[Federal Register Volume 80, Number 194 (Wednesday, October 7, 2015)]
[Proposed Rules]
[Pages 60753-60783]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-24900]



[[Page 60753]]

Vol. 80

Wednesday,

No. 194

October 7, 2015

Part II





Department of the Interior





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Fish and Wildlife Service





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50 CFR Part 17





Endangered and Threatened Wildlife and Plants; Threatened Species 
Status for the Headwater Chub and a Distinct Population Segment of the 
Roundtail Chub; Proposed Rule

Federal Register / Vol. 80 , No. 194 / Wednesday, October 7, 2015 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2015-0148; 4500030113]
RIN 1018-BA86


Endangered and Threatened Wildlife and Plants; Threatened Species 
Status for the Headwater Chub and a Distinct Population Segment of the 
Roundtail Chub

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 headwater chub (Gila nigra) and a distinct population segment 
(DPS) of the roundtail chub (Gila robusta) from the lower Colorado 
River basin as threatened species under the Endangered Species Act 
(Act). If we finalize this rule as proposed, it would extend the Act's 
protections to this species and DPS.

DATES: We will accept comments received or postmarked on or before 
December 7, 2015. 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. We must receive requests for 
public hearings, in writing, at the address shown in FOR FURTHER 
INFORMATION CONTACT by November 23, 2015.

ADDRESSES: You may submit comments by one of the following methods:
    (1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. In the Search box, enter FWS-R2-ES-2015-0148, 
which is the docket number for this rulemaking. Then click on the 
Search button. On the resulting page, in the Search panel on the left 
side of the screen, under the Document Type heading, click on the 
Proposed Rules link to locate this document. You may submit a comment 
by clicking on ``Comment Now!''
    (2) By hard copy: Submit by U.S. mail or hand-delivery to: Public 
Comments Processing, Attn: FWS-R2-ES-2015-0148, U.S. Fish and Wildlife 
Service, MS: BPHC, 5275 Leesburg Pike, Falls Church, VA 22041-3803.
    We request that you send comments only by the methods described 
above. We will post all comments on http://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see Public Comments, below, for more information).

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, U.S. 
Fish and Wildlife Service, Arizona Ecological Services Office, 2321 
West Royal Palm Road, Suite 103, Phoenix, AZ 85021; telephone 602-242-
0210. Persons who use a telecommunications device for the deaf (TDD) 
may call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Executive Summary

    Why we need to publish a rule. Under the Act, if a species is 
determined to be an endangered or threatened species throughout all or 
a significant portion of its range, we are required to promptly publish 
a proposal in the Federal Register and make a determination on our 
proposal within 1 year. Listing a species as an endangered or 
threatened species can only be completed by issuing a rule.
    This rule proposes to list the headwater chub and the lower 
Colorado River basin roundtail chub DPS as threatened species. The 
headwater and lower Colorado River basin roundtail chub DPS are 
candidate species for which we have on file sufficient information on 
biological vulnerability and threats to support preparation of a 
listing proposal, but for which development of a listing regulation has 
been precluded by other higher priority listing activities. This rule 
reassesses all available information regarding the status of and 
threats to the headwater chub and lower Colorado River basin roundtail 
chub DPS.
    The basis for our action. Under the Act, we can determine that a 
species is an endangered or threatened species based on any of five 
factors: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence. We have determined that headwater chub and lower 
Colorado River basin roundtail chub DPS meet the definition of 
threatened species primarily because of the present or threatened 
destruction of their habitat or range and other natural or manmade 
factors resulting mainly from impacts from nonnative aquatic species, 
reduction of habitat (i.e., water availability), and climate change.
    We will seek peer review. We will seek comments from independent 
specialists to ensure that our determinations are based on 
scientifically sound data, assumptions, and analyses. We will invite 
these peer reviewers to comment on our listing proposal. Because we 
will consider all comments and information we receive during the 
comment period, our final determinations may differ from this proposal.

Information Requested

Public Comments

    We intend that any final action resulting from this proposed rule 
will be based on the best scientific and commercial data available, and 
be as accurate and as effective as possible. Therefore, we request 
comments or information from other concerned governmental agencies, 
Native American tribes, the scientific community, industry, or any 
other interested parties concerning this proposed rule. We particularly 
seek comments concerning:
    (1) The headwater and roundtail chubs' 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 range, including distribution patterns;
    (d) Historical and current population levels, and current and 
projected trends; and
    (e) Past and ongoing conservation measures for the species, their 
habitats, or both.
    (2) Factors that may affect the continued existence of the species, 
which may include habitat modification or destruction, overutilization, 
disease, predation, the inadequacy of existing regulatory mechanisms, 
or other natural or manmade factors.
    (3) Biological, commercial trade, or other relevant data concerning 
any threats (or lack thereof) to these species and existing regulations 
that may be addressing those threats.
    (4) Additional information concerning the historical and current 
status, range, distribution, and population size of these species, 
including the locations of any additional populations of these species.
    (5) Information as to which prohibitions, and exceptions to those 
prohibitions, are necessary and advisable to provide for the 
conservation of the headwater chub or the lower Colorado River basin 
roundtail chub DPS pursuant to section 4(d) of the Act (16 U.S.C. 1531 
et seq.).
    We are also seeking comments regarding potential critical habitat 
designation for the headwater chub and

[[Page 60755]]

the lower Colorado River basin roundtail chub DPS. We particularly seek 
comments concerning:
    (1) The reasons why we should or should not designate habitat as 
``critical habitat'' under section 4 of the Act, including whether 
there are threats to the species from human activity, the degree of 
which can be expected to increase due to the designation, and whether 
that increase in threat outweighs the benefit of designation such that 
the designation of critical habitat may not be prudent.
    (2) Specific information on:
    (a) The amount and distribution of headwater chub and roundtail 
chub habitat;
    (b) What areas, that were occupied at the time of listing (or are 
currently occupied) and that contain features essential to the 
conservation of the species, should be included in the designation and 
why;
    (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) What areas not occupied at the time of listing are essential 
for the conservation of the species and why.
    (3) Land use designations and current or planned activities in the 
subject areas and their possible impacts on critical habitat.
    (4) Information on the projected and reasonably likely impacts of 
climate change on the headwater chub, the lower Colorado River basin 
roundtail chub DPS, and their habitats.
    (5) Any probable economic, national security, or other relevant 
impacts of designating any area that may be included in the proposed 
critical habitat designation; in particular, we seek comments on any 
impacts on small entities or families, and the benefits of including or 
excluding areas that exhibit these impacts.
    Please include sufficient information with your submission (such as 
scientific journal articles or other publications) to allow us to 
verify any scientific or commercial information you include.
    Please note that submissions merely stating support for or 
opposition to the action under consideration without providing 
supporting information, although noted, will not be considered in 
making a determination, as section 4(b)(1)(A) of the Act directs that 
determinations as to whether any species is an endangered or threatened 
species must be made ``solely on the basis of the best scientific and 
commercial data available.''
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section. We request 
that you send comments only by the methods described in the ADDRESSES 
section.
    If you submit information via http://www.regulations.gov, your 
entire submission--including any personal identifying information--will 
be posted on the Web site. If your submission is made via a hardcopy 
that includes personal identifying information, you may request at the 
top of your document that we withhold this information from public 
review. However, we cannot guarantee that we will be able to do so. We 
will post all hardcopy submissions on http://www.regulations.gov.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection on http://www.regulations.gov, or by 
appointment, during normal business hours, at the U.S. Fish and 
Wildlife Service, Arizona Ecological Services Field Office (see FOR 
FURTHER INFORMATION CONTACT).

Public Hearing

    Section 4(b)(5) of the Act provides for one or more public hearings 
on this proposal, if requested. Requests must be received within 45 
days after the date of publication of this proposed rule in the Federal 
Register (see DATES, above). Such requests must be sent to the address 
shown in the FOR FURTHER INFORMATION CONTACT section. We will schedule 
public hearings on this proposal, if any are requested, and announce 
the dates, times, and places of those hearings, as well as how to 
obtain reasonable accommodations, in the Federal Register and local 
newspapers at least 15 days before the hearing.

Peer Review

    In accordance with our joint policy on peer review published in the 
Federal Register on July 1, 1994 (59 FR 34270), we will seek expert 
opinions of at least three appropriate and independent specialists 
regarding this proposed rule. The purpose of peer review is to ensure 
that our listing determinations are based on scientifically sound data, 
assumptions, and analyses. The peer reviewers will have expertise in 
headwater and roundtail chub (or similar species) biology, life 
history, ecology, habitat, and other physical or biological factors.

Previous Federal Action

Headwater Chub

    On December 30, 1982 (47 FR 58454), we placed the headwater chub 
(as Gila robusta grahami) on the list of candidate species as a 
category 2 species. Category 2 species were those for which information 
in the Service's possession indicated that proposing to list was 
possibly appropriate, but for which substantial biological data to 
support a proposed rule were lacking. Headwater chub retained its 
category 2 candidate status until the practice of identifying category 
2 candidates was discontinued in the candidate notice of review (CNOR) 
published on February 28, 1996 (61 FR 7596). At that time, the 
headwater chub was removed from the candidate list and no longer 
recognized under the Act.
    On April 14, 2003, we received a petition from the Center for 
Biological Diversity to list the headwater chub (Gila nigra) as 
endangered or threatened and to designate critical habitat concurrently 
with the listing. Following receipt of the 2003 petition, and pursuant 
to a stipulated settlement agreement, we published a 90-day finding on 
July 12, 2005 (70 FR 39981), in which we found that the petitioners had 
provided sufficient information to indicate that listing of the 
headwater chub may be warranted. On May 3, 2006, we published our 12-
month finding (71 FR 26007) that listing was warranted, but precluded 
by higher priority listing actions, for the headwater chub. The species 
was subsequently included in all of our CNORs from 2006 through 2014 
(71 FR 53756, September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 
75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, 
November 10, 2010; 76 FR 66370, October 26, 2011; 77 FR 69994, November 
21, 2012; 78 FR 70104, November 22, 2013; 79 FR 72450, December 5, 
2014).

Lower Colorado River Basin Roundtail Chub DPS

    On December 30, 1982 (47 FR 58455), the roundtail chub was placed 
on the list of candidate species as a category 2 species. Roundtail 
chub retained its category 2 candidate status until the practice of 
identifying category 2 candidates was discontinued in the 1996 CNOR (61 
FR 7596; February 28, 1996). At that time, the roundtail chub was 
removed from the candidate list and no longer recognized under the Act.
    On April 14, 2003, we received a petition from the Center for 
Biological Diversity to list a distinct population segment (DPS) of the 
roundtail chub (Gila robusta) in the lower Colorado River basin 
(defined as all waters tributary to the Colorado River in Arizona and 
the portion of New Mexico in the Gila River and Zuni River basins)

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as endangered or threatened and to designate critical habitat 
concurrently. Following receipt of the 2003 petition, and pursuant to a 
stipulated settlement agreement, we published our 90-day finding on 
July 12, 2005 (70 FR 39981), that the petition presented substantial 
scientific information indicating that listing a DPS of the roundtail 
chub in the lower Colorado River basin may be warranted.
    On May 3, 2006, we published our 12-month finding (71 FR 26007) 
that listing of a DPS of the roundtail chub in the lower Colorado River 
basin was not warranted because it did not meet our definition of a 
DPS. On September 7, 2006, the Center for Biological Diversity 
challenged our decision not to list the lower Colorado River basin 
population of the roundtail chub as an endangered species under the 
Act. On November 5, 2007, in a stipulated settlement agreement, we 
agreed to commence a new status review of the lower Colorado River 
basin population segment of the roundtail chub and to submit a 12-month 
finding to the Federal Register by June 30, 2009.
    On July 7, 2009, we published a 12-month finding (74 FR 32352) on a 
petition to list a DPS of roundtail chub and found that the population 
segment satisfies the discreteness and significance elements of the 
Interagency Policy Regarding the Recognition of Distinct Vertebrate 
Population Segments Under the Act (DPS Policy) (February 7, 1996; 61 FR 
4722), and qualifies as a DPS. We further concluded that listing of the 
lower Colorado River basin DPS was warranted but precluded due to 
higher priority listing actions at the time. The DPS was subsequently 
included in all of our CNORs from 2009 through 2014 (74 FR 57804, 
November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 
26, 2011; 77 FR 69994, November 21, 2012; 78 FR 70104, November 22, 
2013; 79 FR 72450, December 5, 2014).
    The lower Colorado River basin DPS of roundtail chub is the 
candidate entity that is the subject of this proposed rule. The DPS 
includes the lower Colorado River and its tributaries downstream of 
Glen Canyon Dam, including the Gila and Zuni River basins in New 
Mexico.

Background

Species Information

Taxonomy
    Headwater chub was first described as a subspecies, G. grahami or 
G. robusta grahami, from Ash Creek and the San Carlos River in east-
central Arizona in 1874 (Cope and Yarrow 1875). In 2000, Minckley and 
DeMarais proposed full species status for headwater chub. The American 
Fisheries Society has accepted headwater chub (Gila nigra) as a full 
species (Nelson et al. 2004), as have the New Mexico Department of Game 
and Fish (Carmen 2006) and Arizona Game and Fish Department (Arizona 
Game and Fish Department 2006). As a consortium of fisheries 
scientists, the American Fisheries Society is the recognized and 
accepted scientific authority on fish taxonomy, and this is best 
commercial and scientific data available.
    Roundtail chub (Gila robusta) was first described by Baird and 
Girard (1853) from specimens collected in 1851 from the Zuni River 
(tributary to Little Colorado River), although that location may not be 
correct as Smith et al. (1979) reported the type locality was likely 
the mainstem Little Colorado River and Sublette et al. (1990) suggested 
the specimens may have been collected from the Rio Pescado (tributary 
to Zuni River) and incorrectly cited as the Zuni River. Roundtail chub 
has been recognized as a distinct species since the 1800s.
Biology and Habitat
I. Headwater Chub Biology and Habitat
    Headwater chubs are cyprinid fish (member of the minnow family 
Cyprinidae) with streamlined body shapes and are similar in appearance 
to the roundtail chub and the Gila chub (Gila intermedia). Adults range 
in size from 200-320 millimeters (mm) (8-12 inches (in)). Headwater 
chubs live for approximately 8 years and spawn from age 2 to 3 onward 
(Bestgen 1985, p. 65; Neve 1976, pp. 13, 15). Spawning typically occurs 
between April and May (Bestgen 1985, pp. 57-60; Brouder et al. 2000, 
pp. 12-13) but can occur as early as March (Neve 1976, pp. 13-14). 
Headwater chub are omnivorous, opportunistic feeders that consume 
plants, detritus, arthropods (aquatic and terrestrial), and fish.
    Headwater chubs occur in the middle to upper reaches of medium- to 
large-sized streams (Minckley and DeMarais 2000, p. 255) that are 
considered cool to warm water streams. Habitats in the Gila River 
containing headwater chubs consist of tributary and mainstem habitats 
at elevations of 1,325 meters (m) (4,347 feet (ft)) to 2,000 m (6,562 
ft) (Bestgen 1985, entire; Bestgen and Propst 1989, pp. 402-410). 
Typical adult habitats containing headwater chub consist of nearshore 
pools (greater than 1.8 m (6 ft.)), adjacent to swifter riffles and 
runs over sand and gravel substrate, with young-of-the-year and 
juveniles using smaller pools and areas with undercut banks and low 
velocity (Barrett 1992, p. 48; Barrett and Maughn 1995, p. 302; Bestgen 
and Propst 1989, pp. 402-410). Spawning typically occurs in pool-riffle 
areas with sandy-rocky substrates when water temperatures are between 
17-22 degrees Celsius ([deg]C) (63-72 degrees Fahrenheit ([deg]F)) 
(Bonar et al. 2011, p. 10; Bestgen 1985, p. 64; Bonar et al. 2011, p. 
11; Neve 1976, pp. 13-14). Snowmelt during late winter and early spring 
cues spawning and provides water temperatures suitable for spawning.
    In the lower Colorado River basin, several chub species are closely 
related genetically and closely resemble each other morphologically. 
This is likely the result of multiple independent hybridization events 
over time (Rinne 1976; Rosenfeld and Wilkinson 1989; DeMarais et al. 
1992; Dowling and DeMarais 1993; Minckley and DeMarais 2000; Gerber et 
al. 2001; Schwemm 2006; Sch[ouml]nhuth et al. 2014). Due to the 
similarities in morphology and genetics, identification of species in a 
stream is based on the geographic location of the stream in relation to 
other known chub streams. In headwater chub, most of their genetic 
variation occurs among populations, each of which tends to be 
distinctive. Genetic variation within headwater chub populations is 
consistent with the presumed multiple hybrid origins of this species 
(Dowling et al. 2008, p. 2).
II. Lower Colorado River Basin Roundtail Chub Biology and Habitat
    Roundtail chub are similar in appearance to Gila chub and headwater 
chub. Adults range in size from 225-350 mm (9-14 in) in length. 
Roundtail chub average life span is 8-10 years (Bezzerides and Bestgen 
2002, p. 21). Maturity of roundtail chub in the lower Colorado River 
population segment occurs between ages 3 and 5 years at 150-300 mm (6-
12 in) (Bezzerides and Bestgen 2002, p. 21; Brouder et al. 2000, p. 
12). In the lower Colorado River population segment, spawning occurs 
between April and May (Minckley 1981, p. 189; Bestgen 1985b, p. 7; 
Bryan et al. 2000, pp. 27-28; Bryan and Robinson 2000, pp. 20-21).
    Roundtail chub are found in cool to warm waters of rivers and 
streams, and often occupy the deepest pools and eddies present in the 
stream (Minckley 1973, p. 101; Brouder et al. 2000, pp. 6-8; Minckley 
and DeMarais 2000, p. 255; Bezzerides and Bestgen 2002, pp. 17-19). 
Adult roundtail chub favor slow-moving, deep pools. For cover they use 
large rocks, undercut banks, and woody debris (Bezzerides and Bestgen 
2002, p. 18; Brouder et al. 2000, pp. 6-7; Bryan

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and Hyatt 2004, p. 9). Spawning occurs in pool, run, and riffle 
habitats, with slow to moderate water velocities (Propst 1999, p. 24; 
Brouder et al. 2000, p. 12; Voeltz 2002, p. 16). Snowmelt during late 
winter and early spring cues spawning and provides water temperatures 
suitable for spawning. Roundtail chub larvae use low-velocity 
backwaters (Ruppert et al. 1993, p. 397). Young-of-the-year roundtail 
chub occupy shallow (less than 50 cm (20 in) depth) and low-velocity 
waters with vegetated shorelines (Brouder et al. 2000, pp. 6-8; Lanigan 
and Berry 1981, p. 392). Juveniles use habitat similar to young-of-the-
year but with depths less than 100 cm (40 in). Water temperatures of 
habitats occupied by roundtail chub vary seasonally between 0-32 [deg]C 
(32-90 [deg]F) (Bezzerides and Bestgen 2002, p. 19; Bonar et al. 2010, 
p. 3).
    There was historically greater connectivity and subsequent 
relatedness of roundtail chub over the lower Colorado River basin, and 
development of populations in isolation from other roundtail chub 
populations was not the normal condition across most of the historical 
range, except in the Bill Williams River and Little Colorado River 
drainages.

Roundtail Chub Lower Colorado River Distinct Population Segment

    Section 3(16) of the Act defines ``species'' to include any species 
or subspecies of fish and wildlife or plants, and any distinct 
population segment of any species of vertebrate fish or wildlife which 
interbreeds when mature (16 U.S.C. 1532(16)). To interpret and 
implement the distinct population segment provisions of the Act and 
congressional guidance, the Service and the National Marine Fisheries 
Service (now the National Oceanic and Atmospheric Administration--
Fisheries Service), published the Policy Regarding the Recognition of 
Distinct Vertebrate Population Segments (DPS Policy) in the Federal 
Register on February 7, 1996 (61 FR 4722). The DPS Policy sets forth a 
three-step process for considering if a population is a DPS: The Policy 
requires the Service first to determine whether a vertebrate population 
is discrete and, if the population is discrete, then to determine 
whether the population is significant. Lastly, if the population is 
determined to be both discrete and significant, then the DPS Policy 
requires the Service to evaluate the conservation status of the 
population to determine whether or not the DPS falls within the Act's 
definition of an ``endangered species'' or a ``threatened species.''
    In accordance with our DPS Policy, this section details our 
analysis of whether the vertebrate population segment under 
consideration for listing qualifies as a DPS, specifically, whether: 
(1) The population segment is discrete from the remainder of the 
species to which it belongs; and (2) the population is significant to 
the species to which it belongs. In our July 7, 2009, 12-month finding 
for roundtail chub (74 FR 32352) we found that the roundtail chub in 
the lower Colorado River basin (the lower Colorado River and its 
tributaries downstream of Glen Canyon Dam, including the Gila and Zuni 
River basins in New Mexico) met the definition of a DPS. In the 
following sections, we reaffirm that finding.

Discreteness

    Under the DPS Policy, a population segment of a vertebrate taxon 
may be considered discrete if it satisfies either one of the following 
conditions: (1) It is markedly separated from other populations of the 
same taxon as a consequence of physical, physiological, ecological, or 
behavioral factors (quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation); or (2) it is 
delimited by international governmental boundaries within which 
differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the Act. The potential 
DPS population of roundtail chub in the lower Colorado River basin is 
not delimited by international governmental boundaries. The following 
discussion considers whether the potential DPS population of roundtail 
chub in the lower Colorado River basin is markedly separated from other 
populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors.
    The historical range of roundtail chub included both the upper and 
lower Colorado River basins in the States of Wyoming, Utah, Colorado, 
New Mexico, Arizona, and Nevada (Propst 1999, p. 23; Bezzerides and 
Bestgen 2002, p. 25; Voeltz 2002, pp. 9-23), but the roundtail chub was 
likely only a transient in Nevada, so Nevada is not considered part of 
its range. Currently, roundtail chubs occur in both the upper and lower 
Colorado River basins in Wyoming, Utah, Colorado, New Mexico, and 
Arizona. Bezzerides and Bestgen (2002, p. 24) concluded that 
historically there were two discrete population centers, one in each of 
the lower and upper basins, and that these two population centers 
remain today. Numerous authors have noted that roundtail chub was very 
rare with few documented records in the mainstem Colorado River between 
the two basins (Minckley 1973, p. 102; Minckley 1979, p. 51; Valdez and 
Ryel 1994, pp. 5-10-5-11; Minckley 1996, p. 75; Bezzerides and Bestgen 
2002, pp. 24-25; Voeltz 2002, pp. 19, 112), so we do not consider the 
mainstem to have been occupied historically, and have not considered 
the Colorado River in our estimates of historical range. The 
information on historical distribution is clouded because early 
surveyors also variably used the term ``bonytail'' to describe 
roundtail chub (Valdez and Ryel 1994, pp. 5-7). The bonytail chub (Gila 
elegans) is a species in the mainstem Colorado River. Some historical 
accounts of roundtail chub in the mainstem may have, in fact, been 
bonytail chub. Records of roundtail chub from the mainstem Colorado 
River also may have been transients from nearby populations, such as 
some records from Grand Canyon, which may have been from the Little 
Colorado River (Voeltz 2002, p. 112). One record from between the two 
basins, a record of two roundtail chubs captured near Imperial Dam in 
1973, illustrates this. Upon examining these specimens, Minckley (1979, 
p. 51) concluded that they were strays washed downstream from the Bill 
Williams River based on their heavily blotched coloration. This is a 
logical conclusion considering that roundtail chub from the Bill 
Williams River typically exhibit this blotched coloration (Rinne 1969, 
pp. 20-21; Rinne 1976, p. 78). Minckley (1979, p. 51), Minckley (1996, 
p. 75), and Mueller and Marsh (2002, p. 40) also considered roundtail 
chub rare or essentially absent in the Colorado River mainstem based on 
the paucity of records from numerous surveys of the Colorado River 
mainstem.
    We conclude that, historically, roundtail chub occurred in the 
Colorado River basin in two population centers, one each in the upper 
(largely in Utah and Colorado, and to a lesser extent, in Wyoming and 
New Mexico) and lower basins (Arizona and New Mexico), with apparently 
little, if any, mixing of the two populations. If there was one 
population, we would expect to find a large number of records in the 
mainstem Colorado River between the San Juan and Bill Williams Rivers, 
but very few records of roundtail chub exist from this reach of stream. 
Also, there is a substantial distance between these areas of roundtail 
chub occurrence in the two basins. The mouth of the Escalante River, 
which contains the southernmost

[[Page 60758]]

population of roundtail chub in the upper basin, is approximately 443 
kilometers (km) (275 river miles (mi)) upstream from Grand Falls on the 
Little Colorado River, the historical downstream limit of the most 
northern population of the lower Colorado River basin. The lower 
Colorado River basin roundtail chub population segment meets the 
element of discreteness because it was separate historically, and 
continues to be markedly separate today.
    Additionally, in more recent times, the upper and lower basin 
populations of the roundtail chub have been physically separated by 
Glen Canyon Dam. That artificial separation is not the sole basis for 
our finding that the lower basin population is discrete from the upper 
basin population. The historical information on collections suggests 
that there was limited contact even before the dam was built. Available 
molecular information for the species, although sparse, seems to 
support this as genetic markers from roundtail chub in the Gila River 
basin are entirely absent from upper basin populations (Gerber et al. 
2001, p. 2028; see Significance discussion, below).
    Accordingly, we reaffirm our finding that the lower Colorado River 
basin population segment of roundtail chub is discrete from other 
populations of the species.

Significance

    Since we have determined that the roundtail chub in the lower 
Colorado River basin meet the discreteness element of the DPS Policy, 
we now consider the population segment's biological and ecological 
significance based on ``the available scientific evidence of the 
discrete population segment's importance to the taxon to which it 
belongs'' in light of congressional guidance that the authority to list 
DPSs be used ``sparingly'' while encouraging the conservation of 
genetic diversity (DPS Policy, 61 FR 4722; S. Rep. No. 96-151 (1979)).
    The DPS Policy describes four classes of information, or 
considerations, to take into account in evaluating a population 
segment's biological and ecological importance to the taxon to which it 
belongs. As precise circumstances are likely to vary considerably from 
case to case, the DPS policy does not state that these are the only 
classes of information that might factor into a determination of the 
biological and ecological importance of a discrete population. As 
specified in the DPS policy (61 FR 4722), consideration of the 
population segment's significance may include, but is not limited to, 
the following classes of information: (1) Persistence of the discrete 
population segment in an ecological setting that is unusual or unique 
for the taxon; (2) evidence that loss of the discrete population 
segment would result in a significant gap in the range of the taxon; 
(3) evidence that the discrete population segment represents the only 
surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historical range; or 
(4) evidence that the discrete population segment differs markedly from 
other populations of the species in its genetic characteristics. 
Significance of the discrete population segment is not necessarily 
determined by existence of one of these classes of information standing 
alone. Rather, information analyzed under these considerations is 
evaluated relative to the biological or ecological importance of the 
discrete population to the taxon as a whole. Accordingly, all relevant 
and available biological and ecological information is analyzed for 
importance to the taxon as a whole. Below, we provide our analysis of 
the significance of the lower Colorado River basin roundtail chub 
populations.
Persistence of the Population Segment in an Unusual or Unique 
Ecological Setting
    Based on our review of the best available information, we found 
that there are some differences in various ecoregion variables between 
the upper and lower Colorado River basins. For example, McNabb and 
Avers (1994) and Bailey (1995) delineated ecoregions and sections of 
the United States based on a combination of climate, vegetation, 
geology, and other factors. Populations of roundtail chub in the lower 
basin and in the upper basin occur primarily in different ecoregions. 
These ecoregions display differences in the natural hydrograph in the 
type, timing, and amount of precipitation between the two basins, with 
the upper basin (8-165 cm (3-65 in) per year) (Jeppson 1968, p. 1) 
somewhat less arid than the lower basin (13-64 cm (5-25 in) per year) 
(Green and Sellers 1964, pp. 8-11).
    The primary difference is that, in the lower basin there are two 
seasonal peaks of streamflow, a monsoon hydrograph plus the spring 
runoff season. In the upper basin, roundtail chub habitats have strong 
snowmelt hydrographs, with some summer, fall, and winter precipitation, 
but with the majority of major flow events in spring and early summer 
(Bailey 1995, p. 341; Carlson and Muth 1989, p. 222; Woodhouse et al. 
2003, p. 1551). The biology of the roundtail chub indicates the 
importance of the spring runoff as the cue for spawning, and this cue 
operates in both the upper and lower basins (Bezzerides and Bestgen 
2002, p. 21). The variability of the monsoon storms to provide for 
higher flows later in the summer is such that it does not have an 
influence on successful spawning. While there are differences in the 
ecological settings between the two segments, these differences are not 
likely to be significant to the taxon.
Significant Gap in the Range of the Taxon
    Roundtail chub in the lower Colorado River basin can be considered 
significant under our DPS Policy because loss of the lower Colorado 
River populations of roundtail chub would result in a significant gap 
in the range of the taxon. The lower and upper Colorado River basins 
are approximately 443 km (275 river mi) and possess a unique, divergent 
mtDNA lineage that has never been found outside the lower basin 
(Dowling and DeMarais 1993, pp. 444- 446; Gerber et al. 2001, p. 2028). 
The lower Colorado River area constitutes over one third of the 
species' historical range. There are 74 populations of roundtail chub 
remaining in the upper basin and 31 in the lower basin. Thus, the lower 
basin populations constitute approximately one third (30 percent) of 
the remaining populations of the species (Bezzerides and Bestgen 2002, 
pp. 28-29, Appendix C; Voeltz 2002, pp. 82-83). The populations in the 
lower basin account for approximately 49 percent (107,300 square mi, 
270,906 square km) of the Colorado River Basin (U.S. Geological Survey 
2006, pp. 94-102). In addition, the roundtail chub historically 
occupied up to 2,796 mi (4,500 km) of stream in the lower basin and 
currently occupies between 497 mi (800 km) and 901 mi (1450 km) of 
stream habitat in the lower basin. These populations are not newly 
established, ephemeral, or migratory. The species has been well 
established in the lower Colorado River basin, and has represented a 
large portion of the species' range for a long period of time 
(Bezzerides and Bestgen 2002, pp. 20-29; Voeltz 2002, pp. 82- 83). The 
loss of one third of a unique, divergent mtDNA lineage that has never 
been found outside the lower basin (Dowling and DeMarais 1993, pp. 444- 
446; Gerber et al. 2001, p. 2028) of the species as a whole would 
constitute a significant gap in the range.

[[Page 60759]]

Natural Occurrence of a Taxon Elsewhere as an Introduced Population
    As part of a determination of significance, our DPS Policy suggests 
that we consider whether there is evidence that the population 
represents the only surviving natural occurrence of a taxon that may be 
more abundant elsewhere as an introduced population outside its 
historical range (61 FR 4725). The roundtail chub in the lower Colorado 
River basin is not the only surviving natural occurrence of the 
species. Consequently, this factor is not applicable to our 
determination regarding significance.
Marked Differences in Genetic Characteristics
    As stated in the DPS Policy, in assessing the significance of a 
discrete population, the Service considers evidence that the discrete 
population segment differs markedly from other populations of the 
species in its genetic characteristics (61 FR 4725). There have been 
long-standing difficulties in morphological discrimination and 
taxonomic distinction among members from the lower Colorado Gila 
robusta complex, and the genus Gila as a whole, due in part to the role 
hybridization has played in its evolution. But it is important to 
consider variation throughout the entire Colorado River basin to place 
variation and divergence in the lower basin Gila robusta complex in 
appropriate context.
    Along with G. robusta, G. cypha and G. elegans are present in the 
mainstem Colorado River and many large tributaries throughout the 
basin. Lower Colorado River basin populations of these three species 
exhibited distinct mtDNAs, with only limited introgression of G. 
elegans into G. cypha (Gerber et al. 2001, p. 2028). G. robusta 
individuals from the headwaters of the Little Colorado River and the 
mainstem Colorado River and tributaries above Glen Canyon Dam in the 
upper basin possess G. cypha or G. elegans mtDNA (Dowling and DeMarais 
1993, pp. 444-446; Gerber et al. 2001, p. 2028). Populations of the G. 
robusta complex of the lower basin in the Bill Williams and Gila River 
basins (including G. robusta, G. intermedia, and G. nigra) possess a 
unique, divergent mtDNA lineage that has never been found outside the 
lower basin (Dowling and DeMarais 1993, pp. 444- 446; Gerber et al. 
2001, p. 2028). Conversely, in the upper Colorado River basin 
populations, the impact of hybridization was significant. Most upper 
basin fish sampled exhibited only G. cypha mtDNA haplotypes, with some 
individuals exhibiting mtDNA from G. elegans (Gerber et al. 2001, p. 
2028). The complete absence of G. robusta mtDNA, even in populations of 
morphologically pure G. robusta, indicates extensive introgression that 
predates human influence.
    Gerber et al. (2001, p. 2037) noted that genetic information in 
Gila poorly accounts for species morphology, stating that ``the 
decoupling of morphological and mtDNA variation in Colorado River Gila 
illustrates how hybridization and local adaptation can play important 
roles in evolution.'' The lower Colorado River discrete population 
segment differs markedly from the upper Colorado River basin segment 
due to the unique, divergent genetic lineage of the lower basin.
Summary of Significance
    The divergent genetic lineage within the lower Colorado River basin 
(Dowling and DeMarais 1993, pp. 444- 446; Gerber et al. 2001, p. 2028) 
demonstrates a marked difference in genetic characteristics from the 
upper Colorado River basin segment. In addition, the lower Colorado 
River basin segment constitutes one third of the species' range; the 
loss of which would result in a significant gap in the species' range. 
The lower Colorado River basin population of roundtail chub is 
therefore significant to the species as whole because the loss of this 
population would create a significant gap in the range and the 
population demonstrates a marked difference in genetic characteristics.

DPS Conclusion

    We have evaluated the lower Colorado River population segment of 
the roundtail chub to determine whether it meet the definition of a 
DPS, addressing discreteness and significance as required by our 
policy. On the basis of the best available information, we conclude 
that the lower Colorado River populations are discrete from the upper 
Colorado River basin populations on the basis of their present and 
historical geographic separation of 275 river mi (444 km) and because 
few historical records have been detected in the mainstem Colorado 
River between the two population centers that would suggest meaningful 
connectivity. We also conclude that the lower Colorado River basin 
roundtail chub is significant because of its unique genetic lineage, 
which differs markedly from the upper basin, and that the loss of the 
species from the lower basin would result in a significant gap in the 
range of the species. Because this population segment meets both the 
discreteness and significance elements of our DPS policy, the lower 
Colorado River population segment of the roundtail chub qualifies as a 
DPS in accordance with our DPS policy, and, as such, is a listable 
entity under the Act.

Summary of Biological Status and Threats

    The Act directs us to determine whether any species is an 
endangered species or a threatened species based on any on any of five 
factors: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence. We completed the Draft Headwater Chub and Lower 
Colorado River DPS of Roundtail Chub Species Status Assessment (SSA 
Report) (Service 2015; entire), which is available online at http://www.regulations.gov under Docket No. FWS-R2-ES-2015-0148. The SSA 
Report documents the results of the comprehensive biological status 
review for the headwater chub and lower Colorado River basin roundtail 
chub DPS, which provides a thorough account of the species' overall 
viability. We define viability here as a description of the ability of 
the species to sustain populations in the wild beyond a biologically 
meaningful timeframe. For these species, we assessed the future 
viability about 30 years from the present or around 2046. In the SSA 
Report, we assess the viability of the headwater chub and the lower 
Colorado River basin roundtail chub DPS in terms of resiliency, 
redundancy, and representation. Resiliency is having sufficiently large 
populations for the species to withstand stochastic events. Redundancy 
is having a sufficient number of populations for the species to 
withstand catastrophic events. Representation is having the breadth of 
genetic makeup of the species to adapt to changing environmental 
conditions.
    In the SSA Report, we summarize the relevant biological data and a 
description of past, present, and likely future risk factors (causes 
and effects) and provide an analysis of the viability of the species. 
Specifically, we evaluate the risk of extirpation of individual 
analysis units (AUs). The SSA Report provides the scientific basis that 
informs our regulatory decision regarding whether these species should 
be listed as endangered or threatened species under the Act. This 
decision involves the application of standards within the

[[Page 60760]]

Act, its implementing regulations, and Service policies (see 
Determination, below). The SSA Report contains the analysis on which 
this determination is based, and the following discussion is a summary 
of the results and conclusions from the SSA Report.

Historical and Current Range and Distribution

    The occurrence records of both species show some inconsistencies 
and in some cases use incorrect common names. Therefore, we used the 
best available information and made some decisions on assignment of 
chub species that may not be consistent with museum records, but we 
based these decisions on more current information and biological 
characters.
    Assignment of chubs in a stream to headwater, roundtail, or Gila is 
difficult due to the morphological and genetic similarities. Typically, 
assignment to species is based on the geographical location. Assignment 
to one or the other species has been made for all populations or 
streams of the headwater chub and roundtail chub DPS. However, there is 
some uncertainty within three streams (Fossil Creek and West Clear 
Creek in the Verde River drainage, and Turkey Creek in the Upper Gila 
drainage) where the species overlap, and likely hybridize with one 
another. Each of these locations is discussed in more detail below. For 
the purposes of the SSA Report and the SSA Model, we will evaluate 
Fossil Creek as having headwater chub from the constructed barrier 
upstream to Fossil Springs (above the barrier) and roundtail chub from 
the mouth of Fossil Creek to Irving (below the barrier), with a mix 
between Irving and the fish barrier. In West Clear Creek, for the SSA 
Report, we will consider lower and upper West Clear Creek are roundtail 
chub based on our past assignment. In Turkey Creek for the SSA Report, 
we will consider Turkey Creek contains only Gila chub, but not 
headwater chub.
    In the SSA Report, we use AUs to describe the populations of chubs. 
The AUs were delineated based on the hydrological connectivity of 
currently occupied streams and the ability of chubs to move within or 
among streams. There are two types of AUs considered in the SSA Report: 
(1) Those composed of one occupied stream, referred to as independent 
AUs; and (2) those composed of two or more hydrologically connected 
occupied streams, referred to as complex AUs.
Headwater Chub
    Based on our assessment, headwater chub historically occupied 26 
streams with a maximum total stream length of 892 kilometers (km) (554 
miles (mi)). The streams were distributed over three drainage basins: 
Gila River, Salt River, and Verde River. As of 2015, headwater chub are 
found in 22 streams with a collective minimum of 432 km (268 mi) of 
available habitat: 406 km (252 mi) from the historically occupied 
streams and 26 km (16 mi) from occupied streams newly discovered. We 
evaluated the reduction in range based on stream length rather than the 
number of streams because this provides a more accurate assessment of 
the amount of habitat. Listing the number of streams does not provide 
an account of the available habitat because streams could vary greatly 
in length. This represents at least 48 percent of the estimated 
historical range and no more than a 52 percent reduction in range. We 
document the extirpation of chubs from four historically occupied 
streams, totaling 71 km (44 mi). Additionally, we know that chub are 
not found in portions of Haiger and Tonto Creeks (approximately 25 km 
(16 mi) and 18 km (11 mi), respectively), where they were historically. 
This accounts for 114 km of the reduction in range, leaving 346 km (71 
mi) unaccounted for. This 346 km (71 mi) may represent actual habitat 
lost or may be due to differences in the methodologies used in 
calculating the historical and current ranges, or a combination of 
both.

    Table 1--Estimated Historical and Current Ranges (in Linear Stream km) of the Headwater Chub in the Lower Colorado River Basin for the SSA Report
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Estimated
                                                                           Estimated current  reduction in range
                                                           Estimated       range  (km & % of      (km & % of       Number of streams
                   Species of chub                     historical range        estimated           estimated         historically      Number of streams
                                                        based on stream    historical range    historical range        occupied       currently occupied
                                                        length (km) \1\        currently        that no longer
                                                                             occupied) \2\      contains chubs)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Headwater...........................................                892           432 (48%)           460 (52%)                  26                  22
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ This includes perennial, intermittent, and dry reaches within a stream.
\2\ This includes perennial and interrupted perennial reaches within a stream.

Lower Colorado River Basin Roundtail Chub DPS
    The lower Colorado River basin roundtail chub DPS historically 
occupied 48 streams with a maximum total stream length of 4,914 km 
(3,053 mi). The streams were distributed across five drainage basins: 
Bill Williams River, Gila River, Little Colorado River, Salt River, and 
Verde River. As of 2015, roundtail chub are found in 35 streams with a 
collective minimum of 2,098 km (1,303 mi) of available habitat: 2,077 
km (1,291 mi) from the historically occupied streams and 21 km (13 mi) 
from occupied streams newly discovered. We evaluated the reduction in 
range based on stream length rather than the number of streams because 
this provides a more accurate assessment of the amount of habitat. 
Listing the number of streams does not provide an account of the 
available habitat because streams could vary greatly in length. This 
represents at least 43 percent of the historical range and no more than 
a 57 percent reduction in range. We document the extirpation of chubs 
from six historically occupied streams, totaling 1,864 km (1,158 mi). 
Therefore, approximately 234 km (145 mi) of the potential reduction in 
range is unaccounted for. This 234 km (145 mi) may represent actual 
habitat lost or may be due to differences in the methodologies used in 
calculating the historical and current ranges, or a combination of 
both.
    There are also four newly established populations for the lower 
Colorado River basin roundtail chub DPS: Blue River in the Gila River 
drainage basin, Ash Creek in the Salt River drainage basin, and Gap 
Creek and Roundtree Creek in the Verde River drainage basin. Blue River 
is 81 km (50 mi) watered length, Ash Creek is about 5 km (3 mi) watered 
length, Gap Creek and Roundtree Canyon Creek are about 3 km (2 mi) in 
watered length each. The total

[[Page 60761]]

wetted length of all four streams is 92 km (57 mi).
    Historically, populations in the lower Colorado River basin 
roundtail chub DPS had greater connectivity to each other. However, 
roundtail chub are extirpated from several large riverine streams that 
provided connectivity across most of the historically occupied range. 
This has resulted in the recent isolation of AUs even within the same 
drainage basin.

    Table 2--Estimated Historical and Current Ranges (in Linear Stream km) of the Roundtail Chub in the Lower Colorado River Basin for the SSA Report
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Estimated
                                                                           Estimated current  reduction in range
                                                           Estimated       range (km & % of       (km & % of       Number of streams   Number of streams
                   Species of chub                     historical range        estimated           estimated         historically          currently
                                                        based on stream    historical range    historical range        occupied            occupied
                                                        length (km) \1\        currently        that no longer
                                                                             occupied) \2\      contains chubs)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Roundtail...........................................              4,914         2,098 (43%)         2,816 (57%)                  48                  35
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ This includes perennial, intermittent, and dry reaches within a stream.
\2\ This includes perennial and interrupted perennial reaches within a stream.

Individual, Population, and Species Needs for Headwater Chub and the 
Lower Colorado River Basin Roundtail Chub DPS

    Both adult headwater chub and the lower Colorado River basin 
roundtail chub DPS need slow-moving, deep pools, and juveniles and 
young-of-the-year need shallow water along stream banks. For shelter, 
they need large rocks, undercut banks, and woody debris. For spawning, 
they need pool, run, and riffle habitats with sandy-rocky substrates 
and slow to moderate water velocities. For feeding, adults need plants, 
detritus, and arthropods (aquatic and terrestrial), and juveniles and 
young-of-the-year need diatoms, filamentous algae, and insects. Adults 
may also consume small fish, as they are the top native fish predator 
in their habitat (Pilger et al. 2010, p. 306).
    Both headwater chub and the lower Colorado River basin roundtail 
chub DPS need to have multiple resilient populations distributed 
throughout different drainage basins within their historical range to 
maintain viability into the future and avoid extinction. Resilient chub 
populations must be of sufficient size to withstand stochastic events 
such as demographic effects of low genetic diversity and environmental 
variability. The best available data do not indicate a minimum or 
preferred population size. However, large (or more resilient) 
populations are better able to withstand disturbances such as random 
fluctuations in birth rates (demographic stochasticity), or variations 
in rainfall (environmental stochasticity). The resiliency of headwater 
chub or the lower Colorado River basin roundtail chub DPS populations 
is largely governed by: (1) The quantity, distribution, and 
connectivity of habitat; (2) the quality of habitat (specifically deep 
pools for adults and shallow waters along stream banks for juveniles 
and young-of-the-year); and (3) the presence or absence of nonnative 
aquatic species. These conditions combine to control the size of the 
chub population and its age structure (which increases the resiliency 
of AUs in terms of demographic stochasticity and genetic diversity). 
Further, these conditions control the extent of habitat available to 
serve as refuge sites for chub to survive environmental stochasticity 
and localized threats from land and water uses, and allow re-occupancy 
of the affected habitat area after the event.
    For redundancy, both the species and DPS need a sufficient number 
of resilient populations to withstand catastrophic events. The wider 
the distribution of resilient populations and the greater the number of 
populations, the more redundancy the species or DPS will have. This 
redundancy reduces the risk that a large portion of the range will be 
negatively affected by any catastrophic event at any one time. Species 
that are well distributed across their historical range (i.e., having 
high redundancy) are less susceptible to extinction and more likely to 
be viable than species confined to a small portion of their range 
(Carroll et al. 2012, entire; Redford et al. 2011, entire).
    Having a breadth of genetic makeup of the species to adapt to 
changing environmental conditions is needed for representation. 
Representation can be measured through the genetic diversity within and 
among populations, and the ecological diversity (variety of ways 
species interact with each other and the environment) of populations 
across the species' range. The more representation, or diversity, the 
species has, the more it may be capable of adapting to changes (natural 
or human caused) in its environment. In the case of the headwater chub 
and lower Colorado River basin roundtail chub DPS, maintenance of the 
identified genetic diversity in AUs across the species' and DPS's 
geographic range is important.

Risk Factors for Headwater Chub and the Lower Colorado River Basin 
Roundtail Chub DPS

    We reviewed the potential factors that may affect the headwater 
chub and lower Colorado River basin roundtail chub. We found three 
primary risk categories: (1) Competition with, predation from, and 
harassment by nonnative aquatic species; (2) a lack of sufficient water 
to support the physical and biological components needed for all life 
stages and life-history functions; and (3) changes in the timing and 
amount of snowmelt runoff in the spring and precipitation from monsoons 
in the fall, reduction in hydrologic connectivity within and between 
streams, and the reduction in the length of flowing reaches (all of 
which are impacts from climate change). All three of these risks 
categories likely have population-level effects to both the headwater 
chub and the lower Colorado River basin roundtail chub DPS.
    We considered several other potential risk factors that may have 
population-level effects to either the headwater chub or the lower 
Colorado River basin roundtail chub DPS, but we were not able to 
incorporate into the model. These include wildfire risk, additional 
climate change impacts (other than those considered in the model), 
water loss due to anthropogenic actions, and demographic impacts from 
these factors and the reduction in the range. We evaluated impacts from 
these additional risks to each AU and the species/DPS as a whole.
    There are other risks to both chub species that can result in 
localized effects, including grazing, roads, forestry practices, 
disease, pathogens, and recreation. While these may have effects

[[Page 60762]]

on individual chubs, they are not likely to have population-level 
impacts on either the headwater chub or the lower Colorado River basin 
roundtail chub DPS, as explained in chapter 7 and appendix B of the SSA 
Report.
    Across the historical range, the quality and quantity of habitat, 
abundance of headwater chub and roundtail chub, and condition of the 
AUs has been altered. The introduction of nonnative aquatic species and 
changes in water flows, caused by human activities (either surface 
water diversion or groundwater pumping) and climate change, leading to 
a reduction in water availability, have led to reductions in chub 
abundance and habitat quality and quantity. Nonnative aquatic species 
occur within almost all streams occupied by these two chub species. The 
changes in flows have altered the connectivity and spatial distribution 
of chubs, resulting in segmentation of watered areas within individual 
streams and loss of connectivity between streams.
    Nonnative fish are the most significant risk factor to the lower 
Colorado River fish fauna, including headwater chub and the lower 
Colorado River roundtail chub DPS, due to competition and predation 
(Minckley and Deacon 1991; Carlson and Muth 1989, p. 220; Mueller 2005, 
pp. 10-12; Olden and Poff 2005, p. 75). It has now been shown that 
contamination by nonnative fishes is the most significant risk factor 
to the lower Colorado River fish fauna due to competition and predation 
(Minckley and Deacon 1991; Carlson and Muth 1989, p. 220; Mueller 2005, 
pp. 10-12; Olden and Poff 2005, p. 75), and nonnative aquatic species 
are the primary impediment to the native fish species' success 
(Minckley and Marsh 2009, p. 51). Declines in native fish, including 
roundtail and headwater chubs, are largely attributable to predation, 
with early life stages (Minckley 1983, p. 182) being the most 
vulnerable. Clarkson et al. (2005, p. 20) noted that over 50 nonnative 
aquatic species were introduced into the Southwest as either sport fish 
or baitfish. Lower West Clear Creek showed a reduction in roundtail 
chub after smallmouth bass became a significant part of the fish 
community (Brouder et al. 2000, pp. 9, 13; Jones et al. 2014, pp. 70-
71), and in the upper Salt River after flathead catfish were introduced 
(AGFD 1996), and these reductions have been interpreted as resulting 
from those nonnative fish expansions. Fathead minnow (Pimephales 
promelas), green sunfish (Lepomis cyanellus), red shiner (Cyprinella 
lutrensis), western mosquitofish (Gambusia affinis), largemouth bass 
(Micropterus salmoides), flathead catfish (Pylodictis olivaris) (Fuller 
1999, p. 208), and channel catfish (Ictalurus punctatus) are among the 
fastest expanding nonnative fishes in the basin and are considered to 
be the most invasive in terms of their negative impacts on native fish 
communities (Olden and Poff 2005, pp. 83-84). Of these species, green 
sunfish, flathead catfish, smallmouth bass, and largemouth bass are 
considered to impact chubs the most.
    However, there are streams where chubs have maintained populations 
in the presence of one or more of these nonnative aquatic species, but 
the mechanisms providing for that coexistence in any particular stream 
are unknown. The nonnative aquatic species community varies for 
different streams. The amount of preferred habitat available for both 
the chub and the nonnative aquatic species may play a role, as may the 
abundance of the nonnative species and its means of affecting the chub. 
In some cases, the nonnative aquatic species may have only newly 
entered the stream and the full effects have not been realized. In 
other cases, the current habitat and population dynamics may not 
strongly favor either natives or nonnatives, allowing for persistence 
of both under those conditions. While chubs coexist with nonnative 
aquatic species in several streams, this does not mean that nonnative 
aquatic species are not impacting chubs or that nonnative aquatic 
species are not having population-level impacts on chubs. Marks et al. 
(2009, pp. 15, 21) looked at the response of native fish in Fossil 
Creek before and after nonnative fish were removed from the stream. 
With the removal of these nonnative fish, headwater and roundtail chub 
numbers increased 70 times over the pre-removal numbers due to the 
success of spawning and survival of young-of-the-year chubs.
    Nonnative aquatic species occur within all streams occupied by 
chubs with the exception of three streams for each species. We expect 
that nonnative aquatic species will continue to persist in most, if not 
all, of the streams they currently occupy because they have readily 
adapted to the stream conditions and removing them from areas they 
currently occupy is difficult and expensive. Further, it is likely that 
the increase in the frequency and severity of droughts, the reduction 
of flowing regions within a network of streams, and an increase in the 
length of dry patches within a stream as a result of climate change 
will exacerbate the impacts from nonnative aquatic species. This is 
because as the available watered segments decrease, the interactions 
between nonnatives and chubs increase, with more larvae and young-of-
the-year removed from the chub populations due to predation by 
nonnative aquatic species. In addition, resources become more limited 
and the competition for these resources increases, resulting in 
decreased food for chubs and more competition for that food. The 
reduction in water will likely decrease the water quality (e.g., 
decreased dissolved oxygen, temperature increases, changes in pH, and 
nutrient loading) (Lake 2000, p.578; Lake 2003, p. 1165), which 
nonnative aquatic species are likely more capable of adapting to than 
the chubs. (Eaton and Scheller 1996, p. 1111; Rahel and Olden 2008, p. 
527; Rahel et al. 2008, pp. 554-555). While the chubs have maintained a 
presence in several streams with nonnatives, the impacts from nonnative 
aquatic species exacerbated by other factors reduce the streams' 
ability to withstand stochastic events. In addition, there is the 
potential that the six streams (three for headwater chub and three for 
lower Colorado River basin roundtail chub DPS) that currently do not 
have nonnative aquatic species could be infiltrated by nonnatives. The 
three headwater chub streams are Diamond Creek in the Gila River basin, 
and Buzzard Roost Creek and Turkey Creek in the Tonto Creek basin. For 
the lower Colorado River basin roundtail chub DPS, the streams are 
Stone Corral Canyon Creek and Conger Creek in the Bill Williams basin, 
and Canyon Creek in the Salt River basin.
    Nonnative aquatic species could be introduced through the release 
of baitfish, intentional introduction by anglers for sport fishing, or 
flooding events, which allow chubs to pass low water barriers. The 
management of nonnatives is an important tool in the conservation of 
these species. Currently, due to a lack of a producer for Antimycin A 
and lack of Environmental Protection Agency (EPA) registration for 
other potential piscicides in development, the most effective method to 
remove fish is rotenone. However, the process for public coordination 
and other steps required on the pesticide label make it difficult and 
time-consuming to use rotenone under Federal law, and even more so 
under Arizona State Law (ARS Title 17-481) and Arizona Game and Fish 
Commission policy. Given vocal public and political opposition to 
rotenone treatments, stream restoration has become difficult in Arizona 
because of the lengthy bureaucratic process attached to those 
treatments. Without

[[Page 60763]]

this tool, management of nonnative aquatic species will become more 
difficult (Pool et al. 2013, p. 640).
    Water is the basic habitat component needed for both chub species' 
survival and to support the various life stages and life-history 
functions. Water supports the needed physical and biological 
characteristics in streams to provide suitable chub habitat. There is a 
strong seasonal component to the amount of water available in a stream. 
There is snowmelt in the spring, which is important for spawning, and 
monsoon rains in the summer that is important during the driest time of 
year (late spring, early summer). Spatial and temporal variation in 
water amount and temperature may influence timing and periodicity of 
spawning, influence elevation distributions within stream systems, and 
impact the life cycles and availability of food resources (Dallas 2008, 
pp. 395-397). Historically, the amount of water in any stream at any 
time was determined by natural water sources, such as surface flow, 
springs, and alluvial groundwater input. Currently, these natural water 
sources are impacted by climate change (discussed below) and human 
actions. The creation of large water storage dams (such as those on the 
Salt and Verde Rivers) eliminate flowing sections of water and replace 
them with large reservoirs that support nonnative fish species. Chubs 
may be found in these large reservoirs initially, but do not persist 
there (Bezzerides and Bestgen 2002, p. 18). The dams that form the 
reservoirs are impassible obstacles and prevent chubs from moving 
through the system, resulting in occupied fragments of a stream where 
there was once full connectivity.
    On the smaller scale, diversion dams that allow for removal of 
water from the stream for human uses may or may not be barriers to 
connectivity depending on their size and structure; however, their 
effect on flows can be substantial depending on the number of 
diversions in a stream, and the season of diversion. For agriculture, 
the primary diversion season is in the late spring through early fall. 
Generally, late spring and early summer is the time of year with the 
lowest flow and when water supplies are already stressed. This 
contributes to local stream drying, where the reach below the diversion 
can be all or partially dry until any return flows from the land use 
from agricultural fields, groundwater levels restore surface flow, or 
monsoon rains. In addition to direct removal of surface flow, wells 
that tap the alluvial groundwater (the shallow aquifer that also 
supports the surface flow in a stream) can reduce the level of the 
groundwater such that it is below the streambed elevation and cannot 
provide surface flows. In areas with few wells, this is generally not a 
significant concern; however, in areas with denser human development 
(as is found along the East Verde River, Oak Creek, and Wet Beaver 
Creek), stream drying occurs occurs (Girmendonk and Young 1997, pp. 31-
32, 42; Paradzick et al 2006, pp.9-12). Demand for water is projected 
to increase as human populations are predicted to increase, affecting 
the timing, amount, and distribution of water within streams.
    Climate change models project alteration in the timing and amount 
of snowmelt and monsoon rains, and the frequency and duration of 
droughts, as well as increases in temperature resulting in increased 
evaporation. During the spring and early monsoon seasons, the flowing 
regions of the Verde River stream network (areas with water) are 
projected to diminish a median of 8 percent and a maximum of 20 percent 
(Jaeger et al. 2014, p. 3) from their current status in the Verde River 
basin. Over much of the western United States and western Canada, 
warmer winters are projected to produce earlier runoff and discharge 
but less snow water equivalent and shortened snowmelt seasons in many 
snow-dominated areas (Barnett et al. 2005, entire; Rood et al. 2008, 
entire; Reba et al. 2011, entire).
    Climate change model predictions suggest that climate change will 
shrink the length of the remaining flowing reaches in the Verde River, 
in the lower Colorado River basin, where both these species occur 
(Jaeger et al. 2014, p. 3). The frequency of stream drying events in 
the Verde Valley is expected to increase by approximately 17 percent 
(Jaeger et al. 2014, p. 13895), due in large part to groundwater 
decline. These regions that support flow are increasingly isolated as 
adjacent dry fragments expand in length and occur more frequently 
across these seasons. Model predictions suggest that midcentury and 
late-century climate will reduce network-wide hydrological 
connectivity. Midcentury and late-century climate model projections 
suggest that more frequent and severe droughts will reduce network-wide 
hydrologic connectivity for native fishes by 6 to 9 percent over the 
course of a year and up to 12 to 18 percent during spring spawning 
months (Jaeger et al. 2014, p. 3). The reduction in the length of the 
remaining flowing reaches will further increase native and nonnative 
aquatic species interactions and resource limitations, and will 
compromise the ability of these habitats to support native fishes 
(Jaeger et al. 2014, p. 3), including these chub species.
    The best available data indicate that climate change and increased 
human population levels in the Verde Valley in the lower Colorado River 
basin will result in lowered groundwater levels and stream base flows 
to some degree (Garner et al. 2013, p. 23; Jaeger et al. 2014, p. 
13895). The decline in groundwater levels and base flows in the region 
is expected to be caused by increased groundwater pumping, by surface 
water diversion, and from an increase in the frequency and severity of 
droughts in Arizona as a result of climate change. Specifically, future 
water levels and stream base flows are expected to continue decreasing 
along the Verde River and Oak Creek in response to increased pumping, 
particularly over the next 50 years (Owens-Joyce and Bell 1983, pp. 1, 
65; McGavock 1996, p. 67; Blasch et al. 2006, p. 2; Garner et al. 
2013). The best available information regarding future water 
availability for chubs includes models of the groundwater and base flow 
in the Verde River through approximately 2050. These models indicate a 
maximum of 20 percent loss of flow for the Verde River by approximately 
2050 during dry times of the year (Jaeger et al. 2014, p. 13897). 
Despite native fishes having evolved life-history strategies to cope 
with the harsh environmental conditions that occur as a result of 
stream drying events, the predicted spatiotemporal changes in 
streamflow likely will have adverse consequences for the distribution, 
abundance, and persistence of these species into the future.
    Effects to chubs from wildfire vary depending on the wildfire and 
streams. The severity, location, and timing of the wildfire influence 
the impact of wildfire to chubs depending on the amount of runoff, and 
degree of sediment and ash in the runoff. The size and condition of the 
stream also influences the impact to chubs from wildfire. There are 
streams where chubs (and other fish species) survived the post-fire 
ash/sediment flows following wildfire. This happened in the Upper Gila, 
Black River, and Spring Creek (Tonto River drainage). It is probable 
that there were individual fish that died or were harmed, and 
population numbers (or health) were reduced. However, populations that 
were initially depressed in these streams have rebounded, even 
increasing in abundance or extent relative to pre-fire conditions. 
However, in certain streams, like Cave Creek, Gila chub populations 
were impacted by the

[[Page 60764]]

Cave Creek Complex Fire through changes in habitat abundance, in which 
pools where filled with sediment. However, Gila chub still persist in 
all the locations that were occupied by chub prior to the Cave Creek 
Complex Fire. Forest management at large landscape scales across the 
ranges of the chubs is occurring and will continue to occur to reduce 
forest fuels and therefore reduce wildfire risk and severity. However, 
the effects from climate change, such as increased temperatures, 
increased evaporation, and change in timing and amount of 
precipitation, are likely to create conditions more favorable to 
wildfire. Wildfire can result in impacts to individuals and could also 
result in population-level impacts. Wildfire could impact any stream or 
any AU within the range of both species. Severe or extensive wildfires 
that occur in smaller AUs and independent AUs are more likely to have 
an impact on these species as a whole. However, we are unable to 
predict when or where such fires could occur, nor the impacts to chubs 
from these wildfires, but we recognize that wildfires are highly likely 
to occur. We further recognize that not all fire is harmful to these 
species.
    As a result of the risk factors described above, particularly from 
climate change, the connectivity of chubs within and between streams is 
impacted, resulting in fragmented streams and AUs that could have 
population-level impacts to chubs. This results in small and isolated 
populations, susceptible to demographic impacts. Demographic impacts 
include loss of genetic diversity from inbreeding depression and 
genetic drift resulting in young that may have reduced fitness to cope 
with existing or changing conditions. This decreases a population's 
ability to adapt to environmental changes and increases vulnerability 
to extirpation (i.e., decreases resiliency). Fagan et al. (2002, p. 
3254) found that, as a result of fragmentation and isolation, roundtail 
chub has a moderately high risk of local extirpation (0.41 percent 
probability) because recolonization from adjacent populations is less 
likely. Headwater chub, which has naturally fragmented populations, has 
a lower risk of local extirpation (0.28 percent probability), as it 
still occupies many of its historical localities, which are headwater 
and smaller tributary habitats. However, fragmentation within those 
populations exercises the same potential for adverse effects of small, 
isolated populations. In examining the relationship between species 
distribution and extinction risk in southwestern fishes, Fagan et al. 
(2002, p. 3250) found that the number of occurrences or populations of 
a species is less significant a factor in determining extinction risk 
than is habitat fragmentation.
    These species developed as a result of multiple independent 
hybridization events over time (Rinne 1976; Rosenfeld and Wilkinson 
1989; DeMarais et al. 1992; Dowling and DeMarais 1993; Minckley and 
DeMarais 2000; Gerber et al. 2001; Schwemm 2006; Sch[ouml]nhuth et al. 
2014). Historically roundtail chub had greater connectivity among 
populations and subsequent relatedness over the region. The development 
of populations in isolation from other roundtail chub was not the 
normal condition across most of the historical range except in the Bill 
Williams River and Little Colorado River drainages. In the lower 
Colorado River basin roundtail chub DPS, genetic variation occurs 
mainly within populations. For roundtail chub, demographic effects 
could result not only if AUs are fragmented but also if connectivity 
among AUs is fragmented.
    In headwater chub, most of their genetic variation occurs among 
populations, each of which tends to be distinctive. Each AU is 
geographically isolated from the other AUs even in the same drainage 
basin. For headwater chub, demographic effects could result if AUs 
become fragmented due the unique genetic variation within each AU. As 
the demand for water by humans and the effects of climate change 
increase, water is likely to become more limited. This loss of water 
affects the water flow in a stream and the number and length of watered 
and dry stream segments (i.e., increased fragmentation of a stream). As 
fragmentation increases so does the risk of demographic impacts. Small 
and isolated populations are vulnerable to loss of genetic diversity, 
which decreases a population's ability to adapt to environmental 
changes and increases vulnerability to extirpation.

Conservation Efforts for Headwater Chub and the Lower Colorado River 
Basin Roundtail Chub DPS

    Past conservation efforts include the establishment of new 
populations for roundtail chub in the lower Colorado River Basin DPS 
and the renovation or securing of currently occupied areas for 
headwater and roundtail chub in the lower Colorado River Basin DPS. 
Newly established populations are sites where chubs have been released 
within the species' historical range. This involves locating a site 
with suitable habitat, free of nonnative aquatic species or with 
nonnatives to be removed, through chemical or mechanical means. 
Establishment of a hatchery broodstock for the streams at risk of loss 
of wild populations provides for newly established populations to those 
areas. Renovation or securing of a population involves salvaging the 
chub species from the stream, then the removal of nonnative aquatic 
species and potentially the installation of a barrier to keep 
nonnatives out of the site, and then the release of salvaged chubs back 
into the stream. Stream renovation is labor- and time-intensive. The 
salvage of chubs takes significant resources in terms of time, 
personnel, and funding. Temporary housing for the salvaged chub is 
needed while the nonnative aquatic species are removed. The eradication 
of nonnative aquatic species from streams is essential for establishing 
new populations or securing populations. However, removing nonnative 
aquatic species from a stream is difficult and typically requires 
multiple efforts. Rotenone is the most effective means of eradicating 
nonnatives from a stream. If there is not a barrier to prevent 
nonnative aquatic species from moving into the renovated area, then a 
barrier will need to be constructed prior to removing the nonnatives. 
Once the nonnative aquatic species are removed and a barrier put in 
place, chubs are released back into the stream. It is likely that not 
all nonnative aquatic species were removed, and a rotenone treatment 
will be necessary at some point in the future. This will require 
salvaging the chubs again and applying the rotenone, and then releasing 
the salvage chubs.
    Removal of nonnative aquatic species has been used as a securing 
action for Fossil Creek for both headwater and roundtail chub. This 
effort has been successful, but significant time and resources were 
expended to secure the site and continue to be needed to maintain this 
site. Consequently, due to the expense and time, there is uncertainty 
regarding the securing of sites in the future.
    There are currently four newly established sites for the roundtail 
chub in the lower Colorado River basin. The four new established 
populations are: Blue River, Ash Creek, Gap Creek, and Roundtree Creek. 
Blue River is the only established site with documented reproduction. 
This site has a high potential for success; however, it is a relatively 
new site established in 2012. The other three sites have not shown 
reproduction. Their long-term viability is uncertain.
    Three of the established sites are free of nonnative aquatic 
species. Blue

[[Page 60765]]

Creek, the fourth newly established site, does contain some nonnatives 
but the community level of impacts is not likely to impact at a 
population level but does have negative effects to individuals. The 
success of secured sites is dependent on keeping the site free of or 
with limited nonnative aquatic species. The eradication of nonnative 
aquatic species from streams is essential for establishing new 
populations or securing populations. Rotenone is a primary means of 
eradicating nonnative fish from a stream. Currently, due to a lack of a 
producer for Antimycin A and lack of EPA registration for other 
potential piscicides in development, the most effective method to 
remove fish is rotenone. However, the process for public coordination 
and other steps required on the pesticide label make it difficult and 
time-consuming to use rotenone under Federal law. Given the difficulty 
and uncertainty surrounding the use of this tool, management of 
nonnative aquatic species could be problematic in the future. Without 
this tool, management of nonnative fish will become more difficult and 
the success of future conservation efforts more uncertain. Due to the 
high uncertainty of the success of newly established populations, and 
the likelihood that rotenone will not be a useable tool to remove 
nonnative aquatic species, we did not rely on newly established 
populations or renovated streams in our assessment of future 
conditions.
    In addition, the U.S. Forest Service has implemented a suite of 
practices to reduce the risk of high-severity fires in the range of the 
chubs, such as prescribed burning, mechanical thinning, and retention 
of large trees. These actions can help southwestern forest ecosystems 
adapt to climate change and reduce the risk of extreme fire behavior 
(Finney et al. 2005). These measures can also reduce emissions of the 
gases that cause climate change because long-term storage of carbon in 
large trees can outweigh short-term emissions from prescribed burning. 
Although considerable work has been accomplished to reduce fuel loads 
and plans to continue that effort are documented, wildfire still poses 
a risk to the chubs.

Current Condition

    In the SSA Report, we used AUs to describe the populations of 
chubs. The AUs were delineated based on the hydrological connectivity 
of currently occupied streams and the ability of chubs to move within 
or among streams. There are two types of AUs considered in the SSA 
Report: (1) Those composed of one occupied stream, referred to as 
independent AUs; and (2) those composed of two or more hydrologically 
connected occupied streams, referred to as complex AUs.
    We determined that water availability, nonnative aquatic species, 
and chub population structure are the three primary risks to these 
species. We modeled certain components contributing to the primary 
risks that were most likely to have a population-level impact to both 
species of chub. We developed a qualitative (measuring by quality of 
physical and biological components rather than quantitatively) model to 
summarize our understanding of the risk of extinction of these species 
due to these factors. To model water availability, we considered stream 
length as a surrogate for available habitat. We recognize that stream 
length does not equate to the quality of habitat available, but this is 
the best available data we have. The effect of nonnative aquatic 
species was evaluated in terms of the impacts from the community of 
nonnatives aquatic species present in a stream and the known impacts to 
chubs from the nonnative aquatic species present in the stream. Chub 
population structure is expressed in terms of chub abundance, number of 
age classes, and number of positive surveys for presence of the 
species. In addition, the model captures past conservation measures, 
such as stream renovations and newly established populations. Although 
not incorporated into our model, we also considered additional risk 
from climate change and water loss due to anthropogenic factors (e.g., 
surface water diversion and groundwater pumping), which is part of the 
water availability factor we included in our model. However, we were 
not able to capture additional risk from climate change and water loss 
due to anthropogenic factors in the model. In addition, we assessed 
impacts from wildfire based on the wildfire risk map developed by the 
U.S. Forest Service, recognizing that not all fire results in adverse 
effects to these chubs. Further, we considered the demographic impacts 
from these risks and the reduction in range. We evaluated impacts from 
these additional risks to each AU and the species as a whole. We 
considered these additional factors by evaluating their impacts to AUs 
and the species as a whole. For additional information on our 
assessment model, refer to the SSA Report at http://www.regulations.gov.
    The current condition is expressed as our understanding of risk of 
extirpation now or in the near future (next 5 years). We identified 
four categories to communicate how we are defining risk of extirpation, 
described in Table 3, below. An AU categorized as minor risk has a 0 to 
5 percent change of extirpation.

   Table 3--Modeled Analysis Unit Ranking Categories Based on Risk of
                               Extirpation
------------------------------------------------------------------------
                                                            Extirpation
                        Category                             risk (%)
------------------------------------------------------------------------
Minor Risk Extirpation..................................             0-5
Low Risk Extirpation....................................            6-30
Moderate Risk Extirpation...............................           31-60
High Risk Extirpation...................................             >60
------------------------------------------------------------------------

    The results of our model analysis are displayed in Tables 4, 5, and 
6, below. The San Carlos River AU and the upper Salt River AU are 
within tribal boundaries. The available data for these areas are dated 
and limited. In our analysis, we consider these AUs occupied; however, 
we have high uncertainty in this status.
Headwater Chub
    Currently, there are eight AUs over three drainage basins: Gila 
River, Salt River, and Verde River. Headwater chub are found in 22 
streams with a collective minimum of 432 km (268 mi) of available 
habitat. This represents at least 48 percent of the estimated 
historical range and no more than a 52 percent reduction in range. 
Stream lengths range from 3 to 70 km (2 to 44 mi). Average stream 
length is 17 km (10 mi). Only three streams lack nonnative aquatic 
species impacting chubs. Only one AU is in the minor risk of 
extirpation category. There are three AUs in the low risk, and four in 
the moderate risk categories (see Table 4, below).

[[Page 60766]]



                     Table 4--Modeled Current Condition of Headwater Chub by Analysis Units
                                       [C = Complex AU; I = Independent AU]
----------------------------------------------------------------------------------------------------------------
                                                                            Type/Number of          Risk of
           Watershed                Sub-watershed       Analysis unit          streams            extirpation
----------------------------------------------------------------------------------------------------------------
Gila River.....................  Lower Gila River..  San Carlos........  C/2................  Moderate.
                                 Upper Gila River..  Three Forks.......  C/4................  Low.
Salt River.....................  Tonto Creek.......  Lower Tonto Creek.  C/2................  Moderate.
                                 Tonto Creek.......  Upper Gunn Creek..  I..................  Moderate.
                                 Tonto Creek.......  Upper Tonto Creek.  C/8................  Low.
Verde River....................  East Fork Verde     East Fork Verde     C/5................  Moderate.
                                  River.              River.
                                 Verde River.......  Upper Fossil Creek  I..................  Minor.
                                 Verde River.......  Upper Wet Bottom    I..................  Low.
                                                      Creek.
----------------------------------------------------------------------------------------------------------------

    Once the modeled results of the current condition were determined, 
we then evaluated the risk from wildfire, additional risk from climate 
change, water loss due to anthropogenic actions, and the demographic 
impacts from these risk factors and reduction in range on the AUs and 
the species as a whole. We assessed if an AU in each risk category were 
to experience a wildfire, loss of connectivity, decreased water flow 
due to anthropogenic actions and climate change, and demographic 
impacts, how that would further affect the condition of the AU. We 
recognize that impacts from fire do not always result in adverse 
impacts to chubs. We then considered how this would impact the 
redundancy and representation of the species.
    Wildfire could impact one or more AUs now or in the near future (5 
years). Impacts could range from loss of individuals to loss or 
significant impacts to entire AUs or multiple AUs. The likelihood of 
wildfire now or in the near future is high; however, the severity, 
timing, and location of the wildfire is uncertain.
    Climate change is projected to reduce the flowing stream length of 
river networks. However, there are other impacts from climate change 
that we considered but were not able to incorporate into the model. 
This includes the increased lengths of dry reaches within a stream, 
loss of connectivity within and among streams, changes in the timing 
and amount of snowmelt and monsoon rains, changes in the frequency and 
duration of droughts, and the increase in temperatures resulting in 
increased evaporation. Increased dry reaches can impact chub movement 
and dispersal. Connectivity within streams is important for headwater 
chubs to maintain genetic diversity. Alterations in the timing and 
amount of water in the spring could result in delayed or reduced 
reproduction and recruitment. Alterations in the timing and amount of 
monsoon rains could result in a decrease in refugia areas for chubs 
after the driest time of the year. Impacts from climate change occur 
throughout the range of the headwater chub and are likely to affect all 
streams to some degree. In addition to the reduction in water from 
climate change, we also evaluated impacts to chubs from the loss from 
surface water diversions and groundwater pumping. These impacts are 
likely to impact all AUs to some degree.
Lower Colorado River Basin Roundtail Chub DPS
    Currently, there are 15 AUs across five drainage basins: Bill 
Williams River, Gila River, Little Colorado River, Salt River, and 
Verde River. Roundtail chub are found in 35 streams with a collective 
minimum of 2,098 km (1,303 mi) of available habitat. This represents at 
least 43 percent of the historical range and no more than a 57 percent 
reduction in range. The stream lengths range from 7 to 320 km (4 to 199 
mi), with an average stream length of 50 km (10 mi). Only three streams 
lack nonnative aquatic species impacting chubs. One stream, Fossil 
Creek, has undergone renovation (meaning nonnatives have been removed). 
There are currently four newly established sites (see Table 6, below). 
There is only one AU in the minor risk of extirpation category. There 
are seven AUs in low risk, six in moderate risk, and one in high risk 
(see Table 5, below).

          Table 5--Modeled Current Condition of Lower Colorado River Basin Roundtail DPS Analysis Units
                                      [C = Complex AU; I = Independent AU]
----------------------------------------------------------------------------------------------------------------
                                                                            Type/Number of          Risk of
           Watershed                Sub-watershed       Analysis unit          streams            extirpation
----------------------------------------------------------------------------------------------------------------
Bill Williams River............  Boulder Creek.....  Upper Boulder       C/3................  Low.
                                                      Creek.
                                 Burro Creek.......  Burro Creek.......  C/4................  Low.
                                 Santa Maria River.  Santa Maria River.  C/4................  Moderate.
                                 Trout Creek.......  Trout Creek.......  C/3................  Low.
Gila River.....................  Lower Gila River..  Aravaipa Creek....  I..................  Low.
                                                     Eagle Creek.......  I..................  Low.
                                 Upper Gila River..  Upper Gila River..  I..................  Moderate.
Little Colorado River..........  Chevelon Creek....  Chevelon Creek....  I..................  Low.
                                 Clear Creek.......  Clear Creek.......  C/2................  Moderate.
Salt River.....................  Upper Salt River..  Salome Creek......  I..................  High.
                                                     Upper Salt River..  C/9................  Moderate.
Verde River....................  Lower Verde.......  Confluence........  C/2................  Moderate.
                                 Fossil Creek......  Upper Fossil Creek  I..................  Low.
                                 Verde River.......  Upper West Clear    I..................  Minor.
                                                      Creek.
                                 Verde River.......  Verde River.......  C/6................  Moderate.
----------------------------------------------------------------------------------------------------------------


[[Page 60767]]

    Once the modeled results of the current condition were determined, 
we then evaluated the risk from wildfire, additional risk from climate 
change, water loss due to anthropogenic actions, and demographic 
impacts from these risks factors and reduction in range on the AUs and 
the species as a whole. We assessed if an AU in each risk category were 
to experience a wildfire, loss of connectivity, decreased water flow, 
or demographic impacts, how that would further affect the condition (or 
resiliency) of the AU. We recognize that impacts from fire do not 
always result in adverse impacts to chubs. We then considered how this 
would impact the redundancy and representation of the species.
    Wildfire could impact one or more AUs now or in the near future (5 
years). Impacts could range from loss of individuals to loss or 
significant impacts to entire AUs or multiple AUs. The likelihood of 
wildfire now or in the near future is high; however, the severity, 
timing, and location of the wildfire is uncertain.
    Climate change is projected to reduce the flowing stream length. 
However, there are other impacts from climate change that we considered 
but were not able to incorporate into the model. This includes the 
increased lengths of dry reaches within a stream, loss of connectivity 
within and among streams, changes in the timing and amount of snowmelt 
and monsoon rains, changes in the frequency and duration of droughts, 
and the increase in temperatures resulting in increased evaporation. 
Increased dry reaches can impact chub movement and dispersal. 
Connectivity within and among streams is important for the lower 
Colorado River basin roundtail chub DPS to maintain genetic diversity. 
Alterations in the timing and amount of water in the spring could 
result in delayed or reduced reproduction and recruitment. Alterations 
in the timing and amount of monsoon rains could result in a decrease in 
refugia areas for chubs after the driest time of the year. Impacts from 
climate change occur throughout the range of the lower Colorado River 
basin roundtail chub DPS and are likely to affect all streams to some 
degree. In addition to the reduction in water from climate change, we 
also evaluated the impacts to chubs from the loss from surface water 
diversions and groundwater pumping. These impacts are likely to impact 
all AUs to some degree.
Lower Colorado River Basin Roundtail Chub DPS's Newly Established Sites
    There are currently four newly established sites for the lower 
Colorado River basin roundtail chub DPS (see Table 6, below), each site 
is an individual AU. These are relatively newly established AUs, and 
their success is unclear at this time. The Blue River site is the only 
site that has demonstrated reproduction. The remaining three sites have 
yet to show any reproduction. We analyzed the current condition of 
these AUs using the same method that we used to analyze the headwater 
chub and extant populations of lower Colorado River basin roundtail 
chub DPS, meaning that we analyzed these using the model and then 
considered wildfire impacts, additional climate change impacts, water 
loss due to anthropogenic actions, and the demographic effects from 
these factors. Again, we recognize that impacts from fire do not always 
result in adverse impacts to chubs. However, we present the results 
separately due to the uncertainty of their success.

Table 6--Modeled Current Condition of Lower Colorado River Basin Roundtail Chub DPS's Newly Established Analysis
                                                      Units
                                      [C = Complex AU; I = Independent AU]
----------------------------------------------------------------------------------------------------------------
           Drainage basin                  Analysis unit        Type/Number of streams     Risk of  extirpation
----------------------------------------------------------------------------------------------------------------
Gila River..........................  Blue River.............  I.......................  Low Risk.
Salt River..........................  Ash Creek..............  I.......................  Low Risk.
Verde River.........................  Gap Creek..............  I.......................  Low Risk.
Verde River.........................  Roundtree Canyon.......  I.......................  Low Risk.
----------------------------------------------------------------------------------------------------------------

Future Condition Analysis

    We analyzed the future risk of extirpation of each AU using the 
same model we used to assess current condition. However, we added a 
metric to assess conservation measures. We used the current condition 
of nonnative aquatic species, water availability, and chub population 
structure as the baseline to analyze projected future impacts. As 
stated in the current condition, we modeled water availability using 
stream length as a surrogate for available habitat. To model projected 
future impacts from climate change, we applied a reduction in length to 
the baseline stream length (i.e., water availability) to all streams. 
Under the current condition, the nonnative aquatic species were 
evaluated in terms of the impacts from the community of nonnative 
aquatic species present in a stream and the known impacts to chubs from 
the nonnative aquatic species present in the stream. To project future 
impacts from nonnatives aquatic species, we applied an increase in the 
impacts from the community of nonnative aquatic species present to a 
percentage of streams. We did not project future impacts to chub 
population structure because the projected future risk to the chubs is 
what we are projecting. To measure conservation efforts, we projected 
the future establishment of new populations and the renovation of 
streams.
    Given our uncertainty regarding if or when streams or AUs occupied 
by chubs will experience an increase in nonnative aquatic species, a 
reduction in water in the future, or conservation actions, we have 
qualitatively forecasted what both species may have in terms of 
resiliency, redundancy, and representation under four different 
possible future scenarios based on our understanding of the risks to 
these species. Our modeling allowed us to review four future scenarios 
of risk to AUs from nonnative aquatic species and water availability. 
These scenarios extend to the year 2046, about 30 years from present. 
In addition, we included an assessment of the potential for future 
conservation actions within each scenario.
    To measure impacts from nonnative aquatic species in the future 
scenarios, we evaluated an increase in the level of impact from the 
nonnative aquatic species community across a percentage of streams 
because it is unlikely that all streams will be affected by increased 
impacts from nonnative aquatic species. It is more realistic that a 
portion of streams will have increased effects from nonnative aquatic 
species. Impacts due to reduction in water availability were

[[Page 60768]]

assumed to occur throughout all streams because impacts from climate 
change, the largest driver of water availability, occur at a landscape 
scale; however, the future scenarios incorporate various levels of 
climate change severity to account for the uncertainty in future 
climate change projections.
    We identified two levels of conservation: a high management option 
and a low management option. The high management option projects that 
there will be two streams that are renovated or secured (eliminating 
nonnatives), and two new populations will be established per species. 
The low management option only projects one new population being 
established per species. For the two new projected populations for each 
chub, we did not select real streams but identified a set of conditions 
to represent a proxy stream similar to what would be considered in 
selecting a real site for a new population. We randomly selected 
drainage basins where the new population sites would be implemented. 
For the purposes of the model, we assumed all of these conservation 
efforts would result in populations that have reproduction and 
recruitment.

Table 7--Future Scenarios Analyzed in the Model for Headwater Chub and Lower Colorado River Basin Roundtail Chub
                                                       DPS
----------------------------------------------------------------------------------------------------------------
                     Nonnative aquatic species                             Water              Conservation
--------------------------------------------------------------------    availability   -------------------------
                                                                    -------------------
                                   Percent of         Nonnative          Percent of         New populations,
           Scenario             streams impacted   community level      decrease in       renovation,  securing
                                 by nonnatives         increase        stream length
----------------------------------------------------------------------------------------------------------------
1............................                 13                  1                 -4  High management.
2............................                 13                  2                 -8  High management.
3............................                 13                  2                 -8  Low management.
4............................                 45                  1                -20  Low management.
----------------------------------------------------------------------------------------------------------------

    The below results are from the model analysis; however, it is 
important to note that our model does not capture all risks affecting 
these species. For analyzing the future condition, the model captures 
certain components contributing to the primary risks to the species 
(nonnative aquatic species and water availability) and conservation 
measures (establishing new populations and renovating existing 
populations). Although not incorporated into our model, we also 
considered additional risk from climate change and water loss due to 
anthropogenic factors (e.g., surface water diversion and groundwater 
pumping), which is part of the water availability factor we included in 
our model. However, we were not able to capture additional risk from 
climate change and water loss due to anthropogenic factors in the 
model. In addition, we assessed impacts from wildfire based on the 
wildfire risk map developed by the U.S. Forest Service. As clarified in 
the Risk Factors for Headwater Chub and the Lower Colorado River Basin 
Roundtail Chub DPS section of this proposed rule, we recognize that 
fire does not always result in adverse effects to these species. 
Further, we considered the demographic impacts to these risks and the 
reduction in range. We evaluated impacts from these additional risks to 
each AU and the species as a whole.
Future Condition Model Results
I. Headwater Chub
    The high management options projects that two new AUs will be 
established and two streams will be renovated. The low management 
options projects that one new AU will be established and no streams 
will be renovated. Consequently, scenarios 1 and 2 resulted in 10 AUs, 
instead of 8, because both of these scenarios incorporate the high 
management option. Scenarios 3 and 4 resulted in nine AUs due to the 
low management option projecting only one newly established population. 
As a result of the established populations and the renovation 
populations, the representation and redundancy of the species 
increased. However, the resiliency of some of the AUs is diminished due 
to the increased risks from nonnative aquatic species and reduced 
stream length.

                                           Table 8--Modeled Future Condition of Headwater Chub Analysis Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
        Analysis unit name            Current condition          Scenario 1             Scenario 2            Scenario 3               Scenario 4
--------------------------------------------------------------------------------------------------------------------------------------------------------
San Carlos Complex................  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Three Forks Complex...............  Low..................  Low..................  Low..................  Low.................  Moderate.
Lower Tonto Creek Network.........  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Upper Gunn Creek..................  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Upper Tonto Creek Complex.........  Low..................  Low..................  Low..................  Low.................  Low.
New Population A..................  Not applicable.......  Minor................  Minor................  Minor...............  Minor.
East Verde River Complex..........  Moderate.............  Low..................  Low..................  Moderate............  Moderate.
Fossil Creek......................  Minor................  Low..................  Moderate.............  Moderate............  Low.
Wet Bottom Creek..................  Low..................  Low..................  Low..................  Low.................  Low.
New Population B..................  Not applicable.......  Minor................  Minor................  Not applicable......  Not applicable.
--------------------------------------------------------------------------------------------------------------------------------------------------------

II. Lower Colorado River Basin Roundtail Chub DPS
    The high management options projects that two new AUs will be 
established and two streams will be renovated. The low management 
options projects that one new AU will be established and no streams 
will be renovated. Consequently, scenarios 1 and 2 resulted in 17 AUs, 
instead of 15, because both of these scenarios incorporate the high 
management option. Scenarios 3 and 4 resulted in 16 AUs due to the low 
management option only projecting one newly established

[[Page 60769]]

population. As a result of the established populations and the 
renovation populations, the representation and redundancy of the 
species increased. However, the resiliency of some of the AUs is 
diminished due to the increased risks from nonnative aquatic species 
and reduced stream length. However, the increased risk did not elevate 
the ranking to the next risk category.

                            Table 9--Modeled Future Condition of Lower Colorado River Basin Roundtail Chub DPS Analysis Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
           Analysis unit              Current condition          Scenario 1             Scenario 2            Scenario 3               Scenario 4
--------------------------------------------------------------------------------------------------------------------------------------------------------
Boulder Creek Complex.............  Low..................  Low..................  Low..................  Low.................  Low.
Burro Creek Complex...............  Low..................  Low..................  Low..................  Low.................  Low.
Santa Maria River Complex.........  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Trout Creek Complex...............  Low..................  Low..................  Low..................  Low.................  Moderate.
New Population C..................  Not applicable.......  Minor................  Minor................  Minor...............  Minor.
Aravaipa Creek....................  Low..................  Low..................  Low..................  Low.................  Low.
Eagle Creek.......................  Low..................  Low..................  Low..................  Low.................  Low.
Upper Gila River Complex..........  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Chevelon Creek....................  Low..................  Moderate.............  Moderate.............  Moderate............  Moderate.
Clear Creek Complex...............  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Salome Creek......................  High.................  High.................  High.................  High................  High
Upper Salt River Complex..........  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Confluence Reach Complex..........  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
Fossil Creek......................  Low..................  Low..................  Low..................  Low.................  Low.
Upper West Clear Creek............  Minor................  Minor................  Minor................  Minor...............  Low.
Verde River Complex...............  Moderate.............  Moderate.............  Moderate.............  Moderate............  Moderate.
New Population D..................  Not applicable.......  Minor................  Minor................  Not applicable......  Not applicable.
--------------------------------------------------------------------------------------------------------------------------------------------------------

III. Lower Colorado River Basin Roundtail Chub DPS's Newly Established 
Sites
    There are currently four established sites for the lower Colorado 
River basin roundtail chub DPS (see Table 10, below), and each site is 
an individual AU. These are relatively newly established AUs, and their 
success is unclear at this time. The Blue River site is the only site 
that has demonstrated reproduction. The remaining three sites have yet 
to show any reproduction. Consequently, we analyzed these AUs 
separately because of the uncertainty of their success.
    Results for the Lower Colorado River basin roundtail chub DPS newly 
established populations (Blue River, Ash Creek, Gap Creek, and 
Roundtree Canyon) are captured in Table 10.

                 Table 10--Modeled Future Condition of Lower Colorado River Basin Roundtail Chub DPS's Newly Established Analysis Units
                                                          [C = Complex AU; I = Independent AU]
--------------------------------------------------------------------------------------------------------------------------------------------------------
         Drainage basin             Analysis unit          Current           Scenario 1          Scenario 2          Scenario 3           Scenario 4
--------------------------------------------------------------------------------------------------------------------------------------------------------
Gila River.....................  Blue River........  Low...............  Low...............  Moderate..........  Moderate..........  Low.
Salt River.....................  Ash Creek.........  Low...............  Moderate..........  High..............  High..............  High.
Verde River....................  Gap Creek.........  Moderate..........  Moderate..........  High..............  High..............  High.
Verde River....................  Roundtree Canyon..  Low...............  Moderate..........  High..............  High..............  High.
--------------------------------------------------------------------------------------------------------------------------------------------------------

Summary
    Based on the risk factor discussion above, scenarios 1 and 3 are 
the most likely scenarios. We are moderately certain that nonnative 
aquatic species will not impact 45 percent of the streams throughout 
the range of either species. Consequently, scenario 4 is not a 
realistic scenario, but it does demonstrate a negative future condition 
for comparison to the other scenarios. Scenario 2 is similar to 
scenario 3, with different conservation measures (see Table 7, above). 
Given the uncertainty in the success and feasibility of the 
conservation measures, we consider it important to evaluate a scenario 
with low management options. Consequently, we analyzed the results from 
scenario 3, rather than scenario 2. Scenarios 1 and 3 vary in the level 
of impacts from nonnative aquatic species, amount of decrease in stream 
length, and the level of conservation measures. There is uncertainty in 
the level of impacts from nonnative aquatic species and climate change. 
Further, there is uncertainty in the level, feasibility, or 
effectiveness of conservation measures. By considering both scenario 1 
and 3, we address some of this uncertainty. Therefore, the most 
informative scenarios are scenarios 1 and 3, where impacts from 
nonnative aquatic species are likely to increase in a percentage of 
streams across the range of each species, stream lengths will be 
reduced, and some level of conservation management will be implemented. 
In addition to the model results, we also assessed risk from wildfire, 
additional risk from climate change, water loss due to anthropogenic 
factors, demographic impacts from these risks factors, and the 
reduction in range, as described in the Risk Factors for Headwater Chub 
and the Lower Colorado River Basin Roundtail Chub DPS and Current 
Condition sections, above.

Viability

    In the SSA Report, we used AUs to describe the populations of 
chubs. The AUs were delineated based on the hydrological connectivity 
of currently occupied streams and the ability of chubs to move within 
or among streams. There are two types of AUs considered in this SSA 
Report: (1) Those composed of one occupied stream, referred to as 
independent AUs; and (2) those composed of two or more hydrologically 
connected occupied streams, referred to as complex AUs.

[[Page 60770]]

Headwater Chub
    Currently, at least 48 percent of the estimated historical range is 
occupied and there has been no more than a 52 percent reduction in 
range. Occupancy is within 22 streams, with a collective minimum of 432 
km (268 mi) of available habitat, dispersed over eight AUs across three 
drainage basins. Three (38 percent) AUs are isolated, and five (62 
percent) AUs have some hydrologic connection to each other. Headwater 
chub populations are naturally fragmented due to the individual 
hybridization events that created the species. Due to the multiple 
hybridization events in separate streams that likely gave rise to 
headwater chub, there are differences between the occupied streams 
across the occupied range deriving from the specifics of the founding 
populations and subsequent events that may have reduced population 
sizes that affected that diversity (Dowling et al. 2008, pp. 10-11). 
Most of their genetic variation occurs among populations, each of which 
tends to be distinctive. Each AU is geographically isolated from the 
other AUs even in the same drainage basin. The significance of 
isolation in shaping each population highlights the importance of 
maintaining each independently to preserve the unique genetic variation 
(Dowling et al. 2008, p. 2). Maintaining representation in the form of 
genetic or ecological diversity is important to retaining the capacity 
of the chub to adapt to future environmental changes.
    Six of the eight AUs are located in adjoining drainages: three in 
the Salt River (upper and lower Tonto Creek complexes and Gunn Creek 
independent AUs) and three in the Verde River (East Verde River complex 
and Fossil and Wet Bottom creeks independent AUs). The result is a 
distribution with 64 percent of the occupied area within immediate 
proximity to each other in two adjacent drainage basins, which is a 
concern for catastrophic events (such as floods). The remaining two 
complexes, San Carlos River and Three Forks, are in separate drainage 
basins from the other six and each other, and are not likely to be 
affected by the same catastrophic natural or anthropogenic event. This 
configuration creates a concern for maintaining redundancy in the 
future due to a catastrophic event.
    There are eight streams from various AUs of approximately 5 km (3 
mi) or less in length. These streams are at a higher risk of 
extirpation from catastrophic events than are longer streams. Further, 
there are two AUs of approximately 5 km (3 mi) or less, in which a 
catastrophic event could result in the loss of these AUs and reduce 
redundancy of the species. In addition, San Carlos River and its 
tributary Ash Creek within the Gila River drainage basin are on tribal 
lands, and we have high uncertainty regarding the presence of chubs.
Lower Colorado River Basin Roundtail Chub DPS
    Currently, about 47 to 52 percent of historical range is occupied 
(or 48 to 53 percent reduction in range). Occupied areas are dispersed 
over 35 streams within 15 AUs across five drainages. Information about 
roundtail chub indicated that historically there was greater 
connectivity and subsequent relatedness over the region, and 
development of populations in isolation from other roundtail chub was 
not the normal condition across most of the historical range except in 
the Bill Williams River and Little Colorado River drainages. Unlike the 
headwater chub, the roundtail chub's historical connectivity within the 
Gila, Salt, and Verde Rivers promoted less genetic diversity over the 
range; however, the Bill Williams and Little Colorado rivers are 
isolated from that connectivity and are more unique. However, roundtail 
chub are extirpated from several large riverine streams that provided 
connectivity across most of the historically occupied range. This has 
resulted in the recent isolation of AUs even within the same drainage 
basin. Nine AUs (about 60 percent) are isolated and are not able to 
naturally recolonize. If a catastrophic event such as wildfire or 
severe drought occurs in one of these nine populations, it could be 
extirpated. Variation within populations and connectivity may be more 
of an issue for roundtail chub in the DPS than with headwater chub. 
Maintaining representation in the form of genetic or ecological 
diversity is important to retaining the capacity of the roundtail chub 
to adapt to future environmental changes.
    There are eight streams from various AUs of approximately 5 km (3 
mi) or less. These streams are at a higher risk of extirpation from 
catastrophic events than are longer streams. In addition, one AU is 
approximately 5 km (3 mi) or less, putting it at higher risk of 
extirpation due to a catastrophic event, leading to reduced redundancy. 
In addition, there seven streams within the Upper Salt River drainage 
basin located on tribal lands where we have high uncertainty regarding 
the presence of chubs. We consider these streams occupied, but this 
could be overestimating the range of the headwater chub and the lower 
Colorado River basin roundtail chub DPS.
    In the Little Colorado River drainage basin, loss of one of the two 
occupied streams would impair redundancy. For the Verde River Complex 
and Upper Salt River Complex AUs, loss of any stream with documentation 
of recruitment would likely impair the entire complex. The survey data 
suggest that some streams in the Verde River Complex and Upper Salt 
River Complex AUs have more recruitment events than others but we do 
not fully understand how the chub populations are maintained across the 
entire complex. Under these conditions, loss of a stream with sustained 
recruitment would affect redundancy across the entire AU. For the Gila 
River drainage basin, loss of the Eagle Creek AU would effectively 
eliminate the upper portion of the Gila River drainage basin. The loss 
of the Aravaipa Creek AU would effectively eliminate the lower portion 
of the Gila River drainage basin. For the Bill Williams River drainage 
basin, the loss of one AU complex would reduce redundancy but not 
necessarily impair redundancy. However, the loss of both AU complexes 
would impair redundancy because of the potential for loss of a genetic 
management unit.

Determinations

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal Lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may list a species based 
on (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. Listing actions may be warranted based on any of 
the above threat factors, singly or in combination. Under section 
4(b)(1)(a), the Secretary is to make endangered or threatened 
determinations under section 4(a)(1) solely on the basis of the best 
scientific and commercial data available to her after conducting a 
review of the status of the species and after taking into account 
conservation efforts by States or foreign nations. We have carefully 
assessed the best scientific and commercial data available regarding 
the past, present, and future threats to the headwater chub and lower 
Colorado River basin roundtail chub DPS.

[[Page 60771]]

    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We used the best available scientific 
and commercial data to evaluate the viability (and thus risk of 
extinction) for the headwater chub and the lower Colorado River basin 
roundtail chub DPS to determine if they meet the definition of an 
endangered or threatened species.

Summary of Analysis

    The biological information we reviewed and analyzed as the basis 
for our findings is documented in the SSA Report (Service 2015, 
entire), a summary of which is provided in the Background section of 
this proposed rule. The projections for the condition of populations 
are based on our expectations of the risks (in other words, threats) 
that may have population-level effects currently or in the future. The 
risks we evaluated in detail are habitat loss and degradation due to 
groundwater pumping and surface water diversion (Factor A from the 
Act), and predation, competition, and harassment from nonnative aquatic 
species (Factors C and E from the Act). For nonnative aquatic species 
and reduction in water, we also considered the exacerbating effects of 
climate change (Factor E from the Act). We reviewed, but did not 
evaluate in further detail because of a lack of population-level 
effects, the effects of recreation (Factor B from the Act), grazing, 
forestry practices, roads, and mining (Factor A from the Act). The 
overall results of the status assessment found that the best available 
information indicates that the range of the headwater chub and the 
lower Colorado River basin roundtail chub DPS have decreased, with 
multiple streams now extirpated, likely due to nonnative aquatic 
species and loss of habitat (i.e., water).
    The purpose of the status assessment was to characterize the future 
condition of the headwater chub and the lower Colorado River basin 
roundtail chub DPS in the face of risks and conservation efforts 
described above in the Background section. In the SSA Report, we 
described the viability of the headwater chub and the lower Colorado 
River basin roundtail chub DPS in terms of resiliency, redundancy, 
representation now, including the next 5 years, and over the next 30 
years under four likely scenarios. We have determined that scenarios 1 
and 3 are the most likely future scenarios. Our forecasts take into 
consideration the four newly established sites and one restoration site 
for the lower Colorado River basin roundtail chub DPS. In addition, our 
analysis considers wildfire risk, additional climate change impacts, 
water loss due to anthropogenic actions, and demographic impacts from 
these factors and the reduction in the range. We recognize the fire 
does not always result in adverse effects to these chubs. We evaluated 
impacts from these additional risks to each AU and the headwater chub 
and the lower Colorado River basin roundtail chub DPS as a whole.

Application of Analysis to Determinations

    The fundamental question before the Service is whether the 
headwater chub and the lower Colorado River basin roundtail chub DPS 
warrants protection as endangered or threatened under the Act. To 
determine this, we evaluate the projections of extinction risk, 
described in terms of the condition and distribution of current 
(including the next 5 years) and future populations. As population 
condition declines and distribution shrinks, species' extinction risk 
increases and overall viability declines.
    As described in the determinations below, we first evaluated 
whether the headwater chub and the lower Colorado River basin roundtail 
chub DPS are in danger of extinction throughout their ranges now (an 
endangered species). We then evaluated whether they are likely to 
become in danger of extinction throughout their ranges in the 
foreseeable future (a threatened species). We finally considered 
whether the headwater chub and the lower Colorado River basin roundtail 
chub DPS are an endangered or threatened species in a significant 
portion of their ranges (SPR).

Headwater Chub Determination

Endangered Species Throughout Range
I. Standard
    Under the Act, an endangered species is any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range.'' Because of the fact-specific nature of listing determinations, 
there is no single metric for determining if a species is currently in 
danger of extinction. We used the best available scientific and 
commercial data to evaluate the viability (and thus risk of extinction) 
for the headwater chub to determine if it meets the definition of an 
endangered species. In this proposed rule, we use a description of the 
condition of populations to describe the viability of headwater chub 
then determine the species' status under the Act.
II. Evaluation
    To assist us in evaluating the status of the headwater chub, we 
evaluated the risk factors that we found may have potential population-
level effects now. This included nonnative aquatic species, water 
availability, and chub population structure, which we assessed in our 
model. In addition, this included current risk from wildfire, climate 
change, water loss due to anthropogenic actions, and demographic 
effects from these risks factors and the reduction in range; however, 
these were not analyzed in the model. All of these factors affect the 
resiliency of AUs for the headwater chub.
    For headwater chub, at least 48 percent of the estimated historical 
range remains and no more than a 52 percent of the range has been 
reduced from the historical range. Nonnative aquatic species occupy 
almost all currently occupied chub streams, and we analyzed impacts to 
these streams and AUs through the model. Nonnative aquatic species and 
chubs have coexisted for some time in several of these streams, but the 
reasons for this are unclear. There are three streams for headwater 
chub that are currently free of nonnative aquatic species into which 
nonnatives could expand or be introduced.
    In the model, we analyzed the stream length as a measure of water 
availability. This provided a current condition of the amount of water 
in a stream at the driest time of year. This captured climate change 
and anthropogenic action (surface water diversions and groundwater 
pumping) impacts to the stream. Wildfire is not analyzed in the model, 
but we did consider impacts from wildfire. Currently, wildfire could 
occur almost anywhere within the range of this species and impact one 
or more streams or entire AUs. However, impacts to the headwater chub 
are dependent on the severity, location, and timing of the fire, as 
well as the size of the stream.
    Since this species developed as a result of multiple independent 
hybridization events over time (Rinne 1976; Rosenfeld and Wilkinson 
1989; DeMarais et al. 1992; Dowling and DeMarais 1993; Minckley and 
DeMarais 2000; Gerber et al. 2001; Schwemm 2006; Sch[ouml]nhuth et al. 
2014), it is important to maintain it independently to preserve the 
unique genetic variation (Dowling et al. 2008, p. 2). The genetic 
diversity of headwater chub is best represented in differences within 
its

[[Page 60772]]

populations, each of which tends to be distinctive.
    The renovation effort in Fossil Creek for headwater chub (and for 
roundtail chub in the lower Colorado River basin) has proven 
successful, but such an effort requires a large commitment of resources 
including funding and personnel.
III. Finding for Headwater Chub
    Our review found that eight AUs currently exist within the 
historical range of the headwater chub across three drainage basins. We 
defined the minor risk category as a 0 to 5 percent current risk of 
extirpation, the low risk category as a 6 to 30 percent current risk of 
extirpation, and the moderate risk category as a 31 to 60 percent 
current risk of extirpation. The model output categorized one AU as 
minor risk, three AUs as the low risk, and four as the moderate risk 
categories.
    Four AUs are projected as currently having a minor or low risk of 
extirpation. We consider the one AU in the minor risk category, Fossil 
Creek, to be resilient because it contains very few nonnative aquatic 
species, it has a stream length of over 15 km (9 mi), and chub 
population structure is high (meaning chubs are abundant and 
recruitment is high). All these components increase the AU's ability to 
withstand a stochastic event such as wildfire and weather, which are 
the other risks we considered in our assessment. Based on this, 
resiliency is sufficient for this AU, and the risk of extirpation is 0 
to 5 percent.
    Although less resilient than an AU in the minor risk category, the 
AUs in the low risk category are also considered resilient, because 
they have low nonnative aquatic species, sufficient stream length, and/
or good chub population structure (chubs are common to abundant and 
recruitment is moderate to high). These components increase the AUs' 
ability to withstand a stochastic event such as wildfire and drought, 
which are the other risks we considered in our assessment. However, 
their ability to withstand a stochastic event is less than an AU in the 
minor risk, and the range of extirpation risk is greater (6 to 30 
percent). The range in risk of extirpation is a factor of the 
variability in the level of impacts from nonnative aquatic species, 
water availability, and chub population structure, as well as the 
uncertainty in the species' response from these risks factors because 
each AU is different.
    Impacts from nonnative aquatic species and water availability, as 
well as wildfire, climate change, and demographics, are affecting AUs 
in the minor and low risk categories, but these AUs are currently 
maintaining chubs and are therefore likely to withstand a stochastic 
event. In addition, there are two AUs in the moderate risk category 
that are close to the low risk category score, indicating that while 
they are in the moderate category they are at the low end of this 
category (i.e., closer to low risk).
    While impacts from climate change are likely currently, and are 
impacting chub populations at some scale, they are not having 
population-level impacts to all AUs at this time.
    Nonnative aquatic species occur in all but three streams that 
headwater chub occupy. While chubs coexist with nonnative aquatic 
species in several streams, this does not mean that nonnative aquatic 
species are not impacting chubs; however, the AUs are persisting 
currently.
    We consider the species to have sufficient redundancy and 
representation, and a number of sufficiently large populations, so that 
the species is able to withstand catastrophic events. The four AUs 
identified as minor and low risks are currently spread over a large 
geographical area, such that all the AUs are highly unlikely to 
experience a catastrophic event that would impact all AUs now. Further, 
the current range of the species includes AUs that represent the known 
diversity of ecological settings and genetic materials for the 
headwater chub. The current and ongoing threats are not likely to 
impact all remaining populations significantly now. Certain risks, such 
as climate change, move slowly across the landscape, and demographic 
impacts take time to impact a population. The increase or spread of 
nonnative aquatic species moves faster than climate change or 
demographics, but it will likely take a few years for a nonnative 
aquatic species to expand in a currently occupied stream or become 
established in a new stream. Wildfire is likely to have immediate 
impacts, but it is highly unlikely that wildfire will impact all AUs at 
the current time. As a result, it is unlikely that a single stochastic 
event (e.g., drought, wildfire) or catastrophic event will affect all 
known extant populations equally or simultaneously now. It would 
require several stochastic events or catastrophic events over a number 
of years to bring the headwater chub to the brink of extinction due to 
those factors.
    This estimate of the condition and distribution of populations 
provides sufficient resiliency, representation, and redundancy for the 
species. The primary threats to the species (nonnative aquatic species, 
water availability, and climate change) are not currently having 
population-level effects to all AUs across the range of the headwater 
chub. Catastrophic or stochastic events in the present are not likely 
to have population-level impacts to all AUs; consequently the risk of 
extinction is sufficiently low that the species does not meet the 
definition of endangered under the Act. Based on the above information, 
we conclude that the headwater chub does not meet the definition of an 
endangered species under the Act.
Threatened Species Throughout Range
    Having found that the headwater chub is not endangered throughout 
its range, we next evaluated whether this species is threatened 
throughout its range.
I. Standard
    Under the Act, a threatened species is any species that is ``likely 
to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' The foreseeable 
future refers to the extent to which the Secretary can reasonably rely 
on predictions about the future in making determinations about the 
future conservation status of the species (U.S. Department of Interior, 
Solicitor's Memorandum, M-37021, January 16, 2009). A key statutory 
difference between an endangered species and a threatened species is 
the timing of when a species may be in danger of extinction, either now 
(endangered species) or in the foreseeable future (threatened species). 
The foreseeable future refers to the extent to which the Secretary can 
reasonably rely on predictions about the future in making 
determinations about the future conservation status of the species.
II. Foreseeable Future
    To assist us in evaluating the status of the species in the 
foreseeable future, we evaluated the risk factors that we found may 
have potential population-level effects over time. This included 
nonnative aquatic species, water availability, and conservation 
actions, which we assessed in our model. In addition, we considered the 
future risk from wildfire, water loss due to future anthropogenic 
actions, and demographic impacts from these risk factors, as well as 
reduction in range. In considering the foreseeable future, we 
forecasted the future status of the headwater chub as described by the 
future condition of the AUs. This projected future condition was based 
on the risk factors and conservation actions affecting the species, and 
the

[[Page 60773]]

uncertainties associated with these factors and actions. We consider 30 
years from now a reasonable time to reliably predict the future 
conservation status of this species.
    The best available information indicates that we have a high level 
of certainty out to 30 years for climate change risks, which is an 
essential consideration for the foreseeable future. Therefore, our 
analysis of the status of the species to the foreseeable future uses a 
timeframe of 30 years. The outputs of Jaeger et al.'s (2014, entire) 
downscaled climate forecasting models project climate scenarios to 
midcentury (approximately 2050) (IPCC 2014; Jaeger et al. 2014, 
entire). Jaeger et al. (2014, entire) focuses on the Verde River Basin 
in Arizona over current (1988-2006) and midcentury (2046-2064) time 
periods. This study was useful because the headwater chub occurs in the 
Verde River Basin and the study focuses on impacts to native fish. 
Since the potential effects of climate change on flowing regions within 
streams and connectivity within and among streams, and the exacerbated 
impacts from nonnative aquatic species and demographics (i.e., age 
structure and genetics) due to climate change, were primary 
considerations in our status assessment, we considered climate change 
predictions essential in the foreseeable future. However, we did not 
extend our forecasting beyond the midcentury because of uncertainty in 
the climate change models and in the response of the species beyond 
approximately 2046.
III. Evaluation
    To assist us in evaluating the status of the species, we evaluated 
the risk factors that we found may have potential population-level 
effects over a 30-year time period. This included nonnative aquatic 
species, water availability, and conservation actions, which we 
assessed in our model. In addition, we considered the future risk from 
fire, additional climate change, future anthropogenic actions, and 
demographic effects from these risks factors, as well as reduction in 
range; however, these were not analyzed in the model. We evaluated 
impacts from these additional risks to each AU and the species as a 
whole.
    Chubs are affected not only by the quantity and quality of water, 
but also by the timing and spatial distribution of water. In the model, 
we analyzed the reduction in stream length as an impact from climate 
change. However, climate change models project that over the next 50 
years: (1) Future water levels and stream base flows are expected to 
continue to decrease in the Verde River in the lower Colorado River 
basin; (2) the frequency of stream drying events in the Verde Valley is 
expected to increase; (3) the length of the remaining flowing reaches 
of streams in the Verde Valley (or region) will be reduced; and (4) 
network-wide hydrologic connectivity for native fishes will be reduced 
(both over the course of the year and during spring spawning months). 
Climate change is also projected to alter the timing and amount of 
snowmelt and monsoon rains, and the frequency and duration of droughts. 
Climate change will also increase temperature, resulting in increased 
evaporation. Climate change is also likely to exacerbate the effects of 
water loss, reduction in hydrological connectivity, nonnatives, and 
species interactions (impacting demographics). All of these factors 
reduce the resiliency of AUs for the headwater chub. However, the 
certainty of the model projections decreases as the projected timeframe 
increases. Further, the severity of climate change impacts depicted in 
climate models varies depending on the scenario being evaluated, with 
some projecting low changes (e.g., increased ambient temperature and 
decreased rainfall) in carbon dioxide and others projecting high 
changes. To address this uncertainty, we considered different levels of 
impacts to these species under various scenarios. Impacts from climate 
change are likely to affect all streams and AUs within the range of the 
headwater chub over the next 30 years.
    In the model, we analyzed the stream length as a measure of water 
availability. This provided a current condition of the amount of water 
in a stream at the driest time of year. This captured climate change 
and anthropogenic action (surface water diversions and groundwater 
pumping) impacts to the stream. Wildfire is not analyzed in the model, 
but we did consider impacts from wildfire. Currently, wildfire could 
occur almost anywhere within the range of this species and impact one 
or more streams or entire AUs. However, impacts to the headwater chub 
are dependent on the severity, location, and timing of the fire, as 
well as the size of the stream.
    As part of the foreseeable future, we also considered the likely 
reduction in water availability as a result of increased human demand 
for water, resulting in increased surface water diversions and 
groundwater pumping. Demand for water is highly likely to increase as 
human populations are predicted to increase, affecting the timing, 
amount, and distribution of water within streams. However, population 
growth, and the exact location of that population growth, is uncertain. 
Further, the timing and amount of water consumed is uncertain. To 
address this uncertainty, we considered different levels of impacts to 
a subset of streams or AUs.
    Nonnative aquatic species occupy almost all currently occupied chub 
streams, and we analyzed impacts to these streams and AUs through the 
model. Nonnative aquatic species and chubs have coexisted for some time 
in several of these streams, but the reasons for this are unclear. We 
expect that nonnative aquatic species will continue to persist in most 
if not all of the streams they currently occupy and that nonnative 
impacts will increase in a percentage of streams across the range of 
this species. In addition, there are three streams for headwater chub 
that are currently free of nonnative aquatic species into which 
nonnatives could expand or be introduced.
    The projected effects to chubs from nonnative aquatic species are 
likely to be exacerbated by climate change, but this was not analyzed 
in the model. However, we do consider this in our analysis. As the 
available watered segments decrease, the interactions between nonnative 
aquatic species and chubs increase, with more larvae and young-of-the-
year removed from the chub populations dues to predation by nonnative 
aquatic species. In addition, resources become more limited, and the 
competition for these resources increases. Further, the reduction in 
water will likely decrease the water quality (e.g., decreased dissolved 
oxygen, temperature increases, changes in pH, and nutrient loading), 
which nonnative aquatic species are likely more capable of adapting to 
than chubs.
    Since this species developed as a result of multiple independent 
hybridization events over time (Rinne 1976; Rosenfeld and Wilkinson 
1989; DeMarais et al. 1992; Dowling and DeMarais 1993; Minckley and 
DeMarais 2000; Gerber et al. 2001; Schwemm 2006; Sch[ouml]nhuth et al. 
2014), it is important to maintain the species independently to 
preserve the unique genetic variation (Dowling et al. 2008, p. 2). The 
genetic diversity of headwater chub is best represented in differences 
within its populations, each of which tends to be distinctive.
    We have a moderate to high level of uncertainty regarding the 
success of the establishment of new populations. (For example, of the 
four newly established populations of roundtail chub in the lower 
Colorado River basin only one (Blue River) has demonstrated 
reproduction. One potential factor is the

[[Page 60774]]

size of the site--Blue River is much larger than the other three 
sites.) The renovation effort in Fossil Creek has proven successful. 
However, such an effort requires a large commitment of resources 
including funding and personnel. While attempts at establishing new 
populations in the future are likely, the success of these sites is 
uncertain. In addition, the availability of funds and personnel in 
renovating another site like Fossil Creek is uncertain. Future 
scenarios projected in our model include conservation actions 
(establishment of new populations and securing sites), and the 
uncertainty of success of these sites.
IV. Finding for Headwater Chub
    We used the same categories to categorize the risk of extirpation 
in the foreseeable future (until 2046) as discussed above in the ``III. 
Evaluation'' section. We determined that scenarios 1 and 3 are most 
likely and therefore most useful in making our determination. The model 
output for scenario 1 projected 10 AUs due to the high management 
option projecting two newly established populations and two renovation 
sites. The projected risk of extirpation by 2046 for the 10 AUs were: 
two AUs in minor risk, five in low risk, and three in moderate risk. 
The two AUs in minor risk of extirpation are the newly established 
sites, and two of the five AUs in low risk are the renovation sites. 
Scenario 3 projected nine AUs due to the low management option 
projecting only one newly established population. The projected risk of 
extirpation by 2046 for the nine AUs were: one AU in minor risk, three 
in low risk, and five in moderate risk. The one AU in the minor risk is 
a newly established site.
    We consider AUs within the minor to low risk categories to have 
sufficient resiliency in the future because they contain very few 
nonnative aquatic species, have long stream length, and have a high 
chub population structure. All these components increase the AUs' 
ability to withstand a stochastic event such as wildfire and weather, 
which are the other risks we considered in our assessment. Under the 
current condition, the one AU (Fossil Creek) that ranked in the minor 
risk category was projected to experience an increase in nonnative 
aquatic species and a reduction in stream length in the future 
scenarios. These projected impacts resulted in this AU ranking in the 
low risk under scenario 1 and the moderate risk under scenario 3. This 
demonstrates the impacts that nonnative aquatic species and water 
availability have on AUs. The reduced resiliency of this AU affects the 
redundancy and representation of the species as a whole.
    The two AUs in scenario 1, and the one AU in scenario 3, that 
ranked in the minor risk category are the projected newly established 
sites. In addition, one of the AUs in the low risk category under 
scenario 1 is a renovation site, which under the current condition was 
ranked as moderate risk. Given the high uncertainty in the success of 
newly established and renovated sites, these are not reliably 
considered resilient in the future, and therefore we did not consider 
these in our determination. This leaves four AUs that ranked in the low 
risk category in scenario 1 and three in scenario 3. Although less 
resilient than an AU in the minor risk category, the AUs in the low 
risk category are also considered resilient, because they have low 
nonnative aquatic species, sufficient stream length, and good chub 
population structure. Two of these rank closely to the moderate risk 
category in scenario 1 and three in scenario 3. This leaves two AUs 
under scenario 1 and scenario 3 that we consider resilient enough to 
withstand future stochastic events.
    Nonnative aquatic species occur in all but three streams that 
headwater chub occupy. While chubs coexist with nonnative aquatic 
species in several streams, this does not mean that nonnatives are not 
impacting chubs. Further, climate change is likely to exacerbate water 
loss, reduction in hydrological connectivity, nonnative aquatic 
species, and species interactions (impacting demographics), resulting 
in increased competition from and predation by nonnatives. Since 
climate change is likely to affect all streams to varying degrees, it 
is likely that impacts from nonnative aquatic species will increase in 
a portion of streams throughout the range of the headwater chub. The 
level of increased impacts from nonnative aquatic species is dependent 
on the condition of the chubs and nonnatives in that AU, and the level 
of impacts from climate change.
    The occurrence of wildfire within the headwater chub's range is 
highly likely. However, the severity, location, and impacts to chubs 
are uncertain. Over a 30-year period, multiple wildfires could impact 
multiple AUs. Impacts could range from loss of individuals to loss of 
streams to loss of AUs. Demand for water is highly likely to increase 
as human populations are predicted to increase, affecting the timing, 
amount, and distribution of water within streams. In addition, the 
synergistic impacts from the increased effects from wildfire, 
additional impacts from climate change, water loss due to anthropogenic 
actions, and demographic effects from these risks factors increase the 
likelihood and severity of stochastic impacts across the range of the 
species.
    The projected number of AUs in moderate risk is three and five 
under scenarios 1 and 3, respectively (33 to 55 percent, respectively). 
These AUs have moderate to high nonnative aquatic species, low to 
moderate stream lengths, and low to moderate chub abundance. These are 
not considered resilient enough to withstand stochastic events in the 
foreseeable future. As stated above, the synergistic impacts from the 
increased impacts from wildfire, additional impacts from climate 
change, water loss due to anthropogenic actions, and demographic 
effects from these risks factors increase the likelihood and severity 
of stochastic impacts across the range of the species. This increase in 
likelihood and severity increases the risk of extirpation for these AUs 
in the moderate risk category. Over the 30-year period of the 
foreseeable future, the risk from demographic (change in age structure 
and recruitment of populations) and environmental stochasticity 
(wildfire and weather) may have effects to all AUs (or populations) in 
the moderate risk category.
    In addition, the model projects that three (38 percent) AUs would 
be isolated and only five (62 percent) AUs would retain some hydrologic 
connection. There are projected to be eight streams of approximately 5 
km (3 mi) or less in length. These streams would be at a higher risk of 
extirpation due to stochastic and catastrophic events. The loss of 
these streams from an AU would reduce the resiliency of that AU. 
Further, there would be two AUs of approximately 5 km (3 mi) or less. 
These AUs would be at a higher risk of extirpation due to stochastic 
and catastrophic events.
    The AUs are projected to exist across the historical range; 
however, 64 percent of the AUs would occupy an area within immediate 
proximity to each other in two adjacent drainage basins, increasing 
their risk from catastrophic events (such as wildfire). The 
distribution of the AUs in the future could possibly be adequate to 
support representation and redundancy for the species, if a sufficient 
number of AUs were projected to be resilient. However, AUs that are not 
resilient cannot reliably contribute to redundancy or representation, 
and only two to three of the eight AUs are considered resilient. 
Further, the redundancy and representation of the species is diminished 
based on the projected future condition of the AUs, and the

[[Page 60775]]

potential impacts from wildfire, additional impacts from climate 
change, water loss due to anthropogenic factors (e.g., surface water 
diversion and groundwater pumping), and the demographic impacts from 
these risk factors, as well as the inability to rely on conservation 
measures. Redundancy is reduced because threats could potentially 
affect multiple AUs across the range of the headwater chub over the 
next 30 years and several of these AUs are projected to have diminished 
resiliency. Consequently, the ability of the species to withstand 
catastrophic events will likely be impaired.
    The significance of isolation in shaping each population highlights 
the importance of maintaining each independently to preserve the unique 
genetic variation (Dowling et al. 2008, p. 2). Maintaining 
representation in the form of genetic or ecological diversity is 
important to retaining the capacity of the headwater chub to adapt to 
future environmental changes. The loss of an AU could result in reduced 
representation due to a loss of genetic diversity. Representation is 
projected to be reduced because the loss of AUs results in a decrease 
in the unique genetic management units.
    Because this estimate of the condition and distribution of 
populations in the foreseeable future would not provide sufficient 
resiliency, representation, and redundancy for the species, the risk of 
extinction is sufficiently high in the foreseeable future to meet the 
definition of a threatened species under the Act. We conclude that the 
headwater chub meets the definition of a threatened species under the 
Act.
Significant Portion of Its Range for Headwater Chub
    Under the Act and our implementing regulations, a species may 
warrant listing if it is endangered or threatened throughout all or a 
significant portion of its range. Because we have determined that 
headwater chub is threatened throughout all of its range, no portion of 
its range can be ``significant'' for purposes of the definitions of 
``endangered species'' and ``threatened species.'' See 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'' (79 FR 37578; July 1, 2014).

Lower Colorado River Basin Roundtail Chub DPS Determination

Endangered Species Throughout Range
I. Standard
    Under the Act, an endangered species is any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range.'' Because of the fact-specific nature of listing determinations, 
there is no single metric for determining if a species is currently in 
danger of extinction. We used the best available scientific and 
commercial data to evaluate the viability (and thus risk of extinction) 
for the lower Colorado River basin roundtail chub DPS to determine if 
it meets the definition of an endangered species. In this 
determination, we used a description of the condition of populations to 
describe the viability of the lower Colorado River basin roundtail chub 
DPS and then determine the DPS's status under the Act.
II. Evaluation
    To assist us in evaluating the status of the DPS, we evaluated the 
risk factors that we found may have potential population-level effects 
now. This included nonnative aquatic species, water availability, and 
chub population structure, which we assessed in our model. In addition, 
this included current risk from wildfire, climate change, water loss 
due to anthropogenic actions, and demographic effects from these risks 
factors, as well as the reduction in range. However, these were not 
analyzed in the model. All of these factors affect the resiliency of 
AUs for the lower Colorado River basin roundtail chub DPS.
    For roundtail chub in the lower Colorado River basin, at least 43 
percent of the historical range remains and no more than a 57 percent 
of the range has been reduced from the historic range. Nonnative 
aquatic species occupy almost all currently occupied chub streams, and 
we analyzed impacts to these streams and AUs through the model. 
Nonnative aquatic species and chubs have coexisted for some time in 
several of these streams, but the reasons for this are unclear. There 
are three streams occupied by the lower Colorado River basin roundtail 
chub DPS that are currently free of nonnative aquatic species into 
which nonnatives could expand or be introduced.
    In the model, we analyzed the stream length as a measure of water 
availability. This provided a current condition of the amount of water 
in a stream at the driest time of year. This captured climate change 
and anthropogenic actions (surface water diversions and groundwater 
pumping) impacts to the stream. Wildfire is not analyzed in the model, 
but we did consider impacts from wildfire. Currently, wildfire could 
occur almost anywhere within the range of the DPS and impact one or 
more streams or entire AUs. However, impacts to the lower Colorado 
River basin roundtail chub DPS are dependent on the severity, location, 
and timing of the fire, as well as the size of the stream.
    Since roundtail chub developed as a result of multiple independent 
hybridization events over time (Rinne 1976; Rosenfeld and Wilkinson 
1989; DeMarais et al. 1992; Dowling and DeMarais 1993; Minckley and 
DeMarais 2000; Gerber et al. 2001; Schwemm 2006; Sch[ouml]nhuth et al. 
2014), it is important to maintain the DPS independently to preserve 
the unique genetic variation (Dowling et al. 2008, p. 2). The genetic 
diversity of the lower Colorado River basin roundtail chub DPS is 
within populations, meaning there is more similarity between 
populations across its range and connectivity among AUs may be more of 
an issue.
    There is a moderate to high level of uncertainty regarding the 
newly established populations of roundtail chub in the lower Colorado 
River basin. Of the four newly established populations of roundtail 
chub in the lower Colorado River basin, only one, Blue River, has 
demonstrated reproduction. This could be related to the size of the 
site, as Blue River is much larger than the other three sites, but this 
is not clear.
    The renovation effort in Fossil Creek for roundtail chub in the 
lower Colorado River basin (and headwater chub) has proven successful, 
but such an effort requires a large commitment of resources including 
funding and personnel.
III. Finding for Lower Colorado River Basin Roundtail Chub DPS
    Our review found that 15 AUs currently exist within the historical 
range of the lower Colorado River basin roundtail chub DPS across five 
drainage basins. To assess the current condition of these populations, 
we analyzed the impact from nonnative aquatic species, loss of water, 
and chub population structure. In addition, we considered wildfire, 
additional impacts from climate change, and demographic impacts from 
these factors, as well as reduction in range. We defined the minor risk 
category as a 0 to 5 percent current chance of extirpation, the low 
risk category as a 6 to 30 percent current

[[Page 60776]]

risk of extirpation, the moderate risk category as a 31 to 60 percent 
current risk of extirpation, and the high risk category as greater than 
60 percent current risk of extirpation. The model output resulted in 
one AU as minor risk, seven as low risk, six as moderate risk, and one 
as high risk.
    Eight AUs are projected as currently having minor or low risk of 
extirpation. This provides the resiliency (greater than 50 percent of 
the AUs are considered resilient enough to withstand stochastic 
events), redundancy (the AUs exist across the historical range, 
although some are small or have large nonnative aquatic species 
impacts, to withstand catastrophic events), and representation 
(multiple populations continuing to occur across the range of the DPS 
to maintain ecological and genetic diversity).
    We consider AUs within the minor to low risk categories to have 
sufficient resiliency at the present time. We consider these resilient 
because the risks from nonnative aquatic species and water 
availability, as well as wildfire, climate change, and genetics, are 
not having population-level effects to multiple AUs at this time. While 
the majority of streams occupied by chubs have nonnative aquatic 
species, there is little direct evidence of extirpation or significant 
population reductions of chubs from nonnative aquatic species 
currently; however, for Arizona and New Mexico native fish in general, 
this has been documented. Further, while the mechanism is unknown, 
currently there are several streams within multiple AUs containing 
chubs that have maintained populations in the presence of one or more 
of these nonnative aquatic species.
    While impacts from climate change are likely currently impacting 
chub populations at some scale, these do not appear to be having 
population-level impacts at this time. Climate model predictions 
suggest that climate will entail: An increase in the frequency and 
duration of droughts, alteration in the timing and amount of spring and 
fall flows due to changes in precipitation, and increased temperatures 
resulting in increased evaporation. All of these effects are likely to 
negatively affect chub populations. However, these projections are for 
midcentury (around 2046). The current and ongoing threats are not 
likely to impact all remaining populations significantly in the near 
term because these risks, such as climate change, move slowly across 
the landscape. Projected climate change impacts discussed in this 
proposed rule are at mid-century (~2046) and are likely to exacerbate 
water loss, reduction in hydrological connectivity, nonnative aquatic 
species, and species interactions (impacting demographics) is not 
projected until 2046.
    We consider the DPS to have sufficient redundancy and 
representation, and sufficiently large populations, that the DPS is 
able to withstand stochastic events. The AUs are currently spread over 
a large geographical area such that all the AUs are highly unlikely to 
experience a catastrophic event that would impacts all AUs now. 
Further, the current range of the DPS includes AUs that represent the 
known diversity of ecological settings and genetic materials for the 
roundtail chub in the lower Colorado River basin . The current and 
ongoing threats are not likely to impact all remaining populations 
significantly in the near term because these risks, such as climate 
change, move slowly across the landscape, and demographic impacts take 
time to impact a population. The increase or spread of nonnative 
aquatic species moves faster than climate change or demographics, but 
it will likely take a few years for a nonnative aquatic species to 
expand in a currently occupied stream or become established in a new 
stream. Wildfire is likely to have immediate impacts, but it is highly 
unlikely that wildfire will impact all AUs at the current time. As a 
result, it is unlikely that a single stochastic event (e.g., drought, 
wildfire) or catastrophic event will affect all known extant 
populations equally or simultaneously now; therefore, it would require 
several stochastic events or catastrophic events over a number of years 
to bring the roundtail chub in the lower Colorado River basin to the 
brink of extinction due to those factors.
    This estimate of the condition and distribution of populations 
provides sufficient resiliency, representation, and redundancy for the 
DPS. The primary threats to the DPS (nonnative aquatic species, water 
availability, and climate change) are not currently having population-
level effects to all AUs across the range of the lower Colorado River 
basin roundtail chub DPS. The threats are not currently impacting 
multiple populations across the DPS's range. Catastrophic or stochastic 
events in the present are not likely to have population-level impacts 
to multiple AUs. Consequently, the risk of extinction is sufficiently 
low that the DPS does not meet the definition of endangered under the 
Act. Based on the above information, we conclude that the lower 
Colorado River basin roundtail chub DPS does not meet the definition of 
an endangered species under the Act.
Threatened Species Throughout Range
    Having found that the lower Colorado River basin roundtail chub DPS 
is not endangered throughout its range, we next evaluated whether this 
DPS is threatened throughout its range.
I. Standard
    Under the Act, a threatened species is any species that is ``likely 
to become an endangered species within the foreseeable future 
throughout all or a significant portion of its range.'' The foreseeable 
future refers to the extent to which the Secretary can reasonably rely 
on predictions about the future in making determinations about the 
future conservation status of the species (U.S. Department of Interior, 
Solicitor's Memorandum, M-37021, January 16, 2009). A key statutory 
difference between an endangered species and a threatened species is 
the timing of when a species may be in danger of extinction, either now 
(endangered species) or in the foreseeable future (threatened species). 
The foreseeable future refers to the extent to which the Secretary can 
reasonably rely on predictions about the future in making 
determinations about the future conservation status of the species.
II. Foreseeable Future
    To assist us in evaluating the status of the species in the 
foreseeable future, we evaluated the risk factors that we found may 
have potential population-level effects over time. This included 
nonnative aquatic species, water availability, and conservation 
actions, which we assessed in our model. In addition, we considered the 
future risk from wildfire, water loss due to future anthropogenic 
actions, and demographic impacts from these risk factors, as well as 
reduction in range. In considering the foreseeable future, we 
forecasted the future status of the lower Colorado River basin 
roundtail chub DPS as described by the future condition of the AUs. 
This projected future condition was based on the risk factors and 
conservation actions affecting the DPS, and the uncertainties 
associated with these factors and actions. We consider 30 years from 
now a reasonable time to reliably predict the future conservation 
status of the DPS.
    The best available information indicates that we have a high level 
of certainty out to 30 years for climate change risks, which is an 
essential consideration for the foreseeable future. Therefore, our 
analysis of the status of the DPS to the foreseeable future uses a 
timeframe of 30 years. The outputs of Jaeger et al.'s (2014, entire) 
downscaled

[[Page 60777]]

climate forecasting models project climate scenarios to midcentury 
(approximately 2050) (IPCC 2014; Jaeger et al. 2014, entire). Jaeger et 
al. (2014, entire) focuses on the Verde River Basin in Arizona over 
current (1988-2006) and midcentury (2046-2064) time periods. This study 
was useful because the lower Colorado River basin roundtail chub DPS 
occurs in the Verde River Basin and the study focuses on impacts to 
native fish. Since the potential effects of climate change on flowing 
regions within streams and connectivity within and among streams, and 
the exacerbated impacts from nonnative aquatic species and demographics 
(i.e., age structure and genetics) due to climate change, were primary 
considerations in our status assessment, we considered climate change 
predictions essential in the foreseeable future. However, we did not 
extend our forecasting beyond the midcentury due to uncertainty in the 
climate change models and in the response of the DPS beyond 
approximately 2046.
III. Evaluation
    To assist us in evaluating the status of the DPS, we evaluated the 
risk factors that we found may have potential population-level effects 
over a 30-year time period. This included nonnative aquatic species, 
water availability, and conservation actions, which we assessed in our 
model. In addition, we considered the future risk from fire, additional 
climate change, future anthropogenic actions, and demographic effects 
from these risks factors, as well as reduction in range; however, these 
were not analyzed in the model. We evaluated impacts from these 
additional risks to each AU and the DPS as a whole.
    Chubs are affected not only by the quantity and quality of water, 
but also by the timing and spatial distribution of water. In the model, 
we analyzed the reduction in stream length as an impact from climate 
change. However, climate change models project that over the next 50 
years: (1) Future water levels and stream base flows are expected to 
continue to decrease in the Verde River in the lower Colorado River 
basin; (2) the frequency of stream drying events in the Verde Valley is 
expected to increase; (3) the length of the remaining flowing reaches 
of streams in the Verde Valley (or region) will be reduced; and (4) 
network-wide hydrologic connectivity for native fishes will be reduced 
(both over the course of the year and during spring spawning months). 
Climate change is also projected to alter the timing and amount of 
snowmelt and monsoon rains, and the frequency and duration of droughts. 
Climate change will also increase temperature, resulting in increased 
evaporation. Climate change is also likely to exacerbate water loss, 
reduction in hydrological connectivity, nonnatives, and species 
interactions (impacting demographics). All of these factors reduce the 
resiliency of AUs for the lower Colorado River basin roundtail chub 
DPS. However, the certainty of the model projections decreases as the 
projected timeframe increases. Further, the severity of climate change 
impacts depicted in climate models varies depending on the scenario 
being evaluated, with some projecting low changes (e.g., increased 
temperature and decreased rainfall) in carbon dioxide and others 
projecting high changes. To address this uncertainty, we considered 
different level of impacts to this DPS under various scenarios. Impacts 
from climate change are likely to affect all streams and AUs within the 
range of the lower Colorado River basin roundtail chub DPS over the 
next 30 years.
    In the model, we analyzed the stream length as a measure of water 
availability. This provided a current condition of the amount of water 
in a stream at the driest time of year. This captured climate change 
and anthropogenic action (surface water diversions and groundwater 
pumping) impacts to the stream. Wildfire is not analyzed in the model, 
but we did consider impacts from wildfire. Currently, wildfire could 
occur almost anywhere within the range of the DPS and impact one or 
more streams or entire AUs. However, impacts to the lower Colorado 
River basin roundtail chub DPS are dependent on the severity, location, 
and timing of the fire, as well as the size of the stream.
    As part of the foreseeable future, we also considered the likely 
reduction in water availability as a result of increased human demand 
for water, resulting in increased surface water diversions and 
groundwater pumping. Demand for water is highly likely to increase as 
human populations are predicted to increase, affecting the timing, 
amount, and distribution of water within streams. However, population 
growth, and the exact location of that population growth, is uncertain. 
Further, the timing and amount of water consumed is uncertain. To 
address this uncertainty, we considered different levels of impacts to 
a subset of streams or AUs.
    Nonnative aquatic species occupy almost all currently occupied chub 
streams, and we analyzed impacts to these streams and AUs through the 
model. Nonnative aquatic species and chubs have coexisted for some time 
in several of these streams, but the reasons for this are unclear. We 
expect that nonnative aquatic species will continue to persist in most 
if not all of the streams they currently occupy and that nonnative 
impacts will increase in a percentage of streams across the range of 
the DPS. In addition, there are three streams occupied by the lower 
Colorado River basin roundtail chub DPS that are currently free of 
nonnative aquatic species into which nonnatives could expand or be 
introduced.
    The projected effects to chubs from nonnative aquatic species are 
likely to be exacerbated by climate change, but this was not analyzed 
in the model. However, we do consider this in our analysis. As the 
available watered segments decrease, the interactions between nonnative 
aquatic species and chubs increase, with more larvae and young-of-the-
year removed from the chub populations dues to predation by nonnative 
aquatic species. In addition, resources become more limited, and the 
competition for these resources increases. Further, the reduction in 
water will likely decrease the water quality (e.g., decreased dissolved 
oxygen, temperature increases, changes in pH, and nutrient loading), 
which nonnative aquatic species are likely more capable of adapting to 
than chubs.
    Since the lower Colorado River basin roundtail chub DPS developed 
as a result of multiple independent hybridization events over time 
(Rinne 1976; Rosenfeld and Wilkinson 1989; DeMarais et al. 1992; 
Dowling and DeMarais 1993; Minckley and DeMarais 2000; Gerber et al. 
2001; Schwemm 2006; Sch[ouml]nhuth et al. 2014), it is important to 
maintain the DPS independently to preserve the unique genetic variation 
(Dowling et al. 2008, p. 2). For the lower Colorado River basin 
roundtail chub DPS, the pattern of more similarity between populations 
across its range and connectivity among AUs may be more of an issue.
    We have a moderate to high level of uncertainty regarding the 
success of the establishment of new populations. Of the four newly 
established populations of roundtail chub in the lower Colorado River 
basin, only one (Blue River) has demonstrated reproduction. One 
potential factor is the size of the site; Blue River is much larger 
than the other three sites. The renovation effort in Fossil Creek has 
proven successful. However, such an effort requires a large commitment 
of resources including funding and personnel. While attempts at 
establishing new populations in the future are likely, the success of 
these

[[Page 60778]]

sites is uncertain. In addition, the availability of funds and 
personnel in renovating another site like Fossil Creek is uncertain. 
Future scenarios projected in our model include conservation actions 
(establishment of new populations and securing sites), and the 
uncertainty of success of these sites.
IV. Finding for Lower Colorado River Basin Roundtail Chub DPS
    We used the same categories to categorize the risk of extirpation 
in the foreseeable future (until 2046) as discussed above. We 
determined that scenarios 1 and 3 are most likely and therefore most 
useful in making our determination. The model output for scenario 1 
projected 17 AUs due to the high management option projects two newly 
established populations and two renovated sites. The projected risk of 
extirpation for the 17 AUs were: Three AUs in minor risk, seven in low 
risk, six in moderate risk, and one in high risk of extirpation. 
Scenario 3 projected: 16 AUs in 2046 due to the low management option 
only projecting one newly established population. The projected risk of 
extirpation for the 16 AUs were: Two AUs in minor risk, seven in low 
risk, six in moderate risk, and one in high risk of extirpation.
    We consider AUs within the minor to low risk categories to have 
sufficient resiliency in the future because they contain very few 
nonnative aquatic species, have long stream length, and have a high 
chub population structure. All these components increase the AUs' 
ability to withstand a stochastic event such as wildfire and weather, 
which are the other risks we considered in our assessment. However, in 
scenario 1, two of the three AUs in the minor risk category are newly 
established sites. In scenario 3, one of the two AUs in the minor risk 
category was a newly established site.
    Nonnative aquatic species occur in all but three streams that the 
lower Colorado River basin roundtail chub DPS occupies. While chubs 
coexist with nonnative aquatic species in several streams, this does 
not mean that nonnatives are not impacting chubs. Further, climate 
change is likely to exacerbate water loss, reduction in hydrological 
connectivity, nonnative aquatic species, and species interactions 
(impacting demographics), resulting in increased competition from and 
predation by nonnatives. Since climate change is likely to affect all 
streams to varying degrees, it is likely that impacts from nonnative 
aquatic species will increase in a portion of streams throughout the 
range of the lower Colorado River basin roundtail chub DPS. The level 
of increased impacts from nonnative aquatic species is dependent on the 
condition of the chubs and nonnatives in that AU, and the level of 
impacts from climate change.
    The occurrence of wildfire within the range of the lower Colorado 
River basin roundtail chub DPS is highly likely. However, the severity, 
location, and impacts to chubs are uncertain. Over a 30-year period, 
multiple wildfires could impact multiple AUs. Impacts could range from 
loss of individuals to loss of streams to loss of AUs. Demand for water 
is highly likely to increase as human populations are predicted to 
increase, affecting the timing, amount, and distribution of water 
within streams. In addition, the synergistic impacts from the increased 
effects from wildfire, additional impacts from climate change, water 
loss due to anthropogenic actions, and demographic effects from these 
risks factors increase the likelihood and severity of stochastic 
impacts across the range of the DPS.
    This projected number of AUs in moderate and high risk (41 percent) 
existing across the DPS's range is not considered resilient enough to 
withstand stochastic events in the foreseeable future. These AUs have 
moderate to high nonnative aquatic species, low to moderate stream 
lengths, and low to moderate chub abundance. As stated above, the 
synergistic impacts from the increased impacts from wildfire, 
additional impacts from climate change, water loss due to anthropogenic 
actions, and demographic effects from these risks factors increase the 
likelihood and severity of stochastic impacts across the range of the 
DPS. This increase in likelihood and severity increases the risk of 
extirpation for these AUs in the moderate risk category. Over the 30-
year period of the foreseeable future, the risk from demographic 
(change in age structure and recruitment of populations) and 
environmental stochasticity (wildfire and weather) may have effects to 
AUs (or populations) in the moderate risk category. While there are 
seven AUs that ranked in the low risk category, three of these rank 
closely to the moderate risk category in scenarios 1 and 3. This leaves 
three AUs that we consider resilient enough to withstand future 
stochastic events under the most likely scenarios.
    In addition, the model projects that three (38 percent) AUs are 
isolated and only five (62 percent) AUs have some hydrologic 
connection. There are projected to be six streams approximately 5 km (3 
mi) or less in length. These streams are at a higher risk of 
extirpation due to stochastic and catastrophic events; the loss of 
these streams from an AU reduces the resiliency of that AU. Further, 
there is one AU approximately 5 km (3 mi) or less in length. This AU is 
at a higher risk of extirpation due to stochastic and catastrophic 
events. Roundtail chub in the lower Colorado River basin DPS are 
extirpated from several large riverine streams that provided 
connectivity across most of the historically occupied range. This has 
resulted in the recent isolation of AUs even within the same drainage 
basin. Nine AUs (about 60 percent) are isolated and are not able to 
naturally recolonize. If a catastrophic event such as wildfire or 
severe drought occurs within the range of these nine populations, they 
could be extirpated.
    The distribution of the AUs in the future could possibly be 
adequate to support representation and redundancy for the DPS, if a 
sufficient number of AUs were projected to be resilient. However, AUs 
that are not resilient cannot reliably contribute to redundancy or 
representation. Further, the redundancy and representation of the DPS 
is diminished based on the projected future condition of the AUs, and 
the potential impacts from wildfire, additional impacts from climate 
change, and water loss due to anthropogenic factors (e.g., surface 
water diversion and groundwater pumping), the demographic impacts from 
these factors, and the inability to rely on conservation measures. 
Redundancy is reduced because threats could potentially affect multiple 
AUs across the range of the lower Colorado River basin roundtail chub 
DPS over the next 30 years and several of these AUs are projected to 
have diminished resiliency. Consequently, the ability of the DPS to 
withstand catastrophic events is impaired.
    Historically, the lower Colorado River basin roundtail chub DPS had 
greater connectivity. Maintaining representation in the form of genetic 
or ecological diversity is important to keep the capacity of the chub 
to adapt to future environmental changes. The loss of an AU could 
result in reduced representation due to a loss of genetic diversity. 
Representation for the lower Colorado River basin roundtail chub DPS is 
projected to be reduced because of the further reduction in 
connectivity among streams.
    Because this estimate of the condition and distribution of 
populations in the foreseeable future would not provide sufficient 
resiliency, representation, and redundancy for the DPS, the risk of 
extinction is sufficiently high in the foreseeable future to meet the 
definition

[[Page 60779]]

of a threatened species under the Act. We conclude that the lower 
Colorado River basin roundtail chub DPS meets the definition of a 
threatened species under the Act.
Significant Portion of Its Range
    Under the Act and our implementing regulations, a species may 
warrant listing if it is endangered or threatened throughout all or a 
significant portion of its range. Because we have determined that lower 
Colorado River basin roundtail chub DPS is threatened throughout all of 
its range, no portion of its range can be ``significant'' for purposes 
of the definitions of ``endangered species'' and ``threatened 
species.'' See 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'' (79 FR 
37578; July 1, 2014).

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.
    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 ownership or establish a refuge, wilderness, reserve, preserve, or 
other conservation area. Such designation 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 consultation requirements of section 7(a)(2) 
of the Act would apply, but even in the event of a destruction or 
adverse modification finding, the obligation of the Federal action 
agency and the landowner is not to restore or recover the species, but 
to implement reasonable and prudent alternatives to avoid destruction 
or adverse modification of critical habitat.
    Under the first prong of the Act's definition of critical habitat, 
areas within the geographical area occupied by the species at the time 
it was listed are included in a critical habitat designation if they 
contain physical or biological features (1) which are essential to the 
conservation of the species and (2) which may require special 
management considerations or protection. For these areas, critical 
habitat designations identify, to the extent known using the best 
scientific and commercial data available, those physical or biological 
features that are essential to the conservation of the species (such as 
space, food, cover, and protected habitat). In identifying those 
physical and biological features within an area, we focus on the 
principal biological or physical constituent elements (primary 
constituent elements such as roost sites, nesting grounds, seasonal 
wetlands, water quality, tide, soil type) that are essential to the 
conservation of the species. Primary constituent elements are those 
specific elements of the physical or biological features that provide 
for a species' life-history processes and are essential to the 
conservation of the species.
    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. For example, an area currently occupied by the species but 
that was not occupied at the time of listing may be essential to the 
conservation of the species and may be included in the critical habitat 
designation. We designate critical habitat in areas outside the 
geographical area occupied by a species only when a designation limited 
to its range would be inadequate to ensure the conservation of the 
species.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific and commercial 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 developed during the listing process for the species. 
Additional information sources may include 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

[[Page 60780]]

or threatened species, and (3) section 9 of the Act's prohibitions on 
taking any individual of the species, including taking caused by 
actions that affect habitat. Federally funded or permitted projects 
affecting listed species outside their designated critical habitat 
areas may still result in jeopardy findings in some cases. These 
protections and conservation tools will continue to contribute to 
recovery of 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 designation of critical habitat is not prudent when one or both of 
the following situations exist:
    (1) The species is threatened by taking or other human activity, 
and identification of critical habitat can be expected to increase the 
degree of threat to the species, or
    (2) Such designation of critical habitat would not be beneficial to 
the species.
    There is currently no imminent threat of take attributed to 
collection or vandalism under Factor B for either the headwater chub or 
the lower Colorado River basin roundtail chub DPS, and identification 
and mapping of critical habitat is not expected to initiate any such 
threat. In the absence of finding that the designation of critical 
habitat would increase threats to a species, if there are any benefits 
to a critical habitat designation, then a prudent finding is warranted. 
Here, the potential benefits of designation include: (1) Triggering 
consultation under section 7 of the Act, in new areas for actions in 
which there may be a Federal nexus where it would not otherwise occur 
because, for example, it is or has become unoccupied or the occupancy 
is in question; (2) focusing conservation activities on the most 
essential features and areas; (3) providing educational benefits to 
State or county governments or private entities; and (4) preventing 
people from causing inadvertent harm to the species. Therefore, because 
we have determined that the designation of critical habitat will not 
likely increase the degree of threat to the species/DPS and may provide 
some measure of benefit, we find that designation of critical habitat 
is prudent for both the headwater chub and lower Colorado River basin 
roundtail chub DPS.

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 
headwater chub or lower Colorado River basin roundtail chub DPS 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) Information sufficient to perform required analyses of the 
impacts of the designation is lacking, or
    (ii) The biological needs of the species are not sufficiently well 
known to permit identification of an area as critical habitat.
    Delineation of critical habitat requires, within the geographical 
area occupied by the headwater chub or lower Colorado River basin 
roundtail chub DPS, identification of the physical or biological 
features essential to the conservation of the species. A careful 
analysis of the areas that may have the physical or biological features 
essential for the conservation of the species and that may require 
special management considerations or protections, and thus qualify for 
designation as critical habitat, will require a thorough assessment. 
Additionally, critical habitat can include specific areas outside the 
geographical area occupied by the species that are determined to be 
essential to its conservation. While we have some information on the 
habitat requirements of the species, the analysis of which of the 
specific features and areas meet the definition of critical habitat has 
not been completed. Since we have not determined which specific areas 
may meet the definition of critical habitat, the information sufficient 
to perform the required analysis of impacts of the critical habitat 
designation is lacking. Accordingly, we find designation of critical 
habitat to be ``not determinable'' at this time. When critical habitat 
is not determinable, the Act allows the Service an additional year to 
publish a proposed critical habitat designation (16 U.S.C. 
1533(b)(6)(C)(ii)).

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing results in public awareness, and 
conservation by Federal, State, Tribal, and local agencies, private 
organizations, and individuals. The Act encourages cooperation with the 
States and other countries and calls for recovery actions to be carried 
out for listed species. The protection required by Federal agencies and 
the prohibitions against certain activities are discussed, in part, 
below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Subsection 4(f) of the Act calls for the Service to develop 
and implement recovery plans for the conservation of endangered and 
threatened species. The recovery planning process involves the 
identification of actions that are necessary to halt or reverse the 
species' decline by addressing the threats to its survival and 
recovery. The goal of this process is to restore listed species to a 
point where they are secure, self-sustaining, and functioning 
components of their ecosystems.
    Recovery planning includes the development of a recovery outline 
shortly after a species is listed and preparation of a draft and final 
recovery plan. The recovery outline guides the immediate implementation 
of urgent recovery actions and describes the process to be used to 
develop a recovery plan. Revisions of the plan may be done to address 
continuing or new threats to the species, as new substantive 
information becomes available. The recovery plan also identifies 
recovery criteria for review of when a species may be ready for 
downlisting or delisting, and methods for monitoring recovery progress. 
Recovery plans also establish a framework for agencies to coordinate 
their recovery efforts and provide estimates of the cost of 
implementing recovery tasks. Recovery teams (composed of species 
experts, Federal and State agencies, nongovernmental organizations, and 
stakeholders) are often established to develop recovery plans. When 
completed, the recovery outline, draft recovery plan, and the final 
recovery plan will be available on our Web site (http://www.fws.gov/endangered), or from our Arizona Ecological Services Office (see FOR 
FURTHER INFORMATION CONTACT).
    Implementation of recovery actions generally requires the 
participation of a

[[Page 60781]]

broad range of partners, including other Federal agencies, States, 
Tribes, nongovernmental organizations, businesses, and private 
landowners. Examples of recovery actions include habitat restoration 
(e.g., restoration of native vegetation), research, captive propagation 
and reintroduction, and outreach and education. The recovery of many 
listed species cannot be accomplished solely on Federal lands because 
their range may occur primarily or solely on non-Federal lands. To 
achieve recovery of these species requires cooperative conservation 
efforts on private, State, and Tribal lands. If the headwater chub and 
the lower Colorado River basin roundtail chub DPS 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 Arizona and New Mexico would be eligible for Federal funds to 
implement management actions that promote the protection or recovery of 
the headwater chub and lower Colorado River basin roundtail chub DPS. 
Information on our grant programs that are available to aid species 
recovery can be found at: http://www.fws.gov/grants.
    Although the headwater chub and lower Colorado River basin 
roundtail chub DPS 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 this species. Additionally, we invite you to 
submit any new information on this species whenever it becomes 
available and any information you may have for recovery planning 
purposes (see FOR FURTHER INFORMATION CONTACT).
    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is proposed or listed as an 
endangered or threatened species and with respect to its critical 
habitat, if any is designated. Regulations implementing this 
interagency cooperation provision of the Act are codified at 50 CFR 
part 402. Section 7(a)(4) of the Act requires Federal agencies to 
confer with the Service on any action that is likely to jeopardize the 
continued existence of a species proposed for listing or result in 
destruction or adverse modification of proposed critical habitat. If a 
species is listed subsequently, section 7(a)(2) of the Act requires 
Federal agencies to ensure that activities they authorize, fund, or 
carry out are not likely to jeopardize the continued existence of the 
species or destroy or adversely modify its critical habitat. If a 
Federal action may affect a listed species or its critical habitat, the 
responsible Federal agency must enter into consultation with the 
Service.
    Federal agency actions within the species' habitat that may require 
conference or consultation or both as described in the preceding 
paragraph include land management and any other landscape-altering 
activities on Federal lands administered by the U.S. Forest Service, 
Bureau of Land Management, and National Park Service; issuance of 
section 404 Clean Water Act (33 U.S.C. 1251 et seq.) permits by the 
U.S. Army Corps of Engineers; Bureau of Reclamation activities; and 
construction and maintenance of roads or highways by the Federal 
Highway Administration.
    Under section 4(d) of the Act, the Service has discretion to issue 
regulations that we find necessary and advisable to provide for the 
conservation of threatened wildlife. We may also prohibit by regulation 
with respect to threatened wildlife any act prohibited by section 
9(a)(1) of the Act for endangered wildlife. For the headwater chub and 
lower Colorado River basin roundtail chub DPS, we are requesting 
information as to which prohibitions, and exceptions to those 
prohibitions, are necessary and advisable to provide for the 
conservation of the headwater chub or the lower Colorado River basin 
roundtail chub DPS pursuant to section 4(d) of the Act.
    We may issue permits to carry out otherwise prohibited activities 
involving threatened wildlife under certain circumstances. Regulations 
governing permits are codified at 50 CFR 17.32. With regard to 
threatened wildlife, a permit may be issued for the following purposes: 
For scientific purposes, for the enhancement of propagation or 
survival, for economic hardship, for zoological exhibition, for 
educational purposes, and for incidental take in connection with 
otherwise lawful activities. There are also certain statutory 
exemptions from the prohibitions, which are found in sections 9 and 10 
of the Act.
    It is our policy, as published in the Federal Register on July 1, 
1994 (59 FR 34272), to identify to the maximum extent practicable at 
the time a species is listed, those activities that would or would not 
constitute a violation of section 9 of the Act. The intent of this 
policy is to increase public awareness of the effect of a proposed 
listing on proposed and ongoing activities within the range of species 
proposed for listing. Based on the best available information, the 
following actions are unlikely to result in a violation of section 9, 
if these activities are carried out in accordance with existing 
regulations and permit requirements; this list is not comprehensive:
    (1) Normal agricultural and silvicultural practices, including 
herbicide and pesticide use, which are carried out in accordance with 
any existing regulations, permit and label requirements, and best 
management practices.
    (2) Recreational activities such as sightseeing, hiking, camping, 
and hunting in the vicinity of headwater chub or lower Colorado River 
basin roundtail chub DPS populations that do not destroy or 
significantly degrade their habitats, and do not result in take of 
headwater chub or roundtail chub.
    Based on the best available information, the following activities 
may potentially result in a violation of section 9 the Act; this list 
is not comprehensive:
    (1) Unauthorized collecting or handling of headwater chub or lower 
Colorado River basin roundtail chub DPS;
    (2) Use of piscicides, pesticides, or herbicides in violation of 
label restrictions;
    (3) Introduction of nonnative fish that compete with or prey upon 
headwater chub or lower Colorado River basin roundtail chub DPS;
    (4) Modification of the channel or water flow of any stream or 
removal or destruction of emergent aquatic vegetation in any body of 
water in which the headwater chub or lower Colorado River basin 
roundtail chub DPS is known to occur;
    (5) Destruction or alteration of riparian and adjoining uplands of 
waters supporting headwater chub or lower Colorado River basin 
roundtail chub DPS by timber harvest, poor livestock grazing practices, 
road development or maintenance, or other activities that result in the 
destruction or significant degradation of cover, channel stability, 
substrate composition, increased turbidity, or temperature that results 
in death of or injury to any life-history stage of headwater chub or 
lower Colorado River basin roundtail chub DPS through impairment of the 
species' essential breeding, foraging, sheltering, or other essential 
life functions; and
    (6) Release of biological control agents that attack any life stage 
of headwater chub or lower Colorado River basin roundtail chub DPS.
    Questions regarding whether specific activities would constitute a 
violation of section 9 of the Act should be directed to the Arizona 
Ecological Services

[[Page 60782]]

Office (see FOR FURTHER INFORMATION CONTACT).

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 the ADDRESSES section. 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.

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

    We have determined that environmental assessments and environmental 
impact statements, as defined under the authority of the National 
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), need not be 
prepared in connection with listing a species as an endangered or 
threatened species under the Endangered Species Act. We published a 
notice outlining our reasons for this determination in the Federal 
Register on October 25, 1983 (48 FR 49244).

Government-to-Government Relationship With Tribes

    In accordance with the President's memorandum of April 29, 1994 
(Government-to-Government Relations with Native American Tribal 
Governments; 59 FR 22951), Executive Order 13175 (Consultation and 
Coordination With Indian Tribal Governments), and the Department of the 
Interior's manual at 512 DM 2, we readily acknowledge our 
responsibility to communicate meaningfully with recognized Federal 
Tribes on a government-to-government basis. In accordance with 
Secretarial Order 3206 of June 5, 1997 (American Indian Tribal Rights, 
Federal-Tribal Trust Responsibilities, and the Endangered Species Act), 
we readily acknowledge our responsibilities to work directly with 
tribes in developing programs for healthy ecosystems, to acknowledge 
that tribal lands are not subject to the same controls as Federal 
public lands, to remain sensitive to Indian culture, and to make 
information available to tribes.
    We have determined that there are tribal lands that are occupied by 
headwater chub or lower Colorado River basin roundtail chub DPS. The 
lands owned by San Carlos Apache Tribe and White Mountain Apache Tribe 
contain the largest amount of occupied streams. We have begun 
government-to-government coordination with these tribes. We sent 
notification letters in July 2014 to each tribe informing them of our 
assessment of the species under section 4(b)(2) of the Act. We have 
engaged in conversations with both tribes about the status assessment. 
We met with the White Mountain Apache Tribe on September 24, 2014, 
which Chairman Lupe attended, and had a follow-up call with tribal 
representatives on October 23, 2014. We met with the Recreation and 
Wildlife Director of the San Carlos Apache Tribe on July 30, 2014. We 
also sent letters to the following tribes that may be affected by the 
proposed listing or future proposed critical habitat: Ak-Chin Indian 
Community, Chemehuevi Tribe, Colorado River Indian Tribes, Fort 
McDowell Yavapai Nation, Gila River Indian Community, Hopi Tribe, 
Hualapai Tribe, Navajo Nation, Pascua Yaqui Tribe, Salt River Pima-
Maricopa Indian Community, Tonto Apache Tribe, Yavapai Apache Nation, 
Yavapai-Prescott Indian Tribe, and Zuni Pueblo. We will continue 
coordinating with these tribes and any other interested tribes.

References Cited

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

Authors

    The primary authors of this proposed rule are the staff members of 
the Arizona Ecological Services Office.

List of Subjects in 50 CFR Part 17

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

Proposed Regulation Promulgation

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

PART 17--[AMENDED]

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 ``Chub, headwater'' and 
``Chub, roundtail'' in alphabetical order under FISHES to the List of 
Endangered and Threatened Wildlife in to read as follows:


Sec.  17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

 
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       Species                                              Vertebrate population
------------------------------------------------------   Historic range      where  endangered or       Status     When listed    Critical     Special
           Common name              Scientific name                               threatened                                      habitat       rules
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
                                                                      * * * * * * *
             Fishes
 
                                                                      * * * * * * *
Chub, headwater.................  Gila nigra.........  U.S.A. (AZ, NM)...  Entire.................  T              ...........           NA           NA
 
                                                                      * * * * * * *
Chub, roundtail.................  Gila robusta.......  U.S.A. (AZ, CO,     The Lower Colorado       T              ...........           NA           NA
                                                        NM).                River and its
                                                                            tributaries downstream
                                                                            of Glen Canyon Dam,
                                                                            including the Gila and
                                                                            Zuni River basins in
                                                                            New Mexico.

[[Page 60783]]

 
 
                                                                      * * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * *

    Dated: September 18, 2015.
Stephen Guertin,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. 2015-24900 Filed 10-6-15; 8:45 am]
 BILLING CODE 4310-55-P