Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List a Distinct Population Segment of the Roundtail Chub in the Lower Colorado River Basin and To List the Headwater Chub as Endangered or Threatened With Critical Habitat, 26007-26017 [E6-6648]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 71, Number 85 (Wednesday, May 3, 2006)]
[Proposed Rules]
[Pages 26007-26017]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E6-6648]


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

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List a Distinct Population Segment of the Roundtail 
Chub in the Lower Colorado River Basin and To List the Headwater Chub 
as Endangered or Threatened With Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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

SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list a distinct population segment 
(DPS) of the roundtail chub (Gila robusta) in the lower Colorado River 
basin, and to list the headwater chub (G. nigra) as endangered or 
threatened under the Endangered Species Act of 1973, as amended (Act). 
The petition also asked the Service to designate critical habitat. 
After review of all available scientific and commercial information, we 
find that the petitioned action is not warranted for a DPS of the 
roundtail chub in the lower Colorado River basin, as explained below, 
but that listing is warranted for the headwater chub. Currently, 
however, listing of the headwater chub is precluded by higher priority 
actions to amend the Lists of Endangered and Threatened Wildlife and 
Plants. Upon publication of this 12-month petition finding, the 
headwater chub will be added to our candidate species list. We will 
develop a proposed rule to list the headwater chub as our priorities 
allow. Any determinations on critical habitat will be made during 
development of the proposed rule.

DATES: The finding announced in this document was made on April 27, 
2006.

ADDRESSES: The complete file for this finding is available for 
inspection, by appointment, during normal business hours at the Arizona 
Ecological Services Office, 2321 West Royal Palm Road, Suite 103, 
Phoenix, AZ 85021-4951. Please submit any new information, materials, 
comments, or questions

[[Page 26008]]

concerning this species or this finding to the above address.

FOR FURTHER INFORMATION CONTACT: Field Supervisor, Arizona Ecological 
Services Office, at the address above (602-242-0210).

SUPPLEMENTARY INFORMATION: 

Background

    Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.), requires 
that, for any petition to revise the List of Threatened and Endangered 
Species that contains substantial scientific and commercial information 
that listing may be warranted, we make a finding within 12 months of 
the date of receipt of the petition on whether the petitioned action is 
(a) not warranted, (b) warranted, or (c) warranted, but that the 
immediate proposal of a regulation implementing the petitioned action 
is precluded by other pending proposals to determine whether any 
species is threatened or endangered, and expeditious progress is being 
made to add or remove qualified species from the Lists of Endangered 
and Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act 
requires that a petition for which the requested action is found to be 
warranted but precluded be treated as though resubmitted on the date of 
such finding, i.e., requiring a subsequent finding to be made within 12 
months. Each subsequent 12-month finding will be published in the 
Federal Register.
    On April 14, 2003, we received a petition dated April 2, 2003, 
requesting that we list a distinct population segment (DPS) of the 
roundtail chub in the lower Colorado River basin as endangered or 
threatened, that we list the headwater chub as endangered or 
threatened, and that we designate critical habitat concurrently with 
the listing for both species. The petition, submitted by the Center for 
Biological Diversity (Center), was clearly identified as a petition for 
a listing rule, and it contained the names, signatures, and addresses 
of the requesting parties. Included in the petition was supporting 
information regarding the species' taxonomy and ecology, historical and 
current distribution, present status, and potential causes of decline. 
We acknowledged the receipt of the petition in a letter to Mr. Noah 
Greenwald, dated June 4, 2003. In that letter, we also advised the 
petitioners that, due to funding constraints in fiscal year 2003, we 
would not be able to begin processing the petition in a timely manner.
    On May 18, 2004, the Center sent a Notice of Intent to sue, 
contending that the Service had violated the Act by failing to make a 
timely 90-day finding on the petition to list a DPS of the roundtail 
chub in the lower Colorado River basin, and the headwater chub. On 
September 20, 2004, the Center filed a complaint against the Secretary 
of the Interior and the Service for failure to make a 90-day petition 
finding under section 4 of the Act. In a stipulated settlement 
agreement we agreed to submit a 90-day finding to the Federal Register 
by June 30, 2005 (Center for Biological Diversity v. Norton, CV-04-496-
TUC-CKJ (D. AZ)). The settlement agreement was approved by the District 
Court for the District of Arizona on May 5, 2005. On June 30, 2005, we 
made our 90-day finding that the petition presented substantial 
scientific information indicating that listing the roundtail chub as a 
DPS in the lower Colorado River basin, and the headwater chub 
throughout its range, may be warranted. The finding and our initiation 
of a status review was published in the Federal Register on July 12, 
2005 (70 FR 39981). We are required, pursuant to the court-approved 
stipulated settlement agreement, to make our 12-month finding pursuant 
to the Act (16 U.S.C. 1533(b)(3)(B)) on or before April 6, 2006. This 
notice constitutes our 12-month finding for the petition to list a DPS 
of the roundtail chub in the lower Colorado River basin, and to list 
the headwater chub, as endangered or threatened.

Biology

    The roundtail and headwater chubs are both cyprinid fish (members 
of Cyprinidae, the minnow family) with streamlined body shapes. Color 
in roundtail chub is usually olive-gray to silvery, with the belly 
lighter, and sometimes with dark blotches on the sides; headwater chub 
color is usually dark gray to brown overall, with silvery sides that 
often have faded lateral stripes. Roundtail chub are generally 25 to 35 
centimeters (cm) (9 to 14 inches (in)) in length, but can reach 50 cm 
(20 in). Headwater chub are quite similar in appearance to roundtail 
chub, although they are generally smaller, likely due to the smaller 
streams in which they occur (Minckley 1973; Sublette et al. 1990; 
Propst 1999; Minckley and Demaris 2000; Voeltz 2002).
    Baird and Girard (1852) first described roundtail chub from 
specimens collected from the Zuni River in northeastern Arizona and 
northwestern New Mexico. Headwater chub was first described from Ash 
Creek and the San Carlos River in east-central Arizona in 1874 (Cope 
and Yarrow 1875). Since the 1800s, both roundtail and headwater chub 
have been recognized as distinct entities, although at varying 
taxonomic levels (Miller 1945; Holden 1968; Rinne 1969; Holden and 
Stalnaker 1970; Rinne 1976; Smith et al. 1979; DeMarais 1986; Rosenfeld 
and Wilkinson 1989; DeMarais 1992; Dowling and DeMarais 1993; Douglas 
et al. 1998; Minckley and DeMarais 2000; Gerber et al. 2001). At 
present, both are recognized as distinct species, based on discrete 
occurrences of specific morphology (Minckley and DeMarais 2000). Both 
roundtail and headwater chub are recognized as species on the American 
Fisheries Society's most recent list of accepted common and scientific 
names of fishes (Nelson et al. 2004).

Roundtail Chub Distinct Population Segment

    In the petition to list these species, we were asked to consider 
designating a DPS for the roundtail chub in the lower Colorado River 
basin. Under the Act, we must consider for listing any species, 
subspecies, or, DPSs of vertebrate species/subspecies, if information 
is sufficient to indicate that such action may be warranted. To 
implement the measures prescribed by the Act and its Congressional 
guidance, we developed a joint policy with the National Oceanic and 
Atmospheric Administration (NOAA) Fisheries entitled Policy Regarding 
the Recognition of Distinct Vertebrate Population (DPS Policy) to 
clarify our interpretation of the phrase ``distinct population segment 
of any species of vertebrate fish or wildlife'' for the purposes of 
listing, delisting, and reclassifying species under the Act (61 FR 
4721; February 7, 1996). Under our DPS policy, we consider three 
elements in a decision regarding the status of a possible DPS as 
endangered or threatened under the Act. The elements are: (1) The 
population segment's discreteness from the remainder of the taxon to 
which it belongs; (2) the population segment's significance to the 
taxon to which it belongs; and (3) the population segment's 
conservation status in relation to the Act's standards for listing 
(i.e., when treated as if it were a species, is the population segment 
endangered or threatened?). Our policy further recognizes it may be 
appropriate to assign different classifications (i.e., threatened or 
endangered) to different DPSs of the same vertebrate taxon (61 FR 4721; 
February 7, 1996).

Discreteness

    The DPS policy's standard for discreteness requires an entity given 
DPS status under the Act to be

[[Page 26009]]

adequately defined and described in some way that distinguishes it from 
other populations of the species. The historical range of the roundtail 
chub included both the upper and lower Colorado River basins in the 
States of Wyoming, Utah, Colorado, New Mexico, Arizona, and likely 
Nevada and Baja California and Sonora, Mexico (Propst 1999; Bezzerides 
and Bestgen 2002; Voeltz 2002). In recent times, the upper and lower 
basin populations of the roundtail chub have been physically separated 
by the Glen Canyon Dam. Results from comparisons of genetic information 
of roundtail chubs between the lower and upper basins of the Colorado 
River were based on small sample sizes and provided inconclusive 
results (DeMarais 1992; Dowling and DeMarais 1993; Minckley and 
DeMarais 2000; Gerber et al. 2001). Therefore, the best available 
scientific data are not conclusive on the question of whether the lower 
basin populations of the roundtail chub are discrete from the upper 
basin populations. However, because we determine in the following 
section that the lower basin populations are not significant to the 
taxon as a whole, we need not address further the ``discreteness'' test 
of the DPS policy.

Significance

    Under our DPS policy, a population segment must be significant to 
the taxon to which it belongs. The evaluation of ``significance'' may 
address, but is not limited to, (1) Evidence of the persistence of the 
discrete population segment in an ecological setting that is unique for 
the taxon; (2) evidence that loss of the population segment would 
result in a significant gap in the range of the taxon; (3) evidence 
that the population segment represents the only surviving natural 
occurrence of a taxon that may be more abundant elsewhere as an 
introduced population outside its historic range; and (4) evidence that 
the discrete population segment differs markedly from other populations 
of the species in its genetic characteristics.
    Ecological Setting. Based on our review of the 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 are primarily found in the Tonto 
Transition and Painted Desert Sections of the Colorado Plateau Semi-
Desert Province in the Dry Domain, and the White Mountain-San Francisco 
Peaks-Mogollon Rim Section of the Arizona-New Mexico Mountains Semi-
Desert-Open Woodland-Coniferous Forest Province Dry Domain. Populations 
of roundtail chub in the upper basin are primarily found in the 
Northern Canyonlands and Uinta Basin Sections of the Intermountain 
Semi-Desert and Desert Province in the Dry Domain, and the Tavaputs 
Plateau and Utah High Plateaus and Mountains Sections of the Nevada-
Utah Mountains Semi-Desert-Coniferous Forest Province in the Dry Domain 
(McNabb and Avers 1994; Bailey 1995). These ecoregion differences 
result in differences in hydrograph, sediment, substrate, nutrient 
flow, cover, water chemistry, and other habitat variables of roundtail 
chub. Also, there are differences in type, timing, and amount of 
precipitation between the two basins, with the upper basin (3-65 
inches/year (Sims 1968)) somewhat less arid than the lower (5-25 
inches/year (Green and Sellers 1964)).
    The type and timing of precipitation, which are major factors in 
determining the pattern of streamflow, and which when plotted as the 
amount of runoff or discharge against time are known as a hydrograph 
(Dunne and Leopold 1978), also appear to be somewhat different between 
the two basins. The hydrograph of a stream is a major factor in 
determining habitat characteristics and their variability over space 
and time. Habitats of roundtail chub in the lower basin have a monsoon 
hydrograph or a mixed monsoon-snowmelt hydrograph. A monsoon hydrograph 
results from distinctly bimodal annual precipitation, which creates 
large, abrupt, and highly variable flow events in late summer and 
large, longer, and less variable flow events in the winter (Burkham 
1970; Sellers 1974; Minckley and Rinne 1991). Monsoon hydrographs are 
characterized by high variability, including rapid rise and fall of 
flow levels with flood peaks of one or more orders of magnitude greater 
than base, or ``normal low'' flow (Burkham 1970).
    In the upper basin, roundtail chub habitats have strong snowmelt 
hydrographs, with some summer/fall/winter precipitation, but with the 
majority of major flow events in spring and early summer (Bailey 1995; 
Carlson and Muth 1989; Miller and Hubert 1990). Snowmelt hydrographs 
are characterized by low variability, long, slow rises and falls in 
flow and peak flow events that are less than an order of magnitude 
greater than the base flow.
    The lower basin has lower stream flows and warmer temperatures in 
late spring and early summer; whereas this is typically the wettest 
period in the upper basin. Sediment loads vary substantially between 
streams in both basins, but are generally lesser in the upper basin 
than the lower (Carlson and Muth 1989), and patterning of sediment 
movement differs substantially because of the different hydrographs. In 
general, roundtail chub habitat in the lower Colorado River basin is of 
lower gradient, smaller average substrate size, higher water 
temperatures, higher salinity, smaller base flows, higher flood peaks, 
lesser channel stability and higher erosion, and substantially 
different hydrographs than the habitat in the upper Colorado River 
basin.
    Measurable hydrographic differences between the two basins are 
evident, as are differences in landscape level roundtail chub habitats 
between the upper and lower basins; these differences, however, do not 
appear to result in significant disparities in life history of 
roundtail chubs between the two basins. Roundtail chub in the upper and 
lower basins have basically the same life history and occupy similar 
in-stream habitats (Besserides and Bestgen 2002; Voeltz 2002). 
Furthermore, loss of the lower basin roundtail chub would not result in 
a loss of a form of the species that occurs in a setting unique from 
that found in the upper basin.
    Gap in the Range and Marked Differences in Genetic Characteristics. 
Roundtail chub in the lower Colorado River basin is at the southern 
portion of the historic and current distribution of the species. 
Although the species may have occurred in Mexico, there are no records 
to support this. Within the distribution of every species there exists 
a peripheral population, an isolate or subpopulation of a species at 
the edge of the taxon's range. Long-term geographic isolation and loss 
of gene flow between populations is the foundation of genetic changes 
in population resulting from natural selection or change. Evidence of 
changes in these populations may include genetic, behavioral, and/or 
morphological differences from populations in the rest of the species' 
range. While the available genetic information is sparse, it indicates 
that roundtail chubs sampled from Chevelon Creek in the Little Colorado 
River drainage of the lower Colorado River basin share the same mtDNA 
haplotype with upper basin roundtail chubs (Gerber et al. 2001; as 
discussed above under ``Discreteness''). Therefore, based on the 
genetic information currently available, roundtail chub in the lower 
Colorado River basin should not be considered biologically or 
ecologically significant based simply on genetic characteristics. We 
also considered

[[Page 26010]]

information regarding morphological and behavioral differences with 
regard to adaptations that may be occurring in the lower Colorado River 
basin roundtail chub and found no evidence of any differences. 
Biological and ecological significance under the DPS policy is always 
considered in light of Congressional guidance (see Senate Report 151, 
96th Congress, 1st Session) that the authority to list DPS's be used 
''sparingly'' while encouraging the conservation of genetic diversity.
    Whether the Population Represents the Only Surviving Natural 
Occurrence of the Taxon. 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 historic range. 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.

Conclusion

    Following a review of the available information, we conclude that 
the roundtail chub populations in the lower Colorado River basin are 
not significant to the remainder of the taxon. We made this 
determination based on the best available information, which does not 
demonstrate that (1) these populations persist in an ecological setting 
that is unique for the taxon; (2) the loss of these populations would 
result in a significant gap in the range of the taxon; and (3) these 
populations differ markedly from populations of roundtail chub in the 
upper basin in their genetic characteristics, or in other 
considerations that might demonstrate significance. Further, available 
information does not demonstrate that the life history and behavioral 
characteristics of roundtail chub in the lower basin are unique to the 
species. Therefore, on the basis of the best scientific and commercial 
information available, we find that proposing to list a DPS for the 
lower Colorado River basin populations of roundtail chub is not 
warranted; these populations do not meet our definition of a distinct 
population segment.

Headwater Chub

Distribution
    The historical distribution of headwater chub in the lower Colorado 
River basin is poorly documented, due to the paucity of early 
collections and the widespread anthropogenic (manmade) changes (i.e., 
habitat alteration and nonnative species introductions (Girmendonk and 
Young 1997)) to aquatic ecosystems beginning in the mid 19th century. 
The headwater chub was historically considered common throughout its 
range (Minckley 1973; Holden and Stalnaker 1975; Propst 1999). Voeltz 
(2002), estimating historical distribution based on museum collection 
records, agency database searches, literature searches, and discussion 
with biologists, found that headwater chub likely occurred in a number 
of tributaries of the Verde River, most of the Tonto Creek drainage, 
much of the San Carlos River drainage, and parts of the upper Gila 
River in New Mexico (Voeltz 2002). Voeltz (2002) estimated that 
headwater chub historically occupied approximately 500 km (312 mi) in 
Arizona and New Mexico. The species currently occurs in the same areas, 
but has a smaller distribution. In Arizona, four tributaries of the 
Verde River (Fossil Creek, the East Verde River, Wet Bottom Creek, and 
Deadman Creek), and Tonto Creek and eight of its tributaries (Buzzard 
Roost, Gordon, Gun, Haigler, Horton, Marsh, Rock, Spring, and Turkey 
Creeks), are currently occupied; and in New Mexico, in the upper East 
Fork, lower Middle Fork, and lower West Forks of the Gila River (Voeltz 
2002; S. Stefferud in litt. 2005) support headwater chub. Headwater 
chub may still occur in parts of the San Carlos River basin; however 
recent survey information for these streams is unavailable (Minckley 
and DeMarais 2000, Voeltz 2002).
    Headwater chub occur in the middle to upper reaches of moderately-
sized streams (Minckley and Demaris 2000). Bestgen and Propst (1989) 
examined status and life history in the Gila River drainage in New 
Mexico and found that headwater chubs occupied tributary and mainstem 
habitats in the upper Gila River at elevations of 1,325 meters (m) 
(4,347 feet (ft)) to 2,000 m (6,562 ft). Maximum water temperatures of 
headwater chub habitat varied between 20 to 27 [deg]C, and minimum 
water temperatures were around 7 [deg]C (Bestgen and Propst 1989; 
Barrett and Maughan 1995). Typical adult microhabitat consists of 
nearshore pools adjacent to swifter riffles and runs over sand and 
gravel substrate, with young of the year and juvenile headwater chub 
using smaller pools and areas with undercut banks and low current 
(Anderson and Turner 1978; Bestgen and Propst 1989). Spawning in Fossil 
Creek occurred in spring and was observed in March in pool-riffle areas 
with sandy-rocky substrates (Neve 1976). Neve (1976) reported that the 
diet of headwater chub included aquatic insects, ostracods (small 
crustaceans), and plant material.

Previous Federal Actions

    We placed the roundtail chub (as G. r. grahami, which then included 
headwater chub) on the list of candidate species as a category 2 
species on December 30, 1982 (47 FR 58454) and on January 6, 1989 (54 
FR 554). Category 2 species were those for which existing information 
indicated that listing was possibly appropriate, but for which 
substantial supporting biological data were lacking. On November 21, 
1991 (56 FR 58804), we continued to list headwater chub (now referred 
to as G. robusta, which included headwater and roundtail chub) as a 
category 2 species. Due to lack of funding to gather existing 
information on these fishes, they remained in category 2 through the 
1994 (59 FR 58982; November 15, 1994) Candidate Notices of Review. In 
the 1996 Candidate Notice of Review (61 FR 7596; February 28, 1996), 
category 2 was eliminated, and roundtail and headwater chub were no 
longer recognized as candidates for listing. Following receipt of the 
2002 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 roundtail and headwater chubs may be 
warranted. In order to ensure we had the best scientific and commercial 
information available to determine whether listing of these species was 
indeed warranted, we opened a 60-day public comment period, ending 
September 12, 2005, and commenced a status review.

Status of the Headwater Chub

    Headwater chub (as G. robusta grahami) was considered a threatened 
species by the American Fisheries Society on its list of fishes 
receiving legal protection and of special concern in 1987 (Johnson 
1987). Since that time, declines of the headwater chub have been 
further noted both in the scientific peer reviewed literature (Bestgen 
and Propst 1989) and in State agency reports (Girmendonk and Young 
1997; Brouder et al. 2000; Bezzerides and Bestgen 2002; Voeltz 2002).
    The most comprehensive and recent of the status reports concerning 
headwater chub was completed by the Arizona Game and Fish Department in 
2002, and peer-reviewed by Federal agency personnel, university 
researchers, and experts on the headwater chub (AGFD; Voeltz 2002).

[[Page 26011]]

Stream-specific distribution and status information for roundtail and 
headwater chub populations in the lower Colorado River basin was 
gathered from published literature; unpublished agency reports, 
records, manuscripts, and files; scientific collecting permit reports; 
personal communications with knowledgeable biologists; and academic 
databases. Based on this comprehensive information on all available 
current and historical survey records, AGFD estimated historical and 
current ranges of the headwater chub and found that the species had 
declined significantly from historical levels. The AGFD report also 
used a classification system, as described below in Table 1, to report 
status and threat information, which defined populations based on the 
abundance and recruitment of the population and presence or absence of 
obvious threats.

 Table 1.--Definitions of Status Description Categories Used To Describe
                the Status of Headwater Chub Populations
                           [From Voeltz 2002]
------------------------------------------------------------------------
              Status                             Definition
------------------------------------------------------------------------
Stable-Secure.....................  Chubs are abundant or common, data
                                     over the past 5-10 years shows a
                                     stable, reproducing population with
                                     successful recruitment; no impacts
                                     from nonnative aquatic species
                                     exist; and no current or future
                                     habitat altering land or water uses
                                     were identified.
Stable-Threatened.................  Chubs are abundant or common, data
                                     over the past 5-10 years shows a
                                     reproducing population, although
                                     recruitment may be limited;
                                     predatory or competitive threats
                                     from nonnative aquatic species
                                     exist; and/or some current or
                                     future habitat altering land or
                                     water uses were identified.
Unstable-Threatened...............  Chubs are uncommon or rare with a
                                     limited distribution; data over the
                                     past 5-10 years shows a declining
                                     population with limited
                                     recruitment; predatory or
                                     competitive threats from nonnative
                                     aquatic species exist; and/or
                                     serious current or future habitat
                                     altering land or water uses were
                                     identified.
Extirpated........................  Chubs are no longer believed to
                                     occur in the system.
Unknown...........................  Lack of data precludes determination
                                     of status.
------------------------------------------------------------------------

    Voeltz (2002) reviewed the 19 currently known populations of 
headwater chub and found that one was stable-secure, six were stable-
threatened, six were unstable-threatened, three were extirpated, and 
three were unknown. Deadman Creek, the one population that Voeltz 
considered stable-secure, has since been invaded by nonnative green 
sunfish (Lepomis cyanella) (Voeltz, Arizona Game and Fish Department, 
pers. comm. 2003), and should now be considered stable-threatened. 
Headwater chub are known to occupy only 40 percent of their former 
range, and have an unknown distribution on another 10 percent of their 
former range. Based on the best available scientific information, the 
headwater chub occurs in 16 of 19 known populations, which now occur in 
fragmented and isolated stream segments and represent only 40 to 50 
percent of the species' former range (approximately 200 km (125 mi) of 
500 km (312 mi)) in Arizona and New Mexico (Voeltz 2002).
    Populations of headwater chub are found in four separate drainage 
basins that are isolated from one another (the Verde River, Tonto 
Creek, San Carlos River, and upper Gila River). Within these four 
basins, there is further fragmentation and isolation of some 
populations. We consider a particular basin to be at risk of 
extirpation if there are fewer than a minimum of two stable-secure 
populations because any single population can be eliminated by 
stochastic events or catastrophic disturbance, such as fire (see Meffe 
and Carroll 1994). According to information in Voeltz (2002), and 
survey information collected since that time (as described above), 
headwater chub cannot be considered secure in any drainage because 
there are no stable-secure populations in any drainage in which they 
occur.
    In summary, the data show that the status of headwater chub is poor 
and declining. It has been extirpated from approximately 50 percent of 
its historical range; all 16 known populations are experiencing threats 
(see ``Summary of Factors Affecting the Headwater Chub'' discussion and 
Table 2 below); and it is no longer considered secure in any part of 
its historical range (Voeltz 2002; Voeltz, Arizona Game and Fish 
Department, pers. comm. 2003). Although 6 of the 16 extant populations 
are considered ``stable'' based on abundance and evidence of 
recruitment, we believe all six of these populations have a high 
likelihood of becoming extirpated in the foreseeable future, primarily 
because at least one, and in most cases several, nonnative aquatic 
species that have been implicated in the decline of headwater chub are 
present in these streams (Voeltz 2002).

Summary of Factors Affecting the Headwater Chub

    Section 4 of the Act (16 U.S.C. 1533), and implementing regulations 
at 50 CFR 424, set forth procedures for adding species to the Federal 
List of Endangered and Threatened Species. Under section 4(a) of the 
Act, we may list a species on the basis of any of five factors, as 
follows: (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 man-made factors affecting its 
continued existence. In making this finding, information regarding the 
status of, and threats to, the headwater chub in relation to the five 
factors provided in section 4(a)(1) of the Act is discussed below and 
summarized in Table 2 below.

 Table 2.--Summary of Headwater Chub Status and Threats by Stream Reach
              [Voeltz 2002; Voetlz, AGFD, pers. comm. 2003]
------------------------------------------------------------------------
          Stream reach                Status             Threats
------------------------------------------------------------------------
Christopher Creek...............  E              Considered extirpated
                                                  by nonnative species.
Horton Creek....................  E              Considered extirpated
                                                  by nonnative species.
Rye Creek.......................  E              Considered extirpated
                                                  by nonnative species.

[[Page 26012]]

 
Deadman Creek...................  ST             Nonnatives, grazing,
                                                  recreation.
Buzzard Roost Creek.............  ST             Roads, channelization,
                                                  grazing, mining,
                                                  nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
Gordon Creek....................  ST             Roads, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Haigler Creek...................  ST             Roads, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Marsh Creek.....................  ST             Roads, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Rock Creek......................  ST             Roads, grazing, mining,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Spring Creek....................  ST             Roads, grazing, mining,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Ash Creek.......................  U              Roads, grazing,
                                                  nonnatives,
                                                  recreation, fire.
Wet Bottom Creek................  U              Roads, grazing,
                                                  nonnatives,
                                                  recreation, fire.
San Carlos River................  U              Roads, channelization,
                                                  grazing, nonnatives,
                                                  recreation, water use.
Upper Gila River................  UT             Roads, channelization,
                                                  development, grazing,
                                                  mining, nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
Gun Creek.......................  UT             Roads, channelization,
                                                  grazing, mining,
                                                  nonnatives,
                                                  recreation, logging,
                                                  fire.
Tonto Creek.....................  UT             Roads, channelization,
                                                  development, grazing,
                                                  mining, nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
East Verde River................  UT             Roads, channelization,
                                                  development, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
Fossil Creek....................  UT             Roads, channelization,
                                                  development, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
Webber Creek....................  UT             Roads, channelization,
                                                  development, grazing,
                                                  nonnatives,
                                                  recreation, logging,
                                                  water use, fire.
------------------------------------------------------------------------
E=extirpated; ST=stable, threatened; U=unknown; UT=unstable, threatened.

Factor A: The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    Within the historical range of the headwater chub, much of the 
stream habitat has been destroyed or degraded, and loss of this habitat 
continues today (Minckley 1973; Tellman et al. 1997; Propst 1999; 
Voeltz 2002). At certain locations, activities such as groundwater 
pumping, surface water diversions, impoundments, dams, channelization 
(straightening of the natural watercourse, typically for flood control 
purposes), improperly managed livestock grazing, wildfire, agriculture, 
mining, roads, logging, residential development, and recreation all 
contribute to riparian and cienega (wetland) habitat loss and 
degradation in Arizona and New Mexico (Minckley and Deacon 1991; 
Tellman et al. 1997; Propst 1999; Voeltz 2002). These activities and 
their effects on headwater chub are discussed in further detail below.
    Water withdrawal. Headwater chub has been eliminated from much of 
its historical range because many areas formerly occupied are now 
unsuitable due to dewatering (Miller 1961; Miller 1972; Minckley 1973; 
Deacon et al. 1979; Williams et al. 1987; Bestgen and Propst 1989; 
Girmendonk and Young 1997; Bezzerides and Bestgen 2002; Voeltz 2002). 
Habitat for these fishes is likely eliminated once surface flow drops 
below 0.3 cubic meters per second (10 cubic feet per second) because 
the stream lacks the depth and habitat features, such as deep pools, 
that the species requires (U.S. Fish and Wildlife Service 1989). The 
upper Gila River, in the vicinities of Cliff, Redrock, and Virden, New 
Mexico, has been entirely dewatered on occasion by diversions for 
agriculture (Bestgen 1985). In addition, the communities of Strawberry, 
Pine, and Payson, Arizona, are exploring means of securing municipal 
water from Fossil Creek, which could substantially reduce flows in that 
stream (Voeltz 2002; J. Nystedt, U.S. Fish and Wildlife Service, pers. 
comm. 2004). Groundwater pumping in Tonto Creek regularly eliminates 
surface flows during parts of the year (Abarca and Weedman 1993). 
Groundwater pumping in the East Verde River eliminates the flow in many 
parts of the stream, especially when interbasin water transfers from 
Blue Ridge Reservoir are not occurring (Girmendonk and Young 1997). 
Groundwater pumping in Webber Creek for municipal use, as well as at 
least one diversion for agricultural use, reduces flows in that stream 
(Voeltz 2002). Groundwater pumping and surface water withdrawal 
directly eliminate headwater chub habitat because they remove water. 
Obviously, without water, there is no fish habitat, but flowing water 
also helps to create the habitat diversity that headwater chub require. 
Lack of flow often results in only pool habitat remaining, which can 
concentrate headwater chub with nonnative species and increase 
predation pressure of nonnative fishes on headwater chub, which has 
been documented in Marsh Creek and the East Verde River (Voeltz 2002). 
Water withdrawal is a threat in at least 6 of the 16 extant populations 
of headwater chub (Bestgen and Propst 1989; Girmendonk and Young 1997; 
Propst 1999; Voeltz 2002).
    Livestock grazing. Poorly managed livestock grazing has been 
documented to negatively impact headwater chub habitat. Poor livestock-
grazing management is often cited as one of the most significant 
factors contributing to regional stream channel downcutting (the 
entrenchment of stream channels and creation of arroyos) in the late 
1800s; profound effects from this period occurred throughout the 
watershed of Tonto Creek, which contains 70 percent of all extant 
headwater chub populations, and these effects are still evident today 
and compounded by ongoing grazing (Croxen 1926; Ganda 1997). Poorly 
managed livestock grazing destabilizes stream channels and disturbs 
riparian ecosystem functions (Herefore 1992; Tellman et al. 1997). 
Poorly managed livestock grazing negatively affects headwater chub 
habitat through removal of riparian vegetation (Clary and Webster 1989; 
Clary and Medin 1990; Schulz and Leininger 1990; Armour et al. 1991; 
Fleishner 1994), which results in reduced bank stability, fewer pools, 
and higher water temperatures, creating habitats that are too extreme 
to support headwater chub (Meehan 1991; Kauffman and Krueger 1984; 
Swanson et al. 1982; Minckley and Rinne 1985; Fleishner 1994; Belsky et 
al. 1999). Poorly managed livestock grazing also

[[Page 26013]]

causes increased sediment in the stream channel, due to streambank 
trampling and riparian vegetation loss (Weltz and Wood 1986; Waters 
1995; Pearce et al. 1998). Livestock physically alter streambanks 
through trampling and shearing, leading to bank erosion (Platts and 
Nelson 1989; Trimble and Mendel 1995). In combination, loss of riparian 
vegetation and bank erosion alters channel morphology, including 
increased erosion and deposition, downcutting, and an increased width/
depth ratio, all of which lead to a loss of deep pool habitats required 
by the headwater chub, and loss of shallow side and backwater habitats 
used by larval chub (Trimble and Mendel 1995; Belsky et al. 1999).
    Poorly managed livestock grazing causes the structure and diversity 
of the fish community to shift due to changes in availability and 
suitability of habitat types (Rahel and Hubert 1991). This loss of 
aquatic habitat complexity reduces the diversity of habitat types 
available to fish communities (Gorman and Karr 1978). In the arid west, 
this loss of habitat complexity has been found to accelerate the 
displacement of native fish species by nonnatives (Minckley and Rinne 
1991; Baltz and Moyle 1993; Lawler et al. 1999). Livestock grazing also 
contributes significantly to the introduction and spread of nonnative 
aquatic species through the proliferation of ponded water in stock 
tanks (U.S. Fish and Wildlife Service 2001). The U.S. Forest Service 
found that livestock grazing ``may affect [headwater chub] and 
eventually trend the species toward federal listing'' on allotments on 
the Tonto National Forest (Biological Evaluation and Assessment for the 
Green Valley Complex, Tonto National Forest 2002). Though largely a 
past threat, Voeltz (2002) found that livestock grazing occurs in every 
drainage in which headwater chub occur.
    Stream channelization and irrigation. Sections of many Gila Basin 
rivers and streams have been and continue to be channelized for flood 
control, which disrupts natural channel dynamics and promotes the loss 
of riparian plant communities. Channelization changes the gradient of 
the stream above and below the channel. It increases streamflow in the 
channelized section, which results in increased rates of erosion of the 
stream and its tributaries, accompanied by gradual deposits of sediment 
in downstream reaches that increase the risk of flooding (Emerson 1971; 
Simpson et al. 1982). Channelization has affected headwater chub 
habitat by reducing its complexity, eliminating cover, reducing 
nutrient input, improving habitat for nonnative species, changing 
sediment transport, altering substrate size, and reducing the length of 
the stream (and therefore the amount of aquatic habitat available) 
(Gorman and Karr 1978; Simpson 1982; Schmetterling et al. 2001). 
Channelization occurs within at least 50 percent of extant populations 
(Voeltz 2002).
    Irrigation directly from streams reduces or eliminates water in 
existing fish habitat. Fish can be carried into irrigation ditches, 
where they may die following desiccation (drying). Irrigation dams 
prevent movement of fish between populations, resulting in genetic 
isolation within species; small populations are subject to genetic 
threats, such as inbreeding depression (reduced health due to elevated 
levels of inbreeding) and to genetic drift (a reduction in gene flow 
within the species that can increase the probability of unhealthy 
traits; Meffe and Carrol 1994). There are numerous surface water 
diversions in headwater chub habitats, including the upper Gila River, 
East Verde River, and Tonto Creek. Larger dams may also prevent 
movement of fish between populations, and dramatically alter the flow 
regime of streams through the impoundment of water behind and below 
(Ligon et al. 1995).
    Mining activities. Mining activities were more widespread 
historically and likely constituted a greater threat in the past; 
however, the continued mining of sand, gravel, iron, gold, copper, or 
other materials remains a potential threat to the habitat of headwater 
chub. The effects of mining activities on populations include adverse 
effects to water quality and lowered flow rates due to dewatering of 
nearby streams needed for mining operations (ADEQ 1993). Ongoing sand 
and gravel mining in Tonto Creek is eliminating headwater chub habitat 
(Abarca and Weedman 1993; Voeltz 2002). Sand and gravel mining removes 
riparian vegetation and destabilizes streambanks, which results in 
habitat loss for the headwater chub (Brown et al. 1998). Mining occurs 
within at least 6 of the 16 extant populations (Voeltz 2002).
    Roads and Logging. Roads have adversely affected headwater chub 
habitat by destroying riparian vegetation and by increasing surface 
runoff, sedimentation, and erosion (Burns 1971; Eaglin and Hubert 
1993). Roads require instream structures, such as culverts and bridges, 
that remove aquatic habitat and can act as barriers to fish movement 
(Barrett et al. 1992; Warren and Pardew 1998). All of these activities 
negatively impact headwater chub by lowering water quality and reducing 
the quality and quantity of pools, by filling pools with sediments, by 
reducing the quantity of large woody-debris necessary to form pools, 
and by imposing barriers to movement. The end result is deterioration 
of habitat for the headwater chub (Burns 1971; Eaglin and Hubert 1993). 
Roads are found within every drainage containing extant populations of 
headwater chub (Voeltz 2002).
    Vehicular use of roads in creek bottoms, as has been documented in 
Tonto Creek (Voeltz 2002), degrades headwater chub habitat and can 
result in headwater chub mortality. Such use inhibits riparian plant 
growth, breaks down banks, causes erosion and sedimentation, and 
increases turbidity in the stream, particularly where vehicles drive 
through the stream and immediately downstream of the vehicular 
activity. These effects result in wider and shallower stream channels 
(Meehan 1991). This causes progressive adjustments in other variables 
of hydraulic geometry and results in changes to the configuration of 
pools, runs, riffles, and backwaters; levels of fine sediments and 
substrate embeddedness; availability of instream cover; and other fish 
habitat factors in the vicinity of vehicle crossings (Rosgen 1994). 
Resultant changes to the stream channels alter the way in which flood 
flows interact with the stream channel and may exacerbate flood damage 
to banks, channel bottoms, and riparian vegetation. The breaking down 
of stream banks by vehicles reduces undercut banks and overhanging 
vegetation that chub use as cover. Fish fry and eggs could also be 
killed or injured if vehicles are driven through stream segments where 
these life stages occur. Vehicles driven rapidly through the stream 
could splash young fish or eggs onto the bank where they may desiccate. 
Larger fish are likely to swim away and avoid death or injury. Public 
vehicular use is also often associated with an elevated risk of human-
caused fire.
    Adverse effects of stream sedimentation to fish and fish habitat 
have been extensively documented (Murphy et al. 1981; Newcombe and 
MacDonald 1991; Barrett et al. 1992). Excessive sedimentation causes 
channel changes that are adverse to headwater chub habitat. These 
activities have direct impacts on headwater chub habitat because 
excessive sediment can fill backwaters and deep pools used by headwater 
chub, and sediment deposition in the main channel can cause a tendency 
toward stream braiding (e.g., the stream becomes wider, shallower, and 
has numerous

[[Page 26014]]

channels as opposed to one channel), which reduces adult chub habitat. 
Excessive sediment will smother invertebrates (Newcombe and MacDonald 
1991), thereby reducing chub food production and availability, and 
related turbidity reduces the chub's ability to see and capture food 
(Barrett et al. 1992).
    Although logging is a landuse in the watersheds of 13 of the 
remaining 16 streams known to contain headwater chub populations 
(Voeltz 2002), logging is largely a threat of the past, resulting from 
previous management practices no longer in place. The alteration of 
watersheds resulting from road-building and logging is deleterious to 
fish and other aquatic life forms (e.g., Burns 1971; Eaglin and Hubert 
1993). Roads and logging increase surface runoff, sedimentation, and 
mudslides, and destroy riparian vegetation (Lewis 1998; Jones et al. 
2000).
    Recreation. Recreation was noted as a land-use in all of the 
watersheds containing headwater chub (Voeltz 2002). The impacts of 
recreation are highly dependant on the type of activity, with 
activities such as birdwatching having little to no impact and 
activities such as off-road vehicle use potentially having severe 
impacts on aquatic habitats. Specific problems with recreation were 
noted in the Upper Gila River, and Tonto and Webber Creeks (Voeltz 
2002). For example, Voeltz (2002) noted that in-channel vehicular 
traffic was a threat to headwater chubs in Tonto Creek (also discussed 
above under Roads). Much of the current range of the headwater chub 
occurs on public lands administered by the U.S. Forest Service, and 
public use of these lands is high; such use creates an elevated risk of 
human-caused impacts such as off-road vehicle use.
    Development activities. Headwater chub habitat is also threatened 
increasingly from urban and suburban development (Tellman et al. 1997). 
Urban and suburban development affects headwater chub and its habitat 
in a number of ways, such as direct alteration of streambanks and 
floodplains from construction of buildings, gardens, pastures, and 
roads (Tellman et al. 1997), or as mentioned above, diversion of water, 
both from streams and connected groundwater (Glennon 1995). On a 
broader scale, urban and suburban development alters the watershed, 
which changes the hydrology, sediment regimes, and pollution input 
(Dunne and Leopold 1978; Horak 1989; Medina 1990; Reid 1993; Waters 
1995). In addition, it has been documented that the introduction of 
nonnative plants and animals, such as releases from home aquariums, 
that can adversely affect headwater chub become more likely as nearby 
human populations increase (Aquatic Nuisance Species Task Force 1994).
    Suburban and urban development have degraded and eliminated 
headwater chub habitat. The Phoenix metropolitan area, founded in part 
due to its proximity to the Salt and Gila Rivers, is a population 
center of 3.5 million people. Communities in the middle and upper Verde 
River watershed, such as the Prescott-Chino Valley, the Cottonwood-
Clarkdale-Camp Verde communities, Strawberry, Pine, and Payson, are all 
seeing rapid population growth. Many of these communities are near 
headwater chub populations, and 25 percent of known headwater chub 
populations occur in areas of urban and commercial development (Voeltz 
2002). On a broader scale, as of 2005, Arizona was listed as the second 
fastest in Statewide population growth in the nation, and Arizona is 
projected to grow by 109 percent by the year 2030 (U.S. Census Bureau 
2005).
    Human activities in the watershed have had substantial adverse 
impacts to headwater chub habitat. Watershed alteration is a cumulative 
result of many human uses, including timber harvest, livestock grazing, 
roads, recreation, channelization, and residential development. The 
combined effect of all of these actions results in a substantial loss 
and degradation of habitat (Burns 1971; Reid 1993). For example, in 
Williamson Valley Wash, human uses (e.g., recreational use of off-road 
vehicles) in the highly erodible upper watershed have resulted in 
increased erosion and high loads of sediment. In 1993, flooding in 
Williamson Valley Wash carried enough sediment that the isolated pool 
where Gila chub (Gila intermedia), a related species to the headwater 
chub, were previously collected became completely filled with sand and 
gravel (Weedman et al. 1996).

Factor B: Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    We do not believe that overutilization is a threat to headwater 
chub in Arizona because angler catch is considered light (J. Warnecke, 
Arizona Game and Fish Department, pers. comm. 2004). However, in the 
upper Gila River in New Mexico, there are reports of anglers 
purposefully discarding chub species, which may be having a negative 
effect on populations of headwater chub locally (Voeltz 2002).

Factor C: Disease or Predation

    Nonnative fish that prey on and/or compete with headwater chub are 
a serious and persistent threat to the continued existence of this 
species. Direct predation by nonnative fishes on, and competition of 
nonnative fishes with, the headwater chub has resulted in rangewide 
population declines and local extirpations (e.g., Christopher Creek, 
Rye Creek, and Horton Creek). Nonnative aquatic organisms negatively 
affect native fish through predation, aggression and harassment, 
resource competition, habitat alteration, aquatic community disruption, 
introduction of diseases and parasites, and hybridization (numerous 
citations; see U.S. Fish and Wildlife Service (2001)). Based on survey 
information, nonnative species occur in every known population of 
headwater chub (Voeltz 2002).
    Headwater chub evolved in a fish community with low species 
diversity and where few predators existed, and as a result developed 
few or no mechanisms to deal with predation (Carlson and Muth 1989). In 
its habitats, the headwater chub was probably the most predatory fish 
and experienced little or no competition. Nonnative fishes known from 
within the historical range of headwater chub in the Gila River basin 
include channel catfish (Ictalurus punctatus), flathead catfish 
(Pylodictis olivaris), red shiner (Cyprinella lutrensis), fathead 
minnow (Pimephales promelas), green sunfish (Lepomis cyanellus), 
largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus 
dolomieui), rainbow trout (Oncorynchus mykiss), western mosquitofish 
(Gambusia affinis), carp (Cyprinus carpo), warmouth (Lepomis gulosus), 
bluegill (Lepomis macrochiris), yellow bullhead (Ameiurus natalis), 
black bullhead (Ameiurus melas), and goldfish (Carassius auratus) 
(Arizona Game and Fish Department Heritage Data Management System, U.S. 
Fish and Wildlife Service 2001).
    The introduction and spread of nonnative species has long been 
identified as one of the major factors in the continuing decline of 
native fishes throughout North America and particularly in the 
southwest (Miller 1961; Lachner et al. 1970; Ono et al. 1983; Minckley 
and Deacon 1991; Carlson and Muth 1989; Cohen and Carlton 1995; Fuller 
et al. 1999). In the American southwest, Miller et al. (1989) concluded 
that introduced nonnatives were a causal factor in 68 percent of the 
fish extinctions in North America in the last 100 years. For 70 percent 
of those

[[Page 26015]]

fish still extant, but considered to be endangered or threatened, 
introduced nonnative species are a primary cause of the decline 
(Aquatic Nuisance Species Task Force 1994; Lassuy 1995). In Arizona, 
release or dispersal of new nonnative aquatic organisms is a continuing 
phenomenon (Rosen et al. 1995; U.S. Fish and Wildlife Service 2001). 
Introduction of nonnative species has also been consistently cited as a 
threat to the native fish fauna of the Colorado River, and is listed as 
a factor in the listing rules of nine other fish species with 
historical ranges that overlap with headwater chub (bonytail (Gila 
elegans) (45 FR 27710), humpback chub (Gila cypha) (32 FR 4001), Gila 
chub (67 FR 51948), Colorado pikeminnow (Ptychocheilus lucius) (32 FR 
4001), spikedace (Meda fulgida) and loach minnow (Tiaroga cobitis),( 51 
FR 23769), razorback sucker (Xyrauchen texanus) (56 FR 54957), desert 
pupfish (Cyprinodon macularius) (61 FR 10842), and Gila topminnow 
(Poecilopsis occidentalis) (32 FR 4001)). In the Gila River basin, 
introduction of nonnatives is considered a major factor in the decline 
of all native fish species (Minckley 1985; Williams et al. 1985; 
Minckley and Deacon 1991).
    Aquatic nonnative species are introduced and spread into new areas 
through a variety of mechanisms, both intentional and accidental, and 
authorized and unauthorized. Mechanisms for nonnative dispersal in the 
southwestern United States include inter-basin water transfer, sport 
stocking, aquaculture, aquarium releases, bait-bucket release (release 
of fish used as bait by anglers), and for use in biological control 
(U.S. Fish and Wildlife Service 2001).
    Dudley and Matter (2000) found that nonnative green sunfish prey 
on, compete with, and virtually eliminate recruitment of Gila chub (a 
recently federally listed species that is closely related to headwater 
chub) in Sabino Creek in Arizona. Similar effects of green sunfish on 
Gila chub have been documented in Silver Creek in Arizona (Unmack et 
al. 2003). In the Verde River, Bonar et al. (2004) found that 
largemouth bass, smallmouth bass, bluegill, green sunfish, channel 
catfish, flathead catfish, and yellow bullhead all consumed native 
fish. Roundtail chub (a closely related species to headwater chub) have 
been found in stomachs of largemouth bass in the lower Salt River (P. 
Unmack, Arizona State University, pers. comm. 2004). Bestgen and Propst 
(1989) reported that, of nonnatives present in New Mexico, smallmouth 
bass, flathead catfish, and channel catfish most impacted headwater 
chub via predation.
    Nonnative crayfish also appear to prey on and compete with all life 
stages of Gila chub (Carpenter 2000, 2005), a fish species closely 
related to headwater chub. At least two species of crayfish 
(Procambaris clarki and Orconectes virilis) have been introduced into 
Arizona aquatic systems and one or both species co-occur with headwater 
chub in at least four streams. Crayfish are considered a cause of 
decline for one population of headwater chub, and are documented as 
having contributed to the extirpation of two of its populations (Voeltz 
2002).
    Disease, and especially parasites, are a threat. Asian tapeworm 
(Bothriocephalus acheilognathi) was introduced into the United States 
via imported grass carp in the early 1970s. It has since become well-
established in the southeast and mid-south and has been recently found 
in the southwest. The definitive host in the life cycle of B. 
acheilognathi is cyprinid fishes, and, therefore, it is a potential 
threat to the headwater chub as well as to the other native fishes in 
Arizona. The Asian tapeworm affects fish health in several ways. Two 
direct impacts are by impeding the digestion of food as it passes 
through the intestinal track, and when large numbers of worms feed off 
of the fish they can cause emaciation and starvation. The Asian 
tapeworm is present in the Colorado River basin in the Virgin River 
(Heckman et al. 1986) and the Little Colorado River (Clarkson et al. 
1997). It has recently invaded the Gila River basin and was found 
during the fall 1998 Central Arizona Project (CAP) monitoring in the 
Gila River near Ashurst-Hayden Dam.
    Anchor worm (Lernaea cyprinacea) (Copepoda), an external parasite, 
is unusual in that it has little host specificity, infecting a wide 
range of fishes and amphibians. Severe Lernaea sp. infections have been 
noted in a number of chub populations. Hendrickson (1993) noted very 
high infections of Lernaea sp. during warm periods in the Verde River, 
and Voeltz (2002) reported that headwater chubs found in Gun Creek in 
2000, when surface flow was almost totally lacking, ``showed signs of 
stress, and many had Lernaea, black grub, lesions and an unidentified 
fungus.'' Increases in infection negatively affect headwater chub 
populations with Girmendonk and Young (1997) concluding that 
``parasitic infestations may greatly affect the health and thus 
population size of native fishes.''

Factor D: The Inadequacy of Existing Regulatory Mechanisms

    There are currently no specific Federal protections for headwater 
chub, and generalized Federal protections found in Forest plans, Clean 
Water Act dredge and fill regulations for streams, and other statutory, 
regulatory, or policy provisions have not been shown to be effective in 
preventing the decline of this species. Presently, Federal, State, and 
Tribal statutes, regulations, and planning have not achieved 
significant conservation of headwater chub and its habitat.
    As described above, introductions of nonnative fish are likely a 
significant threat to headwater chub. Fish introductions are illegal 
unless approved by the respective States. However, enforcement is 
difficult. Many nonnative fish populations are established through 
illegal introductions. Nine species of fish, crayfish, and waterdogs 
(tiger salamanders (Ambystoma pigrimum)) may be legally used as bait in 
Arizona, all of which are nonnative to the State of Arizona and several 
of which are known to have serious adverse effects on native species. 
The portion of the State in which use of live bait is permitted is 
limited, and use of live bait is restricted in much of the Gila River 
system in Arizona (Arizona Game and Fish Department 2004). New Mexico 
allows use of live bait-fish (New Mexico Game and Fish Department 
2004). Live bait use of two species of sunfish and all ``minnows'' are 
allowed. Goldfish (Carassius auratus), a nonnative formerly allowed for 
live bait use, is no longer allowed. Arizona and New Mexico also 
continue to stock nonnative fishes within areas that are connected to 
habitat of headwater chub.
    Increasing restrictions of live bait use will reduce the input of 
nonnative species into headwater chub habitat. However, it will do 
little to reduce unauthorized bait use or other forms of ``bait-
bucket'' transfer (e.g., dumping of unwanted aquarium fish, which may 
be invasive nonnative species) not directly related to bait use. In 
fact, those other ``bait-bucket'' transfers are expected to increase as 
the human population of Arizona increases and as nonnative species 
remain available to the public through aquaculture and the aquarium 
trade. The general public has been known to dump unwanted pet fish and 
other aquatic species into irrigation ditches such as the CAP aqueduct 
in the Phoenix metropolitan area (U.S. Fish and Wildlife Service 2001).
    The Arizona Game and Fish Department also regulates species of

[[Page 26016]]

nonnatives that can legally be brought into the State. Prohibited 
nonnative species are put onto the Restricted Live Wildlife List 
(Commission Order 12-4-406). However, species are allowed unless they 
are prohibited by placement on the list, rather than the more 
conservative approach of prohibited unless specifically allowed, and 
this leaves a serious regulatory inadequacy that allows the opportunity 
for many noxious nonnatives to be legally imported and introduced into 
Arizona. New Mexico has adopted a more stringent approach; no live 
animal (except domesticated animals or domesticated fowl or fish from 
government hatcheries) is allowed to be imported without a permit (NMS 
17-3-32). However, the majority of the headwater chub range occurs 
within Arizona.
    The Federal Land Policy Management Act of 1976 (43 U.S.