Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Devils River Minnow, 41679-41701 [07-3678]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 146 (Tuesday, July 31, 2007)]
[Proposed Rules]
[Pages 41679-41701]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 07-3678]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AV25


Endangered and Threatened Wildlife and Plants; Designation of 
Critical Habitat for the Devils River Minnow

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 
designate critical habitat for the Devils River minnow (Dionda diaboli) 
under the Endangered Species Act of 1973, as amended (Act). In total, 
approximately 73.5 stream kilometers (km) (45.7 stream miles (mi)) are 
within the boundaries of the proposed critical habitat designation. The 
proposed critical habitat is located along streams in Val Verde and 
Kinney Counties, Texas.

DATES: We will accept comments from all interested parties until 
October 1, 2007. We must receive requests for public hearings, in 
writing, at the address shown in the ADDRESSES section by September 14, 
2007.

ADDRESSES: If you wish to comment on the proposed rule, you may submit 
your comments and materials by any one of several methods:
    1. You may mail or hand-deliver written comments and information to 
Adam Zerrenner, Field Supervisor, U.S. Fish and Wildlife Service, 
Austin Ecological Services Field Office, 10711 Burnet Road, Suite 200, 
Austin, TX 78758.
    2. You may send comments by electronic mail (e-mail) to fw2_
drm@fws.gov. Please see the Public Comments Solicited section below for 
file format and other information about electronic filing.
    3. You may fax your comments to the attention of Adam Zerrenner at 
512-490-0974.
    4. You may go to the Federal eRulemaking Portal: https://
www.regulations.gov. Follow the instructions for submitting comments.
    Comments and materials received, as well as supporting 
documentation used in the preparation of this proposed rule, will be 
available for public inspection, by appointment, during normal business 
hours at the Austin Ecological Services Field Office, 10711 Burnet 
Road, Suite 200, Austin, TX 78758; telephone 512-490-0057.

FOR FURTHER INFORMATION CONTACT: Adam Zerrenner, Field Supervisor, 
Austin Ecological Services Field Office, 10711 Burnet Road, Suite 200, 
Austin, TX 78758; telephone 512-490-0057; facsimile 512-490-0974. 
Persons who use a telecommunications device for the deaf (TDD) may call 
the Federal Information Relay Service (FIRS) at 800-877-8339, 7 days a 
week and 24 hours a day.

SUPPLEMENTARY INFORMATION:

Public Comments Solicited

    We intend that any final action resulting from this proposal will 
be as accurate and as effective as possible. Therefore, comments or 
suggestions from the public, other concerned governmental agencies, the 
scientific community, industry, or any other interested party 
concerning this proposed rule are hereby solicited. Comments 
particularly are sought concerning:
    (1) The reasons habitat should or should not be designated as 
critical habitat under section 4 of the Act (16 U.S.C. 1531 et seq.), 
including whether the benefit of designation would outweigh any threats 
to the species caused by designation such that the designation of 
critical habitat is prudent;
    (2) Specific information on the amount and distribution of Devils 
River minnow habitat, what areas should be included in the designation 
that were occupied at the time of listing that contain the features 
that are essential for the conservation of the species and why, and 
what areas that were not occupied at the listing are essential to the 
conservation of the species and why;
    (3) Information on the status of the Devils River minnow in 
Sycamore Creek and Las Moras Creek watersheds and information that 
indicates whether or not these areas should be considered essential to 
the conservation of the species;
    (4) Land use designations and current or planned activities in the 
subject areas and their possible impacts on proposed critical habitat;
    (5) Any foreseeable economic, national security, or other potential 
impacts resulting from the proposed designation and, in particular, any 
impacts on small entities and information about the benefits of 
including or excluding any areas that exhibit those impacts; and
    (6) Whether our approach to designating critical habitat could be 
improved or modified in any way to provide for greater public 
participation and understanding, or to assist us in accommodating 
public concerns and comments.
    You may submit comments and materials concerning this proposal by 
one of several methods (see ADDRESSES). Please include ``Attn: Devils 
River minnow'' in your e-mail subject header and your name and return 
address in the body of your message. If you do not receive a 
confirmation from the system that we have received your message, 
contact us directly by calling our Austin Ecological Services Field 
Office at 512-490-0057. Please note that comments must be received by 
the date specified in the DATES section in order to be considered and 
that the e-mail address fw2_drm@fws.gov will be closed out at the 
termination of the public comment period.
    Before including your address, phone number, e-mail address, or 
other personal identifying information in your comment, you should be 
aware that your entire comment--including your personal identifying 
information--may be made publicly available at any time. While you can 
ask us in your comment to withhold your personal identifying 
information from public review, we cannot guarantee that we will be 
able to do so.

Background

    It is our intent to discuss only those topics directly relevant to 
the designation of critical habitat in this proposed rule. For more 
information on

[[Page 41680]]

the Devils River minnow, refer to the final listing rule published in 
the Federal Register on October 20, 1999 (64 FR 56596) or the 2005 
Devils River Minnow Recovery Plan available online at https://
www.fws.gov/endangered/. More detailed information on Devils River 
minnow biology and ecology that is directly relevant to designation of 
critical habitat is discussed under the Primary Constituent Elements 
section below.

Description and Taxonomy

    The Devils River minnow (Dionda diaboli Hubbs and Brown) is a small 
fish first collected in 1951 (Hubbs and Brown 1956, p. 70). The Devils 
River minnow is recognized as a distinct species by the American 
Fisheries Society (Nelson et al. 2004, p. 70). Taxonomic validity is 
based on morphology (Hubbs and Brown 1956, p. 69), genetic markers 
(Mayden et al. 1992, p. 722), and chromosome differences (Gold et al. 
1992, p. 221).
    Adult Devils River minnows reach sizes of 25-53 millimeters (mm) 
(1.0-2.1 inches (in)) standard length. The fish has a wedge-shaped spot 
near the tail and a pronounced lateral stripe extending through the eye 
to the snout but without reaching the lower lip. The species has a 
narrow head and prominent dark markings on the scale pockets of the 
body above the lateral line, producing a crosshatched appearance when 
viewed from above (Hubbs and Brown 1956, pp. 69-70). The species occurs 
with other minnows, such as the closely related manantial roundnose 
minnow (Dionda argentosa).

Distribution and Habitat

    The Devils River minnow is limited to short stretches of spring-fed 
stream tributaries of the Rio Grande in southwestern Texas and 
northeastern Mexico (Garrett et al. 1992, p. 259). In the United 
States, the fish has never been found outside of five streams in Val 
Verde and Kinney Counties, Texas. The Devils River minnow currently 
occurs in stretches of the Devils River, San Felipe Creek, and Pinto 
Creek. It has been extirpated from Las Moras Creek and has not been 
collected from Sycamore Creek since 1989 (Garrett et al. 1992, pp. 261-
267; Garrett et al. 2004, p. 435). There is little information 
available on the status of the Devils River minnow in Mexico. 
Historically, it was known to occur in the R[iacute]o San Carlos and 
several streams in the R[iacute]o Salado Drainage, in the State of 
Coahuila. Regulations at 50 CFR 424.12(h) state that critical habitat 
shall not be designated within foreign countries or in other areas 
outside of United States jurisdiction. As such, geographical areas 
supporting the Devils River minnow in Mexico are not included in the 
proposed critical habitat designation.
    The Devils River minnow is found only in spring-fed streams (Brune 
1981, pp. 274-275, 450-454; Garrett et al. 1992, p. 259) with shallow 
to moderate depths and slow to moderate water velocity over gravel 
substrates. Within these streams, Devils River minnows are most often 
found within or nearby emergent aquatic plants (Garrett et al. 2004, p. 
437) or near similar structures created by stream bank vegetation that 
extends into the water (Lopez-Fernandez and Winemiller 2005, p. 249).

Previous Federal Actions

    The Devils River minnow was listed as threatened on October 20, 
1999 (64 FR 56596). Critical habitat was not designated for this 
species at the time of listing (64 FR 56606). On October 5, 2005, the 
Forest Guardians, Center for Biological Diversity, and Save Our Springs 
Alliance filed suit against the Service for failure to designate 
critical habitat for this species (Forest Guardians et al. v. Hall 
2005). On June 28, 2006, a settlement was reached that requires the 
Service to re-evaluate our original prudenct determination. The 
settlement stipulated that, if prudent, a proposed rule would be 
submitted to the Federal Register for publication on or before July 31, 
2007, and a final rule by July 31, 2008. This proposed rule complies 
with the settlement agreement and with section 4(b)(2) of the Act. For 
more information on previous Federal actions concerning the Devils 
River minnow, refer to the final listing rule published in the Federal 
Register on October 20, 1999 (64 FR 56598).

Critical Habitat

    Critical habitat is defined in section 3 of the Act as (i) the 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by a 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 any endangered species or threatened species to the point at 
which the measures provided pursuant to the Act are no longer 
necessary.
    Critical habitat receives protection under section 7(a)(2) of the 
Act through the prohibition against destruction or adverse modification 
of critical habitat with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 of the Act requires 
consultation on Federal actions that may affect 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 government or public 
access to private lands. Section 7(a)(2) of the Act is a purely 
protective measure and does not require implementation of restoration, 
recovery, or enhancement measures.
    To be included in a critical habitat designation, the habitat 
within the geographical area occupied by the species must first have 
features that are essential to the conservation of the species. 
Critical habitat designations identify, to the extent known using the 
best scientific data available, habitat areas that provide essential 
life cycle needs of the species (i.e., areas on which are found the 
primary constituent elements, as defined at 50 CFR 424.12(b)).
    Occupied habitat that contains the features essential to the 
conservation of the species meets the definition of critical habitat 
only if the essential features thereon may require special management 
considerations or protection. Thus, we do not include areas where 
existing management is sufficient to conserve the species. (As 
discussed below, such areas may also be excluded from critical habitat 
pursuant to section 4(b)(2) of the Act.) Unoccupied areas can be 
designated as critical habitat. However, when the best available 
scientific data do not demonstrate that the conservation needs of the 
species require additional areas, we will not designate critical 
habitat in areas outside the geographical area occupied by 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, the Service's Policy on Information Standards Under the 
Endangered Species Act, published in the Federal Register on July 1, 
1994 (59 FR 34271), and Section 515 of the Treasury and General 
Government Appropriations Act for Fiscal Year 2001 (P.L. 106-554; H.R. 
5658), and the associated Information Quality Guidelines issued by the 
Service, provide criteria, establish procedures, and provide guidance 
to ensure that

[[Page 41681]]

decisions made by the Service represent the best scientific data 
available. They require Service 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 determining which 
areas are critical habitat, a primary source of information is 
generally the listing package for the species. Additional information 
sources 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, or other 
unpublished materials and expert opinion or personal knowledge. All 
information is used in accordance with the provisions of Section 515 of 
the Treasury and General Government Appropriations Act for Fiscal Year 
2001 (P.L. 106-554; H.R. 5658) and the associated Information Quality 
Guidelines issued by the Service.
    Habitat is often dynamic, and species may move from one area to 
another over time. Furthermore, we recognize that designation of 
critical habitat may not include all of the habitat areas that may 
eventually be determined to be necessary for the recovery of the 
species. For these reasons, critical habitat designations do not signal 
that habitat outside the designation is unimportant or may not be 
required for recovery.
    Areas that support populations, but are outside the critical 
habitat designation, will continue to be subject to conservation 
actions implemented under section 7(a)(1) of the Act and to the 
regulatory protections afforded by the section 7(a)(2) jeopardy 
standard, as determined on the basis of the best available information 
at the time of the action. Federally funded or permitted projects 
affecting listed species outside their designated critical habitat 
areas may still result in jeopardy findings in some cases. 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, or 
other species conservation planning efforts if new information 
available to these planning efforts calls for a different outcome.

Methods

    As required by section 4(b) of the Act, we use the best scientific 
data available in determining areas occupied at the time of listing 
that contain the features essential to the conservation of the Devils 
River minnow, and areas unoccupied at the time of listing that are 
essential to the conservation of the Devils River minnow, or both. In 
designating critical habitat for the Devils River minnow, we reviewed 
the relevant information available, including peer-reviewed journal 
articles, unpublished reports, the Devils River Minnow Recovery Plan, 
the final listing rule, and unpublished materials (such as expert 
opinions). In February 2006, we sent information requests to a large 
number of experts and stakeholders (such as private landowners, Texas 
state government agencies, other Federal agencies, local governments, 
and nongovernmental organizations).
    We have also reviewed available information that pertains to the 
habitat requirements of this species. We used a wide variety of sources 
of information, such as material included in reports submitted during 
section 7 consultations; research published in peer-reviewed articles 
and presented in academic theses; research proposals and correspondence 
from technical experts; data and reports from other State and Federal 
agencies; unpublished data such as field notes and personal 
observations from field biologists; and regional Geographic Information 
System (GIS) coverages, including geodatabases provided by partner 
organizations, such as the City of Del Rio and The Nature Conservancy.
    We are proposing to designate critical habitat for the Devils River 
minnow in areas that were occupied at the time of listing, and that 
contain the physical and biological features essential to the 
conservation of the species arranged in the quantity and spatial 
characteristics necessary for conservation (see ``Criteria Used to 
Identify Critical Habitat'' section below). We are also proposing to 
designate critical habitat in areas unoccupied at the time of listing 
and determined to be essential to the conservation of the Devils River 
minnow.

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to propose as critical 
habitat, we consider those physical and biological features (primary 
constituent elements) that are essential to the conservation of the 
species, and within areas occupied by the species at the time of 
listing, that may require special management considerations and 
protection. These include, but are not limited to, space for individual 
and population growth and for normal behavior; food, water, air, light, 
minerals, or other nutritional or physiological requirements; cover or 
shelter; sites for breeding, reproduction, and rearing (or development) 
of offspring; and habitats that are protected from disturbance or are 
representative of the historic geographical and ecological 
distributions of a species.
    The specific physical and biological features essential to the 
conservation of the Devils River minnow, primary constituent elements 
(PCEs), are derived from the biological needs of the species as 
understood from studies of its biology and ecology, including but not 
limited to, Edwards et al. (2004), Garrett et al. (1992), Garrett et 
al. (2004), Gibson et al. (2004), Harrell (1978), Hubbs (2001), Hubbs 
and Garrett (1990), Lopez-Fernandez and Winemiller (2005), Valdes Cantu 
and Winemiller (1997), and Winemiller (2003).

Space for Individual and Population Growth, Normal Behavior, and Cover

    The Devils River minnow is a fish that occurs only in aquatic 
environments of small to mid-sized streams that are tributaries to the 
Rio Grande. The species spends its full life cycle within streams. The 
stream environment provides all of the space necessary to allow for 
individual and population growth, food, cover, and normal behaviors of 
the species. Quantitative studies of the specific micro-habitats used 
by any life stages of Devils River minnow in the wild have not been 
conducted. Studies of fish habitat within its range have found too few 
individuals of Devils River minnow to analyze specific habitat 
associations (Garrett et al. 1992, p. 266; Valdes Cantu and Winemiller 
1997, p. 268; Robertson and Winemiller 2003, p. 119). However, 
observational studies have been conducted throughout its limited range 
that qualitatively defined stream conditions where Devils River minnows 
have been collected.
    General habitat descriptions of areas where Devils River minnow 
have been found include the following: ``the area where spring runs 
enter the river'' (Hubbs and Garrett 1990, p. 448); ``channels of fast-
flowing water over gravel bottoms'' (Garrett et al. 1992, p. 259); 
``associated with water willow (Justicia americana) and other aquatic 
macrophytes over a gravel-cobble substrate'' (Garrett et al. 2004, p. 
437) (macrophytes are plants large enough to be seen without a 
microscope); and ``stream seeps'' at sites that ``had abundant riparian 
vegetation overhanging the banks'' (Lopez-Fernandez and Winemiller 
2005, p. 249). We based our determinations of the PCEs on the physical 
and biological features that have been measured in

[[Page 41682]]

streams where Devils River minnow occur.
    a. Water Depth and Velocity. Flowing water within streams is 
critical to provide living space for the Devils River minnow. All of 
the streams where the Devils River minnow is found are supported by 
springs that derive their discharge from underground aquifers, either 
the Edwards Aquifer or the Edwards-Trinity Aquifer (Brune 1981, pp. 
274-277, 449-456; Edwards et al. 2004, p. 256; Garrett et al. 1992, p. 
261; Garrett et al. 2004, p. 439; Hubbs and Garrett 1990, p. 448; 
Lopez-Fernandez and Winemiller 2005, p. 249). The Devils River minnow 
has been associated within the stream channel with areas with slow to 
moderate velocities between 10 and 40 centimeters (cm)/second (4 and 16 
inches (in)/second) (Winemiller 2003, p. 13). The Devils River minnow 
is usually found in areas with shallow to moderate water depths between 
about 10 cm (4 in) and 1.5 meters (4.9 feet (ft)) (Garrett et al. 2004, 
p. 436). Appropriate water depths and velocities are required physical 
features for Devils River minnows to complete all life history 
functions.
    b. Cover. The presence of vegetative structure appears to be 
particularly important for the Devils River minnow. Garrett et al. 
(2004, p. 437) states that the species is most often found associated 
with emergent or submerged vegetation. Lopez-Fernandez and Winemiller 
(2005, p. 249) also found the Devils River minnow associated with 
stream banks having riparian vegetation that overhangs into the water 
column, presumably providing similar structure for the fish to use as 
cover. The structure provided by vegetation likely serves as cover for 
predator avoidance by the Devils River minnow and as a source of food 
where algae and other microorganisms may be attached. In controlled 
experiments in an artificial stream setting, minnows in the Dionda 
genus (the experiment did not distinguished between the Devils River 
minnow and the closely related manantial roundnose minnow) were found 
consistently associated with plants, and, in the presence of a 
predator, sought shelter in plant substrate habitat (Thomas 2001, p. 
8). Also, laboratory observations by Gibson et al. (2004, p. 42) 
suggested that spawning only occurred when structure was provided in 
aquaria. Instream vegetative structure is an important biological 
feature for the Devils River minnow to avoid predation and complete 
other normal behaviors, such as feeding and spawning.
    c. Substrates. The Devils River minnow is most often associated 
with substrates (stream bottom) described as gravel and cobble (Garrett 
et al. 2004, p. 436). Lopez-Fernandez and Winemiller (2005, p. 248) 
found the Devils River minnow associated with areas where the amounts 
of fine sediment on stream bottoms were low (less than 65 percent 
stream bottom coverage) (Winemiller 2003, p. 13) and where there was 
low or moderate amounts of substrate embeddedness. The term 
embeddedness is defined by Sylte and Fischenich (2003, p. 1) as the 
degree to which fine sediments surround coarse substrates on the 
surface of a streambed. Low levels of substrate embeddedness and low 
amounts of fine sediment are physical stream features that provide 
interstitial spaces where microorganisms grow. These microorganisms are 
a component of the diet of the Devils River minnow (Lopez-Fernandez and 
Winemiller 2005, p. 250). We estimate substrate sizes for gravel-cobble 
between 2 and 10 cm (0.8 and 4 in) in diameter (Cummins 1962, p. 495) 
are important for supporting food sources for the Devils River minnow.
    d. Stream Channel. The Devils River minnow occurs in the waters of 
stream channels that flow out of the Edwards Plateau of Texas. The 
streams contain a variety of mesohabitats for fish that are temporally 
and spatially dynamic (Harrell 1978, p. 60-61; Robertson and Winemiller 
2003, p. 115). Mesohabitat types are stream conditions with different 
combinations of depth, velocity, and substrate, such as pools (stream 
reaches with low velocity and deep water), riffles (stream reaches with 
moderate velocity and shallow depths and some turbulence due to high 
gradient), runs (stream reaches with moderate depths and moderate 
velocities and a uniformly, flat stream bottom), and backwaters (areas 
in streams with little or no velocities along stream margins) 
(Parasiewicz 2001, p. 7). These physical conditions in stream channels 
are mainly formed by large flood events that shape the banks and alter 
stream beds. Healthy stream ecosystems require intact natural stream 
banks (composed of sediments, rocks, and native vegetation) and stream 
beds (dynamically fluctuating from silt, sand, gravel, cobble, and 
bedrock). These physical features allow natural ecological processes in 
stream ecosystems to maintain habitat for Devils River minnow behaviors 
of feeding, breeding, and seeking shelter.
    Devils River minnow may move up and downstream to use diverse 
mesohabitats during different seasons and life stages, which could 
partially explain the highly variable sampling results assessing 
abundance of the fish (Garrett et al. 2002, p. 478). However, it is 
unknown to what extent Devils River minnow may move within occupied 
stream segments because no research on movement has been conducted. 
Linear movement (upstream or downstream) within streams may be 
important to allow fishes to complete life history functions and adjust 
to resource abundance, but this linear movement may often be 
underestimated due to limited biological studies (Fausch et al. 2002, 
p. 490). The Devils River minnow occurs in relatively short stream 
segments and, therefore, needs to be able to move within the stream 
unimpeded to prevent population fragmentation.

Food

    The Devils River minnow, like other minnows in the Dionda genus, 
has a long coiled gut for digesting algae and plants. Lopez-Fernandez 
and Winemiller (2005, p. 250) noted that Devils River minnow graze on 
algae attached to stream substrates (such as gravel, rocks, submerged 
plants, woody debris) and associated microorganisms. Thomas (2001, p. 
13) observed minnows in the Dionda genus (the experiment did not 
distinguish between Devils River minnow and the closely related 
manatial roundnose minnow) feeding extensively on filamentous algae 
growing on rocks and plants in an artificial stream experiment. The 
specific components of the Devils River minnow diet have not been 
investigated, but a study is underway to identify stomach contents of 
the Devils River minnow in San Felipe Creek (Texas Parks and Wildlife 
Department (TPWD) 2006, p. 1). An abundant aquatic food base is an 
essential biological feature for conservation of Devils River minnow.

Water Quality

    The Devils River minnow occurs in spring-fed streams originating 
from groundwater. The aquifers that support these streams are of high 
quality, free of pollution and most human-caused impacts (Plateau Water 
Planning Group (PWPG) 2006, p. 5-9). This region of Texas has limited 
human development that would compromise water quality of the streams 
where Devils River minnows occur (San Felipe Creek may be an exception, 
see ``Special Management Considerations or Protection'' below). The 
watersheds are largely rural and have been altered to some extent by 
livestock grazing (cattle, sheep, and goats) for many decades (Brune 
1981, p. 449). As part of state-wide water planning efforts, the TPWD

[[Page 41683]]

proposed that all five streams within the range of the Devils River 
minnow (Devils River, San Felipe Creek, Sycamore Creek, Pinto Creek, 
and Las Moras Creek) be considered ``ecologically significant stream 
segments'' for their biological function, hydrological function, 
exceptional aquatic life, and high aesthetic value (El-Hage and Moulton 
2001, pp. 28-36, 45-49).
    No specific studies have been conducted to determine water quality 
preferences or tolerances for Devils River minnow. However, because the 
species now occurs in only three streams, observations of water quality 
conditions in these streams are used to evaluate the needed water 
quality parameters for critical habitat. In addition, laboratory 
studies by Gibson et al. (2004, pp. 44-46) and Gibson and Fries (2005, 
pp. 299-303) have also provided useful information for the water 
quality conditions in captivity for Devils River minnow.
    a. Water temperature. Water temperatures from groundwater discharge 
at these springs are considered constant (Hubbs 2001, p. 324). However, 
water temperatures downstream from springs vary daily and seasonally 
(Hubbs 2001, p. 324). Water temperatures have been measured in these 
stream segments to range from about 17 [deg]C (degrees Celsius) to 29 
[deg]C (63 [deg]F (degrees Fahrenheit) to 85 [deg]F). Temperatures in 
the Devils River ranged from 17 [deg]C to 27 [deg]C (63 [deg]F to 81 
[deg]F) (Lopez-Fernandez and Winemiller 2005, p. 248; Hubbs 2001, p. 
312). Measurements in San Felipe Creek have ranged from 19 [deg]C to 24 
[deg]C (66 [deg]F to 75 [deg]F) (Hubbs 2001, p. 311; Winemiller 2003, 
p. 13). Gibson and Fries (2005, p. 296) had successful spawning by 
Devils River minnows at temperatures from about 18 [deg]C to 24 [deg]C 
(64 [deg]F to 75 [deg]F). Higher water temperatures are rare in Devils 
River minnow habitat, but temperatures up to 29 [deg]C (84 [deg]F) were 
recorded in Pinto Creek (Garrett et al. 2004, p. 437). This stream 
segment has the lowest flow of those known to contain the Devils River 
minnow, resulting in higher temperatures. Maintaining water 
temperatures within an acceptable range in small streams is an 
essential physical feature for the Devils River minnow to allow for 
survival and reproduction.
    b. Water chemistry. Researchers have noted the need for high-
quality water in habitats supporting the Devils River minnow (Garrett 
2003, p. 155). Field studies at sites where Devils River minnow have 
been collected in conjunction with water quality measurements have 
documented that habitats contain the following water chemistry: 
dissolved oxygen levels are greater than 5.0 mg/l (milligrams per 
liter) (Hubbs 2001, p. 312; Winemiller 2003, p. 13; Gibson et al. 2004, 
p. 44); pH ranges between 7.0 and 8.2 (Garrett et al. 2004, p. 440; 
Hubbs 2001, p. 312; Winemiller 2003, p. 13); conductivity is less than 
0.7 mS/cm (microseimens per centimeter) and salinity is less than 1 ppt 
(part per thousand) (Hubbs 2001, p. 312; Winemiller 2003, p. 13; 
Garrett et al. 2004, p. 440; Gibson et al. 2004, p. 45); and ammonia 
levels are less than 0.4 mg/l (Hubbs 2001, p. 312; Garrett et al. 2004, 
p. 440). Streams with water chemistry within the observed ranges are 
essential physical features to provide habitat for normal behaviors of 
Devils River minnow.
    Garrett et al. (2004, pp. 439-440) highlighted the conservation 
implications of water quality when describing the distribution of 
Devils River minnow in Pinto Creek. The species is abundant in upstream 
portions of the creek and is abruptly absent at and downstream from the 
Highway 90 Bridge crossing. A different aquifer (Austin Chalk) feeds 
the lower portion of the creek (Ashworth and Stein 2005, p. 19), which 
results in changes in water quality (lower measurements of water 
temperature, pH, ammonia, and salinity). Garrett et al. (2004, p. 439) 
found that the change in water quality also coincided with the 
occurrence of different fish species that were more tolerant of lower 
values for these water quality parameters.
    c. Pollution. The Devils River minnow occurs only in habitats that 
are generally free of human-caused pollution. Garrett et al. (1992, pp. 
266-267) suspected that the addition of chlorine to Las Moras Creek for 
the maintenance of a recreational swimming pool may have played a role 
in the extirpation of Devils River minnow from that system. Unnatural 
addition of pollutants such as copper, arsenic, mercury, and cadmium; 
human and animal waste products; pesticides; suspended sediments; 
petroleum compounds and gasoline or diesel fuels will alter habitat 
functions and threaten the continued existence of Devils River minnow. 
Fish, particularly herbivores and bottom-feeders, such as the Devils 
River minnow, are susceptible to the detrimental effects of aquatic 
pollutants (Buzan 1997, p. 4). Areas with waters free of pollution are 
essential physical features to allow normal behaviors and growth of the 
Devils River minnow and to maintain healthy populations of its food 
sources.

Sites for Breeding, Reproduction, and Rearing of Offspring

    The specific sites and habitat associated with Devils River minnow 
breeding and reproduction have not been documented in the wild. 
However, Gibson et al. (2004) studied preferred conditions for spawning 
by Devils River minnow in a laboratory setting. Gibson et al. (2004, 
pp. 45-46) documented that the species is a broadcast spawner (they 
release eggs and sperm into the open water), over unprepared substrates 
(they don't build nests), and males display some territorial behavior. 
Broadcast spawning is the most common reproductive method in minnows 
(Johnston 1999, p. 22; Johnston and Page 1992, p. 604). Fertilized eggs 
of Devils River minnow were slightly adhesive (or became more adhesive 
with time) and tended to stick to gravels just below the surface of the 
substrate (Gibson et al. 2004, p. 46). The eggs can hatch less than one 
week after deposition (Gibson 2007, p. 1). There was little seasonality 
in spawning periods observed (Gibson et al. 2004, p. 45-46), which is 
consistent with a species that lives in a relatively stable temperature 
environment, such as spring-fed streams with low seasonal temperature 
variations. Based on this information, it is likely the species can 
spawn during most of the year. This is supported by Garrett et al. 
(2004, p. 437), who observed distinct breeding coloration of Devils 
River minnow (blue sheen on the head and yellow tint on body) in Pinto 
Creek in December 2001, and Winemiller (2003, p. 16), who found 
juveniles from early spring to late fall in San Felipe Creek.
    a. Substrate. Gibson and Fries (2005, p. 299) found that Devils 
River minnow preferred gravel for spawning substrate, with size ranging 
mostly from 2 to 3 cm in diameter (0.8 to 1.2 in). Gravel and rock 
substrates are required physical features for spawning (depositing, 
incubating, and hatching) of Devils River minnow eggs.
    b. Cover. In laboratory experiments, Devils River minnow spawned in 
tanks with live potted plants (Vallisnaria spp. and Justicia spp.); 
however, eggs were never found on the plants or other parts of the tank 
(Gibson et al. 2004, pp. 42, 43, 46). The plants apparently served as 
cover for the fish and allowed favorable conditions for spawning to 
occur. This condition is supported by observations in the wild that 
associate Devils River minnow with aquatic habitats where vegetative 
structure is present. This vegetative structure is a biological feature 
that is important for reproduction of Devils River minnow.

[[Page 41684]]

Habitat Protected From Disturbance or Representative of the Historic 
Geographical and Ecological Distribution of a Species

    a. Nonnative species. The introduction and spread of nonnative 
species have been identified as major factors in the continuing decline 
of native fishes throughout North America (Moyle et al. 1986, pp. 415-
416) and particularly in the southwestern United States (Miller 1961, 
p. 397; Miller 1977, pp. 376-377). Williams et al. (1989, p. 1) 
concluded that nonnative species were a causal factor in 68 percent of 
the fish extinctions in North America in the last 100 years. For 70 
percent of those fish still extant, but considered to be endangered or 
threatened, introduced nonnative species are a primary cause of the 
decline (Lassuy 1995, p. 392). Nonnative species have been referenced 
as a cause of decline in native Texas fishes as well (Anderson et al. 
1995, p. 319; Hubbs 1990, p. 89; Hubbs et al. 1991, p. 2).
    Aquatic nonnative species are introduced and spread into new areas 
through a variety of mechanisms, intentional and accidental, authorized 
and unauthorized. Mechanisms for nonnative fish dispersal in Texas 
include sport fish stocking (intentional and inadvertent, non-target 
species), aquaculture escapes, aquarium releases, and bait bucket 
releases (release of fish used as bait by anglers) (Howells 2001, p. 
1).
    Within the range of the Devils River minnow, nonnative aquatic 
species of potential concern include: armored (or suckermouth) catfish 
(Hypostomus sp.) in San Felipe Creek (Lopez-Fernandez and Winemiller 
2005, pp. 246-251); smallmouth bass (Micropterus dolomieu) in the 
Devils River (Thomas 2001, p. 1); African cichlid (Oreochromis aureus) 
in San Felipe Creek (Lopez-Fernandez and Winemiller 2005, p. 249) and 
Devils River (Garrett et al. 1992, p. 266); Asian snail (Melanoides 
tuberculata) and associated parasites (McDermott 2000, pp. 13-14); and 
Asian bivalve mollusk (Corbicula sp.) (Winemiller 2003, p. 25) in San 
Felipe Creek. Effects from nonnative species can include predation, 
competition for resources, altering of habitat, changing of fish 
assemblages (combinations of species), or transmission of harmful 
diseases or parasites (Aquatic Nuisance Species Task Force 1994, pp. 
51-59; Baxter et al. 2004, p. 2656; Howells 2001, pp. 17-18; Light and 
Marchetti 2007, pp. 442-444; Moyle et al. 1986, pp. 416-418). Studies 
have found effects from the armored catfish in San Felipe Creek, most 
likely due to competition for food (Lopez-Fernandez and Winemiller 
2005, p. 250). The persistence of Devils River minnow in its natural 
range of habitats is dependent on areas that are devoid of harmful 
nonnative aquatic species or where nonnative aquatic species are at 
levels that allow healthy populations of the Devils River minnow. The 
absence of harmful nonnative species is an essential biological feature 
for conservation of the Devils River minnow.
    b. Hydrology. Natural stream flow regimes (both quantity and 
timing) are vital components to maintain ecological integrity in stream 
ecosystems (Poff et al. 1997, p. 769; Resh et al. 1988, pp. 443-444). 
Aquatic organisms, like the Devils River minnow, have specific 
adaptations to use the environmental conditions provided by natural 
flowing systems and the highly variable stream flow patterns (Lytle and 
Poff 2004, p. 94). As with other streams in the arid southwestern 
United States, streams where the Devils River minnow occurs can have 
large fluctuations in stream flow levels. In Texas, streams are 
characterized by high variation between large flood flows and extended 
period of low flows (Jones 1991, p. 513). Base flows in streams 
containing Devils River minnow are generally maintained by constant 
spring flows (Ashworth and Stein 2005, p. 4), but in periods of 
drought, especially in combination with groundwater withdrawals, 
portions of stream segments can be periodically dewatered. The 
occurrence of intermittent stream segments within the range of the 
Devils River minnow is most common in Pinto Creek (Ashworth and Stein 
2005, Figure 13; Uliana 2005, p. 4; Allan 2006, p. 1).
    Although portions of stream segments included in this proposed 
designation may experience short periods of low or no flows (causing 
dry sections of stream), they are still important because the Devils 
River minnow is adapted to stream systems with some fluctuating water 
levels. Fish cannot persist in dewatered areas (Hubbs 1990, p. 89). 
However, Devils River minnows will use dewatered areas that are 
subsequently wetted as connective corridors between occupied or 
seasonally occupied habitat. Fausch et al. (2002, p. 490) notes in a 
review of movement of fishes related to metapopulation dynamics that, 
``Even small fishes may move long distances to repopulate rewetted 
habitats.'' Preventing habitat fragmentation of fish populations is 
important in reducing extinction risks in rare species (Fagan 2002, p. 
3255). Areas within stream courses that may be periodically dewatered 
but that serve as connective corridors between occupied or seasonally 
occupied habitat and through which the species may move when the 
habitat is wetted are important physical features of Devils River 
minnow habitat.
    Flooding is also a large part of the natural hydrology of streams 
within the range of Devils River minnow. Large floods have been shown 
to alter fish community structure and fish habitat use in the Devils 
River (Harrell 1978, p. 67) and in San Felipe Creek (Garrett and 
Edwards 2003, p. 787; Winemiller 2003, p. 12). Pearsons et al. (1992, 
p. 427) states that ``Flooding is one of the most important abiotic 
factors that structure biotic assemblages in streams.'' Floods provide 
flushing flows that remove fine sediments from gravel and provide 
spawning substrates for species like the Devils River minnow (Instream 
Flow Council 2002, p. 103; Poff et al. 1997, p. 775). Flooding is the 
physical mechanism that shapes stream channels by a process known as 
scour and fill, where some areas are scoured of fine sediments while 
fine sediments are redeposited in other areas (Gordon et al. 1992, pp. 
304-305; Poff et al. 1997, pp. 771-772). This dynamic process is 
fundamental to maintaining habitat diversity in streams that ensure 
healthy ecosystem function (Lytle and Poff 2004, pp. 96-99; Poff et al. 
1997, pp. 774-777). Allowing natural stream flows, particularly during 
flood events, is an essential physical feature to maintain stream 
habitats for Devils River minnow.

Primary Constituent Elements for the Devils River Minnow

    Under the Act and its implementing regulations, we are required to 
identify the physical and biological features (PCEs) within the 
geographical area occupied by the species, which may require special 
management considerations or protections.
    Based on the above needs and our current knowledge of the life 
history, biology, and ecology of the species, we have determined that 
the Devils River minnow's PCEs are:
    1. Streams characterized by:
    a. Areas with slow to moderate water velocities between 10 and 40 
cm/second (4 and 16 in/second) in shallow to moderate water depths 
between approximately 10 cm (4 in) and 1.5 m (4.9 ft), near vegetative 
structure, such as emergent or submerged vegetation or stream bank 
riparian vegetation that overhangs into the water column;
    b. Gravel and cobble substrates ranging in size between 2 and 10 cm 
(0.8 and 4 in) with low or moderate amounts of fine sediment (less than 
65

[[Page 41685]]

percent stream bottom coverage) and low or moderate amounts of 
substrate embeddedness; and
    c. Pool, riffle, run, and backwater components free of artificial 
instream structures that would prevent movement of fish upstream or 
downstream.
    2. High-quality water provided by permanent, natural flows from 
groundwater spring and seeps characterized by:
    a. Temperature ranging between 17 [deg]C and 29 [deg]C (63 [deg]F 
and 84 [deg]F);
    b. Dissolved oxygen levels greater than 5.0 mg/l;
    c. Neutral pH ranging between 7.0 and 8.2;
    d. Conductivity less than 0.7 mS/cm and salinity less than 1 ppt;
    e. Ammonia levels less than 0.4 mg/l; and
    f. No or minimal pollutant levels for copper, arsenic, mercury, and 
cadmium; human and animal waste products; pesticides; fertilizers; 
suspended sediments; petroleum compounds and gasoline or diesel fuels.
    3. Abundant aquatic food base consisting of algae attached to 
stream substrates and other associated microorganisms.
    4. Aquatic stream habitat either devoid of nonnative aquatic 
species (including fish, plants, and invertebrates) or in which such 
nonnative aquatic species are at levels that allow for healthy 
populations of Devils River minnows.
    5. Areas within stream courses that may be periodically dewatered 
for short time periods, during seasonal droughts, but otherwise serve 
as connective corridors between occupied or seasonally occupied areas 
through which the species moves when the area is wetted.
    This proposed designation is designed for the conservation of PCEs 
necessary to support the life history functions that were the basis for 
the proposal and the areas containing those PCEs. Because not all life 
history functions require all the PCEs, not all proposed critical 
habitat will contain all the PCEs.

Special Management Considerations or Protections

    When designating critical habitat, we assess whether the occupied 
areas contain the features essential to the conservation of the species 
that may require special management considerations or protections. We 
provide a summary discussion below of the special management needs for 
the stream segments we have identified as occupied at the time of 
listing (Devils River and San Felipe Creek) and the area considered to 
be essential for the conservation of the Devils River minnow (Pinto 
Creek). For additional information regarding the threats to the Devils 
River minnow and the needed management strategies to address those 
threats, see the Devils River Minnow Recovery Plan (Service 2005, pp. 
1.7-1--1.7-7; 1.8-1--1.8-4; 2.5-1--2.5-5).
    The following special management needs apply to all three stream 
segments, Devils River, San Felipe Creek, and Pinto Creek, and will be 
further discussed for each stream segment in the Proposed Critical 
Habitat Designation below.
    a. Groundwater management. The waters that produce all three stream 
segments issue from springs that are supported by underground aquifers, 
generally some portion of the Edwards Trinity Aquifer (Ashworth and 
Stein 2005, pp.16-33; Barker and Ardis 1996, pp. B5-B6; Brune 1981, pp. 
274-277, 449-456; Green et al. 2006, pp. 28-29; LBG-Guyton Associates 
2001, pp. 5-6; PWPG 2006, pp. 3-5, 3-6, 3-30). Regional groundwater 
flow in this area is generally from north to south (Ashworth and Stein 
2005, Figure 8). This aquifer is currently pumped to provide water for 
human uses including agricultural, municipal, and industrial (Ashworth 
and Stein 2005, p.1; Green et al. 2006, pp. 28-29; LBG-Guyton 
Associates 2001, pp. 22-27; PWPG 2006, pp. 3-14, 3-15). Some parts of 
this aquifer have already experienced large water level declines due to 
a combination of pumping withdrawals and regional drought (Barker and 
Ardis 1996, p. B50). There are a number of preliminary project plans to 
significantly increase the amount of groundwater pumped in this area to 
export it to other metropolitan centers (HDR Engineering Inc. 2001, p. 
1-1; Khorzad 2002, p. 19; PWPG 2006, pp. 4-54). If the aquifers are 
pumped beyond their ability to sustain levels that support spring 
flows, these streams will no longer provide habitat for the Devils 
River minnow (Ashworth and Stein 2005, p.34; Edwards et al. 2004, p. 
256; Garrett et al. 2004, pp. 439-440). Flow reductions can have 
indirect effects on fishes by impacting thermal regimes because higher 
water flow buffers against temperature oscillations (Hubbs 1990, p. 
89).
    Groundwater pumping that could affect stream flows within the 
Devils River minnow's range is subject to limited management control. 
State agencies do not control groundwater. Groundwater resources in 
Texas are under the ``Rule of Capture,'' and groundwater use is not 
regulated by any State agency (Holladay 2006, p. 2; Potter 2004, p. 9). 
The rule of capture essentially provides that groundwater is a 
privately owned resource and, absent malice or willful waste, 
landowners have the right to take all the water they can capture under 
their land without liability to neighboring landowners, even if in so 
doing they deprive their neighbors of the water's use (Holladay 2006, 
p. 2; Potter 2004, p. 1).
    Local groundwater conservation districts are the method for 
groundwater management in Texas (Caroom and Maxwell 2004, pp. 41-42; 
Holladay 2006, p. 3). Most districts are created by action of the Texas 
Legislature (Lesikar et al. 2002, p. 13). The regulations adopted by 
local groundwater conservation districts vary across the State and 
often reflect local decisions based on regional preferences, geologic 
limitations, and the needs of citizens (Holladay 2006, p. 3). The 
Kinney County Groundwater Conservation District is a local authority 
with some regulatory control over the pumping and use of groundwater 
resources in Kinney County (Brock and Sanger 2003, p. 42-44). 
Currently, there is no groundwater district in Val Verde County. It is 
not known whether groundwater districts, such as the one in Kinney 
County, will limit groundwater use and exportation to allow for 
conservation of surface water flows for environmental needs (Brock and 
Sanger 2003, p. 42-44; Caroom and Maxwell 2004, p. 47-48; Marbury and 
Kelly 2005, p. 9). The regional water plan for this area recognizes 
that groundwater needs to be managed for the benefit of spring flows 
(PWPG 2006, p. 3-30) and that groundwater use should be limited so that 
``base flows of rivers and streams are not significantly affected 
beyond a level that would be anticipated due to naturally occurring 
conditions'' (Ashworth and Stein 2005, p. 34; PWPG 2006, p. 3-8). 
Special management efforts are needed across the range of the Devils 
River minnow to ensure that aquifers are used in a manner that will 
sustain spring flows and provide water as an essential physical feature 
for the species.
    b. Nonnative species. Controlling existing nonnative species and 
preventing the release of new nonnative species are special management 
actions needed across the range of the Devils River minnow. The best 
tool for preventing new releases is education of the public on the 
problems associated with nonnative species (Aquatic Nuisance Species 
Task Force 1994, pp. 16-17). Current nonnative species issues have been 
cited for possible impacts to the Devils River (smallmouth bass) and 
San Felipe Creek (armored

[[Page 41686]]

catfish) (Lopez-Fernandez and Winemiller 2005, p. 247; Thomas 2001, p. 
1; Robertson and Winemiller 2001, p. 220). The armored catfish may 
already be impacting Devils River minnows in San Felipe Creek through 
competition for common food resources of attached algae and associated 
microorganisms (Lopez-Fernandez and Winemiller 2005, p. 250). Hoover et 
al. (2004, pp. 6-7) suggest that nonnative catfishes in the family 
Loricaridae, like armored catfish, will impact stream systems and 
native fishes by competing for food with other herbivores, changing 
plant communities, bank erosion due to burrowing in stream banks for 
spawning, and incidentally ingesting fish eggs. Problem nonnative 
species have not been documented in Pinto Creek. Please see the above 
discussion in ``Habitat Protected From Disturbance or Representative of 
the Historic Geographical and Ecological Distribution of a Species'' 
for additional discussion of nonnative species.
    c. Pollution. Special management actions are needed to prevent 
point and nonpoint sources of pollution entering in the stream systems 
where the Devils River minnow occurs. Devils River and Pinto Creek are 
generally free of threats from obvious sources of pollution. San Felipe 
Creek is in an urban environment where threats from human-caused 
pollution are substantial. Potential for spill or discharge of toxic 
materials is an inherent threat in urban environments. In addition, 
there are little to few current controls in the City of Del Rio to 
minimize the pollutants that will run off into the creek during 
rainfall events from streets, parking lots, roof tops, and maintained 
lawns from private yards and the golf course (Winemiller 2003, p. 27). 
All of these surfaces will contribute pollutants (for example, 
fertilizers, pesticides, herbicides, petroleum products) to the creek 
and potentially impact biological functions of the Devils River minnow. 
In addition, trash is often dumped into or near the creek and can be a 
source of pollutants. Special management by the City of Del Rio is 
needed (City of Del Rio 2006, p. 13) to institute best management 
practices for controlling pollution sources that enter the creek and 
maintain the water quality at a level necessary to support Devils River 
minnow.
    d. Stream channel alterations. The stream channels in the three 
streams where Devils River minnow occurs should be maintained in 
natural conditions, free of instream obstructions to fish movement and 
with intact stream banks of native vegetation. Devils River and Pinto 
Creek are generally free of stream channel alterations; however, San 
Felipe Creek has been altered by diversion dams, bridges, and armoring 
of stream banks (replacing native vegetation and soils with rock or 
concrete). Special management is needed in all three occupied streams 
to protect the integrity of the stream channels for the conservation of 
Devils River minnow habitat.

Criteria Used To Identify Critical Habitat

    We are proposing to designate critical habitat for the Devils River 
minnow in areas that were occupied at the time of listing and contain 
sufficient PCEs to support life history functions essential for the 
conservation of the species, which may require special management 
considerations or protection. Critical habitat is also being proposed 
for areas not considered occupied at the time of listing, but 
subsequently discovered to be occupied and essential for the 
conservation of the Devils River minnow.
    Critical habitat is designated based on sufficient PCEs being 
present to support the life processes of the species. Some areas 
contain all PCEs and support multiple life processes. Some areas 
contain only a portion of the PCEs necessary to support the particular 
use of that habitat.
    a. Range. We evaluated the geographical range of the Devils River 
minnow, as described in the Recovery Plan (Service 2005, p. 
1.4.1.1.4.5). There are five stream segments in the United States (all 
in Texas) that have ever been known to have been occupied by the Devils 
River minnow: (1) The Devils River (Val Verde County) from Beaver Lake 
downstream to near the confluence with the Rio Grande; (2) San Felipe 
Creek (Val Verde County) from the headsprings on the Lowe Ranch to 
downstream of the City of Del Rio; (3) Sycamore Creek (Val Verde/Kinney 
county boundary), only documented from the Highway 277 Bridge crossing; 
(4) Pinto Creek (Kinney County) from Pinto Springs downstream to 0.5 
stream km (0.3 stream mi) upstream of the Highway 90 Bridge crossing; 
and (5) Las Moras Creek (Kinney County), only documented from the Las 
Moras Spring in the City of Brackettville.
    Each of these five stream segments has (or formerly had) isolated 
populations of Devils River minnow separated by long distances, 
unsuitable habitat, and/or large dams that prevent fish movements. 
Although each of these streams is a tributary to the Rio Grande, we do 
not expect any contemporary exchange of individuals between these 
stream segments. The Devils River minnow is generally associated with 
upstream reaches of these streams, and connectivity would require 
movement through downstream reaches, through the Rio Grande, and back 
upstream through uninhabited reaches. The Devils River minnow has not 
been documented in the Rio Grande, or any other of its tributaries in 
the United States in modern times (Contreras-Balderas et al. 2002, pp. 
228-240; Edwards et al. 2002, p. 123; Garrett et al. 1992, pp. 261-265; 
Hoagstrom 2003, p. 95; Hubbs 1957, p. 93; Hubbs 1990, p. 90; Hubbs et 
al. 1991, p. 18; Trevi[ntilde]o-Robinson 1959, p. 255). These stream 
reaches are considered unsuitable habitat (Garrett et al. 1992, p. 261) 
because the aquatic habitat is very different (larger volume, higher 
suspended sediments, different suite of native fishes) than the streams 
where the Devils River minnow is found. The presence of Amistad 
Reservoir and Dam has further isolated the Devils River stream segment 
from the other stream segments. While some exchange of individuals 
could have occurred across a geologic time scale, any natural exchange 
of individual Devils River minnows between currently occupied stream 
segments in modern times is unlikely because of habitat changes in the 
Rio Grande, nonnative species, and potential instream barriers.
    Lack of access to private property can limit opportunities to 
sample for the presence of Devils River minnow (such as occurred on 
Pinto Creek, see Garrett et al. (2004), p. 436) and may limit our 
ability to accurately determine the full range of the species. However, 
we do not expect any additional streams outside of the geographical 
range of the species to be occupied. There could be additional stream 
segments within the known range that may be found to be occupied during 
future surveys, but the best available information at this time 
supports only these five stream segments known to be or to have been 
occupied by Devils River minnow in the United States.
    b. Occupancy. For the purpose of this critical habitat designation, 
we consider a stream segment to be occupied if Devils River minnow has 
been found to be present by species experts within the last 10 years, 
or where the stream segment is directly connected to a segment with 
documented occupancy within the last 10 years (see Proposed Critical 
Habitat Designation for additional occupancy information). The life 
expectancy of Devils River minnow is assumed to be about 3 years, 
although individuals have lived 5 years in captivity (Gibson 2006, p. 
1). Ten years is estimated to represent a time period that provides for 
at least three

[[Page 41687]]

generations and should allow for an adequate time to detect occupancy. 
Most stream segments have not been surveyed with a high degree of 
frequency, and this species can be difficult to detect, as even 
multiple samples within a short time in the same location by the same 
researcher can yield different results (Garrett et al. 2002, p. 478). 
We have assessed the occupancy of stream segments based on the best 
survey information available.
    c. Areas occupied at the time of listing. At the time the Devils 
River minnow was listed as a threatened species, it was only confirmed 
to occur at two sites on the Devils River (small tributaries) and in 
San Felipe Creek in Del Rio, Texas (64 FR 56597). This species is 
reasonably expected to move throughout connected stream reaches, based 
on past and recent collection records from these streams (Garrett et 
al. 2002, p. 478). Therefore, we determine there are two stream 
segments that were occupied at the time of listing: (1) Devils River 
from Pecan Springs to downstream of Dolan Falls (Garrett 2006a, p. 4; 
Garrett 2007, p. 1); and (2) San Felipe Creek from the Head Spring to 
downstream through the City of Del Rio (Garrett 2006b, p. 1; Garrett 
2007, p.1). The full extent of both stream segments is considered 
occupied, as surveys in the last 10 years have confirmed the species 
presence in the streams and the unit consists of contiguous habitat 
that allows fish movement throughout the stream.
    d. Primary constituent elements. We are proposing to designate the 
stream segments that were occupied at the time of listing and contain 
sufficient PCEs to support life history functions essential for the 
conservation of the species. Both of the stream segments occupied at 
the time of listing (Devils River and San Felipe Creek) contain 
sufficient PCEs to support life history functions essential for the 
conservation of the Devils River minnow.
    e. Areas not occupied at time of listing. Section 3(5)(A)(ii) of 
the Act allows for critical habitat to be designated in areas outside 
the geographical area occupied by the species at the time it is listed 
if those areas are essential for the conservation of the species. Three 
stream segments historically occupied by Devils River minnow but not 
considered occupied at the time of listing include Sycamore Creek, 
Pinto Creek, and Las Moras Creek.
    Sycamore Creek and Las Moras Creek are not currently occupied by 
the Devils River minnow. The last known occurrence of the species in 
these stream segments was 1989 for Sycamore Creek (Garrett et al. 1992, 
p. 265) and 1955 for Las Moras Creek (Garrett et al. 1992, p. 266; 
Hubbs and Brown 1956, pp. 70-71). Although recent publications continue 
to list Sycamore Creek as a stream where Devils River minnow may still 
occur (Garrett et al. 2004, p. 435; Lopez-Fernandez and Winemiller, p. 
247), we have a high degree of uncertainty as to the status of the fish 
in Sycamore Creek. Collections in 1999 and 2002 from the area of last 
known occurrence (in 1989) did not yield Devils River minnow (G. 
Garrett, TPWD, unpublished data 2002). In addition, Garrett et al. 
(1992) surveyed portions of Mud Creek (a tributary to Sycamore Creek) 
in 1989 but found no Devils River minnow. Additional surveys are needed 
to determine the current status of the fish in the Sycamore Creek 
watershed. Devils River minnow has not been collected from Las Moras 
Creek since the 1950s and is believed to be extirpated from the Las 
Moras Creek drainage. This conclusion is based on the absence of the 
species in sampling efforts from the late 1970s to 2002 (Smith and 
Miller 1986; Hubbs et al. 1991; Garrett et al. 1992; G. Garrett, 
unpublished data 2002).
    Restoring Devils River minnow to Sycamore Creek and Las Moras Creek 
may be important to achieve recovery goals for the species and optimize 
the chances of long-term species conservation (Service 2005, pp. 2.1-
1--2.2-3). Recovery criteria for Devils River minnow include having 
stable or increasing populations in both Sycamore Creek and Las Moras 
Creek, if reestablishment in Las Moras Creek is scientifically 
feasible. However, the feasibility of restoring populations in these 
areas is uncertain and the recovery plan advises additional assessment 
and landowner willingness will be necessary in both areas before 
restoration could occur. Therefore, based on the lack of information 
regarding the species status in Sycamore Creek, uncertainty of the 
potential for restoration in either stream segment, and the absence of 
data to demonstrate that the streams possess the PCEs, for the purposes 
of critical habitat designation, we have not included Sycamore Creek 
and Las Moras Creek in the proposed critical habitat designation.
    Due to the importance of these stream segments to the recovery of 
Devils River minnow, we solicit additional information and comments 
from interested parties on the distribution of Devils River minnow, 
specifically in the Sycamore Creek and Las Moras Creek watersheds. 
Information received, as well as supporting documentation will be used 
in the consideration of Sycamore Creek and Las Moras Creek's inclusion 
in the final critical habitat designation. We may consider including 
Sycamore Creek and Las Moras Creek in our critical habitat designation 
if we receive additional information during the public comment period 
that leads to a determination that these stream segments are essential 
to the conservation of Devils River minnow.
    At the time of listing in 1999, previous fish surveys in Pinto 
Creek were limited to the locations of public access at highway bridge 
crossings and did not find the species present (Garrett et al. 1992, p. 
260). In 2001, fish surveys in upstream areas of Pinto Creek discovered 
the previously unknown population of Devils River minnow (Garrett et 
al. 2004, p. 436-439). The species has been confirmed to occur from 
just