[Federal Register Volume 88, Number 53 (Monday, March 20, 2023)]
[Proposed Rules]
[Pages 16776-16832]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-05107]



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Vol. 88

Monday,

No. 53

March 20, 2023

Part III





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 Texas Heelsplitter, and Threatened 
Status With Section 4(d) Rule and Critical Habitat for Louisiana 
Pigtoe; Proposed Rule

  Federal Register / Vol. 88, No. 53 / Monday, March 20, 2023 / 
Proposed Rules  

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2022-0026; FF09E21000 FXES1111090FEDR 234]
RIN 1018-BE46


Endangered and Threatened Wildlife and Plants; Endangered Species 
Status With Critical Habitat for Texas Heelsplitter, and Threatened 
Status With Section 4(d) Rule and Critical Habitat for Louisiana Pigtoe

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
list the Texas heelsplitter (Potamilus amphichaenus) as an endangered 
species and the Louisiana pigtoe (Pleurobema riddellii) as a threatened 
species under the Endangered Species Act of 1973, as amended (Act). 
Both species are freshwater mussels. This document serves as our 12-
month finding on a petition to list the Texas heelsplitter and 
Louisiana pigtoe. For the Louisiana pigtoe, we also propose a rule 
issued under section 4(d) of the Act (a ``4(d) rule'') to provide for 
the conservation of the species. In addition, we propose to designate 
critical habitat for the Texas heelsplitter and Louisiana pigtoe under 
the Act. In total, approximately 831.8 river miles (1,338.6 river 
kilometers) in 31 counties in Texas fall within the boundaries of the 
proposed critical habitat designation for the Texas heelsplitter, and 
approximately 1,028.2 river miles (1,654.3 river kilometers) in 3 
counties in Arkansas, 6 parishes in Louisiana, 2 counties in 
Mississippi, 1 county in Oklahoma, and 21 counties in Texas fall within 
the boundaries of the proposed critical habitat designation for the 
Louisiana pigtoe. We announce the availability of a draft economic 
analysis of the proposed designation of critical habitat for the Texas 
heelsplitter and Louisiana pigtoe. Finally, we announce an 
informational meeting followed by a public hearing on this proposed 
rule. If we finalize this rule as proposed, it would extend the Act's 
protections to these species and their critical habitats.

DATES: We will accept comments received or postmarked on or before May 
19, 2023. 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 a 
public informational session from 5 p.m. to 6 p.m., central time, 
followed by a public hearing from 6:30 p.m. to 8 p.m., central time, on 
May 2, 2023.

ADDRESSES: You may submit comments by one of the following methods:
    (1) Electronically: Go to the Federal eRulemaking Portal: https://www.regulations.gov. In the Search box, enter FWS-R2-ES-2022-0026, 
which is the docket number for this rulemaking. Then, click on the 
Search button. On the resulting page, in the panel on the left side of 
the screen, under the Document Type heading, check the Proposed Rule 
box to locate this document. You may submit a comment by clicking on 
``Comment.''
    (2) By hard copy: Submit by U.S. mail to: Public Comments 
Processing, Attn: FWS-R2-ES-2022-0026, U.S. Fish and Wildlife Service, 
MS: PRB/3W, 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 https://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see Information Requested, below, for more information).
    Availability of supporting materials: For the proposed 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/arlingtontexas/, at 
https://www.regulations.gov under Docket No. FWS-R2-ES-2022-0026, and 
at the Arlington Ecological Services Field Office (see FOR FURTHER 
INFORMATION CONTACT). Additional supporting information that we 
developed for this critical habitat designation will be available on 
the Service's website, at https://www.regulations.gov, or both.
    Public informational meeting and public hearing: The public 
informational meeting and the public hearing will be held virtually 
using the Zoom online video platform and via teleconference. See Public 
Hearing, below, for more information.

FOR FURTHER INFORMATION CONTACT: Debra Bills, Field Supervisor, U.S. 
Fish and Wildlife Service, Arlington Ecological Services Field Office, 
501 West Felix Street, Suite 1105, Fort Worth, Texas 76115; telephone 
817-277-1100. Individuals in the United States who are deaf, deafblind, 
hard of hearing, or have a speech disability may dial 711 (TTY, TDD, or 
TeleBraille) to access telecommunications relay services. Individuals 
outside the United States should use the relay services offered within 
their country to make international calls to the point-of-contact in 
the United States.

SUPPLEMENTARY INFORMATION: 

Executive Summary

    Why we need to publish a rule. Under the Act, a species warrants 
listing if it meets the definition of an endangered species (in danger 
of extinction throughout all or a significant portion of its range) or 
a threatened species (likely to become endangered within the 
foreseeable future throughout all or a significant portion of its 
range). If we determine that a species warrants listing, we must list 
the species promptly and designate the species' critical habitat to the 
maximum extent prudent and determinable. We have determined that the 
Texas heelsplitter meets the definition of an endangered species and 
that the Louisiana pigtoe meets the definition of a threatened species; 
therefore, we are proposing to list them as such and proposing a 
designation of critical habitat for both species. Both listing a 
species as an endangered or threatened species and designating critical 
habitat can be completed only by issuing a rule through the 
Administrative Procedure Act rulemaking process.
    What this document does. We propose to list the Texas heelsplitter 
as an endangered species and to list the Louisiana pigtoe as a 
threatened species with a 4(d) rule. We also propose to designate 
critical habitat for both species.
    The basis for our action. Under the Act, we may determine that a 
species is an endangered or threatened species because of 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 that habitat loss through 
changes in water quality, the gradual accumulation of additional layers 
of fine sediments, and altered hydrology (Factor A) are the primary 
threats to these species, all of which are exacerbated by the ongoing 
and expected future effects of climate change (Factor E). Additionally, 
predation (Factor C) and collection (Factor B), as well as other 
natural or human-induced events/activities that result in direct 
mortality, are also

[[Page 16777]]

affecting those populations already experiencing low stream flow, and 
reservoirs and other instream barriers to fish movement (Factor E) that 
limit dispersal and prevent recolonization after stochastic events.
    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 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. Section 4(b)(2) of the 
Act states that the Secretary must make the designation on 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.

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 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 the species, including 
habitat requirements for feeding, breeding, and sheltering;
    (b) Genetics and taxonomy;
    (c) Historical and current ranges, including distribution patterns 
and the locations of any additional populations of these species;
    (d) Historical and current population levels, and current and 
projected trends; and
    (e) Past and ongoing conservation measures for the species, their 
habitats, or both.
    (2) Threats and conservation actions affecting these species, 
including:
    (a) 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.
    (b) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to these species.
    (c) Existing regulations or conservation actions that may be 
addressing threats to these species.
    (3) Additional information concerning the historical and current 
status of these species.
    (4) Information on regulations that are necessary and advisable to 
provide for the conservation of the Louisiana pigtoe and that we can 
consider in developing a 4(d) rule for the species. We particularly 
seek information concerning the extent to which we should include any 
of the section 9 prohibitions in the 4(d) rule or whether we should 
consider any additional exceptions from the prohibitions in the 4(d) 
rule.
    (5) Specific information on:
    (a) The amount and distribution of Texas heelsplitter and Louisiana 
pigtoe habitat;
    (b) Any additional areas occurring within the range of the 
Louisiana pigtoe, i.e., Howard, Little River, and Sevier Counties, 
Arkansas; Allen, Beauregard, Rapides, St. Tammany, Vernon, and 
Washington parishes, Louisiana; Marion and Pearl River Counties, 
Mississippi; McCurtain County, Oklahoma; and Anderson, Angelina, 
Cherokee, Gregg, Hardin, Harrison, Houston, Jasper, Jefferson, Liberty, 
Montgomery, Nacogdoches, Orange, Panola, Polk, Rusk, Smith, Trinity, 
Tyler, Upshur, and Wood Counties, Texas, and Texas heelsplitter, i.e., 
Anderson, Angelina, Cherokee, Ellis, Freestone, Gregg, Grimes, Hardin, 
Harrison, Henderson, Houston, Jasper, Jefferson, Kaufman, Leon, 
Madison, Navarro, Orange, Panola, Polk, Rains, Rusk, Sabine, Shelby, 
Smith, Trinity, Tyler, Upshur, Van Zandt, Walker, and Wood Counties, 
Texas, that should be included in the designation because they (i) 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 (ii) are unoccupied 
at the time of listing and are essential for the conservation of the 
species; and
    (c) 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
    (d) To evaluate the potential to include areas not occupied at the 
time of listing, we particularly seek comments regarding whether 
occupied areas are adequate for the conservation of the species. 
Additionally, please provide specific information regarding whether or 
not unoccupied areas would, 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. We 
also seek comments or information regarding whether areas not occupied 
at the time of listing qualify as ``habitat'' for the species.
    (7) Land use designations and current or planned activities in the 
subject areas and their possible impacts on proposed critical habitat.
    (8) 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.
    (9) 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.
    (10) 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 information supporting a benefit of 
exclusion.
    (11) 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, do not provide substantial 
information necessary to support a determination. 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 and section

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4(b)(2) of the Act directs that the Secretary shall designate critical 
habitat on the basis of the best scientific information 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 https://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 https://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 https://www.regulations.gov.
    Because we will consider all comments and information we receive 
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 Texas 
heelsplitter is threatened instead of endangered or that Louisiana 
pigtoe is endangered instead of threatened, or we may conclude that one 
or both species do not warrant listing as either an endangered species 
or a threatened species. For critical habitat, our final designations 
may not include all areas proposed, may include some additional areas 
that meet the definition of critical habitat, or may exclude some areas 
if we find the benefits of exclusion outweigh the benefits of 
inclusion. In addition, we may change the parameters of the 
prohibitions or the exceptions to those prohibitions in the 4(d) rule 
if we conclude it is appropriate in light of comments and new 
information we receive. For example, we may expand the prohibitions to 
include prohibiting additional activities if we conclude that those 
additional activities are not compatible with conservation of the 
species. Conversely, we may establish additional exceptions to the 
prohibitions in the final rule if we conclude that the activities would 
facilitate or are compatible with the conservation and recovery of the 
species.

Public Hearing

    We have scheduled a public informational meeting and public hearing 
on this proposed rule. We will hold the public informational meeting 
and public hearing on the date and at the times provided above under 
Public informational meeting and public hearing in DATES. We are 
holding the public informational meeting and public hearing via the 
Zoom online video platform and via teleconference so that participants 
can attend remotely. For security purposes, registration is required. 
You must register in order 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. For 
information on how to register, or if you encounter problems joining 
Zoom the day of the meeting, visit https://www.fws.gov/office/arlington-ecological-services. Registrants will receive the Zoom link 
and the telephone number for the public informational meeting and 
public hearing. 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 meeting and public 
hearing.
    The public hearing will provide interested parties an opportunity 
to present verbal testimony (formal, oral comments) regarding this 
proposed rule. The public informational meeting will be an opportunity 
for dialogue with the Service. The public hearing is 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 hearing must register before the hearing 
(https://www.fws.gov/office/arlington-ecological-services). The use of 
a virtual public hearing is consistent with our regulations at 50 CFR 
424.16(c)(3).

Previous Federal Actions

    The Texas heelsplitter was identified as a category 2 candidate 
species on January 6, 1989 (54 FR 554). The category 2 designation was 
assigned to taxa for which information indicated that proposing to list 
as endangered or threatened was possibly warranted, but for which 
conclusive data on biological vulnerability and threats were not 
currently available to support proposed rules. The species remained so 
designated in subsequent candidate notices of review (CNORs) (56 FR 
58804, November 21, 1991; 59 FR 58982, November 15, 1994). In the 
February 28, 1996, CNOR (61 FR 7596), we discontinued the designation 
of category 2 species as candidates; therefore, with the publication of 
that CNOR, the Texas heelsplitter was no longer a candidate species.
    On June 25, 2007, we were petitioned to list both the Texas 
heelsplitter and Louisiana pigtoe. We published a substantial 90-day 
finding for Texas heelsplitter on December 15, 2009 (74 FR 66260), and 
for Louisiana pigtoe on December 16, 2009 (74 FR 66866).
    This document constitutes our 12-month warranted petition finding, 
our proposed listing rule, and our proposed critical habitat rule for 
the Texas heelsplitter and Louisiana pigtoe.

Supporting Documents

    A species status assessment (SSA) team prepared an SSA report for 
the Texas heelsplitter and Louisiana pigtoe. The SSA team was composed 
of Service biologists, in consultation with other species experts. The 
SSA report represents a compilation of the best scientific and 
commercial data available concerning the status of the species, 
including the impacts of past, present, and future factors (both 
negative and beneficial) affecting the species. 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 11 appropriate specialists regarding the 
SSA. We received 6 responses.

I. Proposed Listing Determination

Background

General Mussel Biology

    A thorough review of the taxonomy, life history, and ecology of the 
Texas heelsplitter and Louisiana pigtoe is presented in the SSA report 
(USFWS 2022, entire), and briefly summarized here.
    Freshwater mussels, including the Texas heelsplitter and Louisiana 
pigtoe, 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

[[Page 16779]]

sperm into the water column, which is taken in by the female through 
the incurrent aperture (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 mantle displays 
(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.

Texas Heelsplitter

    The Texas heelsplitter was first described as the species Unio 
amphichaenus by Frierson (1898, p. 109) from the Sabine River near 
Logansport, Louisiana. The current recognized scientific name for Texas 
heelsplitter is Potamilus amphichaenus (Williams et al. 2017a, pp. 35, 
42). The Texas heelsplitter is a medium- to large-sized freshwater 
mussel (up to 177 millimeters (mm) (7 inches (in)) shell length) that 
has a tan to brown or black elliptical shell, with lighter coloration 
on the beaks, and a relatively straight hinge line. Texas heelsplitters 
exhibit slight sexual dimorphism; females have a broadly rounded 
posterior margin and males are more pointed (Howells 2010b, p. 2). The 
base of the anterior margin exhibits a long, narrow gape, while a 
shorter, much wider gape is located along the posterior margin, 
presumably to accommodate the incurrent and excurrent apertures (Neck 
and Howells 1995, p. 4).
    Although information specific to Texas heelsplitter reproduction is 
unavailable, other species from the tribe Lampsilini release glochidia 
in packets, called conglutinates, and are known to use mantle lures to 
attract sight feeding fishes that attack and rupture the marsupium, 
thereby becoming infested by glochidia (Barnhart et al. 2008, pp. 377, 
380). Related 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). Freshwater drum (Aplodinotus grunniens) 
have been confirmed as host fish for the Texas heelsplitter (Bosman et 
al. 2015, p. 15).
    A related freshwater mussel species, bleufer (Potamilus 
purpuratus), from the southeastern United States was reported to reach 
a maximum age of 9-26 years, and other related species ranged from 4-50 
years with a higher growth rate compared to other species (Haag and 
Rypel 2011, pp. 229, 234, 239). The Texas heelsplitter has been 
reported mature at approximately 60 mm (2.4 in) (Ford et al. 2016, p. 
31).
    Texas heelsplitters occur in streams and rivers of the Trinity, 
Neches, and Sabine drainages in east Texas and in the Sabine River at 
the western border of Louisiana on substrates consisting of ``firm mud, 
sand, or finer gravels bottoms, in still to moderate flows'' and 
sometimes associated with fallen timber (Howells 2014, p. 69; Howells 
2010b, p. 3 and table 2.3). Additionally, Texas heelsplitters can 
tolerate manmade impoundments and have been found in several East Texas 
reservoirs (Howells 2010b, p. 3).

Louisiana Pigtoe

    The Louisiana pigtoe was originally described as the species Unio 
riddellii (Lea 1862, p. 228) from the Trinity River near the City of 
Dallas, Dallas County, Texas. The current recognized scientific name 
for Louisiana pigtoe is Pleurobema riddellii (Williams et al. 2017a, 
pp. 35, 42). The Louisiana pigtoe is a medium-sized freshwater mussel 
(shell lengths to greater than 62 mm (2.4 in)) with a brown to black, 
triangular to subquadrate shell without external sculpturing, sometimes 
with greenish rays. For a detailed description, see Howells et al. 1996 
(pp. 91-92) and Howells 2014 (p. 65). Other native mussel species 
(e.g., pimpleback (Cyclonaias pustulosa), Texas pigtoe (Fusconaia 
askewi), Trinity pigtoe (F. chunii), and Wabash pigtoe (F. flava)) can 
easily be mistaken for Louisiana pigtoe when identified by shell 
morphology alone.
    Louisiana pigtoe are bradytictic (i.e., long-term brooders; 
spawning occurs during the summer, and glochidia are held by the female 
over winter and released the following spring); however, gravid females 
have been observed in July (Marshall 2014, pp. 46-47). A closely 
related congener, the rough pigtoe (Pleurobema plenum), is known to 
utilize the tachytictic reproductive cycle (i.e., short-term brooders; 
fertilization occurs in the spring, and glochidia are expelled during 
the summer or early fall) (EPA 2007, p. 37).
    The primary host fish for Louisiana pigtoe has not been confirmed. 
Bullhead minnow (Pimephales vigilax), blacktail shiner (Cyprinella 
venusta), and red shiner (Cyprinella lutrensis) have been suggested as 
potential fish hosts based on a fish host distribution modeling effort 
(Marshall 2014, pp. 59-60).
    A single juvenile Louisiana pigtoe from the Neches River, Texas, 
was reported to grow 15 mm (0.6 in) during its first year from an 
initial shell length of 2 mm (0.08 in) (Ford et al. 2016, p. 30). 
Sexual maturity is achieved at shell lengths around 40 mm (1.6 in) 
(Ford et al. 2016, pp. 28, 30), and Louisiana pigtoe could reach 
maturity in 3 to 4 years. Based on egg production, sexually mature 
females were estimated by external annuli to be between 4 and 12 years 
of age with shell lengths ranging

[[Page 16780]]

from 29-59 mm (1.1-2.3 in) (Hinkle 2018, p. 19).
    Louisiana pigtoes occur in medium- to large-sized streams 
throughout portions of east Texas, Louisiana, west Mississippi, 
southeast Oklahoma, and southwest Arkansas (Vidrine 1993, p. 66; 
Howells et al. 1997, p. 22; Randklev et al. 2013, p. 269; Randklev 
2018, entire) in flowing waters (0.3-1.4 meters per second (m/s)) over 
substrates of cobble and rock or sand, gravel, cobble, and woody 
debris; they are often associated with riffle, run, and sometimes 
larger backwater tributary habitats (Ford et al. 2016, pp. 42, 52; 
Howells 2010a, pp. 3-4; Williams et al. 2017b, p. 21). Specimens are 
typically found in shallower waters (0.1-1.2 m (0.3-3.9 feet (ft) in 
depth; Howells 2010a, p. 3)); however, recent surveys found Louisiana 
pigtoe as deep as 3.33 m (10.9 ft) in the lower Neches River (Corbett 
2020, pp. 2, 4).

Regulatory and Analytical Framework

Regulatory Framework

    Section 4 of the Act (16 U.S.C. 1533) and the implementing 
regulations in title 50 of the Code of Federal Regulations set forth 
the procedures for determining whether a species is an endangered 
species or a threatened species, issuing protective regulations for 
threatened species, and designating critical habitat for endangered and 
threatened species. In 2019, jointly with the National Marine Fisheries 
Service, the Service issued a final rule that revised the regulations 
in 50 CFR part 424 regarding how we add, remove, and reclassify 
endangered and threatened species and the criteria for designating 
listed species' critical habitat (84 FR 45020; August 27, 2019). On the 
same day, the Service also issued final regulations that, for species 
listed as threatened species after September 26, 2019, eliminated the 
Service's general protective regulations automatically applying to 
threatened species the prohibitions that section 9 of the Act applies 
to endangered species (84 FR 44753; August 27, 2019).
    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:
    (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.
    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 review of the best scientific and commercial data regarding 
the status of the species, including an assessment of the potential 
threats to the species. The SSA report does not represent a decision by 
the Service on whether the species should be proposed for listing as an 
endangered or threatened species under the Act. It does, however, 
provide the scientific basis that informs our regulatory decisions, 
which involve 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-2022-0026 on https://www.regulations.gov.
    To assess the viability of the Texas heelsplitter and Louisiana 
pigtoe, 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

[[Page 16781]]

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 each individual species' life-
history needs. The next stage involved an assessment of the historical 
and current condition of each 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 each species' responses to positive and negative 
environmental and anthropogenic influences. Throughout all of these 
stages, we 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 condition, in order to assess the species' 
overall viability and the risks to that viability. We analyze these 
factors both individually and cumulatively to determine the current 
condition of the species and project the future condition of the 
species under several plausible future scenarios.
    Using various timeframes and the current and projected future 
resiliency, redundancy, and representation, we describe the species' 
levels of viability over time. For the Texas heelsplitter and Louisiana 
pigtoe to maintain viability, their populations or some portion thereof 
must be sufficiently resilient. A number of factors influence the 
resiliency of their populations, including occupied stream length, 
abundance, and recruitment. Elements of the species' habitat that 
determine whether Texas heelsplitter and Louisiana pigtoe populations 
can grow to maximize habitat occupancy influence those factors, thereby 
increasing the resiliency of populations. These 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 Texas heelsplitter and 
Louisiana pigtoe, are found in aggregations called mussel beds that 
vary in size from about 50 to over 5,000 square meters (m\2\), 
separated by stream reaches in which mussels are absent or rare (Vaughn 
2012, p. 2). Mussel populations in streams are highly patchy, 
especially at a small scale (less than 100 stream meters) (Strayer 
1999, p. 468). We define a mussel population at a larger scale than a 
single mussel bed; it is the collection or series of mussel beds within 
a stream reach between that 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, adequately resilient mussel 
populations must occupy stream reaches that are long enough such that 
stochastic events that adversely affect individual mussel beds do not 
eliminate the entire population. Repopulation by glochidia-infested 
fish from other mussel beds within the reach, if present and connected, 
allow the population to recover from the temporary loss of individuals 
due to occasional disruptive events.
    For our analysis, we consider populations extending greater than 50 
river miles (river mi) (80 kilometers (km)) to have a high probability 
of persistence to stochastic events because a single event is unlikely 
to affect the entire population. Populations occupying reaches between 
20 and 50 river mi (32 and 80 km) have moderate resiliency to 
stochastic events, while populations occupying reaches less than 20 mi 
(32.19 km) have low resiliency. Note that we define populations 
occupying a stream length at or approaching zero miles as being 
functionally extirpated (populations with abundance that is currently 
at such low levels that we expect them to become extirpated in the near 
future) or extirpated.
Abundance
    Populations require a minimum number of individuals to ensure 
stability and persistence. This threshold is often referred to as the 
minimum viable population and is generally calculated through a 
population viability analysis that estimates extinction risk given a 
number of input variables. There are no published minimum viable 
population estimates for the Texas heelsplitter or Louisiana pigtoe; 
therefore, it is unknown how many individuals are required to sustain 
populations of these mussels. However, population health is dependent 
on species abundance as well as water availability and the ability for 
mussels to meet life-history needs within their habitats, which were 
evaluated as part of the SSA.
    It is important to recognize that Louisiana pigtoe observations 
used to determine abundance in the SSA report may include misidentified 
individuals. Without genetic confirmation, identification of Louisiana 
pigtoe in the field based on shell morphology is questionable, with 
seasoned experts accurately identifying the species only 76 percent of 
the time (Inoue 2018, p. 1). Unfortunately, genetic testing was not 
available for the majority of reported Louisiana pigtoe historical 
observations, which relied solely on shell morphological 
characteristics for species identification (Randklev 2018, entire). 
Since there is no way to know the margin of error or to otherwise 
account for potential misidentifications, we determined abundance for 
Louisiana pigtoe based on reported observations (as is) and did not 
adjust or modify the survey data to compensate for potential 
misidentifications. We do not consider misidentification to be an issue 
for Texas heelsplitter observations, since they are recognizable based 
on morphological characteristics observed in the field and not easily 
confused with other species.
    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 Texas heelsplitter and Louisiana pigtoe to be healthy 
(i.e., adequately resilient), mussel beds of sufficient number and 
density must be present to allow recovery from natural and local 
stochastic events, allowing the mussel bed to persist and the overall 
local population to survive within a stream reach. Mussel abundance is 
indicated by the number of individuals found during a sample event. 
Mussel surveys are rarely a complete census of the population, but 
density can be estimated by the number of individuals found during a 
survey effort using various statistical techniques (i.e., estimate the 
total population from a subset of surveyed individuals). Population 
estimates are not available for all Texas heelsplitter and Louisiana 
pigtoe populations, and techniques for available surveys are not always 
directly comparable (i.e., same area size searched, similar search 
time, etc.). When available, we used the number of

[[Page 16782]]

individuals captured relative to the amount of time surveys were 
conducted to estimate population abundance, hereafter referred to as 
overall catch per unit effort (CPUE). Although overall CPUE was the 
preferred metric to estimate population abundance, when overall CPUE 
was not available, the number of individuals detected during the most 
recent comprehensive survey effort was used as a surrogate metric. 
Calculation of abundance in this manner is intended to be an estimate 
and is considered the best available information when population trend 
data do not exist and precise population abundance cannot be 
determined. Using CPUE, we are able to estimate if the species is 
currently (since year 2000) common or rare within populations. 
Abundance for each population is rated from ``high'' to ``low'' (or 
functionally extirpated/extirpated) based on overall CPUE (or number of 
individuals found when survey effort is not reported) according to live 
or recent dead found during surveys since the year 2000, as follows: 
``high'' is overall CPUE of greater than or equal to 4.0 (or 100 or 
more individuals); ``moderate'' is overall CPUE greater than or equal 
to 2.0 and less than 4.0 (or between 25 individuals and 99 
individuals); ``low'' is overall CPUE greater than or equal to 0.5 and 
less than 2.0 (or between 3 and 24 individuals); and ``functionally 
extirpated/extirpated'' is overall CPUE less than 0.5 (or fewer than 3 
individuals).
Reproduction/Recruitment
    Sufficiently resilient Texas heelsplitter and Louisiana pigtoe 
populations must also be reproducing and recruiting young individuals 
into the population to replace individuals lost to old age, disease, or 
predation. Population size and abundance are a reflection of habitat 
conditions, environmental stressors, and other past influences on the 
population. The ability of populations to successfully reproduce and 
recruit will determine if a population 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 if there are few young individuals to sustain the 
population over time (i.e., death rates exceed birth rates resulting in 
negative population growth). Conversely, a population that is less 
dense but has many young and/or gravid individuals is likely to grow, 
becoming more densely populated in the future (i.e., birth rates, and 
subsequent recruitment of reproductive adults, exceed 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 involves tactile 
searches and mussels less than 35 mm (1.4 in) can be difficult to 
detect (Strayer and Smith 2003, pp. 47-48). For this evaluation, we 
concluded there was evidence of reproduction/recruitment for a 
population when surveys detected small-sized individuals (near the low 
end of the detectable range or approximately 35 mm (1.4 in) in size) 
since the year 2000 or gravid females (eggs and/or glochidia visible) 
were observed during the reproductively active time of year.

Risk Factors for Texas Heelsplitter and Louisiana Pigtoe

    We reviewed the potential risk factors (i.e., threats, stressors) 
that could be affecting the Texas heelsplitter and Louisiana pigtoe 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. Many of the threats and risk factors are the same or similar 
for both species. Where the effects are expected to be similar, we 
present one discussion that applies to both species. Where the effects 
may be unique to one species, we will address that specifically. The 
primary risk factors (i.e., threats) affecting the status of the Texas 
heelsplitter and Louisiana pigtoe all fall under Factor A of the Act 
and are: (1) Water quality changes, (2) altered hydrology, (3) changes 
to habitat structure and substrate, and (4) habitat fragmentation. 
These factors are all exacerbated by the ongoing and expected effects 
of climate change (Factor E). Additionally, predation (Factor C) and 
collection (Factor B), as well as other natural or human induced 
events/activities that result in direct mortality, are also affecting 
those populations already experiencing low stream flow, and reservoirs 
and instream barriers to fish movement (Factor E) limit dispersal and 
prevent recolonization after stochastic events.
Changes to Water Quality
    Freshwater mussels require water in sufficient quantity and quality 
on a consistent basis to complete their life cycles and those of their 
host fishes. Water quality can be degraded through contamination or 
alteration of water chemistry. Environmental contaminants include a 
broad array of natural, synthetic, and chemical substances introduced 
to the environment that can be hazardous to living organisms. Chemical 
contaminants are ubiquitous throughout the environment and are a major 
contributor to the current declining status of freshwater mussel 
species nationwide (Augspurger et al. 2007, p. 2025). Contaminants 
enter the environment through both point (e.g., hazardous spills, 
industrial wastewater, municipal effluents) and non-point (e.g., urban 
stormwater and agricultural runoff) sources. These sources contribute 
organic compounds, trace metals, pesticides, plastics, petroleum 
hydrocarbons, flame retardants, and a wide variety of emerging 
contaminants (e.g., pharmaceuticals and personal care products). 
Ammonia is of particular concern below wastewater treatment plant 
outfalls because freshwater mussels have been shown to be particularly 
sensitive to increases in ammonia levels (Augspurger et al. 2003, p. 
2569). The extent to which environmental contaminants adversely affect 
aquatic biota can vary depending on many site-specific variables, but 
species diversity and abundance consistently ranks lower in waters that 
are known to be polluted or otherwise impaired by contaminants. For 
example, freshwater mussels are not generally found for many miles 
downstream of municipal wastewater treatment plants (treatment plants) 
(Gillis et al. 2017, p. 460; Goudreau et al. 1993, p. 211; Horne and 
McIntosh 1979, p. 119).
    There are approximately 386 treatment plant discharge permits 
issued for the Trinity River Basin from its headwaters above the 
Dallas-Fort Worth metroplex down to the Gulf of Mexico (Texas 
Commission on Environmental Quality (TCEQ) 2018, entire). The San 
Jacinto Basin, although geographically smaller than most other basins 
in Texas, has approximately 1,052 treatment plant outfalls, while the 
Neches and Sabine rivers have 218 and 191 outfalls, respectively. In 
addition, some industrial permits can discharge millions of gallons per 
day and have ammonia limits that exceed levels that inhibited growth in 
juvenile fatmucket (Lampsilis siliquoidea) and rainbow mussel (Villosa 
iris) during 28-day chronic tests (Wang et al. 2007, entire). Immature 
mussels (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).
    An additional type of water quality impairment is the alteration of 
water quality parameters such as dissolved oxygen, temperature, total 
dissolved solids (TDS), and salinity levels. Dissolved oxygen levels 
may be reduced from increased nutrients in the water

[[Page 16783]]

from runoff or wastewater effluent, and juveniles seem to be 
particularly sensitive to low dissolved oxygen (Sparks and Strayer 
1998, pp. 132-133). Increases in water temperature from water 
diversions, climate change, or low flows during droughts can exacerbate 
low dissolved oxygen levels as well as have its own effects on juvenile 
and adult mussels.
    Total dissolved solids, a measure of the mineral content of water 
(i.e., inorganic salts, metals, cations, or anions dissolved in water, 
including calcium, magnesium, potassium, sodium, bicarbonates, 
chlorides, and sulfates), is commonly elevated in watersheds impacted 
by a variety of industrial, commercial, urban, and agricultural 
activities and has been associated with acute and chronic toxicity to 
aquatic organisms. Watersheds with increasing trends in conductivity or 
TDS are experiencing declines in water quality that can be harmful to 
mussels and other aquatic organisms. Increasing trends in TDS are 
common in watersheds impacted by anthropogenic activities.
    Contaminant spills are also a concern. Texas leads the nation in 
crude oil and natural gas production, and various chemicals, refined 
fuels, and wastewater related to oil and natural gas exploration are 
routinely transported along highways. These facilities and equipment 
used for extraction, transportation, and refinement of hazardous 
materials are all potential sources of hazardous spills, and can 
originate from human error, equipment failure, or catastrophic events 
like industrial accidents, fires, or floods. Although spills are 
relatively short-term events and may be localized, water resources 
nearby can be severely impacted and degraded for years after the 
incident along with the biological resources that inhabit the area. A 
reduction in surface flow drought, instream diversions, or groundwater 
extraction serve to concentrate contaminant and salinity levels, 
increases water temperatures in streams, and exacerbates effects to 
Texas heelsplitter and Louisiana pigtoe.
    Poor water quality affects most Texas heelsplitter and Louisiana 
pigtoe populations currently to some degree, and future water quality 
is expected to decrease due to decreasing stream flow and increasing 
temperatures. We foresee threats to water quality increasing into the 
future due to the effects of climate change as demand and competition 
for limited water resources grows (USFWS 2022, pp. 61-62).
Altered Hydrology
    Altered hydrology, through changes to historical flow regimes, 
leads to inundation, or low- or high-flow conditions that may reduce 
the quality of affected habitats to the point where they are no longer 
suitable for freshwater mussels. While Texas heelsplitter and Louisiana 
pigtoe have adapted to survive natural fluctuations in flows, 
populations that experience sustained higher than normal flows, 
prolonged flooding, or unnatural fluctuations in the frequency or 
intensity of high/low flows or extended (or repeated) drying events 
will not persist. Virtually every watershed within the range of these 
two freshwater mussels has experienced some level of alteration, a 
trend that has continued into the 21st century, particularly in areas 
with rapid population growth.
    Inundation of previously free-flowing rivers and streams by 
impoundments has arguably had the single largest human-related impact 
on the distribution of freshwater mussels. The construction of 
reservoirs and other impoundments permanently alters the hydrology and, 
hence, the ecology of rivers, often with deleterious effects to water 
quality, water quantity, host fish movement, and dispersal of mussel 
glochidia, nutrient cycling, sediment deposition, fate and transport of 
contaminants, and numerous other changes to the physical, chemical, and 
biological characteristics of affected areas (upstream and downstream). 
The close relationship of flow to mussels makes them uniquely 
vulnerable to hydrology changes.
    Both mussel species are adapted to flowing water (lotic habitats) 
rather than standing water (lentic habitats). Louisiana pigtoe require 
free-flowing water to survive. The Texas heelsplitter has also been 
observed in lentic habitats and appears to be tolerant of reservoir 
conditions; this species may occur in higher densities in areas of 
reservoirs that are influenced by stream inflows where conditions more 
closely resemble their preferred riverine habitat (Whisenant 2019, p. 
1; Neck and Howells 1995, p. 15).
    Inundation of mussel habitat has primarily occurred upstream of 
dams, including major flood control and water supply reservoirs, such 
as Toledo Bend Reservoir, and smaller structures like low water vehicle 
crossings and diversion dams typically found along tributaries on 
privately owned land. These structures alter the hydrology of rivers by 
slowing, impeding, or diverting normal flow patterns, and increasing 
deposition in some areas and eliminating the interstitial spaces that 
juvenile Texas heelsplitters and Louisiana pigtoes inhabit.
    Large reservoirs that release water from the hypolimnion, the 
deeper water is cold and often devoid of oxygen and necessary 
nutrients, can adversely affect mussel survival, as cold water can 
stunt mussel growth and delay or hinder spawning (Vaughn and Taylor 
1999, p. 917). Cold water releases from reservoirs like Broken Bow Lake 
in southeast Oklahoma can affect water temperatures for miles 
downstream. These cold releases create an extinction gradient, where 
freshwater mussels are absent or presence is low near the dam, and 
abundance does not rebound until some distance downstream where ambient 
conditions raise the water temperature to within the tolerance limits 
of mussels (Davidson et al. 2014, p. 29; Vaugh and Taylor 1999, pp. 
915, 916).
    The construction of dams for flood control and drinking water 
supply, and the subsequent management of water releases from those 
reservoirs (e.g., timing, intensity, and duration), often resulting in 
higher base flows and peak flows of reduced intensity but longer 
duration, has significant impacts on the natural function and hydrology 
of rivers and streams. The additional shear stress caused by these 
sustained high base flows can incise channels, erode river banks, scour 
mussel beds, and remove substrate preferred by mussels. Over time, the 
physical force of these higher base flows can dislodge mussels from the 
sediment and permanently alter the geomorphology of rivers.
    During flood events, along with water, rivers transport sediment, 
mostly as solids, suspended in the water column. The increase in 
flooding severity results in greater sediment transport, with important 
effects to substrate stability and benthic habitats for freshwater 
mussels, as well as other organisms that are dependent on stable 
benthic habitats. Further, water released by dams is usually clear due 
to reduced sediment load and results in incision (downcutting of the 
bed) and coarsening of the bed material until a new equilibrium is 
reached (Kondolf 1997, p. 535). The extent to which downcutting and 
erosion occurs as a result of dam releases varies, but in some cases 
leads to bank collapse, burial of mussel beds, and mortality. 
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 reservoirs for flood control, water supply, and 
recreation results in altered hydrologic regimes,

[[Page 16784]]

including an attenuation of both high- and low-flow events. The changes 
to flood flows alters sediment dynamics, as sediments are trapped above 
and scoured below major impoundments, and negatively affect freshwater 
mussels and their habitats (Gascho Landis and Stoeckel 2016, p. 234; 
Ford 2013, p. 3). Evidence that the Texas heelsplitter is able to 
tolerate reservoir conditions leads us to believe the overall impacts 
of reservoirs may be more pronounced for the Louisiana pigtoe (Howells 
2010b, p. 3).
    Very low flows and low water levels are also detrimental to Texas 
heelsplitter and Louisiana pigtoe populations. Droughts that occurred 
in the recent past led to extremely low flows in several east Texas 
rivers. Some rivers, or portions thereof, are resilient to drought 
because they are spring-fed (Calcasieu, Neches rivers), contain large 
volumes of water (Trinity River), have large reservoirs in the upper 
reaches that release water for downstream users (all, excluding 
Calcasieu River), or have significant return flows (Pearl, Sabine, 
Trinity rivers); however, drought in combination with increasing trends 
in groundwater extraction may lead to lower river flows of longer 
duration than previously recorded. Reservoir releases can be managed to 
some extent, but in many cases dam operators must stop releases during 
droughts to conserve water and protect water supplies, or to maximize 
flood releases during major floods to protect public safety and 
property, both can negatively affect mussels downstream.
    Streamflow and overall discharge for rivers inhabited by the Texas 
heelsplitter and Louisiana pigtoe are expected to decline due to 
climate change and projected increases in temperatures and evaporation 
rates, resulting in more frequent and intense droughts (Lafontaine et 
al. 2019, entire) (Factor E). Return flows, consisting primarily of 
treated municipal wastewater, are projected to continue to increase in 
areas with population growth and may serve to ameliorate some of the 
effects of climate change downstream of metropolitan areas, albeit with 
notable impacts to water quality; however, these benefits may become 
less significant as municipalities increase wastewater reuse as a 
conservation measure. The Trinity River, for example, has been a 
significantly modified, highly controlled, and highly regulated system 
since the 1960s, with low flows steadily increasing as the population 
has grown, resulting in base flows that are significantly higher 
compared to historical flows (Clark and Mangham 2019, p. 9). The 
increase in base flows can be attributed to substantial return flows 
from Dallas/Fort Worth metropolitan area wastewater treatment plants 
and are projected to continue to increase in the future. Surface and 
alluvial aquifer groundwater withdrawals will likely increase in the 
future due to the effects of more intense droughts, with reductions in 
stream flows putting an additional strain on aquatic resources. 
However, with the exception of stream segments where municipal effluent 
return flows supplement base flows, most streams experience lower base 
flows and reduced high-flow events after major reservoirs are 
constructed (U.S. Geological Survey (USGS) 2008, pp. 964, 966).
    Many streams within the range of these two freshwater mussel 
species receive significant groundwater inputs from multiple springs 
associated with aquifers. As spring flows decline due to drought, 
climate change, or groundwater pumping, habitat for freshwater mussels 
in affected streams is reduced and could eventually cease to exist. 
While the Texas heelsplitter and Louisiana pigtoe may survive short 
periods of low flow, as low flows persist, mussels can be subjected to 
oxygen deprivation, increased water temperature, stranding, increased 
predation, and, ultimately, desiccation which leads to reduced 
survivorship, reproduction, and recruitment to the population. High-
flow events can lead to increased risk of mortality through physical 
removal, transport, or burial of mussels as unstable substrates are 
transported downstream by flood waters (entrainment) and dislodged 
mussels are later redeposited in locations that may not be suitable 
habitat.
    The distribution of mussel communities and their habitats is 
affected by large floods returning at least once during the typical 
life span of an individual mussel (generally from 3-30 years), as 
mediated by the presence of flow refuges, where shear stress is 
relatively low, sediments are relatively stable, and mussels must 
either tolerate high-frequency disturbances or be eliminated and can 
colonize only areas that are infrequently disturbed between events 
(Strayer 1999, pp. 468-469). Shear stress and relative shear stress are 
limiting to mussel abundance and species richness (Randklev et al. 
2017, p. 7), and riffle habitats may be more resilient to high-flow 
events than bank habitats.
    The Texas heelsplitter and Louisiana pigtoe undoubtedly evolved in 
the presence of extreme hydrological conditions, including severe 
droughts leading to dewatering, and heavy rains leading to damaging 
scour events and movement of mussels and substrate, although the 
frequency, duration, and intensity of these events may be different 
from what is observed today. These same patterns led to the development 
of flood control and storage reservoirs throughout Texas in the 20th 
century. The increasing variability, frequency, and severity of extreme 
weather events is a contributing factor to the contraction of 
populations for both species.
    Another source of alteration to hydrology is from sand and gravel 
mining directly from rivers or from adjacent alluvial deposits (Kondolf 
1997, p. 541). Instream mining directly impacts river habitats by 
removal of substrates used by mussels, 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 knickpoint, which can contribute to erosion 
(and mobilization of substrate) associated with head cutting (Kondolf 
1997, p. 541). Pits associated with off-channel mining of the 
floodplain can become involved during floods, such that the pits become 
hydrologically connected, and thus can affect sediment dynamics in the 
stream or river (Kondolf 1997, p. 545). Sand and gravel mines occurred 
historically and continue to operate in some basins throughout the 
ranges of the Texas heelsplitter and Louisiana pigtoe.
    Specifically, a change to the number of days with zero flow was 
limiting for the Louisiana pigtoe, and the number of high pulses was 
limiting for the Texas heelsplitter. In summary, results to date 
indicate natural flow regimes have been altered in east Texas rivers, 
as was expected, which has led to modification of instream habitats and 
contributed to declines in freshwater mussels (Khan and Randklev 2019, 
entire). These findings agree with the estimate of many experts, who 
based on their research believe: (1) Portions of the Trinity River have 
been significantly modified and may no longer support mussels 
(particularly in the upper basin where stream hydrology and 
geomorphology have been permanently altered), and (2) the Neches River 
is the least altered and has some of the best remaining mussel habitat, 
along with the most abundant and diverse mussel populations, in east 
Texas.
Changes to Habitat Structure/Substrate
    Texas heelsplitters and Louisiana pigtoes inhabit microhabitat 
along river stream beds that have abundant

[[Page 16785]]

interstitial spaces or small openings in an otherwise closed matrix of 
stable substrates created by gravel, cobble, boulders, bedrock 
crevices, tree roots, and other vegetation, with some amount of fine 
sediment (i.e., clay and silt) necessary to provide appropriate 
shelter. Excessive amounts of fine sediments can reduce available 
microhabitat by filling in these interstitial spaces, effectively 
smothering mussels in place. Interstitial spaces provide essential 
habitat for juvenile mussels, offering protection from predation and 
vital nutrients. While adult mussels can be physically buried by 
excessive sediment, the main impacts of excess sedimentation on 
freshwater mussels are often sublethal and include interference with 
feeding mediated by valve closure (Box and Mossa 1999, p. 101).
    Under a natural flow regime, sediments are naturally washed away 
from one microhabitat to another, the amount of sediment in the 
substrate is relatively stable, and different reaches within a river or 
stream may be aggrading or degrading sediment at any given time (Poff 
et al. 1997, pp. 770-772). Current (and past) human activities often 
result in enhanced sedimentation in river systems, including legacy 
sediment from past land disturbances and reservoir construction. These 
activities continue in many basins occupied by the Texas heelsplitter 
and Louisiana pigtoe, and influence river processes and sediment 
dynamics (Wohl 2015, pp. 31, 39), with legacy effects that can result 
in degradation of mussel habitat. Sediments deposited by large-scale 
flooding or other disturbance may persist for several years until 
adequate cleansing flows can redistribute that sediment downstream. 
Conversely, when water velocity decreases 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, 
including streambank erosion from development, agricultural activities, 
livestock and wildlife grazing, 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 on water 
quantity and quality are long lasting and can result in hydrological 
alterations as increased impervious cover increases run off and 
resulting shear stress causes streambank instability and additional 
sedimentation.
Habitat Fragmentation
    Historically, the Texas heelsplitter and Louisiana pigtoe were 
likely distributed in areas with suitable habitat throughout the river 
basins described above under Background. Today, the remaining Texas 
heelsplitter and Louisiana pigtoe populations are isolated from one 
another by major reservoirs, habitat alterations, and de-watering 
events, prolonged drought, among other reasons, such that natural 
recolonization of areas previously extirpated is extremely unlikely, if 
not impossible, due to barriers to host fish movement. With the 
exception of the Louisiana pigtoe populations in the Red River Basin in 
Arkansas and Oklahoma, there is currently no opportunity for 
substantial interaction among extant Texas heelsplitter and Louisiana 
pigtoe populations, resulting in genetic isolation.
    The impacts of reservoirs are significant, causing permanent 
changes to fish movement, water quality, and hydrology, with cascading 
effects to river ecology and aquatic species that utilize areas 
downstream. Small populations are more affected by limited host fish 
immigration potential because they are susceptible to genetic drift 
(random loss of genetic diversity) and inbreeding depression. At the 
species level, populations that are eliminated due to stochastic events 
cannot be recolonized naturally, leading to reduced overall redundancy 
and representation.
    The confirmed or assumed primary host fish species for both the 
Texas heelsplitter and Louisiana pigtoe are known to be common and 
widespread throughout the range of both mussel species and are 
therefore not believed to be a limiting factor to dispersal at this 
time (Nico and Sturtevant 2022, entire; Nico et al. 2022, entire; Nico 
and Fuller 2022, entire; Fuller et al. 2022, entire). Each of the 
identified fish hosts are known to tolerate lake environments and may 
utilize impoundments as corridors to facilitate migration between 
hydrologically connected tributaries, thus aiding mussel dispersal. If 
fish host species are indeed abundant, existing dams, the construction 
of new major dams and reservoirs, and other barriers to fish movement 
are the primary mechanism through which remaining populations are 
isolated. Furthermore, reservoir impacts to river ecosystems can be 
difficult and costly to manage or minimize.
    Most reservoirs function primarily to provide water supply and/or 
flood control, and meeting those objectives typically involves holding 
on to as much water as possible (i.e., not releasing); this may limit 
the ability of reservoir managers to modify releases for the purpose of 
meeting wildlife conservation or recovery goals. Although dams have 
been managed to allow fish passage for spawning, to our knowledge, fish 
passage has not been facilitated specifically to allow movement of host 
fish for the benefit of freshwater mussels, nor would this be cost-
effective considering host fish for the Texas heelsplitter and 
Louisiana pigtoe are believed to be abundant. Nevertheless, reservoirs 
represent a permanent barrier to freshwater mussel dispersal. The 
overall impact of reservoirs is believed to be greater for the 
Louisiana pigtoe than for the Texas heelsplitter, which is able to 
persist in reservoir conditions although questions remain about their 
reproductive success in lake environments.
Direct Mortality
    Direct mortality includes any activity or event, whether human-
induced or natural, that results in the death of mussels within a 
localized area due to removal, crushing, burying, consumption, 
desiccation, or poisoning. Potential activities or events causing 
direct mortality include, but are not limited to, development projects 
(such as bridge replacement, stream channelization, and impoundment 
construction), undeveloped low-water crossings with vehicular traffic 
that intersect mussel beds, bank collapse, accidental release of 
hazardous materials, predation, vandalism, and collection (whether for 
scientific purposes or recreation) (USFWS 2022, pp. 57-58). The 
frequency, intensity, and magnitude of these impacts likely vary in 
time and by location and are difficult to quantify with any certainty 
other than to acknowledge that they exist and negatively affect mussel 
survival to some degree.
    Predation on freshwater mussels is a natural ecological 
interaction. Raccoons, feral hogs, muskrats, snapping turtles, and fish 
are known to prey upon mussels (East et al. 2013, p. 692; Walters and 
Ford 2013, p. 480; Kaller et al. 2007, p. 174; Neves and Odom 1989, p. 
939). Under natural conditions, the level of predation occurring is not 
likely to pose

[[Page 16786]]

a significant risk to any given population; however, during periods of 
low flow, terrestrial predators have increased access to portions of 
the river that are otherwise too deep under normal flow conditions, 
resulting in unnaturally high levels of predation that can decimate 
mussel populations. Predation during drought has been observed for the 
Texas heelsplitter on the Sabine River (Walters and Ford 2013, p. 479). 
Drought, low-flow conditions, and reductions in minimum summer base 
flows are predicted to occur more often and for longer periods due to 
the effects of future climate change; therefore, the tributaries and 
upper portions of focal areas for the Texas heelsplitter and Louisiana 
pigtoe are expected to experience increased predation pressure into the 
future (Lafontaine et al. 2019, entire).
    Additionally, certain mussel beds within some populations, due to 
ease of access, are vulnerable to over-collection and vandalism. These 
areas have well known and well documented mussel beds that are often 
sampled multiple times annually by various researchers for various 
scientific projects. Populations subjected to repeated sampling or 
monitoring may experience increased stress or higher rates of 
mortality. Mortality may also occur in areas where local fishing 
enthusiasts have been observed using freshwater mussels as bait. The 
risk of direct mortality from recreation or over-collection for 
scientific purposes are compounded by the additional stressors 
discussed in this section, which can influence mussel survival in a 
cumulative manner. Because collection of Louisiana pigote is localized 
and could affect populations, we carried this risk factor forward as a 
population-level threat. Service biologists recently hosted a meeting 
with State biologists, consultants, and academia who are involved in 
mussel research to discuss ongoing monitoring and scientific 
collections and to reduce the likelihood of over-harvesting mussels 
from any given population (USFWS 2018, p. 1), and we anticipate this 
collaboration among researchers will continue into the future with 
ongoing coordination and annual meetings.
Invasive Species
    Invasive species, such as Asian clam (Corbicula fluminea), zebra 
mussel (Dreissena polymorpha), feral hog (Sus scrofa), floating water 
hyacinth (Eichhornia crassipes), giant salvinia (Salvinia molesta), and 
hydrilla (Hydrilla verticillata), occur throughout the ranges of the 
Texas heelsplitter and Louisiana pigtoe and can negatively impact 
mussel survival. These impacts include predation (feral hog), habitat 
destruction or modification (feral hog, floating water hyacinth, giant 
salvinia, hydrilla), changes to water quality (feral hog, zebra 
mussel), increased resource competition (Asian clam, zebra mussel), or 
physical impairment (zebra mussel, hydrilla) (Kaller and Kelso 2006, 
pp. 172-174; Howells 2010a, p. 13; Howells 2010b, pp. 14-15).
    Although zebra mussel infestations occur in several Texas 
reservoirs, including Lewisville Lake and Lake Livingston, populations 
have not yet become established in nearby river habitats occupied by 
the Texas heelsplitter and Louisiana pigtoe (Ford et al. 2016, p. 47; 
Texas Parks and Wildlife Department (TPWD) 2019, entire; USGS 2019e, 
entire).
    Feral hogs occur throughout the range of both mussel species and 
are known to engage in a variety of activities that cause bank and 
streambed damage, contribute to erosion and increased sedimentation, 
and their presence appears to cause native mussel diversity and 
abundance to decrease through organic enrichment of the water and 
unfavorable changes to microbial community composition (Kaller et al. 
2007, p. 174; Howells 2010b, p. 10).
    Invasive macrophyte infestations of floating water hyacinth, 
hydrilla, and giant salvinia negatively impact native mussels and their 
host fish throughout the southern half of the ranges of the Texas 
heelsplitter and Louisiana pigtoe by creating hypoxic conditions 
through respiration and during decay (Karatayev and Burlakova 2007, p. 
298; USGS 2019b, entire; USGS 2019c, entire; USGS 2019d, entire). Dense 
mats of hydrilla can also impede native mussel movement during periods 
of fluctuating surface water levels, leaving them stranded as water 
levels recede.
Climate Change
    Climate change in the form of the change in timing and amount of 
precipitation and air temperature increase is occurring, and continued 
greenhouse gas emissions at or above current rates will cause further 
warming (Intergovernmental Panel on Climate Change (IPCC) 2021, pp. 1-
13-1-15). Warming in Texas is expected to be greatest in the summer 
(Maloney et al. 2014, p. 2236, figure 3), with the number of extremely 
hot days (high temperatures exceeding 35 [deg]C (95 [deg]F)) projected 
to double by around 2050 (Kinniburgh et al. 2015, p. 83). Changes in 
stream temperatures are expected to reflect changes in air temperature, 
at a rate of an approximately 0.6-0.8 [deg]C (33 [deg]F) increase in 
stream water temperature for every 1 [deg]C (33 [deg]F) increase in air 
temperature (Morrill et al. 2005, pp. 1-2, 15), with implications for 
temperature-dependent water quality parameters such as dissolved oxygen 
and ammonia toxicity. Given that freshwater mussels in Texas exist at 
or near the ecophysiological edge of climate and habitat gradients of 
freshwater mussel biogeography in North America, they 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 may seem relatively 
small (U.S. Global Change Research Program (USGCRP) 2017, p. 217), 
higher temperatures caused by anthropogenic activity will lead to 
increased soil water deficits because of higher rates of 
evapotranspiration. In turn, higher evapotranspiration rates will 
likely result in increasing drought severity in future climate 
scenarios, and the warming atmosphere is projected to continue across 
the United States (USGCRP 2017, p. 231). Even if precipitation and 
groundwater recharge remain at current levels, increased groundwater 
pumping and resulting 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. 3).
    Effects of climate change, such as changes to seasonal rainfall 
patterns, air temperature increases, and increases in drought frequency 
and intensity, have been shown to be occurring throughout the ranges of 
the Texas heelsplitter and Louisiana pigtoe (Andreadis and Lettenmaier 
2006, p. 3; USGCRP 2017, p. 188); 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 east Texas, with 
droughts like 2011 (the driest on record) becoming commonplace by the 
year 2100 (Mullens and McPherson 2017, pp. 3, 6). This trend of more 
frequent droughts is driven by increases in hot temperatures (e.g., 
daily maximum) and the number of days projected to be at or above 37.8 
[deg]C (100 [deg]F), which is set to ``increase in both consecutive 
events and the total number of days'' (Mullens and McPherson 2017, pp. 
14-15). Similarly, floods and extreme runoff are projected to become 
more common and severe in the 21st century as the frequency,

[[Page 16787]]

magnitude, and intensity of heavy precipitation events increase 
(Mullens and McPherson 2017, p. 20; USGCRP 2017, p. 224).
    In the analysis of the future condition for the Texas heelsplitter 
and Louisiana pigtoe, climate change is considered further under 
various plausible future scenarios, serving to exacerbate already 
deteriorating conditions through an increase of fine sediments, changes 
to water quality, loss of flowing water, and predation, among others.
Summary of Risk Factors for Texas Heelsplitter and Louisiana Pigtoe
    Our analysis of the past, current, and future influences on the 
needs of the Texas heelsplitter and Louisiana pigtoe for long-term 
viability revealed that there are four that pose the greatest impact on 
current condition and future viability: degradation of water quality, 
altered hydrology, substrate changes, and habitat fragmentation, all of 
which are exacerbated by climate change.

Conservation Efforts and Regulatory Mechanisms

    The level of interest among stakeholders, regulatory agencies, and 
partners to better understand the status, threats, and conservation of 
freshwater mussels in Texas has increased significantly since 2017, 
when the Service initiated reviews of several Texas mussel species for 
possible listing under the Act. This led to improved communication 
among interested parties and multiple partnerships seeking to conduct 
research and improve our understanding of the health and distribution 
of mussel populations across Texas, as well as increased efforts to 
protect and conserve known populations. Although there are currently no 
formal conservation agreements in place designed to specifically 
provide benefits to the Texas heelsplitter or Louisiana pigtoe, we are 
in discussions with multiple stakeholders who are interested in 
strengthening partnerships to conserve rare species, including several 
river authorities that are in the process of developing candidate 
conservation agreements with assurances (CCAAs). The CCAAs, if 
finalized, would implement voluntary conservation actions in river 
basins that would result in a net conservation benefit for the species. 
Additionally, several stakeholders have voluntarily funded research to 
ensure that we have the best available information upon which to base a 
listing decision, and we commend them for their efforts to improve the 
science of freshwater mussels in Texas. Interested stakeholders and 
potential future conservation partners include the Trinity River 
Authority, Lower Neches Valley Authority, North Texas Municipal Water 
District, Sabine River Authority, the Cities of Dallas and Fort Worth, 
Tarrant Regional Water District, Texas Department of Transportation, 
Texas Parks and Wildlife Department, U.S. Army Corps of Engineers, 
Texas Comptroller of Public Accounts, Texas A&M University, Texas State 
University, and others.
    With regard to silvicultural operations that occur on forested 
areas across the range of the species, we recognize that private timber 
companies routinely implement State-approved best management practices 
(BMPs; as reviewed by Cristan et al. 2018, entire). Adherence to these 
BMPs, such as citing river crossings away from sensitive areas and 
leaving intact habitat as buffers for areas adjacent to streams, 
broadly protects water quality by reducing timber harvest-related 
impacts, particularly erosion and sedimentation (as reviewed by Cristan 
et al. 2018; Warrington et al. 2017, entire; and Schilling et al. 2021, 
entire). However, it is important to recognize that while BMPs reduce 
timber harvest impacts, they do not eliminate impacts; therefore, 
sensitive species and their habitats may still be impacted even when 
BMP guidelines are followed.
    Some voluntary habitat restoration projects have been completed on 
private lands within the river basins currently known to be occupied by 
one or both species. These restoration projects include upland and 
riparian habitat enhancements coordinated by our State, Federal, and 
nongovernmental partners, as well as our Partners for Fish and Wildlife 
Program. There are also regulatory mechanisms in place to protect water 
quality and quantity, such as protections afforded by the Clean Water 
Act (33 U.S.C. 1251 et seq.), that are implemented by the States with 
oversight by the EPA. While these regulations are in place and provide 
some level of protection, population declines continue to be documented 
in some species of freshwater mussels, indicating that existing 
regulations may not be sufficient to prevent extinction.

Species Condition

    Here we discuss the current and future 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, which can alter stream characteristics 
such as an increase in stream temperatures, erosion, and the 
accumulation of fine sediments. The current condition of each species 
and population is based upon the cumulative effects of these factors. 
In the SSA report, for each species and population, we developed and 
assigned condition categories for three population factors (occupied 
stream length, abundance, reproduction/recruitment; see Species Needs, 
above) and three habitat factors (habitat structure/substrate, 
hydrological regime, and water quality; see Risk Factors for Texas 
Heelsplitter and Louisiana Pigtoe, above) that are important for the 
viability of each species. The summation of all six condition scores 
assigned to each factor were then used to determine the overall 
condition of each population: high (healthy), moderate (moderately 
healthy), low (unhealthy), or functionally extirpated/extirpated. All 
six factors were weighted equally in importance except abundance, which 
was viewed as the most relevant and direct measure of current 
biological condition; therefore, overall condition was capped by the 
abundance score such that no population's overall condition could 
exceed the abundance score. 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, 
unhealthy populations having the lowest probability of persistence 
(between 10 and 60 percent). Functionally extirpated populations (less 
than 10 percent) are not expected to persist over 20 years or are 
already extirpated.
Texas Heelsplitter
    There are five remaining Texas heelsplitter populations, occurring 
in three adjacent river basins (Neches, Sabine, and Trinity River 
basins) in east Texas and on the Sabine River to the western border of 
Louisiana. Historically, populations likely occurred throughout the 
entirety of each basin where connectivity was not an issue and 
conditions were suitable. Based on our analysis, three populations are 
considered to have a low current condition, and two populations are 
considered functionally extirpated/extirpated (see Table 1, below).
    Neches River Basin: There are two Texas heelsplitter populations in 
the

[[Page 16788]]

Neches River Basin, one in the Neches River/B.A. Steinhagen Reservoir 
and the other in the Lower Neches River; these populations are 
fragmented and isolated from each other by the dam that forms B.A. 
Steinhagen Reservoir. The Neches River/B.A. Steinhagen Reservoir 
population occurs in habitat on a fairly long reach (240.9 river mi 
(387.6 km)) of the Neches River that extends from just below Lake 
Palestine to B.A. Steinhagen Reservoir and includes the portion of 
mainstem Angelina River between B.A. Steinhagen and Sam Rayburn 
reservoirs. This population is characterized by low abundance and a 
lack of evidence of reproductive success, resulting in low recruitment 
of new individuals. Further, water quality in tributaries and segments 
of the occupied habitat is affected by a variety of point and non-point 
source pollution, and infrequent but substantial drawdowns of the B.A. 
Steinhagen Reservoir have resulted in direct mortality of Texas 
heelsplitters. The Lower Neches River population extends 74.2 river mi 
(119.4 km) downstream from Lake B.A. Steinhagen Reservoir's Town Bluff 
Dam to approximately 4.5 river mi (7.2 km) downstream of the Village 
Creek confluence. This population is also characterized by low 
abundance and lack of evidence of reproductive success, with subsequent 
low recruitment of new individuals. Further, hydrology and water 
quality in this reach are affected by water releases from the B.A. 
Steinhagen Reservoir. The Neches River/B.A. Steinhagen Reservoir 
population and the Lower Neches River population have a low overall 
current condition, resulting in low resiliency for both populations.
    Sabine River Basin: This Texas heelsplitter population occurs in a 
fairly long reach (245.8 river mi (395.5 km)) of the Sabine River 
Basin, that includes the Toledo Bend Reservoir, Sabine River upstream 
to Lake Tawakoni's Iron Bridge Dam, a portion of Lake Fork Creek 
upstream from its confluence with the Sabine River, and a portion of 
Patroon Bayou upstream from its confluence with Toledo Bend Reservoir. 
While the overall water quality, habitat structure/substrate, and 
occupied habitat reach length are in high condition, construction of 
Lake Tawakoni and Toledo Bend Reservoir have altered the natural 
hydrologic conditions through dam releases causing substrate scouring 
and elimination of habitat downstream. Due to lack of evidence of 
reproduction and recruitment, as well as extremely low abundance (CPUE 
= 0.14) based on 99 surveys since 2000, this population of Texas 
heelsplitter is considered functionally extirpated/extirpated.
    Trinity River Basin: There are two populations of the Texas 
heelsplitter in the Trinity River Basin, one within Grapevine Lake and 
another within the Trinity River/Lake Livingston, that are 
hydrologically isolated from one another by the dam that forms 
Grapevine Lake. The habitat structure/substrate rating for the 
Grapevine Lake population is in high condition, with stormwater runoff 
and the discharge of municipal wastewater and associated pollutants 
limiting water quality to moderate condition. Reservoir-related changes 
to natural flow regimes likewise limited the hydrology rating to 
moderate condition. However, with only two individuals found during 
population surveys, abundance is extremely low, this combined with the 
lack of juveniles and gravid females, the Grapevine Lake population is 
considered to be functionally extirpated. The Trinity River population 
is characterized by high current condition for the relatively large 
habitat reach length currently occupied, while habitat structure/
substrate is affected by unnaturally elevated base flows and is in 
moderate current condition. Large daily volumes of municipal wastewater 
discharge and associated pollutants are impacting water quality and 
hydrology, which are in low current condition. This population is also 
characterized by low abundance and lack of evidence of reproductive 
success, with subsequent low recruitment of new individuals. The 
Trinity River/Lake Livingston population has a low overall current 
condition and low resiliency.

   Table 1--Estimated Current Overall Condition of Texas Heelsplitter
                               Populations
                         [USFWS 2022, pp. 40-44]
------------------------------------------------------------------------
                                                        Overall current
           River basin                Population           condition
------------------------------------------------------------------------
Sabine..........................  Sabine River/       FE/E.\1\ \2\
                                   Toledo Bend.
Neches..........................  Neches River/B.A.   Low.\2\
                                   Steinhagen.        Low.\2\
                                  Lower Neches River
Trinity.........................  Grapevine Lake....  FE/E.\1\ \2\
                                  Trinity River/Lake  Low.\2\
                                   Livingston.
------------------------------------------------------------------------
\1\ FE/E = Functionally extirpated/extirpated.
\2\ Indicates representation areas where overall condition was capped by
  abundance.

    Redundancy describes the ability of a species to withstand and 
recover from catastrophic events. High redundancy is achieved through 
multiple populations that serve to spread risk, thereby reducing the 
impact that any one event might have in terms of overall loss to the 
species. Redundancy is characterized by having multiple healthy, 
resilient populations distributed across the range of the species. It 
can be measured by population number, resiliency, spatial extent, and 
degree of connectivity. Our analysis explored the influence of the 
number, distribution, and connectivity of populations on the species' 
ability to withstand catastrophic events.
    Within the identified representation areas (Neches, Sabine, and 
Trinity River basins), only the Neches and Trinity River basins 
currently have at least one known population (the Sabine River/Toledo 
Bend population in the Sabine River Basin and Grapevine Lake in the 
Trinity River Basin are considered functionally extirpated). The Neches 
River Basin currently has two populations (Neches River and Lower 
Neches River populations); however, these populations are 
hydrologically isolated, and therefore provide only minimal redundancy.
    Representation describes the ability of a species to adapt to 
changing environmental conditions over time. It is characterized by the 
breadth of genetic and environmental diversity within and among 
populations. Our analysis explores the relationship between the species 
life history and the influence of genetic and ecological diversity and 
the species ability to adapt to changing environmental conditions over 
time.
    We consider the Texas heelsplitter to have representation in the 
form of genetic, geographic, and ecological diversity in the three 
currently occupied river basins. Because there are no freshwater 
connections between the three basins, we treated each river basin as 
separate areas of representation.
Louisiana Pigtoe
    Overall, there are 13 remaining populations of Louisiana pigtoe in 
multiple river drainages throughout portions of east Texas (Big 
Cypress-Sulphur, Neches-Angelina, Sabine, and San Jacinto river 
basins), Louisiana (Calcasieu, Sabine, and Pearl river systems), west 
Mississippi (Pearl River), southeast Oklahoma (Little River), and 
southwest Arkansas (Cossatot, Saline, Rolling Fork, and Little rivers). 
Because reported populations from the Ouachita River system in Arkansas 
were determined to be phylogenetically distinct (a separate species) 
from Louisiana pigtoe, they were not considered in the SSA. In 2019, an 
additional population was discovered within the Lower Neches Valley 
River

[[Page 16789]]

Authority canal system in Beaumont, Texas (Bio-West 2021, p. 1). 
Because this population occupies artificially maintained habitat that 
may not persist without active operational management by the Lower 
Neches Valley River Authority, it was not considered for analysis in 
the SSA.
    Historically, the Louisiana pigtoe likely occurred throughout each 
basin wherever conditions were suitable and connectivity was not an 
issue, with populations connected by fish migration; however, due 
primarily to impoundments, the populations are currently isolated from 
one another, and repopulation of functionally extirpated/extirpated 
locations is unlikely to occur without human assistance. Two 
populations are currently considered to be in high condition, four 
populations are in moderate condition, five populations are in low 
condition, and two populations are considered functionally extirpated/
extirpated (see Table 2, below).
    Big Cypress-Sulphur Basin: Although Louisiana pigtoes have not been 
genetically confirmed and observations may be misidentified as Wabash 
pigtoe (Fusconaia flava), past surveys indicated Louisiana pigtoe 
presence (Randklev 2018, entire) in this basin. Therefore, we included 
this population in this assessment. The Louisiana pigtoe population in 
Big Cypress Bayou includes approximately 32.0 river mi (51.5 km) of Big 
Cypress Bayou and Little Cypress Bayou upstream of their confluence. 
This population is characterized by moderate condition for occupied 
habitat stream length, abundance, habitat structure/substrate, 
hydrology, and water quality; the habitat factors are influenced by a 
variety of anthropogenic activities that vary by watershed, including 
stormwater runoff and discharges from multiple wastewater treatments 
plants. However, there has been a lack of reported juveniles or gravid 
females, so this population is in low condition for reproduction and 
recruitment.
    Calcasieu River Basin: Louisiana pigtoe has a single population in 
the Calcasieu-Mermentau Basin that occurs along an approximately 134-
river-mi (216-km) section of hydrologically connected portions of the 
mainstem Calcasieu River, and the Whisky Chitto and Tenmile creeks 
located in Allen, Rapides, and Vernon parishes, Louisiana. This 
population is characterized as being in high condition for occupied 
habitat reach length and habitat structure/substrate, while hydrology 
and water quality are in moderate condition due to fluctuations in flow 
rates and municipal wastewater effluent discharges, among other sources 
of pollution. However, abundance, reproduction, and recruitment are in 
low condition, which corresponds to low resiliency.
    Neches River Basin: The Neches River Basin in Texas has three 
populations of Louisiana pigtoe, one each in the Angelina (above Sam 
Rayburn Reservoir), Neches (above B.A. Steinhagen Reservoir), and Lower 
Neches rivers (below B.A. Steinhagen Reservoir). These three 
populations combined extend over 400 river mi (644 km) in a basin that 
many experts believe contains some of the best remaining habitat and 
most diverse populations of freshwater mussels in Texas. The Neches 
River and Lower Neches River populations are hydrologically isolated 
from each other by the Town Bluff Dam that forms B.A. Steinhagen 
Reservoir, and the Angelina River population is isolated from the 
Neches River population by Sam Rayburn Dam and Reservoir. The Neches 
River population's current condition is characterized as high condition 
for the occupied habitat reach length (203 river mi (326.7 km)), 
abundance, habitat structure/substrate, and hydrology, and moderate 
condition for reproduction/recruitment and water quality. The Lower 
Neches River population is characterized by high current condition for 
occupied habitat reach length (160.4 river mi (258.1 km)) and habitat 
structure/substrate, and a moderate current condition for hydrology, 
water quality, and reproduction/recruitment due to the impacts of 
fluctuating stream flows, pollution loading from point and non-point 
sources, and few reports of gravid females or juvenile mussels. In 
addition, few individuals have been observed, resulting in a low 
current condition for population abundance. The Angelina River 
population is in high condition for occupied habitat reach length (53.2 
river mi (85.6 km)), habitat structure/substrate, and hydrology; 
however, water quality impacts such as elevated bacteria, fecal 
coliform, and ammonia resulted in a moderate current condition for 
water quality. Like the Lower Neches River population, due to the few 
numbers of individuals observed and a lack of juvenile or gravid female 
presence, abundance and reproduction/recruitment are in low condition 
for the Angelina River population. The Neches River population has a 
high overall current condition, and the Lower Neches River and Angelina 
River populations have a low overall current condition (primarily due 
to being capped by low abundance).
    Pearl River Basin: The Pearl River Basin in Louisiana and 
Mississippi has a single population of the Louisiana pigtoe within the 
main stem that extends approximately 280 river mi (450 km) below Ross 
Barnett Dam near Jackson to Picayune, Mississippi (upstream of 
Interstate 59). A new impoundment proposed by the Rankin-Hinds Pearl 
River Flood and Drainage Control District, located 9 mi (14.5 km) 
downstream of Ross Barnett Reservoir, intended for flood control, is 
still under review. For the Pearl River population, we determined that 
occupied habitat reach length is in high condition, and habitat 
structure/substrate, hydrology, and water quality are in moderate 
condition due to erratic flows and pollutants from urban areas and 
industry wastewater discharge. Because few individuals have been 
reported and there is a lack of juvenile or gravid female presence, 
abundance and reproduction/recruitment are in low condition. The Pearl 
River population has an estimated overall low current condition and low 
resiliency.
    Red River Basin: The Red River Basin contains four distinct 
populations of the Louisiana pigtoe that extend along 88.3 river mi 
(142.1 km) within the Little River drainage in Arkansas and Oklahoma, 
including populations in the Cossatot River, Little River/Rolling Fork, 
Lower Little River, and Saline River. Millwood Lake, located in 
southwest Arkansas, hydrologically separates the Cossatot River, Saline 
River, and Little River/Rolling Fork populations from the Lower Little 
River population. The current condition evaluation for the Cossatot 
River population determined that abundance, reproduction/recruitment, 
and habitat structure/substrate are in high condition, and occupied 
habitat reach length, hydrology, and water quality are in moderate 
condition due to fluctuations of stream flows from Gillham Lake, as 
well as pollutant discharges from agriculture and other sources. No 
habitat or population factors are determined to be in low condition. 
The Little River/Rolling Fork population's current condition evaluation 
determined occupied habitat reach length and reproduction/recruitment 
are in high condition. All other population and habitat factors are in 
moderate condition due to lower abundance, fluctuations in instream 
flow (which affect benthic habitat, substrate, and stream hydrology), 
and increased levels of zinc, lead, and salinity (among other 
pollutants), leading to moderate water quality. The Saline River 
population's current condition evaluation found

[[Page 16790]]

occupied habitat reach length, abundance, hydrology, and water quality 
in moderate condition caused by prolonged high water levels and low 
levels of dissolved oxygen. Due to the lack of evidence of reproductive 
success and subsequent recruitment of new individuals, and altered flow 
conditions downstream of Dierks Lake, reproduction/recruitment and 
habitat structure/substrate are in low condition. The Lower Little 
River population's current condition evaluation determined that 
reproduction/recruitment and all habitat factors are in low condition 
primarily because of its short reach length (8.5 river mi (14.16 km)), 
altered flow regime, and paucity of survey data. This population is 
located downstream of Millwood Lake and Dam, a flood control reservoir, 
and is subject to altered hydrology that further impacts habitat 
structure and substrates during flood events. Agricultural runoff 
associated with the lower section of this reach impacts water quality. 
Due to the extremely low numbers of individuals observed (abundance), 
this population is considered functionally extirpated/extirpated. In 
summary, the Cossatot River population has a high overall current 
condition and high resiliency, the Little River/Rolling Fork and Saline 
River populations have a moderate overall current condition and 
moderate resiliency, and the Lower Little River population is 
considered functionally extirpated/extirpated.
    Sabine River: There are two known populations of the Louisiana 
pigtoe within the Sabine River, one located along 87 river mi (140 km) 
between Hawkins and Tatum, Texas, and a second population within a 9-
river-mi (15-km) segment of Bayou Anacoco in Louisiana. These 
populations are hydrologically separated by Toledo Bend Dam and 
Reservoir. The Sabine River population's current condition evaluation 
determined that occupied habitat reach length and habitat structure/
substrate are in high condition. Dam releases from Lake Tawakoni and 
Toledo Bend Reservoir, wastewater releases, and water quality 
degradation (including elevated levels of bacteria) are primary causes 
for moderate current conditions for hydrology and water quality. Due to 
an extremely low number of individuals detected during surveys, and the 
lack of juveniles or gravid females observed, abundance and 
reproduction/recruitment are in low condition, and this population is 
considered functionally extirpated/extirpated. The Bayou Anacoco 
population's current condition evaluation found habitat structure/
substrate is high condition, and abundance, hydrology, and water 
quality are in moderate condition. However, the occupied habitat reach 
length and reproduction/recruitment are in low condition due to the 
distribution of observed individuals and lack of reported juveniles or 
gravid females. The Bayou Anacoco population is in moderate current 
overall condition and has moderate resiliency.
    East Fork San Jacinto River: There is one known population of 
Louisiana pigtoe that occurs within a short (1.3-river-mi (2-km)) 
segment of the East Fork San Jacinto River near Plum Grove, Texas. The 
population's current condition evaluation determined that hydrology and 
water quality are in moderate condition, whereas sand and gravel mining 
are affecting the habitat structure/substrate, which is in low 
condition. Due to a low number of individuals detected and lack of 
juveniles or gravid females observed, population abundance and 
reproduction/recruitment are in low condition. The East Fork San 
Jacinto River population is determined to be in overall low condition 
and has low resiliency.

 Table 2--Estimated Current Overall Condition of Known Louisiana Pigtoe
                               Populations
                         [USFWS 2022, pp. 34-40]
------------------------------------------------------------------------
                                                        Overall current
           River basin                Population           condition
------------------------------------------------------------------------
Red.............................  Little River/       Moderate.
                                   Rolling Fork.      High.
                                  Cossatot River....  Moderate.
                                  Saline River......  FE/E. \1\ \2\
                                  Lower Little River
Big Cypress-Sulphur.............  Big Cypress Bayou.  Moderate.
Calcasieu-Mermentau.............  Calcasieu River...  Low. \2\
Pearl...........................  Pearl River.......  Low. \2\
Sabine..........................  Sabine River......  FE/E. \1\ \2\
                                  Bayou Anacoco.....  Moderate.
Neches..........................  Angelina River....  Low. \2\
                                  Neches River......  High.
                                  Lower Neches River  Low.\2\
San Jacinto.....................  East Fork San       Low.
                                   Jacinto River.
------------------------------------------------------------------------
\1\ FE/E = Functionally extirpated/extirpated.
\2\ Indicates representation areas where overall condition was capped by
  abundance.

    Within identified representation areas, the Big Cypress-Sulphur, 
Calcasieu-Mermentau, Pearl, and San Jacinto River basins each have only 
one known current population, and therefore lack redundancy should 
catastrophic events occur that cause extirpation of one or a few 
populations. The Sabine River Basin has two separate populations 
(Sabine River and Bayou Anacoco populations) but lacks redundancy due 
to the Sabine River population being functionally extirpated. The 
Neches and Red River basins each currently have three known populations 
(the Lower Little River population in the Red River Basin is considered 
functionally extirpated), however each population is hydrologically 
isolated within their respective river basins and are, therefore, 
considered to provide only limited redundancy.
    We consider Louisiana pigtoe to have representation in the form of 
genetic, ecological, and geographical diversity between each of seven 
river basins: Big Cypress-Sulphur, Calcasieu-Mermentau, Neches, Pearl, 
Red, Sabine, and San Jacinto. Because there are no un-impounded, 
freshwater connections that allow movement between the seven basins, 
each river was considered a separate area of representation.

Future Conditions

    As part of the SSA, we developed multiple future condition 
scenarios to capture the range of uncertainties

[[Page 16791]]

regarding future threats and the projected responses by the Texas 
heelsplitter and Louisiana pigtoe. Our scenarios included a status quo 
scenario, which incorporated the current risk factors continuing on the 
same trajectory that they are on now. We also evaluated two future 
scenarios that incorporated varying levels of increasing risk factors 
with elevated negative effects on Texas heelsplitter and Louisiana 
pigtoe populations. However, because we determined that the current 
condition of the Texas heelsplitter is consistent with an endangered 
species (see Texas Heelsplitter: Determination of Status, below), we 
are not presenting the results of the future scenarios in this proposed 
rule. Please refer to the SSA report (Service 2022) for the full 
analysis of future scenarios.
    We forecasted the Louisiana pigtoe's responses to two plausible 
future scenarios of environmental conditions projected across the next 
10, 25, and 50 years. Ten years represents one to two generations of 
mussels, assuming an average reproductive life span of five to 10 
years. Twenty-five years similarly represents at least two to four 
mussel generations and 50 years represents at least five or more 
generations of mussels. The scenarios project the threats into the 
future and consider the impacts those threats could have on the 
viability of the Louisiana pigtoe. We apply the concepts of resiliency, 
redundancy, and representation to the future scenarios to describe 
possible future conditions of the Louisiana pigtoe. The scenarios 
described in the SSA report represent only two possible future 
conditions. Uncertainty is inherent in any projection of future 
condition, so we must consider plausible scenarios to make our 
determinations. When assessing the future, viability is not a specific 
state, but rather a continuous measure of the likelihood that the 
species will sustain populations over time.
    We included climate change in our future scenarios as a factor that 
would add to the negative impacts of the primary threats on the 
species' habitat. Climate change is expected to alter the natural flow 
regime through increased drought and flooding worsening desiccation, 
scour, and sedimentation. Global climate models project changes in 
global temperature and other associated climatic changes based on 
potential future scenarios of greenhouse gas concentrations in the 
atmosphere (i.e., Representative Concentration Pathways, or RCPs). RCP 
4.5 assumes major near-future cuts to carbon dioxide emissions, and RCP 
8.5 assumes that current emissions practices continue with no 
significant change (Terando et al. 2020, p. 10). Thus, these RCPs 
represent conditions in the upper and lower ends of the range of what 
can reasonably be expected for the future effects of climate change 
(Terando et al. 2020, p. 17).
    Scenario 1 assesses the species' responses to moderate increases in 
stressors influencing Louisiana pigtoe populations. Scenario 1 is based 
on RCP 4.5 emission trajectory and associated model projections, and 
represents medium-term increases in emissions followed by a decline 
through the rest of the century. Scenario 2 assesses the species' 
responses to severe increases in stressors and is based on RCP 8.5 
projections. Scenario 2 also includes anthropogenic actions, such as 
the construction of new reservoirs, wastewater treatment plants, and 
other currently proposed projects, and manifests as a future where the 
hydrological conditions of many of the rivers and streams currently 
occupied by Louisiana pigtoe are altered such that base flows are 
diminished, floods are more severe if not more frequent, and mussels 
and their habitats are adversely affected through degradation of water 
quality and quantity. These altered hydrological conditions are 
primarily caused by a combination of increasing anthropogenic stressors 
and climate change. Due to a lack of resolution of the available data, 
we were unable to distinguish any meaningful difference between a 
moderate increase in stressors and a moderate decrease in stressors. As 
a result, we limited the future forecasts to these two scenarios, which 
we projected over a 50-year period. We restricted our evaluation to 50 
years primarily due to limitations projecting non-modeled, extrapolated 
future conditions for water quality, road density, and habitat 
fragmentation. Fifty years encompasses about 5 generations of the 
Louisiana pigtoe; additionally, projected human population growth and 
the limitations of existing resources are expected to increase and 
interact with climate effects to exacerbate the effects of drought 
which is likely to impact water quality and quantity (i.e., the ability 
to provide the minimum flow needed by the Louisiana pigtoe). A full 
description of the future scenarios and our methods is available in the 
SSA report (USFWS 2022, pp. 63-73).
    Under Scenario 1, populations of the Louisiana pigtoe decline in 
resiliency, redundancy, and representation over time as conditions 
moderately decline from current conditions. One population will remain 
in moderate condition, seven in low condition, and five functionally 
extirpated in 50 years. This species will lose two areas of 
representation, diminishing the overall adaptive capacity to future 
environmental change in the next 50 years (see Table 3).

                             Table 3--Future Condition of Louisiana Pigtoe Populations With a Moderate Increase in Stressors
                                                                      [Scenario 1]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         Scenario 1 future condition
              Species                      River basin             Population       --------------------------------------------------------------------
                                                                                            10 years               25 years               50 years
--------------------------------------------------------------------------------------------------------------------------------------------------------
Louisiana Pigtoe...................  Red Little River/       Moderate..............  Low..................  Low..................
                                      Rolling Fork.          High..................  High.................  Moderate.............
                                     Cossatot River........  Moderate..............  Moderate.............  Low..................
                                     Saline River..........  FE/E \1\..............  FE/E \1\.............  FE/E.\1\.............
                                     Lower Little River....
                                     Big Cypress-Sulphur...  Big Cypress Bayou.....  Moderate.............  Moderate.............  Low.
                                     Calcasieu.............  Calcasieu River.......  Low..................  Low..................  FE/E.\1\
                                     Pearl.................  Pearl River...........  Low..................  Low..................  Low.
                                     Sabine................  Sabine River..........  FE/E \1\.............  FE/E \1\.............  FE/E.\1\
                                                             Bayou Anacoco.........  Low..................  Moderate.............  Low.
                                     Neches................  Angelina River........  Low..................  Low..................  FE/E.\1\
                                                             Neches River..........  High.................  Low..................  Low.
                                                             Lower Neches River....  Low..................  Low..................  Low.

[[Page 16792]]

 
                                     San Jacinto...........  East Fork San Jacinto   Low..................  Low..................  FE/E. \1\
                                                              River.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ FE/E = Functionally extirpated/extirpated.

    Under Scenario 2, populations of the Louisiana pigtoe further 
decline in resiliency, redundancy, and representation over time as the 
effects of climate change impact populations through extremely low 
stream flows, severe increases in sedimentation, reductions in water 
quality, and an increase in potential for desiccation of habitat. Eight 
populations of Louisiana pigtoe are expected to become either 
functionally extirpated or extirpated within 50 years, with the 
remaining five populations in low condition. The Louisiana pigtoe is 
projected to lose four of the seven current representation areas in 50 
years, with eight populations remaining or becoming extirpated; 
therefore, the adaptive capacity of this species is projected to be 
severely reduced in the future (see Table 4).

                              Table 4--Future Condition of Louisiana Pigtoe Populations With a Severe Increase in Stressors
                                                                      [Scenario 2]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         Scenario 2 future condition
              Species                      River basin             Population       --------------------------------------------------------------------
                                                                                            10 years               25 years               50 years
--------------------------------------------------------------------------------------------------------------------------------------------------------
Louisiana Pigtoe...................  Red...................  Little River/Rolling    Moderate.............  Low..................  Low.
                                                              Fork.                  High.................  High.................  Low.
                                                             Cossatot River........  Moderate.............  Low..................  Low.
                                                             Saline River..........  FE/E \1\.............  FE/E \1\.............  FE/E.\1\
                                                             Lower Little River....
                                     Big Cypress-Sulphur...  Big Cypress Bayou.....  Moderate.............  Moderate.............  Low.
                                     Calcasieu-Mermentau...  Calcasieu River.......  Low..................  Low..................  FE/E.\1\
                                     Pearl.................  Pearl River...........  Low..................  Low..................  FE/E.\1\
                                     Sabine................  Sabine River..........  FE/E \1\.............  FE/E \1\.............  FE/E.\1\
                                                             Bayou Anacoco.........  Low..................  Moderate.............  FE/E.\1\
                                     Neches................  Angelina River........  Low..................  Low..................  FE/E.\1\
                                                             Neches River..........  High.................  Low..................  Low
                                                             Lower Neches River....  Low..................  Low..................  FE/E.\1\
                                     San Jacinto...........  East Fork San Jacinto   Low..................  FE/E \1\.............  FE/E.\1\
                                                              River.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ FE/E = Functionally extirpated/extirpated.

    We note that, by using the SSA framework to guide our analysis of 
the scientific information documented in 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. To assess the current and 
future condition of the species, we undertake an iterative analysis 
that encompasses and incorporates the threats individually and then 
accumulates and evaluates the effects of all the factors that may be 
influencing the species, including threats and conservation efforts. 
Water quality degradation, altered hydrology, changes to habitat 
structure/substrate, habitat fragmentation, invasive species, climate 
change, and collecting are all factors that influence or could 
influence the viability of these two freshwater mussel species. These 
factors also have the potential to act cumulatively to impact Texas 
heelsplitter and Louisiana pigtoe viability and their cumulative 
impacts were considered in our characterization of the species' current 
and future condition in the SSA. 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 an endangered species or a 
threatened species. The Act defines an ``endangered species'' as a 
species in danger of extinction throughout all or a significant portion 
of its range, and a ``threatened species'' as a species 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 an endangered 
species or a 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 Texas heelsplitter and Louisiana 
pigtoe and

[[Page 16793]]

assessing the cumulative effect of the threats under the Act's section 
4(a)(1) factors, we found that both species of freshwater 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 six 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): 
impairment of water quality, altered hydrology, the accumulation of 
fine sediments, and habitat fragmentation, all of which are exacerbated 
by the effects of climate change (Factor E). Predation (Factor C) and 
collection (Factor B), as well as other natural or human-induced 
events/activities that result in direct mortality, are also affecting 
those populations already experiencing low stream flow, and reservoirs 
and instream barriers to fish movement (Factor E) limit dispersal and 
prevent recolonization after stochastic events.
    Populations of the Texas heelsplitter and Louisiana pigtoe are 
faced with a myriad of stressors from natural and anthropogenic sources 
that pose a risk to their survival in both large and small river 
segments. Climate change has the noteworthy distinction of being able 
to directly or indirectly exacerbate the most relevant stressors to 
freshwater mussels wherever they occur. Climate projections suggest 
persistent droughts over the continental United States that are longer, 
cover more area, and are more intense than what has been experienced in 
the 20th century (APA 2019, p. 4; Terando et al. 2018, p. 786; Wehner 
et al. 2017, p. 237). Humans are likely to respond to climate change in 
predictable ways to meet their needs, such as increased groundwater 
pumping and surface water diversions, and increased use of reverse 
osmosis to treat sources of water that are of poor quality (thereby 
generating increasing volumes of wastewater). These activities will 
increase overall demand for freshwater resources at a time when those 
very resources are strained and less abundant (reviewed in Banner et 
al. 2010, entire). We expect climate change impacts to occur throughout 
the range of both the Texas heelsplitter and the Louisiana pigtoe.
    The threats to the species, acting alone or in combination with 
each other and climate change, could result in the extirpation of 
additional mussel populations, further reducing the overall redundancy 
and representation of the Texas heelsplitter and Louisiana pigtoe. 
Historically, each species, bolstered by large, interconnected 
populations (i.e., with meta-population dynamics), would have been more 
resilient to stochastic events such as drought, excessive 
sedimentation, and scouring floods. As locations became extirpated by 
catastrophic events, they could be recolonized over time by dispersal 
from nearby surviving populations, facilitated by movements of host 
fish. This connectivity across potential habitats made for highly 
resilient species overall, as evidenced by the long and successful 
evolutionary history of freshwater mussels as a taxonomic group, and in 
North America in particular. However, under current conditions, 
restoration of that connectivity on a regional scale is not feasible. 
Because of these current conditions, the viability of the Texas 
heelsplitter and Louisiana pigtoe now primarily depends on maintaining 
the remaining isolated populations and potentially restoring new 
populations where feasible.

Texas Heelsplitter: Status Throughout All of Its Range

    The Texas heelsplitter has declined significantly in overall 
distribution and abundance over the past 100 or more years. Most known 
populations of the Texas heelsplitter are isolated and currently exist 
in very low numbers (low abundance), have limited evidence of 
recruitment, and are believed to occupy much less habitat than in the 
past (range contraction). Of the five remaining populations of Texas 
heelsplitter, three are small in abundance and have low resiliency, and 
two are considered functionally extirpated/extirpated. While the three 
low resiliency populations (Neches River/B.A. Steinhagen Reservoir, 
Lower Neches River, and Trinity River/Lake Livingston) have habitat in 
high or moderate current condition, all three have very little evidence 
of reproduction and are therefore likely to decline due to a lack of 
young individuals joining the population as the population ages. Low 
abundance, combined with the lack of evidence of reproduction and 
recruitment, results in populations with very little population 
resiliency. Overall, these low levels of resiliency, redundancy, and 
representation currently result in the Texas heelsplitter having a high 
risk of extinction.
    Our analysis of the species' current condition, as well as the 
conservation efforts discussed above, show that the Texas heelsplitter 
is in danger of extinction throughout all of its range 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 the Texas heelsplitter 
because its current range is already contracted, all populations are 
fragmented and isolated from one another, the threats are occurring 
across the entire range of this species, and the species currently 
exhibits low resiliency, redundancy, and representation. Because these 
conditions place the species already in danger of extinction throughout 
its range, a threatened status is not appropriate.

Texas Heelsplitter: Status Throughout a Significant Portion of Its 
Range

    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 Texas heelsplitter is in danger 
of extinction throughout all of its range and accordingly did not 
undertake an analysis of any significant portion of its range. Because 
the Texas heelsplitter warrants listing as endangered throughout all of 
its range, our determination does not conflict with the decision in 
Center for Biological Diversity v. Everson, 2020 WL 437289 (D.D.C. Jan. 
28, 2020), because that decision related to significant portion of the 
range analyses for species that warrant listing as threatened, not 
endangered, throughout all of their range.

Texas Heelsplitter: Determination of Status

    Our review of the best available scientific and commercial 
information indicates that the Texas heelsplitter meets the Act's 
definition of an endangered species. Therefore, we propose to list the 
Texas heelsplitter as an endangered species in accordance with sections 
3(6) and 4(a)(1) of the Act.

Louisiana Pigtoe: Status Throughout All of Its Range

    Many Louisiana pigtoe populations are relatively abundant, but 
populations are isolated from one another; therefore, the species is 
unable to recolonize following stochastic events that may reduce or 
eliminate populations. Additionally, many populations occur in degraded 
habitats. Although some

[[Page 16794]]

conservation efforts are underway, they are not sufficient to prevent 
the decline of the species. Thirteen populations of Louisiana pigtoe 
remain. Two populations are in high condition, four in moderate 
condition, five are in low condition, and two are functionally 
extirpated/extirpated. The Red River Basin has four populations, and 
only one is in high condition (Cossatot River), two are in moderate 
overall condition, and one (Lower Little River) is functionally 
extirpated/extirpated. The Neches River is the only other population 
with a high overall current condition. Only two populations, Little 
River/Rolling Fork and Cossatot River (both within the Red River 
Basin), have strong evidence of reproduction and recruitment as 
indicated by presence of fish hosts, juveniles, and gravid females; two 
(Neches and Lower Neches rivers) have moderate evidence of reproduction 
and recruitment; the remaining nine populations have low evidence of 
reproduction and recruitment. Two populations have high abundance 
(Cossatot and Neches rivers) four populations have moderate abundance 
(Little River/Rolling Rock, Saline River, Big Cypress Bayou, and Bayou 
Anacoco), and five populations have extremely low abundance (Calcasieu, 
Pearl, Angelina, Lower Neches, and East Fork San Jacinto rivers), and 
population abundance is too low to support resiliency of two 
populations (Lower Little River (tributary to the Red River) and Sabine 
River), which are functionally extirpated/extirpated
    We considered whether the Louisiana pigtoe is presently in danger 
of extinction throughout all of its range 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 in high current condition, and four are in 
moderate current condition; they 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.
    In the future, 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. Given the likelihood of climate change 
and other anthropogenic effects in the foreseeable future, within 50 
years we estimate at least five populations will become (or remain) 
functionally extirpated/extirpated, seven will be in low condition, and 
one population will be in moderate condition. In the future, we 
anticipate that the Louisiana pigtoe will have reduced viability, with 
no highly resilient populations and limited representation and 
redundancy.
    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 50 years throughout all of its range. Fifty 
years encompasses about 5 generations of the Louisiana pigtoe; 
additionally, projected human population growth and the limitations of 
existing resources are expected to increase and interact with climate 
effects to exacerbate the effects of drought on surface water resources 
throughout all of its range. These effects are likely to impact the 
ability to provide the minimum flow needed by the Louisiana pigtoe. 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 50 years.
    After evaluating threats to the species and assessing the 
cumulative effect of the threats under the Act's section 4(a)(1) 
factors, we find that the Louisiana pigtoe populations will continue to 
decline over the next 50 years so that this species is likely to become 
in danger of extinction throughout all 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.
    Thus, after assessing the best available information, we determine 
that the Louisiana pigtoe 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.

Louisiana Pigtoe: Status Throughout a Significant Portion of Its Range

    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. The court in Center for Biological Diversity v. Everson, 
2020 WL 437289 (D.D.C. Jan. 28, 2020) (Everson), vacated the aspect of 
the Final Policy on Interpretation of the Phrase ``Significant Portion 
of Its Range'' in the Endangered Species Act's Definitions of 
``Endangered Species'' and ``Threatened Species'' (Final Policy) (79 FR 
37578; July 1, 2014) that provided that the Service does 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 Everson, 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 Louisiana pigtoe, 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 may be endangered.
    For the Louisiana pigtoe, we consider abundance to be the most 
direct measure of the health and status of the species (see Species 
Condition, above). Measures like water quality and hydrology may rank 
moderate or high, indicating higher quality habitat--but that does not 
necessarily indicate the presence of Louisiana pigtoe, only presence of 
suitable habitat. All six factors were weighted equally in importance 
except abundance, which was viewed as the most relevant and direct 
measure of current biological condition; therefore, overall condition 
was capped by the abundance score such that no population's overall 
condition could exceed the abundance score. By capping abundance, we 
ensured that the overall current condition score is based on species-
specific information. There are five populations that are considered to 
be in low overall current condition (with between 3-25 individuals 
found per population survey) and two that are considered functionally 
extirpated/extirpated (with less than 3 individuals found per 
population survey). In addition to low abundance, there was a lack of 
evidence of reproduction in 9 of the 13 populations; these two 
population factors are similar in scope, scale, and distribution across 
the range of the species (See Reproduction/

[[Page 16795]]

Recruitment in Species Needs above). We then considered whether these 
populations that are at higher risk of extirpation are geographically 
concentrated in any portion of the species' range at a biologically 
meaningful scale.
    We examined the range of Louisiana pigtoe for biologically 
meaningful portions that may be at higher risk of extirpation, as 
reflected by current population resiliency. The range of Louisiana 
pigtoe is relatively large, and populations are distributed in varying 
conditions across the range. Therefore, we examined the range based on 
accepted mussel faunal provinces (i.e., Haag 2010, p. 18), which 
reflect phylogenetic relationships as well as physiogeographical 
differences in stream habitat. The faunal provinces germane to the 
range of the Louisiana pigtoe are Interior Highlands (includes the 
Little River and tributaries), Mississippi Embayment (includes Big 
Cypress Bayou), Sabine-Trinity (includes Upper Calcasieu, Sabine, 
Angelina, Neches, and East Fork San Jacinto Rivers, and Bayou Anacoco), 
and Pontchartrain-Pearl-Pascagoula (includes Pearl River). Of these 
faunal provinces, the Interior Highlands, Sabine-Trinity, and 
Pontchartrain-Pearl-Pascagoula faunal provinces contain populations in 
low condition or that are functionally extirpated and therefore are at 
higher risk of extirpation.
    The Interior Highlands faunal province is characterized by upland 
streams in the Ozark and Ouachita mountains. This province has numerous 
endemic aquatic species of both fish and freshwater mussels, due to the 
isolation of the river systems within the province from each other and 
from other upland river systems (Haag 2012, pp. 82-83). In this faunal 
province, the Lower Little River is functionally extirpated, with the 
remaining populations in moderate (Little River and Saline River) or 
high (Cossatot River) condition. While the populations in this faunal 
province are subject to threats such as erratic flows capable of 
causing bed movement or dislocation of mussels, increased 
sedimentation, altered water chemistry (e.g., low temperatures), and 
decreased water quality due to higher pollutant loads from urban areas 
and industrial wastewater discharges, the threats are primarily 
occurring in the future. Under a moderate increase in stressors based 
on the lower greenhouse gas emissions trajectory (RCP 4.5), model 
projections expect an increase in global mean surface temperatures that 
will alter precipitation events resulting in drought and flooding in 
the next 25-50 years, this combined with future human demand for water 
resources indicate an overall decline in populations in the future. 
Louisiana pigtoe within the Interior Highlands faunal province are not 
currently in danger of extinction; therefore, they do not have a 
different status from the remainder of the species' range.
    The Sabine-Trinity faunal province is located in the central Gulf 
Coast of Texas, and characterized by lowland streams and rivers, with 
lentic and wetland habitats bordering the main channels (Haag 2012, pp. 
86-87). In this faunal province, the Upper Calcasieu River, Angelina 
River, Lower Neches River, and the East Fork San Jacinto River are in 
low condition, the Sabine River is functionally extirpated, with the 
remaining populations in moderate (Big Cypress Bayou) or high condition 
(Neches River). While the populations in this faunal province are being 
affected by impoundments resulting in threats such as excessive 
sedimentation and water quality degradation, as well as ongoing 
agricultural activities, groundwater withdrawals, and surface water 
diversions, these threats are primarily occurring in the future. Under 
a moderate increase in stressors based on the lower greenhouse gas 
emissions trajectory (RCP 4.5), model projections expect an increase in 
global mean surface temperatures that will alter precipitation events 
resulting in more extreme drought and flooding conditions that reduces 
water quality, mobilizes substrates, eroded habitat or deposits 
sentiments on Louisiana pigtoe populations in the next 25-50 years. The 
Sabine-Trinity faunal province are not currently in danger of 
extinction; therefore, they do not have a different status from the 
remainder of the species' range.
    The Pontchartrain-Pearl-Pascagoula faunal province lies entirely 
within the Coastal Plain and is characterized by lowland streams filled 
with sandy and fine sediments, with lentic and wetland habitats 
alongside the main stream channels (Haag 2012, p. 87.). This province 
has numerous endemic aquatic species of both fish and freshwater 
mussels, the majority of which are shared with the Mobile Basin 
province (Haag 2012, pp. 87-89), and includes the Pearl River 
population in an overall low condition. The Pearl River population in 
this faunal province is subject to threats such as erratic flows from 
water releases from the Ross Barrett Dam that are capable of causing 
bed movement or dislocation of mussels, increased sedimentation, and 
altered water chemistry (e.g., low temperatures), the threats are 
primarily occurring in the future. Under a moderate greenhouse gas 
emission trajectory (RCP 4.5), model projections no changes from 
current condition are expected within 10-years. Within 25-years, 
hydrologic conditions would be negatively affected by the construction 
of a flood control reservoir proposed for the upper portion of the 
focal area, resulting in a moderate decline in substrate condition as 
sediments accumulate on mussel beds from a lack or cleansing flows, and 
water quality degradation. Although these threats are not unique to 
this area, they may be acting at a greater intensity here, either 
individually or in combination, than elsewhere in the range, given the 
low abundance of Louisiana pigtoe in this reach. The small size of this 
population, coupled with the current condition information in the SSA 
report suggesting the population in this area has low resiliency, 
indicates the populations in the Pontchartrain-Pearl-Pascagoula faunal 
province may be in danger of extinction now.
    We evaluated the available information about this portion of the 
range of Louisiana pigtoe that occupies the upper Pearl River in this 
context, assessing its biological significance in terms of the three 
habitat criteria (habitat/structure, hydrology, and water quality; see 
Species Condition) used to assign the current condition of Louisiana 
Pigtoe populations, and determined the information did not indicate it 
may be significant. Louisiana pigtoe in this population exhibit similar 
habitat and host fish use to Louisiana pigtoe in the remainder of its 
range; thus, there is no unique observable environmental usage or 
behavioral characteristics attributable to just this area's population. 
The Pearl River is not essential to any specific life-history function 
of the Louisiana pigtoe that is not found elsewhere in the range. 
Further, the habitat in the Pearl River does not contain higher quality 
or higher value than the remainder of the species' range of the 
Louisiana pigtoe (see Table 3). Additionally, this population does not 
interact with other populations of the species. Overall, we found no 
substantial information that would indicate the population in the Pearl 
River may be significant. While this reach provides some contribution 
to the species' overall ability to withstand catastrophic or stochastic 
events (redundancy and resiliency, respectively), the species has 
larger populations in adjacent faunal provinces. The best scientific 
and commercial information available indicate that this populations' 
contribution is very limited in scope

[[Page 16796]]

due to small population size and isolation from other populations. 
Therefore, because we could not answer both the status and significance 
questions in the affirmative, we conclude that the Pearl River does not 
warrant further consideration as a significant portion of the range of 
the Louisiana pigtoe.
    Therefore, no portion of the species' range provides a basis for 
determining that the species is in danger of extinction in a 
significant portion of its range, and we determine that the species is 
likely to become in danger of extinction within the foreseeable future 
throughout all of its range. This does not conflict with the courts' 
holdings in Desert Survivors v. Department of the Interior, 321 F. 
Supp. 3d 1011, 1070-74 (N.D. Cal. 2018), and Center for Biological 
Diversity v. Jewell, 248 F. Supp. 3d, 946, 959 (D. Ariz. 2017) because, 
in reaching this conclusion, we did not need to consider whether any 
portions are significant and, therefore, did not apply the aspects of 
the Final Policy's definition of ``significant'' that those court 
decisions held were invalid.

Louisiana Pigtoe: Determination of Status

    Our review of the best available scientific and commercial 
information indicates that the Louisiana pigtoe meets the Act's 
definition of a threatened species. Therefore, we propose to list the 
Louisiana pigtoe 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 as a listed 
species, planning and implementation of 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, 
including the Service, 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 goal of this process is to restore listed 
species to a point where they are secure, self-sustaining, and 
functioning components of their ecosystems.
    The recovery planning process begins with development of a recovery 
outline made available to the public soon after a final listing 
determination. The recovery outline guides the immediate implementation 
of urgent recovery actions while a recovery plan is being developed. 
Recovery teams (composed of species experts, Federal and State 
agencies, nongovernmental organizations, and stakeholders) may be 
established to develop and implement recovery plans. The recovery 
planning process involves the identification of actions that are 
necessary to halt and reverse the species' decline by addressing the 
threats to its survival and recovery. The recovery plan 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. Revisions of the plan may 
be done to address continuing or new threats to the species, as new 
substantive information becomes available. The recovery outline, draft 
recovery plan, final recovery plan, and any revisions will be available 
on our website as they are completed (https://www.fws.gov/program/endangered-species).
    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 ranges 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 States of Arkansas, Oklahoma, 
Louisiana, Mississippi, and Texas would be eligible for Federal funds 
to implement management actions that promote the protection or recovery 
of the Texas heelsplitter and Louisiana pigtoe. Information on our 
grant programs that are available to aid species recovery can be found 
at: https://www.fws.gov/service/financial-assistance.
    Although the Texas heelsplitter and Louisiana pigtoe 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 
these 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 Federal Emergency 
Management Agency (related to disaster recovery projects), National 
Park Service, Natural Resources Conservation Service, National Wildlife 
Refuge System, U.S. Army, U.S. Army Corps of Engineers, and the U.S. 
Forest Service.

[[Page 16797]]

    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. The statute also contains certain 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 Act allows the Secretary to 
promulgate protective regulations for threatened species pursuant to 
section 4(d) of the Act. The discussion in the following section, 
Proposed Rule Issued Under Section 4(d) of the Act, regarding 
protective regulations under section 4(d) of the Act for the Louisiana 
pigtoe complies with our policy.
    For the Texas heelsplitter, 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, that are carried out in accordance with 
any existing regulations, permit and label requirements, and best 
management practices; and
    (2) Normal residential landscaping 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) Unauthorized destruction or alteration of Texas heelsplitter 
habitat by dredging, channelization, impoundment, diversion, 
recreational vehicle operation within the stream channel, sand or 
gravel removal, or other activities that result in the destruction or 
significant degradation of channel or bank stability, streamflow/water 
quantity, substrate composition, and water quality used by the species 
for foraging, cover, and reproduction;
    (3) Modification of the channel or water flow of any stream, 
including the withdrawal (decrease) or supplementation (increase) of 
surface or ground waters where the Texas heelsplitter is known to 
occur;
    (4) Livestock grazing that results in direct or indirect 
destruction of riparian or instream habitat; and
    (5) Unauthorized discharge of chemicals (including pesticides and 
fertilizers in violation of label restrictions), household waste, silt, 
sediments, fill material, or other pollutants (e.g., sewage, oil and 
gasoline, heavy metals), into any waters or their adjoining riparian 
areas where the Texas heelsplitter is known to occur.
    Questions regarding whether specific activities would constitute a 
violation of section 9 of the Act should be directed to the Arlington 
Ecological Services Field Office (see FOR FURTHER INFORMATION CONTACT).

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 she deems 
necessary and advisable to provide for the conservation of species 
listed as threatened. The U.S. Supreme Court has noted that statutory 
language similar to the language in section 4(d) of the Act authorizing 
the Secretary to take action that she ``deems necessary and advisable'' 
affords 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, as a valid 
exercise of agency authority, rules developed under section 4(d) that 
included limited prohibitions against takings (see Alsea Valley 
Alliance v. Lautenbacher, 2007 U.S. Dist. Lexis 60203 (D. Or. 2007); 
Washington Environmental Council v. National Marine Fisheries Service, 
2002 WL 511479 (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 [her] with regard to the permitted 
activities for those species. [She] may, for example, permit taking, 
but not importation of such species, or [she] 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).
    The provisions of this proposed 4(d) rule would promote 
conservation of the Louisiana pigtoe by encouraging riparian landscape 
conservation while also meeting the conservation needs of the Louisiana 
pigtoe. By streamlining those projects that follow best management 
practices and improve instream habitat (such as streambank

[[Page 16798]]

stabilization, instream channel restoration, and upland restoration 
that improves instream habitat), conservation is more likely to occur 
for Louisiana pigtoe, improving the condition of populations in those 
reaches. The provisions of this proposed rule are several of many tools 
that we would use to promote the conservation of the Louisiana pigtoe. 
This proposed 4(d) rule would apply only if and when we make final the 
listing of the Louisiana pigtoe as a threatened species.
    As mentioned previously in Available Conservation Measures, 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.
    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 Federal actions that are subject to 
the section 7 consultation process are actions on State, Tribal, local, 
or private lands that require a Federal permit (such as a permit from 
the U.S. Army Corps of Engineers under section 404 of the Clean Water 
Act (33 U.S.C. 1251 et seq.) or a permit from the Service under section 
10 of the Act) or that involve some other Federal action (such as 
funding from the Federal Highway Administration, Federal Aviation 
Administration, or the Federal Emergency Management Agency). 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.
    These requirements are the same for a threatened species with a 
species-specific 4(d) rule. For example, a Federal agency's 
determination that an action is ``not likely to adversely affect'' a 
threatened species will require the Service's written concurrence. 
Similarly, a Federal agency's determination that an action is ``likely 
to adversely affect'' a threatened species will require formal 
consultation and the formulation of a biological opinion.

Provisions of the Proposed 4(d) Rule

    Exercising the Secretary's authority under section 4(d) of the Act, 
we have developed a proposed rule that is designed to address the 
Louisiana pigtoe's specific conservation needs. As discussed previously 
in Summary of Biological Status and Threats, we have concluded that the 
Louisiana pigtoe 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. 
Section 4(d) requires the Secretary to issue such regulations as she 
deems necessary and advisable to provide for the conservation of each 
threatened species and authorizes the Secretary to include among those 
protective regulations any of the prohibitions that section 9(a)(2) of 
the Act prescribes for endangered species. We find that, if finalized, 
the protections, prohibitions, and exceptions in this proposed rule as 
a whole satisfy the requirement in section 4(d) of the Act to issue 
regulations deemed necessary and advisable to provide for the 
conservation of the Louisiana pigtoe.
    The protective regulations we are proposing for the Louisiana 
pigtoe incorporate prohibitions from section 9(a)(1) to address the 
threats to the species. Section 9(a)(1) prohibits the following 
activities for endangered wildlife: importing or exporting; take; 
possession and other acts with unlawfully taken specimens; delivering, 
receiving, transporting, or shipping in interstate or foreign commerce 
in the course of commercial activity; or selling or offering for sale 
in interstate or foreign commerce. This protective regulation includes 
most of these prohibitions for the Louisiana pigtoe because the 
Louisiana pigtoe is at risk of extinction in the foreseeable future and 
putting these prohibitions in place will help to preserve the species' 
remaining populations, slow its rate of decline, and decrease 
synergistic, negative effects from other stressors.
    In particular, this proposed 4(d) rule would provide for the 
conservation of the Louisiana pigtoe by prohibiting the following 
activities, unless they fall within specific exceptions or are 
otherwise authorized or permitted: Importing or exporting; take; 
possession and other acts with unlawfully taken specimens; delivering, 
receiving, transporting, or shipping in interstate or foreign commerce 
in the course of commercial activity; or selling or offering for sale 
in interstate or foreign commerce.
    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 
regulations at 50 CFR 17.3. Take can result knowingly or otherwise, by 
direct and indirect impacts, intentionally or incidentally. Regulating 
incidental and intentional take would help preserve the species' 
remaining populations, slow their rate of decline, and decrease 
synergistic, negative effects from other stressors. Therefore, we 
propose to prohibit take of the Louisiana pigtoe, except for take 
resulting from those actions and activities specifically excepted by 
the 4(d) rule.
    Exceptions to the prohibition on take would include most of the 
general exceptions to the prohibition against take of endangered 
wildlife, as set forth in 50 CFR 17.21 and certain other specific 
activities that we propose for exception, as described below.
    The proposed 4(d) rule would also provide for the conservation of 
the species by allowing exceptions that incentivize conservation 
actions or that, while they may have some minimal level of take of the 
Louisiana pigtoe, are not expected to rise to the level that would have 
a negative impact (i.e., would have only de minimis impacts) on the 
species' conservation. The proposed exceptions to these prohibitions 
include the following activities that are expected to have negligible 
impacts to the Louisiana pigtoe and its habitat:
    (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

[[Page 16799]]

proposed 4(d) rule for incidental take would promote conservation of 
Louisiana pigtoe 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 native stakes (live, vegetative cuttings inserted or tamped into 
the ground in a manner that allows the stake to take root and grow), 
live native fascines (live branch cuttings, usually willows, bound 
together into long, cigar-shaped bundles), or native brush layering 
(cuttings or branches of easily rooted tree species layered between 
successive lifts of soil fill). These methods must 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 must 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 Louisiana pigtoe 
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. We recommend that these practices and activities 
comply with specifications and technical guidelines developed by the 
U.S. Department of Agriculture's Natural Resources Conservation Service 
(NRCS), as 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 Louisiana pigtoe by 
creating stable stream channels and reducing sediment inputs to the 
stream, thereby increasing population resiliency.
    We include other standard exceptions to the prohibitions in the 
proposed 4(d) rule for the Louisiana pigtoe.
    Despite these prohibitions regarding threatened species, we may 
under certain circumstances issue permits to carry out one or more 
otherwise-prohibited activities, including those described above. The 
regulations that govern permits for threatened wildlife state that the 
Director may issue a permit authorizing any activity otherwise 
prohibited with regard to threatened species. These include permits 
issued for the following purposes: for 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 (50 CFR 
17.32). The statute also contains certain exemptions from the 
prohibitions, which are found in sections 9 and 10 of the Act.
    We recognize 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 us in implementing all aspects of the Act. In this 
regard, section 6 of the Act provides that we must 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 us in accordance with section 6(c) of the Act, who is designated 
by his or her agency for such purposes, would be able to conduct 
activities designed to conserve Louisiana pigtoe 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 our ability to 
enter into partnerships for the management and protection of the 
Louisiana pigtoe. However, interagency cooperation may be further 
streamlined through planned programmatic consultations for the species 
between us and other Federal agencies, where appropriate. 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 we could 
provide or use, respectively, to streamline the implementation of this 
proposed 4(d) rule (see Information Requested, above).

III. Critical Habitat

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).
    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 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

[[Page 16800]]

ownership or establish a refuge, wilderness, reserve, preserve, or 
other conservation area. Such designation also does not allow the 
government or public to access private lands. Such designation does not 
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 
likely 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).
    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.
    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.
    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) the prohibitions found in section 9 of the Act. 
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 this 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 Determination

    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12) require that, to the maximum extent prudent 
and determinable, the Secretary shall designate critical habitat at the 
time the species is determined to be an endangered or threatened 
species. 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 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 earlier in this document, there are well documented 
beds of Louisiana pigtoe that are sampled for scientific projects, and 
to a lesser degree collected by fishing enthusiasts for use as bait. 
Because these areas are already well known, and they are not being 
collected for private collections, there is currently no additional 
imminent threat of collection or vandalism identified under Factor B 
for these species, and identification and mapping of critical habitat 
is not expected to initiate any such threat. In our SSA and proposed 
listing determination for the Texas heelsplitter and Louisiana pigtoe, 
we determined that the present or threatened destruction, modification, 
or curtailment of habitat or range is a threat to these species and 
that those threats in some way can be addressed by section 7(a)(2) 
consultation measures. These species occur 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

[[Page 16801]]

the Secretary has not identified other circumstances for which this 
designation of critical habitat would be not prudent, we have 
determined that the designation of critical habitat is prudent for the 
Texas heelsplitter and Louisiana pigtoe.

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 Texas 
heelsplitter and Louisiana pigtoe 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 Texas heelsplitter and Louisiana 
pigtoe.

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, alkaline 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, we 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 the conservation of the Texas heelsplitter and Louisiana 
pigtoe from studies of these species' habitat, ecology, and life 
history. The life histories of these two freshwater mussel species are 
very similar--mussels need suitable water quality, flowing water, 
suitable substrate, flow refuges, and appropriate host fish--and so we 
will discuss their common habitat needs and then describe their 
species-specific needs.

Physiological Requirements: Water Quality Requirements

    Freshwater mussels, as a group, are sensitive to changes in water 
quality, including parameters such as dissolved oxygen, salinity, 
ammonia, and environmental pollutants (e.g., pesticides and trace 
metals). Habitats with appropriate levels of these parameters that are 
pollutant-free or have low levels of pollutants are considered 
suitable, while those habitats with levels outside of the appropriate 
ranges or that contain elevated pollutants are considered less 
suitable. We have used information for the Texas heelsplitter and 
Louisiana pigtoe, 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, with some species showing 
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 (Augspurger 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. Laboratory studies 
investigating the effects of thermal stress on glochidia and adults 
have indicated thermal stress may occur at 27 [deg]C (80.6 [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 Texas 
heelsplitter and Louisiana pigtoe:
     Water temperature below 27 [deg]C (80.6 [deg]F);
     Dissolved oxygen levels greater than 3 mg/L;
     Low salinity (less than 2 ppt) and total dissolved solids;
     Low total ammonia and nitrogen (below 0.3-0.7 mg/L total 
ammonia nitrogen);
     Low levels of copper, nickel, and other trace metals;
     Low levels of pesticides, sulfate, chloride, potassium, 
and other harmful constituents; and
     Low pollutants and environmental contaminants common to 
wastewater.

[[Page 16802]]

Space for Individual and Population Growth and for Normal Behavior

    Most freshwater mussels, including the Texas heelsplitter and 
Louisiana pigtoe, 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. Accordingly, sufficiently 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 the Texas heelsplitter and Louisiana pigtoe into the 
future than shorter stream reaches. Therefore, we determine that long 
stream reaches, over 50 river miles (80.5 km), are an important 
component of a riverine system with habitat to support all life stages 
of the Texas heelsplitter and Louisiana pigtoe. Populations occupying 
reaches shorter than 50 miles can still provide population redundancy 
and, if habitat factors are of sufficiently high quality, can be an 
important component of the recovery of Texas heelsplitter and Louisiana 
pigtoe.
    The Texas heelsplitter needs low to moderately flowing streams, and 
tolerates impoundments (lakes, reservoirs, or pools without flow). All 
life stages of the Texas heelsplitter require substrates consisting of 
firm mud, sand, finer gravels, and mixtures of those with high organic 
matter content. The Louisiana pigtoe needs flowing water for survival 
and occurs in medium- to large-sized streams and rivers associated with 
riffle, run, and sometimes larger backwater tributary habitats. All 
life stages of the Louisiana pigtoe require substrates consisting of 
cobble/rock, sand/gravel/woody debris, and runs with subdominant gravel 
mixtures. River reaches with continuous flow support all life stages of 
these two species of freshwater 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. Habitat 
locations must be relatively free of fine sediments for both species 
such that the mussels are not smothered.

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 Texas 
heelsplitter and Louisiana pigtoe 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 these two species of freshwater mussels:
     Texas heelsplitter: freshwater drum (Aplodinotus 
grunniens).
     Louisiana pigtoe: red shiner (Cyprinella (=Notropis) 
lutrensis), blacktail shiner (Cyprinella venusta), and bullhead minnow 
(Pimephales vigilax).

Summary of Essential Physical or Biological Features

    In summary, we derive the specific PBFs essential to the 
conservation of Texas heelsplitter and Louisiana pigtoe from studies of 
these species' habitat, ecology, and life history as described above. 
Additional information can be found in the SSA report available on 
https://www.regulations.gov under Docket No. FWS-R2-ES-2022-0026.
Texas Heelsplitter
    We have determined that the following PBFs are essential to the 
conservation of the Texas heelsplitter:
    1. Water quality parameters within the following ranges:
    a. Water temperature below 27 [deg]C (80.6 [deg]F);
    b. Dissolved oxygen levels greater than 3 mg/L;
    c. Low salinity (less than 2 ppt) and total dissolved solids;
    d. Low total ammonia and nitrogen (below 0.3-0.7 mg/L total ammonia 
nitrogen);
    e. Low levels of copper, nickel, and other trace metals;
    f. Low levels of pesticides, sulfate, chloride, potassium, and 
other harmful constituents; and
    g. Low pollutants and environmental contaminants common to 
wastewater.
    2. Moderately flowing water rates suitable to prevent excess 
sedimentation but not so high as to dislodge individuals or sediment; 
or no water flow, if in an impoundment (lake, reservoir, or pool 
without flow).
    3. Substrate including bedrock and boulder crevices, point bars, 
and vegetated run habitat comprising sand, gravel, and larger cobbles.
    4. Freshwater drum (Aplodinotus grunniens) present.
Louisiana Pigtoe
    We have determined that the following PBFs are essential to the 
conservation of the Louisiana pigtoe:
    1. Water quality parameters within the following ranges:
    a. Water temperature below 27 [deg]C (80.6 [deg]F);
    b. Dissolved oxygen levels greater than 3 mg/L;
    c. Low salinity (less than 2 ppt) and total dissolved solids;
    d. Low total ammonia and nitrogen (below 0.3-0.7 mg/L total ammonia 
nitrogen);
    e. Low levels of copper, nickel, and other trace metals;
    f. Low levels of pesticides, sulfate, chloride, potassium, and 
other harmful constituents; and
    g. Low pollutants and environmental contaminants common to 
wastewater.
    2. Moderately flowing water rates suitable to prevent excess 
sedimentation but not so high as to dislodge individuals or sediment.
    3. Stable bank and riffle habitats with bedrock and boulder 
crevices, point bars, and vegetated run habitat comprising sand, 
gravel, and larger cobbles.
    4. Red shiner (Cyprinella (=Notropis) lutrensis), blacktail shiner 
(Cyprinella venusta), and bullhead minnow (Pimephales vigilax) present.

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 Texas 
heelsplitter and Louisiana pigtoe 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 not limited to: Use of best management practices (BMPs) 
designed to reduce sedimentation, erosion, and bank side destruction; 
protection of riparian corridors and retention of sufficient canopy 
cover along banks; exclusion of livestock and nuisance wildlife (feral 
hogs, exotic ungulates); moderation of

[[Page 16803]]

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 not currently proposing to 
designate any areas outside the geographical area occupied by the Texas 
heelsplitter and Louisiana pigtoe because we have determined that the 
occupied areas are sufficient to conserve the species.
    We anticipate that recovery will require conserving the genetic 
diversity of extant populations across the species' current ranges and 
maintaining and, where necessary, improving habitat and habitat 
connectivity to ensure the long-term viability of the Texas 
heelsplitter and Louisiana pigtoe. This proposed critical habitat 
designation delineates the habitat that is physically occupied and used 
by the species rather than delineating all land or aquatic areas that 
influence the species. We recognize that there may be additional 
occupied areas outside of the proposed areas designated as critical 
habitat that we are not aware of at the time of this designation that 
may be necessary for the conservation of the species. We have 
determined that the areas currently occupied by the Texas heelsplitter 
and Louisiana pigtoe would maintain each species' resiliency, 
redundancy, and representation and are sufficient to conserve these two 
species. Therefore, we are not currently proposing to designate any 
areas outside the geographical area occupied by the species.
    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' range (Service 2022, pp. 16-24).

Areas Occupied at the Time of Listing

    The proposed critical habitat designations do not include all 
rivers and streams known to have been occupied by the species 
historically; instead, they focus on rivers and 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 a species' presence (e.g., Howells 1996, pp. ii, 
4; Randklev et al. 2011, p. 17).
    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 to 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 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. Humanmade reservoirs are not considered 
natural habitat for either species and may not contain all of the PBFs; 
therefore, they were not delineated as critical habitat for Texas 
heelsplitter, which occurs in some reservoirs. The recovery vision for 
Texas heelsplitter will not be focused on enhancing the species in 
these areas.
    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 10.6.1 
(ESRI, Inc.), a Geographic Information Systems program.
    We consider the following streams and rivers to be occupied by the 
Texas heelsplitter at the time of proposed listing: Neches River, 
Sabine River, and Trinity River.
    We consider the following streams and rivers to be occupied by the 
Louisiana pigtoe at the time of proposed listing: Angelina River, Big 
Cypress Bayou, Calcasieu River, Cossatot River, Little River, Neches 
River, Pearl River, Rolling Fork, Sabine River, Saline River, San 
Jacinto River, and Sulphur River.

General Information on the Maps of the Proposed Critical Habitat 
Designations

    When determining proposed critical habitat boundaries, we made 
every

[[Page 16804]]

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 Texas heelsplitter 
and Louisiana pigtoe. Critical habitat for these mussels includes only 
stream channels up to bankfull height, where the stream base flow is 
contained within the channel. 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 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 are proposing to designate as critical habitat three units for 
the Texas heelsplitter and six units for the Louisiana pigtoe based on 
one or more of the PBFs being present to support the Texas 
heelsplitter's or Louisiana pigtoe's life-history processes. Some units 
contain all of the identified physical or biological features and 
support multiple life-history processes. Some units contain only some 
of the PBFs necessary to support the Texas heelsplitter's or Louisiana 
pigtoe's particular use of that habitat.
    The proposed critical habitat designation is defined by the map or 
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 critical habitat 
designation in the preamble of this document. We will make the 
coordinates or plot points or both on which each map is based available 
to the public on https://www.regulations.gov at Docket No. FWS-R2-ES-
2022-0026, on our internet site https://www.fws.gov/office/arlington-ecological-services.

Proposed Critical Habitat Designation

    We are proposing to designate approximately 832 river mi (1,339 km) 
in three units as critical habitat for Texas heelsplitter and 
approximately 1,028 river mi (1,654 km) in six units for the Louisiana 
pigtoe. The critical habitat areas we describe below constitute our 
current best assessment of areas that meet the definition of critical 
habitat for Texas heelsplitter and Louisiana pigtoe. All units are 
occupied by their respective species. The three areas we propose as 
critical habitat for Texas heelsplitter are all in Texas and are: (1) 
Trinity River, (2) Sabine River, and (3) Neches River. The six areas we 
propose as critical habitat for Louisiana pigtoe are: (1) Little River 
(Arkansas/Oklahoma), (2) Sabine River (Louisiana/Texas), (3) Neches 
River (Texas), (4) San Jacinto River (Texas), (5) Calcasieu River 
(Louisiana), and (6) Pearl River (Louisiana/Mississippi). One proposed 
Louisiana pigtoe critical habitat subunit, LAPT-1a (Upper Little River, 
Oklahoma; 25.7 river miles (41.4 km)), is located within the Choctaw 
Reservation, but not on any lands held in trust for the Tribe, or owned 
or managed by the Tribe. Tables 5 and 6 show the proposed critical 
habitat units, the adjacent riparian area ownership, and the 
approximate area of each unit.

                       Table 5--Proposed Critical Habitat Units for the Texas Heelsplitter
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
              Unit                     Subunit       Riparian ownership        Occupied?          (kilometers)
----------------------------------------------------------------------------------------------------------------
TXHS-1: Trinity River..........  TXHS-1a: Trinity    Private, State....  Yes..................     212.8 (342.4)
                                  River.
                                 TXHS-1b: Bedias     Private...........  Yes..................       28.9 (46.5)
                                  Creek.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     241.7 (388.9)
----------------------------------------------------------------------------------------------------------------
TXHS-2: Sabine River...........  TXHS-2a: Upper      Private, State,     Yes..................     237.4 (382.0)
                                  Sabine River.       Local, Federal.
                                 TXHS-2b: Lake Fork  Private...........  Yes..................       13.8 (22.2)
                                  Creek.
                                 TXHS-2c: Patroon    Private, Federal..  Yes..................       19.9 (32.0)
                                  Bayou.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     271.1 (436.2)
----------------------------------------------------------------------------------------------------------------
TXHS-3: Neches River...........  TXHS-3a: Upper      Private, Federal..  Yes..................     227.9 (366.7)
                                  Neches River.
                                 TXHS-3b: Lower      Private, Federal..  Yes..................       14.7 (23.7)
                                  Angelina River.
                                 TXHS-3c: Lower      Private, State,     Yes..................      76.3 (122.8)
                                  Neches River.       Federal.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     318.9 (513.1)
                                                                        ----------------------------------------
        Total..................  ..................  ..................  .....................   831.8 (1,338.6)
----------------------------------------------------------------------------------------------------------------
Note: Lengths may not accurately sum due to rounding.


                        Table 6--Proposed Critical Habitat Units for the Louisiana Pigtoe
----------------------------------------------------------------------------------------------------------------
                                                                                                   River miles
              Unit                     Subunit       Riparian ownership        Occupied?          (kilometers)
----------------------------------------------------------------------------------------------------------------
LAPT-1: Little River...........  LAPT-1a: Upper      Private, State,     Yes..................      88.0 (141.6)
                                  Little River.       Federal, Tribal.
                                 LAPT-1b: Rolling    Private...........  Yes..................       29.9 (47.9)
                                  Fork.
                                 LAPT-1c: Cossatot   Private, Federal..  Yes..................       47.2 (75.9)
                                  River.
                                 LAPT-1d: Saline     Private...........  Yes..................       42.6 (68.5)
                                  River.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     207.7 (334.2)
----------------------------------------------------------------------------------------------------------------
LAPT-2: Sabine River...........  LAPT-2a: Upper      Private, State,     Yes..................     110.1 (177.2)
                                  Sabine River.       Federal.

[[Page 16805]]

 
                                 LAPT-2b: Anacoco    Private...........  Yes..................       12.2 (19.6)
                                  Bayou.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     122.3 (196.8)
----------------------------------------------------------------------------------------------------------------
LAPT-3: Neches River...........  LAPT-3a: Upper      Private, Federal..  Yes..................     200.4 (322.4)
                                  Neches River.
                                 LAPT-3b: Upper      Private, Federal..  Yes..................      67.4 (108.4)
                                  Angelina River.
                                 LAPT-3c: Lower      Private, State,     Yes..................      76.2 (122.6)
                                  Neches River.       Federal.
                                 LAPT-3d: Village    Private, State,     Yes..................       54.9 (88.3)
                                  Creek.              Federal.
                                 LAPT-3e: Big Sandy  Private, Federal..  Yes..................       43.7 (70.3)
                                  Creek.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     442.6 (712.1)
----------------------------------------------------------------------------------------------------------------
LAPT-4: East Fork San Jacinto    ..................  Private...........  Yes..................       23.3 (37.5)
 River.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................       23.3 (37.5)
----------------------------------------------------------------------------------------------------------------
LAPT-5: Calcasieu River........  LAPT-5a: Upper      Private, Federal..  Yes..................      92.0 (148.0)
                                  Calcasieu River.
                                 LAPT-5b: Whisky     Private, State....  Yes..................       21.7 (34.9)
                                  Chitto Creek.
                                 LAPT-5c: Tenmile    Private, State....  Yes..................       32.0 (51.5)
                                  Creek.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................     145.7 (234.4)
----------------------------------------------------------------------------------------------------------------
LAPT-6: Pearl River............  ..................  Private, State,     Yes..................      86.6 (139.3)
                                                      Federal.
                                                                        ----------------------------------------
    Unit Total.................  ..................  ..................  .....................      86.6 (139.3)
                                                                        ----------------------------------------
        Total..................  ..................  ..................  .....................           1,028.2
                                                                                                       (1,654.3)
----------------------------------------------------------------------------------------------------------------
Note: Lengths may not accurately sum due to rounding.

    We present brief descriptions of all units, and reasons why they 
meet the definition of critical habitat for the Texas heelsplitter 
(TXHS) or Louisiana pigtoe (LAPT) below.

Texas Heelsplitter

Unit TXHS-1: Trinity River
    Subunit TXHS-1a: Trinity River. The Trinity River Subunit includes 
212.8 river mi (342.4 km) in Anderson, Ellis, Freestone, Henderson, 
Houston, Kaufman, Leon, Madison, and Navarro Counties, Texas. The 
subunit begins at Lake Livingston (estimated from the State Highway 24 
bridge located 4.7 mi (7.6 km) northeast of Midway, Texas) and 
continues upstream to the State Highway 34 bridge, located 2.5 miles (4 
km) southwest of Rosser, Texas. Ownership of adjacent riparian areas is 
95 percent private and 5 percent State. Although this reach is 
approximately 20 mi (32.2 km) southeast and downstream of the Dallas-
Fort Worth Metroplex, activities occurring across the Metroplex 
continue to affect both water quality and quantity downstream, 
including in this subunit, even though it is located in a largely rural 
area and predominately within riparian woodlands and agricultural 
lands. The Trinity River Subunit is occupied by the Texas heelsplitter 
and contains all the PBFs essential to the conservation of the species 
most of the year. However, hydrologic conditions have been 
significantly altered by wastewater return flows, and flooding in the 
Trinity River can be extreme, causing the species to experience a 
variety of environmental stressors that degrade habitat quality, such 
as shear stress, scouring, erosion, sediment deposition and siltation, 
and bank collapse.
    The Trinity River Subunit is being affected by impoundments, 
wastewater return flows, ongoing agricultural activities, and 
development resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals, and surface water diversions. 
Therefore, special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. There is no overlap with any designated 
critical habitat for other listed species.
    Subunit TXHS-1b: Bedias Creek. The Bedias Creek Subunit is 
comprised of 28.9 river mi (46.5 km) in Grimes, Madison, and Walker 
Counties, Texas. The subunit continues upstream from Livingston Lake, 
as estimated from the Farm to Market Road 247 bridge located 9.2 mi 
(14.8 km) south-southeast of Midway, Texas, to the State Highway 90 
bridge located approximately 6.3 mi (10.1 km) south-southwest of 
Madisonville, Texas. Adjacent riparian areas are privately owned. This 
reach is largely rural and predominately within riparian woodlands and 
agricultural lands. The Bedias Creek Subunit is occupied by the Texas 
heelsplitter and contains all the PBFs essential to the conservation of 
the species most of the year. However, fluctuating drought conditions 
and flooding in Bedias Creek can cause the species to experience either 
extreme low-flow conditions with related reduced water quality or 
extreme high flows that mobilize substrates, erode habitat, or deposit 
sediment on Texas heelsplitter populations.
    The Bedias Creek Subunit is influenced by drought, low flows, and 
flooding (leading to scour), and 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. Therefore, special management may be required 
to reduce sedimentation, improve water quality, maintain adequate 
flows, and improve habitat connectivity. There is no overlap with any 
designated critical habitat for other listed species.
Unit TXHS-2: Sabine River
    Subunit TXHS-2a: Upper Sabine River. The Upper Sabine River Subunit 
includes 237.4 river mi (382 km) in Gregg, Harrison, Panola, Rains, 
Rusk,

[[Page 16806]]

Smith, Upshur, Van Zandt, and Wood Counties, Texas. The subunit extends 
upstream from the Louisiana/Texas State line, located approximately 2.4 
mi (3.9 km) north-northeast of Joaquin, Texas, to a utility easement 
approximately 0.9 river mile (1.4 km) below Tawakoni Lake dam. 
Ownership of adjacent riparian areas is approximately 93 percent 
private, 4 percent State, 1 percent local, and 2 percent Federal. This 
reach is mostly rural and predominately within riparian woodlands 
bordered by agricultural lands. The Upper Sabine River Subunit is 
occupied by the Texas heelsplitter and contains all the PBFs essential 
to the conservation of the species most of the year. However, drought 
conditions and flooding in the Sabine River can be significant, 
resulting in either extreme low-flow conditions with related reduced 
water quality or high flows that mobilize substrates, erode habitat, or 
deposit sediment on Texas heelsplitter populations. The City of 
Longview, Texas, is located north of the subunit approximately mid-
reach. Industrial and municipal wastewater associated with this urban 
area are discharged into the Sabine River Basin, negatively affecting 
water quality in some areas downstream.
    The Upper Sabine River Subunit is influenced by drought, low flows, 
and flooding (leading to scour), and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is an overlap of 110.05 river mi (177.11 km) of 
this unit with proposed critical habitat for the Louisiana pigtoe.
    Subunit TXHS-2b: Lake Fork Creek. The Lake Fork Creek Subunit 
consists of 13.8 river mi (22.2 km) in Wood County, Texas. The subunit 
extends upstream from its confluence with the Sabine River to the FM 49 
bridge, located approximately 5 mi (8 km) northeast of Mineola, Texas. 
Adjacent riparian areas are privately owned. This reach is mostly rural 
and predominately within riparian woodlands bordered by agricultural 
lands. The Lake Fork Creek Subunit is occupied by the Texas 
heelsplitter and contains all the PBFs essential to the conservation of 
the species most of the year. However, drought conditions and flooding 
in the Lake Fork Creek can cause the species to experience either 
extreme low-flow conditions with related reduced water quality or high 
flows that mobilize substrates, erode habitat, or deposit sediment on 
Texas heelsplitter populations.
    The Lake Fork Creek Subunit is influenced by drought, low flows, 
and flooding (leading to scour), and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is no overlap with any designated critical habitat 
for other listed species.
    Subunit TXHS-2c: Patroon Bayou. The Patroon Bayou Subunit includes 
19.9 river mi (32 km) in Sabine and Shelby Counties, Texas. This 
subunit begins at the mouth of Patroon Bayou (location estimated at the 
Reeves Road bridge, approximately 7 mi (11.3 km) north of Milam, Texas) 
and continues upstream to the State Highway 87 bridge located 11.3 mi 
(18.2 km) southeast of Shelbyville, Texas. Ownership of adjacent 
riparian areas are 93 percent private and 7 percent Federal. The 
Patroon Bayou Subunit is occupied by the Texas heelsplitter and 
contains all the PBFs essential to the conservation of the species most 
of the year. However, drought conditions and flooding in the Patroon 
Bayou can cause low-flow conditions with related reduced water quality 
or high flows that mobilize substrates, erode habitat, or deposit 
sediment on Texas heelsplitter populations.
    The Patroon Bayou Subunit is influenced by drought, low flows, and 
flooding (leading to scour), and 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. Therefore, special management considerations 
may be required to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. There is no 
overlap with any designated critical habitat for other listed species.
Unit TXHS-3: Neches River
    Subunit TXHS-3a: Upper Neches River. The Upper Neches River Subunit 
includes 227.9 river mi (366.7 km) of stream in Anderson, Angelina, 
Cherokee, Houston, Jasper, Polk, Trinity, and Tyler Counties, Texas. 
The subunit originates at B.A. Steinhagen Lake (estimated at a point 
located approximately 13 mi (20.9 km) east of Colmesneil, Texas) and 
continues upstream to a transmission line right-of-way (ROW) located 
approximately 1.1 river mi (1.8 km) below Palestine Lake Dam. Ownership 
of adjacent riparian areas is approximately 88 percent private and 12 
percent Federal. This reach is rural and predominately within riparian 
woodlands bordered by agricultural lands. The Upper Neches River 
Subunit is occupied by the Texas heelsplitter and contains all the PBFs 
essential to the conservation of the species most of the year. However, 
drought conditions and flooding in the Neches River can cause either 
extreme low-flow conditions with related reduced water quality or high 
flows that mobilize substrates, erode habitat, or deposit sediment on 
Texas heelsplitter populations.
    The Upper Neches River Subunit is influenced by drought, low flows, 
and flooding (leading to scour), and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is an overlap of 200.38 river mi (322.48 km) of 
this unit with proposed critical habitat for the Louisiana pigtoe.
    Subunit TXHS-3b: Lower Angelina River. The Lower Angelina River 
Subunit consists of 14.7 river mi (23.7 km) in Jasper County, Texas. 
The subunit extends upstream from B.A. Steinhagen Lake, estimated at a 
point located approximately 5.7 mi (9.2 km) west of Curtis, Texas, to a 
transmission line ROW located approximately 0.3 mile (0.5 km) below Sam 
Rayburn Reservoir. Ownership of adjacent riparian areas is 
approximately 89 percent private and 11 percent Federal. This reach is 
rural and predominately within riparian woodlands bordered by 
agricultural lands. The Lower Angelina River Subunit is occupied by the 
Texas heelsplitter and contains all the necessary PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in the Angelina River can be compounded by 
hydroelectric dam operations at Sam Rayburn Reservoir, causing the 
species to experience either extreme low-flow conditions with related 
reduced water quality or extreme high flows that mobilize substrates,

[[Page 16807]]

erode habitat, or deposit sediment on Texas heelsplitter populations.
    The Lower Angelina River Subunit is influenced by drought, low 
flows, and flooding (leading to scour), and the subunit is being 
affected by impoundments, ongoing agricultural activities, and 
development resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals, and surface water diversions. 
Therefore, special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. There is no overlap with any designated 
critical habitat for other listed species.
    Subunit TXHS-3c: Lower Neches River. The Lower Neches River Subunit 
occupies 76.3 river mi (122.8 km) in Hardin, Jasper, Jefferson, Orange, 
and Tyler Counties, Texas. The subunit extends upstream from the Lower 
Neches Valley Authority weir, located north of Beaumont, Texas, to the 
Walnut Run confluence, which is approximately 2.6 mi (4.2 km) southeast 
of the B.A. Steinhagen Dam. The Lower Neches River Subunit is 
hydrologically isolated from the Upper Neches River Subunit by B.A. 
Steinhagen Lake. Ownership of adjacent riparian areas is approximately 
88 percent private, 7 percent State, and 5 percent Federal. This reach 
is mostly rural and predominately within riparian woodlands bordered by 
agricultural lands. The Lower Neches River Subunit is occupied by the 
Texas heelsplitter and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in the Neches River can cause low-flow 
conditions with related reduced water quality or high flows that 
mobilize substrates, erode habitat, or deposit sediment on Texas 
heelsplitter populations.
    The Lower Neches River Subunit is influenced by drought, low flows, 
and flooding (leading to scour); and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, 
groundwater withdrawals, and surface water diversions. Therefore, 
special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. There is an overlap of 76.35 river mi 
(122.87 km) of this unit with proposed critical habitat for the 
Louisiana pigtoe.

Louisiana Pigtoe

Unit LAPT-1: Little River
    Subunit LAPT-1a: Upper Little River. The Upper Little River Subunit 
consists of approximately 88.0 river mi (141.6 km) of the mainstem 
Little River upstream of Millwood Lake, Arkansas, occupying portions of 
Little River and Sevier Counties, Arkansas, and McCurtain County, 
Oklahoma. This subunit extends upstream from the U.S. Highway 69/71 
bridge near Millwood Lake, Arkansas, to the Glover River confluence, 
located 2.6 mi (4.2 km) west-southwest of Golden, Oklahoma. This 
subunit is hydrologically connected to the Rolling Fork Subunit 
(Subunit LAPT-1b). Ownership of adjacent riparian areas is 
approximately 42 percent private, 1 percent State, 26 percent Federal, 
and 23 percent private land within the Choctaw Reservation, but not any 
lands held in trust for the Tribe, or owned or managed by the Tribe. 
This reach is entirely rural, with long sections of intact riparian 
woodlands bordered by agricultural lands. The Upper Little River 
Subunit is occupied by the Louisiana pigtoe and contains all the PBFs 
essential to the conservation of the species most of the year.
    Drought conditions and flooding in the Little River are seldom 
extreme; however, this subunit is affected by hydroelectric dam-related 
cold water releases in the Mountain Fork from Broken Bow Reservoir and 
ongoing agricultural activities, resulting in excessive sedimentation, 
water quality degradation, ground water withdrawals, and surface water 
diversions. Therefore, special management considerations may be 
required to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. The Upper Little 
River Subunit is occupied by four federally listed freshwater mussels, 
the endangered pink mucket (Lampsilis abrupta), the threatened 
rabbitsfoot (Theliderma cylindrica, listed as Quadrula cylindrica 
cylindrica), the endangered winged mapleleaf (Quadrula fragosa), and 
the endangered Ouachita rock pocketbook (Arcidens wheeleri, listed as 
Arkansia wheeleri). There is overlap of 88.3 river mi (142.1 km) of 
this unit with designated critical habitat for rabbitsfoot (see 50 CFR 
17.95(f) and 80 FR 24692, April 30, 2015).
    Subunit LAPT-1b: Rolling Fork. The Rolling Fork Subunit consists of 
approximately 29.9 river mi (47.9 km) in Sevier County, Arkansas. The 
subunit extends upstream from the Little River confluence to the falls/
bedrock ledge located approximately 0.5 river mile (0.8 km) downstream 
of DeQueen Lake Dam. Ownership of adjacent riparian areas is privately 
held. This reach is entirely rural, and predominately agricultural 
lands and riparian woodlands. The Rolling Fork Subunit is occupied by 
the Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year.
    Drought conditions and flooding in Rolling Fork are seldom extreme; 
however, this subunit is affected by impoundments and ongoing 
agricultural activities, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals, and surface water 
diversions. Therefore, special management considerations may be 
required to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. There is no overlap 
with any designated critical habitat for other listed species.
    Subunit LAPT-1c: Cossatot River. The Cossatot River Subunit 
consists of approximately 47.2 river mi (75.9 km) of stream located 
within Sevier County, Arkansas. This subunit extends upstream from the 
U.S. Highway 69/71 bridge near Millwood Lake, Arkansas, to the Howard/
Sevier County line in southeast Arkansas. Ownership of adjacent 
riparian areas is approximately 85 percent private and 15 percent 
Federal. This reach is entirely rural, and predominately riparian 
woodlands bordered by agricultural lands. The Cossatot River Subunit is 
occupied by the Louisiana pigtoe and contains all the PBFs essential to 
the conservation of the species most of the year.
    Drought conditions and flooding in the Cossatot River are seldom 
extreme; however, this subunit is affected by impoundments and ongoing 
agricultural activities, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals, and surface water 
diversions. Therefore, special management considerations may be 
required to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. There is no overlap 
with any designated critical habitat for other listed species.
    Subunit LAPT-1d: Saline River. The Saline River Subunit consists of 
approximately 42.6 river mi (68.5 km) of stream located along the 
Howard/Sevier County line in southeast Arkansas. This subunit extends 
upstream from the Bright Star Road bridge, which is located immediately 
north of Millwood Lake, to the Thirty Thousand Road (County Road 80) 
bridge located

[[Page 16808]]

approximately 3.8 mi (6.1 km) west-northwest of Dierks, Arkansas. 
Adjacent riparian areas are privately owned. This reach is entirely 
rural, and predominately riparian woodlands bordered by agricultural 
lands. The Saline River Subunit is occupied by the Louisiana pigtoe and 
contains all the PBFs essential to the conservation of the species most 
of the year.
    Drought conditions and flooding in the Saline River are seldom 
extreme; however, this subunit is affected by impoundments and ongoing 
agricultural activities, resulting in excessive sedimentation, water 
quality degradation, ground water withdrawals, and surface water 
diversions. Therefore, special management considerations may be 
required to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. There is no overlap 
with any designated critical habitat for other listed species.
Unit LAPT-2: Sabine River
    Subunit LAPT-2a: Upper Sabine River. The Upper Sabine River Subunit 
consists of 110.1 river mi (177.2 km) occupying portions of Gregg, 
Harrison, Panola, Rusk, Smith, Upshur, and Wood Counties, Texas. This 
subunit continues upstream from the State Highway 43 bridge, which is 5 
mi (8 km) northeast of Tatum, Texas, and terminates at the Farm-to-
Market Road 1804 bridge located 3.3 mi (5.3 km) southeast of Mineola, 
Texas. Ownership of adjacent riparian areas is approximately 96 percent 
private, 2 percent State, and 2 percent Federal. This reach is mostly 
rural and predominately within riparian woodlands bordered by 
agricultural lands.
    The Upper Sabine River Subunit is occupied by the Louisiana pigtoe 
and contains all the PBFs essential to the conservation of the species 
most of the year. However, drought conditions and flooding in the 
Sabine River can be extreme, causing the species to experience either 
extreme low-flow conditions with associated reduced water quality or 
extreme high flows that mobilize substrates, erode habitat, or deposit 
sediment on Louisiana pigtoe populations. The City of Longview, Texas, 
is located north of the subunit at approximately one-third of the reach 
length upstream from the downstream terminus. Industrial and municipal 
wastewater associated with this urban area are discharged into the 
Sabine River Basin. The Upper Sabine River Subunit is influenced by 
drought, low flows, and flooding (leading to scour), and the subunit is 
being affected by impoundments, ongoing agricultural activities, and 
development resulting in excessive sedimentation, water quality 
degradation, ground water withdrawals, and surface water diversions. 
Therefore, special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. There is an overlap of 110.05 river mi 
(177.11 km) of this unit with proposed critical habitat for the Texas 
heelsplitter.
    Subunit LAPT-2b: Anacoco Bayou. The Anacoco Bayou Subunit consists 
of 12.2 river mi (19.6 km) in Vernon Parish, Louisiana. The subunit 
extends upstream from the Beauregard/Vernon parish line, situated 
approximately 8 mi (12.9 km) northwest of DeRidder, Louisiana, and 
terminates at the Hawks Road bridge, located approximately 4.8 mi (7.7 
km) northwest of Rosepine, Louisiana. Adjacent riparian areas are 
privately owned. This reach is mostly rural and predominately within 
riparian woodlands. The Anacoco Bayou Subunit is occupied by the 
Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in Anacoco Bayou can be extreme, causing the 
species to experience either extreme low-flow conditions with 
associated reduced water quality or extreme high flows that mobilize 
substrates, erode habitat, or deposit sediments on Louisiana pigtoe 
populations.
    Three sand and gravel mining operations and one paper mill that 
exist adjacent to this subunit likely negatively affect water quality 
from activities that generate point and non-point source pollution. 
Wastewater and storm water runoff associated with these activities are 
discharged into Anacoco Bayou drainage. The Anacoco Bayou Subunit is 
influenced by drought, low flows, and flooding (leading to scour), and 
the subunit is being affected by impoundments, as well as ongoing 
mining and industrial activities resulting in excessive sedimentation, 
water quality degradation, ground water withdrawals, and surface water 
diversions. Therefore, special management considerations may be 
required to reduce sedimentation, improve water quality, maintain 
adequate flows, and improve habitat connectivity. There is no overlap 
with any designated critical habitat for other listed species.
Unit LAPT-3: Neches River
    Subunit LAPT-3a: Upper Neches River. The Upper Neches River Subunit 
extends for 200.4 river mi (322.4 km) through parts of Anderson, 
Angelina, Cherokee, Houston, Polk, Trinity, and Tyler Counties, Texas. 
The downstream boundary corresponds to U.S. Highway 59 bridge, 
approximately 4 mi (6.4 km) south of Diboll, Texas, and the upstream 
boundary is located at a transmission line ROW approximately 1.1 river 
mi (1.8 km) below Palestine Lake Dam. Ownership of adjacent riparian 
areas is approximately 89 percent private and 11 percent Federal. This 
reach is mostly rural and predominately within riparian woodlands 
bordered by agricultural lands. The Upper Neches River Subunit is 
occupied by the Louisiana pigtoe and contains all the PBFs essential to 
the conservation of the species most of the year. However, drought 
conditions and flooding in the Neches River can be significant, causing 
the species to experience either extreme low-flow conditions with 
associated reduced water quality or extreme high flows that mobilize 
substrates, erode habitat, or deposit sediment on Louisiana pigtoe 
populations.
    The Upper Neches River Subunit is influenced by drought, low flows, 
and flooding (leading to scour), and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. The entire subunit overlaps with proposed critical 
habitat for the Texas heelsplitter.
    Subunit LAPT-3b: Upper Angelina River. The Upper Angelina River 
Subunit includes 67.4 river mi (108.4 km) in Angelina, Cherokee, and 
Nacogdoches Counties, Texas. The subunit extends upstream from the 
Union Pacific Railroad crossing, located approximately 3.7 mi (6 km) 
north-northwest of Redland, Texas, to the State Highway 204 bridge 
located 1.6 mi (2.6 km) west of Sacul, Texas. This subunit is 
hydrologically isolated from the Upper Neches River Subunit by Sam 
Rayburn Reservoir. Ownership of adjacent riparian areas is 
approximately 50 percent private and 50 percent Federal. This reach is 
mostly rural and predominately within riparian woodlands bordered by 
agricultural lands. The Upper Angelina River Subunit is occupied by the 
Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in the Angelina River can result in either 
extreme low-flow conditions with

[[Page 16809]]

associated reduced water quality or extreme high flows that mobilize 
substrates, erode habitat, or deposit sediments on Louisiana pigtoe 
populations.
    The Upper Angelina River Subunit is influenced by drought, low 
flows, and flooding (leading to scour); the subunit is being affected 
by impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is no overlap with any designated critical habitat 
for other listed species.
    Subunit LAPT-3c: Lower Neches River. The Lower Neches River Subunit 
occupies 76.2 river mi (122.6 km) in Hardin, Jasper, Jefferson, Orange, 
and Tyler Counties, Texas. The subunit extends upstream from the Lower 
Neches Valley Authority weir, located north of Beaumont, Texas, to the 
Walnut Run confluence, which is approximately 2.6 mi (4.2 km) southeast 
of the B.A. Steinhagen Dam. The Lower Neches River Subunit is 
hydrologically isolated from the Upper Neches River Subunit by B.A. 
Steinhagen Lake. Ownership of adjacent riparian areas is approximately 
88 percent private, 7 percent State, and 5 percent Federal. This reach 
is mostly rural and predominately within riparian woodlands bordered by 
agricultural lands. The Lower Neches River Subunit is occupied by the 
Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in the Neches River can cause the species to 
experience either extreme low-flow conditions with associated reduced 
water quality or extreme high flows that mobilize substrates, erode 
habitat, or deposit sediments on Louisiana pigtoe populations.
    The Lower Neches River Subunit is influenced by drought, low flows, 
and flooding (leading to scour); the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, 
groundwater withdrawals, and surface water diversions. Therefore, 
special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. The entire subunit overlaps with proposed 
critical habitat for the Texas heelsplitter.
    Subunit LAPT-3d: Village Creek. The Village Creek Subunit includes 
54.9 river mi (88.3 km) of stream in Hardin County, Texas. The subunit 
originates at the Village Creek confluence with the Neches River, 
located approximately 1.6 mi (2.6 km) north-northwest of Lakeview, 
Texas, and continues up Village Creek to its terminus at the confluence 
of Big Sandy and Kimball creeks, located approximately 1.6 mi (2.6 km) 
south-southeast of Wildwood, Texas. Ownership of adjacent riparian 
areas is approximately 20 percent private, 2 percent State, and 78 
percent Federal. Although some urban encroachment occurs in the lower 
half of the reach, it is mostly rural and predominately within riparian 
woodlands bordered by agricultural lands. The Village Creek Subunit is 
occupied by the Louisiana pigtoe and contains all the PBFs essential to 
the conservation of the species most of the year. However, drought 
conditions and flooding in Village Creek can be extreme, causing the 
species to experience either extreme low-flow conditions with 
associated reduced water quality or extreme high flows that mobilize 
substrates, erode habitat, or deposit sediments on Louisiana pigtoe 
populations.
    The Village Creek Subunit is influenced by drought, low flows, and 
flooding (leading to scour); the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is no overlap with any designated critical habitat 
for other listed species.
    Subunit LAPT-3e: Big Sandy Creek. The Big Sandy Creek Subunit 
consists of 43.7 river mi (70.3 km) of stream in Hardin, Polk, and 
Tyler Counties, Texas. The subunit continues upstream from its 
confluence with Kimball Creek, located approximately 1.6 mi (2.6 km) 
south-southeast of Wildwood, Texas, to the Alabama-Coushatta 
Reservation boundary. This boundary is 1.4 river mi (2.25 km) southeast 
of the U.S. Highway 190 bridge, which is located approximately 12.8 mi 
(20.6 km) east of Livingston, Texas. Ownership of adjacent riparian 
areas is approximately 5 percent private and 95 percent Federal. This 
reach is mostly rural and predominately within riparian woodlands 
bordered by agricultural lands. The Big Sandy Creek Subunit is occupied 
by the Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in Big Sandy Creek can be significant, 
resulting in low-flow conditions with associated reduced water quality 
or high flows that mobilize substrates, erode habitat, or deposit 
sediments on Louisiana pigtoe populations.
    The Big Sandy Creek Subunit is influenced by drought, low flows, 
and flooding (leading to scour), and 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. Therefore, special management considerations 
may be required to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. There is no 
overlap with any designated critical habitat for other listed species.
Unit LAPT-4: East Fork San Jacinto River
    The East Fork San Jacinto River Unit includes 23.3 river mi (37.5 
km) of the East Fork San Jacinto River in Liberty and Montgomery 
Counties, Texas. The downstream boundary of this unit is located at the 
FM 1485 bridge approximately 1 mile (1.6 km) east of Lake Houston 
Wilderness Park. The upstream boundary coincides with the Low Water 
Bridge Road (FM 388) bridge approximately 1.6 mi (2.6 km) northwest of 
Cleveland, Texas. Adjacent riparian areas are privately owned. Although 
located 10 mi northwest of the Houston metropolitan area, this reach is 
mostly rural and predominately within riparian woodlands, but it is 
bordered by developed areas. Four sand and gravel mining operations are 
located adjacent to this unit. The East Fork San Jacinto River Unit is 
occupied by the Louisiana pigtoe and contains all the PBFs essential to 
the conservation of the species most of the year. However, drought 
conditions and flooding in the East Fork San Jacinto River can be 
extreme, causing the species to experience either extreme low-flow 
conditions with associated reduced water quality or extreme high flows 
that mobilize substrates, erode habitat, or deposit sediments on 
Louisiana pigtoe populations.
    The East Fork San Jacinto River Unit is influenced by drought, low 
flows, and flooding (leading to scour), and the unit is being affected 
by ongoing agricultural activities and development resulting in 
excessive sedimentation, water quality

[[Page 16810]]

degradation, ground water withdrawals, and surface water diversions. 
Therefore, special management considerations may be required to reduce 
sedimentation, improve water quality, maintain adequate flows, and 
improve habitat connectivity. There is no overlap with any designated 
critical habitat for other listed species.
Unit LAPT-5: Calcasieu River
    Subunit LAPT-5a: Upper Calcasieu River. The Upper Calcasieu River 
Subunit includes 92.0 river mi (148.0 km) located in Allen and Rapides 
parishes, Louisiana. The subunit originates at the Union Pacific 
Railroad crossing located south of U.S. Highway 190 approximately 4 mi 
(6.4 km) west of Kinder, Louisiana, and continues upstream to the Price 
Road bridge, located 3.1 mi (5 km) northwest of Hineston, Louisiana. 
Ownership of adjacent riparian areas is 78 percent private and 22 
percent Federal. This reach is rural and predominately within riparian 
woodlands. The Upper Calcasieu River Subunit is occupied by the 
Louisiana pigtoe and contains all the PBFs essential to the 
conservation of the species most of the year. However, drought 
conditions and flooding in the Calcasieu 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 
substrates, erode habitat, or deposit sediment on Louisiana pigtoe 
populations.
    The Upper Calcasieu River Subunit is influenced by drought, low 
flows, and flooding (leading to scour), and 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. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is no overlap with any designated critical habitat 
for other listed species.
    Subunit LAPT-5b: Whisky Chitto Creek. The Whisky Chitto Creek 
Subunit includes 21.7 river mi (34.9 km) located in Allen Parish, 
Louisiana. The subunit extends from its confluence with Calcasieu River 
to the Tenmile Creek confluence, which is located approximately 0.7 mi 
(1.1 km) northeast of Mittie, Louisiana. Ownership of adjacent riparian 
areas is 1 percent private and 99 percent State. This reach is rural 
and predominately within riparian woodlands. The Whisky Chitto Creek 
Subunit is occupied by the Louisiana pigtoe and contains all the PBFs 
essential to the conservation of the species most of the year. However, 
drought conditions and flooding in the Whisky Chitto Creek can be 
extreme, causing the species to experience either extreme low-flow 
conditions with related reduced water quality or extreme high flows 
that mobilize substrates, erode habitat, or deposit sediment on 
Louisiana pigtoe populations.
    The Whisky Chitto Creek Subunit is influenced by drought, low 
flows, and flooding (leading to scour), and 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. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. There is no overlap with any designated critical habitat 
for other listed species.
    Subunit LAPT-5c: Tenmile Creek. The Tenmile Creek Subunit consists 
of 32.0 river mi (51.5 km) in Allen, Rapides, and Vernon parishes, 
Louisiana. The Tenmile Creek Subunit continues upstream from the Whisky 
Chitto Creek confluence located 0.7 mi (1.1 km) northeast of Mittie, 
Louisiana, to the 10 Mile Road bridge located approximately 5 mi (8 km) 
north of Elizabeth, Louisiana. Ownership of adjacent riparian areas is 
98 percent private and 2 percent State. This reach is rural and 
predominately within riparian woodlands. The Tenmile Creek Subunit is 
occupied by the Louisiana pigtoe and contains all the PBFs essential to 
the conservation of the species most of the year. However, drought 
conditions and flooding in the Tenmile Creek can be extreme, causing 
the species to experience either extreme low-flow conditions with 
related reduced water quality or extreme high flows that mobilize 
substrates, erode habitat, or deposit sediment on Louisiana pigtoe 
populations.
    The Tenmile Creek Subunit is influenced by drought, low flows, and 
flooding (leading to scour), and 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. Therefore, special management considerations 
may be required to reduce sedimentation, improve water quality, 
maintain adequate flows, and improve habitat connectivity. There is no 
overlap with any designated critical habitat for other listed species.
Unit LAPT-6: Pearl River
    The Pearl River Unit consists of 86.6 river mi (139.3 km) in St. 
Tammany and Washington parishes, Louisiana, and Marion and Pearl River 
Counties, Mississippi. The Pearl River splits into two significant 
channels within Bogue Chitto National Wildlife Refuge, and a navigation 
channel is associated with the west channel. Proposed critical habitat 
river mileage is calculated from the east channel only, but the Pearl 
River Unit does include the west channel by definition. The navigation 
channel is excluded from the unit. Following the east channel, the 
Pearl River Unit extends upstream along the Louisiana/Mississippi State 
line from the I-59 bridge located 1 mile (1.6 km) south of Nicholson, 
Mississippi, to where the Pearl River enters Louisiana from 
Mississippi, which is located 3.9 mi (6.3 km) southeast of Sandy Hook, 
Mississippi. The west channel extends from the I-59 bridge located 0.9 
mi (1.4 km) northeast of Pearl River, Louisiana, and continues upstream 
to its confluence with the east channel, which is located approximately 
2.7 mi (4.3 km) west of Industrial, Mississippi. Ownership of adjacent 
riparian areas is 44 percent private, 14 percent State, and 42 percent 
Federal. This reach is largely rural and predominately within riparian 
woodlands. The Pearl River Unit is occupied by the Louisiana pigtoe and 
contains all the PBFs essential to the conservation of the species most 
of the year. However, drought conditions and flooding in the Pearl 
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 substrates, erode habitat, or deposit sediment on 
Louisiana pigtoe populations.
    The Pearl River Unit is influenced by drought, low flows, and 
flooding (leading to scour), and the subunit is being affected by 
impoundments, ongoing agricultural activities, and development 
resulting in excessive sedimentation, water quality degradation, ground 
water withdrawals, and surface water diversions. Therefore, special 
management considerations may be required to reduce sedimentation, 
improve water quality, maintain adequate flows, and improve habitat 
connectivity. The entire subunit overlaps with critical habitat for the 
federally listed Gulf sturgeon (Acipenser oxyrinchus (=oxyrhynchus) 
desotoi) (see 50 CFR 17.95(e)).

[[Page 16811]]

Effects of Critical Habitat Designation

Section 7 Consultation

    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 which 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 rule revising the 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 (such as a permit from the 
U.S. Army Corps of Engineers under section 404 of the Clean Water Act 
(33 U.S.C. 1251 et seq.) or a permit from the Service under section 10 
of the Act) or that involve some other Federal action (such as funding 
from the Federal Highway Administration, Federal Aviation 
Administration, or the Federal Emergency Management Agency). 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.
    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 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, 
subsequent to the previous consultation: (a) if the amount or extent of 
taking specified in the incidental take statement is exceeded; (b) 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; (c) 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 written 
concurrence; or (d) 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 Congress also enacted some 
exceptions in 2018 to the requirement to reinitiate consultation on 
certain land management plans on the basis of a new species listing or 
new designation of critical habitat that may be affected by the subject 
Federal action. See 2018 Consolidated Appropriations Act, Public Law 
115-141, Div, O, 132 Stat. 1059 (2018).

Application of the ``Destruction or 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 section 
7(a)(2) of the Act by destroying or adversely modifying such habitat, 
or that may be affected by such designation.
    Activities that we may, during a consultation under section 7(a)(2) 
of the Act, consider likely to destroy or adversely modify critical 
habitat include, but are not limited to, actions that would: (1) Alter 
the minimum flow or the existing flow regime (for example, impoundment, 
channelization, water diversion, water withdrawal, or hydropower 
generation); (2) significantly alter water chemistry or temperature 
(for example, release of chemicals, biological pollutants, or heated 
effluents into surface water or connected groundwater at a point source 
or by dispersed release (nonpoint source)); (3) significantly increase 
sediment deposition within the stream channel (for example, excessive 
sedimentation from livestock grazing; road construction; channel 
alteration; timber harvest; off-road vehicle use; agricultural, 
industrial, or urban development; or other watershed and floodplain 
disturbances); and (4) significantly alter channel morphology or 
geometry (for example, channelization, impoundment, road and bridge 
construction, mining, dredging, or 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 mussels or their fish hosts.

[[Page 16812]]

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 (DoD), or designated for its use, that are subject to an 
integrated natural resources management plan (INRMP) prepared under 
section 101 of the Sikes Act Improvement Act of 1997 (16 U.S.C. 670a), 
if the Secretary determines in writing that such plan provides a 
benefit to the species for which critical habitat is proposed for 
designation. No DoD lands with a completed INRMP are within the 
proposed critical habitat designations.

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 designated critical habitat based on 
economic impacts, impacts on national security, or any other relevant 
impacts. Exclusion decisions are governed by the regulations at 50 CFR 
424.19 and the Policy Regarding Implementation of Section 4(b)(2) of 
the Endangered Species Act (hereafter, the ``2016 Policy''; 81 FR 7226, 
February 11, 2016), both of which were developed jointly with the 
National Marine Fisheries Service (NMFS). We also refer to a 2008 
Department of the Interior Solicitor's opinion entitled ``The 
Secretary's Authority to Exclude Areas from a Critical Habitat 
Designation under section 4(b)(2) of the Endangered Species Act'' (M-
37016).
    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 discretion to exclude the area only if such exclusion would 
not result in the extinction of the species. In making the 
determination to exclude a particular area, 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. In our final rules, we explain any decision to exclude 
areas, as well as decisions not to exclude, to demonstrate that the 
decision is reasonable. We describe below the process that we use for 
taking into consideration each category of impacts and any initial 
analyses of the relevant impacts.

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 the impacts that a specific critical habitat 
designation may have on restricting or modifying 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 for the 
particular species. 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 socio-
economic 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 this particular designation, we developed an incremental 
effects memorandum (IEM) considering the probable incremental economic 
impacts that may result from this 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 designation of 
critical habitat for the Texas heelsplitter and the Louisiana pigtoe 
(IEc 2021, entire). We began by conducting a screening analysis of the 
proposed designations 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 any probable economic impacts where land and water use may 
already 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. If the proposed critical 
habitat designation contains any unoccupied units, the screening 
analysis assesses whether those units require additional management or 
conservation efforts that may incur incremental economic impacts 
(although here the proposed critical habitat designations does not 
contain any unoccupied units). This screening analysis, combined with 
the information contained in our IEM, are what we consider our draft 
economic analysis (DEA) of the proposed critical habitat designations 
for the Texas heelsplitter and Louisiana pigtoe; our DEA 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

[[Page 16813]]

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 critical habitat designations. In our evaluation 
of the probable incremental economic impacts that may result from the 
proposed designations of critical habitat for the Texas heelsplitter 
and Louisiana pigtoe, first we identified, in the IEM dated September 
1, 2021, probable incremental economic impacts associated with the 
following categories of activities: (1) Federal lands management 
(National Park Service, National Wildlife Refuge System, U.S. Forest 
Service, U.S. Army Corp of Engineers, Natural Resources Conservation 
Service, Department of the Army); (2) industrial, municipal, and 
agricultural water users and dischargers (including wastewater 
treatment plants); (3) water supply delivery and treatment; (4) 
reservoir and dam operations; (5) transportation; (6) petroleum 
pipelines that may cross proposed designated stream reaches; (7) 
residential, commercial, industrial, and agricultural development; and 
(8) disaster recovery from hurricanes and flooding. We considered each 
industry or category individually. Additionally, we considered whether 
their 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 these species, in areas where the Texas 
heelsplitter and Louisiana pigtoe are present, Federal agencies would 
be required to consult with the Service under section 7 of the Act on 
activities they fund, permit, or implement that may affect the species. 
If, when we list the species, we also finalize this proposed critical 
habitat designation, Federal agencies would be required to consider the 
effects of their actions on the designated habitat, and if the Federal 
action may affect critical habitat, our consultations would include an 
evaluation of measures to avoid the destruction or adverse modification 
of critical habitat.
    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 designation (i.e., difference 
between the jeopardy and adverse modification standards) for the Texas 
heelsplitter's and Louisiana pigtoe's critical habitat. Because the 
designations of critical habitat for Texas heelsplitter and Louisiana 
pigtoe are being proposed concurrently with their listings, 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 
will 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 Texas 
heelsplitter and Louisiana pigtoe 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 
designation 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 Texas 
heelsplitter and Louisiana pigtoe include a total of nine units, all of 
which are occupied by their respective species. Ownership of riparian 
lands adjacent to the nine proposed units includes 1,214 river mi 
(1,954 km; 82.2 percent) in private ownership, and 262 river mi (422 
km; 17.8 percent) in public (Federal, State, or Local) ownership. In 
these areas, any actions that may affect the two species or their 
habitats would also affect designated critical habitat.
    Total incremental costs of critical habitat designation for the 
Texas heelsplitter and Louisiana pigtoe are not expected to exceed 
$51,800 (2021 dollars) per year. The costs are reflective of: (1) All 
proposed units are considered occupied, (2) project modifications 
requested to avoid adverse modification are likely to be the same as 
those recommended to avoid jeopardy in occupied habitat for these 
species, and (3) a portion of the proposed designations receive 
baseline protection from the presence of critical habitat for co-
occurring listed mussel species with similar habitat needs. Because 
consultation would be required as a result of the listing of the Texas 
heelsplitter and Louisiana pigtoe and is already required in some of 
these areas as a result of the presence of other listed species and 
critical habitats, the economic costs of the critical habitat 
designation would likely be primarily limited to additional 
administrative efforts to consider adverse modification for these two 
species in section 7 consultations.
    Based on the consultation history regarding historical projects and 
activities overlapping the proposed critical habitat areas for the 
Texas heelsplitter and Louisiana pigtoe, the number of future 
consultations, including technical assistance efforts, is likely to be 
no more than nine per year across all nine units. Overall, 
transportation and utilities activities are expected to result in the 
largest portion of consultations for both the Texas heelsplitter and 
Louisiana pigtoe and, therefore, to incur the highest costs. The 
geographic distribution of future section 7 consultations and 
associated costs are likely to be most heavily concentrated in all 
three proposed units for the Texas heelsplitter, and in proposed Units 
2 and 3 for the Louisiana pigtoe. However, even assuming consultation 
activity increases substantially, incremental administrative costs are 
still likely to remain well under $100 million per year. Therefore, 
based on the definition of significance in E.O. 12866, they would not 
be significant.
    The entities most likely to incur incremental costs are parties to 
section 7 consultations, including Federal action agencies and, in some 
cases, third parties, most frequently State agencies or municipalities. 
Activities we expect would be subject to consultations that may involve 
private entities as third parties are farms and ranches acquiring 
funding through Federal agricultural programs, oil and gas production 
regulated by the Federal Energy Regulatory Commission, and 
infrastructure projects that involve Federal funding or authorization. 
However, based on coordination efforts with State and local agencies, 
the cost to private entities in these sectors is expected to be 
relatively minor (administrative costs of less than $10,000 per 
consultation effort) and would not be significant (i.e., would not 
exceed $100 million in a single year).
    We are soliciting data and comments from the public on the DEA 
discussed above. During the development of a final designation, we will 
consider the information presented in the DEA and any additional 
information on economic impacts we receive 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 424.19. We may 
exclude an area from critical habitat if we determine that the benefits 
of

[[Page 16814]]

excluding the area outweigh the benefits of including the area, 
provided the exclusion will not result in the extinction of this 
species.

Consideration of National Security Impacts or Homeland Security Impacts

    Section 4(a)(3)(B)(i) of the Act may not cover all DoD lands or 
areas that pose potential national-security concerns (e.g., a DoD 
installation that is in the process of revising its INRMP for a newly 
listed species or a species previously not covered). If a particular 
area is not covered under section 4(a)(3)(B)(i), national-security or 
homeland-security concerns are not a factor in the process of 
determining what areas meet the definition of ``critical habitat.'' 
However, the Service must consider impacts on national security, 
including homeland security, on those lands or areas not covered by 
section 4(a)(3)(B)(i) because section 4(b)(2) requires the Service to 
consider those impacts whenever it designates critical habitat. 
Accordingly, if DoD, Department of Homeland Security (DHS), or another 
Federal agency has requested exclusion based on an assertion of 
national-security or homeland-security concerns, or we have otherwise 
identified national-security or homeland-security impacts from 
designating particular areas as critical habitat, we generally have 
reason to consider excluding those areas.
    However, we cannot automatically exclude requested areas. When DoD, 
DHS, or another Federal agency requests exclusion from critical habitat 
on the basis of national-security or homeland-security impacts, we must 
conduct an exclusion analysis if the Federal requester provides 
information, including a reasonably specific justification of an 
incremental impact on national security that would result from the 
designation of that specific area as critical habitat. That 
justification could include demonstration of probable impacts, such as 
impacts to ongoing border-security patrols and surveillance activities, 
or a delay in training or facility construction, as a result of 
compliance with section 7(a)(2) of the Act. If the agency requesting 
the exclusion does not provide us with a reasonably specific 
justification, we will contact the agency to recommend that it provide 
a specific justification or clarification of its concerns relative to 
the probable incremental impact that could result from the designation. 
If we conduct an exclusion analysis because the agency provides a 
reasonably specific justification or because we decide to exercise the 
discretion to conduct an exclusion analysis, we will defer to the 
expert judgment of DoD, DHS, or another Federal agency as to: (1) 
Whether activities on its lands or waters, or its activities on other 
lands or waters, have national-security or homeland-security 
implications; (2) the importance of those implications; and (3) the 
degree to which the cited implications would be adversely affected in 
the absence of an exclusion. In that circumstance, in conducting a 
discretionary section 4(b)(2) exclusion analysis, we will give great 
weight to national-security and homeland-security concerns in analyzing 
the benefits of exclusion.
    In preparing this proposal, we have determined that the lands 
within the proposed designations of critical habitat for Texas 
heelsplitter and Louisiana pigtoe are not owned or managed by the DoD 
or DHS, and, therefore, we anticipate no impact on national security or 
homeland security.

Consideration of 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 discussed above. To identify other relevant impacts that may 
affect the exclusion analysis, 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 (SHAs), or 
candidate conservation agreements with assurances (CCAAs)--or whether 
there are non-permitted conservation agreements and partnerships that 
may be impaired by designation of, or exclusion from, critical habitat. 
In addition, we look at whether Tribal conservation plans or 
partnerships, Tribal resources, or government-to-government 
relationships of the United States with Tribal entities may be affected 
by the designation. We also consider any State, local, social, or other 
impacts that might occur because of the designation.
    When analyzing other relevant impacts of including a particular 
area in a designation of critical habitat, we weigh those impacts 
relative to the conservation value of the particular area. To determine 
the conservation value of designating a particular area, we consider a 
number of factors, including, but not limited to, the additional 
regulatory benefits that the area would receive due to the protection 
from destruction or adverse modification as a result of actions with a 
Federal nexus, the educational benefits of mapping essential habitat 
for recovery of the listed species, and any benefits that may result 
from a designation due to State or Federal laws that may apply to 
critical habitat.
    In the case of the Texas heelsplitter and Louisiana pigtoe, the 
benefits of critical habitat include public awareness of the presence 
of these species and the importance of habitat protection, and, where a 
Federal nexus exists, increased habitat protection for the Texas 
heelsplitter and Louisiana pigtoe due to protection from destruction or 
adverse modification of critical habitat. Continued implementation of 
an ongoing management plan that provides conservation equal to or more 
than the protections that result from a critical habitat designation 
would reduce those benefits of including that specific area in the 
critical habitat designation.
    We evaluate the existence of a conservation plan when considering 
the benefits of inclusion. We consider a variety of factors, including, 
but not limited to, whether the plan is finalized; how it provides for 
the conservation of the essential physical or biological features; 
whether there is a reasonable expectation that the conservation 
management strategies and actions contained in a management plan will 
be implemented into the future; whether the conservation strategies in 
the plan are likely to be effective; and whether the plan contains a 
monitoring program or adaptive management to ensure that the 
conservation measures are effective and can be adapted in the future in 
response to new information.
    After identifying the benefits of inclusion and the benefits of 
exclusion, we carefully weigh the two sides to evaluate whether the 
benefits of exclusion outweigh those of inclusion. If our analysis 
indicates that the benefits of exclusion outweigh the benefits of 
inclusion, we then determine whether exclusion would result in 
extinction of the species. If exclusion of an area from critical 
habitat will result in extinction, we will not exclude it from the 
designation.

Private or Other Non-Federal Conservation Plans Related to Permits 
Under Section 10 of the Act

    HCPs for incidental take permits under section 10(a)(1)(B) of the 
Act provide for partnerships with non-Federal entities to minimize and 
mitigate impacts to listed species and their habitat. In some cases, 
HCP permittees agree to do more for the conservation of the species and 
their habitats on private lands than designation of critical habitat 
would provide alone. We place great value on the partnerships that are 
developed

[[Page 16815]]

during the preparation and implementation of HCPs.
    CCAAs and SHAs are voluntary agreements designed to conserve 
candidate and listed species, respectively, on non-Federal lands. In 
exchange for actions that contribute to the conservation of species on 
non-Federal lands, participating property owners are covered by an 
``enhancement of survival'' permit under section 10(a)(1)(A) of the 
Act, which authorizes incidental take of the covered species that may 
result from implementation of conservation actions, specific land uses, 
and, in the case of SHAs, the option to return to a baseline condition 
under the agreements. We also provide enrollees assurances that we will 
not impose further land-, water-, or resource-use restrictions, or 
require additional commitments of land, water, or finances, beyond 
those agreed to in the agreements.
    When we undertake a discretionary section 4(b)(2) exclusion 
analysis based on permitted conservation plans such as CCAAs, SHAs, and 
HCPs, we consider the following three factors:
    (i) Whether the permittee is properly implementing the conservation 
plan or agreement;
    (ii) Whether the species for which critical habitat is being 
designated is a covered species in the conservation plan or agreement; 
and
    (iii) Whether the conservation plan or agreement specifically 
addresses the habitat of the species for which critical habitat is 
being designated and meets the conservation needs of the species in the 
planning area.
    In preparing this proposal, we have determined that there are 
currently no HCPs or other management plans for the Texas heelsplitter 
or Louisiana pigtoe. The proposed designation of critical habitat for 
the Louisiana pigtoe includes the Choctaw Reservation in Oklahoma, but 
not any lands held in trust for the tribe, or owned or managed by the 
tribe. No Tribal lands fall within the range of the Texas heelsplitter 
or the boundaries of the proposed critical habitat designations. 
Therefore the proposed designations do not include any Tribal lands or 
trust resources. We anticipate no impact on Tribal lands, partnerships, 
or HCPs from the proposed critical habitat designations.
    We are currently working with the Sabine River Authority of 
Louisiana, State of Louisiana, and Sabine River Authority of Texas to 
develop CCAAs that address activities conducted by the River 
Authorities and States with conservation measures specifically designed 
to provide a net conservation benefit to the covered species, including 
the Texas heelsplitter and Louisiana pigtoe, in the covered area for 
the term for each of the CCAAs. We are also working with the Trinity 
River Authority of Texas to develop a CCAA that would address 
activities conducted by the Trinity River Authority and State with 
conservation measures specifically designed to provide a net 
conservation benefit to the covered species, including the Texas 
heelsplitter, in the covered area for the term of the CCAA. 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.

Summary of Exclusions Considered Under Section 4(b)(2) of the Act

    At this time, we are not considering any exclusions from the 
proposed designations based on economic impacts, national security 
impacts, or other relevant impacts--such as partnerships, management, 
or protection afforded by cooperative management efforts--under section 
4(b)(2) of the Act. In preparing this proposal, we have determined that 
the proposed designation of critical habitat for the Louisiana pigtoe 
includes Choctaw Reservation in Oklahoma, but not any lands held in 
trust for the Tribe, or owned or managed by the Tribe. No tribal lands 
fall within the range of the Texas heelsplitter or the boundaries of 
the proposed critical habitat designations. Therefore we have 
determined that no HCPs or other management plans for the Texas 
heelsplitter or Louisiana pigtoe currently exist, and the proposed 
designations do not include any Tribal lands or trust resources. 
Therefore, we anticipate no impact on Tribal lands, partnerships, or 
HCPs from the proposed critical habitat designations, and, thus, as 
described above, we are not considering excluding any particular areas 
on the basis of the presence of conservation agreements or impacts to 
trust resources. Some areas within the proposed designations are 
included in proposed CCAAs. If finalized, we will consider the lands 
covered in the CCAAs for exclusion in the development of the final 
designations. However, we have contacted the Choctaw Nation of Oklahoma 
to request information on any possible impacts and will include such 
information in our final review.
    If through the public comment period we receive information that we 
determine indicates that there are economic, national security or other 
relevant impacts from designating particular areas as critical habitat, 
then as part of developing the final designation of critical habitat, 
we will evaluate that information and may 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 
424.19. If we receive a request for exclusion of a particular area and 
after evaluation of supporting information we do not exclude, we will 
fully explain our decision in the final rule for this action. (Please 
see ADDRESSES, above, for instructions on how to submit comments).

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 proposed 
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

[[Page 16816]]

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 proposed 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 
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 whether 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 light of recent 
court decisions, Federal agencies are required to evaluate the 
potential incremental impacts of rulemaking on those entities directly 
regulated by the rulemaking itself; in other words, the RFA does not 
require agencies 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. The 
RFA does not require evaluation of 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 made final 
as proposed, 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 would 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. Facilities that provide energy supply, distribution, 
or use occur within some units of the proposed critical habitat 
designations (for example, dams, pipelines) and may potentially be 
affected. We determined that consultations, technical assistance, and 
requests for species lists may be necessary in some instances. In our 
economic analysis, we did not find that the proposed critical habitat 
designations would 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 finding:
    (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 designation of critical habitat does 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

[[Page 16817]]

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 vast majority of the 
lands being proposed for critical habitat designation are owned by the 
Federal Government; States of Arkansas, Louisiana, Mississippi, 
Oklahoma, and Texas; and private individuals. These entities do not fit 
the definition of ``small governmental jurisdiction.'' One proposed 
unit (TXHS-2a) includes a very small portion of land owned by the local 
government, but that is only 1 percent of that one unit. 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 Texas heelsplitter and Louisiana pigtoe 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 critical habitat. A takings 
implications assessment has been completed for the proposed designation 
of critical habitat for the Texas heelsplitter and the Louisiana 
pigtoe, and it concludes that, if adopted, these designations of 
critical habitat do 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 the proposed critical habitat designations 
with, appropriate State resource agencies. 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 for 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 State and local 
governments in long-range planning because they 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) of the Act 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 proposed rule would 
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 physical or biological 
features essential to the conservation of the species. The proposed 
areas of 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 proposed 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 regulations 
adopted pursuant to section 4(a) of 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)). However, 
when the range of the species includes States within the Tenth Circuit, 
such as that of the Louisiana pigtoe, under the Tenth Circuit ruling in 
Catron County Board of Commissioners v. U.S. Fish and Wildlife Service, 
75 F.3d 1429 (10th Cir. 1996), we undertake a NEPA analysis for 
critical habitat designation. We invite the public to comment on the 
extent to which these proposed critical habitat designations may have a 
significant impact on the human environment or fall within one of the 
categorical exclusions for actions that have no individual or 
cumulative effect on the quality of the human environment. We will 
complete our analysis, in compliance with NEPA, before making a final 
determination on this proposed rule.

[[Page 16818]]

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 federally recognized 
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 for 
the Texas heelsplitter or Louisiana pigtoe, 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 https://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 Fish and Wildlife Service's Species Assessment Team and the 
Arlington Ecological Services Field Office.

List of Subjects in 50 CFR Part 17

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

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 ``Heelsplitter, Texas'' 
and ``Pigtoe, Louisiana'' 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) * * *

----------------------------------------------------------------------------------------------------------------
                                                                                          Listing citations and
           Common name              Scientific name      Where listed         Status         applicable rules
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
              Clams
 
                                                  * * * * * * *
Heelsplitter, Texas.............  Potamilus           Wherever found....  E              [Federal Register
                                   amphichaenus.                                          citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.95(f).\CH\
 
                                                  * * * * * * *
Pigtoe, Louisiana...............  Pleurobema          Wherever found....  T              [Federal Register
                                   riddellii.                                             citation when
                                                                                          published as a final
                                                                                          rule]; 50 CFR
                                                                                          17.45(g); \4d\ 50 CFR
                                                                                          17.95(f).\CH\
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

0
3. Further amend Sec.  17.45, as proposed to be amended on September 
29, 2020, at 85 FR 61384, on August 26, 2021, at 86 FR 47916, and on 
September 7, 2021, at 86 FR 50010, and by adding paragraphs (f) and (g) 
to read as follows:


Sec.  17.45  Special rules--snails and clams.

* * * * *
    (f) [Reserved]
    (g) Louisiana pigtoe (Pleurobema riddellii).
    (1) Prohibitions. The following prohibitions that apply to 
endangered wildlife also apply to the Louisiana pigtoe. Except as 
provided under paragraph (g)(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 Louisiana pigtoe:
    (i) Import or export, as set forth at Sec.  17.21(b) for endangered 
wildlife.
    (ii) Take, as set forth at Sec.  17.21(c)(1) for endangered 
wildlife.
    (iii) Possession and other acts with unlawfully taken specimens, as 
set forth at Sec.  17.21(d)(1) for endangered wildlife.
    (iv) Interstate or foreign commerce in the course of commercial 
activity, as set forth at Sec.  17.21(e) for endangered wildlife.
    (v) Sale or offer for sale, as set forth at Sec.  17.21(f) for 
endangered wildlife.
    (2) Exceptions from prohibitions. In 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 
wildlife, as set forth at Sec.  17.21(d)(2) for endangered wildlife.
    (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 native stakes (live, vegetative cuttings inserted or tamped into 
the ground in a manner that allows the stake to take root and grow), 
live native fascines (live branch cuttings, usually willows, bound 
together into long, cigar-shaped bundles), or native brush layering 
(cuttings or branches of easily rooted tree species layered between 
successive lifts of soil fill). These methods must 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

[[Page 16819]]

into the stream, work using these bioengineering methods must 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 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. We recommend that these practices and activities 
comply with specifications and technical guidelines developed by the 
U.S. Department of Agriculture's Natural Resources Conservation 
Service.
0
4. Amend Sec.  17.95(f) by adding an entry for ``Texas Heelsplitter 
(Potamilus amphichaenus)'' after the entry for ``Carolina Heelsplitter 
(Lasmigona decorata)'', and by adding an entry for ``Louisiana Pigtoe 
(Pleurobema riddellii)'' after the entry for ``Georgia Pigtoe 
(Pleurobema hanleyianum)'', to read as follows:


Sec.  17.95  Critical habitat--fish and wildlife.

* * * * *
    (f) Clams and Snails.
* * * * *
Texas Heelsplitter (Potamilus amphichaenus)
    (1) Critical habitat units are depicted for Anderson, Angelina, 
Cherokee, Ellis, Freestone, Gregg, Grimes, Hardin, Harrison, Henderson, 
Houston, Jasper, Jefferson, Kaufman, Leon, Madison, Navarro, Orange, 
Panola, Polk, Rains, Rusk, Sabine, Shelby, Smith, Trinity, Tyler, 
Upshur, Van Zandt, Walker, and Wood Counties, Texas, on the maps in 
this entry.
    (2) Within these areas, the physical or biological features 
essential to the conservation of Texas heelsplitter consist of the 
following components within impoundments and streambeds:
    (i) Water quality parameters within the following ranges:
    (A) Water temperature below 27 [deg]C (80.6 [deg]F);
    (B) Dissolved oxygen levels greater than 3 milligrams per liter 
(mg/L);
    (C) Low salinity (less than 2 parts per thousand) and total 
dissolved solids;
    (D) Low total ammonia and nitrogen (below 0.3-0.7 mg/L total 
ammonia nitrogen);
    (E) Low levels of copper, nickel, and other trace metals;
    (F) Low levels of pesticides, sulfate, chloride, potassium, and 
other harmful constituents; and
    (G) Low pollutants and environmental contaminants common to 
wastewater.
    (ii) Moderately flowing water rates suitable to prevent excess 
sedimentation but not so high as to dislodge individuals or sediment; 
or no water flow, if in an impoundment (lake, reservoir, or pool 
without flow).
    (iii) Substrate including bedrock and boulder crevices, point bars, 
and vegetated run habitat comprising sand, gravel, and larger cobbles.
    (iv) Freshwater drum (Aplodinotus grunniens) present.
    (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 
the effective date of the final rule.
    (4) Data layers defining map units were created on a base of U.S. 
Geological Survey digital ortho-photo quarter-quadrangles, and critical 
habitat units were then mapped using Universal Transverse Mercator 
(UTM) Zone 14N coordinates. 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 the Service's internet 
site at https://www.fws.gov/office/arlington-ecological-services, at 
https://www.regulations.gov at Docket No. FWS-R2-ES-2022-0026, and at 
the field office responsible for this designation. You may obtain field 
office location information by contacting one of the Service regional 
offices, the addresses of which are listed at 50 CFR 2.2.
    (5) Index map of critical habitat units for the Texas heelsplitter 
follows:

Figure 1 to Texas Heelsplitter (Potamilus amphichaenus) paragraph (5)
BILLING CODE 4333-15-P

[[Page 16820]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.024

    (6) Unit TXHS-1: Trinity River Unit; Anderson, Ellis, Freestone, 
Grimes, Henderson, Houston, Kaufman, Leon, Madison, Navarro, and Walker 
Counties, Texas.
    (i) Unit TXHS-1 consists of two subunits:
    (A) Subunit TXHS-1a (Trinity River) is comprised of 212.8 river 
miles (mi) (342.4 kilometers (km)) in Anderson, Ellis, Freestone, 
Henderson, Houston, Kaufman, Leon, Madison, and Navarro Counties, 
Texas. This subunit is composed of lands in State (5 percent) and 
private (95 percent) ownership.
    (B) Subunit TXHS-1b (Bedias Creek) is comprised of 28.9 river mi 
(46.5 km) in Grimes, Madison, and Walker Counties, Texas. All of the 
riparian lands that border this subunit are in private ownership.
    (ii) Unit TXHS-1 includes stream channel up to bankfull height.
    (iii) Map of Unit TXHS-1 follows:

Figure 2 to Texas Heelsplitter (Potamilus amphichaenus) paragraph 
(6)(iii)

[[Page 16821]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.025

    (7) Unit TXHS-2: Sabine River Unit; Gregg, Harrison, Panola, Rains, 
Rusk, Sabine, Shelby, Smith, Upshur, Van Zandt, and Wood Counties, 
Texas.
    (i) Unit TXHS-2 consists of three subunits:
    (A) Subunit TXHS-2a (Upper Sabine River) is comprised of 237.4 
river mi (382 km) in Gregg, Harrison, Panola, Rains, Rusk, Smith, 
Upshur, Van Zandt, and Wood Counties, Texas. The riparian lands that 
border this subunit include Federal (2 percent), State (4 percent), 
local (1 percent), and private (93 percent) ownership.
    (B) Subunit TXHS-2b (Lake Fork Creek) consists of 13.8 river mi 
(22.2 km) in Wood County, Texas. All of the riparian lands that border 
this subunit are in private ownership.
    (C) Subunit TXHS-2c (Patroon Bayou) includes 19.9 river mi (32 km) 
in Sabine and Shelby Counties, Texas. The riparian lands that border 
this subunit are in Federal (7 percent) and private (93 percent) 
ownership.
    (ii) Unit TXHS-2 includes stream channel up to bankfull height.
    (iii) Map of Unit TXHS-2 follows:

Figure 3 to Texas Heelsplitter (Potamilus amphichaenus) paragraph 
(7)(iii)

[[Page 16822]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.026

    (8) Unit TXHS-3: Neches River Unit; Anderson, Angelina, Cherokee, 
Hardin, Houston, Jasper, Jefferson, Orange, Polk, Trinity, and Tyler 
Counties, Texas.
    (i) Unit TXHS-3 consists of three subunits:
    (A) Subunit TXHS-3a (Upper Neches River) is comprised of 227.9 
river mi (366.7 km) of stream in Anderson, Angelina, Cherokee, Houston, 
Jasper, Polk, Trinity, and Tyler Counties, Texas. The riparian lands 
that border this subunit are in Federal (12 percent) and private (88 
percent) ownership.
    (B) Subunit TXHS-3b (Lower Angelina River) consists of 14.7 river 
mi (23.7 km) in Jasper County, Texas. The riparian lands that border 
this subunit are in Federal (11 percent) and private (89 percent) 
ownership.
    (C) Subunit TXHS-3c (Lower Neches River) includes 76.3 river mi 
(122.8 km) in Hardin, Jasper, Jefferson, Orange, and Tyler Counties, 
Texas. The riparian lands that border this subunit are in Federal (5 
percent), State (7 percent), and private (88 percent) ownership.
    (ii) Unit TXHS-3 includes stream channel up to bankfull height.
    (iii) Map of Unit TXHS-3 follows:

Figure 4 to Texas Heelsplitter (Potamilus amphichaenus) paragraph 
(8)(iii)

[[Page 16823]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.027

* * * * *
Louisiana Pigtoe (Pleurobema riddellii)
    (1) Critical habitat units are depicted for Howard, Little River, 
and Sevier Counties, Arkansas; Allen, Beauregard, Rapides, St. Tammany, 
Vernon, and Washington parishes, Louisiana; Marion and Pearl River 
Counties, Mississippi; McCurtain County, Oklahoma; and Anderson, 
Angelina, Cherokee, Gregg, Hardin, Harrison, Houston, Jasper, 
Jefferson, Liberty, Montgomery, Nacogdoches, Orange, Panola, Polk, 
Rusk, Smith, Trinity, Tyler, Upshur, and Wood Counties, Texas, on the 
maps in this entry.
    (2) Within this area, the physical or biological features essential 
to the conservation of Louisiana pigtoe consist of the following 
components within streambeds:
    (i) Water quality parameters within the following ranges:
    (A) Water temperature below 27 [deg]C (80.6 [deg]F);
    (B) Dissolved oxygen levels greater than 3 milligrams per liter 
(mg/L);
    (C) Low salinity (less than 2 parts per thousand) and total 
dissolved solids;
    (D) Low total ammonia and nitrogen (below 0.3-0.7 mg/L total 
ammonia nitrogen);

[[Page 16824]]

    (E) Low levels of copper, nickel, and other trace metals;
    (F) Low levels of pesticides, sulfate, chloride, potassium, and 
other harmful constituents; and
    (G) Low pollutants and environmental contaminants common to 
wastewater.
    (ii) Moderately flowing water rates suitable to prevent excess 
sedimentation but not so high as to dislodge individuals or sediment.
    (iii) Stable bank and riffle habitats with bedrock and boulder 
crevices, point bars, and vegetated run habitat comprising sand, 
gravel, and larger cobbles.
    (iv) Red shiner (Cyprinella (=Notropis) lutrensis), blacktail 
shiner (Cyprinella venusta), and bullhead minnow (Pimephales vigilax) 
present.
    (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 
the effective date of the final rule.
    (4) Data layers defining map units were created on a base of U.S. 
Geological Survey digital ortho-photo quarter-quadrangles, and critical 
habitat units were then mapped using Universal Transverse Mercator 
(UTM) Zone 14N coordinates. 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 the Service's internet 
site at https://www.fws.gov/office/arlington-ecological-services, at 
https://www.regulations.gov at Docket No. FWS-R2-ES-2022-0026, and at 
the field office responsible for this designation. You may obtain field 
office location information by contacting one of the Service regional 
offices, the addresses of which are listed at 50 CFR 2.2.
    (5) Index map of critical habitat units for the Louisiana pigtoe 
follows:

Figure 1 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (5)

[[Page 16825]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.028

    (6) Unit LAPT-1: Little River Unit; Howard, Little River, and 
Sevier Counties, Arkansas, and McCurtain County, Oklahoma.
    (i) Unit LAPT-1 consists of four subunits:
    (A) Subunit LAPT-1a (Upper Little River) is comprised of consists 
of approximately 88 river miles (mi) (141.6 kilometers (km)) in Little 
River and Sevier Counties, Arkansas, and McCurtain County, Oklahoma. 
The riparian lands that border this subunit are in Federal (26 
percent), State (1 percent), and private (42 percent) ownership, and 
private land with the Choctaw Reservation (23 percent), but not any 
lands held in trust for the Tribe, or owned or managed by the Tribe.
    (B) Subunit LAPT-1b (Rolling Fork) is comprised of 29.9 river mi 
(47.9 km) in Sevier County, Arkansas. All of the riparian lands that 
border this subunit are in private ownership.
    (C) Subunit LAPT-1c (Cossatot River) includes 47.2 river mi (75.9 
km) in Sevier County, Arkansas. The riparian lands that border this 
subunit are in Federal (15 percent) and private (85 percent) ownership.
    (D) Subunit LAPT-1d (Saline River) consists of 42.6 river mi (68.5 
km) along the Howard/Sevier County line in southeast Arkansas. All of 
the riparian

[[Page 16826]]

lands in this subunit are in private ownership.
    (ii) Unit LAPT-1 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-1 follows:

Figure 2 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (6)(iii)
[GRAPHIC] [TIFF OMITTED] TP20MR23.029

    (7) Unit LAPT-2: Sabine River Unit; Beauregard and Vernon parishes, 
Louisiana, and Gregg, Harrison, Panola, Rusk, Smith, Upshur, and Wood 
Counties, Texas.
    (i) Unit LAPT-2 consists of two subunits:
    (A) Subunit LAPT-2a (Upper Sabine River) consists of 110.1 river mi 
(177.2 km) in Gregg, Harrison, Panola, Rusk, Smith, Upshur, and Wood 
Counties, Texas. The riparian lands that border this subunit are in 
Federal (2 percent), State (2 percent), and private (96 percent) 
ownership.
    (B) Subunit LAPT-2b (Anacoco Bayou) includes 12.2 river mi (19.6 
km)

[[Page 16827]]

in Vernon and Beauregard parishes, Louisiana. All of the riparian lands 
that border this subunit are in private ownership.
    (ii) Unit LAPT-2 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-2 follows:

Figure 3 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (7)(iii)
[GRAPHIC] [TIFF OMITTED] TP20MR23.030

    (8) Unit LAPT-3: Neches River Unit; Anderson, Angelina, Cherokee, 
Hardin, Houston, Jasper, Jefferson, Nacogdoches, Orange, Polk, Trinity, 
and Tyler Counties, Texas.
    (i) Unit LAPT-3 consists of five subunits:
    (A) Subunit LAPT-3a (Upper Neches River) consists of 200.4 river mi 
(322.4 km) through parts of Anderson, Angelina, Cherokee, Houston, 
Polk, Trinity, and Tyler Counties, Texas. The riparian lands that 
border this subunit are in Federal (11 percent) and private (89 
percent) ownership.

[[Page 16828]]

    (B) Subunit LAPT-3b (Upper Angelina River) consists of 67.4 river 
mi (108.4 km) in Angelina, Cherokee, and Nacogdoches Counties, Texas. 
The riparian lands that border this subunit are in Federal (50 percent) 
and private (50 percent) ownership.
    (C) Subunit LAPT-3c (Lower Neches River) includes 76.2 river mi 
(122.6 km) in Hardin, Jasper, Jefferson, Orange, and Tyler Counties, 
Texas. The riparian lands that border this subunit are in Federal (5 
percent), State (7 percent), and private (88 percent) ownership.
    (D) Subunit LAPT-3d (Village Creek) consists of 54.9 river mi (88.3 
km) of stream in Hardin County, Texas. The riparian lands that border 
this subunit are in Federal (78 percent), State (2 percent), and 
private (20 percent) ownership.
    (E) Subunit LAPT-3e (Big Sandy Creek) consists of 43.7 river mi 
(70.3 km) of stream in Hardin, Polk, and Tyler Counties, Texas. The 
riparian lands that border this subunit are in Federal (95 percent) and 
private (5 percent) ownership.
    (ii) Unit LAPT-3 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-3 follows:

Figure 4 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (8)(iii)

[[Page 16829]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.031

    (9) Unit LAPT-4: East Fork San Jacinto River Unit; Liberty and 
Montgomery Counties, Texas.
    (i) Unit LAPT-4 consists of 23.3 river mi (37.5 km) in Liberty and 
Montgomery Counties, Texas. All of the riparian lands that border this 
unit are in private ownership.
    (ii) Unit LAPT-4 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-4 follows:

Figure 5 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (9)(iii)

[[Page 16830]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.032

    (10) Unit LAPT-5: Calcasieu River Unit; Allen, Rapides, and Vernon 
parishes, Louisiana.
    (i) Unit LAPT-5 consists of three subunits:
    (A) Subunit LAPT-5a (Upper Calcasieu River) includes 92 river mi 
(148 km) in Allen and Rapides parishes, Louisiana. The riparian lands 
that border this subunit are in Federal (22 percent) and private (78 
percent) ownership.
    (B) Subunit LAPT-5b (Whisky Chitto Creek) includes 21.7 river mi 
(34.9 km) in Allen Parish, Louisiana. The riparian lands that border 
this subunit are in State (99 percent) and private (1 percent) 
ownership.
    (C) Subunit LAPT-5c (Tenmile Creek) consists of 32 river mi (51.5 
km) in Allen, Rapides, and Vernon parishes, Louisiana. The riparian 
lands that border the subunit are in State (2 percent) and private (98 
percent) ownership.
    (ii) Unit LAPT-5 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-5 follows:

Figure 6 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (10)(iii)

[[Page 16831]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.033

    (11) Unit LAPT-6: Pearl River Unit; St. Tammany and Washington 
parishes, Louisiana, and Marion and Pearl River Counties, Mississippi.
    (i) Unit LAPT-6 consists of 86.6 river mi (139.3 km) in St. Tammany 
and Washington parishes, Louisiana, and Marion and Pearl River 
Counties, Mississippi. The riparian lands that border this unit are in 
Federal (42 percent), State (14 percent), and private (44 percent) 
ownership.
    (ii) Unit LAPT-6 includes stream channel up to bankfull height.
    (iii) Map of Unit LAPT-6 follows:

Figure 7 to Louisiana Pigtoe (Pleurobema riddellii) paragraph (11)(iii)

[[Page 16832]]

[GRAPHIC] [TIFF OMITTED] TP20MR23.034

* * * * *

Martha Williams,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2023-05107 Filed 3-17-23; 8:45 am]
BILLING CODE 4333-15-C