[Federal Register Volume 86, Number 163 (Thursday, August 26, 2021)]
[Proposed Rules]
[Pages 47916-48011]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-18012]



[[Page 47915]]

Vol. 86

Thursday,

No. 163

August 26, 2021

Part IV





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; Endangered Species 
Status With Critical Habitat for Guadalupe Fatmucket, Texas Fatmucket, 
Guadalupe Orb, Texas Pimpleback, and False Spike, and Threatened 
Species Status With Section 4(D) Rule and Critical Habitat for Texas 
Fawnsfoot; Proposed Rule

Federal Register / Vol. 86, No. 163 / Thursday, August 26, 2021 / 
Proposed Rules

[[Page 47916]]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R2-ES-2019-0061; FF09E21000 FXES11110900000 212]
RIN 1018-BD16


Endangered and Threatened Wildlife and Plants; Endangered Species 
Status With Critical Habitat for Guadalupe Fatmucket, Texas Fatmucket, 
Guadalupe Orb, Texas Pimpleback, and False Spike, and Threatened 
Species Status With Section 4(d) Rule and Critical Habitat for Texas 
Fawnsfoot

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service or USFWS), 
propose to list six Central Texas mussel species: The Guadalupe 
fatmucket (Lampsilis bergmanni), Texas fatmucket (Lampsilis bracteata), 
Texas fawnsfoot (Truncilla macrodon), Guadalupe orb (Cyclonaias necki), 
Texas pimpleback (Cyclonaias (=Quadrula) petrina), and false spike 
(Fusconaia (=Quincuncina) mitchelli) as endangered or threatened under 
the Endangered Species Act of 1973, as amended (Act). After review of 
the best available scientific and commercial information, we find that 
listing Guadalupe fatmucket, Texas fatmucket, Guadalupe orb, Texas 
pimpleback, and false spike as endangered species is warranted, and 
listing Texas fawnsfoot as a threatened species is warranted. We 
propose a rule issued under section 4(d) of the Act (``4(d) rule'') for 
the Texas fawnsfoot. If we finalize this rule as proposed, it would add 
these species to the List of Endangered and Threatened Wildlife and 
extend the Act's protections to the species. We also propose to 
designate critical habitat for all six species under the Act. In total, 
approximately 1,944 river miles (3,129 river kilometers) in Texas fall 
within the boundaries of the proposed critical habitat designations. We 
also announce the availability of a draft economic analysis (DEA) of 
the proposed designation of critical habitat. We also are notifying the 
public that we have scheduled two informational meetings followed by 
public hearings on the proposed rule.

DATES: 
    Comment submission: We will accept comments received or postmarked 
on or before October 25, 2021. Comments submitted electronically using 
the Federal eRulemaking Portal (see ADDRESSES, below) must be received 
by 11:59 p.m. Eastern Time on the closing date.
    Public informational meeting and public hearing: We will hold 
public informational sessions from 5:00 p.m. to 6:00 p.m., Central 
Time, followed by public hearings from 6:30 p.m. to 8:30 p.m., Central 
Time, on September 14, 2021, and September 16, 2021.

ADDRESSES: You may submit comments by one of the following methods:
    (1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. In the Search box, enter FWS-R2-ES-2019-0061, 
which is the docket number for this rulemaking. Then, in the Search 
panel on the left side of the screen, under the Document Type heading, 
check the Proposed Rules box to locate this document. You may submit a 
comment by clicking on ``Comment Now!''
    (2) By hard copy: Submit by U.S. mail to: Public Comments 
Processing, Attn: FWS-R2-ES-2019-0061, U.S. Fish and Wildlife Service, 
MS: JAO/1N, 5275 Leesburg Pike, Falls Church, VA 22041-3803.
    We request that you send comments only by the methods described 
above. We will post all comments on http://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see Information Requested, below, for more information).
    Public informational meetings and public hearings: The public 
informational meetings and the public hearings will be held virtually 
using the Zoom platform. See Public Hearing, below, for more 
information.
    Availability of supporting materials: For the critical habitat 
designation, the coordinates or plot points or both from which the maps 
are generated are included in the decision file and are available at 
https://www.fws.gov/southwest/es/AustinTexas/ESA_Sp_Mussels.html and at 
http://www.regulations.gov under Docket No. FWS-R2-ES-2019-0061. Any 
additional tools or supporting information that we may develop for the 
critical habitat designation will also be available at the Service 
website set out above, and may also be included in the preamble and/or 
at http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Adam Zerrenner, Field Supervisor, U.S. 
Fish and Wildlife Service, Austin Ecological Services Field Office, 
10711 Burnet Rd., Suite 200, Austin, TX 78758; telephone (512) 490-
0057. Persons who use a telecommunications device for the deaf (TDD) 
may call the Federal Relay Service at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

    Why we need to publish a rule. Under the Act, if we determine that 
a species may be an endangered or threatened species throughout all or 
a significant portion of its range, we are required to promptly publish 
a proposal in the Federal Register and make a determination on our 
proposal within 1 year. To the maximum extent prudent and determinable, 
we must designate critical habitat for any species that we determine to 
be an endangered or threatened species under the Act. Listing a species 
as an endangered or threatened species and designation of critical 
habitat can only be completed by issuing a rule.
    What this document does. This document proposes the Guadalupe 
fatmucket (Lampsilis bergmanni), Texas fatmucket (Lampsilis bracteata), 
Guadalupe orb (Cyclonaias necki), Texas pimpleback (Cyclonaias 
(=Quadrula) petrina), and false spike (Fusconaia (=Quincuncina) 
mitchelli) as endangered species and Texas fawnsfoot (Truncilla 
macrodon) as a threatened species. This document also proposes the 
designation of critical habitat for all six species, as well as a 4(d) 
rule providing protective regulations for the Texas fawnsfoot.
    The basis for our action. Under the Act, we may determine that a 
species is an endangered or threatened species based on any of 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. We have determined habitat loss through changes in 
water quality and quantity, as well as increased fine sediments (Factor 
A), are the primary threats to these species.
    Under the Act, for any species that is determined to be threatened, 
we must provide protective regulations to provide for the conservation 
of that species. For the Texas fawnsfoot, we are proposing to prohibit 
take and possession.
    Section 4(a)(3) of the Act requires the Secretary of the Interior 
(Secretary) to designate critical habitat concurrent with listing to 
the maximum extent prudent and determinable. Section 4(b)(2) of the Act 
states that the Secretary must make the designation on

[[Page 47917]]

the basis of the best scientific data available and after taking into 
consideration the economic impact, the impact on national security, and 
any other relevant impacts of specifying any particular area as 
critical habitat. Section 3(5)(A) of the Act defines critical habitat 
as (i) the specific areas within the geographical area occupied by the 
species, at the time it is listed, on which are found those physical or 
biological features (I) essential to the conservation of the species 
and (II) which may require special management considerations or 
protections; and (ii) specific areas outside the geographical area 
occupied by the species at the time it is listed, upon a determination 
by the Secretary that such areas are essential for the conservation of 
the species.
    Supporting analyses. We prepared an analysis of the economic 
impacts of the proposed critical habitat designations and hereby 
announce the availability of the draft economic analysis for public 
review and comment.
    Our species status assessment report (SSA report) documents the 
results of the comprehensive biological status review for the central 
Texas mussels and provides an account of the species' overall viability 
through forecasting of the species' condition in the future (Service 
2019a, entire). Additionally, the SSA report contains our analysis of 
required habitat and the existing conditions of that habitat.
    Peer review. In accordance with our joint policy on peer review 
published in the Federal Register on July 1, 1994 (59 FR 34270), and 
our August 22, 2016, memorandum updating and clarifying the role of 
peer review of listing actions under the Act, we sought the expert 
opinions of eight appropriate specialists regarding the species status 
assessment report. We received responses from six specialists, which 
informed this proposed rule. The purpose of peer review is to ensure 
that our listing determinations, critical habitat designations, and 
4(d) rules are based on scientifically sound data, assumptions, and 
analyses. The peer reviewers have expertise in the biology, habitat, 
and threats to the species.
    We sought comments from independent specialists on the SSA report 
to ensure that our proposal is based on scientifically sound data and 
analyses. We received feedback from six scientists with expertise in 
freshwater mussel biology, ecology, genetics, climate science, and 
hydrology as peer review of the SSA report. The reviewers were 
generally supportive of our approach and made suggestions and comments 
that strengthened our analysis. The SSA report and other materials 
relating to this proposal can be found at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    Because we will consider all comments and information received 
during the comment period, our final determinations may differ from 
this proposal. Based on the new information we receive (and any 
comments on that new information), we may conclude that any of these 
species are threatened instead of endangered, or endangered instead of 
threatened, or we may conclude that any of these species do not warrant 
listing as either an endangered species or a threatened species. Such 
final decisions would be a logical outgrowth of this proposal, as long 
as we: (a) Base the decisions on the best scientific and commercial 
data available after considering all of the relevant factors; (2) do 
not rely on factors Congress has not intended us to consider; and (3) 
articulate a rational connection between the facts found and the 
conclusions made, including why we changed our conclusion.

Information Requested

    We intend that any final action resulting from this proposed rule 
will be based on the best scientific and commercial data available and 
be as accurate and as effective as possible. Therefore, we request 
comments or information from other concerned governmental agencies, 
Native American tribes, the scientific community, industry, or any 
other interested parties concerning this proposed rule. We particularly 
seek comments concerning:
    (1) The species' biology, range, and population trends, including:
    (a) Biological or ecological requirements of these species, 
including habitat requirements for feeding, breeding, and sheltering;
    (b) Genetics, genomics, systematics, and taxonomy;
    (c) Historical and current range, including distribution patterns;
    (d) Historical and current population levels, abundance, and 
current and projected trends; and
    (e) Past and ongoing conservation measures for these species, their 
habitats, or both.
    (2) Factors that may affect the continued existence of the species, 
which may include habitat modification or destruction, overutilization, 
disease, predation, the inadequacy of existing regulatory mechanisms, 
or other natural or manmade factors.
    (3) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to these species and existing regulations 
that may be addressing those threats.
    (4) Additional information concerning the historical and current 
status, range, distribution, and population size of these species, 
including the locations of any additional populations of the Central 
Texas mussels.
    (5) Information on regulations that are necessary and advisable to 
provide for the conservation of the Texas fawnsfoot and that the 
Service can consider in developing a 4(d) rule for the species. In 
particular, information concerning the extent to which we should 
include any of the section 9 prohibitions in the 4(d) rule or whether 
any other forms of take should be excepted from the prohibitions in the 
4(d) rule.
    (6) The reasons why we should or should not designate habitat as 
``critical habitat'' under section 4 of the Act, including information 
to inform the following factors such that a designation of critical 
habitat may be determined to be not prudent:
    (a) The species is threatened by taking or other human activity and 
identification of critical habitat can be expected to increase the 
degree of such threat to the species;
    (b) The present or threatened destruction, modification, or 
curtailment of a species' habitat or range is not a threat to the 
species, or threats to the species' habitat stem solely from causes 
that cannot be addressed through management actions resulting from 
consultations under section 7(a)(2) of the Act;
    (c) Areas within the jurisdiction of the United States provide no 
more than negligible conservation value, if any, for a species 
occurring primarily outside the jurisdiction of the United States;
    (d) No areas meet the definition of critical habitat.
    (7) Specific information on:
    (a) The amount and distribution of habitat for all six Central 
Texas mussels;
    (b) What areas, that were occupied at the time of listing and that 
contain the physical or biological features essential to the 
conservation of the species, should be included in the designation and 
why;
    (c) Any additional areas occurring within the range of the species, 
i.e., Anderson, Austin, Bastrop, Bell, Blanco, Brazoria, Brazos, Brown, 
Burleson, Caldwell, Coleman, Colorado, Comal, Concho, Dallas, DeWitt, 
Edwards, Ellis, Falls, Fayette, Fort Bend, Freestone, Gillespie, 
Gonzales, Grimes, Guadalupe, Hays, Henderson, Houston, Kaufman, Kerr, 
Kendall, Kimble, Lampasas, Leon, Llano, Madison, Mason, Matagorda, 
McCulloch, McLennan, Menard, Milam, Mills, Navarro, Palo Pinto, Parker,

[[Page 47918]]

Robertson, Runnels, San Saba, Shackelford, Stephens, Sutton, Tom Green, 
Travis, Throckmorton, Waller, Washington, Victoria, Wharton, and 
Williamson Counties, Texas, that should be included in the designation 
because they (1) are occupied at the time of listing and contain the 
physical or biological features that are essential to the conservation 
of the species and that may require special management considerations, 
or (2) are unoccupied at the time of listing and are essential for the 
conservation of the species;
    (d) Special management considerations or protection that may be 
needed in critical habitat areas we are proposing, including managing 
for the potential effects of climate change; and
    (e) What areas not occupied at the time of listing are essential 
for the conservation of the species. We particularly seek comments:
    (i) Regarding whether occupied areas are inadequate for the 
conservation of the species;
    (ii) Providing specific information that supports the determination 
that unoccupied areas will, with reasonable certainty, contribute to 
the conservation of the species and contain at least one physical or 
biological feature essential to the conservation of the species; and
    (iii) Explaining whether or not unoccupied areas fall within the 
definition of ``habitat'' at 50 CFR 424.02 and why.
    (8) Land use designations and current or planned activities in the 
subject areas and their possible impacts on proposed critical habitat.
    (9) Any probable economic, national security, or other relevant 
impacts of designating any area that may be included in the final 
designation, and the related benefits of including or excluding 
specific areas.
    (10) Information on the extent to which the description of probable 
economic impacts in the draft economic analysis is a reasonable 
estimate of the likely economic impacts and any additional information 
regarding probable economic impacts that we should consider.
    (11) Whether any specific areas we are proposing for critical 
habitat designation should be considered for exclusion under section 
4(b)(2) of the Act, and whether the benefits of potentially excluding 
any specific area outweigh the benefits of including that area under 
section 4(b)(2) of the Act. If you think we should exclude any 
additional areas, please provide credible information regarding the 
existence of a meaningful economic or other relevant impact supporting 
a benefit of exclusion.
    (12) Whether we could improve or modify our approach to designating 
critical habitat in any way to provide for greater public participation 
and understanding, or to better accommodate public concerns and 
comments.
    Please include sufficient information with your submission (such as 
scientific journal articles or other publications) to allow us to 
verify any scientific or commercial information you include.
    Please note that submissions merely stating support for, or 
opposition to, the action under consideration without providing 
supporting information, although noted, will not be considered in 
making a determination, as section 4(b)(1)(A) of the Act directs that 
determinations as to whether any species is an endangered or a 
threatened species must be made ``solely on the basis of the best 
scientific and commercial data available.''
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in ADDRESSES. We request that you 
send comments only by the methods described in ADDRESSES.
    If you submit information via http://www.regulations.gov, your 
entire submission--including any personal identifying information--will 
be posted on the website. If your submission is made via a hardcopy 
that includes personal identifying information, you may request at the 
top of your document that we withhold this information from public 
review. However, we cannot guarantee that we will be able to do so. We 
will post all hardcopy submissions on http://www.regulations.gov.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on http://www.regulations.gov.

Public Hearing

    We have scheduled two public informational meetings and public 
hearings on this proposed rule to list the Central Texas mussels as 
endangered or threatened species with critical habitat. We will hold 
the public informational meetings and public hearings on the date and 
at the times listed above under Public informational meeting and public 
hearing in DATES. We are holding the public informational meetings and 
public hearings via the Zoom online video platform and via 
teleconference so that participants can attend remotely. For security 
purposes, registration is required. To listen and view the meeting and 
hearing via Zoom, listen to the meeting and hearing by telephone, or 
provide oral public comments at the public hearing by Zoom or 
telephone, you must register. For information on how to register, or if 
you encounter problems joining Zoom the day of the meeting, visit 
https://www.fws.gov/southwest/. Registrants will receive the Zoom link 
and the telephone number for the public informational meetings and 
public hearings. If applicable, interested members of the public not 
familiar with the Zoom platform should view the Zoom video tutorials 
(https://support.zoom.us/hc/en-us/articles/206618765-Zoom-video-tutorials) prior to the public informational meetings and public 
hearings.
    The public hearings will provide interested parties an opportunity 
to present verbal testimony (formal, oral comments) regarding this 
proposed rule. While the public informational meetings will be 
opportunities for dialogue with the Service, the public hearings are 
not: They are a forum for accepting formal verbal testimony. In the 
event there is a large attendance, the time allotted for oral 
statements may be limited. Therefore, anyone wishing to make an oral 
statement at the public hearing for the record is encouraged to provide 
a prepared written copy of their statement to us through the Federal 
eRulemaking Portal, or U.S. mail (see ADDRESSES, above). There are no 
limits on the length of written comments submitted to us. Anyone 
wishing to make an oral statement at the public hearings must register 
before the hearing (https://www.fws.gov/southwest/). The use of a 
virtual public hearing is consistent with our regulations at 50 CFR 
424.16(c)(3).

Previous Federal Actions

    Table 1, below, summarizes the petition history and proposed status 
of the Central Texas mussels under the Endangered Species Act. On June 
25, 2007, we received a formal petition dated June 18, 2007, from 
Forest Guardians (now WildEarth Guardians), for 475 species in the 
southwestern United States. The petitioned group of species included 
the Texas fatmucket.
    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 Texas pimpleback, Texas fawnsfoot, 
and false spike.
    On December 15, 2009, we published our 90-day finding that the 
above petitions presented substantial scientific information indicating 
that listing the Texas fatmucket, Texas pimpleback, Texas fawnsfoot, 
and false spike may be warranted (74 FR 66260). As a result of

[[Page 47919]]

the finding, we initiated status reviews for these four species. On 
October 6, 2011, we published a 12-month finding for five Texas 
mussels, including the Texas fatmucket, Texas fawnsfoot, and Texas 
pimpleback, that listing was warranted but precluded by higher priority 
actions, and these species were added to the candidate list (76 FR 
62166). Candidates are those fish, wildlife, and plants for which we 
have on file sufficient information on biological vulnerability and 
threats to support preparation of a listing proposal, but for which 
development of a listing rule is precluded by other higher priority 
listing activities. The Texas fatmucket, Texas fawnsfoot, and Texas 
pimpleback were included in all of our subsequent annual Candidate 
Notices of Review (77 FR 69993, November 21, 2012; 78 FR 70104, 
November 22, 2013; 79 FR 72450, December 5, 2014; 80 FR 80584, December 
24, 2015; 81 FR 87246, December 2, 2016; and 84 FR 54732, October 10, 
2019).
    The distribution of the newly described Guadalupe orb was 
previously fully contained within the distribution of the Texas 
pimpleback. Genetic information received in 2018 (Burlakova et al. 
2018, entire) confirmed that the Guadalupe orb is a separate species 
distinct from the Texas pimpleback, and the Guadalupe orb is now a 
newly described species. Similarly, the Guadalupe fatmucket was split 
from the Texas fatmucket in 2018 (Inoue et al. 2018, entire) and 
described in 2019 (Inoue et al. 2019, in press). As both species were 
part of the original petitioned entities, we evaluated both of these 
new species as well as the four original species in our SSA, and all 
six species are included in this proposed rule.
    This document constitutes our concurrent 12-month warranted 
petition finding for the false spike and proposed listing rule and 
proposed critical habitat rule for all six Central Texas mussel 
species.

                                        Table 1--List of the Petition Findings for the Six Central Texas Mussels
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                                                                                       Petition received
          Scientific name                  Common name            River basins                date           90-day finding date   12-month finding date
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Lampsilis bergmanni................  Guadalupe fatmucket...  Guadalupe.............  Previously included in Texas fatmucket.
                                                                                    --------------------------------------------------------------------
Lampsilis bracteata................  Texas fatmucket.......  Colorado..............  June 25, 2007........  December 15, 2009....  October 6, 2011.
Truncilla macrodon.................  Texas fawnsfoot.......  Trinity, Brazos,        October 15, 2008.....  December 15, 2009....  October 6, 2011.
                                                              Colorado.
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Cyclonaias necki...................  Guadalupe orb.........  Guadalupe.............  Previously included in Texas pimpleback.
                                                                                    --------------------------------------------------------------------
Cyclonaias petrina.................  Texas pimpleback......  Colorado..............  October 15, 2008.....  December 15, 2009....  October 6, 2011.
Fusconaia mitchelli................  False spike...........  Brazos, Colorado,       October 15, 2008.....  December 15, 2009....  This finding.
                                                              Guadalupe.
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I. Proposed Listing Determination

Background

General Mussel Biology

    Freshwater mussels, including the six Central Texas mussels, have a 
complex life history involving parasitic larvae, called glochidia, 
which are wholly dependent on host fish. As freshwater mussels are 
generally sessile (immobile), dispersal is accomplished primarily 
through the behavior of host fish and their tendencies to travel 
upstream and against the current in rivers and streams. Mussels are 
broadcast spawners; males release sperm into the water column, which is 
taken in by the female through the incurrent siphon (the tubular 
structure used to draw water into the body of the mussel). The 
developing larvae remain with the female until they mature and are 
ready for release as glochidia, to attach on the gills, head, or fins 
of fishes (Vaughn and Taylor 1999, p. 913; Barnhart et al. 2008, pp. 
371-373).
    Glochidia die if they fail to find a host fish, attach to the wrong 
species of 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. 599). Successful glochidia encyst 
(enclose in a cyst-like structure) on the host's tissue, draw nutrients 
from the fish, and develop into juvenile mussels (Arey 1932, pp. 214-
215). The glochidia will remain encysted for about a month through a 
transformation to the juvenile stage. Once transformed, the juveniles 
will excyst from the fish and drop to the substrate.
    Freshwater mussel species vary in both onset and duration of 
spawning, how long developing larvae are held in the marsupial gill 
chambers (gills used for holding eggs and glochidia), and which fish 
species serve as hosts. The mechanisms employed by mussel species to 
increase the likelihood of interaction between host fish and glochidia 
vary by species.
    Mussels are generally immobile; their primary opportunity for 
dispersal and movement within the stream comes when glochidia attach to 
a mobile 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). Adult mussels typically remain within the same general 
location where they dropped off (excysted) from their host fish as 
juveniles.
    Host specificity can vary across mussel species, which may have 
specialized or generalized relationships with one or more taxa of fish. 
Mussels have evolved a wide variety of adaptations to facilitate 
transmission of glochidia to host fish including: Display/mantle lures 
mimicking fish or invertebrates; packages of glochidia (conglutinates) 
that mimic worms, insect larvae, larval fish, or fish eggs; and release 
of glochidia in mucous webs that entangle fish (Strayer et al. 2004, p. 
431). Polymorphism (existence of multiple forms) of mantle lures and 
conglutinates frequently exists within mussel populations (Barnhart et 
al. 2008, p. 383), representing important adaptive capacity in terms of 
genetic diversity and ecological representation.

Guadalupe Fatmucket

    The Guadalupe fatmucket (Lampsilis bergmanni) was recently 
discovered to be a separate and distinct species from Texas fatmucket 
(L. bracteata; Inoue et al. 2018, pp. 5-6; Inoue et al. 2019, in 
press), and the Service now recognizes the Guadalupe fatmucket as a new

[[Page 47920]]

species that occurs only in the Guadalupe River basin. Because the 
Guadalupe fatmucket has recently been split from Texas fatmucket, the 
species are very similar, and better information is not yet available, 
we believe the Guadalupe fatmucket has similar habitat needs (headwater 
habitats in gravel or bedrock fissures) and host fish (sunfishes) as 
the Texas fatmucket.
    The Guadalupe fatmucket is a small to medium-sized freshwater 
mussel (to 4 inches (in) (100 millimeters (mm))) that exhibits sexual 
dimorphism and has a yellow-green-tan shell, and is similar in 
appearance to the Texas fatmucket (a more detailed description of the 
Texas fatmucket is found in Howells et al. 2011, pp. 14-16). Related 
species in the genus Lampsilis from the southeast United States reach a 
maximum age of 13-25 years (Haag and Rypel 2010, pp. 4-6).
    Guadalupe fatmucket is currently found in one population, which 
occurs in 54 miles (87 km) of the Guadalupe River basin in Kerr and 
Kendall Counties, Texas (Randklev et al. 2017, p. 4) (table 2; figure 
1). For more information on this population, see the SSA report.

                                 Table 2--Current Guadalupe Fatmucket Population
----------------------------------------------------------------------------------------------------------------
                                                                             Occupied reach
            Population               Streams included         Counties         length (mi     Recent collection
                                                                                  (km))        years (numbers)
----------------------------------------------------------------------------------------------------------------
Guadalupe River..................  Guadalupe River;     Kerr and Kendall            54 (87)  2018 (22), 2019
                                    North Fork,          Co., TX.                             (shells).
                                    Guadalupe River;
                                    Johnson Creek.
----------------------------------------------------------------------------------------------------------------

BILLING CODE 4333-15-P

[[Page 47921]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.025

Texas Fatmucket

    A thorough review of the taxonomy, life history, and ecology of the 
Texas fatmucket is presented in the SSA report. Texas fatmucket has 
been characterized as a rare Texas endemic (Burlakova et al. 2011a, p. 
158) and was originally described as the species Unio bracteatus by 
A.A. Gould in 1855 (p. 228) from the ``Llanos River'' in ``Upper'' 
Texas. The species is currently recognized as Lampsilis bracteata 
(Williams et al. 2017, pp. 35, 39). Recently, individuals that had been 
known as Texas fatmucket in the Guadalupe River basin were found to be 
a new species (Inoue et al. 2019, in press); therefore, the Texas 
fatmucket occurs only in the Colorado River basin.
    The Texas fatmucket is a small to medium-sized freshwater mussel 
(to 4 in (100 mm)) that exhibits sexual dimorphism (males and females 
have different shapes) and has a yellow-

[[Page 47922]]

green-tan shell (Howells et al. 2011, pp. 14-16). For a detailed 
morphological description see Howells et al. 1996 (p. 61) and Howells 
2014 (p. 41).
    Host fishes for Texas fatmucket are members of the Family 
Centrarchidae (sunfishes) including bluegill (Lepomis macrochirus), 
green sunfish (L. cyanellus), Guadalupe bass (Micropterus treculii), 
and largemouth bass (M. salmoides) (Howells 1997, p. 257; Johnson et 
al. 2012, p. 148; Howells 2014, p. 41; Ford and Oliver 2015, p. 4; 
Bonner et al. 2018, p. 9).
    Related species can expel conglutinates (packets of glochidia) and 
are known to use mantle lures (Barnhart et al. 2008, pp. 377, 380) to 
attract sight-feeding fishes that attack and rupture the marsupium 
where the glochidia are held, thereby becoming infested by glochidia. 
These species are long-term brooders (bradytictic), spawning and 
becoming gravid in the fall and releasing glochidia in the spring 
(Barnhart et al. 2008, p. 384).
    Related species in the genus Lampsilis from the southeast United 
States reach a maximum age of 13-25 years (Haag and Rypel 2010; pp. 4-
6). Texas fatmucket occur in firm mud, stable sand, and gravel bottoms, 
in shallow waters, sometimes in bedrock fissures or among roots of bald 
cypress (Taxodium distichum) and other aquatic vegetation (Howells 
2014, p. 41). The species typically occurs in free-flowing rivers but 
can survive in backwater areas, such as in areas upstream of lowhead 
dams (e.g. Llano Park Lake (BioWest, Inc., 2018, pp. 2-3)).
    Texas fatmucket currently occur only in the upper reaches of major 
tributaries within the Colorado River basin (Randklev et al. 2017, p. 
4) in five populations: Lower Elm Creek, upper/middle San Saba River, 
Llano River, Pedernales River, and lower Onion Creek (table 3; figure 
2). Isolated individuals not considered part of larger functioning 
populations have been found in Cherokee Creek, Bluff Creek, and the 
North Llano River. For more information on these populations, see the 
SSA report.

                                  Table 3--Current Texas Fatmucket Populations
----------------------------------------------------------------------------------------------------------------
                                                                             Occupied reach   Recent collection
            Population               Streams included         Counties         length (mi       years (number
                                                                                  (km))           collected)
----------------------------------------------------------------------------------------------------------------
Lower Elm Creek..................  Elm Creek..........  Runnels Co., TX....       12.5 (20)  * 2005
                                                                                             2008 (1)
                                                                                             2019 (1)
Upper/Middle San Saba River......  San Saba River.....  Menard, Mason, San         62 (100)  2016 (29)
                                                         Saba, and                           2017 (87)
                                                         McCulloch Co., TX.                  2017 (71)
Llano River......................  Llano River, South   Kimble, Mason,            127 (204)  2016 (72)
                                    Llano River.         Llano Co., TX.                      2017 (47)
                                                                                             2017 (5)
Pedernales River.................  Pedernales River,    Gillespie, Hays,           79 (127)  2017 (17)
                                    Live Oak Creek.      and Blanco Co., TX.
Lower Onion Creek................  Onion Creek........  Travis Co., TX.....           5 (8)  2010 (3)
                                                                                             2018 (1)
----------------------------------------------------------------------------------------------------------------
* No live animals.


[[Page 47923]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.026

Texas Fawnsfoot

    The Texas fawnsfoot was originally described as Unio macrodon 1859 
from a location near Rutersville, Fayette County, Texas (Lea 1859, pp. 
154-155). Texas fawnsfoot is recognized by the scientific community as 
Truncilla macrodon (Williams et al. 2017, pp. 35, 44).
    Texas fawnsfoot is a small- to medium-sized (2.4 in (60 mm)) mussel 
with an elongate oval shell (Howells 2014, p. 111). For a detailed 
description, see Howells et al. 1996 (p. 143) and Howells 2014 (p. 
111).
    Host fish species are not confirmed for the Texas fawnsfoot, but we 
conclude they use freshwater drum (Aplodinotus grunniens; Howells 2014, 
p. 111), like other Truncilla species occurring in Texas and elsewhere 
(Ford and Oliver 2015, p. 8). Freshwater drum are molluscivorous 
(mollusk-eating) and

[[Page 47924]]

become infested with glochidia when they consume gravid female mussels 
(Barnhart et al. 2008, p. 373). This strategy of host infestation may 
limit population size, as reproductively successful females are 
sacrificed (i.e., eaten by freshwater drum). Related species are 
bradytictic, brooding larvae over the winter instead of releasing them 
immediately (Barnhart et al. 2008, p. 384). Other species in the genus 
Truncilla from the Southeast and Midwest reach a maximum age ranging 
from 8-18 years (Haag and Rypel 2010, pp. 4-6).
    Texas fawnsfoot are found in medium- to large-sized streams and 
rivers with flowing waters and mud, sand, and gravel substrates 
(Howells 2014, p. 111). Adults are most often found in bank habitats 
and occasionally in backwater, riffle, and point bar habitats, with low 
to moderate velocities that appear to function as flow refuges during 
high flow events (Randklev et al. 2017c, p. 137).
    Texas fawnsfoot occurs in the lower reaches of the Colorado and 
Brazos Rivers, and in the Trinity River (Randklev et al. 2017b, p. 4) 
in seven populations: East Fork Trinity River, Middle Trinity River, 
Clear Fork Brazos River, Upper Brazos River, Middle/Lower Brazos River, 
San Saba/Colorado Rivers, and Lower Colorado River (table 4; figure 3). 
Texas fawnsfoot was historically distributed throughout the Colorado 
and Brazos River basins (Howells 2014, pp. 111-112; and reviewed in 
Randklev et al. 2017c, pp. 136-137) and in the Trinity River basin 
(Randklev et al. 2017b, p. 11). Texas fawnsfoot historically occurred 
in, but is now absent from, the Leon River (Popejoy et al. 2016, p. 
477). Randklev et al. (2017c, p. 135) surveyed the Llano, San Saba, and 
Pedernales Rivers and found neither live individuals nor dead shells of 
Texas fawnsfoot. Isolated individuals not considered part of 
functioning populations have been found in the Little River. For more 
information on Texas fawnsfoot populations, see the SSA report.

                                  Table 4--Current Texas Fawnsfoot Populations
----------------------------------------------------------------------------------------------------------------
                                                                                                      Recent
                                                                                  Occupied reach    collection
            Population                 Streams included           Counties          length (mi         years
                                                                                       (km))         (numbers)
----------------------------------------------------------------------------------------------------------------
East Fork Trinity River...........  East Fork Trinity      Kaufman Co., TX......         12 (19)       2017 (40)
                                     River.                                                            2018 (12)
Middle Trinity River..............  Trinity River........  Navarro, Anderson,          140 (225)      2016--2017
                                                            Leon, Houston, and                              (59)
                                                            Madison Co., TX.
Clear Fork Brazos River...........  Clear Fork Brazos      Shackelford and               13 (21)        2010 (1)
                                     River.                 Throckmorton Co., TX.                       2018 (0)
Upper Brazos River................  Brazos River.........  Palo Pinto and Parker        62 (100)       2017 (23)
                                                            Co., TX.
Middle/Lower Brazos River.........  Brazos River.........  McLennan, Falls,            346 (557)      2014 (188)
                                                            Robertson, Milam,                          2017 (28)
                                                            Brazos, Burleson,
                                                            Grimes, Washington,
                                                            Waller, Austin, and
                                                            Fort Bend Co., TX.
San Saba/Colorado Rivers..........  San Saba River,        San Saba and Mills            43 (69)        2017 (0)
                                     Colorado River.        Co., TX.                                    2018 (2)
Lower Colorado River..............  Colorado River.......  Colorado, Wharton,          109 (175)       2010 (52)
                                                            and Matagorda Co.,                         2015 (10)
                                                            TX.                                         2017 (9)
----------------------------------------------------------------------------------------------------------------


[[Page 47925]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.027

Guadalupe Orb

    Burlakova et al. (2018, entire) recently described the Guadalupe 
orb (Cyclonaias necki) from the Guadalupe River basin as a separate 
species distinct from Texas pimpleback. The Guadalupe orb occurs only 
in the Guadalupe basin and is a small-sized mussel with a shell length 
that reaches up to 2.5 in (63 mm) (Burlakova et al. 2018, p. 48). 
Guadalupe orb shells are thinner and more compressed but otherwise 
morphologically similar to the closely related Texas pimpleback. The 
posterior ridge is more distinct and prominent, and the umbo is more 
compressed than in Texas pimpleback (Burlakova et al. 2018, p. 48). 
Individuals collected from the upper Guadalupe River (near Comfort, 
Texas) averaged 1.9 in (48 mm) (Bonner et al. 2018, p. 221). Channel 
catfish, flathead catfish, and tadpole madtom are host fish for the 
Guadalupe

[[Page 47926]]

orb (Dudding et al. 2019, p. 15). Dudding et al. (2019, p. 16) 
cautioned that the apparent clumped distribution of Guadalupe orb (and 
closely related species) in ``strongholds'' could be related to 
observed ongoing declines in native catfishes, including the small and 
rare tadpole madtom, a riffle specialist. The best available 
information leads us to believe that reproduction, ecological 
interactions and habitat requirements of Guadalupe orb are similar to 
those of the closely related Texas pimpleback.
    The Guadalupe orb occurs only in the Guadalupe River basin in two 
separate and isolated populations: The upper Guadalupe River and the 
lower Guadalupe River (table 5; figure 4). An isolated individual not 
considered part of a functioning population has been found in the 
Blanco River, a tributary to the San Marcos River (Johnson et al. 2018, 
p. 7). For more information on these populations, see the SSA report.

                                   Table 5--Current Guadalupe Orb Populations
----------------------------------------------------------------------------------------------------------------
                                                                                                      Recent
                                                                                  Occupied reach    collection
            Population                 Streams included           Counties          length (mi         years
                                                                                       (km))         (numbers)
----------------------------------------------------------------------------------------------------------------
Upper Guadalupe River.............  Guadalupe River......  Kerr, Kendall, and           95 (153)        2013 (1)
                                                            Comal Co., TX.                             2017 (10)
                                                                                                        2018 (2)
Lower Guadalupe River.............  Guadalupe River, San   Caldwell, Guadalupe,        181 (291)       2014-2015
                                     Marcos River.          Gonzales, DeWitt,                              (893)
                                                            and Victoria Co., TX.                      2017 (41)
----------------------------------------------------------------------------------------------------------------


[[Page 47927]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.028

 Texas Pimpleback

    The Texas pimpleback was originally described as Unio petrinus from 
the ``Llanos River'' in ``Upper'' Texas (Gould 1855, p. 228). The 
species is now recognized as Cyclonaias petrina by the scientific 
community (Williams et al. 2017, pp. 35, 37). Burlakova et al. (2018, 
entire) recently described the Guadalupe orb (C. necki) from the 
Guadalupe River basin as a separate species distinct from Texas 
pimpleback. Texas pimpleback is now considered to occur only in the 
Colorado River basin of Texas. Texas pimpleback is a small- to medium-
sized (up to 4 in (103 mm)) mussel with a moderately inflated, yellow, 
brown, or black shell, occasionally with vague green rays or concentric 
blotches (Howells 2014, p. 93).
    Recent laboratory studies of the closely related Guadalupe orb 
suggest that channel catfish (Ictalurus

[[Page 47928]]

punctatus), flathead catfish (Pylodictus olivarus) and tadpole madtom 
(Noturus gyrinus) are host fish for Texas pimpleback (Dudding et al. 
2019, p. 2). Related species have miniature glochidia and use catfish 
as hosts (Barnhart et al. 2008, pp. 373, 379). Additionally, related 
species can also produce conglutinates (Barnhart et al. 2008, p. 376) 
and tend to exhibit short-term brooding (tachytictia; releasing 
glochidia soon after the larvae mature) (Barnhart et al. 2008, p. 384). 
Texas pimpleback are reproductively active between April and August 
(Randklev et al. 2017c, p. 110). Related species live as long as 15-72 
years (Haag and Rypel 2010, p. 10).
    Texas pimpleback occurs in the Colorado River basin in five 
isolated populations: Concho River, Upper San Saba River, Lower San 
Saba River/Colorado River, Llano River, and the Lower Colorado River 
(table 6; figure 5). Only the Lower San Saba and Llano River 
populations are known to be successfully reproducing. Texas pimpleback 
was historically distributed throughout the Colorado River basin 
(Howells 2014, pp. 93-94; reviewed in Randklev et al. 2017, pp. 109-
110). For more information on Texas pimpleback populations, see the SSA 
report.

                                 Table 6-- Current Texas Pimpleback Populations
----------------------------------------------------------------------------------------------------------------
                                                                                                      Recent
                                                                                  Occupied reach    collection
            Population                 Streams included           Counties          length (mi         years
                                                                                       (km))         (numbers)
----------------------------------------------------------------------------------------------------------------
Concho River......................  Concho River.........  Concho Co., TX.......         14 (23)       2008 (47)
                                                                                                        2012 (1)
Upper San Saba River..............  San Saba River.......  Menard Co., TX.......         30 (48)        2017 (1)
Lower San Saba/Colorado Rivers....  San Saba River,        San Saba, McCulloch,        178 (286)      2012 (247)
                                     Colorado River.        Mills, Brown, and                         2014 (481)
                                                            Coleman Co., TX.                           2017 (97)
                                                                                                       2018 (42)
Llano River.......................  Llano River..........  Mason Co., TX........           5 (8)       2012 (10)
                                                                                                        2016 (1)
                                                                                                       2017 (23)
Lower Colorado River..............  Colorado River.......  Colorado and Wharton         98 (158)       2014 (49)
                                                            Co., TX.                                    2017 (8)
                                                                                                       2018 (30)
----------------------------------------------------------------------------------------------------------------


[[Page 47929]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.029

False Spike

    The false spike is native to the Brazos, Colorado, and Guadalupe 
basins in central Texas (Howells 2010, p. 4; Randklev et al. 2017c, p. 
12). It was thought to have historically occurred in the Rio Grande 
based on the presence of fossil and subfossil shells there (Howells 
2010, p. 4), but those specimens have now been attributed to 
Sphenonaias taumilapana Conrad 1855 (no common name; Randklev et al. 
2017c, p. 12; Graf and Cummings 2007, p. 309).
    The false spike was originally described as Unio mitchelli by 
Charles T. Simpson in 1895 from the Guadalupe River in Victoria County, 
Texas (Dall 1896, pp. 5-6). The species has been assigned as 
Quincuncina mitchelli by Turgeon et al. (1988, p. 33) and was 
recognized as such by Howells et al. (1996, p. 127), and it was 
referenced as Quadrula mitchelli by Haag (2012, p.

[[Page 47930]]

71). Finally, it was recognized as Fusconaia mitchelli, its current 
nomenclature, by Pfeiffer et al. (2016, p. 289). False spike is 
considered a valid taxon by the scientific community (Williams et al. 
2017, pp. 35, 39).
    The false spike is a medium-sized freshwater mussel (to 5.2 in (132 
mm)) with a yellow-green to brown or black elongate shell, sometimes 
with greenish rays. For a detailed description see Howells et al. 1996 
(pp. 127-128) and Howells 2014 (p. 85).
    Based on closely related species, false spike likely brood eggs and 
larvae from early spring to late summer and host fish are expected to 
be minnows (family Cyprinidae) (Pfeiffer et al. 2016, p. 287). 
Confirmed host fish for false spike include blacktail shiner 
(Cyprinella venusta) and red shiner (C. lutrensis; Dudding et al. 2019, 
p. 16).
    Related species in the genus Fusconaia from the southeast United 
States are reach a maximum age of 15-51 years (Haag and Rypel 2010, pp. 
4-6). No information on age at maturity currently exists for false 
spike (Howells 2010d, p. 3). In part because of their long lifespan and 
episodic recruitment strategy, populations may be slow to recover from 
disturbance.
    False spike occur in larger creeks and rivers with sand, gravel, or 
cobble substrates, and in areas with slow to moderate flows. The 
species is not known from impoundments, nor from deep waters (Howells 
2014, p. 85).
    False spike was once considered common wherever it was found; 
however, beginning in the early 1970s, the species began to be regarded 
as rare throughout its range, based on collection information (Strecker 
1931, pp. 18-19; Randklev et al. 2017c, p. 13). It was considered to be 
extinct until 2011, when the discovery of seven live false spike in the 
Guadalupe River, near Gonzales, Texas, was the first report of living 
individuals in nearly four decades (Howells 2010d, p. 4; Randklev et 
al. 2011, p. 17). Dudding et al. (2019, pp. 16-17) cautioned that the 
patchy distribution of false spike could be related to host fish 
relationships; that is, because their host fish have a small home 
range, limited dispersal ability, and are sensitive to human impacts, 
distribution of false spike could be limited by access to, and movement 
of, host fish.
    Currently, the false spike occurs in four populations: In the 
Little River and some tributaries (Brazos River basin), the lower San 
Saba and Llano Rivers (Colorado River basin), and in the lower 
Guadalupe River (Guadalupe River Basin) (table 7; figure 6). For more 
information on these populations, see the SSA report. False spike is 
presumed to have been extirpated from the remainder of its historical 
range throughout the Brazos, Colorado, and Guadalupe Basins of central 
Texas (reviewed in Randklev et al. 2017c, pp. 12-13).

                                    Table 7--Current False Spike Populations
----------------------------------------------------------------------------------------------------------------
                                                                                                      Recent
                                                                                  Occupied reach    collection
            Population                 Streams included           Counties          length (mi     years (number
                                                                                       (km))        collected)
----------------------------------------------------------------------------------------------------------------
Little River and tributaries......  Little River.........  Milam and Williamson          41 (66)       2015 (29)
                                    Brushy Creek, San       Co., TX.
                                     Gabriel River.
Lower San Saba River..............  San Saba River.......  San Saba Co., TX.....         42 (67)        2012 (3)
Llano River.......................  Llano River..........  Mason Co., TX........         <1 (~1)        2017 (1)
Lower Guadalupe River.............  Guadalupe River......  Gonzales, DeWitt, and       102 (164)       2014-2015
                                                            Victoria Co., TX.                              (652)
----------------------------------------------------------------------------------------------------------------


[[Page 47931]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.030

BILLING CODE 4333-15-C

Regulatory and Analytical Framework

Regulatory Framework

    Section 4 of the Act (16 U.S.C. 1533) and its implementing 
regulations (50 CFR part 424) set forth the procedures for determining 
whether a species is an ``endangered species'' or a ``threatened 
species.'' The Act defines an endangered species as a species that is 
``in danger of extinction throughout all or a significant portion of 
its range,'' and a threatened species as a species that is ``likely to 
become an endangered species within the foreseeable future throughout 
all or a significant portion of its range.'' The Act requires that we 
determine whether any species is an ``endangered species'' or a 
``threatened species'' because of any of the following factors:

[[Page 47932]]

    (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.
    These factors represent broad categories of natural or human-caused 
actions or conditions that could have an effect on a species' continued 
existence. In evaluating these actions and conditions, we look for 
those that may have a negative effect on individuals of the species, as 
well as other actions or conditions that may ameliorate any negative 
effects or may have positive effects (e.g. conservation measures).
    We use the term ``threat'' to refer in general to actions or 
conditions that are known to or are reasonably likely to negatively 
affect individuals of a species. The term ``threat'' includes actions 
or conditions that have a direct impact on individuals (direct 
impacts), as well as those that affect individuals through alteration 
of their habitat or required resources (stressors). The term ``threat'' 
may encompass--either together or separately--the source of the action 
or condition or the action or condition itself.
    However, the mere identification of any threat(s) does not 
necessarily mean that the species meets the statutory definition of an 
``endangered species'' or a ``threatened species.'' In determining 
whether a species meets either definition, we must evaluate all 
identified threats by considering the expected response by the species, 
and the effects of the threats--in light of those actions and 
conditions that will ameliorate the threats--on an individual, 
population, and species level. We evaluate each threat and its expected 
effects on the species, then analyze the cumulative effect of all of 
the threats on the species as a whole. We also consider the cumulative 
effect of the threats in light of those actions and conditions that 
will have positive effects on the species, such as any existing 
regulatory mechanisms or conservation efforts. The Secretary determines 
whether the species meets the definition of an ``endangered species'' 
or a ``threatened species'' only after conducting this cumulative 
analysis and describing the expected effect on the species now and in 
the foreseeable future.
    The Act does not define the term ``foreseeable future,'' which 
appears in the statutory definition of ``threatened species.'' Our 
implementing regulations at 50 CFR 424.11(d) set forth a framework for 
evaluating the foreseeable future on a case-by-case basis. The term 
foreseeable future extends only so far into the future as the Services 
can reasonably determine that both the future threats and the species' 
responses to those threats are likely. In other words, the foreseeable 
future is the period of time in which we can make reliable predictions. 
``Reliable'' does not mean ``certain''; it means sufficient to provide 
a reasonable degree of confidence in the prediction. Thus, a prediction 
is reliable if it is reasonable to depend on it when making decisions.
    It is not always possible or necessary to define foreseeable future 
as a particular number of years. Analysis of the foreseeable future 
uses the best scientific and commercial data available and should 
consider the timeframes applicable to the relevant threats and to the 
species' likely responses to those threats in view of its life-history 
characteristics. Data that are typically relevant to assessing the 
species' biological response include species-specific factors such as 
lifespan, reproductive rates or productivity, certain behaviors, and 
other demographic factors.

Analytical Framework

    The SSA report documents the results of our comprehensive 
biological status review for the Guadalupe fatmucket, Texas fatmucket, 
Texas fawnsfoot, Guadalupe orb, Texas pimpleback, and false spike, 
including an assessment of the potential stressors to each species. The 
SSA report does not represent a decision by the Service on whether the 
species should be proposed for listing as endangered or threatened 
species under the Act. The SSA report provides the scientific basis 
that informs our regulatory decision, which involves the further 
application of standards within the Act and its implementing 
regulations and policies. The following is a summary of the key results 
and conclusions from the SSA report; the full SSA report can be found 
at Docket No. FWS-R2-ES-2019-0061 on http://www.regulations.gov.
    To assess the viability of the six Central Texas mussels, we used 
the three conservation biology principles of resiliency, redundancy, 
and representation (Shaffer and Stein 2000, pp. 306-310). Briefly, 
resiliency supports the ability of the species to withstand 
environmental and demographic stochasticity (for example, wet or dry, 
warm or cold years), redundancy supports the ability of the species to 
withstand catastrophic events (for example, droughts, large pollution 
events), and representation supports the ability of the species to 
adapt over time to long-term changes in the environment (for example, 
climate changes). In general, the more resilient and redundant a 
species is and the more representation it has, the more likely it is to 
sustain populations over time, even under changing environmental 
conditions. Using these principles, we identified the species' 
ecological requirements for survival and reproduction at the 
individual, population, and species levels, and described the 
beneficial and risk factors influencing the species' viability.
    The SSA process can be categorized into three sequential stages. 
During the first stage, we evaluated individual species' life-history 
needs. The next stage involved an assessment of the historical and 
current condition of the species' demographics and habitat 
characteristics, including an explanation of how the species arrived at 
its current condition. The final stage of the SSA involved making 
predictions about the species' responses to positive and negative 
environmental and anthropogenic influences. This process used the best 
available information to characterize viability as the ability of a 
species to sustain populations in the wild over time. We use this 
information to inform our regulatory decision.

Summary of Biological Status and Threats

    In this discussion, we review the biological condition of the 
species and their resources, and the threats that influence the 
species' current and future conditions, in order to assess the species' 
overall viability and the risks to that viability.
    Using various timeframes and the current and projected future 
resiliency, redundancy, and representation, we describe the species' 
levels of viability over time. For the Central Texas mussels to 
maintain viability, their populations or some portion thereof must be 
resilient. A number of factors influence the resiliency of Central 
Texas mussel populations, including occupied stream length, abundance, 
and recruitment. While some of the six species have life-history 
adaptations that help them tolerate dewatering and other stressors to 
some extent, each of these stressors diminishes the resiliency of 
populations to some degree and especially in combination. Elements of 
the species' habitat that determine whether Central Texas mussel 
populations can grow to maximize habitat occupancy influence those 
factors, thereby increasing the resiliency of populations. These

[[Page 47933]]

resiliency factors and habitat elements are discussed in detail in the 
SSA report and summarized here.

Species Needs

    Occupied Stream Length: Most freshwater mussels, including the 
Central Texas mussel species, are found in aggregations, called mussel 
beds, that vary in size from about 50 to >5,000 square meters (m\2\), 
separated by stream reaches in which mussels are absent or rare (Vaughn 
2012, p. 2). We define a mussel population at a larger scale than a 
single mussel bed; it is the collection of mussel beds within a stream 
reach between which infested host fish may travel, allowing for ebbs 
and flows in mussel bed density and abundance over time throughout the 
entirety of the population's occupied reach. Therefore, resilient 
mussel populations must occupy stream reaches long enough such that 
stochastic events that affect individual mussel beds do not eliminate 
the entire population. Repopulation by infested fish from other mussel 
beds within the reach can allow the population to recover from these 
events. We consider populations extending more than 50 miles (80 
kilometers (km)) to be highly resilient to stochastic events because a 
single event is unlikely to affect the entire population. Populations 
occupying reaches between 20 and 49 river miles (32-79 km) have some 
resiliency to stochastic events, and populations occupying reaches less 
than 20 miles (32 km) have little resiliency. Note that, by definition, 
an extirpated or functionally extirpated population occupies a stream 
length of approximately (or approaching) zero miles (0 km).
    Abundance: Mussel abundance in a given stream reach is a product of 
the number of mussel beds and the density of mussels within those beds. 
For populations of Central Texas mussel species to be healthy (i.e., 
resilient), there must be many mussel beds of sufficient density such 
that local stochastic events do not necessarily eliminate the bed(s), 
allowing the mussel bed and the overall local population within a 
stream reach to recover from any single event. Mussel abundance is 
indicated by the number of individuals found during a sampling event; 
mussel surveys rarely represent a complete census of the population. 
Instead, density is estimated by the number found during a survey event 
using various statistical techniques. Because we do not have population 
estimates for most populations of Central Texas mussels, nor are the 
techniques directly comparable (i.e., same area size searched, similar 
search time, etc.), we used the number of individuals captured as an 
index over time, presuming relatively similar levels of effort. While 
we cannot precisely determine population abundance at the sites using 
these numbers, we are able to determine if the species is dominant at 
the site or rare and examine this over time if those data are 
available.
    Reproduction: Resilient Central Texas mussel populations must also 
be reproducing and recruiting young individuals into the population. 
Population size and abundance reflects previous influences on the 
population and habitat, while reproduction and recruitment reflect 
population trends that may be stable, increasing, or decreasing over 
time. For example, a large, dense mussel population that contains 
mostly old individuals is not likely to remain large and dense into the 
future, as there are few young individuals to sustain the population 
over time (i.e., death rates exceed birth rates and subsequent 
recruitment of reproductive adults resulting in negative population 
growth). Conversely, a population that is less dense but has many young 
and/or gravid individuals may likely grow to a higher density in the 
future (i.e., birth rates and subsequent recruitment of reproductive 
adults exceeds death rates resulting in positive population growth). 
Detection rates of very young juvenile mussels during routine abundance 
and distribution surveys are extremely low due to sampling bias because 
sampling for these species involves tactile searches and mussels <35 mm 
are very difficult to detect (Strayer and Smith 2003, pp. 47-48).
    Evidence of reproduction is demonstrated by repeated captures of 
small-sized individuals (juveniles and subadults near the low end of 
the detectable range size ~35 mm; Randklev et al. 2013, p. 9) over time 
and by observing gravid (with eggs in the marsupium, gills, or gill 
pouches) females during the reproductively active time of year. While 
small-sized mussels and gravid females can be difficult to detect, it 
is important that surveyors attempt to detect them as reproduction and 
subsequent recruitment are important demographic parameters that affect 
growth rates in mussel populations (Berg et al. 2008, pp. 396, 398-399; 
Matter et al. 2013, pp. 122-123, 134-135).

Risk Factors for the Central Texas Mussels

    We reviewed the potential risk factors (i.e., threats, stressors) 
that could be affecting the six Central Texas mussels now and in the 
future. In this proposed rule, we will discuss only those factors in 
detail that could meaningfully impact the status of the species. Those 
risks that are not known to have effects on Central Texas mussel 
populations, such as disease, are not discussed here but are evaluated 
in the SSA report. Many of the threats and risk factors are the same or 
similar for each of the six species. Where the effects are expected to 
be similar, we present one discussion that applies to all six species. 
Where the effects may be unique or different to one species, we will 
address that specifically. The primary risk factors (i.e., threats) 
affecting the status of the Central Texas mussels are: (1) Increased 
fine sediment (Factor A from the Act), (2) changes in water quality 
(Factor A), (3) altered hydrology in the form of inundation (Factor A), 
(4) altered hydrology in the form of loss of flow and scour of 
substrate (Factor A), (5) predation and collection (Factor C), and (6) 
barriers to fish movement (Factor E). These factors are all exacerbated 
by the ongoing and expected effects of climate change. Finally, we also 
reviewed the conservation efforts being undertaken for the species.
Increased Fine Sediment
    Juvenile and adult Central Texas mussels inhabit microsites that 
have abundant interstitial spaces, or small openings in an otherwise 
closed matrix of substrate, created by gravel, cobble, boulders, 
bedrock crevices, tree roots, and other vegetation. Inhabited 
interstitial spaces have some amount of fine sediment (i.e., clay and 
silt) necessary to provide appropriate shelter. However, excessive 
amounts of fine sediments can reduce the number of appropriate 
microsites in an otherwise suitable mussel bed by filling in these 
interstitial spaces and can smother mussels in place. All six species 
of Central Texas mussels generally require stable substrates, and loose 
silt deposits do not generally provide for substrate stability that can 
support mussels. Interstitial spaces provide essential habitat for 
juvenile mussels. Juvenile freshwater mussels burrow into interstitial 
substrates, making them particularly susceptible to degradation of this 
habitat feature. When clogged with sand or silt, interstitial flow may 
become reduced (Brim Box and Mossa 1999, p. 100), thus reducing 
juvenile habitat availability and quality. While adult mussels can be 
physically buried by excessive sediment, ``the main impacts of excess 
sedimentation on unionids (freshwater mussels) are often sublethal'' 
and include interference with feeding mediated by valve closure (Brim 
Box

[[Page 47934]]

and Mossa 1999, p. 101). Many land use activities can result in 
excessive erosion, sediment production, and channel instability, 
including, but not limited to: logging, crop farming, ranching, mining, 
and urbanization (Brim Box and Mossa 1999, p. 102).
    Under a natural flow regime, a stream's sediment load is in 
equilibrium such that as sediments are naturally moved downstream from 
one microsite to another, the amount of sediment in the substrate is 
relatively stable, given that different reaches within a river or 
stream may be aggrading (gaining) or degrading (losing) sediment (Poff 
et al. 1997, pp. 770-772). Current and past human activities result in 
enhanced sedimentation in river systems, and legacy sediment, resulting 
from past land disturbance and reservoir construction, continues to 
persist and influence river processes and sediment dynamics (Wohl 2015, 
p. 31) and these legacy effects can degrade mussel habitats. Fine 
sediments collect on the streambed and in crevices during low flow 
events, and much of the sediment is washed downstream during high flow 
events (also known as cleansing flows) and deposited elsewhere. 
However, increased frequency of low flow events (from groundwater 
extraction, instream surface flow diversions, and drought) combined 
with a decrease in cleansing flows (from reservoir management and 
drought) causes sediment to accumulate. Sediments deposited by large-
scale flooding or other disturbance may persist for several years until 
adequate cleansing flows can redistribute that sediment downstream. 
When water velocity decreases, which can occur from reduced streamflow 
or inundation, water loses its ability to carry sediment in suspension, 
and sediment falls to the substrate, eventually smothering mussels not 
adapted to soft substrates (Watters 2000, p. 263). Sediment 
accumulation can be exacerbated when there is a simultaneous increase 
in the sources of fine sediments in a watershed.
    In the range of the Central Texas mussels, these sources include 
streambank erosion from development, agricultural activities, livestock 
and wildlife grazing and browsing, in-channel disturbances, roads, and 
crossings, among others (Poff et al. 1997, p. 773). In areas with 
ongoing development, runoff can transport substantial amounts of 
sediment from ground disturbance related to construction activities 
with inadequate or absent sedimentation controls. While these 
construction impacts can be transient (lasting only during the 
construction phase), the long-term effects of development are long 
lasting and can result in hydrological alterations as increased 
impervious cover increases runoff and resulting shear stress causes 
streambank instability and additional sedimentation.
    All populations of Central Texas mussels face the risk of fine 
sediment accumulation to varying degrees. Multiple populations of the 
six Central Texas mussel species are experiencing increased 
sedimentation, including in particular the Clear Fork Brazos River 
(Texas fawnsfoot), middle and lower Brazos River (false spike and Texas 
fawnsfoot), and lower Colorado River (Texas pimpleback, Texas 
fawnsfoot). In the future, we expect sediment deposition to continue to 
increase across the range of all six species due to low water levels 
and decreasing frequency of cleansing flows at all populations and for 
longer periods due to climate change and additional human development 
in the watershed.
Changes in Water Quality
    Freshwater mussels and their host fish require water in sufficient 
quantity and quality on a consistent basis to complete their life 
cycles. Urban growth and other anthropogenic activities across Texas 
are placing increased demands on limited freshwater resources that, in 
turn, can have deleterious effects on water quality. Water quality can 
be degraded through contamination or alteration of water chemistry. 
Chemical contaminants are ubiquitous throughout the environment and are 
a major reason for the current declining status of freshwater mussel 
species nationwide (Augspurger et al. 2007, p. 2025). Immature mussels 
(i.e., juveniles and glochidia) are especially sensitive to water 
quality degradation and contaminants (Cope et al. 2008, p. 456, Wang et 
al. 2017, pp. 791-792; Wang et al. 2018, p. 3041).
    Chemicals enter the environment through both point and nonpoint 
source discharges, including hazardous spills, industrial wastewater, 
municipal effluents, and agricultural runoff. These sources contribute 
organic compounds, trace metals, pesticides, and a wide variety of 
newly emerging contaminants (e.g., pharmaceuticals) that comprise some 
85,000 chemicals in commerce today that are released to the aquatic 
environment (Environmental Protection Agency (EPA) 2018, p. 1). The 
extent to which environmental contaminants adversely affect aquatic 
biota can vary depending on many variables such as concentration, 
volume, and timing of the release. Species diversity and abundance 
consistently ranks lower in waters that are polluted or otherwise 
impaired by contaminants. Freshwater mussels are not generally found 
for many miles downstream of municipal wastewater treatment plants 
(Gillis et al. 2017, p. 460; Goudreau et al. 1993, p. 211; Horne and 
McIntosh 1979, p. 119). For example, transplanted common freshwater 
mussels (including threeridge (Amblema plicata) and the nonnative Asian 
clam (Corbicula fluminea) showed reduced growth and survival below a 
wastewater treatment plant (WWTP) outfall relative to sites located 
upstream of the WWTP in Wilbarger Creek (a tributary to the Colorado 
River in Travis County, Texas); water chemistry was altered by the 
wastewater flows at downstream sites, with elevated constituents in the 
water column that included copper, potassium, magnesium, and zinc 
(Duncan and Nobles 2012, p. 8; Nobles and Zhang 2015, p. 11). 
Contaminants released during hazardous spills are also of concern. 
Although spills are relatively short-term localized events, depending 
on the types of substances and volume released, water resources nearby 
can be severely impacted and degraded for years following an incident.
    Ammonia is of particular concern below wastewater treatment plants 
because freshwater mussels are particularly sensitive to increased 
ammonia levels (Augspurger et al. 2003, p. 2569). Elevated 
concentrations of un-ionized ammonia (NH<INF>3</INF>) in the 
interstitial spaces of benthic habitats (>0.2 parts per billion) have 
been implicated in the reproductive failure of other freshwater mussel 
populations (Strayer and Malcom 2012, pp. 1787-1788), and sublethal 
effects (valve closures) have recently been described as total ammonia 
nitrogen approaches 2.0 milligrams per liter (mg/L = ppm; Bonner et al. 
2018, p. 186). Immature mussels (i.e., juveniles and glochidia) are 
especially sensitive to water quality degradation and contaminants, 
including ammonia (Wang et al. 2007, p. 2055). For smooth pimpleback 
(Cyclonaias houstonensis, a species native to central Texas but not 
included in this listing), the revised EPA ammonia benchmarks are 
sufficient to protect from short term effects of ammonia on the 
species' physiological processes (Bonner et al. 2018, p. 151). However, 
the long-term effects of chronic exposure (i.e., years or decades) to 
freshwater mussels has yet to be experimentally investigated.
    Municipal wastewater contains both ionized and un-ionized ammonia, 
and wastewater discharge permits issued by Texas Commission on 
Environmental

[[Page 47935]]

Quality (TCEQ) do not always impose limits on ammonia, particularly for 
smaller volume dischargers. Therefore, at a minimum, concentrations of 
ammonia are likely to be elevated in the immediate mixing zone of some 
WWTP outfalls. To give some insight into the potential scope of WWTP 
related impacts, approximately 480 discharge permits are issued for the 
Brazos River watershed alone from its headwaters above Possum Kingdom 
Lake down to the Gulf of Mexico (TCEQ 2018c, entire). In addition, some 
industrial permits, such as animal processing facilities, have ammonia 
limits in the range of 3 to 4 mg/L or higher, which exceeds levels that 
inhibited growth in juvenile fatmucket (Lampsilis siliquoidea) and 
rainbow mussel (Villosa iris) (Wang et al. 2007, entire). Similar to 
the Brazos River, WWTP outfalls are numerous throughout the ranges of 
the Central Texas mussels.
    An additional type of water quality degradation that affects the 
Central Texas mussels is alteration of water quality parameters such as 
dissolved oxygen, temperature, and salinity levels. Dissolved oxygen 
levels may be reduced from increased nutrient inputs or other sources 
of organic matter that increase the biochemical oxygen demand in the 
water column as microorganisms decompose waste. Organic waste can 
originate from storm water or irrigation runoff or wastewater effluent, 
and juvenile mussels seem to be particularly sensitive to low dissolved 
oxygen (with sublethal effects evident at 2 ppm and lethal effects 
evident at 1.3 ppm; Sparks and Strayer 1998, pp. 132-133). Increased 
water temperature (over 30 [deg]C and approaching 40 [deg]C) from 
climate change and from low flows during drought can exacerbate low 
dissolved oxygen levels in addition to other drought-related effects on 
both juvenile and adult mussels (Sparks and Strayer 1998, pp. 132-133). 
Finally, high salinity concentrations are an additional concern in 
certain watersheds, where dissolved salts can be particularly limiting 
to Central Texas mussels. Upper portions of the Brazos and Colorado 
Rivers, originating from the Texas High Plains, contain saline water, 
sourced from both natural geological formations, and from oil and gas 
development. Salinity in river water is diluted by surface flow and as 
surface flow decreases salt concentrations increase, resulting in 
adverse effects to freshwater mussels. Even low levels of salinity (2-4 
parts per thousand (ppt)) have been demonstrated to have substantial 
negative effects on reproductive success, metabolic rates, and survival 
of freshwater mussels (Blakeslee et al. 2013, p. 2853). Bonner et al. 
(2018, pp. 155-156) suggest that the behavioral response of valve 
closure to high salinity concentrations (>2 ppt) is the likely 
mechanism for reduced metabolic rates, reduced feeding, and reduced 
reproductive success based on reported sublethal effects of salinity >2 
ppt for Texas pimpleback.
    Water quality and quantity are interdependent, so reductions in 
surface flow from drought, instream diversion, and groundwater 
extraction serve to concentrate contaminants by reducing flows that 
would otherwise dilute point and non-point source pollution. For 
example, salinity inherently poses a greater risk to aquatic biota 
under low flow conditions as salinity concentrations and water 
temperatures increase. Drought conditions can place additional 
stressors on stream systems beyond reduced flow by exacerbating 
contaminant-related effects to aquatic biota, including Central Texas 
mussels. Not only can temperature be a biological, physical, and 
chemical stressor, the toxicity of many pollutants to aquatic organisms 
increases at higher temperatures (e.g., ammonia, mercury). We foresee 
threats to water quality increasing into the future as demand and 
competition for limited water resources grows.
Altered Hydrology--Inundation
    Central Texas mussels are adapted to flowing water (lotic habitats) 
rather than standing water (lentic habitats) and require free-flowing 
water to survive. Low flow events (including stream drying) and 
inundation can eliminate habitat appropriate for Central Texas mussels, 
and while these species can survive these events for a short duration, 
populations that experience prolonged drying events or repeated drying 
events will not persist over time.
    Inundation has primarily occurred upstream of dams, both large 
(such as the Highland Lakes on the Colorado River and other major flood 
control and water supply reservoirs) and small (low water crossings and 
diversion dams typical of the tributaries and occurring usually on 
privately owned lands throughout Central Texas). Inundation causes an 
increase in sediment deposition, eliminating the crevices that many 
Central Texas mussel species inhabit. Inundation also includes the 
effects of reservoir releases where frequent variation in surface water 
elevation acts to make habitats unsuitable for Central Texas mussels. 
In large reservoirs, deep water is very cold and often devoid of oxygen 
and necessary nutrients. Cold water (less than 11 [deg]Celsius (C) or 
52 [deg]F (F)) stunts mussel growth and delays or hinders spawning. The 
Central Texas mussels do not tolerate inundation under large 
reservoirs. Further, deep-water reservoirs with bottom release (like 
Canyon Reservoir) can affect water temperatures several miles 
downriver. The water temperature remains below 21.1 [deg]C for the 
first 3.9 miles (6.3 km) of the 13.8-mile (22.2-km) Canyon Reservoir 
tailrace (Texas Parks and Wildlife Department (TPWD) 2007c, p. ii), 
cold enough to support a recreational non-native rainbow and brown 
trout fishery.
    The construction of dams, inundation of reservoirs, and management 
of water releases have significant effects on the natural hydrology of 
a river or stream. For example, dams trap sediment in reservoirs, and 
managed releases typically do not conform to the natural flow regime 
(i.e., higher baseflows, and peak flows of reduced intensity but longer 
duration). Rivers transport not only water but also sediment, which is 
transported mostly as suspended load (held by the water column), and 
most sediment transport occurs during floods as sediment transport 
increases as a power function (greater than linear) of flow (Kondolf 
1997, p. 533). It follows that increased severity of flooding would 
result in greater sediment transport, with important effects on 
substrate stability and benthic habitats for freshwater mussels and 
other organisms dependent on stable benthic habitats. Further, water 
released by dams is usually clear and does not carry a sediment load 
and is considered ``hungry water because the excess energy is typically 
expended on erosion of the channel bed and banks . . . resulting in 
incision (downcutting of the bed) and coarsening of the bed material 
until a new equilibrium is reached'' (Kondolf 1997, p. 535). 
Conversely, depending on how dam releases are conducted, reduced flood 
peaks can lead to accumulations of fine sediment in the river bed 
(i.e., loss of flushing flows, Kondolf 1997, pp. 535, 548).
    Operation of flood-control, water-supply, and recreation reservoirs 
results in altered hydrologic regimes, including an attenuation of both 
high- and low-flow events. Flood-control dams store floodwaters and 
then release them in a controlled manner; this extended release of 
flood waters can result in significant scour and loss of substrates 
that provide mussel habitat. Along with this change in the flow of 
water, sediment dynamics are affected as sediment is trapped above and 
scoured below major impoundments. These changes in water and sediment 
transport

[[Page 47936]]

have negatively affected freshwater mussels and their habitats.
    There are numerous dams throughout the range of Central Texas 
mussels. There are now 27 major reservoirs in the Brazos River basin 
(16 have >50,000 acre-feet of storage) (Brazos River and Associated Bay 
Estuary System Basin and Bay Expert Science Team (BBEST) 2012, p. 33); 
31 major reservoirs in the Colorado River basin, including the Highland 
Lakes (Texas Water Development Board (TWDB) 2018d, p. 1); 9 major 
reservoirs on the Guadalupe River (BBEST 2011b, p. 2.2); and 31 major 
reservoirs in the Trinity River basin (BBEST 2009, p. 10). These 
reservoirs, subsequent inundation, and resulting fragmentation of 
mussel populations has been the primary driver of the current 
distribution of the Central Texas mussels. Additional reservoirs are 
planned for the future, including the Cedar Ridge Reservoir, proposed 
by the City of Abilene on the Clear Fork of the Brazos River near the 
town of Lueders, Texas (83 FR 16061), and more than one reservoir is 
proposed to be built off the main channel of the Lower Colorado River 
in Wharton and Colorado Counties, Texas (Lower Colorado River Authority 
(LCRA) 2018c, p. 1). The Allens Creek Reservoir is proposed for 
construction on Allens Creek near the City of Wallis, to provide water 
supply and storage for the City of Houston (Brazos River Authority 
(BRA) 2018b, p. 1). Water that is planned to be pumped from the Brazos 
River during high flows will be stored and released back into the river 
to meet downstream needs during periods of low flow.
Altered Hydrology--Flow Loss and Scour
    Extreme water levels--both low flows and high flows--threaten 
population persistence of the Central Texas mussels. The effects of 
population losses associated with excessively low flows are compounded 
by population losses associated with excessively high flows. Whereas 
persistent low flow during times of drought results in drying of mussel 
habitats and desiccation of exposed mussels, rapid increases in flows 
associated with large-scale rain events and subsequent flooding results 
in scour of the streambed and physical displacement of mussels and 
appropriate substrates. Appropriately-sized substrates are moved during 
scouring high flow events and mussels are transported downstream to 
inappropriate sites or are buried by inappropriately sized materials. 
The Central Texas mussels are experiencing a repeating cycle of 
alternating droughts and flooding that, in combination with 
hydrological alterations, threatens population persistence.
    Droughts that have occurred in the recent past have led to 
extremely low flows in several Central Texas rivers. Many of these 
rivers have some resiliency to drought because they are spring-fed 
(Colorado River tributaries, Guadalupe River), are very large (lower 
Brazos and Colorado Rivers), or have significant return flows (Trinity 
River), but drought in combination with increased groundwater pumping 
may lead to lower river flows of longer duration than have been 
recorded in the past. Reservoir releases can be managed to some extent 
during drought conditions to prevent complete dewatering below many 
major reservoirs. During the months of July and August 2018, the Clear 
Fork Brazos, Concho, San Saba, Llano, Pedernales, and upper Colorado 
and upper Guadalupe Rivers all had very low flows (U.S. Geological 
Survey (USGS) 2019).
    Streamflow in the Colorado River above the Highland Lakes and 
downstream of the confluence with Concho River has been declining since 
the 1960s as evidenced by annual daily mean streamflow (USGS 2008b, pp. 
812, 814, 848, 870, 878, 880), and overall river discharge for each of 
the rivers can be expected to continue to decline due to increased 
drought as a result of climate change, absent significant return flows. 
There are a few exceptions including the Llano River at Llano (USGS 
2008b, p. 892), Pedernales River at Fredericksburg (USGS 2008b, p. 
896), Onion Creek near Driftwood, and Onion Creek at Highway 183 (flows 
appear to become more erratic, characteristic of a developing 
watershed; USGS 2008b, pp. 930, 946). In the San Saba River, continuing 
or increasing surface and alluvial aquifer groundwater withdrawals in 
combination with drought is likely to result in reduced streamflow, 
affecting mussels in the future (Randklev et al. 2017c, pp. 10-11).
    Flows have declined due to drought in the Brazos River in recent 
years upstream of Lake Whitney (USGS 2008b, pp. 578, 600, 626, 638; BRA 
2018e, p. 6), although baseflows are maintained somewhat due to 
releases from Lake Granbury and other reservoirs in the upper basin 
(USGS 2008b, p. 644; BRA 2018e, p. 6). In the middle Brazos, U.S. Army 
Corps of Engineers (USACE) dams have reduced the magnitude of floods on 
the mainstem of the Brazos River downstream of Lake Whitney (USGS 
2008b, pp. 652, 676 766, 776; BRA 2018e, p. 6), while flows in the 
lower Brazos and Navasota Rivers appear to have higher baseflows due to 
water supply operations in the upper basin that deliver to downstream 
users (USGS 2008b, pp. 754, 766, 776; BRA 2018e, p. 6). Lake Limestone 
releases also appear to be contributing to higher base flows in the 
Lower Brazos (BRA 2018e, p. 6). Flows have declined in the upper 
Guadalupe River (USGS 2008b, pp. 992, 994, 1000, 1018) but appear 
relatively unchanged at Comfort and Spring Branch and in the San Marcos 
River (USGS 2008b, pp. 1004, 1006, 1022), and in the lower Guadalupe 
River (USGS 2008b, pp. 1036, 1040). In the lower sections of the 
Colorado River, lower flows and reduced high flow events are more 
common now decades after major reservoirs were constructed (USGS 2008b, 
pp. 964, 966). In the Trinity River, low flows are higher (elevated 
baseflows) than they were in the past (USGS 2008b, pp. 370, 398, 400, 
430) because of substantial return flows from Dallas area wastewater 
treatment plants.
    Many of the tributary streams (i.e., Concho, San Saba, Llano, and 
Pedernales Rivers) historically received significant groundwater inputs 
from multiple springs associated with the Edwards and other aquifers. 
As spring flows decline due to drought or groundwater lowering from 
pumping, habitat for Central Texas mussels in the tributary streams is 
reduced and could eventually cease to exist (Randklev et al. 2018, pp. 
13-14). While Central Texas mussels may survive short periods of low 
flow, as low flows persist, mussels face oxygen deprivation, increased 
water temperature, increased predation risk, and ultimately stranding, 
all reducing survivorship, reproduction, and recruitment in the 
population.
    Low-flow events lead to increased risk of desiccation (physical 
stranding and drying) and exposure to elevated water temperature and 
other water quality degradations, such as contaminants, as well as to 
predation. For example, sections of the San Saba River, downstream of 
Menard, Texas, experienced very low flows during the summer of 2015, 
which led to dewatering of occupied habitats as evidenced by 
observations of recent dead shell material of Texas pimpleback and 
Texas fatmucket (TPWD 2015, pp. 2-3; described in detail by Randklev et 
al. 2018, entire). Several USGS stream gauges reported very low flows 
during the 2017-2018 water year, including: the Clear Fork of the 
Brazos River, Elm Creek, Concho River at Paint Rock, San Saba River, 
Colorado River at San Saba, Llano River, Pedernales River, and upper 
Guadalupe River (USGS 2018a, entire). Service, TPWD, and Texas

[[Page 47937]]

Department of Transportation (TxDOT) biologists noted in 2017 that at 
one site on the Brazos River near Highbank, Texas, the presence of 42 
dead to fresh dead (with tissue intact) Texas fawnsfoot that likely 
died as a result of recent drought or scouring events (Tidwell 2017, 
entire).
    High flow events lead to increased risk of physical removal, 
transport, and burial (entrainment) of mussels as unstable substrates 
are transported downstream by floodwaters and later redeposited in 
locations that may not be suitable. A site in the lower Colorado River 
near Altair, Texas, suffered significant changes in both mussel 
community structure and bathymetry (measurement of water depths) during 
extensive flooding (and resulting high flows) in August 2017, as a 
result of Hurricane Harvey (Bonner et al. 2018, p. 266). This site 
previously held the highest mussel abundance (Bonner et al. 2018, pp. 
242-243) and represented high-quality habitat within the Colorado River 
basin, prior to the flooding events. Mussel abundance significantly 
decreased by nearly two orders of magnitude (Bonner et al. 2018, p. 
266). This location had two of the Central Texas mussel species (Texas 
fawnsfoot and Texas pimpleback) present during initial surveys in 2017 
(Bonner et al. 2018, p. 242). Widespread flooding was reported in the 
Colorado and Guadalupe River basins of Central Texas in October 2018.
    The distribution of mussel beds and their habitats is affected by 
large floods returning at least once during the typical life span of an 
individual mussel (generally from 3 to 30 years). The presence of flow 
refuges mediates the effects of these floods, as shear stress is 
relatively low in flow refuges and where sediments are relatively 
stable, and individual mussels ``must either tolerate high-frequency 
disturbances or be eliminated, and can colonize areas that are 
infrequently disturbed between events'' (Strayer 1999, pp. 468-469). 
Shear stress and relative substrate stability are limiting to mussel 
abundance and species richness (Randklev et al. 2017a, p. 7), and 
riffle habitats may be more resilient to high flow events than littoral 
(bank) habitats.
    The Central Texas mussels have historically been, and currently 
remain, exposed to extreme hydrological conditions, including severe 
drought leading to dewatering, and heavy rains leading to damaging 
scour events with movement of mussels and substrate (i.e., ``flash 
flooding''). For example, in 2018, over the span of 69 days, the Llano 
River near Llano, Texas, experienced extreme low flows (0.08 cfs on 
August 8, 2018), and extreme high flows leading to severe flooding, 
which resulted in substantial scour of streambed and riparian area 
habitats (278,000 cfs on October 16, 2018) (Llano River Watershed 
Alliance (LRWA) 2019, entire). Prolonged drought followed by severe 
flooding can result in failure and collapse of river banks and 
subsequent sedimentation, as demonstrated by slumping and undercutting 
on the lower Guadalupe River near Cuero, Texas, in 2015 (Giardino and 
Rowley 2016, pp. 70-72), which is occupied by the false spike and 
Guadalupe orb. The usual drought/flood cycle in Central Texas can be 
characterized by long periods of time absent of rain interrupted by 
short periods of heavy rain, resulting in often severe flooding. These 
same patterns led to the development of flood control and storage 
reservoirs throughout Texas in the twentieth century. It follows that, 
given the extreme and variable climate of Central Texas, mussels must 
have life-history strategies and other adaptations that allow them to 
persist by withstanding severe conditions and repopulating during more 
favorable conditions. However, it is also likely that there is a limit 
to how the mussels might respond to increasing variability, frequency, 
and severity of extreme weather events, combined with habitat 
fragmentation and population isolation.
    Sediment deposition may arise from human activities, as well. Sand 
and gravel can be mined from rivers or from adjacent alluvial deposits, 
and instream gravels often require less processing and are thus more 
attractive from a business perspective (Kondolf 1997, p. 541). Instream 
mining directly affects river habitats, and can indirectly affect river 
habitats through channel incision, bed coarsening, and lateral channel 
instability (Kondolf 1997, p. 541). Excavation of pits in or near to 
the channel can create a nickpoint, which can contribute to erosion 
(and mobilization of substrate) associated with head cutting (Kondolf 
1997, p. 541). Off-channel mining of floodplain pits can become 
involved during floods, such that the pits become hydrologically 
connected and thus can affect sediment dynamics in the stream (Kondolf 
1997, p. 545).
Predation and Collection
    Predation on freshwater mussels is a natural phenomenon. Raccoons, 
muskrats, snapping turtles, wading birds, and fish are known to prey 
upon Central Texas mussels. Under natural conditions, the level of 
predation occurring within Central Texas mussel populations is not 
likely to pose a significant risk to any given population. However, 
during periods of low flow, terrestrial predators and wading birds have 
increased access to portions of the river that are otherwise too deep 
under normal flow conditions. High levels of predation during drought 
have been observed on the Llano and San Saba Rivers. As drought and low 
flow are predicted to occur more often and for longer periods due to 
the effects of future climate change, the Hill Country tributaries (of 
the Colorado River) in particular are expected to experience additional 
predation pressure into the future, and this may become especially 
problematic in the Llano and San Saba Rivers. Predation is expected to 
be less of a problem for the lower portions of the mainstem river 
populations because the rivers are significantly larger than the 
tributary streams and Central Texas mussels are less likely to be found 
by predators in exposed or very shallow habitats.
    Certain mussel beds within some populations, due to ease of access, 
are vulnerable to overcollection and vandalism. These areas, primarily 
on the Llano and San Saba Rivers, have well-known and well-documented 
mussel beds that have been sampled repeatedly over the past few years 
by multiple researchers and others for a variety of projects. Given the 
additional stressors aforementioned in this section, these populations 
are being put at additional risk due to over-collection and over-
harvest for scientific needs.
Barriers to Fish Movement
    Central Texas mussels historically colonized new areas through 
movement of infested host fish, as newly metamorphosed juveniles would 
excyst from host fish in new locations. Today, the remaining Central 
Texas mussel populations are significantly isolated due to habitat 
fragmentation by major reservoirs such that recolonization of areas 
previously extirpated is extremely unlikely, if not impossible, due to 
existing dams creating permanent barriers to host fish movement. There 
is currently no opportunity for interaction among any of the extant 
Central Texas mussel populations, as they are isolated from one another 
by major reservoirs.
    The overall distribution of mussels is, in part, a function of host 
fish dispersal (Smith 1985, p. 105). There is limited potential for 
immigration and emigration between populations other than through the 
movement of infected host fish between mussel populations. Small 
populations are more affected by this limited immigration potential 
because they are susceptible to genetic drift, resulting from random 
loss of genetic diversity, and inbreeding

[[Page 47938]]

depression. At the species level, isolated populations that are 
eliminated due to stochastic events cannot be recolonized naturally due 
to barriers to host fish movement, leading to reduced overall 
redundancy and representation.
    Many of the Central Texas mussels' known or assumed primary host 
fish species are known to be common, widespread species in the Central 
Texas river basins. We know that populations of mussels and their host 
fish have become fragmented and isolated over time following the 
construction of major dams and reservoirs throughout Central Texas. We 
do not currently have information demonstrating that the distribution 
of host fish is a factor currently limiting Central Texas mussels 
distribution. However, a recent study suggested that the currently 
restricted distribution of false spike, Guadalupe orb, and other 
related species could be related to declining abundance of their host 
fish, particularly those fish having small home ranges and specialized 
habitat affinities (Dudding et al. 2019, entire). Further research into 
the relationships between each of the Central Texas mussel species and 
their host fish is needed to more fully examine the possible role of 
declining host fish abundance in declining mussel populations.
Effects of Climate Change
    Climate change has been documented to have already taken place, and 
continued greenhouse gas emissions at or above current rates will cause 
further warming (Intergovernmental Panel on Climate Change (IPCC) 2013, 
pp. 11-12). Warming in Texas is expected to be greatest in the summer 
(Maloney et al. 2014, p. 2236). The number of extremely hot days (high 
temperatures exceeding 95 [deg]F) is expected to double by around 2050 
(Kinniburgh et al. 2015, p. 83). Western Texas, including portions of 
the ranges of the Central Texas mussels, is an area expected to show 
greater responsiveness to the effects of climate change (Diffenbaugh et 
al. 2008, p. 3). Changes in stream temperatures are expected to reflect 
changes in air temperature, at a rate of approximately 0.6-0.8 [deg]C 
increase in stream water temperature for every 1 [deg]C increase in air 
temperature (Morrill et al. 2005, pp. 1-2, 15) and with implications 
for temperature-dependent water quality parameters such as dissolved 
oxygen and ammonia toxicity. The Central Texas mussels exist at or near 
a climate and habitat gradient in North America, with the eastern 
United States having more rainfall and higher freshwater mussel 
diversity, and the western United States receiving less rainfall and 
having fewer species of freshwater mussels. As such, it is likely that 
the Central Texas mussels may be particularly vulnerable to future 
climate changes in combination with current and future stressors 
(Burlakova et al. 2011a, pp. 156, 161, 163; Burlakova et al. 2011b, pp. 
395, 403).
    While projected changes to rainfall in Texas are small (U.S. Global 
Change Research Program (USGCRP) 2017, p. 217), higher temperatures 
caused by anthropogenic factors lead to increased soil water deficits 
because of higher rates of evapotranspiration. This is likely to result 
in increasing drought severity in future climate scenarios just as 
``extreme precipitation, one of the controlling factors in flood 
statistics, is observed to have generally increased and is projected to 
continue to do so across the United States in a warming atmosphere'' 
(USGCRP 2017, p. 231). Even if precipitation and groundwater recharge 
remain at current levels, increased groundwater pumping and resultant 
aquifer shortages due to increased temperatures are nearly certain 
(Loaiciga et al. 2000, p. 193; Mace and Wade 2008, pp. 662, 664-665; 
Taylor et al. 2013, p. 325). Higher temperatures are also expected to 
lead to increased evaporative losses from reservoirs, which could 
negatively affect downstream releases and flows (Friedrich et al. 2018, 
p. 167). Effects of climate change, such as air temperature increases 
and an increase in drought frequency and intensity, have been shown to 
be occurring throughout the range of Central Texas mussels (USGCRP 
2017, p. 188; Andreadis and Lettenmaier 2006, p. 3), and these effects 
are expected to exacerbate several of the stressors discussed above, 
such as water temperature and flow loss (Wuebbles et al. 2013, p. 16).
    A recent review of future climate projections for Texas concludes 
that both droughts and floods could become more common in Central Texas 
and projects that years like 2011 (the warmest on record) could be 
commonplace by the year 2100 (Mullens and McPherson 2017, pp. 3, 6). 
This trend toward more frequent drought is attributed to increases in 
hot temperatures, and the number of days at or above 100 [deg]F are 
projected to ``increase in both consecutive events and the total number 
of days'' (Mullens and McPherson 2017, pp. 14-15). Similarly, floods 
are projected to become more common and severe because of increases in 
the magnitude of extreme precipitation (Mullens and McPherson 2017, p. 
20). Recent ``historic'' flooding of the Llano River resulted in the 
transport of high levels of silt and debris to Lake Travis, so much so 
that the City of Austin's ability to treat raw water was affected and 
the City issued a boil water notice and call for water conservation 
(City of Austin 2018c, p. 3)
    In the analysis of the future condition of the Central Texas 
mussels, we considered climate change to be an exacerbating factor, 
contributing to the increase of fine sediments, changes in water 
quality, loss of flowing water, and predation. Due to the effects of 
ongoing climate change (represented by representative concentration 
pathway (RCP) 4.5), we expect the frequency and duration of cleansing 
flows to decrease, leading to the increase in fine sediments at all 
populations. Many populations will experience increased frequency of 
low flows. More extreme climate change projections (RCP 8.5 and beyond) 
lead to further increases in fine sediment within the populations. 
Similarly, as lower water levels concentrate contaminants and cause 
unsuitable temperature and dissolved oxygen levels, we expect water 
quality to decline to some degree in the future. The SSA report 
includes a detailed analysis of the species' responses to both RCP 4.5 
and 8.5.
Conservation Actions and Regulatory Mechanisms
    Since 2011, when three of the Central Texas mussel species became 
candidates for listing under the Endangered Species Act, many agencies, 
non-governmental organizations, and other interested parties have been 
working to develop voluntary agreements with private landowners to 
restore or enhance habitats for fish and wildlife in the region, 
including in the watersheds where Central Texas mussels occur. These 
agreements provide voluntary conservation including upland habitat 
enhancements that will, if executed properly, reduce threats to the 
species while improving in-stream physical habitat and water quality, 
as well as adjacent riparian and upland habitats. Additionally, as many 
as three river authorities are developing (or have already developed) 
conservation plans that may lead to candidate conservation agreements 
with assurances to benefit one or more species of candidate mussels 
(including the Central Texas mussels) in their basins. Because these 
plans and agreements are not yet fully drafted and implemented, we are 
not considering the conservation actions in our evaluation of the 
status of the Central Texas mussels; however, we will evaluate any new 
information on these

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actions prior to making our final listing determination for these 
species.
    Some publicly and privately owned lands in the watersheds occupied 
by Central Texas mussels are protected with conservation easements or 
are otherwise managed to support populations of native fish, wildlife, 
and plant populations. The Natural Resources Conservation Service 
(NRCS), along with the Service and State and local partners, are 
working with private landowners to develop and implement comprehensive 
conservation plans to address soil, water, and wildlife resource 
concerns in the lower Colorado River basin through a Working Lands for 
Wildlife project (NRCS 2019a, entire).
    The Service has been hosting annual mussel research and 
coordination meetings to help manage and monitor scientific collection 
of mussel populations and encourage collaboration among researchers and 
other conservation partners since 2018 (USFWS 2018, p. 1, USFWS 2019a, 
p. 1). Additionally, work is under way to evaluate methods of captive 
propagation for the Central Texas mussel species at the Service's 
hatchery and research facilities (San Marcos Aquatic Research Center, 
Inks Dam National Fish Hatchery, and Uvalde National Fish Hatchery), 
including efforts to collect gravid females from the wild to infest 
host fish (Bonner et al. 2018, pp. 8, 9, 11).

Species Condition

    Here we discuss the current condition of each known population, 
taking into account the risks to those populations that are currently 
occurring, as well as management actions that are currently occurring 
to address those risks. We consider climate change to be currently 
occurring, resulting in changes to the timing and amount of rainfall 
affecting streamflow, increased stream temperatures, and increased 
accumulation of fine sediments. In the SSA report, for each species and 
population, we developed and assigned condition categories for three 
population and three habitat factors that are important for viability 
of each species. The condition scores for each factor were then used to 
determine an overall condition of each population: healthy, moderately 
healthy, unhealthy, or functionally extirpated. These overall 
conditions translate to our presumed probability of persistence of each 
population, with healthy populations having the highest probability of 
persistence over 20 years (greater than 90 percent), moderately healthy 
populations having a probability of persistence that falls between 60 
and 90 percent, and unhealthy populations having the lowest probability 
of persistence (between 10 and 60 percent). Functionally extirpated 
populations are not expected to persist over 20 years or are already 
extirpated.
Guadalupe Fatmucket
    Overall, there is one known remaining population of Guadalupe 
fatmucket, in the Guadalupe River. Historically, Guadalupe fatmucket 
likely occurred through the Guadalupe River basin, but it currently 
only occurs in the upper Guadalupe River in an unhealthy population due 
to low abundance and little evidence of reproduction and recruitment. 
Very few individuals have been found in recent years, and the upper 
Guadalupe River in this reach already experiences very low water 
levels. These low water events are expected to continue into the 
future, and the population will be unlikely to rebound from any 
degraded habitat conditions.
Texas Fatmucket
    Overall, there are five known remaining populations of Texas 
fatmucket, all limited to the headwater reaches of the Colorado River 
and its tributaries (see figure 2, above). Historically, most Texas 
fatmucket populations were likely connected by fish migration 
throughout the Colorado River basin, but due to impoundments and low 
water conditions in the Colorado River and tributaries they are 
currently isolated from one another, and repopulation of extirpated 
locations is unlikely to occur without human assistance. Two of the 
current populations are moderately healthy, two are unhealthy, and one 
is functionally extirpated.
    Lower Elm Creek: The Elm Creek population of Texas fatmucket is 
extremely small and isolated. This population will continue to be 
threatened by excessive sedimentation and deterioration of substrate, 
altered hydrology associated with anthropogenic activities and the 
effects of climate change, and water quality degradation. The poor 
habitat conditions and only a single individual found at this site more 
than a decade ago indicate a population that is unlikely to persist and 
may already be extirpated.
    Upper/Middle San Saba River: The population of Texas fatmucket in 
the upper/middle San Saba River is currently moderately healthy. Most 
of the flows in the Upper San Saba River (in Menard County, Texas) are 
from Edwards Formation springs, where it gains streamflow from 
groundwater except for, and due to a change in the underlying geology, 
a reach that loses flow to the aquifer (called a losing reach) near the 
Menard/Mason County line (LBG-Guyton 2002, p. 3). It is in this losing 
reach where drought effects are especially noticeable, as some flows 
may percolate downward to the aquifer. Much of the middle San Saba 
River below Menard is reported to have gone dry for 10 of the last 16 
years by landowners downstream of Menard (Carollo Engineers 2015, p. 
2). Regardless of the cause, low flows in the San Saba River have 
resulted in significant stream drying, and stranded Central Texas 
mussels have been identified following dewatering as recently as 2015 
near and below the losing reach (TPWD 2015, p. 3). During the 2011-2013 
drought, stream flows in the San Saba River were critically low, such 
that several water rights in Schleicher, Menard, and McCulloch Counties 
were suspended by the Texas Commission on Environmental Quality (TCEQ). 
These very low flow events are expected to continue into the future and 
put the upper/middle San Saba River population of Texas fatmucket at 
risk of extirpation. Even if the locations of Texas fatmucket do not 
become dry, water quality degradation and increased sedimentation 
associated with low flows is expected.
    Llano River: The Llano River population of Texas fatmucket is 
currently moderately healthy, although there has been limited evidence 
that the population is successfully reproducing, and collection of the 
species is frequent at this location. We expect flows to continue to 
decline and the frequency of extreme flow events to increase, leading 
to increased sedimentation and decreased water quality, and scour, and 
the population is expected to decline as a result.
    Pedernales River: The population of Texas fatmucket in the 
Pedernales River is very small and isolated. The Pedernales River is a 
flashy system, which experiences extreme high flow events, especially 
in the lower reaches in the vicinity of Pedernales Falls State Park and 
below. Occasional, intense thunderstorms can dramatically increase 
streamflow and mobilize large amounts of silt and organic debris (LCRA 
2017, p. 82). The continued increasing frequency of high flow events 
combined with the very low abundances in the river result in a 
population that is likely to be extirpated and currently is unhealthy.
    Onion Creek: Only a single live individual of Texas fatmucket has 
been found in Onion Creek since 2010, and we consider this population 
to be

[[Page 47940]]

functionally extirpated with little chance of persistence. The upper 
reaches of Onion Creek frequently go dry, and several privately owned 
low-head in-channel dams currently exist along upper and lower Onion 
Creek, which further provide barriers to fish passage and mussel 
dispersal, preventing recolonization after low water events. Onion 
Creek is in close proximity to the City of Austin, and continued 
development in the watershed is expected to continue to degrade habitat 
conditions.
Texas Fawnsfoot
    There are seven remaining populations of Texas fawnsfoot, in the 
Trinity, Brazos, and Colorado River basins. Historically, Texas 
fawnsfoot occurred throughout each basin with populations connected by 
fish migration within each basin, but due to impoundments and low water 
conditions, they are currently isolated from one another, and 
repopulation of extirpated locations is unlikely to occur without human 
assistance. Four Texas fawnsfoot populations are moderately healthy, 
and three are unhealthy.
    East Fork Trinity River: The Texas fawnsfoot population in the East 
Fork Trinity River occupies a small stream reach (12 mi (19 km)), 
making it especially vulnerable to a single stochastic event such as a 
spill or flood and changes to water quality. Further, no evidence of 
reproduction exists for this population. The population is expected to 
decline as a result of the lack of reproduction. This population is 
small and isolated from the middle and lower Trinity River population 
by unsuitable habitat affected primarily by altered hydrology as flows 
from the Dallas-Fort Worth metro area are too flashy to provide 
suitable habitat for Texas fawnsfoot. Therefore, this population is 
unhealthy.
    Middle Trinity River: Texas fawnsfoot in the Trinity River have 
experienced improved water quality over the past 30 years due to 
advancements in wastewater treatment technology and facilities, and 
streamflows have been subsidized by return flows originating in part 
from other basins, although water quality degradation and sedimentation 
are still of concern. Additionally, the middle Trinity River is a 
relatively long and unobstructed reach of river. While habitat may 
decline, we expect the population of Texas fawnsfoot to persist in the 
middle Trinity River, as we expect that flows will remain within a 
normal range of environmental variation in this reach.
    Clear Fork Brazos River: Texas fawnsfoot in the Clear Fork of the 
Brazos River is very small and isolated. This population likely 
experienced extensive mortality associated with prolonged dewatering 
during the 2011-2013 drought, combined with ambient water quality 
degradation associated with naturally occurring elevated salinity 
levels from the upper reaches of the river. This population is likely 
functionally extirpated, although more survey effort is needed to reach 
a definitive conclusion. Further, the proposed Cedar Ridge Reservoir, 
if constructed, will likely result in significant hydrologic 
alterations, all of which would not be expected to improve the overall 
condition of this population of Texas fawnsfoot.
    Upper Brazos River: The population of Texas fawnsfoot in the Upper 
Brazos River is characterized by low abundances and lack of 
reproduction, and reduced flows associated with continued drought and 
upstream dam operations. Further, water quality degradation associated 
with naturally occurring salinity is expected to continue. This 
population is at risk of extirpation due to its small population size 
and continued poor habitat conditions.
    Middle/Lower Brazos River: The population of Texas fawnsfoot in the 
middle and lower Brazos River occupies a fairly long reach of river 
(346 mi (557 km)) and exhibits evidence of reproduction. The lack of 
major impoundments and diversions in the Brazos River below Waco, 
Texas, benefits this population through maintenance of a relatively 
natural hydrological regime. Even so, Texas fawnsfoot surveys have yet 
to yield the species in numbers that would indicate a healthy 
population, and future habitat degradation from reduced flows, 
increased temperatures, and decreased water quality will likely reduce 
the resiliency of this population.
    Lower San Saba: Texas fawnsfoot in the lower San Saba River are 
found in low abundance with little evidence of reproductive success and 
subsequent recruitment of new individuals to the population. Habitat 
factors are currently unhealthy overall, due primarily to degraded 
substrate conditions caused, in part, by reductions in flowing water 
over time due to a combination of increased water withdrawals and 
drought. We expect this population to become functionally extirpated 
due to lack of water and degradation of substrate.
    Lower Colorado River: The Texas fawnsfoot population in the lower 
Colorado River is expected to remain extant under current conditions, 
as this reach is expected to remain wetted but flowing at reduced 
amounts that reduce available habitat. Despite increasing demands for 
municipal water, we expect that the lower Colorado River will continue 
to provide water associated with priority downstream agricultural and 
industrial water rights. Similar to the lower Brazos River population, 
the Lower Colorado River is vulnerable to reduced flows and associated 
habitat degradation, because the Texas fawnsfoot occurs in bank 
habitats that are likely to become exposed to desiccation, predation, 
and increased water temperatures as river elevations decline while the 
river still flows in its main channel. Over time, we expect flows in 
the lower Colorado River to be reduced, negatively affecting substrate 
quality and water quality (through increased sediment load and water 
temperature) such that reproduction and abundance are negatively 
affected, resulting in overall unhealthy population conditions.
Guadalupe Orb
    There are two remaining populations of the Guadalupe orb, all in 
the Guadalupe River basin. Historically, Guadalupe orb likely occurred 
throughout the basin with populations connected by fish migration, but 
due to impoundments and low water conditions, they are currently 
isolated from one another, and repopulation of extirpated locations is 
unlikely to occur without human assistance. Both of the Guadalupe orb 
populations are moderately healthy.
    Upper Guadalupe River: The Guadalupe orb population in the upper 
Guadalupe River occurs over approximately 95 river miles (153 river 
km), and water quantity and quality are in moderate condition. However, 
the population occurs in low numbers, and there appears to be a lack of 
reproduction; this population is unhealthy and is expected to become 
functionally extirpated in the near future. This stream reach is 
expected to be sensitive to potential changes in groundwater inputs to 
stream flow and thus is vulnerable to ongoing and future hydrological 
alterations that reduce flows during critical conditions, resulting in 
substrate quality degradations as well as water quality degradation.
    San Marcos/Lower Guadalupe Rivers: In the San Marcos and Lower 
Guadalupe River, the Guadalupe orb population currently occupies a 
relatively long stream length, is observed in relatively high 
abundances, and exhibits evidence of reproduction. Significant spring 
complexes contribute substantially to baseflow during dry

[[Page 47941]]

periods in this system and are expected to continue to contribute to 
baseflows for the next 50 years due to conservation measures 
implemented by the Edwards Aquifer Habitat Conservation Plan partners, 
bolstering the resiliency of this population. However, this population 
is subject to extreme high flow events that scour and mobilize the 
substrate, and water quality degradation and sedimentation are threats, 
putting it at risk of decline.
Texas Pimpleback
    There are five remaining Texas pimpleback populations, all in the 
Colorado River basin. Historically, Texas pimpleback likely occurred 
throughout the basin with populations connected by fish migration, but 
due to impoundments and low water conditions, they are currently 
fragmented and isolated from one another and repopulation of extirpated 
locations is unlikely to occur without human assistance. Three of the 
remaining Texas pimpleback populations are unhealthy and are not 
reproducing, and two of the populations are moderately healthy.
    Concho River: The Texas pimpleback population in the Concho River 
is limited by very low levels of flowing water (including periods of 
almost complete dewatering), poor water quality, and poor substrate 
quality associated with excessive sedimentation. The drought of 2011-
2013 resulted in extremely low flows in this river, and only one live 
adult has been found since that time. This population may currently be 
functionally extirpated.
    Middle Colorado/Lower San Saba Rivers: The population of Texas 
pimpleback in the middle Colorado and lower San Saba River is the 
largest known. This population has relatively high abundance but little 
evidence of reproduction, so we expect this population to decline as 
old individuals die and very few young individuals are recruited into 
the reproducing population. The combination of reduced flows, degraded 
water quality, and substrate degradation will reduce the resiliency of 
this population and may cause it to become extirpated.
    Upper San Saba River: Similar to other populations of Texas 
pimpleback, the population in the Upper San Saba River is currently 
unhealthy and does not appear to be reproducing. Regardless of the high 
risk of low water levels, the very small population size and lack of 
reproduction will likely result in the extirpation of this population. 
Because of the losing reach near Hext, Texas, that serves to separate 
the upper and lower San Saba River populations, along with differences 
in substrate, this population is isolated and no longer connected to 
the lower San Saba River population.
    Llano River: The population of Texas pimpleback in the Llano River 
occupies a very short stream length, which is negatively affected by 
substrate degradation during periods of low flows. This population, due 
to ease of access to the location, is especially vulnerable to the 
threat of overcollection and vandalism. The small population size and 
frequency of low water levels, and flooding with scour, cause this 
population to be unhealthy.
    Lower Colorado River: Currently, the population of Texas pimpleback 
in the lower Colorado River is relatively abundant over a long stream 
length. However, because the species is a riffle specialist, the Texas 
pimpleback is especially sensitive to hydrological alterations leading 
to both extreme drying (dewatering) during low flow events, and to 
extreme high flow events leading to scouring of substrate and movement 
of mature individuals to sites that may or may not be appropriate (as 
evidenced by the August 2017 scouring flood event that substantially 
degraded the quality of the Altair Riffle in the lower Colorado River, 
a formerly robust mussel bed). We expect this population to be at risk 
of extirpation due to these extreme flow events.
False Spike
    Overall, there are four known remaining populations of false spike 
(see figure 6, above), comprising less than 10 percent of the species' 
known historical range. Historically, most false spike populations were 
likely connected by fish migration throughout each of the Brazos, 
Colorado, and Guadalupe river basins, but due to impoundments they are 
currently fragmented and isolated from one another and repopulation of 
extirpated locations is unlikely to occur without human assistance. 
Based on our analysis as described in the SSA Report, one population is 
moderately healthy, and three are unhealthy.
    Little River and tributaries: The Little River population is 
considered to have low resiliency currently due to the small size of 
the population. Development in the watershed has reduced water quality 
and substrate conditions currently, and habitat factors are expected to 
continue to decline because of alterations to flows and water quality 
associated primarily with increasing development in the watershed as 
the Austin-Round Rock (Texas) metropolitan area continues to expand. 
Low water levels remain a concern that is mediated somewhat by the 
likelihood that enhanced return flows associated with the development 
and use of alternative water supplies will bolster base flows somewhat. 
The small size of the population combined with continued habitat 
degradation put this population at high risk of extirpation.
    Lower San Saba River: The lower San Saba River population is 
currently small and isolated and therefore has low resiliency. The 
population has low abundance, and a lack of reproduction and subsequent 
recruitment, and we expect it to become functionally extirpated in the 
next 10 years. Future degradation of habitat factors is expected as 
flows continue to be diminished, most notably by altered precipitation 
patterns (that result in dewatering droughts and scouring floods) 
combined with enhanced evaporative demands and anthropogenic 
withdrawals to support existing and future demands for municipal and 
agricultural water.
    Llano River: The Llano River population is currently very small and 
isolated and therefore has low resiliency. The population occupies an 
extremely small area, and degradation of habitat is expected to 
continue as flows continue to decline due to altered precipitation 
patterns (dewatering droughts and scouring floods) combined with 
enhanced evaporative demands and anthropogenic withdrawals to support 
existing and future demands for municipal and agricultural water. 
Further, this population is well known and easy to access and therefore 
has experienced high collection pressure in recent years, and the 
population has not shown recent evidence of reproduction. Therefore, we 
expect the population to become extirpated.
    Lower Guadalupe River: The lower Guadalupe River population of 
false spike is the largest population of the species and the most 
resilient. This population has fairly high abundance over a long reach, 
and flow protections afforded by the Edwards Aquifer Habitat 
Conservation Plan have contributed substantially to the resiliency of 
this population by sustaining base flows above critical levels. 
However, despite these base flow protections, this population remains 
vulnerable to changes in water quality, sedimentation, and extreme high 
flow events, such as from hurricanes or other strong storms, which 
scour and deplete mussel beds (Strayer 1999, pp. 468-469). Overall, 
this population is moderately healthy.
    We note that, by using the SSA framework to guide our analysis of 
the scientific information documented in

[[Page 47942]]

the SSA report, we have not only analyzed individual effects on the 
species, but we have also analyzed their potential cumulative effects. 
We incorporate the cumulative effects into our SSA analysis when we 
characterize the current and future condition of the species. Our 
assessment of the current and future conditions encompasses and 
incorporates the threats individually and cumulatively. Our current and 
future condition assessment is iterative because it accumulates and 
evaluates the effects of all the factors that may be influencing the 
species, including threats and conservation efforts. Because the SSA 
framework considers not just the presence of the factors, but to what 
degree they collectively influence risk to the entire species, our 
assessment integrates the cumulative effects of the factors and 
replaces a standalone cumulative effects analysis.

Determination of Status

    Section 4 of the Act (16 U.S.C. 1533) and its implementing 
regulations (50 CFR part 424) set forth the procedures for determining 
whether a species meets the definition of ``endangered species'' or 
``threatened species.'' The Act defines an ``endangered species'' as a 
species that is ``in danger of extinction throughout all or a 
significant portion of its range,'' and a ``threatened species'' as a 
species that is ``likely to become an endangered species within the 
foreseeable future throughout all or a significant portion of its 
range.'' The Act requires that we determine whether a species meets the 
definition of ``endangered species'' or ``threatened species'' because 
of any of the following 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.

Status Throughout All of Its Range

    After evaluating threats to the six Central Texas mussel species 
and assessing the cumulative effect of the threats under the section 
4(a)(1) factors, we found that all six species of Central Texas mussels 
have declined significantly in overall distribution and abundance. At 
present, most of the known populations exist in very low abundances and 
show limited evidence of recruitment. Furthermore, existing available 
habitats are reduced in quality and quantity, relative to historical 
conditions. Our analysis revealed five primary threats that caused 
these declines and pose a meaningful risk to the viability of the 
species. These threats are primarily related to habitat changes (Factor 
A from the Act): The accumulation of fine sediments, altered hydrology, 
and impairment of water quality, all of which are exacerbated by the 
effects of climate change. Predation and collection (Factor C) are also 
affecting those populations already experiencing low stream flow, and 
barriers to fish movement (Factor E) limit dispersal and prevent 
recolonization after stochastic events.
    Because of historic and ongoing habitat destruction and 
fragmentation, remaining Central Texas mussel populations are now 
fragmented and isolated from one another, interrupting the once 
functional metapopulation dynamic that historically made mussel 
populations robust and very resilient to change. The existing 
fragmented and isolated mussel populations are largely in a state of 
chronic degradation due to a number of historical and ongoing stressors 
affecting flows, water quality, sedimentation, and substrate quality. 
Given the high risk of catastrophic events including droughts and 
floods, both of which are exacerbated by climate change, many Central 
Texas mussel populations are at a high risk of extirpation.
    Beginning around the turn of the twentieth century until 1970, over 
100 major dams had been constructed, creating reservoirs across Texas, 
including several reservoirs in the Brazos and Trinity basins, the 
chain of Highland Lakes on the Lower Colorado River, the Guadalupe 
Valley Hydroelectric Project, and the Canyon Reservoir on the Guadalupe 
River (Dowell 1964, pp. 3-8). The inundation and subsequent altered 
hydrology and sediment dynamics associated with operation of these 
flood-control, hydropower, and municipal water supply reservoirs have 
resulted in irreversible changes to the natural flow regime of these 
rivers. These changes have re-shaped and fragmented these aquatic 
ecosystems and fish and invertebrate communities, including populations 
of the six species of Central Texas mussels, which all depend on 
natural river flows.
    Water quality has benefited from dramatically improved wastewater 
treatment technology in recent years, such that fish populations have 
rebounded but not completely recovered (Perkin and Bonner 2016, p. 97). 
However, water quality degradation continues to affect mussels and 
their habitats, especially as low flow conditions and excessive 
sedimentation interact to diminish instream habitats, and substrate-
mobilizing and mussel-scouring flood events have become more extreme 
and perhaps more frequent.
    Additionally, while host fish may still be adequately represented 
in contemporary fish assemblages, access to fish hosts can be reduced 
during critical reproductive times by barriers such as the many low-
water crossings and low-head dams that now exist and fragment the 
landscape. Diminished access to host fish leads to reduced reproductive 
success just as barriers to fish passage impede the movement of fish, 
and thus compromise the ability of mussels to disperse and colonize new 
habitats following a disturbance (Schwalb et al. 2013, p. 447).
    Populations of each of the six Central Texas mussels face risks 
from declining water quantity in both large and small river segments. 
Low flows lead to dewatering of habitats and desiccation of 
individuals, elevated water temperatures, and other quality 
degradations, as well as increased exposure to predation. Future higher 
air temperatures, higher rates of evaporation and transpiration, and 
changing precipitation patterns are expected in central Texas (Jiang 
and Yang 2012, pp. 234-239, 242). Future climate changes are expected 
to lead to human responses, such as increased groundwater pumping and 
surface water diversions, associated with increasing demands for and 
decreasing availability of freshwater resources in the State (reviewed 
in Banner et al. 2010, entire). Finally, direct mortality due to 
predation and collection further limits population sizes of those 
populations already experiencing the stressors discussed above.
    These threats, alone or in combination, are expected to cause the 
extirpation of additional mussel populations, further reducing the 
overall redundancy and representation of each of the six species of 
Central Texas mussels. Historically, each species, with a large range 
of interconnected populations (i.e., having metapopulation dynamics), 
would have been resilient to stochastic events such as drought, 
excessive sedimentation, and scouring floods because even if some 
locations were extirpated by such events, they could be recolonized 
over time by dispersal from nearby survivors and facilitated by 
movements by ``affiliate species'' of host fish (Douda et al. 2012, p. 
536). This connectivity across potential habitats would have made for 
highly resilient species overall, as evidenced by the long and 
successful evolutionary history of freshwater mussels as a taxonomic 
group, and in

[[Page 47943]]

North America in particular. However, under present circumstances, 
restoration of that connectivity on a regional scale is not feasible. 
As a consequence of these current conditions, the viability of the six 
species of Central Texas mussels now primarily depends on maintaining 
and improving the remaining isolated populations and potentially 
restoring new populations where feasible.

Guadalupe Fatmucket

    The Guadalupe fatmucket has only one remaining population, and very 
few individuals have been detected and reported in recent years. The 
upper Guadalupe River in this reach already experiences very low water 
levels, putting this population at high risk of extirpation. The 
species has very low viability, with a single population at high risk 
of extirpation, and no additional representation or redundancy. Our 
analysis of the species' current and future conditions, as well as the 
conservation efforts discussed above, show that the Guadalupe fatmucket 
is in danger of extinction throughout all of its range due to the 
severity and immediacy of threats currently impacting the species.

Texas Fatmucket

    Of the five remaining fragmented and isolated populations of Texas 
fatmucket, two are small in abundance and occupied stream length and 
have low to no resiliency (unhealthy), and one population is 
functionally extirpated. The other two current populations are 
moderately healthy. The upper/middle San Saba and Llano River 
populations are larger, with increased abundance and occupied stream 
length, but these populations are vulnerable to stream drying and 
overcollection. These very low flow events are expected to continue 
into the future, and both of these populations of Texas fatmucket are 
at risk of extirpation. Even if the locations of Texas fatmucket do not 
become dry, water quality degradation and increased sedimentation 
associated with low flows is expected. Additionally, the Llano River 
population does not appear to be successfully reproducing, further 
increasing the species' risk of extirpation at this location. The Texas 
fatmucket has no populations that are currently considered healthy. 
Loss of populations at high risk of extirpation leads to low levels of 
redundancy and representation. Overall, these low levels of resiliency, 
redundancy, and representation result in the Texas fatmucket having low 
viability, and the species currently faces a high risk of extinction. 
Our analysis of the species' current and future conditions shows that 
the Texas fatmucket is in danger of extinction throughout all of its 
range due to the severity and immediacy of threats currently impacting 
the species.

Texas Fawnsfoot

    Seven populations of Texas fawnsfoot remain. Four populations are 
moderately healthy, and three are unhealthy or are functionally 
extirpated. Currently, two of the moderately healthy populations are 
not subject to flow declines similar to the remaining populations of 
this species, due to increased flow returns in the Trinity River from 
wastewater treatment facilities and a lack of impoundments on the 
mainstem of the lower Brazos River. In the future, however, as extreme 
flow events become more frequent as rainfall patterns change, and 
increased urbanization results in reduced groundwater levels, we expect 
even these populations to be at an increased risk of extirpation. 
Within 25 to 50 years, even under the best conditions and with 
additional conservation efforts undertaken, given the ongoing effects 
of climate change and human activities on altered hydrology and habitat 
degradation, we expect only one population to be in healthy condition, 
one population to remain in moderately healthy condition, four 
populations to be in unhealthy condition, and one population to become 
functionally extirpated. Given the likelihood of increased climate and 
anthropogenic effects in the foreseeable future, as many as five 
populations are expected to become functionally extirpated, leaving no 
more than three unhealthy populations remaining after 50 years. In the 
future, we anticipate that the Texas fawnsfoot will have reduced 
viability, with no highly resilient populations and limited 
representation and redundancy. Thus, after assessing the best available 
information, we determine that the Texas fawnsfoot is not currently in 
danger of extinction but is likely to become in danger of extinction 
within the foreseeable future throughout all of its range.

Guadalupe Orb

    Only two fragmented and isolated populations of Guadalupe orb 
remain, and one of these populations is functionally extirpated. The 
San Marcos/Lower Guadalupe River population is more resilient but is at 
risk of catastrophic events, such as hurricane flooding, that can scour 
and reduce the abundance and distribution of this population. The 
Guadalupe orb has no populations that are considered healthy. Loss of 
populations at high risk of extirpation leads to low levels of 
redundancy and representation, and results in overall low viability. 
The Guadalupe orb currently faces a high risk of extinction. Our 
analysis of the species' current and future conditions, as well as the 
conservation efforts discussed above, show that the Guadalupe orb is in 
danger of extinction throughout all of its range due to the severity 
and immediacy of threats currently impacting the species.

Texas Pimpleback

    Of the five remaining Texas pimpleback populations, three are 
unhealthy and are not reproducing, and two are moderately healthy. The 
populations that are not reproducing are considered functionally 
extirpated, and the two moderately healthy populations are expected to 
continue to decline. The population in the middle Colorado and lower 
San Saba Rivers has very little evidence of reproduction and is 
therefore likely to decline due to a lack of young individuals joining 
the population as the population ages. The lower Colorado River 
population has very recently experienced an extreme high flow event 
(i.e., associated with Hurricane Harvey flooding in August and 
September of 2017) that vastly changed the substrate and mussel 
composition of much of its length, putting this population at high risk 
of extirpation. The Texas pimpleback has no healthy populations, and 
all populations are expected to continue to decline. Loss of 
populations at high risk of extirpation leads to low levels of 
redundancy and representation. Overall, these low levels of resiliency, 
redundancy, and representation result in the Texas pimpleback having 
low viability, and the species currently faces a high risk of 
extinction. Our analysis of the species' current and future conditions, 
as well as the conservation efforts discussed above, show that the 
Texas pimpleback is in danger of extinction throughout all of its range 
due to the severity and immediacy of threats currently impacting the 
species.

False Spike

    Of the four remaining fragmented and isolated populations of false 
spike, three are small in abundance and occupied stream length, having 
low to no resiliency. The remaining lower Guadalupe River population is 
larger, with increased abundance and occupied stream length; however, 
the risk of extreme high flow events in this reach is high. Therefore, 
the false spike has no populations that are currently considered 
healthy (i.e., highly

[[Page 47944]]

resilient). Loss of populations at high risk of extirpation leads to 
low levels of redundancy (few populations will persist to withstand 
catastrophic events) and representation (little to no ecological or 
genetic diversity will persist to respond to changing environmental 
conditions). The threats identified above are occurring now and are 
expected to continue into the future. Overall, these low levels of 
resiliency, redundancy, and representation result in the false spike 
having low viability, and the species currently faces a high risk of 
extinction. Our analysis of the species' current and future conditions 
demonstrate that the false spike is in danger of extinction throughout 
all of its range due to the severity and immediacy of threats currently 
impacting the species.

Summary of Status Throughout All of Its Range: Guadalupe Fatmucket, 
Texas Fatmucket, Guadalupe Orb, Texas Pimpleback, and False Spike

    Our analysis of the species' current and future conditions, as well 
as the conservation efforts discussed above, show that the Guadalupe 
fatmucket, Texas fatmucket, Guadalupe orb, Texas pimpleback, and false 
spike are in danger of extinction throughout all their ranges due to 
the severity and immediacy of threats currently impacting their 
populations. The risk of extinction is high because the remaining 
fragmented populations have a high risk of extirpation, are isolated, 
and have limited potential for recolonization. We find that a 
threatened species status is not appropriate for Guadalupe fatmucket, 
Texas fatmucket, Guadalupe orb, Texas pimpleback, and false spike 
because of their currently contracted ranges, because all populations 
are fragmented and isolated from one another, because the threats are 
occurring across the entire range of these species, and because the 
threats are ongoing currently and are expected to continue or worsen 
into the future. Because these species are already in danger of 
extinction throughout their ranges, a threatened status is not 
appropriate.

Summary of Status Throughout All of Its Range: Texas Fawnsfoot

    After evaluating threats to the species and assessing the 
cumulative effect of the threats under the section 4(a)(1) factors, we 
find that that Texas fawnsfoot populations will continue to decline 
over the next 25 years so that this species is likely to become in 
danger of extinction throughout all or a significant portion of its 
range within the foreseeable future due to increased frequency of 
drought and extremely high flow events, decreased water quality, and 
decreased substrate suitability. We considered whether the Texas 
fawnsfoot is presently in danger of extinction and determined that 
endangered status is not appropriate. The current conditions as 
assessed in the SSA report show two of the populations in two of the 
representative units are not currently subject to declining flows or 
extreme flow events. While threats are currently acting on the species 
and many of those threats are expected to continue into the future, we 
did not find that the species is currently in danger of extinction 
throughout all of its range. According to our assessment of plausible 
future scenarios in the SSA report, the species is likely to become an 
endangered species in the foreseeable future of 25 years throughout all 
of its range. Twenty-five years encompasses about 5 generations of the 
Texas fawnsfoot; additionally, models of human demand for water (Texas 
Water Development Board 2017, p. 30) and climate change (e.g., 
Kinniburgh et al. 2015, p. 83) project decreased water availability 
over 25 and 50 years, respectively. As a result, we expect increased 
incidences of low flows followed by scour events as well as persistent 
decreased water quality to be occurring in 25 years. Thus, after 
assessing the best available information, we determine that the Texas 
fawnsfoot is not currently in danger of extinction but is likely to 
become in danger of extinction within the foreseeable future throughout 
all of its range.

Status Throughout a Significant Portion of Its Range: Guadalupe 
Fatmucket, Texas Fatmucket, Guadalupe Orb, Texas Pimpleback, and False 
Spike

    Under the Act and our implementing regulations, a species may 
warrant listing if it is in danger of extinction or likely to become so 
in the foreseeable future throughout all or a significant portion of 
its range. We have determined that the Guadalupe fatmucket, Texas 
fatmucket, Guadalupe orb, Texas pimpleback, and false spike are in 
danger of extinction throughout all of their ranges, and accordingly 
did not undertake an analysis of whether there are any significant 
portions of these species' ranges. Because the Guadalupe fatmucket, 
Texas fatmucket, Guadalupe orb, Texas pimpleback, and false spike 
warrant listing as endangered throughout all of their ranges, our 
determination is consistent with the decision in Center for Biological 
Diversity v. Everson, 2020 WL 437289 (D.D.C. Jan. 28, 2020), in which 
the court vacated the aspect of the 2014 Significant Portion of its 
Range Policy that provided the Services do not undertake an analysis of 
significant portions of a species' range if the species warrants 
listing as threatened throughout all of its range.

Status Throughout a Significant Portion of Its Range: Texas Fawnsfoot

    Under the Act and our implementing regulations, a species may 
warrant listing if it is in danger of extinction or likely to become so 
within the foreseeable future throughout all or a significant portion 
of its range. The court in Center for Biological Diversity v. Everson, 
2020 WL 437289 (D.D.C. Jan. 28, 2020) (Center for Biological 
Diversity), vacated the aspect of the 2014 Significant Portion of its 
Range Policy that provided that the Services do not undertake an 
analysis of significant portions of a species' range if the species 
warrants listing as threatened throughout all of its range. Therefore, 
we proceed to evaluating whether the species is endangered in a 
significant portion of its range--that is, whether there is any portion 
of the species' range for which both (1) the portion is significant; 
and, (2) the species is in danger of extinction in that portion. 
Depending on the case, it might be more efficient for us to address the 
``significance'' question or the ``status'' question first. We can 
choose to address either question first. Regardless of which question 
we address first, if we reach a negative answer with respect to the 
first question that we address, we do not need to evaluate the other 
question for that portion of the species' range.
    Following the court's holding in Center for Biological Diversity, 
we now consider whether there are any significant portions of the 
species' range where the species is in danger of extinction now (i.e., 
endangered). In undertaking this analysis for the Texas fawnsfoot, we 
choose to address the status question first--we consider information 
pertaining to the geographic distribution of both the species and the 
threats that the species faces to identify any portions of the range 
where the species is endangered.
    We considered whether any of the threats acting on the species are 
geographically concentrated in any portion of the range at a 
biologically meaningful scale. We examined the following threats 
throughout the range of the species: The accumulation of fine 
sediments, altered hydrology, and impairment of water quality (Factor 
A); predation and collection (Factor C); and barriers to fish movement 
(Factor E).
    We identified a portion of the range of Texas fawnsfoot, the upper 
Brazos

[[Page 47945]]

River (including the populations in the Upper Brazos River and Clear 
Fork Brazos River), that is experiencing a concentration of the 
following threats: Altered hydrology and impaired water quality. 
Although these threats are not unique to this area, they are acting at 
a greater intensity here (e.g., populations higher in the watershed and 
that receive less rainfall are more vulnerable to stream drying because 
there is a smaller volume of water in the river), either individually 
or in combination, than elsewhere in the range. In addition, the small 
sizes of each population, coupled with the current condition 
information in the SSA report suggesting the two populations in this 
area are unhealthy, leads us to find that this portion provides 
substantial information indicating the populations occurring here may 
be in danger of extinction now.
    We then proceeded to the significance question, asking whether 
there is substantial information indicating that this portion of the 
range (i.e., the Upper Brazos River and Clear Fork Brazos River) may be 
significant. As an initial note, the Service's most recent definition 
of ``significant'' within agency policy guidance has been invalidated 
by court order (see Desert Survivors v. Dep't of the Interior, No. 16-
cv-01165 (N.D. Cal. Aug. 24, 2018)). In undertaking this analysis for 
the Texas fawnsfoot, we considered whether the Upper Brazos River 
portion of the species' range may be significant based on its 
biological importance to the overall viability of the Texas fawnsfoot. 
Therefore, for the purposes of this analysis, when considering whether 
this portion may be biologically significant, we considered whether the 
portion may (1) occur in a unique habitat or ecoregion for the species, 
(2) contain high quality or high value habitat relative to the 
remaining portions of the range, for the species' continued viability 
in light of the existing threats, or (3) contain habitat that is 
essential to a specific life-history function for the species and that 
is not found in the other portions (for example, the principal breeding 
ground for the species).
    We evaluated the available information about the portion of the 
range of Texas fawnsfoot that occupies the upper Brazos River in this 
context, assessing its biological significance in terms of these three 
habitat criteria, and determined the information did not substantially 
indicate it may be significant. Texas fawnsfoot in these populations 
exhibit similar habitat and host fish use to Texas fawnsfoot in the 
remainder of its range; thus, there is no unique observable 
environmental usage or behavioral characteristics attributable to just 
this area's populations. The Upper Brazos River is not essential to any 
specific life-history function of the Texas fawnsfoot that is not found 
elsewhere in the range. Further, the habitat in the Upper Brazos River 
does not contain higher quality or higher value than the remainder of 
the species' range. The Upper Brazos River populations have a small 
number of individuals compared to most of the other populations 
throughout the range of Texas fawnsfoot (see Table 4, above). The Clear 
Fork Brazos River population may already be extirpated, and the Upper 
Brazos River population had 23 individuals found in 2017. These 
populations do not interact with other populations of the species.
    Overall, we found no substantial information that would indicate 
the Upper Brazos River may be significant. While this area provides 
some contribution to the species' overall ability to withstand 
catastrophic or stochastic events (redundancy and resiliency, 
respectively), the species has a larger population that occupies a 
larger area downstream in the Brazos River. The best scientific and 
commercial information available indicates that the Upper Brazos River 
population's contribution is very limited in scope due to the small 
population sizes and isolation from other populations. Therefore, 
because we could not answer both the status and significance questions 
in the affirmative, we conclude that the Upper Brazos River portion of 
the range does not warrant further consideration as a significant 
portion of the range.
    We did not identify any portions of the Texas fawnsfoot's range 
where: (1) The portion is significant; and, (2) the species is in 
danger of extinction in that portion. Therefore, we conclude that the 
Texas fawnsfoot is likely to become in danger of extinction within the 
foreseeable future throughout all of its range. This is consistent with 
the courts' holdings in Desert Survivors v. Department of the Interior, 
No. 16-cv-01165-JCS, 2018 WL 4053447 (N.D. Cal. Aug. 24, 2018), and 
Center for Biological Diversity v. Jewell, 248 F. Supp. 3d, 946, 959 
(D. Ariz. 2017).

Determination of Status: Guadalupe Fatmucket, Texas Fatmucket, 
Guadalupe Orb, Texas Pimpleback, and False Spike

    Our review of the best available scientific and commercial 
information indicates that the Guadalupe fatmucket, Texas fatmucket, 
Guadalupe orb, Texas pimpleback, and false spike meet the definition of 
endangered species. Therefore, we propose to list the Guadalupe 
fatmucket, Texas fatmucket, Guadalupe orb, Texas pimpleback, and false 
spike as endangered species in accordance with sections 3(6) and 
4(a)(1) of the Act.

Determination of Status: Texas Fawnsfoot

    Our review of the best available scientific and commercial 
information indicates that the Texas fawnsfoot meets the definition of 
a threatened species. Therefore, we propose to list the Texas fawnsfoot 
as a threatened species in accordance with sections 3(20) and 4(a)(1) 
of the Act.

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened species under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing results in public awareness, and 
conservation by Federal, State, tribal, and local agencies, private 
organizations, and individuals. The Act encourages cooperation with the 
States and other countries and calls for recovery actions to be carried 
out for listed species. The protection required by Federal agencies and 
the prohibitions against certain activities are discussed, in part, 
below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Section 4(f) of the Act calls for the Service to develop and 
implement recovery plans for the conservation of endangered and 
threatened species. The recovery planning process involves the 
identification of actions that are necessary to halt or reverse 
species' decline by addressing the threats to survival and recovery. 
The goal of this process is to restore listed species to a point where 
they are secure, self-sustaining, and functioning components of their 
ecosystems.
    Recovery planning consists of preparing draft and final recovery 
plans, beginning with the development of a recovery outline and making 
it available to the public within 30 days of a final listing 
determination. The recovery outline guides the immediate implementation 
of urgent recovery actions and describes the process to be used to 
develop a recovery plan. Revisions of the plan may be done to

[[Page 47946]]

address continuing or new threats to the species, as new substantive 
information becomes available. The recovery plan also identifies 
recovery criteria for review of when a species may be ready for 
reclassification from endangered to threatened (``downlisting'') or 
removal from protected status (``delisting''), and methods for 
monitoring recovery progress. Recovery plans also establish a framework 
for agencies to coordinate their recovery efforts and provide estimates 
of the cost of implementing recovery tasks. Recovery teams (composed of 
species experts, Federal and State agencies, nongovernmental 
organizations, and stakeholders) are often established to develop 
recovery plans. When completed, the recovery outline, draft recovery 
plan, and the final recovery plan will be available on our website 
(http://www.fws.gov/endangered).
    Implementation of recovery actions generally requires the 
participation of a broad range of partners, including other Federal 
agencies, States, Tribes, nongovernmental organizations, businesses, 
and private landowners. Examples of recovery actions include habitat 
restoration (e.g., restoration of native vegetation), research, captive 
propagation and reintroduction, and outreach and education. The 
recovery of many listed species cannot be accomplished solely on 
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires 
cooperative conservation efforts on private, State, and tribal lands.
    If these species are listed, funding for recovery actions will be 
available from a variety of sources, including Federal budgets, State 
programs, and cost-share grants for non-Federal landowners, the 
academic community, and nongovernmental organizations. In addition, 
pursuant to section 6 of the Act, the State of Texas would be eligible 
for Federal funds to implement management actions that promote the 
protection or recovery of the Central Texas mussels. Information on our 
grant programs that are available to aid species recovery can be found 
at: http://www.fws.gov/grants.
    Although the Central Texas mussels are only proposed for listing 
under the Act at this time, please let us know if you are interested in 
participating in recovery efforts for these species. Additionally, we 
invite you to submit any new information on this species whenever it 
becomes available and any information you may have for recovery 
planning purposes (see FOR FURTHER INFORMATION CONTACT).
    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is proposed or listed as an 
endangered or threatened species and with respect to its critical 
habitat, if any is designated. Regulations implementing this 
interagency cooperation provision of the Act are codified at 50 CFR 
part 402. Section 7(a)(4) of the Act requires Federal agencies to 
confer with the Service on any action that is likely to jeopardize the 
continued existence of a species proposed for listing or result in 
destruction or adverse modification of proposed critical habitat. If a 
species is listed subsequently, section 7(a)(2) of the Act requires 
Federal agencies to ensure that activities they authorize, fund, or 
carry out are not likely to jeopardize the continued existence of the 
species or destroy or adversely modify its critical habitat. If a 
Federal action may affect a listed species or its critical habitat, the 
responsible Federal agency must enter into consultation with the 
Service.
    Federal agency actions within the species' habitat that may require 
conference or consultation or both as described in the preceding 
paragraph include management and any other landscape-altering 
activities on Federal lands administered by the National Park Service.
    The Act and its implementing regulations set forth a series of 
general prohibitions and exceptions that apply to endangered wildlife. 
The prohibitions of section 9(a)(1) of the Act, codified at 50 CFR 
17.21, make it illegal for any person subject to the jurisdiction of 
the United States to take (which includes harass, harm, pursue, hunt, 
shoot, wound, kill, trap, capture, or collect; or to attempt any of 
these) endangered wildlife within the United States or on the high 
seas. In addition, it is unlawful to import; export; deliver, receive, 
carry, transport, or ship in interstate or foreign commerce in the 
course of commercial activity; or sell or offer for sale in interstate 
or foreign commerce any species listed as an endangered species. It is 
also illegal to possess, sell, deliver, carry, transport, or ship any 
such wildlife that has been taken illegally. Certain exceptions apply 
to employees of the Service, the National Marine Fisheries Service, 
other Federal land management agencies, and State conservation 
agencies.
    We may issue permits to carry out otherwise prohibited activities 
involving endangered wildlife under certain circumstances. Regulations 
governing permits are codified at 50 CFR 17.22. With regard to 
endangered wildlife, a permit may be issued for the following purposes: 
For scientific purposes, to enhance the propagation or survival of the 
species, and for incidental take in connection with otherwise lawful 
activities. There are also certain statutory exemptions from the 
prohibitions, which are found in sections 9 and 10 of the Act.
    It is our policy, as published in the Federal Register on July 1, 
1994 (59 FR 34272), to identify to the maximum extent practicable at 
the time a species is listed, those activities that would or would not 
constitute a violation of section 9 of the Act. The intent of this 
policy is to increase public awareness of the effect of a proposed 
listing on proposed and ongoing activities within the range of the 
species proposed for listing. The discussion below regarding protective 
regulations under section 4(d) of the Act for the Texas fawnsfoot 
complies with our policy.
    Based on the best available information, the following actions are 
unlikely to result in a violation of section 9, if these activities are 
carried out in accordance with existing regulations and permit 
requirements; this list is not comprehensive:
    (1) Normal agricultural and silvicultural practices, including 
herbicide and pesticide use, which are carried out in accordance with 
any existing regulations, permit and label requirements, and best 
management practices; and,
    (2) Normal residential landscape activities.
    Based on the best available information, the following activities 
may potentially result in a violation of section 9 of the Act if they 
are not authorized in accordance with applicable law; this list is not 
comprehensive:
    (1) Unauthorized handling or collecting of the species;
    (2) Modification of the channel or water flow of any stream in 
which the Central Texas mussels are known to occur;
    (3) Livestock grazing that results in direct or indirect 
destruction of stream habitat; and
    (4) Discharge of chemicals or fill material into any waters in 
which the Central Texas mussels are known to occur.
    Questions regarding whether specific activities would constitute a 
violation of section 9 of the Act should be directed to the Austin 
Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).

[[Page 47947]]

II. Proposed Rule Issued Under Section 4(d) of the Act

Background

    Section 4(d) of the Act contains two sentences. The first sentence 
states that the ``Secretary shall issue such regulations as he deems 
necessary and advisable to provide for the conservation'' of species 
listed as threatened. The U.S. Supreme Court has noted that statutory 
language like ``necessary and advisable'' demonstrates a large degree 
of deference to the agency (see Webster v. Doe, 486 U.S. 592 (1988)). 
Conservation is defined in the Act to mean ``the use of all methods and 
procedures which are necessary to bring any endangered species or 
threatened species to the point at which the measures provided pursuant 
to [the Act] are no longer necessary.'' Additionally, the second 
sentence of section 4(d) of the Act states that the Secretary ``may by 
regulation prohibit with respect to any threatened species any act 
prohibited under section 9(a)(1), in the case of fish or wildlife, or 
section 9(a)(2), in the case of plants.'' Thus, the combination of the 
two sentences of section 4(d) provides the Secretary with wide latitude 
of discretion to select and promulgate appropriate regulations tailored 
to the specific conservation needs of the threatened species. The 
second sentence grants particularly broad discretion to the Service 
when adopting the prohibitions under section 9.
    The courts have recognized the extent of the Secretary's discretion 
under this standard to develop rules that are appropriate for the 
conservation of a species. For example, courts have upheld rules 
developed under section 4(d) as a valid exercise of agency authority 
where they prohibited take of threatened wildlife, or include a limited 
taking prohibition (see Alsea Valley Alliance v. Lautenbacher, 2007 
U.S. Dist. Lexis 60203 (D. Or. 2007); Washington Environmental Council 
v. National Marine Fisheries Service, 2002 U.S. Dist. Lexis 5432 (W.D. 
Wash. 2002)). Courts have also upheld 4(d) rules that do not address 
all of the threats a species faces (see State of Louisiana v. Verity, 
853 F.2d 322 (5th Cir. 1988)). As noted in the legislative history when 
the Act was initially enacted, ``once an animal is on the threatened 
list, the Secretary has an almost infinite number of options available 
to him with regard to the permitted activities for those species. He 
may, for example, permit taking, but not importation of such species, 
or he may choose to forbid both taking and importation but allow the 
transportation of such species'' (H.R. Rep. No. 412, 93rd Cong., 1st 
Sess. 1973).
    Exercising its authority under section 4(d), the Service has 
developed a proposed rule that is designed to address the Texas 
fawnsfoot's specific threats and conservation needs. Although the 
statute does not require the Service to make a ``necessary and 
advisable'' finding with respect to the adoption of specific 
prohibitions under section 9, we find that this rule as a whole 
satisfies the requirement in section 4(d) of the Act to issue 
regulations deemed necessary and advisable to provide for the 
conservation of the Texas fawnsfoot. As discussed in the Summary of 
Biological Status and Threats section, the Service has concluded that 
the Texas fawnsfoot is likely to become in danger of extinction within 
the foreseeable future primarily due to habitat changes such as the 
accumulation of fine sediments, altered hydrology, and impairment of 
water quality, predation and collection, and barriers to fish movement. 
The provisions of this proposed 4(d) rule would promote conservation of 
the Texas fawnsfoot by encouraging riparian landscape conservation 
while also meeting the conservation needs of Texas fawnsfoot. By 
streamlining those projects that follow best management practices and 
improve instream habitat (such as streambank stabilization, instream 
channel restoration, and upland restoration that improves instream 
habitat), conservation is more likely to occur for Texas fawnsfoot, 
improving the condition of populations in those reaches. The provisions 
of this proposed rule are one of many tools that the Service would use 
to promote the conservation of the Texas fawnsfoot. This proposed 4(d) 
rule would apply only if and when the Service makes final the listing 
of the Texas fawnsfoot as a threatened species.

Provisions of the Proposed 4(d) Rule

    This proposed 4(d) rule would provide for the conservation of the 
Texas fawnsfoot by prohibiting the following activities, except as 
otherwise authorized or permitted: Take, possession, and import/export 
of unlawfully taken specimens.
    As discussed in the Summary of Biological Status and Threats 
(above), habitat loss, predation and collection, and barriers to fish 
movement are affecting the status of the Texas fawnsfoot. A range of 
activities have the potential to impact the Texas fawnsfoot, including: 
Instream construction, water withdrawals, flow releases from upstream 
dams, riparian vegetation removal, improper handling, and wastewater 
treatment facility outflows. Regulating these activities will help 
preserve the species' remaining populations, slow their rate of 
decline, and decrease synergistic, negative effects from other 
stressors.
    Under the Act, ``take'' means to harass, harm, pursue, hunt, shoot, 
wound, kill, trap, capture, or collect, or to attempt to engage in any 
such conduct. Some of these provisions have been further defined in 
regulation at 50 CFR 17.3. Take can result knowingly or otherwise, by 
direct and indirect impacts, intentionally or incidentally. Regulating 
incidental and intentional take will help preserve the species' 
remaining populations, slow their rate of decline, and decrease 
synergistic, negative effects from other stressors.
    We have identified some exceptions to the prohibition on incidental 
and intentional take. Those exceptions include the following 
activities:
    (1) Channel restoration projects that create natural, physically 
stable (streambanks and substrate remaining relatively unchanging over 
time), ecologically functioning streams or stream and wetland systems 
(containing an assemblage of fish, mussels, other invertebrates, and 
plants) that are reconnected with their groundwater aquifers. These 
projects can be accomplished using a variety of methods, but the 
desired outcome is a natural channel with low shear stress (force of 
water moving against the channel); bank heights that enable 
reconnection to the floodplain; a reconnection of surface and 
groundwater systems, resulting in perennial flows in the channel; 
riffles and pools composed of existing soil, rock, and wood instead of 
large imported materials; low compaction of soils within adjacent 
riparian areas; and inclusion of riparian wetlands and woodland 
buffers. This exception to the proposed 4(d) rule for incidental take 
would promote conservation of Texas fawnsfoot by creating stable stream 
channels that are less likely to scour during high flow events, thereby 
increasing population resiliency.
    (2) Bioengineering methods such as streambank stabilization using 
live stakes (live, vegetative cuttings inserted or tamped into the 
ground in a manner that allows the stake to take root and grow), live 
fascines (live branch cuttings, usually willows, bound together into 
long, cigar-shaped bundles), or brush layering (cuttings or branches of 
easily rooted tree species layered between successive lifts of soil 
fill). These methods would not include the sole use of quarried rock 
(rip-rap) or the use of rock baskets or gabion

[[Page 47948]]

structures. In addition, to reduce streambank erosion and sedimentation 
into the stream, work using these bioengineering methods would be 
performed at base flow or low water conditions and when significant 
rainfall is not predicted. Further, streambank stabilization projects 
must keep all equipment out of the stream channels and water. Similar 
to channel restoration projects, this exception to the proposed 4(d) 
rule for incidental take would promote conservation of Texas fawnsfoot 
by creating stable stream channels that are less likely to scour during 
high flow events, thereby increasing population resiliency.
    (3) Soil and water conservation practices and riparian and adjacent 
upland habitat management activities that restore instream habitats for 
the species, restore adjacent riparian habitats that enhance stream 
habitats for the species, stabilize degraded and eroding stream banks 
to limit sedimentation and scour of the species' habitats, and restore 
or enhance nearby upland habitats to limit sedimentation of the 
species' habitats and comply with conservation practice standards and 
specifications and technical guidelines developed by the Natural 
Resources Conservation Service (NRCS) and available in the Field Office 
Technical Guide (FOTG). Soil and water conservation practices and 
aquatic species habitat restoration projects associated with NRCS 
conservation plans are designed to improve water quality and enhance 
fish and aquatic species habitats. This exception to the proposed 4(d) 
rule for incidental take would promote conservation of Texas fawnsfoot 
by creating stable stream channels and reducing sediment inputs to the 
stream, thereby increasing population resiliency.
    (4) Presence or abundance surveys for Texas fawnfoot conducted by 
individuals who successfully complete and show proficiency by passing 
the end-of-course test with a score equal to or greater than 90 
percent, with 100 percent accuracy in identification of mussel species 
listed under the Endangered Species Act, in an approved freshwater 
mussel identification and sampling course (specific to the species and 
basins in which the Texas fawnsfoot is known to occur), such as that 
administered by the Service, State wildlife agency, or qualified 
university experts. Those individuals exercising this exemption should 
provide reports to the Service annually on number, specific location 
(e.g. GPS coordinates), and date of encounter. This exemption does not 
apply if lethal take or collection is anticipated. This exemption only 
applies for 5 years from the date of successful completion of the 
course. This provision of the 4(d) rule for intentional take would 
promote conservation of Texas fawnsfoot by ensuring surveyors are 
proficient at identification of freshwater mussels and would add to the 
knowledge and understanding of the distribution of Texas fawnsfoot 
populations.
    We may issue permits to carry out otherwise prohibited activities, 
including those described above, involving threatened wildlife under 
certain circumstances. Regulations governing permits are codified at 50 
CFR 17.32. With regard to threatened wildlife, a permit may be issued 
for the following purposes: Scientific purposes, to enhance propagation 
or survival, for economic hardship, for zoological exhibition, for 
educational purposes, for incidental taking, or for special purposes 
consistent with the purposes of the Act. There are also certain 
statutory exemptions from the prohibitions, which are found in sections 
9 and 10 of the Act.
    The Service recognizes the special and unique relationship with our 
State natural resource agency partners in contributing to conservation 
of listed species. State agencies often possess scientific data and 
valuable expertise on the status and distribution of endangered, 
threatened, and candidate species of wildlife and plants. State 
agencies, because of their authorities and their close working 
relationships with local governments and landowners, are in a unique 
position to assist the Services in implementing all aspects of the Act. 
In this regard, section 6 of the Act provides that the Services shall 
cooperate to the maximum extent practicable with the States in carrying 
out programs authorized by the Act. Therefore, any qualified employee 
or agent of a State conservation agency that is a party to a 
cooperative agreement with the Service in accordance with section 6(c) 
of the Act, who is designated by his or her agency for such purposes, 
will be able to conduct activities designed to conserve Texas fawnsfoot 
that may result in otherwise prohibited take without additional 
authorization.
    Nothing in this proposed 4(d) rule would change in any way the 
recovery planning provisions of section 4(f) of the Act, the 
consultation requirements under section 7 of the Act, or the ability of 
the Service to enter into partnerships for the management and 
protection of the Texas fawnsfoot. However, interagency cooperation may 
be further streamlined through planned programmatic consultations for 
the species between Federal agencies and the Service. We ask the 
public, particularly State agencies and other interested stakeholders 
that may be affected by the proposed 4(d) rule, to provide comments and 
suggestions regarding additional guidance and methods that the Service 
could provide or use, respectively, to streamline the implementation of 
this proposed 4(d) rule (see Information Requested, above).

III. Proposed Critical Habitat Designation

Background

    Critical habitat is defined in section 3 of the Act as:
    (1) The specific areas within the geographical area occupied by the 
species, at the time it is listed in accordance with the Act, on which 
are found those physical or biological features
    (a) Essential to the conservation of the species, and
    (b) Which may require special management considerations or 
protection; and
    (2) Specific areas outside the geographical area occupied by the 
species at the time it is listed, upon a determination that such areas 
are essential for the conservation of the species.
    Our regulations at 50 CFR 424.02 define the geographical area 
occupied by the species as an area that may generally be delineated 
around species' occurrences, as determined by the Secretary (i.e., 
range). Such areas may include those areas used throughout all or part 
of the species' life cycle, even if not used on a regular basis (e.g., 
migratory corridors, seasonal habitats, and habitats used periodically, 
but not solely by vagrant individuals). Additionally, our regulations 
at 50 CFR 424.02 define the word ``habitat'' as follows: ``for the 
purposes of designating critical habitat only, habitat is the abiotic 
and biotic setting that currently or periodically contains the 
resources and conditions necessary to support one or more life 
processes of a species.''
    Conservation, as defined under section 3 of the Act, means to use 
and the use of all methods and procedures that are necessary to bring 
an endangered or threatened species to the point at which the measures 
provided pursuant to the Act are no longer necessary. Such methods and 
procedures include, but are not limited to, all activities associated 
with scientific resources management such as research, census, law 
enforcement, habitat acquisition and maintenance, propagation, live 
trapping, and

[[Page 47949]]

transplantation, and, in the extraordinary case where population 
pressures within a given ecosystem cannot be otherwise relieved, may 
include regulated taking.
    Critical habitat receives protection under section 7 of the Act 
through the requirement that Federal agencies ensure, in consultation 
with the Service, that any action they authorize, fund, or carry out is 
not likely to result in the destruction or adverse modification of 
critical habitat. The designation of critical habitat does not affect 
land ownership or establish a refuge, wilderness, reserve, preserve, or 
other conservation area. Designation also does not allow the government 
or public to access private lands, nor does designation require 
implementation of restoration, recovery, or enhancement measures by 
non-Federal landowners. Where a landowner requests Federal agency 
funding or authorization for an action that may affect a listed species 
or critical habitat, the Federal agency would be required to consult 
with the Service under section 7(a)(2) of the Act. However, even if the 
Service were to conclude that the proposed activity would result in 
destruction or adverse modification of the critical habitat, the 
Federal action agency and the landowner are not required to abandon the 
proposed activity, or to restore or recover the species; instead, they 
must implement ``reasonable and prudent alternatives'' to avoid 
destruction or adverse modification of critical habitat.
    Under the first prong of the Act's definition of critical habitat, 
areas within the geographical area occupied by the species at the time 
it was listed are included in a critical habitat designation if they 
contain physical or biological features (1) which are essential to the 
conservation of the species and (2) which may require special 
management considerations or protection. For these areas, critical 
habitat designations identify, to the extent known using the best 
scientific and commercial data available, those physical or biological 
features that are essential to the conservation of the species (such as 
space, food, cover, and protected habitat). In identifying those 
physical or biological features that occur in specific occupied areas, 
we focus on the specific features that are essential to support the 
life-history needs of the species, including but not limited to, water 
characteristics, soil type, geological features, prey, vegetation, 
symbiotic species, or other features. A feature may be a single habitat 
characteristic, or a more-complex combination of habitat 
characteristics. Features may include habitat characteristics that 
support ephemeral or dynamic habitat conditions. Features may also be 
expressed in terms relating to principles of conservation biology, such 
as patch size, distribution distances, and connectivity.
    Under the second prong of the Act's definition of critical habitat, 
we can designate critical habitat in areas outside the geographical 
area occupied by the species at the time it is listed, upon a 
determination that such areas are essential for the conservation of the 
species. The implementing regulations at 50 CFR 424.12(b)(2) further 
delineate unoccupied critical habitat by setting out three specific 
parameters: (1) When designating critical habitat, the Secretary will 
first evaluate areas occupied by the species; (2) the Secretary will 
only consider unoccupied areas to be essential where a critical habitat 
designation limited to geographical areas occupied by the species would 
be inadequate to ensure the conservation of the species; and (3) for an 
unoccupied area to be considered essential, the Secretary must 
determine that there is a reasonable certainty both that the area will 
contribute to the conservation of the species and that the area 
contains one or more of those physical or biological features essential 
to the conservation of the species.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific data available. Further, our Policy on 
Information Standards under the Endangered Species Act (published in 
the Federal Register on July 1, 1994 (59 FR 34271)), the Information 
Quality Act (section 515 of the Treasury and General Government 
Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), 
and our associated Information Quality Guidelines, provide criteria, 
establish procedures, and provide guidance to ensure that our decisions 
are based on the best scientific data available. They require our 
biologists, to the extent consistent with the Act and with the use of 
the best scientific data available, to use primary and original sources 
of information as the basis for recommendations to designate critical 
habitat.
    When we are determining which areas should be designated as 
critical habitat, our primary source of information is generally the 
information from the SSA report and information developed during the 
listing process for the species. Additional information sources may 
include any generalized conservation strategy, criteria, or outline 
that may have been developed for the species; the recovery plan for the 
species; articles in peer-reviewed journals; conservation plans 
developed by States and counties; scientific status surveys and 
studies; biological assessments; other unpublished materials; or 
experts' opinions or personal knowledge.
    As the regulatory definition of ``habitat'' reflects (50 CFR 
424.02), habitat is dynamic, and species may move from one area to 
another over time. We recognize that critical habitat designated at a 
particular point in time may not include all of the habitat areas that 
we may later determine are necessary for the recovery of the species. 
For these reasons, a critical habitat designation does not signal that 
habitat outside the designated area is unimportant or may not be needed 
for recovery of the species. Areas that are important to the 
conservation of the species, both inside and outside the critical 
habitat designation, will continue to be subject to: (1) Conservation 
actions implemented under section 7(a)(1) of the Act; (2) regulatory 
protections afforded by the requirement in section 7(a)(2) of the Act 
for Federal agencies to ensure their actions are not likely to 
jeopardize the continued existence of any endangered or threatened 
species; and (3) section 9 of the Act's prohibitions on taking any 
individual of the species, including taking caused by actions that 
affect habitat. Federally funded or permitted projects affecting listed 
species outside their designated critical habitat areas may still 
result in jeopardy findings in some cases. These protections and 
conservation tools will continue to contribute to recovery of these 
species. Similarly, critical habitat designations made on the basis of 
the best available information at the time of designation will not 
control the direction and substance of future recovery plans, habitat 
conservation plans (HCPs), or other species conservation planning 
efforts if new information available at the time of these planning 
efforts calls for a different outcome.

Prudency Determinations

    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12), require that the Secretary shall designate 
critical habitat at the time the species is determined to be an 
endangered or threatened species to the maximum extent prudent and 
determinable. Our regulations (50 CFR 424.12(a)(1)) state that the 
Secretary may, but is not required to, determine that a designation 
would not be prudent in the following circumstances:
    (i) The species is threatened by taking or other human activity and 
identification of critical habitat can be

[[Page 47950]]

expected to increase the degree of such threat to the species;
    (ii) The present or threatened destruction, modification, or 
curtailment of a species' habitat or range is not a threat to the 
species, or threats to the species' habitat stem solely from causes 
that cannot be addressed through management actions resulting from 
consultations under section 7(a)(2) of the Act;
    (iii) Areas within the jurisdiction of the United States provide no 
more than negligible conservation value, if any, for a species 
occurring primarily outside the jurisdiction of the United States;
    (iv) No areas meet the definition of critical habitat; or
    (v) The Secretary otherwise determines that designation of critical 
habitat would not be prudent based on the best scientific data 
available.
    As discussed in the proposed listing rule, above, while collection 
at certain locations has been identified as a threat to certain 
populations of Texas pimpleback, Texas fatmucket, and false spike in 
the Llano River, the location of these populations is well known and 
the identification and mapping of critical habitat is not expected to 
increase the degree of this threat. In our SSA report and proposed 
listing rule for the Central Texas mussels, we determined that the 
present or threatened destruction, modification, or curtailment of 
habitat or range is a threat to the Central Texas mussels and that 
those threats in some way can be addressed by section 7(a)(2) 
consultation measures. The species occurs wholly in the jurisdiction of 
the United States, and we are able to identify areas that meet the 
definition of critical habitat. Therefore, because none of the 
circumstances enumerated in our regulations at 50 CFR 424.12(a)(1) have 
been met and because there are no other circumstances the Secretary has 
identified for which this designation of critical habitat would be not 
prudent, we have determined that the designation of critical habitat is 
prudent for the Central Texas mussels.

Critical Habitat Determinability

    Having determined that designation is prudent, under section 
4(a)(3) of the Act we must find whether critical habitat for the 
Central Texas mussels is determinable. Our regulations at 50 CFR 
424.12(a)(2) state that critical habitat is not determinable when one 
or both of the following situations exist:
    (i) Data sufficient to perform required analyses are lacking, or
    (ii) The biological needs of the species are not sufficiently well 
known to identify any area that meets the definition of ``critical 
habitat.''
    When critical habitat is not determinable, the Act allows the 
Service an additional year to publish a critical habitat designation 
(16 U.S.C. 1533(b)(6)(C)(ii)).
    We reviewed the available information pertaining to the biological 
needs of the species and habitat characteristics where these species 
are located. This and other information represent the best scientific 
data available and led us to conclude that the designation of critical 
habitat is determinable for the Central Texas mussels.

Physical or Biological Features Essential to the Conservation of the 
Species

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12(b), in determining which areas we will designate as 
critical habitat from within the geographical area occupied by the 
species at the time of listing, we consider the physical or biological 
features that are essential to the conservation of the species and that 
may require special management considerations or protection. The 
regulations at 50 CFR 424.02 define ``physical or biological features 
essential to the conservation of the species'' as the features that 
occur in specific areas and that are essential to support the life-
history needs of the species, including but not limited to, water 
characteristics, soil type, geological features, sites, prey, 
vegetation, symbiotic species, or other features. A feature may be a 
single habitat characteristic, or a more complex combination of habitat 
characteristics. Features may include habitat characteristics that 
support ephemeral or dynamic habitat conditions. Features may also be 
expressed in terms relating to principles of conservation biology, such 
as patch size, distribution distances, and connectivity.
    For example, physical features essential to the conservation of the 
species might include gravel of a particular size required for 
spawning, alkali soil for seed germination, protective cover for 
migration, or susceptibility to flooding or fire that maintains 
necessary early-successional habitat characteristics. Biological 
features might include prey species, forage grasses, specific kinds or 
ages of trees for roosting or nesting, symbiotic fungi, or a particular 
level of nonnative species consistent with conservation needs of the 
listed species. The features may also be combinations of habitat 
characteristics and may encompass the relationship between 
characteristics or the necessary amount of a characteristic essential 
to support the life history of the species.
    In considering whether features are essential to the conservation 
of the species, the Service may consider an appropriate quality, 
quantity, and spatial and temporal arrangement of habitat 
characteristics in the context of the life-history needs, condition, 
and status of the species. These characteristics include, but are not 
limited to, space for individual and population growth and for normal 
behavior; food, water, air, light, minerals, or other nutritional or 
physiological requirements; cover or shelter; sites for breeding, 
reproduction, or rearing (or development) of offspring; and habitats 
that are protected from disturbance.
    We derive the specific physical or biological features (PBFs) 
essential for Central Texas mussels from studies of these species' 
habitat, ecology, and life history. The life histories of the six 
Central Texas mussel species are very similar--mussels need flowing 
water, suitable substrate, suitable water quality, flow refuges, and 
appropriate host fish--and so we will discuss their common habitat 
needs and then describe species-specific needs thereafter.

Space for Individual and Population Growth and for Normal Behavior

    Most freshwater mussels, including the Central Texas mussels, are 
found in aggregations, called mussel beds, that vary in size from about 
50 to greater than 5,000 square meters (m\2\), separated by stream 
reaches in which mussels are absent or rare (Vaughn 2012, p. 983). 
Freshwater mussel larvae (called glochidia) are parasites that must 
attach to a host fish. A population incorporates more than one mussel 
bed; it is the collection of mussel beds within a stream reach between 
which infested host fish may travel, allowing for ebbs and flows in 
mussel bed density and abundance over time throughout the population's 
occupied reach. Therefore, resilient mussel populations must occupy 
stream reaches long enough so that stochastic events that affect 
individual mussel beds do not eliminate the entire population. 
Repopulation by infested host fish from other mussel beds within the 
reach can allow the population to recover from these events. Longer 
stream reaches are more likely to support populations of Central Texas 
mussels into the future than shorter stream reaches. Therefore, we 
determine that long stream reaches, over 50 miles (80.5 km), are an 
important component of a riverine system with habitat to

[[Page 47951]]

support all life stages of Central Texas mussels.
    All six species of Central Texas mussels need flowing water for 
survival. They are not found in lakes, reservoirs, or in pools without 
flow, or in areas that are regularly dewatered. River reaches with 
continuous flow support all life stages of Central Texas mussels, while 
those with little or no flow do not. Flow rates needed by each species 
will vary depending on the species and the river size, location, and 
substrate type.
    Additionally, each species of Central Texas mussel has specific 
substrate needs, including gravel/cobble (Guadalupe orb, Texas 
pimpleback, and false spike), gravel/sand/silt (Texas fawnsfoot), and 
bedrock crevices/vegetated runs (Guadalupe fatmucket and Texas 
fatmucket). Except for habitats for Texas fawnsfoot, these locations 
must be relatively free of fine sediments such that the mussels are not 
smothered.

Physiological Requirements: Water Quality Requirements

    Freshwater mussels, as a group, are sensitive to changes in water 
quality parameters such as dissolved oxygen, salinity, ammonia, and 
pollutants. Habitats with appropriate levels of these parameters are 
considered suitable, while those habitats with levels outside of the 
appropriate ranges are considered less suitable. We have used 
information for these six Central Texas mussel species, where 
available, and data from other species when species-specific 
information is not available. Juvenile freshwater mussels are 
particularly susceptible to low dissolved oxygen levels. Juveniles will 
reduce feeding behavior when dissolved oxygen is between 2-4 milligrams 
per liter (mg/L), and mortality has been shown to occur at dissolved 
oxygen levels below 1.3 mg/L. Increased salinity levels may also be 
stressful to freshwater mussels, and additionally, Central Texas 
mussels show signs of stress at salinity levels of 2 ppt or higher 
(Bonner et al. 2018; pp. 155-156).
    The release of pollutants into streams from point and nonpoint 
sources have immediate impacts on water quality conditions and may make 
environments unsuitable for habitation by mussels. Early life stages of 
freshwater mussels are some of the most sensitive organisms of all 
species to ammonia and copper (Naimo 1995, pp. 351-352; Augsperger et 
al. 2007, p. 2025). Additionally, sublethal effects of contaminants 
over time can result in reduced feeding efficiency, reduced growth, 
decreased reproduction, changes in enzyme activity, and behavioral 
changes to all mussel life stages. Even wastewater discharges with low 
ammonia levels have been shown to negatively affect mussel populations.
    Finally, water temperature plays a critical role in the life 
history of freshwater mussels. High water temperatures can cause valve 
closure, reduced reproductive output, and death. The Central Texas 
mussels differ in their optimal temperature ranges, with some species 
much more tolerant of high temperatures than others. Laboratory studies 
investigating the effects of thermal stress on glochidia and adults has 
indicated thermal stress may occur at 29 [deg]C (84.2) [deg]F) (Bonner 
et al. 2018; Khan et al. 2019, entire)).
    Based on the above information, we determine that stream reaches 
with the following water quality parameters are suitable for the 
Guadalupe fatmucket, Texas fatmucket, Texas fawnsfoot, Guadalupe orb, 
Texas pimpleback, and false spike:
    <bullet> Low salinity (less than 2 ppt);
    <bullet> Low total ammonia (less than 0.77 mg/L total ammonia 
nitrogen);
    <bullet> Low levels of contaminants;
    <bullet> Dissolved oxygen levels greater than 2 mg/L;
    <bullet> Water temperatures below 29 [deg]C (84.2 [deg]F).

Sites for Development of Offspring

    As discussed above, freshwater mussel larvae are parasites that 
must attach to a host fish to develop into juvenile mussels. The 
Central Texas mussels use a variety of host fish, many of which are 
widely distributed throughout their ranges. The presence of these fish 
species, either singly or in combination, supports the life-history 
needs of the Central Texas mussels:
    <bullet> False spike: Blacktail shiner (Cyprinella venusta) and red 
shiner (C. lutrensis);
    <bullet> Texas fawnsfoot: Freshwater drum (Aplodinotus grunniens);
    <bullet> Texas pimpleback and Guadalupe orb: Channel catfish 
(Ictalurus punctatus), flathead catfish (Pylodictus olivaris), and 
tadpole madtom (Noturus gyrinus);
    <bullet> Texas fatmucket and Guadalupe fatmucket: Green sunfish 
(Lepomis cyanellus), bluegill (L. macrochirus), largemouth bass 
(Micropterus salmoides), and Guadalupe bass (M. treculii).
Summary of Essential Physical or Biological Features
    In summary, we derive the specific PBFs essential to the 
conservation of Central Texas mussels from studies of these species' 
habitat, ecology, and life history as described above. Additional 
information can be found in the SSA report available on http://www.regulations.gov under Docket No. FWS-R2-ES-2019-0061. We have 
determined that the following PBFs are essential to the conservation of 
the Central Texas mussels:
    (1) Suitable substrates and connected instream habitats, 
characterized by geomorphically stable stream channels and banks (i.e., 
channels that maintain lateral dimensions, longitudinal profiles, and 
sinuosity patterns over time without an aggrading or degrading bed 
elevation) with habitats that support a diversity of freshwater mussel 
and native fish (such as stable riffle-run-pool habitats that provide 
flow refuges consisting of silt-free gravel and coarse sand 
substrates).
    (2) Adequate flows, or a hydrologic flow regime (which includes the 
severity, frequency, duration, and seasonality of discharge over time), 
necessary to maintain benthic habitats where the species are found and 
to maintain connectivity of streams with the floodplain, allowing the 
exchange of nutrients and sediment for maintenance of the mussels' and 
fish hosts' habitat, food availability, spawning habitat for native 
fishes, and the ability for newly transformed juveniles to settle and 
become established in their habitats.
    (3) Water and sediment quality (including, but not limited to, 
dissolved oxygen, conductivity, hardness, turbidity, temperature, pH, 
ammonia, heavy metals, and chemical constituents) necessary to sustain 
natural physiological processes for normal behavior, growth, and 
viability of all life stages.
    (4) The presence and abundance of fish hosts necessary for 
recruitment of the Central Texas mussels.
Special Management Considerations or Protection
    When designating critical habitat, we assess whether the specific 
areas within the geographical area occupied by the species at the time 
of listing contain features which are essential to the conservation of 
the species and which may require special management considerations or 
protection. The features essential to the conservation of the Central 
Texas mussels may require special management considerations or 
protections to reduce the following threats: Increased fine sediment, 
changes in water quality impairment, altered hydrology from both 
inundation and flow loss/scour, predation and collection, and barriers 
to fish movement.
    Management activities that could ameliorate these threats include, 
but are

[[Page 47952]]

not limited to: Use of best management practices (BMPs) designed to 
reduce sedimentation, erosion, and bank side destruction; protection of 
riparian corridors and leaving sufficient canopy cover along banks; 
exclusion of livestock and nuisance wildlife (feral hogs, exotic 
ungulates); moderation of surface and ground water withdrawals to 
maintain natural flow regimes; increased use of stormwater management 
and reduction of stormwater flows into the systems; use of highest 
water quality standards for wastewater and other return flows, and 
reduction of other watershed and floodplain disturbances that release 
sediments, pollutants, or nutrients into the water.
    In summary, we find that the occupied areas we are proposing to 
designate as critical habitat contain the PBFs that are essential to 
the conservation of the species and that may require special management 
considerations or protection. Special management considerations or 
protection may be required of the Federal action agency to eliminate, 
or to reduce to negligible levels, the threats affecting the PBFs of 
each unit.

Criteria Used To Identify Critical Habitat

    As required by section 4(b)(2) of the Act, we use the best 
scientific data available to designate critical habitat. In accordance 
with the Act and our implementing regulations at 50 CFR 424.12(b), we 
review available information pertaining to the habitat requirements of 
the species and identify specific areas within the geographical area 
occupied by the species at the time of listing and any specific areas 
outside the geographical area occupied by the species to be considered 
for designation as critical habitat.
    We are proposing to designate critical habitat in areas within the 
geographical area that was occupied by the species at the time of 
listing. We also are proposing to designate specific areas outside the 
geographical area occupied by the species at the time of listing 
because we have determined that a designation limited to occupied areas 
would be inadequate to ensure the conservation of the species. The 
current distributions of all six of the Central Texas mussels are much 
reduced from their historical distributions. We anticipate that 
recovery will require continued protection of existing populations and 
habitat, as well as ensuring that there are adequate numbers of mussels 
in stable populations that occur over a wide geographic area. This 
strategy will help to ensure that catastrophic events, such as the 
effects of hurricanes (which can lead to flooding that causes excessive 
sedimentation, nutrients, and debris to disrupt stream ecology, etc.) 
and drought, cannot simultaneously affect all known populations. 
Rangewide recovery considerations, such as maintaining existing genetic 
diversity and striving for representation of all major portions of the 
species' current ranges, were considered in formulating this proposed 
critical habitat. The unoccupied areas included in this designation all 
contain at least one PBF, fall within the regulatory definition of 
``habitat'' (50 CFR 424.02), and are reasonably certain to contribute 
to the conservation of the species, as discussed in the below unit 
descriptions.
    Sources of data for this proposed critical habitat include multiple 
databases maintained by universities and State agencies, scientific and 
agency reports, and numerous survey reports on streams throughout the 
species' ranges (see SSA report).

Areas Occupied at the Time of Listing

    The proposed critical habitat designations do not include all 
streams known to have been occupied by the species historically; 
instead, they focus on streams occupied at the time of listing that 
have retained the necessary PBFs that will allow for the maintenance 
and expansion of existing populations. A stream reach may not have all 
of the PBFs to be included as proposed critical habitat; in such 
reaches, our goal is to recover the species by restoring the missing 
PBFs. We defined ``occupied'' units as stream channels with 
observations of one or more live individuals. Specific habitat areas 
were delineated based on reports of live individuals and recently dead 
shells. We include ``recent dead shell material'' to delineate the 
boundaries of a unit because recently dead shell material at a site 
indicates the species is present in that area. Recently dead shells 
have tissue remaining on the shells or have retained a shiny nacre, 
indicating the animal died within days or weeks of finding the shell. 
It is highly unlikely that a dead individual represents the last 
remaining individual of the population, and recently dead shells are an 
accepted indicator of species' presence (e.g., Howells 1996; Randklev 
et al. 2012). We are relying on evidence of occupancy from data 
collected in 2000 to the present. This is because freshwater mussels 
may be difficult to detect and some sites are not visited multiple 
times. Additionally, these species live at least 15--20 years. Because 
adults are less sensitive to habitat changes than juveniles, changes in 
population sizes usually occur over decades rather than years. As a 
result, areas where individuals were collected within the last 20 years 
are expected to remain occupied now. Additionally, any areas that were 
surveyed around 20 years ago and do not have subsequent surveys were 
reviewed for any large-scale habitat changes (i.e., major flood or 
scour event, drought) to confirm that general habitat characteristics 
remained constant over this time. None of the relatively few areas 
without more recent survey information had experienced changes to 
general habitat characteristics. Therefore, data from around 2000 would 
be considered a strong indicator a species remains extant at a site if 
general habitat characteristics have remained constant over that time.
    For occupied areas proposed as critical habitat, we delineated 
critical habitat unit boundaries using the following criterion: 
Evaluate habitat suitability of stream segments within the geographic 
area occupied at the time of listing, and retain those segments that 
contain some or all of the PBFs to support life-history functions 
essential for conservation of the species.
    As a final step, we evaluated those occupied stream segments 
retained through the above analysis and refined the starting and ending 
points by evaluating the presence or absence of appropriate PBFs. We 
selected upstream and downstream cutoff points to reference existing 
easily recognizable geopolitical features including confluences, 
highway crossings, and county lines. Using these features as end points 
allows the public to clearly understand the boundaries of critical 
habitat. Unless otherwise specified, any stream beds located directly 
beneath bridge crossings or other landmark features used to describe 
critical habitat spatially, such as stream confluences, are considered 
to be wholly included within the critical habitat unit. Critical 
habitat stream segments were then mapped using ArcMap version 10 (ESRI, 
Inc.), a Geographic Information Systems program.
    We consider the following streams to be occupied by the Guadalupe 
fatmucket at the time of proposed listing: Guadalupe River, North Fork 
Guadalupe River, and Johnson Creek (see Unit Descriptions, below).
    We consider the following streams to be occupied by the Texas 
fatmucket at the time of proposed listing: Bluff Creek, Elm Creek, San 
Saba River, Cherokee Creek, North Llano River, South Llano River, Llano 
River, James River, Threadgill Creek, Beaver Creek,

[[Page 47953]]

Pedernales River, Live Oak Creek, and Onion Creek (see Unit 
Descriptions, below).
    We consider the following streams to be occupied by the Texas 
fawnsfoot at the time of proposed listing: Clear Fork of the Brazos 
River, Upper Brazos River, Lower Brazos River, Navasota River, Little 
River, Lower San Saba River, Upper Colorado River, Lower Colorado 
River, East Fork of the Trinity River, and Middle Trinity River (see 
Unit Descriptions, below).
    We consider the following streams to be occupied by the Guadalupe 
orb at the time of proposed listing: Upper Guadalupe River, South Fork 
Guadalupe River, Lower Guadalupe River, and San Marcos River (see Unit 
Descriptions, below).
    We consider the following streams to be occupied by the Texas 
pimpleback at the time of proposed listing: Concho River, Upper 
Colorado River, Lower San Saba River, Upper San Saba River, Llano 
River, and Lower Colorado River (see Unit Descriptions, below).
    We consider the following streams to be occupied by false spike at 
the time of proposed listing: Little River, San Gabriel River, Brushy 
Creek, San Saba River, Llano River, San Marcos River, and Guadalupe 
River (see Unit Descriptions, below).

Areas Outside the Geographic Area Occupied at the Time of Listing

    We are not proposing to designate any areas outside the 
geographical area currently occupied by the false spike, Guadalupe orb, 
and Guadalupe fatmucket because we did not find any unoccupied areas 
that contained the necessary PBFs and were essential for the 
conservation of the species. However, each species needs the 
establishment and protection of additional resilient populations across 
their historical ranges to reduce their risk of extinction. While the 
species need these areas, we do not currently have adequate information 
to identify where these populations could be located at this time.
    We have determined that a designation limited to the occupied units 
would be inadequate to ensure the conservation of the Texas fatmucket, 
Texas fawnsfoot, and Texas pimpleback. Of the five remaining fragmented 
and isolated populations of Texas fatmucket, two are small in abundance 
and occupied stream length and have low to no resiliency (i.e., are 
unhealthy), and one population is functionally extirpated. The other 
two current populations have moderate resiliency and remain at risk of 
extirpation. For Texas fawnsfoot, seven populations remain. Four 
populations have moderate resiliency, and three are unhealthy or are 
functionally extirpated. The populations with moderate resiliency are 
all in the mainstem of large rivers, subject to decreased water quality 
as urbanization increases. Increasing the size of populations in the 
upper portions of the watersheds will increase the redundancy and 
representation of the Texas fawnsfoot in areas that are not subject to 
similar water quality declines. Finally, of the five remaining Texas 
pimpleback populations, three are unhealthy and are not reproducing, 
and two have moderate resiliency. This species needs expanded 
populations across its range to increase the populations' resiliency 
and the species' redundancy and representation.
    In the SSA report, we defined 50 miles (80 km) as a stream length 
long enough to sustain a highly resilient population of the Central 
Texas mussels because a single event is unlikely to affect the entire 
population, and the affected section may be repopulated by mussel beds 
up- or downstream. Where available, we identified areas outside the 
geographical area currently occupied by Texas fatmucket, Texas 
pimpleback, and Texas fawnsfoot as critical habitat in order to 
increase the occupied stream length of existing small populations. Not 
all small (less than 50 miles) occupied stream reaches may have 
adjacent unoccupied reaches that are reasonably certain to contribute 
to the conservation of the species, and while these smaller reaches 
will inherently have a higher risk of extirpation, these smaller areas 
contribute to the conservation of the species through maintaining 
redundancy and representation. Special management within smaller 
occupied units can reduce the risk of extirpation.
    We are proposing to designate some areas outside the geographical 
area currently occupied by Texas fatmucket, Texas pimpleback, and Texas 
fawnsfoot we found to be essential for the conservation of each 
species. The proposed unoccupied subunits are essential to the 
conservation of the species because each provides for the growth and 
expansion of the species within portions of their historical ranges. 
The longer the reach occupied by a species, the more likely it is that 
the population can withstand stochastic events such as extreme 
flooding, dewatering, or water contamination. Therefore, the unoccupied 
subunits are each essential for the conservation of the species. These 
proposed areas are located immediately adjacent to currently occupied 
stream reaches, include one or more of the necessary PBFs, and would 
allow for expansion of existing populations necessary to improve 
population resiliency, extend physiographic representation, and reduce 
the risk of extinction for the species. The establishment of additional 
moderately healthy to healthy populations across the range of these 
species would sufficiently reduce their risk of extinction. Improving 
the resiliency of populations in the currently occupied streams, and 
into identified unoccupied areas, will increase species viability to 
the point that the protections of the Act are no longer necessary. The 
unoccupied reaches we are proposing for critical habitat designation 
are Elm Creek and Onion Creek for the Texas fatmucket; the Clear Fork 
Brazos River for the Texas fawnsfoot; and the Llano River and Concho 
River for the Texas pimpleback.

General Information on the Maps of the Proposed Critical Habitat 
Designations

    When determining proposed critical habitat boundaries, we made 
every effort to avoid including developed areas such as lands covered 
by buildings, pavement, and other structures because such lands lack 
physical or biological features necessary for the Central Texas 
mussels. The scale of the maps we prepared under the parameters for 
publication within the Code of Federal Regulations may not reflect the 
exclusion of such developed lands. Any such lands inadvertently left 
inside critical habitat boundaries shown on the maps of this proposed 
rule have been excluded by text in the proposed rule and are not 
proposed for designation as critical habitat. Therefore, if the 
critical habitat is finalized as proposed, a Federal action involving 
these lands would not trigger section 7 consultation under the Act with 
respect to critical habitat and the requirement of no adverse 
modification unless the specific action would affect the physical or 
biological features in the adjacent critical habitat.
    We propose to designate as critical habitat lands that we have 
determined are occupied at the time of listing (i.e., currently 
occupied) and that contain one or more of the physical or biological 
features that are essential to support life-history processes of the 
species. We have determined that occupied areas are inadequate to 
ensure the conservation of the species. Therefore, we have also 
identified, and propose for designation as critical habitat, unoccupied 
areas that are essential for the conservation of the species.
    The proposed critical habitat designations are defined by the map 
or

[[Page 47954]]

maps, as modified by any accompanying regulatory text, presented at the 
end of this document under Proposed Regulation Promulgation. We include 
more detailed information on the boundaries of the proposed critical 
habitat designations in the discussion of individual units below. We 
will make the coordinates or plot points or both on which each map is 
based available to the public on http://www.regulations.gov under 
Docket No. FWS-R2-ES-2019-0061.

Proposed Critical Habitat Designation

    In total, we are proposing to designate approximately 1,944 river 
mi (3,129 river km), accounting for overlapping units, in 27 units 
(total of 50 subunits; Table 8) as critical habitat for one or more 
Central Texas mussel species: The false spike, Texas fatmucket, 
Guadalupe fatmucket, Texas pimpleback, Guadalupe orb, and Texas 
fawnsfoot. All but five of the subunits are currently occupied by one 
or more of the species, and each of the 50 subunits contains the 
physical and biological features essential to the conservation of each 
species. These proposed critical habitat areas, described below, 
constitute our current best assessment of areas that meet the 
definition of critical habitat for the six Central Texas mussel 
species. Each species historically occurred in a different subset of 
watersheds in Central Texas; therefore, there are large differences in 
the amount of critical habitat proposed for each species. For example, 
the Guadalupe fatmucket only occurred in the upper reaches of the 
Guadalupe River basin. As such, we have not proposed to designate areas 
outside of the very small historical range. In contrast, Texas 
fawnsfoot was historically widespread in three basins; therefore, to 
maintain the adaptive capacity of this species, we are proposing to 
designate a larger area for Texas fawnsfoot. Texas surface water is 
owned by the State, as are the beds of navigable streams; thus the 
actual critical habitat units (occupied waters and streambeds up to the 
ordinary high-water mark) are owned by the State of Texas (Texas Water 
Code Section 11.021, 11.0235). Adjacent riparian areas are in most 
cases, privately owned, and are what is reported in the discussion that 
follows. In many cases, activities on adjacent private land would not 
trigger section 7 consultation under the Act if those activities do not 
affect instream habitat.

                    Table 8--Overall Proposed Critical Habitat for the Central Texas Mussels
                          [Note: Stream lengths will not sum due to overlapping units.]
----------------------------------------------------------------------------------------------------------------
                                                                                            Proposed critical
               Species                       Basin/unit name              Occupied        habitat river mi (km)
----------------------------------------------------------------------------------------------------------------
Guadalupe fatmucket.................  Guadalupe River:............  Yes................
                                         GUFM-1a: North Fork        ...................               7.5 (12.1)
                                          Guadalupe River.
                                         GUFM-1b: Johnson Creek...  ...................              10.4 (16.7)
                                         GUFM-1c: Guadalupe River.  ...................              36.2 (58.3)
                                                                                        ------------------------
                                                                                              Total: 54.1 (87.1)
----------------------------------------------------------------------------------------------------------------
Texas fatmucket.....................  Colorado River:.............  Yes................
                                         TXFM-1a: Bluff Creek.....  ...................              11.8 (19.0)
                                         TXFM-1b: Lower Elm Creek.  ...................              12.5 (20.2)
                                         TXFM-2: San Saba River...  ...................             93.4 (150.3)
                                         TXFM-3: Cherokee Creek...  ...................              18.1 (29.2)
                                         TXFM-4a: North Llano       ...................              31.2 (50.1)
                                          River.
                                         TXFM-4b: South Llano       ...................              22.9 (36.8)
                                          River.
                                         TXFM-4c: Llano River.....  ...................             90.4 (145.6)
                                         TXFM-4d: James River.....  ...................              18.6 (30.1)
                                         TXFM-4e: Threadgill Creek  ...................               8.3 (13.4)
                                         TXFM-4f: Beaver Creek....  ...................              12.9 (20.8)
                                         TXFM-5a: Pedernales River  ...................             80.1 (128.9)
                                         TXFM-5b: Live Oak Creek..  ...................                2.6 (4.2)
                                         TXFM-6a: Lower Onion       ...................                5.2 (8.3)
                                          Creek.
                                                                                        ------------------------
                                                                                            Total: 408.2 (656.8)
                                      Colorado River:.............  No.................
                                         TXFM-1c: Upper Elm Creek.  ...................               9.1 (14.7)
                                         TXFM-6b: Upper Onion       ...................              18.9 (30.4)
                                          Creek.
                                                                                        ------------------------
                                                                                                Total: 28 (45.1)
----------------------------------------------------------------------------------------------------------------
Texas fawnsfoot.....................  Brazos River:...............  Yes................
                                         TXFF-1a: Upper Clear Fork  ...................              27.9 (44.9)
                                          Brazos River.
                                         TXFF-2: Upper Brazos       ...................             79.9 (128.6)
                                          River.
                                         TXFF-3a: Lower Brazos      ...................            348.0 (560.0)
                                          River.
                                         TXFF-3b: Navasota River..  ...................              39.3 (63.2)
                                      Colorado River:
                                         TXFF-4: Little River.....  ...................              35.6 (57.3)
                                         TXFF-5a: San Saba River..  ...................              50.4 (81.1)
                                         TXFF-5b: Upper Colorado    ...................              10.5 (16.9)
                                          River.
                                         TXFF-6: Lower Colorado     ...................            124.4 (200.2)
                                          River.
                                      Trinity River:
                                         TXFF-7: East Fork Trinity  ...................              15.6 (25.1)
                                          River.
                                         TXFF-8: Trinity River....  ...................            157.0 (252.7)
                                                                                        ------------------------
                                                                                          Total: 888.6 (1,430.1)

[[Page 47955]]

 
                                      Brazos River:...............  No.................
                                         TXFF-1b: Lower Clear Fork  ...................              28.6 (46.0)
                                          Brazos River.
----------------------------------------------------------------------------------------------------------------
Guadalupe orb.......................  Guadalupe River:............  Yes................
                                         GORB-1a: South Fork        ...................                5.1 (8.3)
                                          Guadalupe River.
                                         GORB-1b: Upper Guadalupe   ...................             99.4 (159.9)
                                          River.
                                         GORB-2a: San Marcos River  ...................             65.3 (105.1)
                                         GORB-2b: Lower Guadalupe   ...................            124.7 (200.7)
                                          River.
                                                                                        ------------------------
                                                                                                   294.5 (474.0)
----------------------------------------------------------------------------------------------------------------
Texas pimpleback....................  Colorado River:.............  Yes................
                                         TXPB-1a: Bluff Creek.....  ...................              11.8 (19.0)
                                         TXPB-1b: Lower Elm Creek.  ...................              12.5 (20.2)
                                         TXPB-2a: Lower Concho      ...................              35.6 (57.2)
                                          River.
                                         TXPB-3a: Upper Colorado    ...................            153.8 (247.6)
                                          River.
                                         TXPB-3b: Lower San Saba    ...................              50.4 (81.1)
                                          River.
                                      TXPB-4: Upper San Saba River  ...................              52.8 (85.0)
                                         TXPB-5a: Upper Llano       ...................              38.3 (61.6)
                                          River.
                                         TXPB-6: Lower Colorado     ...................            111.3 (179.1)
                                          River.
                                                                                        ------------------------
                                                                                            Total: 466.5 (750.8)
                                      Colorado River:.............  No.................
                                         TXPB-2b: Upper Concho      ...................              16.0 (25.7)
                                          River.
                                         TXPB-5b: Lower Llano       ...................              12.2 (19.7)
                                          River.
                                                                                        ------------------------
                                                                                              Total: 28.2 (45.4)
----------------------------------------------------------------------------------------------------------------
False spike.........................  Brazos River:...............  Yes................
                                         FASP-1a: Little River....  ...................              35.6 (57.3)
                                         FASP-1b: San Gabriel       ...................              31.4 (50.5)
                                          River.
                                         FASP-1c: Brushy Creek....  ...................              14.0 (22.5)
                                      Colorado River:
                                         FASP-2: San Saba River...  ...................              50.4 (81.1)
                                         FASP-3: Llano River......  ...................              50.5 (81.3)
                                      Guadalupe River:
                                         FASP-4a: San Marcos River  ...................              21.6 (34.8)
                                         FASP-4b: Guadalupe River.  ...................            124.7 (200.7)
                                                                                        ------------------------
                                                                                            Total: 328.2 (528.2)
----------------------------------------------------------------------------------------------------------------

Guadalupe Fatmucket

    We are proposing to designate approximately 54.1 river mi (87.1 
river km) in a single unit (three subunits) as critical habitat for 
Guadalupe fatmucket. The critical habitat areas we describe below 
constitute our current best assessment of areas that meet the 
definition of critical habitat for Guadalupe fatmucket. The unit we 
propose as critical habitat is GUFM-1: Guadalupe River Unit. Table 9 
shows the occupancy of the unit, the riparian ownership, and 
approximate length of the proposed designated areas for the Texas 
fatmucket. We present a brief description of the proposed unit, and 
reasons why it meets the definition of critical habitat for Guadalupe 
fatmucket, below.

                      Table 9--Proposed Critical Habitat Units for the Guadalupe Fatmucket
                                  [Note: Lengths may not sum due to rounding.]
----------------------------------------------------------------------------------------------------------------
                                                                                                    River miles
               Unit                       Subunit         Riparian ownership       Occupancy       (kilometers)
----------------------------------------------------------------------------------------------------------------
GUFM-1: Guadalupe River..........  GUFM-1a: North Fork   Private............  Occupied..........      7.5 (12.1)
                                    Guadalupe River.
                                   GUFM-1b: Johnson      Private............  Occupied..........     10.4 (16.7)
                                    Creek.
                                   GUFM-1c: Guadalupe    Private............  Occupied..........     36.2 (58.3)
                                    River.
                                                                                                 ---------------
    Total........................  ....................  ...................  ..................     54.1 (87.1)
----------------------------------------------------------------------------------------------------------------


[[Page 47956]]

Guadalupe River Basin

Unit GUFM-1: Guadalupe River
    Subunit GUFM-1a: North Fork Guadalupe River. The North Fork 
Guadalupe River subunit consists of 7.5 river mi (12.1 river km) in 
Kerr County, Texas. The adjacent riparian areas of the subunit are 
privately owned. The entire subunit is currently occupied by the 
species. The North Fork Guadalupe River subunit extends from the FM 
1340 bridge crossing (just upstream of the Bear Creek Boy Scout camp) 
downstream to the confluence with the Guadalupe River. This subunit 
contains all of the PBFs essential to the conservation of the Guadalupe 
fatmucket. The North Fork Guadalupe River subunit is in a mostly rural 
setting; is influenced by drought, low flows, and flooding (leading to 
scour); and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. Special management may be necessary to ensure adequate 
instream flow and water quality.
    Subunit GUFM-1b: Johnson Creek. The Johnson Creek subunit consists 
of 10.4 river mi (16.7 river km) within Kerr County, Texas. The Johnson 
Creek subunit begins at the Byas Springs Road crossing downstream to 
the confluence with the Guadalupe River. The adjacent riparian area is 
privately owned. The subunit is occupied by the Guadalupe fatmucket. 
This site contains the majority of the PBFs essential to the 
conservation of the species. Certain PBFs, such as sufficient water 
flow, dissolved oxygen levels, and water temperature, may be missing or 
degraded during times of drought. The Johnson Creek subunit is in a 
mostly rural but urbanizing setting, is influenced by drought, low 
flows, and flooding (leading to scour), and is being affected by 
ongoing agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity.
    Subunit GUFM-1c: Guadalupe River. This unit consists of 
approximately 36.2 river mi (58.3 river km) in Kerr and Kendall 
Counties, Texas. The Guadalupe River Subunit extends from the 
confluence of the North and South Fork Guadalupe Rivers downstream to 
the Interstate Highway 10 bridge crossing near Comfort, Texas. The 
adjacent riparian areas of this subunit are privately owned. The 
subunit is occupied by the Guadalupe fatmucket. This portion of the 
Guadalupe River basin is largely agricultural with several 
municipalities and multiple low-head dams originally built for a 
variety of purposes and now largely used for recreation (kayaking, 
fishing, camping, swimming, etc.). This subunit provides all of the 
PBFs essential to the conservation of the species. The Guadalupe River 
subunit is experiencing some urbanization and is influenced by drought, 
low flows, and flooding (leading to scour), and is being affected by 
ongoing agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and wastewater inputs. Therefore, special 
management is necessary to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. This subunit 
is also occupied by Guadalupe orb.

Texas Fatmucket

    We are proposing to designate approximately 436.0 river mi (701.7 
km) in 6 units (15 subunits) as critical habitat for Texas fatmucket. 
The critical habitat areas we describe below constitute our current 
best assessment of areas that meet the definition of critical habitat 
for Texas fatmucket. The six areas we propose as critical habitat are: 
TXFM-1: Elm Creek Unit; TXFM-2: San Saba River Unit; TXFM-3: Cherokee 
Creek Unit; TXFM-4: Llano River Unit; TXFM-5: Pedernales River Unit; 
and TXFM-6: Onion Creek Unit. Table 10 shows the occupancy of the 
units, the riparian ownership, and approximate length of the proposed 
designated areas for the Texas fatmucket. We present brief descriptions 
of all proposed units, and reasons why they meet the definition of 
critical habitat for Texas fatmucket, below.

                          Table 10--Proposed Critical Habitat Units for Texas Fatmucket
                                  [Note: Lengths may not sum due to rounding.]
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
              Unit                      Subunit         Riparian ownership       Occupancy         (kilometers)
----------------------------------------------------------------------------------------------------------------
TXFM-1: Elm Creek...............  TXFM-1a: Bluff       Private............  Occupied...........      11.8 (19.0)
                                   Creek.
                                  TXFM-1b: Lower Elm   Private............  Occupied...........      12.5 (20.2)
                                   Creek.
                                  TXFM-1c: Upper Elm   Private............  Unoccupied.........       9.1 (14.7)
                                   Creek.
TXFM-2: San Saba River..........  ...................  Private............  Occupied...........     93.4 (150.3)
TXFM-3: Cherokee Creek..........  ...................  Private............  Occupied...........      18.1 (29.2)
TXFM-4: Llano River.............  TXFM-4a: North       Private............  Occupied...........      31.2 (50.1)
                                   Llano River.
                                  TXFM-4b: South       Private............  Occupied...........      22.9 (36.8)
                                   Llano River.
                                  TXFM-4c: Llano       Private............  Occupied...........     90.4 (145.6)
                                   River.
                                  TXFM-4d: James       Private............  Occupied...........      18.6 (30.1)
                                   River.
                                  TXFM-4e: Threadgill  Private............  Occupied...........       8.3 (13.4)
                                   Creek.
                                  TXFM-4f: Beaver      Private............  Occupied...........      12.9 (20.8)
                                   Creek.
TXFM-5: Pedernales River........  TXFM-5a: Pedernales  Private, Federal...  Occupied...........     80.1 (128.9)
                                   River.
                                  TXFM-5b: Live Oak    Private............  Occupied...........        2.6 (4.2)
                                   Creek.
TXFM-6: Onion Creek.............  TXFM-6a: Lower       Private............  Occupied...........        5.2 (8.3)
                                   Onion Creek.
                                  TXFM-6b: Upper       Private............  Unoccupied.........      18.9 (30.4)
                                   Onion Creek.
                                                                                                ----------------
    Total.......................  ...................  ...................  ...................    436.0 (701.7)
----------------------------------------------------------------------------------------------------------------


[[Page 47957]]

Colorado River Basin

Unit TXFM-1: Elm Creek
    Subunit TXFM-1a: Bluff Creek. This occupied critical habitat 
subunit consists of 11.8 river mi (19.0 km) of Bluff Creek, a tributary 
to Elm Creek, in Runnels County, Texas. The subunit extends from the 
County Road 153 bridge crossing, near the town of Winters, Texas, 
downstream to the confluence of Bluff and Elm creeks. The riparian area 
of this subunit is privately owned. This subunit is currently occupied 
by Texas fatmucket. The Bluff Creek subunit is in a rural setting, is 
influenced by drought, low flows, and elevated chlorides, and is being 
affected by ongoing agricultural activities and development resulting 
in excessive sedimentation, water quality degradation, and ground water 
withdrawals and surface water diversions. Therefore, special management 
is necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. This subunit is also 
occupied by Texas pimpleback.
    Subunit TXFM-1b: Lower Elm Creek. This subunit consists of 12.5 
river mi (20.2 km) of Elm Creek beginning at the confluence of Bluff 
Creek and continuing downstream to Elm Creek's confluence with the 
Colorado River in Runnels County, Texas. The riparian lands adjacent to 
this subunit are privately owned. The Elm Creek watershed is relatively 
small and remains largely rural and dominated by agricultural 
practices. This stream regularly has extremely low or no flow during 
times of drought. Moreover, this stream has elevated chloride 
concentrations and sedimentation resulting in reduced habitat quality 
and availability, and decreased water quality. Lower Elm Creek is 
occupied by Texas fatmucket and contains some of the PBFs essential to 
the conservation of the species such as presence of host fish; others 
are in degraded condition and would benefit from management actions 
such as improving water quality and substrate. The Lower Elm Creek 
subunit is influenced by drought, low flows, and elevated chlorides, 
and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. This unit is also occupied by Texas pimpleback.
    Subunit TXFM-1c: Upper Elm Creek. Because we have determined 
occupied areas are not adequate for the conservation of the species, we 
evaluated whether any unoccupied areas are essential for the 
conservation of Texas fatmucket and identified this area as essential 
for the conservation of the species. This subunit consists of 9.1 river 
mi (14.7 km) from the County Road 153 crossing, near the town of 
Winters, Texas, downstream to the confluence of Bluff and Elm creeks. 
The riparian area surrounding this subunit is privately owned. The 
entire Elm Creek watershed is dominated by agriculture and remains 
rural. Upper Elm Creek is not currently occupied by Texas fatmucket, 
but it is essential for the conservation of the species because it 
provides for the growth and expansion of the Texas fatmucket within a 
portion of its historical range on Elm Creek; the occupied segment of 
Elm Creek is too small to ensure conservation of the Texas fatmucket 
over the long term. This unit is important to the conservation of Texas 
fatmucket because it is the furthest upstream population; its loss 
would shrink the overall range of Texas fatmucket to the lower, larger 
tributaries of the Colorado River. Additionally, this population of 
Texas fatmucket is substantially far from the other population of the 
species, such that if a catastrophic event such as drought or extreme 
flooding were to occur it is likely that this population would be 
affected differently, increasing the chance of the species surviving 
such an event.
    The Upper Elm Creek subunit is in a rural setting, is influenced by 
drought, low flows, and elevated chlorides, and is being affected by 
ongoing agricultural activities. Although it is considered unoccupied, 
portions of this subunit contain some or all of the physical or 
biological features essential for the conservation of the species. As 
previously mentioned, flow rates in this subunit are typically not 
within the range required by the Texas fatmucket (PBF 1). This subunit 
is often characterized by small, isolated pools separated by short 
riffles over bedrock during low flow and when dam releases are minimal. 
During the last decade, lower Elm Creek has experienced both the lowest 
and highest flow rates on record (see SSA report for more information). 
This subunit will require management actions that address flow rate and 
associated stream habitat quality.
    Suitable stream habitat and hydrological connectivity (PBF 2) are 
unsupported throughout the entirety of this subunit. Specifically, low 
flows during times of drought punctuated by high flows are either 
scouring the stream habitat, or depositing stream sediments downstream. 
Because mussels are sedentary organisms, transportation of individuals 
during flooding events is often lethal.
    The Texas fatmucket uses predatory fish (e.g., bass and sunfishes) 
for its host infestation period of its lifecycle. These host fishes 
(PBF 3) are presumed to be common throughout the state of Texas and 
within the Upper Elm Creek subunit. While ongoing research may be 
necessary to confirm current abundance of host fishes are at suitable 
levels, we currently believe they are adequate.
    This subunit is not included in Texas Commission on Environmental 
Quality classified stream segments; therefore, we have no specific 
water quality information. During times of normal flow this subunit 
likely supports healthy water quality parameters (PBF 4) for Texas 
fatmucket, but water quality is likely compromised during low flows, 
when water temperatures rise and dissolved oxygen drops. The Upper Elm 
Creek subunit will require additional management practices to ensure 
sufficient water quality standards are being met and maintained for 
Texas fatmucket.
    Because this reach of Elm Creek periodically contains the flowing 
water conditions and host fish species used by Texas fatmucket, it 
qualifies as habitat according to our regulatory definition (50 CFR 
424.02).
    If the Texas fatmucket can be reestablished in this reach, it will 
expand the occupied reach length in Elm Creek to a length that will be 
more resilient to the stressors that the species is facing. The longer 
the reach occupied by a species, the more likely it is that the 
population can withstand stochastic events such as extreme flooding, 
dewatering, or water contamination. In the SSA report, we identified 50 
miles (80.5 km) as a reach long enough for a population to be able to 
withstand stochastic events, and the addition of this 10.9-mile reach, 
as well as the adjacent tributary of Bluff Creek, would expand the 
existing Texas fatmucket population downstream in Lower Elm Creek and 
in Bluff Creek closer to 50 miles. The addition of multiple tributaries 
increases the value of the overall critical habitat unit, providing 
protection for the population should a stochastic event occur in one 
tributary. If Texas fatmucket were to become reestablished throughout 
this unit, it would likely be a moderately to highly resilient 
population due to longer stream length and would increase the species' 
future redundancy. This unit is

[[Page 47958]]

essential for the conservation of the species because it will provide 
habitat for range expansion in portions of known historical habitat 
that is necessary to increase viability of the species by increasing 
its resiliency, redundancy, and representation.
    We are reasonably certain that this unit will contribute to the 
conservation of the species, because the need for conservation efforts 
is recognized and is being discussed by our conservation partners, and 
methods for restoring and reintroducing the species into unoccupied 
habitat are being developed. The Texas fatmucket is listed as 
threatened by the State of Texas, and the Texas Comptroller of Public 
Accounts has funded research, surveys, propagation, and reintroduction 
studies for this species. State and Federal partners have shown 
interest in propagation and reintroduction efforts for the Texas 
fatmucket. As previously mentioned, efforts are underway regarding a 
captive propagation program for Texas fatmucket at the San Marcos 
Aquatic Resource Center and Inks Dam National Fish Hatchery. The State 
of Texas, San Marcos Aquatic Resource Center, Inks Dam National Fish 
Hatchery, and the Service's Austin and Texas Coastal Field Offices 
collaborate regularly on conservation actions. Therefore, this 
unoccupied critical habitat subunit is essential for the conservation 
of the Texas fatmucket and is reasonably certain to contribute to such 
conservation.
Unit TXFM-2: San Saba River
    This unit consists of 93.4 river mi (150.3 km) of the San Saba 
River in Menard, Mason, McCulloch, and San Saba Counties, Texas. This 
unit of the San Saba River extends from the Schleicher and Menard 
County line, near Fort McKavett, Texas, downstream to the San Saba 
River confluence with the Colorado River. The adjacent riparian areas 
are privately owned. This basin is largely rural and is dominated by 
mostly agricultural activities including cattle grazing and hay and 
pecan farming. This unit is affected by very low flows and drought 
during the summer, which is exacerbated by pumping. This unit contains 
all of the PBFs essential to the conservation of the Texas fatmucket 
and is currently occupied by the species. The San Saba River unit is 
influenced by drought, low flows, underlying geology resulting in a 
losing reach and is being affected by ongoing agricultural activities 
and development resulting in excessive sedimentation, water quality 
degradation, groundwater withdrawals and surface water diversions, and 
collection. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, improve 
habitat connectivity, and manage collection. Special management will be 
necessary to ensure adequate flow and prevent water quality 
degradation. This subunit is also occupied by Texas fawnsfoot, Texas 
pimpleback, and false spike.
Unit TXFM-3: Cherokee Creek
    This unit consists of 18.1 river mi (29.2 km) of Cherokee Creek in 
San Saba County, Texas. The adjacent riparian lands are privately 
owned. The Cherokee Creek unit extends from the County Road 409 bridge 
crossing downstream to the confluence with the Colorado River. This 
unit is occupied by the Texas fatmucket and contains all of the PBFs 
essential to the conservation of the species. Even though this unit is 
smaller than 50 miles, which we had determined was the reach length 
long enough to withstand stochastic events, this population increases 
the species' redundancy, making it more likely to withstand 
catastrophic events that may eliminate one or more of the other 
populations. The Cherokee Creek unit is in a rural setting, is 
influenced by drought and low flows, and is being affected by ongoing 
agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. Special management 
may be necessary to limit the effect of low flow and drought 
conditions. With this special management, the threats to the population 
may be reduced, increasing the resiliency of the population, and 
providing additional redundancy and representation for the species.
Unit TXFM-4: Llano River
    Subunit TXFM-4a: North Llano River. This subunit consists of 31.2 
river mi (50.1 km) in Sutton and Kimble Counties, Texas. The North 
Llano River subunit extends from the most upstream County Road 307 
bridge crossing in Sutton County downstream for 31.2 river mi (50.1 
river km) into Kimble County at the confluence with the South Llano 
River near the city of Junction, Texas. The North Llano River is 
occupied by the Texas fatmucket and contains all of the PBFs essential 
to the conservation of the species. Riparian areas adjacent to this 
subunit are privately owned and largely dominated by rural agricultural 
operations. This subunit is not heavily influenced by spring inputs 
like some other tributaries to the Llano River, such as the South Llano 
River. During summertime low flows and extended periods of drought, 
this subunit often becomes a series of isolated pools separated by 
shallow flowing riffles over bedrock. These reduced flows can leave 
mussels stranded and dessicated in dry beds or isolated in shallow 
pools. Decreased flows can also result in decreased water quality, 
specifically in the form of reduced dissolved oxygen and increased 
temperature. Special management may be required to address ongoing 
concerns of low flows and subsequent water quality degradation.
    Subunit TXFM-4b: South Llano River. The South Llano River subunit 
extends from the Edwards and Kimble County line downstream 22.9 river 
mi (36.8 river km) to the confluence with the North Llano River in 
Kimble County, Texas. Riparian areas adjacent to this subunit are 
privately owned. Major activities in this basin are farming, ranching, 
and other agricultural uses, as the watershed remains largely rural. 
The South Llano River subunit is occupied by the Texas fatmucket and 
contains all of the PBFs essential to the conservation of the species. 
The South Llano River subunit is influenced by flooding (leading to 
scour), drought, and low flows and is being affected by ongoing 
agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. Special management 
will be required to address episodic low flows during summer drought 
and associated with reduced spring flow.
    Subunit TXFM-4c: Llano River. This subunit consists of 90.4 river 
mi (145.6 km) in Kimble, Mason, and Llano Counties, Texas. The Llano 
River subunit begins at the confluence of the North and South Fork 
Llano River and continues downstream to the State Highway 16 bridge 
crossing in Llano County. The riparian land adjacent to the subunit is 
privately owned, and the watershed remains largely rural. The Llano 
River subunit is occupied by the Texas fatmucket and contains all of 
the PBFs essential to the conservation of the species. The Llano River 
subunit is in a rural setting; is influenced by flooding (leading to 
scour), drought, and low flows; and is being affected by ongoing

[[Page 47959]]

agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. Special management 
may be necessary to prevent low-flow conditions due to drought and 
agricultural water use. This subunit is also occupied by Texas 
pimpleback and false spike.
    Subunit TXFM-4d: James River. The James River subunit consists of 
18.6 river mi (30.1 km) of the James River and begins at the Kimble and 
Mason county line and continues downstream to the Llano River 
confluence. Adjacent riparian areas are privately owned. The James 
River subunit is occupied by the Texas fatmucket and contains all of 
the PBFs essential to the conservation of the species. The James River 
subunit is in a rural setting; is influenced by flooding (leading to 
scour), drought, and low flows; and is being affected by ongoing 
agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity.
    Subunit TXFM-4e: Threadgill Creek. The Threadgill Creek subunit 
consists of 8.3 river mi (13.4 river km) extending from the Ranch Road 
783 bridge crossing downstream to the confluence with Beaver Creek. 
Riparian lands adjacent to this subunit are privately owned. Threadgill 
Creek is occupied by the Texas fatmucket and contains all of the PBFs 
essential to the conservation of the species. The Threadgill Creek 
subunit is in a rural setting; is influenced by flooding (leading to 
scour), drought, and low flows; and is being affected by ongoing 
agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and ground water withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity.
    Subunit TXFM-4f: Beaver Creek. The Beaver Creek Subunit consists of 
12.9 river mi (20.8 river km) and begins at the confluence with 
Threadgill Creek and continues downstream to the confluence with the 
Llano River. Adjacent riparian habitats are privately owned. This 
subunit contains all of the PBFs essential to the conservation of Texas 
fatmucket. The Beaver Creek subunit is in a rural setting; is 
influenced by flooding (leading to scour), drought, and low flows; and 
is being affected by ongoing agricultural activities and development 
resulting in excessive sedimentation, water quality degradation, and 
ground water withdrawals and surface water diversions. Therefore, 
special management is necessary to reduce sedimentation, improve water 
quality, maintain adequate flows, and improve habitat connectivity.
    This subunit is connected to known populations of Texas fatmucket 
in Subunits TXFM-4c and TXFM-4e, but there are no recent surveys of 
Beaver Creek itself. There are no instream structures in subunits TXFM-
4c and TXFM-4e that would impede water flow; the flow regime is the 
same as in those subunits; and the host fish may move between the 
subunits freely. Based on this information, it is reasonable to 
conclude that the populations in subunits TXFM-4c and TXFM-4e are 
unlikely to stop at the most up- or downstream survey location; 
therefore, we conclude that this subunit is occupied.
    However, due to the lack of recent surveys, we are analyzing this 
subunit against the second prong of the definition of critical habitat 
for unoccupied habitat out of an abundance of caution. If subunit TXFM-
4f is not, in fact, occupied, it is essential to the conservation of 
the species because it provides for needed growth and expansion of the 
species in this portion of its historical range and connectivity 
between documented occupied reaches. Connecting occupied reaches 
increases the resiliency of the occupied reaches by allowing for gene 
flow and repopulation after stochastic events. The longer the occupied 
reach, the more likely it is that the Texas fatmucket population can 
rebound after stochastic events such as extreme flooding, dewatering, 
or water contamination. Therefore, subunit TXFM-4e is essential for the 
conservation of the species.
Unit TXFM-5: Pedernales River
    Subunit TXFM-5a: Pedernales River. The Pedernales River subunit 
consists of 80.1 river mi (128.9 river km) in Gillespie, Blanco, Hays, 
and Travis Counties, Texas. The Pedernales River subunit extends from 
the origination of the Pedernales River at the confluence of Bear and 
Wolf creeks in Gillespie County downstream to the FM 3238 (Hamilton 
Pool Road) bridge crossing in Travis County. The riparian area of this 
subunit is primarily privately owned, although 1.5 river mi (2.4 river 
km) within Lyndon B. Johnson National Historical Park owned and managed 
by the National Park Service (NPS) in Gillespie County, Texas. The 
subunit is currently occupied by the Texas fatmucket and supports all 
of the PBFs essential to the conservation of the species. The watershed 
of the Pedernales River is characterized by agricultural uses including 
irrigated orchards and vineyards. Excess nutrients, sediment, and 
pollutants enter the Pedernales River from wastewater, agricultural 
runoff, and urban stormwater runoff, all of which reduces instream 
water quality. The Pedernales River geology, like many central Texas 
rivers, is predominately limestone outcroppings; therefore, this system 
is subject to flashy, episodic flooding during rain events that 
mobilize large amounts of sediment and wood materials. Special 
management may be required in this subunit to address low water levels 
as a result of water withdrawals and drought. Additionally, 
implementation of the highest levels of treatment of wastewater 
practicable would improve water quality in this subunit, and 
maintenance of riparian habitat and upland buffers would maintain or 
improve substrate quality.
    Subunit TXFM-5b: Live Oak Creek. The Live Oak Creek subunit 
consists of 2.6 river mi (4.2 river km) in Gillespie County, Texas. 
Riparian ownership of lands adjacent to this subunit is private. The 
Live Oak Creek subunit originates at the FM 2093 bridge crossing 
downstream to its confluence with the Pedernales River. This subunit is 
currently occupied by Texas fatmucket and contains all of the PBFs 
essential to the conservation of the species. The Live Oak Creek 
subunit is in a mostly rural setting with some urbanization; is 
influenced by drought, low flows, and flooding (leading to scour); and 
is being affected by ongoing development and agricultural activities 
resulting in excessive sedimentation, water quality degradation, and 
groundwater withdrawals and surface water diversions. Therefore, 
special management is necessary to reduce sedimentation, improve water 
quality, maintain adequate flows, and improve habitat connectivity. 
Special management considerations may be required to address periods of 
low flow, increased sedimentation, and water quality degradation.
Unit TXFM-6: Onion Creek
    Subunit TXFM-6a: Lower Onion Creek. The Lower Onion Creek subunit 
consists of 5.2 river mi (8.3 river km) in

[[Page 47960]]

Travis County, Texas. This subunit extends from the State Highway 130 
bridge crossing downstream to the confluence with the Colorado River. 
This subunit is in close proximity to the rapidly urbanizing city of 
Austin, Texas, and contains substantial municipal developments. The 
effects of such rapid and widespread urbanization have contributed to 
significantly altered flows in Onion Creek that have led to bank 
destabilization, increased sedimentation and streambed mobilization, 
and loss of stable substrate. Further, urban runoff pollutants are 
responsible for degraded water quality conditions. Even though this 
unit is smaller than 50 miles, which we had determined was the reach 
length long enough to withstand stochastic events, the population 
increases the species' redundancy, making it more likely to withstand 
catastrophic events that may eliminate one or more of the other 
populations. Further, it is the easternmost population of Texas 
fatmucket and its loss would lessen the species' distribution 
considerably. The Lower Onion Creek subunit is occupied by Texas 
fatmucket. The subunit occurs within private land and contains some of 
the PBFs essential to the conservation of Texas fatmucket, including 
host fishes. Several PBFs, such as water quality, sufficient flow 
rates, and sedimentation, are either missing in this subunit or 
minimally acceptable for the species. Special management is necessary 
to reduce sedimentation, improve water quality, maintain adequate 
flows, and improve habitat connectivity.
    Subunit TXFM-6b: Upper Onion Creek. Because we have determined 
occupied areas are not adequate for the conservation of the species, we 
have evaluated whether any unoccupied areas are essential for the 
conservation of Texas fatmucket and identified this area as essential 
for the conservation of the species. The Upper Onion Creek subunit 
consists of 18.9 river mi (30.4 river km) of stream habitat with 
private riparian ownership. The subunit begins at the Interstate 
Highway 35 bridge crossing and extends downstream to the State Highway 
130 bridge, where it is adjacent to subunit TXFM-6a. The Upper Onion 
Creek subunit is in a rural but urbanizing setting and is influenced by 
drought, low flows, and flooding (leading to scour). Riparian lands 
adjacent to this subunit are privately owned.
    This unit is essential to the conservation of Texas fatmucket 
because it would expand the easternmost population; its loss would 
diminish the distribution of Texas fatmucket. Additionally, this 
population of Texas fatmucket is substantially far from the other 
population of the species, such that if a catastrophic event such as 
drought or extreme flooding were to occur it is likely that this 
population would be affected differently, increasing the chance of the 
species surviving such an event. The subunit is being affected by 
ongoing agricultural and development activities resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and wastewater inputs.
    Although it is considered unoccupied, portions of this subunit 
contain some or all of the physical or biological features essential 
for the conservation of the species. Water quantity (PBF 1) is likely 
present only during portions of the year. This subunit is subjected to 
extreme high and extreme low flows during periods of flash flooding and 
prolonged drought. This subunit requires management actions that 
address these hydrological alterations leading to extreme high and low 
flow events.
    Suitable substrate and connected instream habitats (PBF 2) are not 
present through the majority of this reach. The Upper Onion Creek 
subunit's watershed is highly urbanized and even minor precipitation 
events frequently result in elevated flows, which scour, mobilize, and 
redeposit stream bed materials. Management actions addressing overland 
flows and the frequency of elevated flows in this subunit are required.
    Access to host fishes (PBF 3) is the only physical or biological 
factor currently supported by this subunit because Texas fatmucket 
utilize common basses and sunfishes (see the SSA report for more 
details). Future management actions could focus on determining if the 
abundance and distribution of host fish are sufficient to support a 
robust Texas fatmucket population.
    Urban runoff and resulting inflows from tributary streams 
contributes to elevated levels of salts and decreased dissolved oxygen 
levels in Onion Creek. While these parameters may be present during 
periods of normal flows, we believe they are degraded overall. 
Management actions that contribute to increased quality of key water 
parameters (PBF 4) would benefit this stream subunit and allow for the 
reestablishment of Texas fatmucket. This subunit occurs within the 
Barton Springs segment of the Edwards Aquifer recharge zone, and the 
continued management of this aquifer may indirectly benefit Texas 
fatmucket through water quality improvements.
    Because this reach of Onion Creek periodically contains the flowing 
water conditions and host fish species used by Texas fatmucket, it 
qualifies as habitat according to our regulatory definition (50 CFR 
424.02).
    If the Texas fatmucket becomes reestablished in this reach, it will 
expand the occupied reach length in Onion Creek to a length that will 
be more resilient to the stressors that the species is facing. The 
longer the reach occupied by a species, the more likely it is that the 
population can withstand stochastic events such as extreme flooding, 
dewatering, or water contamination. The addition of this 18.9-mile 
reach to the 5.2-mile occupied section of Onion Creek would expand the 
existing Texas fatmucket population in Onion Creek to 25.1 miles. While 
this reach length is still less than 50 miles, (the stream length 
identified in the SSA report as a reach long enough for a population to 
be able to withstand stochastic events) the additional stream miles 
would substantially increase the resiliency of this population and 
dramatically reduce the likelihood of its extirpation. If this unit 
were established, it would likely be a moderately resilient population 
due to longer stream length and would increase the species' future 
redundancy This unit is essential for the conservation of the species 
because it will provide habitat for range expansion in portions of 
known historical habitat that is necessary to increase viability of the 
species by increasing its resiliency, redundancy, and representation.
    We are reasonably certain that this unit will contribute to the 
conservation of the species because it is an extension of a currently 
occupied unit and it supports the host fish of the species (PBF 2), as 
well as the appropriate flowing water conditions (PBF 1) periodically. 
Additionally, the need for conservation efforts is recognized and is 
being discussed by our conservation partners, and methods for restoring 
and reintroducing the species into unoccupied habitat are being worked 
on. The Texas fatmucket is listed as threatened by the State of Texas, 
and the Texas Comptroller of Public Accounts has funded research, 
surveys, propagation, and reintroduction studies for this species. 
State and Federal partners have shown interest in propagation and 
reintroduction efforts for the Texas fatmucket. As previously 
mentioned, efforts are underway regarding a captive propagation program 
for Texas fatmucket at the San Marcos Aquatic Resource Center and Inks 
Dam National Fish Hatchery. The State of Texas, San Marcos Aquatic 
Resource Center, Inks Dam National Fish

[[Page 47961]]

Hatchery, and the Service's Austin and Texas Coastal Field Offices 
collaborate regularly on conservation actions. Therefore, this 
unoccupied critical habitat subunit is essential for the conservation 
of the Texas fatmucket and is reasonably certain to contribute to such 
conservation.

Texas Fawnsfoot

    We are proposing to designate approximately 917.2 river mi (1,476.1 
km) in eight units (11 subunits) as critical habitat for Texas 
fawnsfoot. The critical habitat areas we describe below constitute our 
current best assessment of areas that meet the definition of critical 
habitat for Texas fawnsfoot. The eight areas we propose as critical 
habitat are: TXFF-1: Clear Fork Brazos River Unit; TXFF-2: Upper Brazos 
River Unit; TXFF-3: Lower Brazos River Unit; TXFF-4: Little River; 
TXFF-5: Lower San Saba and Upper Colorado River Unit; TXFF-6: Lower 
Colorado River Unit; TXFF-7: East Fork Trinity River Unit; and TXFF-8: 
Trinity River Unit. Table 11 shows the occupancy of the units, the 
riparian ownership, and approximate length of the proposed designated 
areas for the Texas fawnsfoot. We present brief descriptions of all 
proposed units, and reasons why they meet the definition of critical 
habitat for Texas fawnsfoot, below.

             Table 11--Proposed Critical Habitat Units for the Texas Fawnsfoot (Truncilla macrodon)
                                  [Note: Lengths may not sum due to rounding.]
----------------------------------------------------------------------------------------------------------------
                                                                                                  River miles
              Unit                      Subunit        Riparian ownership       Occupancy         (kilometers)
----------------------------------------------------------------------------------------------------------------
TXFF-1: Clear Fork Brazos River.  TXFF-1a: Upper       Private...........  Occupied..........        27.9 (44.9)
                                   Clear Fork Brazos
                                   River.
                                  TXFF-1b: Lower       Private...........  Unoccupied........        28.6 (46.0)
                                   Clear Fork Brazos
                                   River.
TXFF-2: Upper Brazos River......  ...................  Private...........  Occupied..........       79.9 (128.6)
TXFF-3: Lower Brazos River......  TXFF-3a: Lower       Private...........  Occupied..........      348.0 (560.0)
                                   Brazos River.
                                  TXFF-3b: Navasota    Private...........  Occupied..........        39.3 (63.2)
                                   River.
TXFF-4: Little River............  ...................  Private...........  Occupied..........        35.6 (57.3)
TXFF-5: Lower San Saba and Upper  TXFF-5a. Lower San   Private...........  Occupied..........        50.4 (81.1)
 Colorado River.                   Saba River.         Private...........  Occupied..........        10.5 (16.9)
                                  TXFF-5b. Upper
                                   Colorado River.
TXFF-6: Lower Colorado River....  ...................  Private...........  Occupied..........      124.4 (200.2)
TXFF-7: East Fork Trinity River.  ...................  Private...........  Occupied..........        15.6 (25.1)
TXFF-8: Trinity River...........  ...................  Private...........  Occupied..........      157.0 (252.7)
                                                                                              ------------------
    Total.......................  ...................  ..................  ..................    917.2 (1,476.1)
----------------------------------------------------------------------------------------------------------------

Brazos River Basin

Unit TXFF-1: Clear Fork of the Brazos River
    Subunit TXFF-1a: Upper Clear Fork of the Brazos River. The Upper 
Clear Fork of the Brazos River Subunit consists of approximately 27.9 
river mi (44.9 river km) in Throckmorton and Shackelford Counties, 
Texas. The subunit begins at the confluence of Paint Creek and extends 
downstream to the US Highway 283 bridge, near Fort Griffin, Texas. 
Adjacent riparian lands are privately owned. This subunit is occupied 
by Texas fawnsfoot and contains some of the PBFs essential to the 
conservation of the species, such as appropriate fish hosts and 
appropriate flows during portions of the year. The Upper Clear Fork of 
the Brazos River does not currently have sufficient flow, and water 
quality is often inadequate for the Texas fawnsfoot in this subunit, 
largely due to ongoing low-flow conditions from summertime drought and 
continued pressure on already strained water resources for municipal 
and agricultural uses.
    The Upper Clear Fork Brazos River subunit is in a rural setting and 
is influenced by drought, low flows, and chlorides. The subunit is 
being affected by ongoing agricultural activities and development, 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity.
    Subunit TXFF-1b: Lower Clear Fork of the Brazos River. Because we 
have determined occupied areas are not adequate for the conservation of 
the species, we have evaluated whether any unoccupied areas are 
essential for the conservation of Texas fawnsfoot and identified this 
area as essential for the conservation of the species. The Lower Clear 
Fork of the Brazos River Subunit consists of 28.6 river mi (46.0 river 
km) in Shackelford and Stephens Counties, Texas. This subunit begins at 
the US Highway 283 bridge and continues downstream to the US Highway 
183 bridge in Stephens County, Texas. Adjacent riparian lands are 
privately owned.
    This unit is essential to the conservation of Texas fawnsfoot 
because it would expand the most northern population; its loss would 
reduce the distribution of Texas fawnsfoot to only mainstem, higher 
order streams. Additionally, this population of Texas fawnsfoot is 
geographically distant from the other populations of the species, such 
that if a catastrophic event were to occur within the range of Texas 
fawnsfoot, such as extreme flooding or drought, it is likely that this 
population would not be affected in the same way, increasing the chance 
of the species surviving such an event. The Lower Clear Fork Brazos 
River Subunit is in a rural setting; is influenced by drought, low 
flows, and chlorides; and is being affected by ongoing agricultural 
activities and development, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals and surface water 
diversions, and wastewater inputs.
    Although it is considered unoccupied, portions of this subunit 
contain some or all of the physical or biological features essential 
for the conservation of the species. Flowing water at rates needed by 
Texas fawnsfoot (PBF 1) is not adequate in this subunit throughout most 
of the year due to low precipitation, surface diversions, and 
groundwater withdrawals. In the SSA report, we noted that the Lower 
Clear Fork of the Brazos River experienced both the lowest flow rate (0 
cfs) during the 2011 drought and the highest flow rate (approaching 
4,000 cfs) during the 2015 floods. This altered hydrological regime 
also degrades stream habitat (PBF 2) by either scouring out available 
substrate or depositing large amounts of sediment on top of otherwise 
suitable areas. Appropriate substrates are found only in isolated 
reaches. Management

[[Page 47962]]

actions that allow for improvement of degraded habitat areas within 
this subunit would allow Texas fawnsfoot populations to expand and 
increase the subunit's resiliency.
    Freshwater drum, the Texas fawnsfoot's host fish (PBF 3), is 
expected to be present in the Lower Clear Fork of the Brazos River. 
However, it remains unclear if the abundance of host fish for the Texas 
fawnsfoot is currently sufficient. Thus, management actions may be 
necessary to ensure appropriate populations of host fish are co-
occurring with Texas fawnsfoot.
    Water quality (PBF 4) may not be sufficient in the Lower Clear Fork 
of the Brazos River. Elevated chloride levels from naturally occurring 
underground salt formations are exacerbated by reduced water flow. In 
order for Texas fawnsfoot populations to expand and occupy the Lower 
Clear Fork of the Brazos River subunit, management actions would be 
necessary to reduce chloride levels.
    Because this reach of the Clear Fork Brazos River periodically 
contains the flowing water conditions and host fish species used by 
Texas fawnsfoot, it qualifies as habitat according to our regulatory 
definition (50 CFR 424.02).
    If the Texas fawnsfoot can be reestablished in this reach, it will 
expand the occupied reach length in the Clear Fork Brazos River to a 
length that will be more resilient to the stressors that the species is 
experiencing. The longer the reach occupied by a species, the more 
likely it is that the population can withstand stochastic events such 
as extreme flooding, dewatering, or water contamination. In the SSA 
report, we identified 50 miles (80.5 km) as a reach long enough for a 
population to be able to withstand stochastic events, and the addition 
of this 28.6-mile reach to the 27.9-mile occupied section of the Clear 
Fork Brazos River would expand the existing Texas fawnsfoot population 
in the Clear Fork Brazos River to 56.5 miles, achieving a length that 
would allow for a highly resilient population to be reestablished, 
increasing the species' future redundancy. This unit is essential for 
the conservation of the species because it will provide habitat for 
range expansion in portions of known historical habitat that is 
necessary to increase viability of the species by increasing its 
resiliency, redundancy, and representation.
    We are reasonably certain that this unit will contribute to the 
conservation of the species, because the need for conservation efforts 
is recognized and is being discussed by our conservation partners, and 
methods for restoring and reintroducing the species into unoccupied 
habitat are being developed. The Texas fawnsfoot is listed as 
threatened by the State of Texas, and the Texas Comptroller of Public 
Accounts has funded research, surveys, propagation, and reintroduction 
studies for this species. State and Federal partners have shown 
interest in propagation and reintroduction efforts for the Texas 
fawnsfoot. As previously mentioned, efforts are underway regarding a 
captive propagation program for Texas fawnsfoot at the San Marcos 
Aquatic Resource Center and Inks Dam National Fish Hatchery. The State 
of Texas, San Marcos Aquatic Resource Center, Inks Dam National Fish 
Hatchery, and the Service's Austin, Arlington and Texas Coastal Field 
Offices collaborate regularly on conservation actions for Texas 
fawnsfoot. Therefore, this unoccupied critical habitat subunit is 
essential for the conservation of the Texas fawnsfoot and is reasonably 
certain to contribute to such conservation.
Unit TXFF-2: Upper Brazos River
    The Upper Brazos River Unit consists of approximately 79.9 river mi 
(128.6 km) of the Brazos River in Palo Pinto and Parker Counties, 
Texas. The Upper Brazos River Unit extends from the FM 4 bridge 
crossing in Palo Pinto County, Texas, downstream to the FM 1189 bridge 
in Parker County, Texas. The unit is currently occupied by the species, 
and adjacent riparian lands are privately owned. This unit currently 
supports some of the PBFs essential to the conservation of Texas 
fawnsfoot, such as presence of appropriate fish hosts and suitable flow 
conditions during portions of the year, but becomes unsuitable during 
times of drought. The PBFs for water quality and sufficient flow are 
degraded in this unit, as excessive chloride concentrations and 
persistent low flows diminish habitat quality in this unit. Elevated 
chloride concentrations in this portion of Central Texas are often a 
result of natural causes, such as saline water inputs from spring 
releases flowing through subterranean salt deposits. However, while the 
Texas fawnsfoot may be able to tolerate some minor increases in 
salinity, low-flow rates in this unit exacerbate the concentrations of 
chlorides.
    The Upper Brazos River Unit is in a rural setting with some 
urbanization; is influenced by drought, low flows, chlorides, and 
reservoir operations; and is being affected by rock, sand and gravel 
mining, ongoing agricultural activities and development, resulting in 
excessive sedimentation, water quality degradation, ground water 
withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. Special management may be required to improve the water 
quantity, water quality, and habitat connectivity in this unit.
Unit TXFF-3: Lower Brazos River
    Subunit TXFF-3a: Lower Brazos River. The Lower Brazos River Subunit 
consists of approximately 348.0 river mi (560.0 km) in McLennan, Falls, 
Robertson, Milam, Burleson, Brazos, Washington, Grimes, Waller, Austin, 
and Fort Bend Counties, Texas. This subunit begins at the Texas State 
Highway 6 bridge crossing, downstream of Waco, Texas, to the Fort Bend 
and Brazoria county line. This subunit is occupied by Texas fawnsfoot 
and supports all of the PBFs essential to the conservation of the Texas 
fawnsfoot. Adjacent riparian lands are privately owned and include 
rural agricultural operations such as cattle grazing and row-crop 
agriculture. Because much of the historically forested floodplain has 
been deforested, bank sloughing and sedimentation is ongoing in this 
segment.
    The Lower Brazos River Subunit is in a rural setting with some 
urbanization; is influenced by drought, low flows, and reservoir 
operations; and is being affected by rock, sand and gravel mining, 
channel incision, ongoing agricultural activities and development, 
resulting in excessive sedimentation, water quality degradation, 
groundwater withdrawals and surface water diversions, and wastewater 
inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, restore 
riparian vegetation, and improve habitat connectivity. The Brazos River 
Authority (BRA) owns and manages surface water rights throughout the 
Brazos River basin, and, through operations of the BRA system of 
reservoirs, the BRA is able to manage flows in this subunit to some 
degree.
    Subunit TXFF-3b: Navasota River. The Navasota River Subunit 
consists of 39.3 river mi (63.2 river km) of the Navasota River in 
Brazos and Grimes Counties, Texas. This subunit extends from the State 
Highway 30 bridge downstream to the Brazos River confluence. Adjacent 
riparian lands to this subunit are primarily privately owned. The 
subunit is largely rural with agricultural practices dominating the 
surrounding landscape. This subunit is

[[Page 47963]]

occupied by the Texas fawnsfoot and supports the PBFs essential to the 
conservation of the species. The Navasota River has experienced water 
quality degradation (low dissolved oxygen and elevated bacteria) from 
adjacent land use practices, flow alterations associated with drought, 
and operation of the Lake Limestone reservoir. Additionally, this 
subunit has elevated levels of nitrate and phosphorus presumably from 
agricultural runoff. The Navasota River Subunit is in a rural setting 
with some urbanization; is influenced by drought, low flows, and 
reservoir operations; and is being affected by ongoing agricultural 
activities and development, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals and surface water 
diversions, and wastewater inputs. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, restore riparian vegetation, and improve habitat 
connectivity.

Colorado River Basin

Unit TXFF-4: Little River
    The Little River Unit consists of 35.6 river miles (57.3 km) of the 
Little River in Milam County, Texas. This subunit begins at the Bell 
and Milam county line and continues downstream to the confluence of the 
Little and San Gabriel rivers. The lands adjacent to the critical 
habitat unit are privately owned. The unit is currently occupied by the 
species and supports all of the PBFs essential to the conservation of 
the species. The Little River subunit is in a mostly rural setting, is 
influenced by ongoing development in the upper reaches associated with 
the Austin-Round Rock metropolitan area, and is being affected by 
ongoing agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, and groundwater withdrawals 
and surface water diversions. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. The Little River Unit 
is also occupied by false spike.
Unit TXFF-5: Lower San Saba River and Upper Colorado River
    Subunit TXFF-5a: Lower San Saba River. The Lower San Saba River 
Subunit consists of approximately 50.4 river mi (81.1 river km) in San 
Saba County, Texas. This subunit begins at the Brady Creek confluence 
and extends to the Colorado River confluence. Adjacent riparian lands 
are owned and are primarily in agricultural use. The river experiences 
periods of low flow due to drought and water withdrawals, and water 
withdrawals are expected to increase in the future. The subunit is 
occupied by Texas fawnsfoot and contains all of the PBFs essential to 
the conservation of the species. The Lower San Saba River Subunit is 
experiencing some urbanization and is influenced by drought, low flows, 
and wastewater discharges. The watershed is being affected by ongoing 
agricultural activities and development, resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and wastewater inputs. Therefore, special 
management is necessary to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. This subunit 
is also occupied by Texas pimpleback and false spike.
    Subunit TXFF-5b: Upper Colorado River. The Upper Colorado River 
Subunit consists of 10.5 river mi (16.9 river km) of the Colorado River 
near its confluence with the San Saba River in San Saba, Mills, and 
Lampasas Counties, Texas. This subunit extends from the County Road 124 
bridge and continues downstream to the US highway 190 bridge. 
Activities in the watershed are mostly agricultural. The river 
experiences periodic low flows from drought and upstream water 
withdrawals. The average daily flow rate of the upper Colorado River in 
this segment has been declining since the early 1920s. This subunit is 
currently occupied, and adjacent riparian lands are privately owned. 
All PBFs essential to the conservation of Texas fawnsfoot are present 
in this subunit, with the exception of appropriate flows throughout the 
year.
    The Upper Colorado River Subunit is influenced by reservoir 
operations and chlorides and is being affected by ongoing agricultural 
activities and development, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals and surface water 
diversions, and wastewater inputs. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. This subunit is also 
occupied by the Texas pimpleback.
Unit TXFF-6: Lower Colorado River
    The Lower Colorado River Unit consists of approximately 124.4 river 
mi (200.2 river km) of the Colorado River in Colorado, Wharton, and 
Matagorda Counties, Texas. This unit begins at the Fayette and Colorado 
county line and continues downstream to the Texas State Highway 35 
bridge near Bay City, Texas. Adjacent riparian habitats are privately 
owned. This unit is currently occupied by Texas fawnsfoot, and all PBFs 
essential to the conservation of the species are present in the unit. 
Upstream reservoir operation and urbanization in the Austin, Texas, 
metropolitan area contribute to altered flows and degraded water 
quality downstream.
    The Lower Colorado River Unit is in a mostly rural setting with 
some urbanization downstream from an urban area; is influenced by 
reservoir operations, drought, low flows, flooding (leading to scour), 
and wastewater discharges; and is being affected by ongoing 
agricultural activities and development, resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, wastewater inputs, and rock, sand and gravel 
mining. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. This subunit is also occupied by the 
Texas pimpleback.

Trinity River Basin

Unit TXFF-7: East Fork of the Trinity River
    This unit consists of approximately 15.6 river mi (25.1 km) of the 
East Fork of the Trinity River in Kaufman County, Texas. The East Fork 
of the Trinity River Unit extends from the Dallas and Kaufman county 
line downstream to the Trinity River confluence. This unit is currently 
occupied, and adjacent riparian lands are privately owned. Even though 
this unit is smaller than 50 miles, which we had determined was the 
reach length long enough to withstand stochastic events, the population 
increases the species' redundancy, making it more likely to withstand 
catastrophic events that may eliminate one or more of the other 
populations.
    Some of the PBFs essential to the conservation of Texas fawnsfoot 
are present, such as host fishes and appropriate substrate. The East 
Fork Trinity River Unit is in an urban setting; is influenced by 
drought, low flows, wastewater discharges, and flooding (leading to 
scour); and is being affected by ongoing development activities, 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation,

[[Page 47964]]

improve water quality, maintain adequate flows, and improve habitat 
connectivity, which would reduce the threats to the population, 
increasing the resiliency of the population.
Unit TXFF-8: Middle Trinity River
    The Middle Trinity River Unit consists of approximately 157.0 river 
mi (252.7 km) of the Trinity River in Navarro, Henderson, Freestone, 
Anderson, Leon, Houston, and Madison Counties, Texas. This unit extends 
from the State Highway 31 bridge, west of Trinidad, Texas, to the State 
Highway 21 bridge in Madison County. This unit is occupied, and 
adjacent riparian lands are privately owned. This unit provides all of 
the PBFs essential to the conservation of Texas fawnsfoot, although 
flows in this portion of the Trinity River are elevated above natural 
levels due to altered hydrology within the basin and daily high mean 
discharge approaching 80,000 cubic feet per second. Runoff and 
wastewater effluent release in the Dallas-Fort Worth metropolitan area 
result in daily pulses of high and low flow moving through the Trinity 
basin.
    The Middle Trinity River Unit is in a rural setting with some 
urbanization; is influenced by drought, low flows, wastewater 
discharges, reservoir operations, and flooding (leading to scour); and 
is being affected by channel incision, ongoing agricultural activities 
and development, resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals and surface water diversions, and 
wastewater inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, restore 
riparian vegetation, and improve habitat connectivity.

Guadalupe Orb

    We are proposing to designate approximately 294.5 river mi (474.0 
river km) in two units (four subunits) as critical habitat for 
Guadalupe orb. The critical habitat areas we describe below constitute 
our current best assessment of areas that meet the definition of 
critical habitat for Guadalupe orb. The two areas we propose as 
critical habitat are: GORB-1: Upper Guadalupe River Unit and GORB-2: 
Lower Guadalupe River Unit. Table 12 shows the occupancy of the units, 
the riparian ownership, and approximate length of the proposed 
designated areas for the Guadalupe orb. We present brief descriptions 
of all proposed units, and reasons why they meet the definition of 
critical habitat for Guadalupe orb, below.

                         Table 12--Proposed Critical Habitat Units for the Guadalupe Orb
                                  [Note: Lengths may not sum due to rounding.]
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
               Unit                       Subunit        Riparian ownership       Occupancy        (kilometers)
----------------------------------------------------------------------------------------------------------------
GORB-1: Upper Guadalupe River....  GORB-1a: South Fork   Private...........  Occupied..........        5.1 (8.3)
                                    Guadalupe River.
                                   GORB-1b: Upper        Private...........  Occupied..........     99.4 (159.9)
                                    Guadalupe River.
GORB-2: Lower Guadalupe River....  GORB-2a: San Marcos   Private...........  Occupied..........     65.3 (105.1)
                                    River.
                                   GORB-2b: Lower        Private...........  Occupied..........    124.7 (200.7)
                                    Guadalupe River.
                                                                                                ----------------
    Total........................  ....................  ..................  ..................    294.5 (474.0)
----------------------------------------------------------------------------------------------------------------

Guadalupe River Basin

Unit GORB-1: Upper Guadalupe River
    Subunit GORB-1a: South Fork Guadalupe River. The South Fork 
Guadalupe River Subunit consists of 5.1 river mi (8.3 river km) of the 
South Fork Guadalupe River in Kerr County, Texas. This subunit extends 
from Griffin Road crossing just downstream of the Texas Highway 39 
crossing in Kerr County, to its confluence with the North Fork 
Guadalupe River. This subunit is occupied by the Guadalupe orb, and the 
riparian area is privately owned. This subunit is mostly rural and 
agricultural, with organized recreational camps. These camps often 
operate very low dams that form small impoundments along the subunit. 
The South Fork Guadalupe River Subunit contains all of the PBFs 
essential to the conservation of the species. This subunit, combined 
with the Upper Guadalupe River subunit, results in a highly resilient 
population with presence in several tributaries, protecting the 
population from a single stochastic event eliminating the entire 
population.
    The South Fork Guadalupe River Subunit is in a mostly rural 
setting; is influenced by drought, low flows, and flooding (leading to 
scour); and is being affected by ongoing agricultural activities and 
development, resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity.
    Subunit GORB-1b: Upper Guadalupe River. The Upper Guadalupe River 
Subunit consists of 99.4 river mi (159.9 river km) of the Guadalupe 
River in Kerr, Kendall, and Comal Counties, Texas. This subunit extends 
from the confluence of the North and South Forks of the Guadalupe River 
downstream to the US Highway 311 bridge in Comal County, Texas. The 
Upper Guadalupe River is occupied by the Guadalupe orb, and adjacent 
riparian areas are privately owned. The subunit contains the PBFs 
essential to the conservation of the Guadalupe orb. In recent years, 
the Guadalupe orb in this reach have experienced some of the highest 
and lowest flows on record, as well as water quality degradation (high 
temperature and low dissolved oxygen). Extreme high flows removed 
needed gravel and cobble, while low flows caused suspended sediment to 
settle out, reducing substrate quality for the Guadalupe orb.
    The Upper Guadalupe River subunit is in a mostly rural setting with 
some urbanization; is influenced by drought, low flows, and flooding 
(leading to scour); and is being affected by ongoing agricultural 
activities and development, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals and surface water 
diversions, and wastewater inputs. Therefore, special management is 
necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. This subunit is also 
occupied by Guadalupe fatmucket.
Unit GORB-2: Lower Guadalupe River
    Subunit GORB-2a: San Marcos River. The San Marcos River Subunit 
consists of approximately 65.3 river miles (105.1 river km) in 
Caldwell, Guadalupe, and Gonzales Counties, Texas. The subunit extends 
from the FM 1977 bridge crossing in Caldwell County to the

[[Page 47965]]

Guadalupe River confluence. The subunit is currently occupied by the 
Guadalupe orb, and adjacent riparian areas are privately owned. The San 
Marcos River drains the City of San Marcos, including the campus of 
Texas State University, leading to impacts of urban runoff, waste water 
inputs, and altered hydrology. The large San Marcos springs complex, 
the second largest in Texas, contributes significantly to the flows in 
this river and the lower Guadalupe River. This segment contains all of 
the PBFs essential to the conservation of the species.
    The San Marcos River Subunit is in a mostly rural setting with some 
urbanization and downstream from an urban area; is influenced by 
drought, low flows, flooding (leading to scour), and wastewater 
discharges; and is being affected by ongoing agricultural activities 
and development, resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals and surface water diversions, and 
wastewater inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. This subunit is also occupied by the 
false spike.
    Subunit GORB-2b: Lower Guadalupe River. The Lower Guadalupe River 
Subunit consists of approximately 124.7 river mi (200.7 river km) in 
Gonzales, DeWitt, and Victoria Counties, Texas. This subunit extends 
from the San Marcos River confluence downstream to the US Highway 59 
bridge crossing near Victoria, Texas. The Lower Guadalupe River Subunit 
is currently occupied by the Guadalupe orb, and adjacent riparian areas 
are privately owned. This subunit contains all of the PBFs necessary 
for the Guadalupe orb and is the most resilient population known. 
Existing protections for the San Marcos and Comal Springs from the 
Edwards Aquifer Authority Habitat Conservation Plan provide some 
protection to spring flows and help ensure flow rates and water quality 
are generally believed to be suitable for downstream mussel beds during 
times of drought and low flows.
    The Lower Guadalupe River subunit is in a mostly rural setting with 
some urbanization downstream from some urban areas; is influenced by 
reservoir operations, drought, low flows, flooding (leading to scour), 
and wastewater discharges; and is being affected by ongoing 
agricultural activities and development, resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and wastewater inputs. Therefore, special 
management is necessary to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. This subunit 
is also occupied by the false spike.

Texas Pimpleback

    We are proposing to designate approximately 494.7 river mi (796.1 
km) in six units (10 subunits) as critical habitat for Texas 
pimpleback. The critical habitat areas we describe below constitute our 
current best assessment of areas that meet the definition of critical 
habitat for Texas pimpleback. The five areas we propose as critical 
habitat are: TXPB-1: Elm Creek Unit; TXPB-2: Concho River Unit; TXPB-3: 
Upper Colorado River/Lower San Saba River Unit; TXPB-4: Upper San Saba 
River Unit; TXPB-5: Llano River Unit; and TXPB-6: Lower Colorado River 
Unit. Table 13 shows the occupancy of the units, the riparian 
ownership, and approximate length of the proposed designated areas for 
the Texas pimpleback. We present brief descriptions of all proposed 
units, and reasons why they meet the definition of critical habitat for 
Texas pimpleback, below.

                       Table 13--Proposed Critical Habitat Units for the Texas Pimpleback
                                  [Note: Lengths may not sum due to rounding.]
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
              Unit                      Subunit         Riparian ownership       Occupancy         (kilometers)
----------------------------------------------------------------------------------------------------------------
TXPB-1: Elm Creek...............  TXPB-1a: Bluff       Private............  Occupied...........      11.8 (19.0)
                                   Creek.
                                  TXPB-1b: Lower Elm   Private............  Occupied...........      12.5 (20.2)
                                   Creek.
TXPB-2: Concho River............  TXPB-2a: Lower       Private............  Occupied...........      35.6 (57.2)
                                   Concho River.
                                  TXPB-2b. Upper       Private............  Unoccupied.........      16.0 (25.7)
                                   Concho River.
TXPB-3. Upper Colorado River/     TXPB-3a. Upper       Private............  Occupied...........    153.8 (247.6)
 Lower San Saba River.             Colorado River.     Private............  Occupied...........      50.4 (81.1)
                                  TXPB-3b. Lower San
                                   Saba River.
TXPB-4: Upper San Saba River....                       Private............  Occupied...........      52.8 (85.0)
TXPB-5: Llano River.............  TXPB-5a: Upper       Private............  Occupied...........      38.3 (61.6)
                                   Llano River.
                                  TXPB-5b: Lower       Private............  Unoccupied.........      12.2 (19.7)
                                   Llano River.
TXPB-6. Lower Colorado River....  ...................  Private............  Occupied...........    111.3 (179.1)
                                                                                                ----------------
    Total.......................  ...................  ...................  ...................    494.7 (796.1)
----------------------------------------------------------------------------------------------------------------

Colorado River Basin

Unit TXPB-1: Elm Creek
    Subunit TXPB-1a: Bluff Creek. This occupied critical habitat 
subunit consists of 11.8 river mi (19.0 km) of Bluff Creek, a tributary 
to Elm Creek, in Runnels County, Texas. The subunit extends from the 
County Road 153 bridge crossing, near the town of Winters, Texas, 
downstream to the confluences of Bluff and Elm creeks. The riparian 
area of this subunit is privately owned. This subunit is currently 
occupied by Texas pimpleback. The Bluff Creek subunit is in a rural 
setting, is influenced by drought, low flows, and elevated chlorides, 
and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. This subunit is also occupied by Texas fatmucket.
    Subunit TXPB-1b: Lower Elm Creek. This subunit consists of 12.5 
river mi (20.2 km) of Elm Creek beginning at the County Road 344 
crossing downstream to Elm Creek's confluence with the Colorado River 
in Runnels County, Texas. The riparian lands adjacent to this subunit 
are privately owned. The Elm Creek watershed is relatively small and 
remains largely rural and dominated by agricultural practices. This 
stream regularly has extremely low or no flow during times of drought. 
Moreover, this stream has elevated chloride concentrations and

[[Page 47966]]

sedimentation resulting in reduced habitat quality and availability, 
and decreased water quality. Lower Elm Creek is occupied by Texas 
pimpleback and contains some of the PBFs essential to the conservation 
of the species such as presence of host fish; others are in degraded 
condition and would benefit from management actions. The Lower Elm 
Creek subunit is influenced by drought, low flows, and elevated 
chlorides, and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, and groundwater withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. This unit is also occupied by Texas fatmucket.
Unit TXPB-2: Concho River
    Subunit TXPB-2a: Lower Concho River. The Lower Concho River Subunit 
consists of approximately 35.6 river mi (57.2 river km) in Tom Green 
and Concho Counties, Texas. The Concho River subunit extends from the 
FM 1692 bridge crossing downstream to the FM 1929 crossing. This 
subunit is occupied, and its riparian area is privately owned. The 
Lower Concho River Subunit does not currently contain all of the PBFs 
essential to the conservation of the Texas pimpleback, as it does not 
currently have sufficient water quality (e.g., water temperature is 
high and dissolved oxygen is low) and instream flow is too low at 
certain times of the year. Upstream reservoirs, built for flood control 
and municipal water storage, have contributed to a downward trend in 
normal river base-flows in recent years. The Lower Concho River subunit 
is in a mostly rural setting downstream from an urban area, is 
influenced by reservoir operations and chlorides, and is being affected 
by ongoing agricultural activities and development resulting in 
excessive sedimentation, water quality degradation, ground water 
withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity.
    Subunit TXPB-2b: Upper Concho River. Because we have determined 
occupied areas are not adequate for the conservation of the species, we 
have evaluated whether any unoccupied areas are essential for the 
conservation of Texas pimpleback and identified this area as essential 
for the conservation of the species. The Upper Concho River subunit 
consists of 16.0 river mi (25.7 river km) of the Concho River in Tom 
Green County, Texas, from the FM 380 bridge crossing, downstream of San 
Angelo, Texas, to the FM 1692 bridge where it adjoins subunit TXPB-2a. 
The riparian lands adjacent to this subunit are privately owned.
    This subunit is essential to the conservation of Texas pimpleback 
because it would expand one of the smaller populations to a length that 
would be highly resilient to stochastic events; its loss would shrink 
the distribution of Texas pimpleback and reduce redundancy of the 
species, limiting its viability. The Upper Concho River subunit is in a 
mostly rural setting with some urbanization downstream from an urban 
area; is influenced by reservoir operations, wastewater discharges, and 
chlorides; and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, groundwater withdrawals and surface water diversions, and 
wastewater inputs.
    Although it is considered unoccupied, portions of this subunit 
contain some or all of the physical or biological features essential 
for the conservation of the species. Flowing water (PBF 1) is not at 
levels appropriate for Texas pimpleback in this subunit. Several 
upstream reservoirs divert the already limited flows, and reduced 
precipitation has resulted in an overall decrease in river flow rates. 
Management actions to increase stream flows in this subunit would be 
required for the Texas pimpleback population to be reestablished.
    Currently, appropriate substrates (PBF 2) exist in isolated areas 
throughout this subunit. These isolated pockets of suitable habitat 
could allow for expansion and recolonization of Texas pimpleback. 
However, future management actions that focus on habitat restoration in 
this reach to improve connectivity between habitat patches would 
improve the resiliency of this population, once restored.
    Recent research on the closely related Guadalupe orb indicated that 
several species of catfishes are likely suitable host fishes for Texas 
pimpleback, as well. Currently, we believe appropriate host fishes (PBF 
3) are occurring throughout the subunit and would allow for 
reproduction of Texas pimpleback when the species is reestablished. 
Management actions could address any deficit in the abundance and 
distribution of fish hosts in this area allowing for expansion and 
future reestablishment of this subunit from the adjacent occupied 
subunit TXPB-2a.
    Water quality (PBF 4) is degraded in this subunit. The Upper Concho 
River subunit, due in part to low flows and high water temperature, 
experiences decreased levels of dissolved oxygen at such a level that 
could preclude mussel occupancy. We believe these periods of low 
dissolved oxygen primarily occur during hot summer months when droughts 
are common. Therefore, management actions that increase flow rates 
would also improve water quality in this reach.
    Because this reach of the Concho River periodically contains the 
appropriate substrate conditions and host fish species used by Texas 
pimpleback, it qualifies as habitat according to our regulatory 
definition (50 CFR 424.02).
    If the Texas pimpleback can be reestablished in this reach, it will 
expand the occupied reach length in the Concho River to a length that 
will be more resilient to the stressors that the species is facing. The 
longer the reach occupied by a species, the more likely it is that the 
population can withstand stochastic events such as extreme flooding, 
dewatering, or water contamination. In the SSA report, we identified 50 
miles (80.5 km) as a reach long enough for a population to be able to 
withstand stochastic events, and the addition of this 16.0-mile reach 
to the 35.6-mile occupied section of the Concho River would expand the 
existing Texas fawnsfoot population in the Concho River to 51.6 miles, 
achieving a length that would allow for a highly resilient population 
to be reestablished, increasing the species' future redundancy. This 
unit is essential for the conservation of the species because it will 
provide habitat for range expansion in portions of known historical 
habitat that is necessary to increase viability of the species by 
increasing its resiliency, redundancy, and representation.
    We are reasonably certain that this unit will contribute to the 
conservation of the species, because the need for conservation efforts 
is recognized and is being discussed by our conservation partners, and 
methods for restoring and reintroducing the species into unoccupied 
habitat are being worked on. The Texas pimpleback is listed as 
threatened by the State of Texas, and the Texas Comptroller of Public 
Accounts has funded research, surveys, propagation, and reintroduction 
studies for this species. State and Federal partners have shown 
interest in propagation and reintroduction efforts for the Texas 
pimpleback. As previously mentioned, efforts are underway regarding a 
captive propagation program

[[Page 47967]]

for Texas pimpleback at the San Marcos Aquatic Resource Center and Inks 
Dam National Fish Hatchery. The State of Texas, San Marcos Aquatic 
Resource Center, Inks Dam National Fish Hatchery, and the Service's 
Austin and Texas Coastal Field Offices collaborate regularly on 
conservation actions. Therefore, this unoccupied critical habitat 
subunit is essential for the conservation of the Texas pimpleback and 
is reasonably certain to contribute to such conservation.
Unit TXPB-3: Upper Colorado River and Lower San Saba River
    Subunit TXPB-3a: Upper Colorado River. The Upper Colorado River 
Subunit consists of approximately 153.8 river mi (247.6 river km) in 
Coleman, McCulloch, Brown, San Saba, Mills, and Lampasas Counties, 
Texas. The subunit extends from the Coleman and McCulloch county line 
downstream to the confluence of the Colorado River and Cherokee Creek. 
The riparian area of this subunit is privately owned. The Upper 
Colorado River is occupied by Texas pimpleback and contains some of the 
PBFs essential to the conservation of the species, including host 
fishes in appropriate abundance and small areas of suitable substrate 
habitat, but not several PBFs, such as sufficient flow rate and 
sufficient water quality (dissolved oxygen is often low, and 
temperature reaches unsuitably high levels during summer drought). The 
Upper Colorado River subunit is in a mostly rural setting, is 
influenced by reservoir operations and chlorides, and is being affected 
by ongoing agricultural activities and development resulting in 
excessive sedimentation, water quality degradation, groundwater 
withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. This subunit is also occupied by Texas fawnsfoot.
    Subunit TXPB-3b: Lower San Saba River. The Lower San Saba River 
Subunit consists of 50.4 river mi (81.1 river km) of the San Saba 
River. This subunit is currently occupied by the species, and adjacent 
riparian areas are privately owned. The Lower San Saba Subunit extends 
from the Brady Creek confluence in San Saba County, Texas, downstream 
to the Colorado River confluence where it adjoins the Upper Colorado 
River subunit (TXPB-3a). This subunit contains all the PBFs essential 
to the conservation of the Texas pimpleback most of the year. This 
population contains evidence of recent Texas pimpleback reproduction, 
which is largely absent from the rest of the species' range.
    This subunit is primarily rural, with cattle grazing and irrigated 
orchards. Summer drought and water withdrawals cause occasional periods 
of low flow, which results in water quality degradation as water 
temperatures are high and dissolved oxygen is low. Additionally, high-
flow events during flooding can result in habitat scour and 
sedimentation. The Lower San Saba River Subunit is experiencing some 
urbanization; is influenced by drought, low flows, and wastewater 
discharges; and is being affected by ongoing agricultural activities 
and development, resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals and surface water diversions, and 
wastewater inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. This subunit is also occupied by Texas 
fawnsfoot and false spike.
Unit TXPB-4: Upper San Saba River
    The Upper San Saba River Unit consists of approximately 52.8 river 
mi (85.0 river km) of the San Saba River in Menard County, Texas. 
Adjacent riparian habitats are privately owned. The Upper San Saba 
River Unit extends from the Schleicher County line near Fort McKavett, 
Texas, downstream to the FM 1311 bridge crossing in Menard, County, 
Texas. Texas pimpleback occupies the Upper San Saba River Unit in low 
densities. The Upper San Saba River Unit contains the PBFs essential to 
the conservation of Texas pimpleback most of the year, although flows 
decline to low levels during summer drought. The PBFs of sufficient 
water flow and water quality are lacking during these times, as low-
flow conditions lead to high water temperature and low dissolved 
oxygen. The Upper San Saba River unit is in a rural setting; is 
influenced by drought, low flows, and underlying geology resulting in a 
losing reach; and is being affected by ongoing agricultural activities 
and development resulting in excessive sedimentation, water quality 
degradation, groundwater withdrawals and surface water diversions, and 
collection. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. This subunit is also occupied by Texas 
fatmucket.
Unit TXPB-5: Llano River
    Subunit TXPB-5a: Upper Llano River. The Upper Llano River Subunit 
consists of approximately 38.3 river mi (61.6 river km) in Kimble and 
Mason Counties, Texas. Adjacent riparian areas are privately owned. 
This subunit extends from the Ranch Road RR 385 bridge crossing 
downstream to the US Highway 87 bridge. This reach of the Llano River 
is largely rural, with much of the land in agricultural use. The Upper 
Llano River Subunit is occupied by the Texas pimpleback and contains 
all the necessary PBFs essential to the conservation of the species 
most of the year. However, drought conditions and flooding in the Llano 
River can be extreme, causing the species to experience either extreme 
low-flow conditions with related reduced water quality or extreme high 
flows that mobilize substrate, eroding habitat or depositing sediment 
on Texas pimpleback populations. The Upper Llano River Subunit is in a 
rural setting; is influenced by drought, low flows, and flooding 
(leading to scour); and is being affected by ongoing agricultural 
activities and development resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals and surface water 
diversions, and collection. Therefore, special management is necessary 
to reduce sedimentation, improve water quality, maintain adequate 
flows, improve habitat connectivity, and manage collection. This 
subunit is also occupied by Texas fatmucket.
    Subunit TXPB-5b: Lower Llano River. Because we have determined 
occupied areas are not adequate for the conservation of the species, we 
have evaluated whether any unoccupied areas are essential for the 
conservation of Texas pimpleback and identified this area as essential 
for the conservation of the species. The Lower Llano River Subunit 
consists of 12.2 river mi (19.7 river km) of the Llano River. This 
subunit extends from the US Highway 87 bridge in Mason County 
downstream to the Mason and Llano county line. Adjacent riparian lands 
are privately owned.
    This subunit is essential to the conservation of Texas pimpleback 
because it would expand one of the smaller populations to a length that 
would be highly resilient to stochastic events in a separate tributary; 
its loss would reduce the distribution of Texas pimpleback and reduce 
redundancy of the species, limiting its viability. The Lower Llano 
River Subunit is in a rural setting; is influenced by drought, low 
flows, and flooding (leading to scour);

[[Page 47968]]

and is being affected by ongoing agricultural activities and 
development, resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions.
    Although it is considered unoccupied, portions of this subunit 
contain some or all of the physical or biological features essential 
for the conservation of the species. Flowing water (PBF 1) is generally 
sufficient in this subunit during portions of the year. However, in the 
past decade the Llano River has seen both the highest and lowest flow 
rates ever recorded, with extremely low water levels and stranding of 
mussels during low flow, and scour and entrainment of mussels with 
subsequent deposition over suitable habitat during floods. Spring 
inputs from the South Llano River help mitigate the effects of drought 
in the lower portions of the Llano River, although water withdrawals 
for agricultural operations contribute to decreased flows during 
drought. Ongoing management actions by resource management agencies and 
non-profit organizations are contributing to restoring a natural flow 
regime.
    In the Llano River, suitable substrates (PBF 2) exist as isolated 
riffles between larger pools. Given the hydrology of the Llano River 
basin, suitable substrates have been degraded in this reach and would 
need restoration.
    The Texas pimpleback uses similar host fishes as the closely 
related Guadalupe orb, including channel catfish, flathead catfish, and 
tadpole madtom. Sufficient abundance of host fishes (PBF 3) are present 
in the lower Llano River subunit to support a population of Texas 
pimpleback.
    Water quality in the lower Llano River subunit (PBF 4) are 
generally sufficient for the species during portions of the year. 
However, dissolved oxygen declines and water temperature increases 
during periods of low flow. Management to ensure sufficient flow rates 
in this reach will improve water quality as well.
    Because this reach of the Llano River periodically contains the 
flowing water conditions, suitable substrates, and host fish species 
used by Texas pimpleback, it qualifies as habitat according to our 
regulatory definition (50 CFR 424.02).
    If the Texas pimpleback can be reestablished in this reach, it will 
expand the occupied reach length in the Llano River to a length that 
will be more resilient to the stressors that the species is facing. The 
longer the reach occupied by a species, the more likely it is that the 
population can withstand stochastic events such as extreme flooding, 
dewatering, or water contamination. In the SSA report, we identified 50 
miles (80.5 km) as a reach long enough for a population to be able to 
withstand stochastic events, and the addition of this 12.2-mile reach 
to the 38.3-mile occupied section of the Llano River would expand the 
existing Texas pimpleback population in the Llano River to 50.5 miles, 
achieving a length that would allow for a highly resilient population 
to be reestablished, increasing the species' future redundancy. This 
unit is essential for the conservation of the species because it will 
provide habitat for range expansion in portions of known historical 
habitat that is necessary to increase viability of the species by 
increasing its resiliency, redundancy, and representation.
    We are reasonably certain that this unit will contribute to the 
conservation of the species, because the need for conservation efforts 
is recognized and is being discussed by our conservation partners, and 
methods for restoring and reintroducing the species into unoccupied 
habitat are being worked on. The Texas pimpleback is listed as 
threatened by the State of Texas, and the Texas Comptroller of Public 
Accounts has funded research, surveys, propagation, and reintroduction 
studies for this species. State and Federal partners have shown 
interest in propagation and reintroduction efforts for the Texas 
pimpleback. As previously mentioned, efforts are underway regarding a 
captive propagation program for Texas pimpleback at the San Marcos 
Aquatic Resource Center and Inks Dam National Fish Hatchery. The State 
of Texas, San Marcos Aquatic Resource Center, Inks Dam National Fish 
Hatchery, and the Service's Austin and Texas Coastal Field Offices 
collaborate regularly on conservation actions.
    Therefore, this unoccupied critical habitat subunit is essential 
for the conservation of the Texas pimpleback and is reasonably certain 
to contribute to such conservation. This subunit is also occupied by 
Texas fatmucket and false spike.
Unit TXPB-6: Lower Colorado River
    The Lower Colorado River Unit consists of approximately 111.3 river 
mi (179.1 river km) of the Colorado River in Colorado and Wharton 
Counties, Texas. The Lower Colorado River unit extends from the Fayette 
and Colorado County line downstream to the Wharton and Matagorda County 
line. The unit is currently occupied, and adjacent riparian lands are 
privately owned. This unit contains all of the PBFs essential to the 
conservation of Texas pimpleback. Periodic low flows due to drought and 
water management activities contribute to diminished and variable 
flows, dewatering, scour, and water quality decline from urban run-off, 
agricultural operations, and wastewater treatment effluent. The Lower 
Colorado River Unit is in a mostly rural setting with some urbanization 
downstream from an urban area and is influenced by reservoir 
operations, drought, low flows, flooding (leading to scour), and 
wastewater discharges. The unit is being affected by ongoing 
agricultural activities and development, resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, wastewater inputs, and rock, sand and gravel 
mining. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. This subunit is also occupied by Texas 
fatmucket.

False Spike

    We are proposing to designate approximately 328.2 river mi (528.2 
km) in four units (seven subunits) as critical habitat for false spike. 
Each of the seven subunits is currently occupied by the species and 
contains all of the PBFs essential to the conservation of the species. 
The critical habitat areas we describe below constitute our current 
best assessment of areas that meet the definition of critical habitat 
for false spike. The four areas we propose as critical habitat are: 
FASP-1: Little River Unit; FASP-2: San Saba River Unit; FASP-3: Llano 
River Unit; and FASP-4: Guadalupe River Unit. Table 14 shows the 
occupancy of the units, the riparian ownership, and approximate length 
of the proposed designated areas for the false spike. We present brief 
descriptions of all proposed units, and reasons why they meet the 
definition of critical habitat for false spike, below.

[[Page 47969]]



                            Table 14--Proposed Critical Habitat Units for False Spike
                                   [Note: Lengths may not sum due to rounding]
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
               Unit                       Subunit        Riparian ownership       Occupancy        (kilometers)
----------------------------------------------------------------------------------------------------------------
FASP-1: Little River.............  FASP-1a: Little       Private...........  Occupied..........      35.6 (57.3)
                                    River.
                                   FASP-1b: San Gabriel  Private...........  Occupied..........      31.4 (50.5)
                                    River.
                                   FASP-1c: Brushy       Private...........  Occupied..........      14.0 (22.5)
                                    Creek.
FASP-2: San Saba River...........  ....................  Private...........  Occupied..........      50.4 (81.1)
FASP-3: Llano River..............  ....................  Private...........  Occupied..........      50.5 (81.3)
FASP-4: Guadalupe River..........  FASP-4a: San Marcos   Private...........  Occupied..........      21.6 (34.8)
                                    River.
                                   FASP-4b: Guadalupe    Private...........  Occupied..........    124.7 (200.7)
                                    River.
                                                                                                ----------------
    Total........................  ....................  ..................  ..................    328.2 (528.2)
----------------------------------------------------------------------------------------------------------------

Brazos River Basin
Unit FASP-1: Little River
    Subunit FASP-1a: Little River. This subunit consists of 35.6 river 
miles (57.3 km) of the Little River in Milam County, Texas. This 
subunit begins at the Bell and Milam county line and continues 
downstream to the confluence of the Little and San Gabriel Rivers. The 
lands adjacent to the critical habitat unit are privately owned. The 
unit is currently occupied by the species and supports all of the PBFs 
essential to the conservation of the species. The Little River subunit 
is in a mostly rural setting, is influenced by ongoing development in 
the upper reaches associated with the Austin-Round Rock metropolitan 
area, and is being affected by ongoing agricultural activities and 
development resulting in excessive sedimentation, water quality 
degradation, and ground water withdrawals and surface water diversions. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. This subunit is also occupied by the Texas fawnsfoot.
    Subunit FASP-1b: San Gabriel River. This subunit consists of 31.4 
river mi (50.5 km) of the San Gabriel River in Williamson and Milam 
Counties, Texas. The subunit starts downstream of the Granger Lake dam 
(at the downstream edge of the Pecan Grove State Wildlife Management 
Area) and continues through Williamson County to the confluence of the 
San Gabriel and Little Rivers in Milam County. The land adjacent to 
this subunit is all privately owned. The San Gabriel River subunit is 
currently occupied by the species and currently supports all of the 
PBFs essential to the conservation of the species. The San Gabriel 
River subunit is in a rural setting, is influenced by releases from 
Granger Reservoir, and is being affected by ongoing agricultural 
activities and development resulting in excessive sedimentation, water 
quality degradation, and ground water withdrawals and surface water 
diversions. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity.
    Subunit FASP-1c: Brushy Creek. The subunit consists of 14.0 river 
mi (22.5 km) of Brushy Creek in Milam County, Texas. The subunit begins 
at the US Highway 79 bridge crossing and extends downstream to the 
confluence with Brushy Creek and the San Gabriel River. The unit is 
currently occupied by the species, and the adjacent riparian areas are 
privately owned. This stream drains a large portion of the City of 
Cedar Park, resulting in altered hydrology, altered flow regimes, and 
increased sedimentation. Brushy Creek contains some of the PBFs 
essential to the conservation of the false spike, such as adequate fish 
hosts, but other factors like water flow rates and water quality 
parameters may not be adequate during summer low-flow periods. The 
Brushy Creek subunit is in a rural but urbanizing setting, and it is 
influenced by wastewater discharges and ongoing development in the 
upper reaches associated with the Austin-Round Rock metropolitan area. 
It is also being affected by ongoing development and agricultural 
activities resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals and surface water diversions, and 
wastewater inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. Additionally, hydrological alterations in 
this watershed result in scour and mobilization of sediment during 
times of high-flow rates, resulting in loss of appropriate mussel 
habitat. Special management considerations for this area could include 
the highest level of wastewater treatment, decreased pollutant inputs 
from surface flows, bank stabilization, and increased flows during low-
flow periods.
Colorado River Basin
Unit FASP-2: San Saba River
    This unit consists of 50.4 river mi (81.1 km) of the San Saba River 
in San Saba County, Texas. The unit extends from the San Saba River and 
Brady Creek confluence and continues downstream to the confluence of 
the San Saba and Colorado Rivers. The riparian land adjacent to the 
critical habitat unit is privately owned. The unit is currently 
occupied by the species and contains all of the PBFs essential to the 
conservation of false spike. The San Saba River subunit is in a rural 
setting, is influenced by drought, low flows, and wastewater 
discharges, and is being affected by ongoing agricultural activities 
and development resulting in excessive sedimentation, water quality 
degradation, groundwater withdrawals and surface water diversions, and 
wastewater inputs. Therefore, special management is necessary to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. Much of the land use in the watershed is 
agricultural, and special management considerations or protection may 
be required to address excess nutrients, sediment, and pollutants that 
enter the San Saba River and reduce instream water quality. Sources of 
these types of pollution are wastewater, agricultural runoff, and urban 
stormwater runoff. Additional special management considerations or 
protection may be required in this unit to address low water levels 
that result from water withdrawals and drought, as well as excessive 
erosion. This subunit is also occupied by Texas pimpleback.
Unit FASP-3: Llano River
    This unit consists of 50.5 river mi (81.3 km) of the Llano River in 
Kimble and Mason Counties, Texas. The Llano River unit begins at the 
Ranch Road 385 bridge crossing in Kimble County and

[[Page 47970]]

continues downstream to the Mason and Llano County line. The unit is 
occupied by the species, and surrounding riparian areas are privately 
owned. The majority of the Llano River basin is rural and composed of 
agricultural operations that were historically used for sheep and goat 
ranching. During 2018, the Llano River experienced some of the largest 
floods and most severe drought within the same year. Extreme floods and 
drought conditions result in both stream bed mobilization, 
sedimentation, and dewatering. The Llano River unit contains all the 
PBFs essential to the conservation of false spike. The Llano River unit 
is in a rural setting; is influenced by drought, low flows, and 
flooding (leading to scour); and is being affected by ongoing 
agricultural activities and development resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and collection. Therefore, special management 
is necessary to reduce sedimentation, improve water quality, maintain 
adequate flows, improve habitat connectivity, and manage collection. 
Additionally, special management may be required to address excess 
nutrients, sediment, and pollutants, as well as exceptionally low and 
high flows. This subunit is also occupied by Texas fatmucket, Texas 
fawnsfoot, and Texas pimpleback.
Guadalupe River Basin
Unit FASP-4: Guadalupe River
    Subunit FASP-4a: San Marcos River. This subunit consists of 21.6 
river mi (34.8 km) of the San Marcos River in Gonzales County, Texas. 
The San Marcos River subunit begins at the Farm-to-Market (FM) 2091 
bridge crossing within Palmetto State Park (Park Road 11) and continues 
for 21.7 river miles downstream to the San Marcos River confluence with 
the Guadalupe River. The riparian lands adjacent to this subunit are 
primarily privately owned; Texas Parks and Wildlife Department's 
Palmetto State Park occurs in the upstream reaches. The San Marcos 
River drains the City of San Marcos, including the campus of Texas 
State University, which causes the river to be impacted by urban 
runoff, wastewater inputs, and altered hydrology. The San Marcos 
springs complex, the second largest in Texas, contributes significantly 
to the flows in this river and the lower Guadalupe River. The lower San 
Marcos River watershed is characterized by agricultural land in the 
lower portion of the San Marcos River. The subunit is occupied by the 
false spike and contains all of the PBFs essential to the conservation 
of the species. Because the San Marcos River subunit is downstream from 
an urban area in a rural but urbanizing setting, it is influenced by 
wastewater discharges and ongoing development in the upper reaches 
associated with the Austin-Round Rock metropolitan area. It is also 
being affected by ongoing development and agricultural activities 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals and surface water diversions, and wastewater inputs. 
Therefore, special management is necessary to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. Special management considerations may be required to 
address riparian bank sloughing, increased sedimentation, and 
pollutants from upstream urbanization and agricultural practices. This 
subunit is also occupied by Guadalupe orb.
    Subunit FASP-4b: Guadalupe River. This subunit consists of 124.7 
river mi (200.7 km) of the Guadalupe River in Gonzales, DeWitt, and 
Victoria Counties, Texas. The Guadalupe River subunit begins at the 
confluence of the Guadalupe and San Marcos Rivers and continues 
downstream for 124.7 river miles to the US highway 59 bridge near 
Victoria, Texas. Adjacent riparian areas within this subunit are 
privately owned. This subunit is occupied by the false spike and 
contains all of the PBFs essential to the conservation of the species. 
The Guadalupe River subunit is in a mostly rural but urbanizing 
setting, is influenced by reservoir releases (from Canyon and Guadalupe 
Valley) and flooding (leading to scour), and is being affected by 
ongoing development and agricultural activities resulting in excessive 
sedimentation, water quality degradation, ground water withdrawals and 
surface water diversions, and wastewater inputs. Therefore, special 
management is necessary to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. This subunit 
contains the most resilient known population of false spike. During 
times of drought, spring water influence from the Comal and San Marcos 
Rivers can contribute as much as 50 percent of the flows to the lower 
Guadalupe River. Continued protections for these spring systems are 
imperative for protecting mussel beds in the lower Guadalupe River. 
Special management considerations may be required to ensure low flows, 
sedimentation, and degraded water quality parameters do not worsen and 
contribute to future population decline. This subunit is also occupied 
by Guadalupe orb.

Effects of Critical Habitat Designation

Section 7 Consultation

    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is proposed or listed as an 
endangered or threatened species and with respect to its critical 
habitat, if any is designated. Section 7(a)(2) of the Act requires 
Federal agencies, including the Service, to ensure that any action they 
fund, authorize, or carry out is not likely to jeopardize the continued 
existence of any endangered species or threatened species or result in 
the destruction or adverse modification of designated critical habitat 
of such species. In addition, section 7(a)(4) of the Act requires 
Federal agencies to confer with the Service on any agency action that 
is likely to jeopardize the continued existence of any species proposed 
to be listed under the Act or result in the destruction or adverse 
modification of proposed critical habitat.
    We published a final regulation with a revised definition of 
destruction or adverse modification on August 27, 2019 (84 FR 44976). 
Destruction or adverse modification means a direct or indirect 
alteration that appreciably diminishes the value of critical habitat as 
a whole for the conservation of a listed species.
    If a Federal action may affect a listed species or its critical 
habitat, the responsible Federal agency (action agency) must enter into 
consultation with us. Examples of actions that are subject to the 
section 7 consultation process are actions on State, tribal, local, or 
private lands that require a Federal permit or that involve some other 
Federal action. Federal agency actions within the species' habitat that 
may require conference or consultation or both include management and 
any other landscape-altering activities on Federal lands administered 
by the U.S. Fish and Wildlife Service, Army National Guard, U.S. Forest 
Service, and National Park Service; issuance of section 404 Clean Water 
Act (33 U.S.C. 1251 et seq.) permits by the U.S. Army Corps of 
Engineers; and construction and maintenance of roads or highways by the 
Federal Highway Administration. Federal actions not affecting listed 
species or critical habitat, and actions on State, tribal, local, or 
private lands that are not federally funded, authorized, or carried out 
by a Federal agency, do not require section 7 consultation.

[[Page 47971]]

    Compliance with the requirements of section 7(a)(2), is documented 
through our issuance of:
    (1) A concurrence letter for Federal actions that may affect, but 
are not likely to adversely affect, listed species or critical habitat; 
or
    (2) A biological opinion for Federal actions that may affect, and 
are likely to adversely affect, listed species or critical habitat.
    When we issue a biological opinion concluding that a project is 
likely to jeopardize the continued existence of a listed species and/or 
destroy or adversely modify critical habitat, we provide reasonable and 
prudent alternatives to the project, if any are identifiable, that 
would avoid the likelihood of jeopardy and/or destruction or adverse 
modification of critical habitat. We define ``reasonable and prudent 
alternatives'' (at 50 CFR 402.02) as alternative actions identified 
during consultation that:
    (1) Can be implemented in a manner consistent with the intended 
purpose of the action,
    (2) Can be implemented consistent with the scope of the Federal 
agency's legal authority and jurisdiction,
    (3) Are economically and technologically feasible, and
    (4) Would, in the Service Director's opinion, avoid the likelihood 
of jeopardizing the continued existence of the listed species and/or 
avoid the likelihood of destroying or adversely modifying critical 
habitat.
    Reasonable and prudent alternatives can vary from slight project 
modifications to extensive redesign or relocation of the project. Costs 
associated with implementing a reasonable and prudent alternative are 
similarly variable.
    Regulations at 50 CFR 402.16 set forth requirements for Federal 
agencies to reinitiate formal consultation on previously reviewed 
actions. These requirements apply when the Federal agency has retained 
discretionary involvement or control over the action (or the agency's 
discretionary involvement or control is authorized by law) and, if 
subsequent to the previous consultation: (1) If the amount or extent of 
taking specified in the incidental take statement is exceeded; (2) if 
new information reveals effects of the action that may affect listed 
species or critical habitat in a manner or to an extent not previously 
considered; (3) if the identified action is subsequently modified in a 
manner that causes an effect to the listed species or critical habitat 
that was not considered in the biological opinion; or (4) if a new 
species is listed or critical habitat designated that may be affected 
by the identified action. In such situations, Federal agencies 
sometimes may need to request reinitiation of consultation with us, but 
the regulations also specify some exceptions to the requirement to 
reinitiate consultation on specific land management plans after 
subsequently listing a new species or designating new critical habitat. 
See the regulations for a description of those exceptions.

Application of the ``Adverse Modification'' Standard

    The key factor related to the destruction or adverse modification 
determination is whether implementation of the proposed Federal action 
directly or indirectly alters the designated critical habitat in a way 
that appreciably diminishes the value of the critical habitat as a 
whole for the conservation of the listed species. As discussed above, 
the role of critical habitat is to support physical or biological 
features essential to the conservation of a listed species and provide 
for the conservation of the species.
    Section 4(b)(8) of the Act requires us to briefly evaluate and 
describe, in any proposed or final regulation that designates critical 
habitat, activities involving a Federal action that may violate 7(a)(2) 
of the Act by destroying or adversely modifying such habitat, or that 
may be affected by such designation.
    Activities that the Service may, during a consultation under 
section 7(a)(2) of the Act, find are likely to destroy or adversely 
modify critical habitat include, but are not limited to:
    (1) Actions that would alter the minimum flow or the existing flow 
regime. Such activities could include, but are not limited to, 
impoundment, channelization, water diversion, water withdrawal, and 
hydropower generation. These activities could eliminate or reduce the 
habitat necessary for the growth and reproduction of the Central Texas 
mussels and its fish host by decreasing or altering flows to levels 
that would adversely affect their ability to complete their life 
cycles.
    (2) Actions that would significantly alter water chemistry or 
temperature. Such activities could include, but are not limited to, 
release of chemicals (including pharmaceuticals, metals, and salts), 
biological pollutants, or heated effluents into the surface water or 
connected groundwater at a point source or by dispersed release (non-
point source). These activities could alter water conditions to levels 
that are beyond the tolerances of the mussel or its host fish and 
result in direct or cumulative adverse effects to these individuals and 
their life cycles.
    (3) Actions that would significantly increase sediment deposition 
within the stream channel. Such activities could include, but are not 
limited to, excessive sedimentation from livestock grazing, road 
construction, channel alteration, timber harvest, off-road vehicle use, 
agricultural, industrial, and urban development, and other watershed 
and floodplain disturbances. These activities could eliminate or reduce 
the habitat necessary for the growth and reproduction of the mussel and 
its fish host by increasing the sediment deposition to levels that 
would adversely affect their ability to complete their life cycles.
    (4) Actions that would significantly alter channel morphology or 
geometry. Such activities could include, but are not limited to, 
channelization, impoundment, road and bridge construction, mining, 
dredging, and destruction of riparian vegetation. These activities may 
lead to changes in water flows and levels that would degrade or 
eliminate the mussel or its fish host and/or their habitats. These 
actions can also lead to increased sedimentation and degradation in 
water quality to levels that are beyond the tolerances of the mussel or 
its fish host.
    (5) Actions that result in the introduction, spread, or 
augmentation of nonnative aquatic species in occupied stream segments, 
or in stream segments that are hydrologically connected to occupied 
stream segments, even if those segments are occasionally intermittent, 
or introduction of other species that compete with or prey on the 
Central Texas mussels. Possible actions could include, but are not 
limited to, stocking of nonnative fishes, stocking of sport fish, or 
other related actions. These activities can introduce parasites or 
disease for host fish, and can result in direct predation, or affect 
the growth, reproduction, and survival, of Central Texas mussels.

Exemptions

Application of Section 4(a)(3) of the Act

    Section 4(a)(3)(B)(i) of the Act (16 U.S.C. 1533(a)(3)(B)(i)) 
provides that the Secretary shall not designate as critical habitat any 
lands or other geographical areas owned or controlled by the Department 
of Defense, or designated for its use, that are subject to an 
integrated natural resources management plan (INRMP) prepared under 
section 101 of the Sikes Act (16 U.S.C. 670a), if the Secretary 
determines in writing that such plan provides a

[[Page 47972]]

benefit to the species for which critical habitat is proposed for 
designation. There are no Department of Defense (DoD) lands with a 
completed INRMP within the proposed critical habitat designation.

Consideration of Impacts Under Section 4(b)(2) of the Act

    Section 4(b)(2) of the Act states that the Secretary shall 
designate and make revisions to critical habitat on the basis of the 
best available scientific data after taking into consideration the 
economic impact, national security impact, and any other relevant 
impact of specifying any particular area as critical habitat. The 
Secretary may exclude an area from critical habitat if she determines 
that the benefits of such exclusion outweigh the benefits of specifying 
such area as part of the critical habitat, unless she determines, based 
on the best scientific data available, that the failure to designate 
such area as critical habitat will result in the extinction of the 
species. In making that determination, the statute on its face, as well 
as the legislative history, are clear that the Secretary has broad 
discretion regarding which factor(s) to use and how much weight to give 
to any factor.
    Under section 4(b)(2) of the Act, we may exclude an area from 
designated critical habitat based on economic impacts, impacts on 
national security, or any other relevant impacts. In considering 
whether to exclude a particular area from the designation, we identify 
the benefits of including the area in the designation, identify the 
benefits of excluding the area from the designation, and evaluate 
whether the benefits of exclusion outweigh the benefits of inclusion. 
If the analysis indicates that the benefits of exclusion outweigh the 
benefits of inclusion, the Secretary may exercise the discretion to 
exclude the area only if such exclusion would not result in the 
extinction of the species. We describe below the process that we 
undertook for taking into consideration each category of impacts and 
our analyses of the relevant impacts.
    The Service is aware of efforts currently under way by the Brazos 
River Authority, Trinity River Authority of Texas, and Lower Colorado 
River Authority (collectively the River Authorities) to develop 
comprehensive management plans for one or more species of Central Texas 
mussels. The Service is currently working with the River Authorities 
individually to develop Candidate Conservation Agreements with 
Assurances (CCAAs) that address activities conducted by the River 
Authorities and conservation measures specifically designed to provide 
a net conservation benefit to the covered species, including the 
Central Texas mussels, in the covered area for the term of the CCAA. 
The Brazos River Authority CCAA would cover the false spike and Texas 
fawnsfoot. The Trinity River Authority of Texas is developing a CCAA 
that would cover the Texas fawnsfoot. The Colorado River Authority is 
developing a CCAA that would cover the Texas fawnsfoot and Texas 
pimpleback. Finally, the Guadalupe-Blanco River Authority, in 
partnership with the Upper Guadalupe River Authority, has plans to 
develop a comprehensive Habitat Conservation Plan (HCP) for the entire 
Guadalupe River Basin that would cover the false spike, Guadalupe orb, 
and Guadalupe fatmucket, among other species. None of these plans have 
been approved or operationalized as of the time this proposal is 
published. While these agreements are not yet completed, if and when 
they are, we may consider excluding areas covered by the completed 
agreements from our critical habitat designations.

Consideration of Economic Impacts

    Section 4(b)(2) of the Act and its implementing regulations require 
that we consider the economic impact that may result from a designation 
of critical habitat. To assess the probable economic impacts of a 
designation, we must first evaluate specific land uses or activities 
and projects that may occur in the area of the critical habitat. We 
then must evaluate whether a specific critical habitat designation may 
restrict or modify specific land uses or activities for the benefit of 
the species and its habitat within the areas proposed. We then identify 
which conservation efforts may be the result of the species being 
listed under the Act versus those attributed solely to the designation 
of critical habitat. The probable economic impact of a proposed 
critical habitat designation is analyzed by comparing scenarios both 
``with critical habitat'' and ``without critical habitat.''
    The ``without critical habitat'' scenario represents the baseline 
for the analysis, which includes the existing regulatory and 
socioeconomic burden imposed on landowners, managers, or other resource 
users potentially affected by the designation of critical habitat 
(e.g., under the Federal listing as well as other Federal, State, and 
local regulations). The baseline, therefore, represents the costs of 
all efforts attributable to the listing of the species under the Act 
(i.e., conservation of the species and its habitat incurred regardless 
of whether critical habitat is designated). The ``with critical 
habitat'' scenario describes the incremental impacts associated 
specifically with the designation of critical habitat for the species. 
The incremental conservation efforts and associated impacts would not 
be expected without the designation of critical habitat for the 
species. In other words, the incremental costs are those attributable 
solely to the designation of critical habitat, above and beyond the 
baseline costs. These are the costs we use when evaluating the benefits 
of inclusion and exclusion of particular areas from the final 
designation of critical habitat should we choose to conduct a 
discretionary 4(b)(2) exclusion analysis.
    For these proposed designations, we developed an incremental 
effects memorandum (IEM) considering the probable incremental economic 
impacts that may result from these proposed designations of critical 
habitat. The information contained in our IEM was then used to develop 
a screening analysis of the probable effects of the designations of 
critical habitat for the Central Texas mussels (Industrial Economics, 
Inc. (IEc) 2019, entire). We began by conducting a screening analysis 
of the proposed designation of critical habitat in order to focus our 
analysis on the key factors that are likely to result in incremental 
economic impacts. The purpose of the screening analysis is to filter 
out particular geographic areas of critical habitat that are already 
subject to such protections and are, therefore, unlikely to incur 
incremental economic impacts. In particular, the screening analysis 
considers baseline costs (i.e., absent critical habitat designation) 
and includes probable incremental economic impacts where land and water 
use may be subject to conservation plans, land management plans, best 
management practices, or regulations that protect the habitat area as a 
result of the Federal listing status of the species. Ultimately, the 
screening analysis allows us to focus our analysis on evaluating the 
specific areas or sectors that may incur probable incremental economic 
impacts as a result of the designation. The screening analysis also 
assesses whether units are unoccupied by the species and thus may 
require additional management or conservation efforts as a result of 
the critical habitat designation for the species; these additional 
efforts may incur incremental economic impacts. This screening 
analysis, combined with the information contained in our IEM, 
constitute our draft economic analysis (DEA) of the proposed critical 
habitat

[[Page 47973]]

designations for the Central Texas mussels, and is summarized in the 
narrative below.
    Executive Orders (E.O.s) 12866 and 13563 direct Federal agencies to 
assess the costs and benefits of available regulatory alternatives in 
quantitative (to the extent feasible) and qualitative terms. Consistent 
with the E.O. regulatory analysis requirements, our effects analysis 
under the Act may take into consideration impacts to both directly and 
indirectly affected entities, where practicable and reasonable. If 
sufficient data are available, we assess to the extent practicable the 
probable impacts to both directly and indirectly affected entities. As 
part of our screening analysis, we considered the types of economic 
activities that are likely to occur within the areas likely affected by 
the proposed critical habitat designations. In our December 4, 2019, 
IEM describing probable incremental economic impacts that may result 
from the proposed designations, we first identified probable 
incremental economic impacts associated with each of the following 
categories of activities: (1) Federal lands management (National Park 
Service, U.S. Forest Service, Department of Defense); (2) agriculture; 
(3) forest management/silviculture/timber; (4) development; (5) 
recreation; (6) restoration activities; and (7) transportation. We 
considered each industry or category individually. Additionally, we 
considered whether the activities have any Federal involvement. 
Critical habitat designation generally will not affect activities that 
do not have any Federal involvement; under the Act, designation of 
critical habitat only affects activities conducted, funded, permitted, 
or authorized by Federal agencies. If we list any of the species, as 
proposed in this document, in areas where the Central Texas mussels are 
present, under section 7 of the Act, Federal agencies would be required 
to consult with the Service on activities they fund, permit, or 
implement that may affect the species. If we finalize this proposed 
critical habitat designation, consultations to avoid the destruction or 
adverse modification of critical habitat would be incorporated into the 
existing consultation process.
    In our IEM, we attempted to clarify the distinction between the 
effects that would result from the species being listed and those 
attributable to the critical habitat designations (i.e., difference 
between the jeopardy and adverse modification standards) for the 
Central Texas mussels. Because the designation of critical habitat is 
being proposed concurrently with the listing, it has been our 
experience that it is more difficult to discern which conservation 
efforts are attributable to the species being listed and those which 
would result solely from the designation of critical habitat. However, 
the following specific circumstances in this case help to inform our 
evaluation: (1) The essential physical or biological features 
identified for critical habitat are the same features essential for the 
life requisites of the species, and (2) any actions that would result 
in sufficient harm or harassment to constitute jeopardy to the Central 
Texas mussels would also likely adversely affect the essential physical 
or biological features of critical habitat. The IEM outlines our 
rationale concerning this limited distinction between baseline 
conservation efforts and incremental impacts of the designations of 
critical habitat for these species. This evaluation of the incremental 
effects has been used as the basis to evaluate the probable incremental 
economic impacts of these proposed designations of critical habitat.
    The proposed critical habitat designations for the Central Texas 
mussels totals approximately 1,944 river mi (3,129 river km) in 27 
units with a combination of occupied and unoccupied areas. In occupied 
areas, any actions that may affect the species or their habitat would 
likely also affect proposed critical habitat, and it is unlikely that 
any additional conservation efforts would be required to address the 
adverse modification standard over and above those recommended as 
necessary to avoid jeopardizing the continued existence of the species. 
Therefore, the only additional costs that are expected in the occupied 
proposed critical habitat designations are administrative costs, due to 
the fact that this additional analysis will require time and resources 
by both the Federal action agency and the Service. However, it is 
believed that, in most circumstances, these costs would not reach the 
threshold of ``significant'' under E.O. 12866. We anticipate 
incremental costs of section 7 consultations in occupied critical 
habitat to total less than $75,000 per year.
    In unoccupied critical habitat, any costs of section 7 
consultations would not be incurred due to the listing of the species. 
We are proposing to designate six subunits that are currently 
unoccupied by the Central Texas mussels. We anticipate approximately 
five new formal section 7 consultations to occur in the next 10 years 
in these subunits. Considering the costs of formal consultation as well 
as project modifications that arise from consultation, we project 
consultations in unoccupied critical habitat to cost approximately 
$15,000 per consultation.
    In total, in both occupied and unoccupied critical habitat, we 
expect the total cost of critical habitat designations not to exceed 
$82,500 per year.
    We are soliciting data and comments from the public on the DEA 
discussed above, as well as on all aspects of this proposed rule and 
our required determinations. During the development of a final 
designation, we will consider the information presented in the DEA and 
any additional information on economic impacts received during the 
public comment period to determine whether any specific areas should be 
excluded from the final critical habitat designation under authority of 
section 4(b)(2) and our implementing regulations at 50 CFR 17.90. If we 
receive credible information regarding the existence of a meaningful 
economic or other relevant impact supporting a benefit of exclusion, we 
will conduct an exclusion analysis for the relevant area or areas. We 
may also exercise the discretion to evaluate any other particular areas 
for possible exclusion. Furthermore, when we conduct an exclusion 
analysis based on impacts identified by experts in, or sources with 
firsthand knowledge about, impacts that are outside the scope of the 
Service's expertise, we will give weight to those impacts consistent 
with the expert or firsthand information unless we have rebutting 
information. We may exclude an area from critical habitat if we 
determine that the benefits of excluding the area outweigh the benefits 
of including the area, provided the exclusion will not result in the 
extinction of this species.

Exclusions

Exclusions Based on Economic Impacts

    The first sentence of section 4(b)(2) of the Act requires the 
Service to consider the economic impacts (as well as the impacts on 
national security and any other relevant impacts) of designating 
critical habitat. In addition, economic impacts may, for some 
particular areas, play an important role in the discretionary section 
4(b)(2) exclusion analysis under the second sentence of section 
4(b)(2). In both contexts, the Service will consider the probable 
incremental economic impacts of the designation. When the Service 
undertakes a discretionary section 4(b)(2) exclusion analysis with 
respect to a particular area, we will weigh the economic benefits of 
exclusion (and any

[[Page 47974]]

other benefits of exclusion) against any benefits of inclusion 
(primarily the conservation value of designating the area). The 
conservation value may be influenced by the level of effort needed to 
manage degraded habitat to the point where it could support the listed 
species.
    The Service will use its discretion in determining how to weigh 
probable incremental economic impacts against conservation value. The 
nature of the probable incremental economic impacts and not necessarily 
a particular threshold level triggers considerations of exclusions 
based on probable incremental economic impacts. For example, if an 
economic analysis indicates high probable incremental impacts of 
designating a particular critical habitat unit of low conservation 
value (relative to the remainder of the designation), the Service may 
consider exclusion of that particular unit.

Exclusions Based on National Security Impacts or Homeland Security 
Impacts

    Under section 4(b)(2) of the Act, we consider whether there are 
lands where a national security impact might exist. In preparing this 
proposal, we have determined that there are no lands within the 
proposed designations of critical habitat for the Central Texas mussels 
owned or managed by the Department of Defense or Department of Homeland 
Security. We anticipate no impact on national security because there 
are no lands owned or managed by the Department of Defense within this 
proposal, and we have not identified any national security or homeland 
security activities that would be affected by the proposed 
designations. However, if through the public comment period we receive 
credible information regarding impacts on national security or homeland 
security from designating particular areas as critical habitat, then as 
part of developing the final designation of critical habitat, we will 
conduct a discretionary exclusion analysis to determine whether to 
exclude those areas under authority of section 4(b)(2) and our 
implementing regulations at 50 CFR 17.90.

Exclusions Based on Other Relevant Impacts

    Under section 4(b)(2) of the Act, we consider any other relevant 
impacts, in addition to economic impacts and impacts on national 
security. We consider a number of factors including whether there are 
permitted conservation plans covering the species in the area such as 
HCPs, safe harbor agreements, or candidate conservation agreements with 
assurances (CCAAs), or whether there are non-permitted conservation 
agreements and partnerships that would be encouraged by designation of, 
or exclusion from, critical habitat. In addition, we look whether there 
are Tribal conservation plans or parnerships, Tribal resources, or 
government-to-government relationships of the United States with Tribal 
entities that may be affected by the designation. We also consider any 
State, local, public health, community interest, environmental, or 
social impacts that might occur because of the designations.
    In preparing this proposal, we have determined that there are 
currently no HCPs or other management plans for the Central Texas 
mussels, and the proposed designations do not include any tribal lands 
or trust resources. We anticipate no impact on tribal lands, 
partnerships, or HCPs from these proposed critical habitat 
designations. We are aware of efforts currently under way by the River 
Authorities to develop CCAAs for the Central Texas mussels, as 
discussed above, and will take those efforts into account in a final 
designation. During the development of a final designation, we will 
consider any additional information received through the public comment 
period regarding other relevant impacts to determine whether any 
specific areas should be excluded from the final critical habitat 
designation under authority of section 4(b)(2) and our implementing 
regulations at 50 CFR 17.90.

Required Determinations

Clarity of the Rule

    We are required by Executive Orders 12866 and 12988 and by the 
Presidential Memorandum of June 1, 1998, to write all rules in plain 
language. This means that each rule we publish must:
    (1) Be logically organized;
    (2) Use the active voice to address readers directly;
    (3) Use clear language rather than jargon;
    (4) Be divided into short sections and sentences; and
    (5) Use lists and tables wherever possible.
    If you feel that we have not met these requirements, send us 
comments by one of the methods listed in ADDRESSES. To better help us 
revise the rule, your comments should be as specific as possible. For 
example, you should tell us the numbers of the sections or paragraphs 
that are unclearly written, which sections or sentences are too long, 
the sections where you feel lists or tables would be useful, etc.

Regulatory Planning and Review (Executive Orders 12866 and 13563)

    Executive Order 12866 provides that the Office of Information and 
Regulatory Affairs (OIRA) in the Office of Management and Budget will 
review all significant rules. OIRA has determined that this rule is not 
significant.
    Executive Order 13563 reaffirms the principles of E.O. 12866 while 
calling for improvements in the Nation's regulatory system to promote 
predictability, to reduce uncertainty, and to use the best, most 
innovative, and least burdensome tools for achieving regulatory ends. 
The Executive order directs agencies to consider regulatory approaches 
that reduce burdens and maintain flexibility and freedom of choice for 
the public where these approaches are relevant, feasible, and 
consistent with regulatory objectives. E.O. 13563 emphasizes further 
that regulations must be based on the best available science and that 
the rulemaking process must allow for public participation and an open 
exchange of ideas. We have developed this rule in a manner consistent 
with these requirements.

Regulatory Flexibility Act (5 U.S.C. 601 et seq.)

    Under the Regulatory Flexibility Act (RFA; 5 U.S.C. 601 et seq.), 
as amended by the Small Business Regulatory Enforcement Fairness Act of 
1996 (SBREFA; 5 U.S.C. 801 et seq.), whenever an agency is required to 
publish a notice of rulemaking for any proposed or final rule, it must 
prepare and make available for public comment a regulatory flexibility 
analysis that describes the effects of the rule on small entities 
(i.e., small businesses, small organizations, and small government 
jurisdictions). However, no regulatory flexibility analysis is required 
if the head of the agency certifies the rule will not have a 
significant economic impact on a substantial number of small entities. 
The SBREFA amended the RFA to require Federal agencies to provide a 
certification statement of the factual basis for certifying that the 
rule will not have a significant economic impact on a substantial 
number of small entities.
    According to the Small Business Administration, small entities 
include small organizations such as independent nonprofit 
organizations; small governmental jurisdictions, including school 
boards and city and town governments that serve fewer than 50,000 
residents; and small businesses (13 CFR 121.201). Small businesses 
include manufacturing and mining concerns with fewer than 500

[[Page 47975]]

employees, wholesale trade entities with fewer than 100 employees, 
retail and service businesses with less than $5 million in annual 
sales, general and heavy construction businesses with less than $27.5 
million in annual business, special trade contractors doing less than 
$11.5 million in annual business, and agricultural businesses with 
annual sales less than $750,000. To determine if potential economic 
impacts to these small entities are significant, we considered the 
types of activities that might trigger regulatory impacts under this 
designation as well as types of project modifications that may result. 
In general, the term ``significant economic impact'' is meant to apply 
to a typical small business firm's business operations.
    Under the RFA, as amended, and as understood in the light of recent 
court decisions, Federal agencies are required to evaluate the 
potential incremental impacts of rulemaking only on those entities 
directly regulated by the rulemaking itself and, therefore, are not 
required to evaluate the potential impacts to indirectly regulated 
entities. The regulatory mechanism through which critical habitat 
protections are realized is section 7 of the Act, which requires 
Federal agencies, in consultation with the Service, to ensure that any 
action authorized, funded, or carried out by the agency is not likely 
to destroy or adversely modify critical habitat. Therefore, under 
section 7, only Federal action agencies are directly subject to the 
specific regulatory requirement (avoiding destruction and adverse 
modification) imposed by critical habitat designation. Consequently, it 
is our position that only Federal action agencies would be directly 
regulated if we adopt the proposed critical habitat designations. There 
is no requirement under the RFA to evaluate the potential impacts to 
entities not directly regulated. Moreover, Federal agencies are not 
small entities. Therefore, because no small entities would be directly 
regulated by this rulemaking, the Service certifies that, if 
promulgated, the proposed critical habitat designations will not have a 
significant economic impact on a substantial number of small entities.
    In summary, we have considered whether the proposed designations 
would result in a significant economic impact on a substantial number 
of small entities. For the above reasons and based on currently 
available information, we certify that, if made final, the proposed 
critical habitat designations will not have a significant economic 
impact on a substantial number of small business entities. Therefore, 
an initial regulatory flexibility analysis is not required.

Energy Supply, Distribution, or Use--Executive Order 13211

    Executive Order 13211 (Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use) requires 
agencies to prepare Statements of Energy Effects when undertaking 
certain actions. In our economic analysis, we did not find that the 
designations of this proposed critical habitat will significantly 
affect energy supplies, distribution, or use. Therefore, this action is 
not a significant energy action, and no Statement of Energy Effects is 
required.

Unfunded Mandates Reform Act (2 U.S.C. 1501 et seq.)

    In accordance with the Unfunded Mandates Reform Act (2 U.S.C. 1501 
et seq.), we make the following findings:
    (1) This proposed rule would not produce a Federal mandate. In 
general, a Federal mandate is a provision in legislation, statute, or 
regulation that would impose an enforceable duty upon State, local, or 
tribal governments, or the private sector, and includes both ``Federal 
intergovernmental mandates'' and ``Federal private sector mandates.'' 
These terms are defined in 2 U.S.C. 658(5)-(7). ``Federal 
intergovernmental mandate'' includes a regulation that ``would impose 
an enforceable duty upon State, local, or tribal governments'' with two 
exceptions. It excludes ``a condition of Federal assistance.'' It also 
excludes ``a duty arising from participation in a voluntary Federal 
program,'' unless the regulation ``relates to a then-existing Federal 
program under which $500,000,000 or more is provided annually to State, 
local, and tribal governments under entitlement authority,'' if the 
provision would ``increase the stringency of conditions of assistance'' 
or ``place caps upon, or otherwise decrease, the Federal Government's 
responsibility to provide funding,'' and the State, local, or tribal 
governments ``lack authority'' to adjust accordingly. At the time of 
enactment, these entitlement programs were: Medicaid; Aid to Families 
with Dependent Children work programs; Child Nutrition; Food Stamps; 
Social Services Block Grants; Vocational Rehabilitation State Grants; 
Foster Care, Adoption Assistance, and Independent Living; Family 
Support Welfare Services; and Child Support Enforcement. ``Federal 
private sector mandate'' includes a regulation that ``would impose an 
enforceable duty upon the private sector, except (i) a condition of 
Federal assistance or (ii) a duty arising from participation in a 
voluntary Federal program.''
    The designations of critical habitat do not impose a legally 
binding duty on non-Federal Government entities or private parties. 
Under the Act, the only regulatory effect is that Federal agencies must 
ensure that their actions do not destroy or adversely modify critical 
habitat under section 7. While non-Federal entities that receive 
Federal funding, assistance, or permits, or that otherwise require 
approval or authorization from a Federal agency for an action, may be 
indirectly impacted by the designation of critical habitat, the legally 
binding duty to avoid destruction or adverse modification of critical 
habitat rests squarely on the Federal agency. Furthermore, to the 
extent that non-Federal entities are indirectly impacted because they 
receive Federal assistance or participate in a voluntary Federal aid 
program, the Unfunded Mandates Reform Act would not apply, nor would 
critical habitat shift the costs of the large entitlement programs 
listed above onto State governments.
    (2) We do not believe that this proposed rule would significantly 
or uniquely affect small governments because the lands being proposed 
for critical habitat designation are owned by the State of Texas. This 
government entity does not fit the definition of ``small governmental 
jurisdiction.'' Therefore, a Small Government Agency Plan is not 
required.

Takings--Executive Order 12630

    In accordance with E.O. 12630 (Government Actions and Interference 
with Constitutionally Protected Private Property Rights), we have 
analyzed the potential takings implications of designating critical 
habitat for the Central Texas mussels in a takings implications 
assessment. The Act does not authorize the Service to regulate private 
actions on private lands or confiscate private property as a result of 
critical habitat designation. Designation of critical habitat does not 
affect land ownership, or establish any closures or restrictions on use 
of or access to the designated areas. Furthermore, the designation of 
critical habitat does not affect landowner actions that do not require 
Federal funding or permits, nor does it preclude development of habitat 
conservation programs or issuance of incidental take permits to permit 
actions that do require Federal funding or permits to go forward. 
However, Federal agencies are prohibited from carrying out, funding, or 
authorizing actions that would destroy or adversely modify

[[Page 47976]]

critical habitat. A takings implications assessment has been completed 
and concludes that, if adopted, these designations of critical habitat 
for the Central Texas mussels does not pose significant takings 
implications for lands within or affected by the designations.

Federalism--Executive Order 13132

    In accordance with E.O. 13132 (Federalism), this proposed rule does 
not have significant federalism effects. A federalism summary impact 
statement is not required. In keeping with Department of the Interior 
and Department of Commerce policy, we requested information from, and 
coordinated development of these proposed critical habitat designations 
with, appropriate State resource agencies in Texas. From a federalism 
perspective, the designation of critical habitat directly affects only 
the responsibilities of Federal agencies. The Act imposes no other 
duties with respect to critical habitat, either for States and local 
governments, or for anyone else. As a result, the proposed rule does 
not have substantial direct effects either on the States, or on the 
relationship between the National Government and the States, or on the 
distribution of powers and responsibilities among the various levels of 
government. The proposed designations may have some benefit to these 
governments because the areas that contain the features essential to 
the conservation of the species are more clearly defined, and the 
physical or biological features of the habitat necessary to the 
conservation of the species are specifically identified. This 
information does not alter where and what federally sponsored 
activities may occur. However, it may assist these local governments in 
long-range planning (because these local governments no longer have to 
wait for case-by-case section 7 consultations to occur).
    Where State and local governments require approval or authorization 
from a Federal agency for actions that may affect critical habitat, 
consultation under section 7(a)(2) would be required. While non-Federal 
entities that receive Federal funding, assistance, or permits, or that 
otherwise require approval or authorization from a Federal agency for 
an action, may be indirectly impacted by the designation of critical 
habitat, the legally binding duty to avoid destruction or adverse 
modification of critical habitat rests squarely on the Federal agency.

Civil Justice Reform--Executive Order 12988

    In accordance with Executive Order 12988 (Civil Justice Reform), 
the Office of the Solicitor has determined that the rule does not 
unduly burden the judicial system and that it meets the requirements of 
sections 3(a) and 3(b)(2) of the Order. We have proposed designating 
critical habitat in accordance with the provisions of the Act. To 
assist the public in understanding the habitat needs of the species, 
this proposed rule identifies the elements of physical or biological 
features essential to the conservation of the species. The proposed 
areas of designated critical habitat are presented on maps, and the 
proposed rule provides several options for the interested public to 
obtain more detailed location information, if desired.

Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.)

    This rule does not contain information collection requirements, and 
a submission to the Office of Management and Budget (OMB) under the 
Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.) is not 
required. We may not conduct or sponsor and you are not required to 
respond to a collection of information unless it displays a currently 
valid OMB control number.

National Environmental Policy Act (42 U.S.C. 4321 et seq.)

    It is our position that, outside the jurisdiction of the U.S. Court 
of Appeals for the Tenth Circuit, we do not need to prepare 
environmental analyses pursuant to the National Environmental Policy 
Act (NEPA; 42 U.S.C. 4321 et seq.) in connection with designating 
critical habitat under the Act. We published a notice outlining our 
reasons for this determination in the Federal Register on October 25, 
1983 (48 FR 49244). This position was upheld by the U.S. Court of 
Appeals for the Ninth Circuit (Douglas County v. Babbitt, 48 F.3d 1495 
(9th Cir. 1995), cert. denied 516 U.S. 1042 (1996)).

Government-to-Government Relationship With Tribes

    In accordance with the President's memorandum of April 29, 1994 
(Government-to-Government Relations with Native American Tribal 
Governments; 59 FR 22951), Executive Order 13175 (Consultation and 
Coordination with Indian Tribal Governments), and the Department of the 
Interior's manual at 512 DM 2, we readily acknowledge our 
responsibility to communicate meaningfully with recognized Federal 
Tribes on a government-to-government basis. In accordance with 
Secretarial Order 3206 of June 5, 1997 (American Indian Tribal Rights, 
Federal-Tribal Trust Responsibilities, and the Endangered Species Act), 
we readily acknowledge our responsibilities to work directly with 
tribes in developing programs for healthy ecosystems, to acknowledge 
that tribal lands are not subject to the same controls as Federal 
public lands, to remain sensitive to Indian culture, and to make 
information available to tribes. We have determined that no tribal 
lands fall within the boundaries of the proposed critical habitat 
designations for the Central Texas mussels, so no tribal lands would be 
affected by the proposed designations.

References Cited

    A complete list of references cited in this rulemaking is available 
on the internet at http://www.regulations.gov and upon request from the 
Austin Ecological Services Field Office (see FOR FURTHER INFORMATION 
CONTACT).

Authors

    The primary authors of this proposed rule are the staff members of 
the U.S. Fish and Wildlife Service's Species Assessment Team and the 
Austin Ecological Services Field Office.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Proposed Regulation Promulgation

    Accordingly, we propose to amend part 17, subchapter B of chapter 
I, title 50 of the Code of Federal Regulations, as set forth below:

PART 17--ENDANGERED AND THREATENED WILDLIFE AND PLANTS

0
1. The authority citation for part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 1531-1544; and 4201-4245, unless 
otherwise noted.

0
2. Amend Sec.  17.11(h) by adding entries for ``Fatmucket, Guadalupe''; 
``Fatmucket, Texas''; ``Fawnsfoot, Texas''; ``Orb, Guadalupe''; 
``Pimpleback, Texas''; and ``Spike, false'' to the List of Endangered 
and Threatened Wildlife in alphabetical order under Clams to read as 
follows:


Sec.  17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

[[Page 47977]]



----------------------------------------------------------------------------------------------------------------
                                                                                          Listing citations and
           Common name              Scientific name       Where listed        Status         applicable rules
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
              Clams
 
                                                  * * * * * * *
Fatmucket, Guadalupe............  Lampsilis bergmanni  Wherever found....            E   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f)CH.
Fatmucket, Texas................  Lampsilis bracteata  Wherever found....            E   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f)CH.
Fawnsfoot, Texas................  Truncilla macrodon.  Wherever found....            T   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.45(c)4d; 50 CFR
                                                                                          17.95(f)CH.
 
                                                  * * * * * * *
Orb, Guadalupe..................  Cyclonaias necki...  Wherever found....            E   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f)CH.
 
                                                  * * * * * * *
Pimpleback, Texas...............  Cyclonaias petrina.  Wherever found....            E   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f)CH.
 
                                                  * * * * * * *
Spike, false....................  Fusconaia mitchelli  Wherever found....            E   [Federal Register
                                                                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f)CH.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

0
3. As proposed to be added at 83 FR 51570 (Oct. 11, 2018), and amended 
at 85 FR 44821 (July 24, 2020) and 85 FR 61384 (Sept. 29, 2020), Sec.  
17.45 is further amended by adding paragraph (c) to read as follows:


Sec.  17.45   Special rules--snails and clams.

* * * * *
    (c) Texas fawnsfoot (Truncilla macrodon)--(1) Prohibitions. The 
following prohibitions that apply to endangered wildlife also apply to 
the Texas fawnsfoot. Except as provided at paragraph (c)(2) of this 
section and Sec. Sec.  17.4 and 17.5, it is unlawful for any person 
subject to the jurisdiction of the United States to commit, to attempt 
to commit, to solicit another to commit, or cause to be committed, any 
of the following acts in regard to the Texas fawnsfoot:
    (i) Import or export, as set forth at Sec.  17.21(b).
    (ii) Take, as set forth at Sec.  17.21(c)(1).
    (iii) Possession and other acts with unlawfully taken specimens, as 
set forth at Sec.  17.21(d)(1).
    (iv) Interstate or foreign commerce in the course of commercial 
activity, as set forth at Sec.  17.21(e).
    (v) Sale or offer for sale, as set forth at Sec.  17.21(f).
    (2) Exceptions from the prohibitions. With regard to this species, 
you may:
    (i) Conduct activities as authorized by a permit under Sec.  17.32.
    (ii) Take, as set forth at Sec.  17.21(c)(2) through (4) for 
endangered wildlife.
    (iii) Take, as set forth at Sec.  17.31(b).
    (iv) Possess and engage in other acts with unlawfully taken Texas 
fawnsfoot, as set forth at Sec.  17.21(d)(2).
    (v) Take incidental to an otherwise lawful activity caused by:
    (A) Channel restoration projects that create natural, physically 
stable, ecologically functioning streams (or stream and wetland 
systems) that are reconnected with their groundwater aquifers.
    (B) Bioengineering methods such as streambank stabilization using 
live stakes (live, vegetative cuttings inserted or tamped into the 
ground in a manner that allows the stake to take root and grow), live 
fascines (live branch cuttings, usually willows, bound together into 
long, cigar-shaped bundles), or brush layering (cuttings or branches of 
easily rooted tree species layered between successive lifts of soil 
fill). These methods would not include the sole use of quarried rock 
(rip-rap) or the use of rock baskets or gabion structures. In addition, 
to reduce streambank erosion and sedimentation into the stream, work 
using these bioengineering methods would be performed at base-flow or 
low-water conditions and when significant rainfall is not predicted. 
Further, streambank stabilization projects must keep all equipment out 
of the stream channels and water.
    (C) Soil and water conservation practices and riparian and adjacent 
upland habitat management activities that restore in-stream habitats 
for the species, restore adjacent riparian habitats that enhance stream 
habitats for the species, stabilize degraded and eroding stream banks 
to limit sedimentation and scour of the species' habitats, and restore 
or enhance nearby upland habitats to limit sedimentation of the 
species' habitats and comply with conservation practice standards and 
specifications, and technical guidelines developed by the Natural 
Resources Conservation Service.
    (D) Presence or abundance surveys for Texas fawnfoot conducted by 
individuals who successfully complete and show proficiency by passing 
the end-of-course test with a score equal to or greater than 90 
percent, with 100 percent accuracy in identification of mussel species 
listed under the Endangered Species Act, in an approved freshwater 
mussel identification and sampling course (specific to the species and 
basins in which the Texas fawnsfoot is known to occur), such as that 
administered by the Service, a State wildlife agency, or qualified 
university experts. Those individuals exercising the exemption in this 
paragraph (c)(2)(v)(D) should provide reports to the Service annually 
on number, location, and date of collection. The exemption in this 
paragraph (c)(2)(v)(D) does not apply if lethal take or collection is 
anticipated. The exemption in this paragraph (c)(2)(v)(D) only applies 
for 5 years from the date of successful course completion.
* * * * *
0
4. Amend Sec.  17.95(f) by:
0
a. Adding critical habitat entries for ``Guadalupe Fatmucket (Lampsilis

[[Page 47978]]

bergmanni)'', ``Texas Fatmucket (Lampsilis bracteata)'', and ``Texas 
Fawnsfoot (Truncilla macrodon)'' immediately following the entry for 
``Appalachian Elktoe (Alasmidonta raveneliana)'';
0
b. Adding an entry for ``Guadalupe Orb (Cyclonaias necki)'' immediately 
following the entry for ``Carolina Heelsplitter (Lasmigona decorata)''; 
and
0
c. Adding entries for ``Texas Pimpleback (Cyclonaias petrina)'' and 
``False Spike (Fusconaia mitchelli)'' immediately following the entry 
for ``Georgia Pigtoe (Pleurobema hanleyianum)''.
    The additions read as follows:


Sec.  17.95   Critical habitat--fish and wildlife.

* * * * *
    (f) * * *
Guadalupe Fatmucket (Lampsilis bergmanni)
    (1) A critical habitat unit is depicted for Kendall and Kerr 
Counties, Texas, on the map in this critical habitat entry.
    (2) Within this area, the physical or biological features essential 
to the conservation of Guadalupe fatmucket consist of the following 
components within waters and streambeds up to the ordinary high-water 
mark:
    (i) Flowing water at moderate to high rates with sufficient depth 
to remain sufficiently cool and oxygenated during low-flow periods;
    (ii) Substrate including bedrock and boulder crevices, point bars, 
and vegetated run habitat comprising sand, gravel, and larger cobbles;
    (iii) Green sunfish (Lepomis cyanellus), bluegill (L. macrochirus), 
largemouth bass (Micropterus salmoides), and Guadalupe bass (M. 
treculii) present; and
    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Index map of critical habitat for the Central Texas mussels, 
which includes the Guadalupe fatmucket, follows:
BILLING CODE 4333-15-P

[[Page 47979]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.031


[[Page 47980]]


[GRAPHIC] [TIFF OMITTED] TP26AU21.032

Texas Fatmucket (Lampsilis bracteata)
    (1) Critical habitat units are depicted for Blanco, Gillespie, 
Hays, Kimble, Llano, Mason, McCulloch, Menard, Runnels, San Saba, and 
Travis Counties, Texas, on the maps in this critical habitat entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of Texas fatmucket consist of the 
following components within waters and streambeds up to the ordinary 
high-water mark:
    (i) Flowing water at moderate to high rates with sufficient depth 
to remain sufficiently cool and oxygenated during low-flow periods;
    (ii) Substrate including bedrock and boulder crevices, point bars, 
and vegetated run habitat comprising sand, gravel, and larger cobbles;
    (iii) Green sunfish (Lepomis cyanellus), bluegill (L. macrochirus),

[[Page 47981]]

largemouth bass (Micropterus salmoides), and Guadalupe bass (M. 
treculii) present; and
    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Note: An index map of the critical habitat designations for the 
Central Texas mussels, which includes the Texas fatmucket, can be found 
in this paragraph (f) at the entry for the Guadalupe fatmucket. An 
index map of critical habitat units for the Texas fatmucket follows:
[GRAPHIC] [TIFF OMITTED] TP26AU21.033


[[Page 47982]]


    (6) Map of TXFM-1: Elm Creek follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.034
    

[[Page 47983]]


    (7) Map of Unit TXFM-2: San Saba River, Unit TXFM-3: Cherokee 
Creek, Unit TXFM-4: Llano River, and Unit TXFM-5: Pedernales River, 
follows:
[GRAPHIC] [TIFF OMITTED] TP26AU21.035


[[Page 47984]]


    (8) Map of Unit TXFM-6: Onion Creek follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.036
    
Texas Fawnsfoot (Truncilla macrodon)
    (1) Critical habitat units are depicted for Anderson, Austin, 
Brazos, Burleson, Colorado, Falls, Fort Bend, Freestone, Grimes, 
Henderson, Houston, Kaufman, Lampasas, Leon, Madison, Matagorda, 
McLennan, Milam, Mills, Navarro, Palo Pinto, Parker, Robertson, San 
Saba, Shackelford, Stephens, Throckmorton, Waller, Washington, and 
Wharton Counties, Texas, on the maps in this critical habitat entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of Texas fawnsfoot consist of the 
following components within waters and streambeds up to the ordinary 
high-water mark:
    (i) Flowing water at rates suitable to prevent excess sedimentation 
but not so high as to dislodge individuals or sediment;

[[Page 47985]]

    (ii) Stable bank and riffle habitats with gravel, sand, silt, and 
mud substrates that are clean swept by flushing flows;
    (iii) Freshwater drum (Aplodinotus grunniens) present; and
    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Note: An index map of the critical habitat designations for the 
Central Texas mussels, which includes the Texas fawnsfoot, can be found 
in this paragraph (f) at the entry for the Guadalupe fatmucket. An 
index map of critical habitat units for the Texas fawnsfoot follows:

[[Page 47986]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.037


[[Page 47987]]


    (6) Map of Unit TXFF-1: Clear Fork Brazos River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.038
    

[[Page 47988]]


    (7) Map of Unit TXFF-2: Upper Brazos River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.039
    

[[Page 47989]]


    (8) Map of Unit TXFF-3: Lower Brazos River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.040
    

[[Page 47990]]


    (9) Map of Unit TXFF-4: Little River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.041
    

[[Page 47991]]


    (10) Map of TXFF-5: Lower San Saba and Upper Colorado River 
follows:
[GRAPHIC] [TIFF OMITTED] TP26AU21.042


[[Page 47992]]


    (11) Map of Unit TXFF-6: Lower Colorado River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.043
    

[[Page 47993]]


    (12) Map of Unit TXFF-7: East Fork Trinity River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.044
    

[[Page 47994]]


    (13) Map of Unit TXFF-8: Trinity River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.045
    
* * * * *
Guadalupe Orb (Cyclonaias necki)
    (1) Critical habitat units are depicted for Caldwell, Comal, 
DeWitt, Gonzales, Guadalupe, Kendall, Kerr, and Victoria Counties, 
Texas, on the maps in this critical habitat entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of Guadalupe orb consist of the following 
components within waters and streambeds up to the ordinary high-water 
mark:
    (i) Flowing water at rates suitable to keep riffle habitats wetted 
and well-oxygenated and to prevent excess sedimentation or scour during 
high-flow events but not so high as to dislodge individuals;
    (ii) Stable riffles and runs with substrate composed of cobble, 
gravel, and fine sediments;

[[Page 47995]]

    (iii) Channel catfish (Ictalurus punctatus), flathead catfish 
(Pylodictus olivaris), and tadpole madtom (Noturus gyrinus) present; 
and
    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Note: An index map of the critical habitat designations for the 
Central Texas mussels, which includes the Guadalupe orb, can be found 
in this paragraph (f) at the entry for the Guadalupe fatmucket. An 
index map of critical habitat units for the Guadalupe orb follows:

[[Page 47996]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.046


[[Page 47997]]


    (6) Map of Unit GORB-1: Upper Guadalupe River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.047
    

[[Page 47998]]


    (7) Map of Unit GORB-2: Lower Guadalupe River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.048
    
* * * * *
Texas Pimpleback (Cyclonaias petrina)
    (1) Critical habitat units are depicted for Brown, Coleman, 
Colorado, Concho, Kimble, Lampasas, Mason, McCulloch, Menard, Mills, 
San Saba, Tom Green, and Wharton Counties, Texas, on the maps in this 
critical habitat entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of Texas pimpleback consist of the 
following components within waters and streambeds up to the ordinary 
high-water mark:
    (i) Flowing water at rates suitable to keep riffle habitats wetted 
and well-oxygenated and to prevent excess sedimentation or scour during 
high-flow events but not so high as to dislodge individuals;

[[Page 47999]]

    (ii) Stable riffles and runs with substrate composed of cobble, 
gravel, and fine sediments;
    (iii) Channel catfish (Ictalurus punctatus), flathead catfish 
(Pylodictus olivaris), and tadpole madtom (Noturus gyrinus) present; 
and
    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Note: An index map of the critical habitat designations for the 
Central Texas mussels, which includes the Texas pimpleback, can be 
found in this paragraph (f) at the entry for the Guadalupe fatmucket. 
An index map of critical habitat units for the Texas pimpleback 
follows:

[[Page 48000]]

[GRAPHIC] [TIFF OMITTED] TP26AU21.049


[[Page 48001]]


    (6) Map of Unit TXPB-1: Elm Creek follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.050
    

[[Page 48002]]


    (7) Map of Unit TXPB-2: Concho River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.051
    

[[Page 48003]]


    (8) Map of Unit TXPB-3: Upper Colorado River and Lower San Saba 
River follows:
[GRAPHIC] [TIFF OMITTED] TP26AU21.052


[[Page 48004]]


    (9) Map of Unit TXPB-4: Upper San Saba River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.053
    

[[Page 48005]]


    (10) Map of Unit TXPB-5: Llano River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.054
    

[[Page 48006]]


    (11) Map of Unit TXPB-6: Lower Colorado River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.055
    
False Spike (Fusconaia mitchelli)
    (1) Critical habitat units are depicted for DeWitt, Gonzales, 
Kimble, Mason, Milam, San Saba, Victoria, and Williamson Counties, 
Texas, on the maps in this critical habitat entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of false spike consist of the following 
components within waters and streambeds up to the ordinary high-water 
mark:
    (i) Flowing water at rates suitable to keep riffle habitats wetted 
and well oxygenated, and to prevent excess sedimentation but not so 
high as to dislodge individuals;
    (ii) Stable riffles and runs with cobble, gravel, and fine 
sediments;
    (iii) Blacktail shiner (Cyprinella venusta) and red shiner 
(Cyprinella lutrensis) present; and

[[Page 48007]]

    (iv) Water quality parameters within the following ranges:
    (A) Dissolved oxygen >2 mg/L;
    (B) Salinity <2 ppt;
    (C) Total ammonia <0.77 mg/L total ammonia nitrogen;
    (D) Water temperature <29 [deg]C (84.2 [deg]F); and
    (E) Low levels of contaminants.
    (3) Critical habitat does not include manmade structures (such as 
buildings, aqueducts, runways, roads, and other paved areas) and the 
land on which they are located existing within the legal boundaries on 
[EFFECTIVE DATE OF THE FINAL RULE].
    (4) The maps in this entry, as modified by any accompanying 
regulatory text, establish the boundaries of the critical habitat 
designation. The coordinates or plot points or both on which each map 
is based are available to the public at http://www.regulations.gov 
under Docket No. FWS-R2-ES-2019-0061.
    (5) Note: An index map of the critical habitat designations for the 
Central Texas mussels, which includes the false spike, can be found in 
this paragraph (f) at the entry for the Guadalupe fatmucket. An index 
map of critical habitat units for the false spike follows:
[GRAPHIC] [TIFF OMITTED] TP26AU21.056


[[Page 48008]]


    (6) Map of Unit FASP-1: Little River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.057
    

[[Page 48009]]


    (7) Map of Unit FASP-2: San Saba River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.058
    

[[Page 48010]]


    (8) Map of Unit FASP-3: Llano River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.059
    

[[Page 48011]]


    (9) Map of Unit FASP-4: Guadalupe River follows:
    [GRAPHIC] [TIFF OMITTED] TP26AU21.060
    
* * * * *

Martha Williams,
Principal Deputy Director, Exercising the Delegated Authority of the 
Director U.S. Fish and Wildlife Service.
[FR Doc. 2021-18012 Filed 8-25-21; 8:45 am]
BILLING CODE 4333-15-C