea corallicola) (LPN = 2),
 shellmound applecactus (Harrisia
 (=Cereus) aboriginum (=gracilis)) (LPN =
 2), Cape Sable thoroughwort (Chromolaena
 frustrata) (LPN = 2)) \5\.

[[Page 62212]]

 
21 Big Island (HI) species \5\ (includes 8  Proposed listing.
 candidate species--6 plants & 2 animals;
 4 with LPN = 2, 1 with LPN = 3, 1 with
 LPN = 4, 2 with LPN = 8).
12 Puget Sound prairie species (9           Proposed listing.
 subspecies of pocket gopher (Thomomys
 mazama ssp.) (LPN = 3), streaked horned
 lark (LPN = 3), Taylor's checkerspot (LPN
 = 3), Mardon skipper (LPN = 8)) \3\.
2 TN River mussels (fluted kidneyshell      Proposed listing.
 (LPN = 2), slabside pearlymussel (LPN =
 2)) \5\.
Jemez Mountain salamander (LPN = 2) \5\...  Proposed listing.
------------------------------------------------------------------------
 \1\ Funds for listing actions for these species were provided in
  previous FYs.
 \2\ Although funds for these high-priority listing actions were
  provided in FY 2008 or 2009, due to the complexity of these actions
  and competing priorities, these actions are still being developed.
 \3\ Partially funded with FY 2010 funds and FY 2011 funds.
 \4\ Funded with FY 2010 funds.
 \5\ Funded with FY 2011 funds.

    We have endeavored to make our listing actions as efficient and 
timely as possible, given the requirements of the relevant law and 
regulations, and constraints relating to workload and personnel. We are 
continually considering ways to streamline processes or achieve 
economies of scale, such as by batching related actions together. Given 
our limited budget for implementing section 4 of the Act, these actions 
described above collectively constitute expeditious progress.
    Texas fatmucket, golden orb, smooth pimpleback, Texas pimpleback, 
and Texas fawnsfoot will be added to the list of candidate species upon 
publication of this 12-month finding. We will continue to evaluate 
these species as new information becomes available. Continuing review 
will determine if a change in status is warranted, including the need 
to make prompt use of emergency listing procedures.
    We intend that any proposed listing determination for Texas 
fatmucket, golden orb, smooth pimpleback, Texas pimpleback, and Texas 
fawnsfoot will be as accurate as possible. Therefore, we will continue 
to accept additional information and comments from all concerned 
governmental agencies, the scientific community, industry, or any other 
interested party concerning this finding.

References Cited

    A complete list of references cited is available on the Internet at 
http://www.regulations.gov and upon request from the Clear Lake 
Ecological Services Field Office (see ADDRESSES).

Authors

    The primary authors of this notice are the staff members from the 
Southwest Region of the U.S. Fish and Wildlife Service.

Authority

    The authority for this section is section 4 of the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: September 26, 2011.
Rowan W. Gould,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2011-25471 Filed 10-5-11; 8:45 am]
BILLING CODE 4310-55-P