Endangered and Threatened Wildlife and Plants; 90-Day Finding on Petitions To List Nine Species of Mussels From Texas as Threatened or Endangered With Critical Habitat, 66260-66271 [E9-29698]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 74, Number 239 (Tuesday, December 15, 2009)]
[Proposed Rules]
[Pages 66260-66271]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-29698]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R2-ES-2009-0076; 92210-1111-0000 B2]


Endangered and Threatened Wildlife and Plants; 90-Day Finding on 
Petitions To List Nine Species of Mussels From Texas as Threatened or 
Endangered With Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

[[Page 66261]]


ACTION: Notice of petition finding and initiation of status review.

-----------------------------------------------------------------------

SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 90-day 
finding on two petitions to list nine species of freshwater mussels, 
the Texas fatmucket (Lampsilis bracteata), Texas heelsplitter 
(Potamilus amphichaenus), Salina mucket (Potamilus metnecktayi), golden 
orb (Quadrula aurea), smooth pimpleback (Quadrula houstonensis), Texas 
pimpleback (Quadrula petrina), false spike (Quincuncina mitchelli), 
Mexican fawnsfoot (Truncilla cognata), and Texas fawnsfoot (Truncilla 
macrodon), as threatened or endangered under the Endangered Species Act 
of 1973, as amended (Act) and designate critical habitat. Based on our 
review, we find that the petitions present substantial scientific or 
commercial information indicating that listing these species may be 
warranted. Therefore, with the publication of this notice, we are 
initiating a status review of the nine species of mussels to determine 
if listing them is warranted. To ensure that the status review is 
comprehensive, we are soliciting scientific and commercial data and 
other information regarding these species. At the conclusion of this 
review, we will issue a 12-month finding on the petitions, which will 
address whether the petitioned actions are warranted, as provided in 
section 4(b)(3)(B) of the Act. We will make a determination on critical 
habitat for these species if, and when, we initiate a listing action.

DATES: To allow us adequate time to conduct this review, we request 
that we receive information on or before February 16, 2010. After this 
date, you must submit information directly to the Field Office (see FOR 
FURTHER INFORMATION CONTACT section below). Please note that we may not 
be able to address or incorporate information that we receive after the 
above requested date.

ADDRESSES: You may submit information by one of the following methods:
     Federal rulemaking Portal: https://www.regulations.gov. 
Follow the instructions for submitting comments.
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: FWS-R2-ES-2009-0076; Division of Policy and Directives 
Management; U.S. Fish and Wildlife Service; 4401 Fairfax Drive, Suite 
222; Arlington, VA 22203.
    We will post all information received on https://www.regulations.gov. This generally means that we will post any 
personal information you provide us (see the Information Solicited 
section below for more details).

FOR FURTHER INFORMATION CONTACT: Stephen D. Parris, Field Supervisor, 
Clear Lake Ecological Services Field Office, 17629 El Camino Real, Ste. 
211, Houston, TX 77058; telephone 281-286-8282, extension 230. If you 
use a telecommunications device for the deaf (TDD), call the Federal 
Information Relay Service (FIRS) at 800-877-8339.


SUPPLEMENTARY INFORMATION:

Information Solicited

    When we make a finding that a petition presents substantial 
information indicating that listing a species may be warranted, we are 
required to promptly review the status of the species (status review). 
For the status review to be complete and based on the best available 
scientific and commercial information, we request information on the 
nine species of mussels (Texas fatmucket, Texas heelsplitter, Salina 
mucket, golden orb, smooth pimpleback, Texas pimpleback, false spike, 
Mexican fawnsfoot, and Texas fawnsfoot). We request information from 
governmental agencies, Native American Tribes, the scientific 
community, industry, and any other interested parties concerning the 
status of the nine species of mussels. We seek information for each of 
the nine species regarding:
     (1) The species' biology, range, and population trends, including:
     (a) Habitat requirements for feeding, breeding, and sheltering;
    (b) Genetics and taxonomy;
    (c) Historical and current range, including distribution patterns;
    (d) Historical and current population levels, and current and 
projected trends; and
    (e) Past and ongoing conservation measures for the species or its 
habitat.
    (2) The factors that are the basis for making a listing 
determination for a species under section 4(a) of the Act, which are:
    (a) The present or threatened destruction, modification, or 
curtailment of the species' 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 their continued 
existence.
     (3) Information about any ongoing conservation measures for, or 
threats to, the species and their habitats.
    Please include sufficient information with your submission (such as 
full references) to allow us to verify any scientific or commercial 
information you include.
    If, after the status review, we determine that listing any of the 
nine species of mussels under the Act is warranted, we will propose 
critical habitat (see definition in section 3(5)(A) of the Act), in 
accordance with section 4 of the Act, to the maximum extent prudent and 
determinable at the time we would propose to list the species. 
Therefore, within the geographical range currently occupied by the nine 
species of mussels, we also request data and information on:
    (1) What may constitute physical or biological features essential 
to the conservation of the species,
    (2) Where these features are currently found, and
     (3) Whether any of these features may require special management 
considerations or protection.
    In addition, we request data and information on specific areas 
outside the geographical area occupied by the species that are 
essential to the conservation of the species. Please provide specific 
comments and information as to what, if any, critical habitat you think 
we should propose for designation if any of the nine species of mussels 
are proposed for listing, and why such habitat meets the requirements 
of section 4 of the Act.
    Submissions merely stating support or opposition to the action 
under consideration without providing supporting information, although 
noted, will not be considered in making a determination. Section 
4(b)(1)(A) of the Act directs that determinations as to whether any 
species is an endangered or threatened species must be made solely on 
the basis of the best scientific and commercial data available.
    You may submit your information concerning this status review by 
one of the methods listed in the ADDRESSES section. We will not 
consider submissions sent by e-mail or fax or to an address not listed 
in the ADDRESSES section.
    If you submit information via https://www.regulations.gov, your 
entire submission--including any personal identifying information--will 
be posted on the website. If you submit a hardcopy that includes 
personal identifying information, you may request at the top of your 
document that we withhold this personal identifying information from 
public review. However, we cannot guarantee that we will be able to do 
so. We will post all hardcopy submissions on https://www.regulations.gov.

[[Page 66262]]

    Information and supporting documentation that we received and used 
in preparing this finding, will be available for public inspection at 
https://www.regulations.gov, or by appointment, during normal business 
hours, at the U.S. Fish and Wildlife Service, Clear Lake Ecological 
Services Field Office (see FOR FURTHER INFORMATION CONTACT).

Background

    Section 4(b)(3)(A) of the Act requires that we make a finding on 
whether a petition to list, delist, or reclassify a species presents 
substantial scientific or commercial information indicating that the 
petitioned action may be warranted. We are to base this finding on 
information provided in the petition, supporting information submitted 
with the petition, and information otherwise available in our files. To 
the maximum extent practicable, we are to make this finding within 90 
days of our receipt of the petition and publish our notice of this 
finding promptly in the Federal Register.
    Our standard for substantial scientific or commercial information 
within the Code of Federal Regulations (CFR) with regard to a 90-day 
petition finding is ``that amount of information that would lead a 
reasonable person to believe that the measure proposed in the petition 
may be warranted'' (50 CFR 424.14(b)). If we find that substantial 
scientific or commercial information was presented, we are required to 
commence a review of the status of the species, which is subsequently 
summarized in our 12-month finding.

Petition History

    On June 25, 2007, we received a petition dated June 18, 2007, from 
Forest Guardians (now WildEarth Guardians) requesting that the Service: 
(1) Evaluate 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 G1 or G1G2 species as either endangered or threatened with 
critical habitat. The petitioned group of species included the Texas 
fatmucket, Texas heelsplitter, Salina mucket, and golden orb. The 
petition incorporates all analyses, references, and documentation 
provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2007) into the 
petition. The information presented by NatureServe is considered to be 
a reputable source of information with respect to taxonomy and 
distribution. However, NatureServe indicates on their website that 
information in their database is not intended for determining whether 
species are warranted for listing under the Act. Where NatureServe 
presented assertions without supporting references that allow us to 
verify their statements, we found that the information presented by 
NatureServe was limited in its usefulness for this process. The 
petition clearly identified itself as such and included the 
identification information required at 50 CFR 424.14(a). We sent a 
letter dated July 11, 2007, to the petitioner acknowledging receipt of 
the petition and stating that the petition was under review by staff in 
our Southwest Regional Office.
    On June 18, 2008, we received a petition from WildEarth Guardians, 
dated June 12, 2008, to emergency list 32 species, including the Salina 
mucket, under the Administrative Procedure Act (APA) (5 U.S.C. 
Subchapter II) and the Act. In a letter dated July 22, 2008, we stated 
that the information provided in both the 2007 and 2008 petitions and 
in our files did not indicate that emergency listing of any of the 
petitioned species was warranted. That letter concluded our evaluation 
of the emergency aspect of the 2008 petition.
    On October 15, 2008, we received a petition dated October 9, 2008, 
from WildEarth Guardians requesting that the Service list six species 
of freshwater mussels, the smooth pimpleback, Texas pimpleback, false 
spike, Mexican fawnsfoot, Texas fawnsfoot, and southern hickorynut, as 
either endangered or threatened throughout their historic ranges within 
the United States and internationally. The petitioner also requested 
the designation of critical habitat for each of the petitioned mussel 
species. The petition clearly identified itself as such and included 
the identification information required at 50 CFR 424.14(a). In 
addition to other information cited in the petition, the petition 
incorporates all analyses, references, and documentation provided by 
NatureServe in its online database at https://www.natureserve.org/ 
(hereafter cited as NatureServe 2009) into the petition. To clarify, 
for the first four species addressed in this finding (Texas fatmucket, 
Texas heelsplitter, Salina mucket, and golden orb), we referenced the 
species profiles retrieved from the NatureServe online database in 
2007. For the following five species (smooth pimpleback, Texas 
pimpleback, false spike, Mexican fawnsfoot, and Texas fawnsfoot), we 
referenced the species profiles retrieved from the NatureServe online 
database in 2009. In a November 26, 2008, letter to the petitioner, we 
acknowledged receipt of the 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. This finding 
addresses 5 of the 6 petitioned species that occur within Region 2: 
smooth pimpleback, Texas pimpleback, false spike, Mexican fawnsfoot, 
and Texas fawnsfoot. Region 4 is addressing the southern hickorynut in 
a separate finding. In total, this 90-day finding includes nine mussel 
species; four species (Texas fatmucket, Texas heelsplitter, Salina 
mucket, and golden orb) are included from the June 18, 2007, petition, 
and five species (smooth pimpleback, Texas pimpleback, false spike, 
Mexican fawnsfoot, and Texas fawnsfoot) from the October 9, 2008, 
petition.

Previous Federal Actions

    There are no previous Federal actions or previous determinations 
for the Texas fatmucket, Salina mucket, golden orb, smooth pimpleback, 
Texas pimpleback and Texas fawnsfoot. However, the Texas heelsplitter, 
the false spike, Salina mucket (listed as Disconaias salinasensis), and 
the Mexican fawnsfoot were listed as Category 2 candidate species in 
the 1989 Animal Notice of Review (published January 6, 1989, at 54 FR 
554) and again in the 1991 and 1994 candidate species lists (56 FR 
58804 and 59 FR 58982, respectively). Category 2 candidate species 
included taxa for which information in the Service's possession 
indicated that a proposed listing rule was possibly appropriate, but we 
did not have sufficient data available on biological vulnerability and 
threats to support a proposed rule.
    In 1996, the Service changed its definition of candidate species 
(see 61 FR 7596). Species that had been listed as Category 1 species 
remained on the candidate list and those that were listed as Category 2 
species were dropped from the candidate list. Therefore, the Texas 
heelsplitter, the false spike, Salina mucket, and the Mexican fawnsfoot 
have not been on the candidate species list since 1996. There are no 
other previous Federal actions for these species.

Species Information

    All of the nine species are freshwater mussels in the family 
Unionidae, and all are known to occur in Texas (Howells 2007). Mussels 
in the family Unionidae are generally referred to as unionids, and we 
use that term in this finding. Freshwater mussels are bottom-dwelling 
and burrow into the substrate to maintain position on the stream 
bottom. Some mussel species require free-flowing streams, while other 
species

[[Page 66263]]

prefer, or are tolerant of, lentic (lake or pond) habitat. All 
freshwater mussels are filter-feeders, collecting algae, detritus, and 
bacteria from the water as it passes across the gills. Excessive 
amounts of suspended sediments can interfere with a mussel's ability to 
efficiently filter feed.
    Unionid reproduction requires separate male and female individuals. 
Fertilization takes place when a male discharges sperm into the water 
column and the female intakes the water-born sperm through siphon tubes 
during normal feeding and respiration (Howells et al. 1996, p. 9). 
Fertilized eggs are retained in the female's brood pouch (Howells et 
al. 1996, p. 9). The larvae, called glochidia, are retained in the 
female brood pouch until released, then live temporarily as obligate 
parasites (cannot live independently of its host) on a suitable host 
fish before transforming into bottom-dwelling juveniles (Howells et al. 
1996, p. 9). If the glochidia do not find a suitable host fish, they 
die.
Texas fatmucket
    Gould described the Texas fatmucket in 1855 (https://www.natureserve.org/explorer/; accessed July 2, 2007; hereafter cited as 
NatureServe 2007). The shell is tan to brown, is rhomboidal to oval in 
shape, and reaches 9 centimeters (cm) (3.5 inches (in)) in length 
(NatureServe 2007). The Texas fatmucket is historically known to occur 
in the Colorado, Guadalupe, and San Antonio river systems in Texas 
(Howells et al. 1996, p. 61). It is currently known from two 
tributaries of the Colorado River, the Llano River, upper San Saba 
River, and the upper Guadalupe River (Howells 2006, p. 97). This 
species occurs in streams and smaller rivers where water depths are 
less than 1 meter (m) (3.3 feet (ft)) and lives in substrates of sand, 
mud, and gravel (NatureServe 2007). The glochidial host fish include 
bluegill (Lepomis macrochirus) and green sunfish (L. cyanellus) 
(Howells et al. 1996, p. 62).
Texas heelsplitter
    Frierson described the Texas heelsplitter in 1898 (NatureServe 
2007). The shell is tan to brown, is elongated, and 17.7 cm (7 in) in 
length (Howells et al. 1996, p. 95). The Texas heelsplitter 
historically and currently is known to occur in the Neches River, the 
lower-central Trinity River, and the upper Sabine River in Texas 
(Howells 2006, p. 98). This species inhabits flowing waters, preferring 
mud or sand substrates in small to medium rivers, but it can also be 
found in reservoirs (NatureServe 2007). The glochidial host fish for 
the Texas heelsplitter are unknown (Howells et al. 1996. p. 96).
Salina mucket
    Johnson described the Salina mucket in 1998 (NatureServe 2007). 
Salina mucket has undergone taxonomic changes since the mussel's 
original listing on the 1989 Animal Notice of Review. We intend to 
investigate these taxonomic revisions further during the status review. 
The shell is tan to dark brown or black, is oval, and reaches a length 
of 10.5 cm (4.1 in) (Howells et al. 1996, pp. 103-104). The Salina 
mucket historically occurred in the Rio Grande as far north and west as 
New Mexico and as far south as northern Mexico (Howells et al. 1996, p. 
103). It currently is known from the Rio Grande in Texas from the Big 
Bend region in Brewster County downstream to below the Falcon Dam in 
Starr County (NatureServe 2007), although there is no mention of its 
occurrence in Falcon Reservoir. The species inhabits flowing streams 
and rivers with sand and gravel substrates (NatureServe 2007). The 
glochidial host fish for the Salina mucket are unknown (Howells et al. 
1996, p. 104).
Golden orb
    Lea described the golden orb in 1859 (NatureServe 2007). The shell 
varies from tan, reddish-brown, orange-brown, to gray-brown; is 
somewhat rectangular to broadly elliptical in shape; and reaches an 
overall length of 7.7 cm (3.0 in) (Howells et al. 1996, p. 108). The 
golden orb historically occurred in the Guadalupe, San Antonio, 
Colorado, and Nueces-Frio river systems. Currently, it is known from 
the upper and central Guadalupe River, lower San Marcos River, and Lake 
Corpus Christi in the lower Nueces River drainage (Howells 2006, p. 
98). This species appears to be restricted to flowing waters with sand, 
gravel, and cobble bottoms at depths of a few cm (few in) to over 3 m 
(9.8 ft). The glochidial host fish for the golden orb are unknown 
(Howellset al. 1996, p. 109).
Smooth pimpleback
    Lea described the smooth pimpleback in 1859 (https://www.natureserve.org/explorer/; accessed February 12-13, 2009; hereafter 
cited as NatureServe 2009). The shell is dark brown to black, round in 
shape, and generally smooth, but it may have a few small pimples 
(bumps) and can reach a length of 6.5 cm (2.5 in) (NatureServe 2009). 
The smooth pimpleback historically occurred in the Brazos and Colorado 
River systems of central Texas (Howells 2006, p. 98). Currently, it is 
known from the central Brazos, central Leon, central Little Brazos, and 
Navasota rivers in the Brazos River system, and from the central 
Colorado River (Howells 2007, slide 13). It prefers small-to moderate-
sized streams and rivers, as well as moderate-sized reservoirs, and it 
is found in mixed-mud, sand, and fine gravel substrate (NatureServe 
2009). The glochidial host fish for the smooth pimpleback are unknown 
(NatureServe 2009).
Texas pimpleback
    Gould described the Texas pimpleback in 1855 (NatureServe 2009). 
The shell is glossy and tan to brown in color, with some individuals 
displaying distinctive green and yellow markings (NatureServe 2009). 
The Texas pimpleback historically occurred in the upper and central 
Brazos, Colorado, and Guadalupe-San Antonio river systems (Howells 
2006, p. 99); currently, it is known from two tributaries of the 
Colorado River, the lower Concho and upper San Saba rivers, as well as 
the upper San Marcos River (Howells 2007, slide 13). Texas pimplebacks 
generally inhabit rivers with low flow rates with mud, gravel, and sand 
substrates (NatureServe 2009). The glochidial host fish for the Texas 
pimpleback are unknown (NatureServe 2009).
False spike
    Simpson described the false spike in 1895 (NatureServe 2009). The 
shell is tawny-brown to dark brown or black, oval to round in shape, 
and up to 13.2 cm (5.2 in) in length (Howells et al. 1996, p. 128). 
According to information in the petition, it has parallel, ripple-like 
ridges in the posterior and central portion of the shell. The false 
spike occurred historically in the Brazos, Colorado, and Guadalupe 
river systems in central Texas and in the Rio Grande system in New 
Mexico, Texas, and Mexico (NatureServe 2009). The only known extant 
population occurs in the lower San Marcos River, a tributary to the 
Guadalupe River system (Howells 2007, slide 16). False spike has been 
found in medium to large rivers with substrates varying from mixed mud, 
sand, and gravel, to cobble (NatureServe 2009). The glochidial host 
fish for the false spike are unknown (NatureServe 2009).
Mexican fawnsfoot
    Lea described the Mexican fawnsfoot in 1860 (NatureServe 2009). The 
shell is yellow- to gray-green, elliptical in shape, and up to 4.4 cm 
(1.7 in) in length (NatureServe 2009). The Mexican fawnsfoot 
historically occurred in a large section of the Rio Grande system, 
including the lower Pecos River near

[[Page 66264]]

Del Rio, Texas, and through the Rio Salado of Nuevo Leon and 
Tamaulipas, Mexico (NatureServe 2009). Now, the Mexican fawnsfoot is 
known to inhabit only a small section of the lower Rio Grande in 
Laredo, Texas (NatureServe 2009). Habitat preferences for the Mexican 
fawnsfoot are largely unknown because environmental modifications of 
the Rio Grande make it difficult to define clearly the habitats that 
are required or preferred by the Mexican fawnsfoot (NatureServe 2009). 
This species has not been reported from reservoirs, suggesting a 
preference for flowing streams and rivers with sand or gravel bottoms 
(NatureServe 2009). The glochidial host fish for the Mexican fawnsfoot 
are unknown (NatureServe 2009).
Texas fawnsfoot
    Lea described the Texas fawnsfoot in 1850 (NatureServe 2009). Shell 
color varies from gray-green, greenish-brown, orange brown to dark 
brown, often with a pattern of broken rays (NatureServe 2009). It is 
oval in shape and reaches a length of 5.5 cm (2.2 in) (NatureServe 
2009). The Texas fawnsfoot historically occurred in the Brazos and 
Colorado river systems. Until 2009, the only known surviving population 
was in the Brazos River system (NatureServe 2009). We are aware of a 
recently discovered population estimated to be approximately 3,000 
individuals in the upper portion of the Colorado River (Burlakova 2009, 
pers. comm.; Leggett 2009). We intend to investigate the report more 
thoroughly in our status review for the species. The species appears to 
prefer flowing rivers and large streams with sand, gravel, and mixed 
muddy substrates (NatureServe 2009). Living specimens have not been 
documented in reservoirs, but in the past have been found alive in 
flowing rice irrigation canals (NatureServe 2009). The glochidial host 
fish for the Texas fawnsfoot are unknown (NatureServe 2009).

Evaluation of Information for This Finding

    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
at 50 CFR 424 set forth the procedures for adding species to the 
Federal Lists of Endangered and Threatened Wildlife and Plants. A 
species may be determined to be an endangered or threatened species due 
to one or more of the five factors described in section 4(a)(1) of the 
Act: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence.
    In making this 90-day finding, we evaluated whether information 
regarding the nine species of mussels, as presented in the petitions 
and other information available in our files, is substantial, thereby 
indicating that the petitioned action may be warranted. Our evaluation 
of this information is presented below. The information discussed below 
was presented by the petitioner, unless otherwise noted.
Texas fatmucket

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petition incorporates all analyses, references, and 
documentation provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2007) into the 
petition. NatureServe (2007) claims that poor land management 
activities in the past century have resulted in the loss and 
modification of habitat, and the reduction in abundance, of the Texas 
fatmucket. NatureServe (2007) identifies intense overgrazing as a land 
management activity that has been harmful to the Texas fatmucket; 
however, no further discussion or reference is provided.
    Five of the six known populations, all in central Texas, are 
threatened by periodic flooding and possibly dewatering (NatureServe 
2007). Howells et al. (2003, p. 5), cited in NatureServe (2007), report 
that the population of a Colorado River tributary in Runnels County 
experienced extensive, if not complete, dewatering in 1999 and 2000, 
then flood-scouring in 2000 and 2001. No living or recently dead 
specimens could be found in a 2001 survey, and the stream had suffered 
major alterations in form and structure. A second population in a 
Concho River tributary in Tom Green County is presumed extirpated. The 
small stream reportedly dried completely in 1999 and 2000, and no 
specimens have been reported from the stream from subsequent surveys 
(Howells et al. 2003, p. 5). A third population in the San Saba River 
in Menard County experienced reduced water levels in the late 1990s 
followed by flooding in 2000. Based on post-flood examination of river 
and bank structure, mussels in the San Saba are thought to still 
persist (Howells et al. 2003, p. 5). A fourth population in the 
Guadalupe River in Kerr County is presumed to have been eliminated in 
1998, when river levels were drawn down to build a footbridge (Howells 
et al. 2003, p. 5). A fifth population in a Pedernales River tributary 
in Gillespie County was discovered when flood waters stranded specimens 
in 2002 (Howells et al. 2003, p. 5). This area had been surveyed prior 
to the flood, yielding no living or recently dead specimens, and the 
recent collection of a single living specimen at this site suggests 
that the population is limited (Howells et al. 2003, p. 5).
Evaluation of Information
    In our evaluation of the petition, we find that the petitioner 
provides substantial information indicating that listing the Texas 
fatmucket may be warranted due to present or threatened destruction, 
modification, or curtailment of the species' habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the Texas fatmucket 
due to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Texas fatmucket 
due to disease or predation may be warranted.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    NatureServe (2007) states that few occurrences of Texas fatmucket 
are appropriately protected and managed, and that only one Texas 
fatmucket population is currently in an area designated as a no-harvest 
mussel sanctuary, meaning commercial harvest is not permitted. 
NatureServe (2007) cites Howells et al. (1997, p.126) in stating that 
no-harvest sanctuary designations alone afford little protection where 
environmental disturbances of terrestrial habitats result in subsequent 
loss of aquatic habitats. NatureServe (2007) states that the Texas 
fatmucket is not a State or federally protected species.
Evaluation of Information
    Since mussel harvest was not identified as a potential threat to 
the Texas fatmucket, we find the petition does not provide substantial

[[Page 66265]]

information indicating that listing the species due to inadequacy of 
existing regulatory mechanisms may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

    The petitioner does not address other natural and manmade factors, 
and we have no information in our files indicating that listing the 
Texas fatmucket due to other natural and manmade factors may be 
warranted.
Texas heelsplitter

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petition incorporates all analyses, references, and 
documentation provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2007) into the 
petition. NatureServe (2007) claims that Texas heelsplitter habitat is 
threatened by siltation. NatureServe (2007) cites Neck and Howells 
(1995, cited in NatureServe 2007 as Neck and Howells 1994) in stating 
that sand and silt deposition create undesirable mussel habitat and 
cover existing mussel beds. In their status survey for the species, 
Neck and Howells (1995, p. 14) report that silt and mud deposition in 
the B.A. Steinhagen Reservoir, which is occupied by the Texas 
heelsplitter, caused many areas of the reservoir to become shallow and 
filled some bays in the reservoir with silt. These conditions do not 
support habitation by Texas heelsplitter.
    NatureServe (2007) identifies pollution as a threat to Texas 
heelsplitter habitat. Neck and Howells (1995, p. 15) state that 
increases in acidity, runoff, effluents from wood pulp and paper mills, 
human-caused nutrient enrichment, tar and oil, and increased silt loads 
due to land clearing are shown to have damaging effects on mussel 
habitat. Pollutants of these types have been reported in the upper 
Trinity River, in Pine Island Bayou (a tributary to the Neches River), 
and in the lower Neches River, all of which are situated within the 
range of the Texas heelsplitter (Neck and Howells 1995, p. 15). They 
conclude that the anticipated urban expansion of cities in Texas will 
likely amplify this threat in the foreseeable future (Neck and Howells 
1995, p. 14).
    Neck and Howells (1995, pp. 15-16), which is cited in NatureServe 
(2007), indicate that the Texas heelsplitter is negatively impacted by 
aquatic plants, including water hyacinth (Eichhornia crassipes) and 
hydrilla (Hydrilla verticillata), which have invaded reservoirs 
occupied by the Texas heelsplitter. Unmanaged, these plants can 
eliminate mussel habitat; however, the techniques currently employed 
for the management of these species, including mechanical removal, 
herbicides, and water drawdowns, also negatively affect mussel 
populations (Neck and Howells 1995, pp. 15-16). NatureServe (2007) 
identifies fluctuating water levels associated with water drawdowns at 
reservoirs as a current threat for the Texas heelsplitter.
Evaluation of Information
    Information in our files supports the claims made in the petition 
regarding the present and future threat of fluctuating water levels to 
the Texas heelsplitter and its habitat. Howells (2006, p. 32) indicates 
that the Texas heelsplitter is negatively affected by water drawdowns 
at B.A. Steinhagen Reservoir, part of the Neches River drainage. These 
drawdowns result in mussel mortality and overall decreased mussel 
abundance and diversity (Howells 2006, pp. 24-34). Since the early 
1990s, the Texas Parks and Wildlife Department (TPWD) and the reservoir 
operator have employed mid-winter water drawdowns to reduce aquatic 
plant density through drying and cold temperatures on the reservoir 
(Howells 2006, p. 32). The water level is lowered slowly to allow the 
mussels to follow the receding water level, and the duration of the 
drawdown is as short as possible to minimize mussel mortality; however, 
repeated drawdowns in the range of the Texas heelsplitter may be 
decreasing the abundance of the species (Howells 2006, p. 32).
    In our evaluation of the petition and information in our files, we 
find that there is substantial information indicating that listing the 
Texas heelsplitter may be warranted due to the present or threatened 
destruction, modification, or curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the Texas heelsplitter 
due to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Texas 
heelsplitter due to disease or predation may be warranted.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    NatureServe (2007) states that it is unknown whether any 
occurrences of Texas heelsplitter are appropriately protected and 
managed.
Evaluation of Information
    We do not consider the statement by NatureServe (2007) to be a 
sufficient presentation of information indicating to a reasonable 
person that listing may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

    The petitioner does not address other natural and manmade factors, 
and we have no information in our files indicating that listing the 
Texas heelsplitter due to other natural and manmade factors may be 
warranted.
Salina mucket

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petition incorporates all analyses, references, and 
documentation provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2007) into the 
petition. NatureServe (2007) identifies poor land and water management 
practices as threats to Salina mucket habitat. NatureServe (2007) cites 
Howells (2003, p. 70; cited in NatureServe 2007 as Howells 2001) in 
stating that the lower Rio Grande system within the range of the Salina 
mucket has experienced a significant increase in human population and 
urban development in the last 30 years. Land management activities 
associated with increased human development include land clearing and 
construction of impervious surfaces, which contribute to increased 
runoff and silt loads during storms and to additional scouring and 
riverbed modifications (Howells 2003, p. 66). Howells (2004b, p. 2) 
states that the only known surviving Salina mucket specimens in the Rio 
Grande are in areas undergoing major development and modification. 
Increased water demands that are projected with continuing residential 
and commercial

[[Page 66266]]

development in the range of the Salina mucket will likely compound 
factors currently affecting the species (Howells 2004b, p. 2).
    NatureServe (2007) identifies siltation as a threat to Salina 
mucket habitat; however, no further discussion is provided. NatureServe 
(2007) also identifies drought-related dewatering as a threat to Salina 
mucket habitat. The Salina mucket habitat within the Rio Grande system 
has been subject to periods of drought punctuated by severe storm 
events, often producing scouring floods that modify the riverbed and 
alter mussel habitat (Howells 2003, p. 66). Historical drought-related 
dewatering likely reduced or eliminated some unionid populations in the 
region, and the current decline in water flow rates constitutes an 
increasing threat to the species and its habitat (Howells 2003, p. 67).
Evaluation of Information
    In our evaluation of the petition, we find that the petitioner 
provides substantial information indicating that listing the Salina 
mucket may be warranted due to the present or threatened destruction, 
modification, or curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the Salina mucket due 
to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Salina mucket 
due to disease or predation may be warranted.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    NatureServe (2007) states that no occurrences of Salina mucket are 
appropriately protected and managed, that no Salina mucket populations 
occur in State-designated no-harvest mussel sanctuaries, and that the 
Salina mucket is not a State or federally protected species.
Evaluation of Information
    Since mussel harvest was not identified as a potential threat to 
the Salina mucket, we find the petition does not provide substantial 
information indicating that listing the species due to inadequacy of 
existing regulatory mechanisms may be warranted.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

Information Provided in the Petition
    NatureServe (2007) identifies population isolation as a threat to 
the Salina mucket. Howells (2003, p. 68) indicates that the Pecos 
River, a tributary of the Rio Grande, is the major source of elevated 
salinity of the waters in the lower Rio Grande drainage. Natural salt 
seeps and deposits are present in the area, but groundwater pumping 
that has lowered the water table and reduced freshwater input, long 
periods of reduced precipitation, and brines from oil and gas drilling 
operations likely contribute to current high saline conditions (Howells 
2003, pp. 68-69). Howells (2004b, p. 2) reports that the salinity of 
the Pecos River creates a functional barrier between Salina mucket 
specimens in the area, thus inhibiting opportunities for dispersal and 
interbreeding. This physical separation may result in the genetic 
isolation of surviving Salina mucket populations downstream of the Big 
Bend in the area of Brewster County, Texas (Howells 2003, p. 69).
Evaluation of Information
    In our evaluation of the petition, we find that the petition 
presents substantial information indicating that listing the Salina 
mucket may be warranted due to population isolation.
Golden orb

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petition incorporates all analyses, references, and 
documentation provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2007) into the 
petition. NatureServe (2007) identifies flooding as a threat to golden 
orb habitat. Howells et al. (1997, p. 118), cited in NatureServe 
(2007), report that the greatest decline in golden orb numbers appears 
to have occurred in 1978 during a major hurricane and subsequent 
flooding in the species' range. NatureServe (2007) asserts that this 
single event appears to have reduced the species to four primary 
populations, and that three of these populations in the Guadalupe River 
are still subject to flood-related scouring and large water-level 
fluctuations.
    NatureServe (2007) identifies the effects of poor land and water 
management practices as a threat to golden orb habitat; however, no 
further discussion is provided. NatureServe (2007) also identifies 
drought as a threat to golden orb habitat; however, no further 
discussion is provided.
Evaluation of Information
    The petition does not provide substantial information indicating 
that listing the golden orb due to poor land and water management or to 
drought may be warranted. However, information in our files from 
Howells' 2006 Statewide freshwater mussel survey supports the 
petitioner's claim of the species' negative response to flooding in its 
habitat. Specifically, in the Guadalupe River below the Upper Guadalupe 
River Authority dam, no golden orbs were found in a survey following a 
1996 flood, three were found dead following a second flood in 1997, 
none were found following a high water release from the dam 4 months 
later, and none were found in a 2005 survey (Howells 2006, p. 71). In 
our evaluation of the petition and information in our files, we 
therefore find that there is substantial information indicating that 
listing the golden orb may be warranted due to the present or 
threatened destruction, modification, or curtailment of its habitat or 
range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific, or educational purposes, and we have no 
information in our files indicating that listing the golden orb due to 
overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the golden orb due 
to disease or predation may be warranted.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    NatureServe (2007) states that few occurrences of golden orb are 
appropriately protected and managed, and that none of the inhabited 
sites of the four known populations are protected. NatureServe (2007) 
states that the golden orb is not a State or federally protected 
species.
Evaluation of Information
    We do not consider the statements by NatureServe (2007) to be a 
sufficient presentation of information indicating

[[Page 66267]]

to a reasonable person that listing may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

    The petitioner does not address other natural and manmade factors, 
and we have no information in our files indicating that listing the 
golden orb due to other natural and manmade factors may be warranted.
Smooth pimpleback

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    In addition to other information cited in the petition, the 
petition incorporates all analyses, references, and documentation 
provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2009) into the 
petition. The petitioner identifies increased human activity within the 
species' range and associated poor land and water management practices 
as a threat to smooth pimpleback habitat. NatureServe (2009) adds that 
recent habitat loss continues to affect the species.
    The petitioner identifies pollution as a threat to smooth 
pimpleback habitat, and cites NatureServe (2009) in claiming that a 
chemical dump on the Little Brazos River in 1993 eliminated many of the 
mussel populations there, including the smooth pimpleback.
    The petitioner cites NatureServe (2009) in asserting that drought 
conditions that decreased surface water levels in the 1980s in the Leon 
River range caused extensive loss of smooth pimpleback individuals. The 
petitioner also cites NatureServe (2009) in asserting that scouring 
floods in 1978 throughout the range of the species in central Texas 
were responsible for the reduction or elimination of many mussel 
populations, including the smooth pimpleback. NatureServe (2009) 
clarifies that the species does not tolerate dramatic water 
fluctuations, scoured bedrock substrates, or shifting sand bottoms, all 
of which are associated with floods.
Evaluation of Information
    Information in our files indicates that water fluctuations 
unrelated to drought occur in areas occupied by smooth pimplebacks. 
Howells (2006, p. 67) reports that water-level drawdowns adversely 
impact Inks Lake's population of smooth pimplebacks. Lake elevation is 
rapidly reduced by 3 meters (m) (9.8 ft) during biannual maintenance 
and repair drawdowns (Howells 2006, p. 67). Howells (2006, p. 67) 
reports that these drawdowns occur so quickly that any unionids 
occupying the shallows are generally killed with each drawdown.
    In our evaluation of the petition and information in our files, we 
find that there is substantial information indicating that listing the 
smooth pimpleback may be warranted due to the present or threatened 
destruction, modification, or curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the smooth pimpleback 
due to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the smooth 
pimpleback due to disease or predation may be warranted.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    NatureServe (2009) states that no occurrences of smooth pimpleback 
are appropriately protected and managed, and that no smooth pimpleback 
populations occur in State-designated no-harvest mussel sanctuaries. 
The petitioner states that the smooth pimpleback is not a State or 
federally protected species (NatureServe 2009).
Evaluation of Information
    Since mussel harvest was not identified as a potential threat to 
the smooth pimpleback, we find the petition does not provide 
substantial information indicating that listing the species due to 
inadequacy of existing regulatory mechanisms may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

Information Provided in the Petition
    The petitioner identifies climate change as an additional factor 
affecting the species' continued existence; however, no specific 
justification or reference is provided.
Evaluation of Information
    The information presented on climate change is not specific to the 
smooth pimpleback and no specific references were provided. The 
petition does not provide substantial information indicating that 
listing the species due to climate change may be warranted. We intend 
to investigate this factor more thoroughly in our status review of the 
species.
Texas pimpleback

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petitioner states that dewatering is a threat to the species, 
but points out that some individuals survive severe stream dewatering. 
Howells (2006, p. 61) reports that in the Concho River in Concho 
County, low water levels and high temperatures killed large numbers of 
Texas pimplebacks and other mussels in 1997, and in 1999 and early 
2000. The Concho River was reduced to stagnant pools and dry bottoms. 
Results from subsequent surveys indicate that Texas pimpleback 
abundance was significantly reduced, presumably due to habitat 
modifications that restrict mussel habitation (Howells 2006, p. 61). 
The petitioner states that habitat occupied by the Texas pimpleback is 
threatened by drought and flooding; however, no further discussion is 
provided.
Evaluation of Information
    Information in our files shows that over the 10 years from 1998 to 
2007, there was zero flow measured at the stream gage at the Concho 
River mussel survey site 26 percent of the days (Asquith and Heitmuller 
2008, pp. 810-813, 846-853). These data suggest that dewatering may be 
continuing in the Concho River.
    Information in our files indicates that scouring floods and 
drought-related dewatering have caused recent losses of Texas 
pimpleback populations in Runnels County, Texas. No live Texas 
pimpleback individuals were found during a 2005 survey in the Colorado 
River drainage at either a site on the San Saba River or one on Elm 
Creek where they had been found previously (Howells 2006, pp. 63-64). 
These sites showed signs of extensive flood scouring during surveys 
conducted throughout the 1990s and early 2000s, and overall mussel 
abundance and diversity have been reduced (Howells 2006, pp. 63-64).
    In our evaluation of the petition and information in our files, we 
find that

[[Page 66268]]

there is substantial information indicating that listing the Texas 
pimpleback may be warranted due to the present or threatened 
destruction, modification, or curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

Information Provided in the Petition
    The petitioner states that overcollection at one site has 
negatively impacted the Texas pimpleback; however, no further 
discussion is provided.
Evaluation of Information
    Information in our files indicates that the Texas pimpleback may be 
taken by rare-shell collectors (Howells 2004a, slide 14). Howells 
(2006, p. 63) reports that details released over the Internet in 2001 
disclosing the location of rare mussels at the site may have been used 
by rare-shell collectors to find and harvest Texas pimplebacks.
    We find that the petition and information in our files presents 
substantial information indicating that listing the Texas pimpleback 
may be warranted due to overutilization for commercial, recreational, 
scientific, or educational purposes.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Texas 
pimpleback due to disease or predation may be warranted.

D. The Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    In addition to other information cited in the petition, the 
petition incorporates all analyses, references, and documentation 
provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2009) into the 
petition. NatureServe (2009) indicates that few occurrences of Texas 
pimpleback are appropriately protected and managed, and that only one 
Texas pimpleback population is currently in a State-designated no-
harvest mussel sanctuary. The petitioner cites Howells et al. (1997, 
p.126) in stating that no-harvest sanctuary designations alone afford 
little protection where environmental disturbances of terrestrial 
habitats result in subsequent loss of aquatic habitats.
Evaluation of Information
    In Factor B, the petitioner and our files identify overutilization 
for commercial, recreational, scientific, or educational purposes as a 
potential threat to the Texas pimpleback. Here, we find that the 
petitioner and information in our files provides substantial 
information indicating that listing the Texas pimpleback may be 
warranted due to inadequacy of existing regulatory mechanisms to 
protect the species from this potential threat.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

Information Provided in the Petition
    The petitioner identifies climate change as an additional factor 
affecting the species' continued existence; however, no specific 
justification or reference is provided.
Evaluation of Information
    The information presented on climate change is not specific to the 
Texas pimpleback and no specific references were provided. The petition 
does not provide substantial information indicating that listing the 
species due to climate change may be warranted. We intend to 
investigate this factor more thoroughly in our status review of the 
species.
False spike

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petitioner claims that the dramatic land use modification of 
the lower Rio Grande drainage over the past 100 years has negatively 
affected the false spike. The petitioner further claims that continued 
development and modification, including increases in human activity and 
associated negative environmental impacts, may preclude future 
conservation of the species.
    The petitioner identifies overgrazing and increased runoff from 
rains as threats to false spike habitat in central Texas. The 
petitioner, citing a personal communication with R. Howells in July 
2008, claims that in the mid-to late 1800s, overgrazing resulted in 
loss of terrestrial vegetative cover and soils. Subsequently, when 
rains fell, runoff increased, scouring riverbeds. The petitioner 
references the same personal communication in stating that prior to the 
1900s, the Guadalupe River never rose more than 1.8 m (6 ft), but that 
6-m (20-ft) rises are now regularly observed. This has resulted in 
scour of river bottoms to bedrock and cobble, which the petitioner 
claims is unacceptable habitat for unionid mussels.
    The petitioner identifies drought and flooding as threats to false 
spike habitat. Howells (2006, p. 73) states that drought conditions in 
the late 1970s, followed by major flooding events in 1978 and 1981 
within the false spike's range in the San Marcos River, part of the 
Guadalupe River drainage, likely had negative impacts on unionid 
mussels in that area, including the false spike.
Evaluation of Information
    Information in our files supports the petitioner's claim that 
humans have significantly modified land use in the Rio Grande basin in 
Texas and Mexico, and that this land use change may be a threat to 
false spike. Howells (2003, pp. 66, 70) states that human-caused 
impacts appear to be the major reason for the massive reduction in 
mussel fauna and diversity there, including the apparent extinction of 
the false spike. He identifies climate change; altered water flows; 
impoundments; and increased nutrient, salt, and sediment pollution as 
the human-caused threats responsible for the threats (Howells 2003, pp. 
66-70).
    The petitioner and information in our files provide substantial 
information indicating that listing the false spike may be warranted 
due to the present or threatened destruction, modification, or 
curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the false spike due to 
overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the false spike due 
to disease or predation may be warranted.

D. The Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    In addition to other information cited in the petition, the 
petition incorporates all analyses, references, and documentation 
provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2009) into the 
petition. NatureServe (2009) states that

[[Page 66269]]

no occurrences of false spike are appropriately protected and managed.
Evaluation of Information
    Since mussel harvest was not identified as a potential threat to 
the false spike, we find the petition does not provide substantial 
information indicating that listing the species due to inadequacy of 
existing regulatory mechanisms may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

Information Provided in the Petition
    The petitioner identifies climate change as an additional factor 
affecting the false spike's continued existence; however, no specific 
justification or reference is provided.
Evaluation of Information
    The information presented on climate change is not specific to the 
false spike and no specific references were provided. The petition does 
not provide substantial information indicating that listing the species 
due to climate change may be warranted. We intend to investigate this 
factor more thoroughly in our status review of the species.
Mexican fawnsfoot

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    In addition to other information cited in the petition, the 
petition incorporates all analyses, references, and documentation 
provided by NatureServe in its online database at https://www.natureserve.org/ (hereafter cited as NatureServe 2009) into the 
petition. NatureServe (2009) identifies the effects of increased human 
activity as a threat to Mexican fawnsfoot habitat. Trade and 
development along the U.S. (Texas)-Mexico border have had extensive 
environmental impacts on this area, which has already undergone great 
ecological modification (NatureServe 2009). The petitioner cites 
Howells (2004a) in stating that the only known extant population of the 
Mexican fawnsfoot, located near Laredo, Texas, is threatened by impacts 
from development. Additional landscape modification is anticipated, 
including the proposed construction of a fence at the border (Howells 
2007, slide 14). The petitioner also identifies smothering and 
siltation as a threat to the Mexican fawnsfoot and its habitat; 
however, no further discussion is provided. The petitioner cites 
NatureServe (2009) in stating that the general fragility of the Rio 
Grande aquatic ecosystem and ecological alterations to date are likely 
a cause of the extreme rarity of this species.
    The petitioner identifies dewatering as a threat to Mexican 
fawnsfoot habitat. The petitioner cites Howells (2004b, p. 2) in 
stating that all unionid assemblages in the Rio Grande basin, including 
the Mexican fawnsfoot, have been subject to drought-related dewatering.
Evaluation of Information
    In our evaluation of the petition, we find that the petitioner 
provides substantial information indicating that listing the Mexican 
fawnsfoot may be warranted due to the present or threatened 
destruction, modification, or curtailment of its habitat or range.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific, or educational purposes, and we have no 
information in our files indicating that listing the Mexican fawnsfoot 
due to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Mexican 
fawnsfoot due to disease or predation may be warranted.

D. The Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    The petitioner cites NatureServe (2009) in stating that no 
occurrences of Mexican fawnsfoot are appropriately protected and 
managed, and that no Mexican fawnsfoot populations occur in State-
designated no-harvest mussel sanctuaries. The petitioner states that 
the Mexican Fawnsfoot is not a State or federally protected species 
(NatureServe 2009).
Evaluation of Information
    Since mussel harvest was not identified as a potential threat to 
the Mexican fawnsfoot, we find the petition does not provide 
substantial information indicating that listing the species due to 
inadequacy of existing regulatory mechanisms may be warranted.

E. Other Natural or Manmade Factors Affecting the Species' Continued 
Existence

Information Provided in the Petition
    The petition identifies climate change as an additional factor 
affecting the species' continued existence; however, no specific 
justification or reference is provided.
Evaluation of Information
    The information presented on climate change is not specific to the 
Mexican fawnsfoot and no specific references were provided. The 
petition does not provide substantial information indicating that 
listing the species due to climate change may be warranted. We intend 
to investigate this factor more thoroughly in our status review of the 
species.
Texas fawnsfoot

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Information Provided in the Petition
    The petitioner identifies aquatic habitat destruction and 
modification from wide-ranging terrestrial sources as a threat to the 
Texas fawnsfoot; however, these terrestrial sources are not specified 
and no further discussion is provided. The petitioner also identifies 
smothering and siltation as a threat to the Texas fawnsfoot and its 
habitat; however, no further discussion is provided that is specific to 
the species or to the rivers and streams where it is known to occur.
    The petitioner identifies dewatering as a threat to Texas fawnsfoot 
habitat, stating that in 2000, the Colorado River above Lake Buchanan 
dried, and all mussels in that area, including the Texas fawnsfoot, 
were presumed lost. The petitioner further states that because the 
species is intolerant of impounded water bodies, the species would not 
be able to recolonize the dewatered area from Lake Buchanan. The 
petitioner also identifies scouring floods during times of intense 
precipitation as a threat to Texas fawnsfoot habitat.
Evaluation of Information
    In our evaluation of the petition, we find that the petitioner 
provides substantial information indicating that listing the Texas 
fawnsfoot may be warranted due to the present or threatened 
destruction, modification, or curtailment of its habitat or range.

[[Page 66270]]

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The petitioner does not address overutilization for commercial, 
recreational, scientific or educational purposes, and we have no 
information in our files indicating that listing the Texas fawnsfoot 
due to overutilization may be warranted.

C. Disease or Predation

    The petitioner does not address disease or predation, and we have 
no information in our files indicating that listing the Texas fawnsfoot 
due to disease or predation may be warranted.

D. The Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    In addition to other information cited in the petition, the 
petition incorporates all analyses, references, and documentatio