Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List a Distinct Population Segment of the Roundtail Chub (Gila robusta) in the Lower Colorado River Basin, 32352-32387 [E9-15828]
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DEPARTMENT OF THE INTERIOR
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Act (16
U.S.C. 1531 et seq.) requires that, for
50 CFR Part 17
any petition to revise the Lists of
[FWS–R2–ES–2009–0004; MO 92210530083–
Endangered and Threatened Wildlife
B2]
and Plants that contains substantial
scientific or commercial information
Endangered and Threatened Wildlife
that the action may be warranted, we
and Plants; 12-Month Finding on a
make a finding within 12 months of the
Petition To List a Distinct Population
date of the receipt of the petition on
Segment of the Roundtail Chub (Gila
whether the petitioned action is: (a) Not
robusta) in the Lower Colorado River
warranted, (b) warranted, or (c)
Basin
warranted but the immediate proposal
AGENCY: Fish and Wildlife Service,
of a regulation implementing the
Interior.
petitioned action is precluded by other
ACTION: Notice of 12-month petition
pending proposals to determine whether
finding.
species are threatened or endangered,
and expeditious progress is being made
SUMMARY: We, the U.S. Fish and
to add or remove qualified species from
Wildlife Service (Service), announce a
the Lists of Endangered and Threatened
12-month finding on a petition to list a
Wildlife and Plants. Section 4(b)(3)(C) of
distinct population segment (DPS) of the
the Act requires that we treat a petition
roundtail chub (Gila robusta) in the
for which the requested action is found
lower Colorado River basin as
to be warranted but precluded as though
endangered or threatened under the
resubmitted on the date of such finding,
Endangered Species Act of 1973, as
that is, requiring a subsequent finding to
amended (Act). The petition also asked
be made within 12 months. We must
the Service to designate critical habitat.
publish these 12-month findings in the
After review of all available scientific
Federal Register.
and commercial information, we find
Previous Federal Actions
that the petitioned listing action is
warranted, but precluded by higher
In 1985, the roundtail chub (Gila
priority actions to amend the Lists of
robusta) was placed on the list of
Endangered and Threatened Wildlife
candidate species as a category 2 species
and Plants. Upon publication of this 12- (50 FR 37958). Category 2 species were
month petition finding, this species will those for which existing information
be added to our candidate species list.
indicated that listing was possibly
We will develop a proposed rule to list
appropriate, but for which substantial
this population segment of the roundtail supporting biological data were lacking.
chub pursuant to our Listing Priority
Due to lack of funding to gather existing
System. Any determinations on critical
information on the roundtail chub, the
habitat will be made at that time.
species remained in category 2 through
DATES: The finding announced in this
the 1989 (54 FR 554), 1991 (56 FR
document was made on July 7, 2009.
58804) and 1994 (59 FR 58982)
ADDRESSES: This finding is available on
candidate notices of review. In the 1996
the Internet at https://
candidate notice of review (61 FR 7596),
www.regulations.gov at Docket Number
category 2 was eliminated, and
FWS–R2–ES–2009–0004. Supporting
roundtail chub no longer had formal
documentation we used in preparing
status under the candidate identification
this finding is available for public
system.
inspection, by appointment, during
On April 14, 2003, we received a
normal business hours at the U.S. Fish
petition from the Center for Biological
and Wildlife Service, Arizona Ecological Diversity requesting that we list a DPS
Services Office, 2321 West Royal Palm
of the roundtail chub (Gila robusta) in
Road, Suite 103, Phoenix, AZ 85021–
the lower Colorado River basin (defined
4951. Please submit any new
as all waters tributary to the Colorado
information, materials, comments, or
River in Arizona and the portion of New
questions concerning this finding to the Mexico in the Gila River and Zuni River
above address.
basins) as endangered or threatened,
FOR FURTHER INFORMATION CONTACT:
that we list the headwater chub (Gila
Steve Spangle, Field Supervisor,
nigra) as endangered or threatened, and
Arizona Ecological Services Office (see
that we designate critical habitat
ADDRESSES), telephone 602–242–0210. If concurrently with the listing for both
you use a telecommunications device
species.
Following receipt of the 2003 petition,
for the deaf (TDD), please call the
and pursuant to a stipulated settlement
Federal Information Relay Service
agreement, on July 12, 2005, we
(FIRS) at 800–877–8339.
Fish and Wildlife Service
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published our 90-day finding that the
petition presented substantial scientific
information indicating that listing the
headwater chub and a DPS of the
roundtail chub in the lower Colorado
River basin may be warranted, and we
initiated 12-month status reviews for
these species (70 FR 39981).
On May 3, 2006, we published our 12month finding that listing was
warranted for the headwater chub, but
precluded by higher priority listing
actions, and that listing of a population
segment of the roundtail chub in the
lower Colorado River basin was not
warranted because it did not meet our
definition of a DPS (71 FR 26007).
On September 7, 2006, we received a
complaint from the Center for Biological
Diversity for declaratory and injunctive
relief, challenging our decision not to
list the lower Colorado River basin
population of the roundtail chub as an
endangered species under the Act. On
November 5, 2007, in a stipulated
settlement agreement, we agreed to
commence a new status review of the
lower Colorado River basin population
segment of the roundtail chub and to
submit a 12-month finding to the
Federal Register by June 30, 2009. On
March 3, 2009, we published a notice in
the Federal Register that we were
initiating a status review and soliciting
new information for reevaluating the
2003 petition to list a lower Colorado
River basin DPS of the roundtail chub
(74 FR 9205).
Defining a Species Under the Act
Section 3(16) of the Act defines
‘‘species’’ to include ‘‘any subspecies of
fish or wildlife or plants, and any
distinct population segment of any
species of vertebrate fish or wildlife
which interbreeds when mature’’ (16
U.S.C. 1532(16)). Our implementing
regulations at 50 CFR 424.02 provide
further guidance for determining
whether a particular taxon or
population is a species or subspecies for
the purposes of the Act: ‘‘[T]he
Secretary shall rely on standard
taxonomic distinctions and the
biological expertise of the Department
and the scientific community
concerning the relevant taxonomic
group’’ (50 CFR 424.11(a)). As
previously discussed, the population
segment of roundtail chub in the lower
Colorado River basin is classified as Gila
robusta, the same as other roundtail
chub populations, and as such we do
not consider the population segment of
roundtail chub in the lower Colorado
River basin to constitute a distinct
species or subspecies. Since the
population segment of roundtail chub in
the lower Colorado River basin is not a
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distinct species or subspecies, we then
evaluated whether it is a distinct
population segment to determine
whether it would constitute a listable
entity under the Act.
To interpret and implement the DPS
provisions of the Act and Congressional
guidance, the Service and the National
Marine Fisheries Service (now the
National Oceanic and Atmospheric
Administration—Fisheries), published
the Policy Regarding the Recognition of
Distinct Vertebrate Population Segments
Under the Endangered Species Act (DPS
Policy) in the Federal Register on
February 7, 1996 (61 FR 4722). Under
the DPS Policy, three elements are
considered in the decision regarding the
establishment and classification of a
population of a vertebrate species as a
possible DPS. These are applied
similarly for additions to and removals
from the Lists of Endangered and
Threatened Species. These elements are
(1) the discreteness of a population in
relation to the remainder of the species
to which it belongs, (2) the significance
of the population segment to the species
to which it belongs, and (3) the
population segment’s conservation
status in relation to the Act’s standards
for listing, delisting, or reclassification
(i.e., is the population segment
endangered or threatened?).
Distinct Vertebrate Population Segment
Analysis
In the 2003 petition, we were asked to
consider listing a DPS for the roundtail
chub in the lower Colorado River basin
(the Colorado River and its tributaries
downstream of Glen Canyon Dam
including the Gila and Zuni River
basins in New Mexico). Per our
November 5, 2007, stipulated settlement
agreement, we are reevaluating our May
3, 2006, determination (71 FR 26007)
that listing the roundtail chub
population segment in the lower
Colorado River basin was not warranted
because it did not meet our definition of
a DPS.
In accordance with our DPS Policy,
this section details our analysis of the
first two elements we consider in a
decision regarding the status of a
possible DPS as endangered or
threatened under the Act. These
elements are (1) the population
segment’s discreteness from the
remainder of the species to which it
belongs and (2) the significance of the
population segment to the species to
which it belongs.
Discreteness
The DPS policy’s standard for
discreteness requires an entity to be
adequately defined and described in
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some way that distinguishes it from
other representatives of its species. A
population segment of a vertebrate
species may be considered discrete if it
satisfies either one of the following two
conditions: (1) It is markedly separated
from other populations of the same
taxon as a consequence of physical,
physiological, ecological, or behavioral
factors (quantitative measures of genetic
or morphological discontinuity may
provide evidence of this separation); or
(2) it is delimited by international
governmental boundaries within which
significant differences in control of
exploitation, management of habitat,
conservation status, or regulatory
mechanisms exist.
The historical range of roundtail chub
included both the upper and lower
Colorado River basins in the States of
Wyoming, Utah, Colorado, New Mexico,
Arizona, and Nevada (Propst 1999, p.
23; Bezzerides and Bestgen 2002, p. 25;
Voeltz 2002, pp. 19–23), but the
roundtail chub was likely only a
transient in Nevada. Currently roundtail
chubs occur in both the upper and
lower Colorado River basins in
Wyoming, Utah, Colorado, New Mexico,
and Arizona. Bezzerides and Bestgen
(2002, p. 24) concluded that historically
there were two discrete population
centers, one in each of the lower and
upper basins, and that these two
population centers remain today.
Numerous authors have noted that
roundtail chub was very rare with few
documented records in the mainstem
Colorado River between the two basins
(Minckley 1973, p. 102; Minckley 1979,
p. 51; Valdez and Ryel 1994, pp. 5–10–
5–11; Minckley 1996, p. 75; Bezzerides
and Bestgen 2002, pp. 24–25; Voeltz
2002, pp. 19, 112), so we do not
consider the mainstem to have been
occupied historically, and have not
considered the Colorado River in our
estimates of historical range. Early
surveyors also variably used the term
‘‘bonytail’’ to describe roundtail chub
(Valdez and Ryel 1994, pp. 5–7), further
clouding information on historical
distribution, as some accounts of
roundtail chub in the mainstem may
have been bonytail (Gila elegans), which
is a mainstem species in the Colorado
River. Records from the mainstem
Colorado River also may have been
transients from nearby populations,
such as some records from Grand
Canyon, which may have been from the
Little Colorado River (Voeltz 2002, p.
112). One record from between the two
basins, a record of two roundtail chubs
captured near Imperial Dam in 1973,
illustrates this. Upon examining these
specimens, Minckley (1979, p. 51)
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concluded that they were strays washed
downstream from the Bill Williams
River based on their heavily blotched
coloration. This is a logical conclusion
considering that roundtail chub from
the Bill Williams River typically exhibit
this blotched coloration (Rinne 1969,
pp. 20–21; Rinne 1976, p. 78). Minckley
(1979, p. 51), Minckley (1996, p. 75),
and Mueller and Marsh (2002, p. 40)
also considered roundtail chub rare or
essentially absent in the Colorado River
mainstem based on the paucity of
records from numerous surveys of the
Colorado River mainstem.
We conclude that historically,
roundtail chub occurred in the Colorado
River basin in two population centers,
one each in the upper (largely in Utah
and Colorado, and to a lesser extent, in
Wyoming and New Mexico) and lower
basins (Arizona and New Mexico), with
apparently little, if any, mixing of the
two populations. If there was one
population, we would expect to find a
large number of records in the mainstem
Colorado River between the San Juan
and Bill Williams Rivers, but very few
records of roundtail chub exist from this
reach of stream. Also, there is a
substantial distance between these areas
of roundtail chub occurrence in the two
basins. The mouth of the Escalante
River, which contains the southernmost
population of roundtail chub in the
upper basin, is approximately 275 river
miles (mi) (443 kilometers (km))
upstream from Grand Falls on the Little
Colorado River, the historical
downstream limit of the most northern
population of the lower Colorado River
basin. The lower Colorado River basin
roundtail chub population segment
meets the element of discreteness
because it was separate historically, and
continues to be markedly separate
today.
In more recent times, the upper and
lower basin populations of the roundtail
chub have been physically separated by
Glen Canyon Dam, but that artificial
separation is not the sole basis for our
finding that the lower basin population
is discrete from the upper basin. The
historical information on collections
suggests that there was limited contact
even before the dam was built.
Available molecular information for the
species, although sparse, seems to
support this; mitochondrial DNA
markers (mtDNA; a type of genetic
material) of roundtail chub in the Gila
River basin are entirely absent from
upper basin populations (Gerber et al.
2001, p. 2028; see Significance
discussion below).
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Significance
If we have determined that a
vertebrate population segment is
discrete under our DPS policy, we
consider its biological and ecological
significance to the taxon to which it
belongs in light of Congressional
guidance (see Senate Report 151, 96th
Congress, 1st Session) that the authority
to list DPSs be used ‘‘sparingly’’ while
encouraging the conservation of genetic
diversity. To evaluate whether a discrete
vertebrate population may be significant
to the taxon to which it belongs, we
consider available scientific evidence of
the discrete population segment’s
importance to the taxon to which it
belongs. Since precise circumstances are
likely to vary considerably from case to
case, the DPS policy does not describe
all the classes of information that might
be used in determining the biological
and ecological importance of a discrete
population. However, the DPS policy
describes four possible classes of
information that provide evidence of a
population segment’s biological and
ecological importance to the taxon to
which it belongs. This consideration
may include, but is not limited to: (1)
Persistence of the discrete population
segment in an ecological setting that is
unusual or unique for the taxon; (2)
evidence that loss of the discrete
population segment would result in a
significant gap in the range of the taxon;
(3) evidence that the discrete population
segment represents the only surviving
natural occurrence of a taxon that may
be more abundant elsewhere as an
introduced population outside its
historical range; or (4) evidence that the
discrete population segment differs
markedly from other populations of the
species in its genetic characteristics.
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 PeaksMogollon Rim Section of the ArizonaNew Mexico Mountains Semi-DesertOpen 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
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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-DesertConiferous Forest Province in the Dry
Domain (McNabb and Avers 1994;
Bailey 1995). These ecoregions display
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 (in)
per year (8–165 centimeters (cm) per
year)) (Jeppson 1968, p. 1) somewhat
less arid than the lower basin (5–25 in
per year (13–64 cm per year)) (Green
and Sellers 1964, pp. 8–11).
The type (snow or rain) and timing of
precipitation are major factors
determining the pattern of annual
streamflow. A hydrograph depicts the
amount of runoff or discharge over time
(Leopold 1997, pp. 49–50). 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, pp. B3–B7; Green and
Sellers 1964, pp. 8–11; Minckley and
Rinne 1991, p.12). 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, pp. B3–B7; Ray et al.
2007, p. 1617).
In the upper basin, roundtail chub
habitats have strong snowmelt
hydrographs, with some summer, fall,
and winter precipitation, but with the
majority of major flow events in spring
and early summer (Bailey 1995, p. 341;
Carlson and Muth 1989, p. 222;
Woodhouse et al. 2003, p. 1551).
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; in contrast,
this is typically the wettest period in the
upper basin (Carlson and Muth 1989, p.
222). Regarding the differences between
the two basins, Carlson and Muth
(1989), for example, conclude, ‘‘The
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upper basin produced most of the river’s
discharge, and peak flows occurred after
snowmelt in spring and early summer.
Maximum runoff in the lower basin
often followed winter rainstorms.’’
Sediment loads vary substantially
between streams in both basins, but are
generally lesser in the upper basin than
the lower, 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.
Gap in the Range. Roundtail chub in
the lower Colorado River basin can be
considered significant under our DPS
analysis because loss of the lower
Colorado River populations of roundtail
chub would result in a significant gap
in the range of the taxon; this area
constitutes over one third of the species’
historical range (2 out of 6 States),
including the species’ entire current
range in two States (Arizona and New
Mexico) and all of several major river
systems, including the Little Colorado,
Bill Williams, and Gila River basins.
Additionally there are 74 populations of
roundtail chub remaining in the upper
basin and 31 in the lower basin; thus,
the lower basin populations also
constitute approximately one third (30
percent) of the remaining populations of
the species (Bezzerides and Bestgen
2002, pp. 28–29, Appendix C; Voeltz
2002, pp. 82–83). The populations in
the lower basin also account for
approximately 107,300 square mi
(270,906 square km; 49 percent) of the
219,310 square mi (568,010 square km)
of the Colorado River Basin (U.S.
Geological Survey 2006, pp. 94–102). In
addition, the roundtail chub historically
occupied up to 2,796 mi (4,500 km) of
stream in the lower basin and currently
occupies between 497 mi (800 km) and
901 mi (1450 km) of stream habitat in
the lower basin. These populations are
not newly established, ephemeral, or
migratory; the species has been well
established in the lower Colorado River
basin, and has represented a large
portion of the species’ range for a long
period of time (Bezzerides and Bestgen
2002, pp. 20–29; Voeltz 2002, pp. 82–
83).
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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 historical 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.
Marked Differences in Genetic
Characteristics. Long-standing
difficulties in morphological
discrimination and taxonomic
distinction among members from the
lower Colorado G. robusta complex, and
the genus Gila as a whole, due in part
to the role hybridization has played in
its evolution, have plagued conservation
efforts. But it is important to consider
variation throughout the entire Colorado
River basin to place variation and
divergence in the lower basin Gila
robusta complex in appropriate context.
Two isolated species of hybrid origin
(involving G. robusta with G. elegans
and G. cypha) can be found in the
Virgin and White River drainages (G.
seminuda—DeMarais et al. 1992, p.
2747; G. jordani—Gerber et al. 2001, p.
2033, respectively). Gila robusta is
relatively abundant in the mainstem
Colorado River and tributaries above the
Glen Canyon Dam in the upper basin.
All individuals from the headwaters of
the Little Colorado River and the
mainstem Colorado River and tributaries
above Glen Canyon Dam in the upper
basin possess G. cypha or G. elegans
mtDNA (Dowling and DeMarais 1993,
pp. 444–446; Gerber et al. 2001, p.
2028). However, populations of the G.
robusta complex of the lower basin in
the Bill Williams and Gila River basins
(including G. robusta, G. intermedia,
and G. nigra) possess a unique,
divergent mtDNA lineage that has never
been found outside the lower basin
(Dowling and DeMarais 1993, pp. 444–
446; Gerber et al. 2001, p. 2028). But as
Gerber et al. (2001, p. 2037) noted,
genetic information in Gila poorly
accounts for species morphology, stating
‘‘the decoupling of morphological and
mtDNA variation in Colorado River Gila
illustrates how hybridization and local
adaptation can play important roles in
evolution.’’ Although individuals in the
Little Colorado River illustrate some
minor genetic uniqueness, the evidence,
though limited (samples size in Gerber
et al. 2001 was limited to 7 individuals)
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indicates these populations align more
closely with the upper Colorado River
basin populations. But discriminating
between populations of Gila based on
these data is difficult, and more data
and analysis may help to place these
populations in better perspective.
DPS Conclusion
We have reevaluated the lower
Colorado River populations of the
roundtail chub to determine whether
they meet the definition of a DPS,
addressing discreteness and significance
as required by our policy. We have
considered the extent of the range of the
roundtail chub in the lower Colorado
River basin relative to the rest of the
species’ range, the ecological setting of
roundtail chub in the lower Colorado
River basin, and available information
on the genetics of the species. We
conclude that the lower Colorado River
populations are discrete from the upper
Colorado River basin populations on the
basis of their present and historical
geographic separation of 275 river mi
(444 km) and because few historical
records have been detected in the
mainstem Colorado River between the
two population centers that would
confirm significant connectivity
historically. We also conclude that the
lower Colorado River basin roundtail
chub is significant because of its unique
ecological setting compared to the upper
basin, and because the loss of the
species from the lower basin would
result in a significant gap in the range
of the species. Genetic information for
this species has long been difficult to
interpret, and additional data and
analysis may help to clarify this.
In our 2006 finding, we made the
determination that the roundtail chub in
the lower Colorado River basin did not
meet our definition of a DPS. We have
reevaluated that determination and now
find the best available information has
demonstrated that these populations are
discrete, persist in an ecological setting
that is unique for the taxon, and, if lost,
would result in a significant gap in the
range of the taxon. Because this
population segment meets both the
discreteness and significance elements
of our DPS policy, the lower Colorado
River population segment of the
roundtail chub qualifies as a DPS in
accordance with our DPS policy, and as
such, is a listable entity under the Act.
Below we provide a summary of the
biology, status, and distribution of the
DPS, and an analysis of threats to the
DPS, based on the five listing factors
established by the Act.
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Biology
The roundtail chub is a cyprinid fish
(member of Cyprinidae, the minnow
family) with a streamlined body shape.
Color in roundtail chub is usually olivegray to silvery, with the belly lighter,
and sometimes with dark blotches on
the sides. Roundtail chubs are generally
9 to 14 in. (25 to 35 cm) in length, but
can reach 20 in. (50 cm) (Minckley
1973, pp. 101–103; Sublette et al. 1990,
pp. 126–129; Propst 1999, pp. 23–25;
Minckley and Demaris 2000, pp. 251–
256; Voeltz 2002, pp. 8–11). Baird and
Girard first described roundtail chub
from specimens collected from the Zuni
River in northeastern Arizona and
northwestern New Mexico (Baird and
Girard 1853, pp. 368–369). Roundtail
chub has been recognized as a distinct
species since the 1800s (Miller 1945, p.
104; Holden 1968, pp. 27–28; Rinne
1969, pp. 27–42; Holden and Stalnaker
1970, p. 409; Rinne 1976, pp. 87–91;
Smith et al. 1979, p. 623; DeMarais
1986, p. iii; Douglas et al. 1989, p. 653;
Rosenfeld and Wilkinson 1989, p. 232;
DeMarais 1992, pp. 63–64; Dowling and
DeMarais 1993, p. 444; Douglas et al.
1998, p. 169; Minckley and DeMarais
2000, p. 255; Gerber et al. 2001, p.
2028), and is currently recognized as a
species by the American Fisheries
Society (Nelson et al. 2004, p. 71). The
chubs of the genus Gila in the lower
Colorado River basin are all closely
related and are often regarded as a
species complex (Minckley 1973, p. 101;
DeMarais 1992, p. 150; Dowling and
DeMarais 1993, p. 444; Minckley and
DeMarais 2000, p. 251; Gerber et al.
2001, p. 2028).
Roundtail chubs in the lower
Colorado River basin are found in cool
to warm waters of rivers and streams,
and often occupy the deepest pools and
eddies of large streams (Minckley 1973,
p. 101; Brouder et al. 2000, pp. 6–8;
Minckley and DeMarais 2000, p. 255;
Bezzerides and Bestgen 2002, pp. 17–
19). Although roundtail chubs are often
associated with various cover features,
such as boulders, vegetation, and
undercut banks, they are less apt to use
cover than other related species such as
the headwater chub and Gila chub (Gila
intermedia) (Minckley and DeMarais
2000, p. 2145). Water temperatures of
habitats occupied by roundtail chub
vary between 0 degrees and greater than
32 degrees Celsius (°C) (32 to 90 degrees
Fahrenheit (°F)) (Bestgen 1985, p. 14).
Carveth et al. (2006, p. 1435) reported
the upper thermal tolerance of roundtail
chub to be 36.6 °C (97.9 °F); spawning
has been documented from 14 to 24 °C
(57 to 75 °F) (Bestgen 1985, p. 14;
Kaeding et al. 1990, p. 139; Brouder et
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al. 2000, p. 13). Spawning occurs from
February through June in pool, run, and
riffle habitats, with slow to moderate
water velocities (Neve 1976, p. 32;
Bestgen 1985, pp. 56–67; Propst 1999, p.
24; Brouder et al. 2000, p. 12; Voeltz
2002, p. 16). Roundtail chubs live for 5
to 7 years and spawn from age 2 on
(Bestgen 1985, p. 62; Brouder et al.
2000, p. 12). Roundtail chubs are
omnivores, consuming foods
proportional to their availability,
including aquatic and terrestrial
invertebrates, aquatic plants, detritus,
and fish and other vertebrates; algae and
aquatic insects can be major portions of
the diet (Bestgen 1985, pp. 46–53;
Schreiber and Minckley 1981, pp. 409,
415; Propst 1999, p. 24).
Status and Distribution of the Lower
Colorado River DPS
The historical distribution of
roundtail chub in the lower Colorado
River basin is poorly documented
because there were few early
collections, and perhaps more
importantly, because many populations
of native fish, including roundtail chub,
were likely lost prior to early
comprehensive fish surveys because
habitat-altering actions (e.g., dewatering,
livestock grazing, mining) were
widespread, and had already severely
altered aquatic habitats (Girmendonk
and Young 1997, p. 50; Minckley 1999,
p. 179; Voeltz, 2002, p. 19). Roundtail
chub was historically considered
common throughout its range (Minckley
1973, p. 101; Holden and Stalnaker
1975, p. 222; Propst 1999, p. 23). Voeltz
(2002), estimating historical distribution
based on museum collection records,
agency database searches, literature
searches, and discussion with biologists,
found that roundtail chub in the lower
Colorado River basin was historically
found in the Gila and Zuni Rivers in
New Mexico; the Black, Colorado
(though likely only as a transient), Little
Colorado, Bill Williams, Gila, San
Francisco, San Carlos, San Pedro, Salt,
Verde, White, and Zuni Rivers in
Arizona: and numerous tributaries
within those basins. Voeltz (2002, p. 83)
estimated the lower Colorado River
basin roundtail chub historically
occupied approximately 2,796 mi (4,500
km) of rivers and streams in Arizona
and New Mexico. Although roundtail
chubs were never collected from the
Colorado River or San Pedro River basin
in Mexico, they may have occurred in
these areas based on records near the
international border in the lower
Colorado River and upper San Pedro
River and the occurrence of suitable
habitat in these streams in Mexico
(Voeltz 2002, p. 20).
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Miller (1961) first comprehensively
documented the decline of fishes of the
southwestern United States in 1961, but
interestingly, F.M. Chamberlain made
similar observations in Arizona in 1904;
roundtail chub was included in these
assessments and in subsequent
evaluations of imperiled fish species of
the region (Miller 1961, pp. 373–379;
Miller 1972, p. 242; Deacon et al. 1979,
p. 34; Minckley 1999, pp. 215–218). The
decline of the species has been
documented both in the scientific peerreviewed literature (Bestgen and Propst
1989, p. 402) and in State agency reports
(Girmendonk and Young 1997, p. 49;
Propst 1999, p. 23; Brouder et al. 2000,
p. 1; Bezzerides and Bestgen 2002, pp.
iii–iv; Voeltz 2002, p. 83). Roundtail
chub is considered vulnerable by the
American Fisheries Society (Jenks et al.
2008, p. 390).
Roundtail chub in the lower Colorado
River basin in Arizona currently occurs
in two tributaries of the Little Colorado
River (Chevelon and East Clear Creeks);
several tributaries of the Bill Williams
River basin (Boulder, Burro, Conger,
Francis, Kirkland, Sycamore, Trout, and
Wilder Creeks); the Salt River and four
of its tributaries (Ash Creek, Black
River, Cherry Creek and Salome Creek);
the Verde River and five of its
tributaries (Fossil, Oak, Roundtree
Canyon, West Clear, and Wet Beaver
Creeks); Aravaipa Creek (a tributary of
the San Pedro River); Eagle Creek (a
tributary of the Gila River); and in New
Mexico, in the upper Gila River (Voeltz
2002, pp. 82–83; the upper Gila River is
used in this document to denote that
portion of the Gila River basin in New
Mexico). The Salt River and Verde River
are occupied in several reaches that are
fragmented and separated by two large
dams and reservoirs on the Verde River,
and four large dams and reservoirs on
the Salt River. Roundtail chubs also
occur in canals in Phoenix that are fed
by the lower Salt and Verde Rivers.
Roundtail chubs inhabit several streams
in the Salt River drainage, although
survey information on the San Carlos
Apache Reservation and White
Mountain Apache Reservation is
proprietary and confidential, and their
status is not currently known; these
streams include Canyon, Carrizo, Cedar,
Cibecue, and Corduroy Creeks, and the
White River (Voeltz 2002, pp. 82–83).
The Arizona Game and Fish
Department (AGFD) conducted a
comprehensive status review of
roundtail and headwater chub (Voeltz
2002) in the lower Colorado River basin
that included a review of all available
current and historical survey records
and estimated historical and current
range of roundtail chub using
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information from museum collections,
agency databases, records found in
literature, and consultation with
experts. The report found that roundtail
chub populations and distribution had
declined significantly from historical
levels. Based on Voeltz (2002), roundtail
chub is known to occupy only 18
percent of its former range in the lower
Colorado River basin; status in an
additional 14 percent of its range is
unknown. Based on the best available
scientific information in Voeltz (2002),
the roundtail chub in the lower
Colorado River basin appears to occupy
about 18 to 32 percent of its former
range (approximately 497 mi (800 km)
out of the 2,796 mi (4,500 km))
considered to be formerly occupied) in
Arizona and New Mexico. We now
consider the Colorado River in the lower
Colorado River basin to be outside the
historical range of the species (Voeltz
considered it to have been occupied);
given this, roundtail chub has been
extirpated from 672 mi (965 km) of
2,197 mi (3,535 km; approximately 60
percent) of its formerly occupied range.
Of the populations for which status and
threat information is available, all but
one of the remaining natural
populations are considered threatened
by both the presence of nonnative
species and habitat-altering land uses.
In the report, Voeltz (2002) used a
classification system to report status and
threat information. Populations were
defined as an occurrence at a streamspecific locality. A population was
considered ‘‘stable-secure,’’ ‘‘stablethreatened,’’ or ‘‘unstable-threatened,’’
based on abundance, population trend,
and threat information for the locality
(see Table 1, Voeltz 2002, p. 5). Voeltz
(2002, p. 5) considered a population
‘‘extirpated’’ if the species was no
longer believed to occupy the site, and
‘‘unknown’’ if there are too few data to
determine status. Note that the term
‘‘threatened’’ as used by Voeltz (2002, p.
5) is not the definition of ‘‘threatened’’
used in the Act in which a species is
likely to become endangered in the
foreseeable future, but rather is an
estimate of the likelihood that a
population is likely to become
extirpated. Of 40 populations of
roundtail chub in the lower Colorado
River basin identified in the report,
Voeltz (2002, pp. 82–87) found that
none were ‘‘stable-secure,’’ 6 were
‘‘stable-threatened,’’ 13 were ‘‘unstablethreatened,’’ 10 were ‘‘extirpated,’’ and
11 were of ‘‘unknown’’ status.
Populations with an ‘‘unknown’’ status
in Voeltz (2002) included nine
populations wholly or partly on Tribal
lands. Tribes are sovereign nations and
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survey data is proprietary and
confidential, but existing survey
information for these streams was
provided and indicated occupancy. The
remaining two populations with
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‘‘unknown’’ status lacked sufficient
information to assign a category.
TABLE 1—DEFINITIONS OF STATUS DESCRIPTION CATEGORIES USED TO DESCRIBE ROUNDTAIL CHUB POPULATIONS
[From Voeltz 2002]
Status
Definition
Stable-Secure (SS) .....................
Chubs are abundant or common, data over the past 5–10 years shows a stable, reproducing population with
successful recruitment (survival of young to Age 2, reproductive age); no impacts from nonnative aquatic
species exist; and no current or future habitat altering land or water uses were identified.
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.
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.
Chubs are no longer believed to occur in the system.
Lack of data precludes determination of status.
Stable-Threatened (ST) ...............
Unstable-Threatened (UT) ..........
Extirpated (E) ..............................
Unknown (UN) .............................
We have updated this assessment
with new data from various sources,
particularly Cantrell (2009) as provided
in Table 2 below. It is important to
recognize that these status categories are
qualitative, and based on very limited
data in most instances. We have very
little information on the population
size, length of the stream reach,
survivorship, recruitment (survival of
young to Age 2, reproductive age), or
age structure of these populations.
These categories are also often based on
only a few surveys conducted over
decadal time scales. We now consider 1
population ‘‘stable-secure,’’ 8
populations ‘‘stable-threatened,’’ 13
populations ‘‘unstable-threatened,’’ and
9 populations ‘‘unknown.’’ Ten
populations remain extirpated although
we now consider what was called a
population in the Colorado River to
have been occupied only by transient
individuals. In the nine populations
with ‘‘unknown’’ status, two (Ash Creek
and Roundtree Creek) are newly
established via translocation and have
not been extant long enough to
determine successful establishment.
Information on the Black River and
Conger Creek provided since the 2002
report resulted in recategorization of
both of those sites from ‘‘unknown’’ to
‘‘stable-threatened’’ and for
recategorization of Eagle Creek from
‘‘unknown’’ to ‘‘unstable-threatened.’’
Improved status at Fossil Creek that
allows that population to reach ‘‘stablesecure’’ is due to removal of the power
plant and associated structures,
construction of a new fish barrier, and
chemical renovation to remove
nonnative fish species. Recent surveys
have confirmed some of the information
in Voeltz’s 2002 status review; in the
upper Black River, Chevelon Creek, and
East Clear Creek, the species persists in
the presence of abundant nonnative
predators, and apparently reproduces
successfully, but distribution appears
limited, abundance is unknown, and
other signs, such as abundance of other
native fish species, indicate these native
fisheries are deteriorating (AGFD 2005a,
p. 4; 2005b, pp. 4–5; Clarkson and
Marsh 2005a, pp. 6–8; 2005b, pp. 6–7).
Other roundtail chub populations in
waters with abundant nonnative
predators are less able to reproduce
successfully and the particular
circumstances at these three sites are
worth further investigation. Roundtail
chub in the lower Colorado River basin
in New Mexico may now be extirpated.
The species has long been considered
extirpated in many Gila River tributaries
in New Mexico, and has become very
rare in the mainstem Gila River (Carman
2006, pp. 9, 18).
TABLE 2—SUMMARY OF ROUNDTAIL CHUB STATUS AND THREATS BY STREAM REACH
[Voeltz 2002, Cantrell 2009, service files]
Location
Current
status
Regional historical or current threats
Management Area A—Gila River Basin
Aravaipa Creek ................
ST
Blue River ........................
E
Eagle Creek .....................
UT
San Francisco River ........
E
Upper Gila River ..............
UT
Lower Gila River ..............
E
San Pedro River ..............
E
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Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing, road use.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, logging and fuel wood cutting, recreation, livestock
grazing, road use.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, recreation, mining, livestock grazing.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
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TABLE 2—SUMMARY OF ROUNDTAIL CHUB STATUS AND THREATS BY STREAM REACH—Continued
[Voeltz 2002, Cantrell 2009, service files]
Location
Current
status
Regional historical or current threats
Factor C: Nonnative species.
Management Area A—Salt River Basin
Ash Creek ........................
Black River .......................
UN
ST
Canyon Creek ..................
UN
Carrizo Creek ...................
UN
Cedar Creek ....................
UN
Cherry Creek ...................
ST
Cibecue Creek .................
UN
Corduroy Creek ...............
UN
Salome Creek ..................
UT
Salt River .........................
UT
White River ......................
UN
Factor A: Recreation, logging and fuel wood cutting, livestock grazing.
Factor A: Water diversions, groundwater pumping, recreation, livestock grazing, mining, logging and fuel
wood cutting, urban and agricultural development.
Factor C: Nonnative species.
Factor A: Livestock grazing, recreation, limited fuelwood harvest, limited agriculture, fisheries and wildlife management, and localized municipal, urban and rural development and associated water use.
Factor C: Nonnative species.
Factor A: Livestock grazing, recreation, limited fuelwood harvest, limited agriculture, fisheries and wildlife management, and localized municipal, urban and rural development and associated water use.
Factor C: Nonnative species.
Factor A: Livestock grazing, recreation, limited fuelwood harvest, limited agriculture, fisheries and wildlife management, and localized municipal, urban and rural development and associated water use.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, mining, recreation, livestock grazing, logging and fuel
wood cutting, urban and agricultural development.
Factor C: Nonnative species.
Factor A: Livestock grazing, recreation, limited fuelwood harvest, limited agriculture, fisheries and wildlife management, and localized municipal, urban and rural development and associated water use.
Factor C: Nonnative species.
Factor A: Livestock grazing, recreation, limited fuelwood harvest, limited agriculture, fisheries and wildlife management, and localized municipal, urban and rural development and associated water use.
Factor C: Nonnative species.
Factor A: Recreation, logging and fuel wood cutting, livestock grazing.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, recreation, livestock grazing, mining, logging and fuel
wood cutting, urban and agricultural development.
Factor C: Nonnative species.
Management Area A—Verde River Basin
Dry Beaver Creek ............
E
Fossil Creek .....................
SS
Oak Creek ........................
UT
Roundtree Canyon ...........
Verde River ......................
UN
ST
West Clear Creek ............
ST
Wet Beaver Creek ...........
UT
Factor A: Water diversions, dewatering, livestock grazing, logging and fuel wood cutting, recreation.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, dewatering, mining, contaminants, urban and agricultural development, livestock grazing.
Factor A: Water diversions, groundwater pumping, dewatering, mining, contaminants, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Recreation, logging and fuel wood cutting, livestock grazing.
Factor A: Water diversions, groundwater pumping, dewatering, mining, contaminants, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Water diversions, dewatering, livestock grazing, logging and fuel wood cutting, recreation.
Factor C: Nonnative species.
Factor A: Water diversions, dewatering, livestock grazing, logging and fuel wood cutting, recreation.
Factor C: Nonnative species.
Management Area B—Bill Williams River Basin
Big Sandy River ...............
E
Bill Williams River ............
E
Boulder Creek ..................
ST
Burro Creek .....................
UT
Conger Creek ..................
ST
Francis Creek ..................
UT
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Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing, residential development.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing.
Factor C: Nonnative species.
Factor A: Groundwater pumping, recreation, livestock grazing.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.
Factor C: Nonnative species.
Factor A: Groundwater pumping, mining, livestock grazing, recreation.
Factor C: Nonnative species.
Factor A: Groundwater pumping, mining, livestock grazing, recreation.
Factor C: Nonnative species.
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TABLE 2—SUMMARY OF ROUNDTAIL CHUB STATUS AND THREATS BY STREAM REACH—Continued
[Voeltz 2002, Cantrell 2009, service files]
Location
Current
status
Kirkland Creek .................
UT
Santa Maria River ............
UT
Sycamore Creek ..............
UT
Trout Creek ......................
ST
Wilder Creek ....................
UN
Regional historical or current threats
Factor A: Groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.
Factor C: Nonnative species.
Factor A: Groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, recreation, residential development.
Factor C: Nonnative species.
Factor A: Groundwater pumping, mining, livestock grazing, recreation.
Factor C: Nonnative species.
Management Area C—Little Colorado River Basin
Chevelon Creek ...............
UT
East Clear Creek .............
UT
Little Colorado River ........
E
Zuni River ........................
E
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing, contaminants.
Factor C: Nonnative species.
Factor A: Logging and fuel wood cutting, recreation, mining, livestock grazing, contaminants.
Factor C: Nonnative species.
Factor A: Dams, water diversions, groundwater pumping, dewatering, logging and fuel wood cutting,
recreation, mining, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
Factor A: Water diversions, groundwater pumping, dewatering, mining, contaminants, urban and agricultural development, livestock grazing.
Factor C: Nonnative species.
SS—Stable-Secure; ST—Stable-Threatened; UT—Unstable-Threatened; E—Extirpated; UN—Unknown.
Populations of roundtail chub are
found in five separate drainages that are
isolated from one another (the Little
Colorado River, Bill Williams River,
Gila River, Salt River, and Verde River),
and populations within the drainages
have varying amounts of connectivity
between them. Using large-scale
watersheds, AGFD created
‘‘management areas’’ and ‘‘significant
conservation units’’ based on currently
occupied roundtail habitats. AGFD has
utilized new genetic studies (Dowling et
al. 2008; Schwemm 2006; See Table 2)
to refine these management areas. Based
on genetic similarity, the Verde, Salt,
and Gila Rivers and their tributaries
constitute Management Area A, the Bill
Williams and its tributaries are
Management Area B, and the Little
Colorado River and its tributaries are
Management Area C. Cantrell (2009, p.
9) also refined significant conservation
units for management purposes based
on genetic information (Dowling et al.
2008; Schwemm 2006); however the
mechanism for selecting these units and
determination of stability versus
instability of a management area or
significant conservation units was not
clearly described.
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Summary of Factors Affecting the
Species
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 Lists of
Endangered and Threatened Wildlife
and Plants. A species may be
determined to be an endangered or
threatened species due to one or more
of the five factors described in section
4(a)(1) of the Act: (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; and (E) other natural or
manmade factors affecting its continued
existence. In making this finding,
information regarding the status and
threats to the Lower Colorado River
Basin DPS of roundtail chub in relation
to the five factors provided in section
4(a)(1) of the Act is summarized below.
Factor A. The Present or Threatened
Destruction, Modification, or
Curtailment of Its Habitat or Range
Roundtail chub has been eliminated
from much of its historical range
because many formerly occupied areas
are now unsuitable due to dewatering,
impoundment, channelization, and
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channel changes caused by alteration of
riparian vegetation and watershed
degradation (Miller 1961, pp. 367–371;
Miller 1972, pp. 240, 242; Deacon et al.
1979, pp. 32, 34; Bestgen and Propst
1989, p. 409; Girmendonk and Young
1997, p. 16–44; Bezzerides and Bestgen
2002, pp. 6–9, 24–33; Voeltz 2002, pp.
87–89). In addition, areas where
roundtail chub still occurs have been
significantly altered or are currently
being altered by the same and additional
factors, including mining, improper
livestock grazing, wood cutting,
recreation, urban and suburban
development, groundwater pumping,
dewatering, dams and dam operation,
contaminants, and other human actions
(Minckley 1973, p. 101; Minckley 1985,
pp. 12–15, 65–67; Bestgen and Propst
1989, p. 409; Bezzerides and Bestgen
2002, pp. 24–33; Tellman et al. 1997,
pp. 159–170; Voeltz 2002, pp. 87–89;
McKinnon 2006a, 2006b, 2006c, 2006d,
2006e). These activities and their effects
on the roundtail chub are discussed in
further detail below. It is important to
recognize that in most areas where
roundtail chub historically occurred or
currently occur, two or more threats
may be acting in combination in their
influence on the roundtail chub or on
suitability of habitat to support the
species (Voeltz 2002, pp. 23–81;
Cantrell 2009, p. 15).
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The modification and destruction of
aquatic and riparian communities in the
post-settlement arid southwestern
United States from anthropogenic
(human-caused) land uses is well
documented (Miller 1961, pp. 367–371;
Sullivan and Richardson 1993, pp. 35–
42; Girmendonk and Young 1997, pp.
45–52; Tellman et al. 1997; Webb and
Leake 2005, pp. 305–310; Ouren et al.
2007, pp. 16–22). Significant loss of
habitat and species range has also been
well documented (Miller 1961, p. 365;
Minckley 1985, pp. 4–15; Minckley and
Deacon 1991, pp. 7–18), and has been
reported specifically for the roundtail
chub in the lower Colorado River basin
(Voeltz 2002). An estimated one-third of
Arizona’s pre-settlement wetlands have
dried or have been rendered
ecologically dysfunctional (Yuhas
1996). Although many of these habitat
changes, and the greatest loss and
degradation of riparian and aquatic
communities in Arizona, occurred
during the period from 1850 to 1940,
(Miller 1961, pp. 365–371; Minckley
1985, pp. 4–15; Webb and Leake 2005,
pp. 305–310), many of these land
activities continue today and are
discussed in detail below.
Dams, Diversions, and Groundwater
Withdrawal
Major dams have been constructed
throughout the historical and current
range of the roundtail chub in the lower
Colorado River basin, including four
dams on the Gila River, four on the Salt
River, and two on the Verde River, and
have been a substantial cause in the
decline of the species (Minckley 1985,
pp. 12–14; Tellman et al. 1997, pp. 159–
170; Voeltz 2002, pp. 19–22, 44–45).
Although roundtail chubs survive,
reproduce, and can even be cultured in
small ponds, they do not appear to be
able to persist in reservoirs. Much of the
lower Salt River and portions of the
lower Verde River are now reservoirs
where roundtail chub formerly occurred
(Voeltz 2002, pp. 20, 84–85). In addition
to the loss of flowing river habitats
through inundation, dams also modify
sediment dynamics, timing and
magnitude of downstream flow, and
temperature characteristics of habitats
(Gloss et al. 2005, pp. 17–32, 69–85).
Such changes can negatively affect the
distribution and survival of warm-water
adapted native fishes like roundtail
chub. Tailwaters of large dams are often
too cold for successful reproduction by
native warmwater fishes. Cooler water
temperatures can also reduce the growth
rates and survival of embryos and
juvenile warm-water fish. Larvae grow
more slowly, which increases their risk
of predation and decreases
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accumulation of energetic reserves
needed for overwinter survival. Cold
water temperatures may slow growth
and reduce reproductive success (Marsh
1985, p. 129; Valdez and Ryel 1994, pp.
4–16; Muth et al. 2000, pp. 5–1–5–39).
Reservoirs also capture sediment and
discharge sediment-poor water
downstream that alters channel
characteristics (Collier et al. 1996, pp.
63–85; Gloss et al. 2005, pp. 17–32;
Wright et al. 2008, p. 4). Alteration of
the magnitude and timing of flow and
capture of sediment in reservoirs can
increase water clarity and channel scour
downstream from the dam (Collier et al.
1996, pp. 63–85). Changes in discharge
timing and magnitude may shift
environmental cues needed by fish for
proper timing of migration and
spawning, thereby preventing successful
reproduction (Muth et al. 2000, pp. 5–
1–5–39). Dams also prevent upstream,
and to a lesser degree downstream,
movement of all age classes to historical
spawning, rearing, and overwintering
habitat (Martinez et al. 1994, pp. 227–
239; Schuman 1995, pp. 249–261).
Within the range of roundtail chub in
the lower Colorado River basin, water
for human uses is supplied by reservoirs
created by dams, surface water
diversions, and groundwater pumping.
The hydrologic connection between
groundwater and surface flow of
intermittent and perennial streams is
becoming better understood.
Groundwater pumping creates a cone of
depression within the affected aquifer
that slowly radiates outward from the
well site. When the cone of depression
intersects the hyporheic zone of a
stream (the active transition zone
between surface water and groundwater
that contributes water to the stream
itself), the surface water flow may
decrease. Continued groundwater
pumping can draw down the aquifer
sufficiently to create a water-level
gradient away from the stream and
floodplain (Webb and Leake 2005, p.
309). Finally, complete disconnection of
the aquifer and the stream results in
dewatering of the stream (Webb and
Leake 2005, p. 309).
Roundtail chub has been eliminated
from much of its historical range
because many formerly occupied areas
are now unsuitable due to dewatering
(Miller 1961, pp. 367–371; Miller 1972,
pp. 240, 242; Deacon et al. 1979, pp. 32,
34; Bestgen and Propst 1989, p. 409;
Girmendonk and Young 1997, pp. 16–
44; Bezzerides and Bestgen 2002, pp. 6–
9, 24–33; Voeltz 2002, pp. 87–89).
Dams, diversions, and groundwater
pumping have effectively eliminated
much of the riverine habitat in Arizona
that roundtail chub once occupied
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simply by eliminating downstream flow
and drying much of the historical river
courses (Tellman et al. 1997, pp. 164,
169; Voeltz 2002, pp. 19–22, 44–45). In
1904, Chamberlin noted that a primary
cause of fish extinctions in the lower
Colorado River basin was irrigation
operations including water use,
preclusion of migration due to dams,
and destruction of fish in ditches
(Minckley 1999, p. 215). Groundwater
pumping and water diversions continue
to pose a significant threat to the
continued existence of the roundtail
chub by reducing the quantity and
quality of habitat (Girmendonk and
Young 1997, p. 56), and by altering
streamflow and reducing the frequency
and magnitude of floods. Diversions
also impact fish populations by creating
barriers to fish movement and by
entraining drifting larvae and fish into
irrigation canals where they may later
perish (Martinez et al. 1994, pp. 227–
239). Chamberlin found that all of the
flow of the San Pedro River was
diverted at two dams near Fairbanks in
1904 (Minckley 1999, pp. 200–201).
Reaches of the Verde River near Tapco
and the urban areas in the Verde Valley
contain numerous, significant diversion
dams, and dead fishes have been
reported in surrounding pastures
following irrigation (Girmendonk and
Young 1997, p. 56). Roundtail chubs are
also diverted from the lower Salt River
into canals in the Phoenix area, where
they likely perish as a result of annual
dewatering for canal maintenance,
although some fish are salvaged and
returned to the Salt River.
The Service found that, in lotic
systems (flowing water), roundtail chub
habitat is essentially eliminated when
flow consistently drops below 10 cubic
feet per second (0.3 cubic meters per
second) (Service 1989, pp. 32–33). In
the Verde River, the lowered water level
during the summer irrigation season
alters physical characteristics of the
river, changing stream width and depth
(Girmendonk and Young 1997, p. 55–
56), with much of the stream in the
summer dry season reduced to isolated
pools, especially in the urbanized Verde
Valley area. 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, p. 13). Water
withdrawal alters stream flow regime, in
part by reducing flooding (Brouder
2001, p. 302; Freeman 2005, p. 1).
Brouder (2001, p. 302) hypothesized
that periodic flooding in the Verde River
is needed to maintain roundtail chub
habitat, and further that reductions in
periodic flooding due to continued
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water withdrawal and extended drought
could lead to roundtail chub
recruitment failure and significant
population declines.
To accommodate the needs of rapidly
growing rural and urban populations
(see the ‘‘Urban and Rural
Development’’ section), surface water is
commonly diverted to serve many
industrial and municipal uses. These
water diversions have dewatered large
reaches of once perennial or
intermittent streams, adversely affecting
roundtail chub habitat throughout its
range in Arizona and New Mexico.
Many tributaries of the Verde River are
permanently or seasonally dewatered by
water diversions for agriculture
(Paradzick et al. 2006, pp. 104–110).
Water withdrawal (dams, diversions,
and groundwater pumping) is a threat to
most extant populations of roundtail
chub in the lower Colorado River basin
(Bestgen and Propst 1989, p. 409;
Girmendonk and Young 1997, p. 56;
Propst 1999, p. 25; Voeltz 2002, pp. 23–
81; Cantrell 2009, p. 15).
Increased urbanization and
population growth results in an increase
in the demand for water and, therefore,
water development projects. Municipal
water use in central Arizona has
increased by 39 percent in the last 8
years (American Rivers 2006, pp. 2–3).
Areas of the Verde River basin continue
to experience explosive population
growth and concomitant demand for
water. Traditionally rural portions of
Arizona are also predicted to experience
significant growth. The populations of
developing cities and towns of the
Verde watershed are expected to more
than double in the next 50 years, which
may pose exceptional threats to riparian
and aquatic communities of the Verde
Valley (Girmendonk and Young 1993, p.
47; American Rivers 2006; Paradzick et
al. 2006, p. 89). Communities in
Yavapai and Gila counties such as the
Prescott-Chino Valley and the City of
Payson have seen rapid population
growth in recent years. For example, the
population in the town of Chino Valley,
at the headwaters of the Verde River,
grew by 22 percent between 2000 and
2004; Gila County, which includes
reaches of Tonto Creek and the Salt,
White, and Black Rivers, grew by 20
percent between 2000 and 2003 (U.S.
Census Bureau 2005). Voeltz (2002, p.
35) also considered groundwater
pumping from new development a
serious threat for all streams of the
Burro Creek drainage in the Bill
Williams River basin.
In the Verde River basin, water
demands of increasing population
density and associated development
have reduced the flow of the Verde
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River, and seem likely to continue to do
so. A number of researchers have
reported that groundwater in the Big
Chino aquifer is connected to the Verde
River and that groundwater pumping of
this aquifer affects stream flow in the
mainstem Verde River (Wirt and
Hjalmarson 2000, pp. 44–47; Ford 2002,
p. 1; Woodhouse et al. 2002, pp. 1–4).
The relationship between groundwater
pumping in the lower Big Chino aquifer
and Verde River flow has been apparent
since at least the early 1960s when a
surge of pumping due to new
development caused Verde River flows
to drop significantly (Wirt and
Hjalmarson 2000, p. 27). The Big Chino
aquifer is estimated to supply
approximately 80 percent of the base
flow of the Upper Verde River (Wirt and
Hjalmarson 2000, p. 44, Wirt et al. 2004,
p. G7; Blasch et al. 2006, updated 2007,
pp. 1–2). Woodhouse et al. (2004, pp.
1–4) also reported that numerous
groundwater wells throughout the upper
Verde River watershed have reduced the
water table of the Verde River
(Woodhouse et al. 2002, pp. 1–4). A
proposed water project in the area, the
Big Chino Water Ranch Project, will
include infrastructure to pump
groundwater in the Chino Valley and
pipe it to nearby communities. It will
include a 30 mi (48 km), 36 in. (91 cm)
diameter pipeline that will deliver up to
2.8 billion gallons (gal) (12,400 acre-feet
(ac-ft)) of groundwater annually from
the Big Chino sub-basin aquifer to the
rapidly growing area of Prescott Valley
for municipal use (McKinnon 2006c;
Davis 2007, pp. 1–2). This potential
reduction or loss of baseflow in the
Verde River could seasonally dry up
large reaches of the stream.
Roundtail chub habitat in Clear Creek
and Chevelon Creek in the Little
Colorado River watershed appears
severely threatened by dewatering.
Recent studies and assessments of the
Little Colorado River watershed and its
underlying groundwater resources
indicate that these water resources are
under increasing pressure from
development (Bills et al. 2005). The
North Central Arizona Water Supply
Study Report of Findings (U.S. Bureau
of Reclamation 2006) predicts that by
the year 2050, the human demand for
water will not be met in north-central
Arizona. Plans are underway to
determine how additional water
resources can be developed to provide
for this unmet demand. Protecting water
resources for environmental needs is
included in these plans. However, it is
likely that, with the need for additional
demand and use of water for human
uses, there will be additional stress on
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32361
these aquatic ecosystems. In addition,
there is high potential that extended
drought, perhaps exacerbated through
global climate change (see the ‘‘Climate
Change’’ section below), will further
stress water resources. Two hydrologic
models developed to evaluate the
impacts of additional pumping on
groundwater in the C-aquifer in Arizona
support these findings. The C-aquifer is
located on the Colorado Plateau of
northeastern Arizona, western New
Mexico, and southern Colorado and is
the aquifer that underlies the lower
Colorado River Basin. Two groundwater
models, one developed by the U.S.
Geological Survey (Leake et al. 2005),
and a second full-flow groundwater
model developed to evaluate cumulative
effects to surface water flow
(Papadopulos and Associates 2005),
have been developed for the area
encompassing the C-aquifer. Both
models predicted depletion in baseflow
from current and proposed groundwater
withdrawals in lower Chevelon and
Clear Creeks over the next 50 to 100
years. The flow model (Papadopulos
and Associates 2005) predicted that,
based on current regional pumping, the
base flow of Lower Chevelon Creek
would be zero in 60 years.
Water use from rapidly growing
communities and agricultural and
mining interests have altered flows or
dewatered significant reaches during the
spring and summer months in some of
the Verde River’s larger, formerly
perennial tributaries such as Wet Beaver
Creek, West Clear Creek, and the East
Verde River (Girmendonk and Young
1993, pp. 45–47; Sullivan and
Richardson 1993, pp. 38–39; Paradzick
et al. 2006, pp. 104–110). The upper
Gila River is also threatened by water
diversions and water allocations. In
New Mexico, a water settlement in 2004
allows New Mexico the right to
withhold 4.5 billion gal (13,800 ac-ft) of
surface water every year from the Gila
and San Francisco Rivers (McKinnon
2006d). Project details are still under
development, so the impact of this
project on aquatic resources cannot yet
be evaluated.
The Arizona Department of Water
Resources manages water supplies in
Arizona and has established five Active
Management Areas across the State
(Arizona Department of Water
Resources 2006). An Active
Management Area is established by the
Arizona Department of Water Resources
when an area’s water demand has
exceeded the groundwater supply and
an overdraft has occurred. In these
areas, groundwater use has exceeded the
rate that precipitation can recharge the
aquifer. Geographically, all five Active
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Management Areas overlap the
historical distribution of the roundtail
chub in Arizona. The declaration of
these Active Management Areas further
illustrates the current and future threats
to aquatic habitat in these areas and is
a cause of concern for the long-term
maintenance of historical and occupied
roundtail chub habitat. Such overdrafts
reduce surface water flow of streams
that are hydrologically connected to the
aquifer under stress, and this stress can
be further exacerbated by the surface
water diversions.
Livestock Grazing
Historical accounts of livestock
grazing and its effects in Arizona are
consistent: widespread overgrazing
throughout the State in the mid- to late1880s denuded rangelands and so
altered watersheds that the landscape
was changed forever. In fact, in 1906,
F.M. Chamberlain conjectured that the
alteration of landscapes was so
profound that it had actually resulted in
climate change to a more arid climate in
the region (as cited in Minckley 1999).
Similarly, Croxen (1926) describes
changes to the Tonto National Forest
resulting from poorly managed livestock
grazing as largely running their course
by the late 1880s. Between 1880 and
1890, the widespread improper grazing
regimes that had denuded the landscape
for 10 to 20 years or so throughout the
State was followed by severe flooding.
The end result was a rapid transition for
many aquatic habitats from permanent,
meandering streams to intermittent
‘‘flashy’’ arroyos (intermittent streams
with higher peak flows and lower base
flows) (Minckley and Hendrickson
1984, pp. 131–132; Cheney et al. 1990,
pp. 5, 10).
Poorly managed livestock grazing has
damaged approximately 80 percent of
stream, cienega (marsh), and riparian
ecosystems in the western United States
(Kauffman and Krueger 1984, pp. 433–
435; Weltz and Wood 1986, pp. 367–
368; Waters 1995, pp. 22–24; Pearce et
al. 1998, p. 307; Belsky et al. 1999, p.
1) and severely altered many of the
habitats formerly and currently
occupied by roundtail chub. Livestock
grazing today is much more strictly
managed by Federal agencies and Tribes
because the effects of grazing and
mismanagement are now better
understood and have been well
documented. For example, Stromberg
and Chew (2002, p. 198) and Trimble
and Mendel (1995, p. 243) discuss the
propensity for poorly managed cattle to
remain within or adjacent to riparian
communities, a behavior that is more
pronounced in arid regions (Trimble
and Mendel 1995, p. 243). In one
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rangeland study, it was concluded that
81 percent of the vegetation that was
consumed, trampled, or otherwise
removed was from a riparian area,
which amounted to only 2 percent of
the total grazing space (Trimble and
Mendel 1995, p. 243). Additionally,
grazing rates can be 5 to 30 times higher
in riparian areas (Trimble and Mendel
1995, p. 244). But as a direct result of
this research, management agencies now
exclude livestock grazing from many
riparian areas and streams, or only
permit light and seasonal grazing in
these areas. We summarize here the
effects of livestock grazing, but it is
important to note that these effects only
become tangible if livestock grazing is
poorly managed. If properly managed,
there is some evidence that affects to
wildlife habitat can be positive. In this
respect, livestock grazing is largely a
threat of the past, and if properly
managed, is not likely a threat.
Although more research is needed,
livestock grazing strategies can be
developed that are compatible and even
complementary with fisheries
management (Platts 1989, p. 103; Vavra
2005, p. 128). The American Fisheries
Society Policy Statement on livestock
grazing concludes that ‘‘it is our strong
contention that when properly
implemented and supervised, grazing
could become an important
management tool benefiting fish and
wildlife riparian habitats’’ (American
Fisheries Society 2009).
Livestock grazing occurs throughout
the range of roundtail chub in the lower
Colorado River basin in all drainages in
which the species occurs (Tellman et al.
1997, p. 167; Propst 1999, p. 25; Voeltz
2002, pp. 23–88), and has resulted in
the degradation of roundtail chub
habitat from a number of mechanisms.
Livestock directly affect roundtail chub
habitat through removal of riparian
vegetation (Clary and Webster 1989, p.
1; Clary and Medin 1990, p. 1; Schulz
and Leininger 1990, p. 295; Armour et
al. 1991, pp. 8–10; Fleishner 1994, pp.
630–631), which can result in reduced
bank stability, fewer pools, and higher
water temperatures (Kauffman and
Krueger 1984, p. 432; Minckley and
Rinne 1985, p. 150; Schulz and
Leininger 1990, p. 295; Fleishner 1994,
pp. 630–631; Belsky et al. 1999, pp. 8–
12). Livestock grazing can also cause
increased sediment in the stream
channel, due to streambank trampling
and riparian vegetation loss (Weltz and
Wood 1986, pp. 367–368; Waters 1995,
pp. 22–24; Pearce et al. 1998, p. 307).
Livestock physically alter streambanks
through trampling and shearing, leading
to bank erosion (Trimble and Mendel
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1995, p. 244; Clary and Webster 1989,
pp. 7–8). In combination, loss of
riparian vegetation and bank erosion
can alter channel morphology,
including increased erosion and
deposition, downcutting, and an
increased width/depth ratio, all of
which can lead to a loss of pool habitats
and loss of shallow side and backwater
habitats (Trimble and Mendel 1995, pp.
243–250; Belsky et al. 1999, pp. 1–2).
Pool habitats are required by the
roundtail chub, and shallow side and
backwater habitats are used by larval
chubs for sheltering from larger bodied
predators and for feeding (Minckley
1973, p. 100; Brouder et al. 2000, pp. 6–
7; Minckley and DeMarais 2000, p. 255).
Although livestock grazing is unlikely
to be a threat if properly managed,
physical developments necessary to
support livestock grazing can also have
direct effects on roundtail chub. Water
sources are essential to livestock
operations, and numerous stock tanks,
stream diversions, and various types of
groundwater pumps are utilized to
provide water for livestock (Valentine
1989, pp. 413–431). This diverts water
from natural surface waters, including
streams supporting roundtail chub (see
‘‘Dams, Diversions, and Groundwater
Withdrawal’’ section above). In addition
to livestock developments, thousands of
miles of fencing are needed to partition
cattle into pastures or rotation-type
grazing systems (Valentine 1989, pp.
435–449). Maintaining this
infrastructure requires a substantial
network of roads. Road use and
maintenance have been a major factor in
altering the morphology and habitat of
streams in the Southwest (see ‘‘Road
Construction, Use, and Maintenance’’
section below).
Livestock can indirectly impact
aquatic and riparian habitats at a
watershed level though soil compaction,
altered soil chemistry, and reductions in
upland vegetation cover; these changes
lead to an increased severity of floods
and sediment loading, lower water
tables, and altered channel morphology
(Rich and Reynolds 1963, p. 222;
Orodho et al. 1990, p. 9; Schlesinger et
al. 1990, p. 1043; Belsky et al. 1999, p.
1). One consequence of these changes in
watershed function is a reduction in the
quantity and quality of pool habitat.
Lowered water tables result in the direct
loss of pool habitats, simply because
water is not available to form pools.
Increased erosion and sedimentation
results in filling of pools with
sediments. Channel incision and
increased flood severity eliminate pools
through bed scour, and reduce habitat
complexity by creating shallow, uniform
streambeds (see Trimble and Mendel
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1995, pp. 245–251; Belsky et al. 1999,
pp. 25–35). Much of Arizona’s rivers
and streams were modified by livestock
grazing in this way by the mid 1900s
(Miller 1961, pp. 394–395; Minckley
1999, p. 215), and the effects to aquatic
habitat from that historical modification
remain today.
Livestock use has been shown to alter
the composition and community
structure of the aquatic fauna (regional
animal life), which can also indirectly
impact roundtail chub by reducing the
quantity and quality of food sources.
Altered stream channel characteristics,
sediment deposition, changes in
substrate size, and nutrient cycle
changes are all potential effects of
livestock grazing that can alter aquatic
invertebrate communities (Li et al. 1994,
pp. 638–639; Hoorman and McCutcheon
2005, p. 3), resulting in changes to the
food base for aquatic vertebrates,
particularly fish. Few detailed studies of
changes in aquatic faunal communities
have been completed on streams in the
range of the roundtail chub, but given
the widespread occurrence of ongoing
and historical livestock grazing, changes
in aquatic faunal community has likely
occurred in many streams within
historical range of roundtail chub.
Livestock grazing results in loss of
aquatic habitat complexity, thus
reducing diversity of habitat types
available and altering fish communities
(Li et al. 1987, pp. 627, 638–639). In the
arid west, loss of habitat complexity has
been a major contributing factor in
declines of native fishes and
amphibians and in the displacement of
native fish species by nonnative species
(Bestgen and Propst 1986, p. 209;
Minckley and Rinne 1991, pp. 2–5;
Baltz and Moyle 1993, p. 246; Lawler et
al. 1999, p. 621). Livestock grazing has
also contributed significantly to the
introduction and spread of nonnative
aquatic species through the proliferation
of stock tanks (manmade ponds that are
water sources for livestock) which serve
as created habitat for nonnative species
(Rosen et al. 2001, p. 24; Hedwall and
Sponholtz 2005, pp. 1–5; Service 2008,
pp. 46–51). The spread of nonnative
species is a threat to roundtail chub
because these nonnative species prey on
and compete with roundtail chub (see
‘‘Nonnative Species’’ section below for
more discussion).
Another direct effect of livestock
grazing in intermittent aquatic habitats
is the potential for livestock to drink
occupied roundtail chub habitat dry
under certain conditions, completely
eliminating all habitat and killing any
roundtail chub present. Vallentine
(1989, pp. 413–431) states that cattle
need an average of 12 to 15 gal (45 to
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57 liters (L)) of water per day per
animal, and that this varies seasonally
because of the moisture content of
forage, ambient temperature and
humidity, and other factors. Griffith
(1999, p. 1) states that at 10 °C (50 °F),
a cow may consume about 5 to 7 gal (19
to 26 L) per day, but the amount
increases by 0.4 gal (1.5 L) per day for
every one-degree increase in air
temperature; thus at 35 °C (95 °F) the
same cow will drink an average of 24 gal
(91 L) per day. Roundtail chub can be
limited to small isolated pool habitats
during the driest times of the year that
can be as little as several hundred gal
(1–2000 L) in volume, and have flow so
low that inflow is essentially equal to or
less than evaporation; several cows
could completely dry such habitats in a
matter of days, especially in times of
drought. Gila chub, a related species,
and its habitat, is believed to have been
eliminated in this manner from portions
of Indian Creek in 2002–2003 (Service
2006, p. 10).
Livestock grazing also contributed to
shrub invasion of grasslands (Brown
and Archer 1999, p. 2385). Shrub
invasions decrease biodiversity and
create ecosystem instability in desert
ecosystems (Baez and Collins 2008).
Shrub invasion also can lead to a greater
amount of water loss through plants,
which contributes to desertification
(Knapp et al. 2008, p. 621). Fire regimes
are also altered by shrub invasion
(Richburg et al. 2001, p. 104), and
altered fire regimes pose a threat to
roundtail chub due to the effects of
wildfire on watersheds and direct
effects of ash and sediment flows
following wildfires (see ‘‘High-Intensity
Wildfires’’ section below).
All extant populations of roundtail
chub are subject to some level of
livestock grazing in the watershed, but
specific problems associated with
livestock grazing have only been noted
in four streams (Chevelon, East Clear,
Burro, and Salome Creeks) (Voeltz 2002;
Cantrell 2009, p. 15). In Chevelon Creek,
Arizona Department of Environmental
Quality water quality standards for
sediment and turbidity (muddiness of
water) were not met due to grazing and
high channel erosion, habitat
modification, and unsatisfactory
watershed condition for the watershed
(Voeltz 2002, p. 27). In the Verde River,
Girmendonk and Young (1997, p. 53)
noted cattle grazing had a major impact
on both upland and aquatic
communities due to trampled banks and
heavily grazed vegetation from Sullivan
Lake downstream to Cottonwood.
However, we note that in most streams
currently occupied by roundtail chub,
grazing has been removed from the
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riparian area. For example, livestock
grazing has since been removed from
that portion of the Verde River
discussed by Girmendonk and Young
(1997).
The above discussion illustrates that
poorly managed livestock grazing can
adversely affect roundtail chub in
several ways, from direct loss due to
livestock water and vegetation
consumption and trampling, to indirect
habitat alteration from changes in the
watershed. In general, properly
managed livestock grazing utilizes restrotation grazing systems that exclude
riparian areas or limit their use to the
winter season, and utilize monitoring
systems to ensure that use of uplands
and riparian areas are not overgrazed.
When livestock grazing is well managed
in this manner it is not likely a threat
to the roundtail chub. The capability
exists to create livestock grazing
strategies that are compatible and even
complementary to maintaining fisheries
habitat, although more research is
needed in this regard (Platts 1989, p.
103; Vavra 2005, p. 128).
Urban and Rural Development
Urban and rural development are
considered a threat in every stream
currently occupied by roundtail chub
(Cantrell 2009, p. 18). Development can
affect roundtail chub and its habitat
through direct alteration of streambanks
and floodplains from construction of
homes and businesses, as well as from
numerous related impacts. Tellman et
al. (1997, pp. 92–93) listed the following
impacts to rivers in Arizona from urban
and rural development: increased use of
floodplain for homes and businesses,
sand and gravel mining in the
floodplain for construction materials,
pollution from trash and wastewater in
river bed, depletion of water supplies,
increased land covered by impervious
surfaces with greater surface runoff and
less infiltration, building of flood
control structures, and increased
recreational impacts. On a broader scale,
development alters the watershed with
consequent changes in the hydrology,
sediment regimes, and pollution input
(Leopold 1997, pp. 97–102; Horak 1989,
p. 42; Medina 1990, p. 351; Reid 1993,
pp. 48–51; Waters 1995, pp. 42–44;
Wheeler et al. 2005, p. 141).
Development changes watersheds
from land surfaces where precipitation
can infiltrate the soil and reach a stream
slowly as subsurface flow, to one with
impervious surfaces such as rooftops,
asphalt, and compacted soils (Schueler
1994, p. 100; 1995, p. 233; Wheeler et
al. 2005, p. 151). These impervious
surfaces capture precipitation and route
it quickly and directly into gutters,
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storm drains, overland flow, and
streams (Hollis 1975, p. 431; Wheeler et
al. 2005, p. 151). Similarly,
precipitation falling on impervious
surfaces without direct hydraulic
connections to streams may reach
streams quickly as overland flow
(Horton 1945, p. 275; Leopold 1973, p.
1845; Wheeler et al. 2005, p. 151). Thus,
urbanization fundamentally alters the
delivery of water to streams
(Environmental Protection Agency 2008,
p. 1). These changes in precipitation
delivery alter stream flow regimes. Peak
flow volume from precipitation events
increases (Hollis 1975, p. 431; Neller
1988, p. 1; Booth 1990, pp. 407–417;
Clark and Wilcock 2000, p. 1763; Rose
and Peters 2001, p. 246; Wheeler et al.
2005, p. 151). These changes increase
the frequency and magnitude of floods
(Hollis 1975, p. 431; Wheeler et al. 2005,
p. 151), which cause a stream to
increase its channel capacity by eroding
its banks, downcutting its channel, or
both (Hammer 1972, p. 1530; Leopold
1973, p. 1845; Booth 1990, p. 1752;
Pizzuto et al. 2000, p. 79; Brown and
Caraco 2001, pp. 16–19; Wheeler et al.
2005, p. 151). Because natural surfaces
in a watershed transmit water slowly to
the stream as subsurface flow, base flow
in a stream is often from subsurface flow
and groundwater that steadily
contributes flow between precipitation
events. The impervious surfaces caused
by development alter this process,
preventing precipitation from
infiltrating, and resulting in a reduction
in base flow of the stream (Simmons
and Reynolds 1982, p. 1752; Wang et al.
2001, p. 255; 2003, p. 825; Wheeler et
al. 2005, p. 151). Development within
and adjacent to riparian areas has
proven to be a significant threat to
riparian and aquatic biological
communities (Medina 1990, p. 351),
with even low levels of development
causing adverse impacts within a
watershed (Wheeler et al. 2005, p. 142).
Development can alter the nature of
stream flow dramatically, changing
streams from perennial to ephemeral,
which can have direct consequences to
stream fauna (Medina 1990, pp. 358–
359). Medina (1990, pp. 358–359) found
that development reduced vegetation in
streams and changed flow regimes,
which resulted in a decrease in
abundance of fish.
Development in and near stream
courses usually results in removal of
riparian vegetation, which leads to a
number of changes to streams (Wheeler
et al. 2005, p. 151). Riparian vegetation
stabilizes streambanks and reduces bank
erosion (Beeson and Doyle 1995, p. 983;
Wynn and Mostaghimi 2006, p. 400),
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and helps moderate urban stream
temperatures (LeBlanc et al. 1997, p.
445). Because riparian vegetation
contributes leaves, wood, organic
debris, and terrestrial invertebrates to
streams, vegetation removal can often
drastically alter food webs in streams
(Vannote et al. 1980, p. 130; Hawkins
and Sedell 1981, p. 387; Reid 1993, p.
74). Also, large woody debris can be an
important component of stream
channels because the debris stabilizes
stream banks (Keller and Swanson 1979,
p. 361), creates pools (Keller and
Swanson 1979, p. 361; Rinne and
Minckley 1985, p. 150), and provides
habitat for macroinvertebrates (Benke et
al. 1985, pp. 8–13; Rinne and Minckley
1985, p. 150) and fishes (Angermeier
and Karr 1984, p. 716; Flebbe and
Dolloff 1995, p. 579). Riparian
vegetation also moderates stream
temperatures (LeBlanc et al. 1997, p.
445). In small and medium-sized
streams, riparian vegetation shades and
cools the stream; loss of riparian
vegetation contributes to warming of the
stream (Barton et al. 1985, p. 365;
LeBlanc et al. 1997, p. 445). Wang et al.
(2003, p. 825) found that the maximum
daily water temperature of streams in
urbanized settings in Wisconsin and
Minnesota increased by 0.25 °C (0.5 °F)
with every 1 percent increase in the
impervious area of the watershed.
Urban streams enlarge their channels
by eroding their banks; this erosion,
together with runoff from urban
construction activities, adds fine
sediment to the stream (Waters 1995, p.
43; Trimble 1997, p. 1442; Wheeler et
al. 2005, p. 151), increasing turbidity,
which can alter stream habitat
productivity, adversely affect the food
base for fish, eliminate rearing habitats,
and fill in pool habitat (Waters 1995, p.
43). Because urbanization typically
results in loss of riparian vegetation as
areas near streams are cleared, riparian
areas can lose the natural ability to
absorb and filter out metals, fine
sediment, and nutrients from overland
runoff (McNaught et al. 2003, p. 7).
Development can affect water quality
in a number of ways. Urban runoff
contains a variety of chemical pollutants
including petroleum, metals, and
nutrients from a variety of sources such
as automobiles and building materials
(Wheeler et al. 2005, p. 153). Some
pollutants contain the nutrients nitrogen
and phosphorus, which can cause a
body of water to become nutrientenriched and stimulate the growth of
aquatic plant life resulting in the
depletion of dissolved oxygen. This can
adversely affect fish by reducing
dissolved oxygen to lethal levels
(Hassler 1947, pp. 383–384; Cantrell
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2009, p. 15). Development also leads to
increases in the number of dumps and
landfills that leach contaminants into
ground and surface water, reducing
water quality and thereby degrading
roundtail chub habitat. Similarly,
wastewater treatment plants that
accompany development also can
contaminate ground and surface water
(Winter et al. 1998, p. 66).
Pharmaceuticals and personal care
products also may contain hormones,
which are present in wastewater, and
can have significant adverse effects to
fishes, particularly fish reproduction
(Kime 1995, p. 52; Rosen et al. 2007, pp.
1–4). The use of pesticides is also a
source of water quality contamination
from agricultural and residential use,
which can have lethal and sublethal
effects to fish (Ongley 1996). The use of
pesticides occurs adjacent to 9
populations of roundtail chub in
Arizona (Cantrell 2009, p. 12).
The physical and chemical alterations
of stream systems due to urbanization
cause significant changes to the stream
biological community (Wheeler et al.
2005, p. 153). Urbanized streams have
fewer numbers and species of
macroinvertebrates (Richards and Host
1994, p. 195; Kemp and Spotila 1997, p.
55; Kennen 1998, p. 3), and exhibit
reduced biological health (Kennen 1998,
p. 3). Urban streams also have lower
overall abundance and diversity of
fishes (Tramer and Rogers 1973, p. 366;
Scott et al. 1986, p. 555; Medina 1990,
p. 351; Weaver and Garman 1994, p.
162; Wang et al. 2000, p. 255; 2003, p.
825). Little is known about how urban
development and the corresponding
physical and chemical changes in
streams result in changes in the stream
ecosystem, although the physical
changes appear more important in this
process than the chemical changes
(Wheeler et al. 2005, p. 154).
The net result of urbanization for
roundtail chub is a decrease in habitat
suitability, most significantly through a
reduction in stream flow, although also
through an increase in the probability of
the presence of nonnative aquatic
species that prey on and compete with
roundtail chub (see ‘‘Nonnative
Species’’ section below). As described
above, development typically involves
increased water use in the form of
diversions of water from both surface
flows and connected groundwater
(Glennon 1995, pp. 133–139). The
physical changes associated with
development also result in a more
‘‘flashy’’ system, as described above,
where runoff from precipitation rapidly
exits the watershed, increasing flood
flows, and decreasing base flow. These
hydrologic changes can lead to streams
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changing from perennial to intermittent,
and result in a corresponding decrease
in fish abundance (Medina 1990, p.
351).
The effects of urban and rural
development are expected to increase as
human populations increase.
Development has continually been
increasing in the southwestern United
States. Arizona increased its population
by 394 percent from 1960 to 2000, and
is second only to Nevada as the fastest
growing State in terms of human
population (Social Science Data
Analysis Network 2000, p. 1). Growth
rates in Arizona counties with historical
or extant roundtail chub populations are
also significant and increasing:
Maricopa (463 percent); Cochise (214
percent); Yavapai (579 percent); Gila
(199 percent); Graham (238 percent);
Apache (228 percent); Navajo (257
percent); Yuma (346 percent); LaPaz
(142 percent); and Mohave (1,904
percent) (Social Science Data Analysis
Network 2000). Population growth
trends in Arizona are expected to
continue into the future. The Phoenix
metropolitan area, founded in part due
to its location near the junction of the
Salt and Gila Rivers, is a population
center of 3.6 million people. The
Phoenix metropolitan area is the sixth
largest in the United States and is
located in the fastest growing county in
the United States since the 2000 census
(McKinnon 2006a). Traditionally rural
portions of Arizona are also predicted to
see huge increases in human
population. Developing cities and towns
of the Verde watershed are expected to
more than double in the next 50 years,
which, as described above, is expected
to threaten riparian and aquatic
communities of the Verde Valley where
roundtail chubs occur (Girmendonk and
Young 1993, p. 47; American Rivers
2006; Paradzick et al. 2006, p. 89).
Chino Valley, at the headwaters of the
Verde River, grew by 22 percent
between 2000 and 2004. Gila County,
which includes reaches of Tonto Creek
and the Salt, White, and Black Rivers,
grew by 20 percent between 2000 and
2003 (U.S. Census Bureau 2005). In New
Mexico, a water settlement in 2004
allows New Mexico the right to
withhold 4.5 billion gal (13,800 ac-ft) of
surface water every year from the Gila
and San Francisco Rivers (McKinnon
2006d). Project details are still under
development, so the impact of this
project on aquatic resources has not yet
been evaluated; however, the project
represents another potential withdrawal
of water from occupied habitat.
Given the arid nature of the
Southwest, the predictions of further
growth in an already large population
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center, and the adverse impacts to
aquatic habitats that are associated with
development, development will
continue to be a threat to the roundtail
chub. Urban and rural development are
considered a threat in every stream
currently occupied by roundtail chub
(Cantrell 2009, p. 15).
Road Construction, Use, and
Maintenance
Roads are a threat to roundtail chub
and its habitat due to a variety of factors
including fragmentation, modification,
and destruction of habitat; increase in
genetic isolation; facilitation of the
spread of nonnative species via human
vectors; increases in recreational access
and the likelihood of subsequent,
decentralized urbanization; and
contributions of contaminants to aquatic
communities (Burns 1972, p. 1; Barrett
et al. 1992, p. 437; Eaglin and Hubert
1993, p. 884; Warren and Pardew 1998,
p. 637; Waters 1995, p. 42; Jones et al.
2000, pp. 82–84; Angermeier et al. 2004,
pp. 19–24; Wheeler et al. 2005, pp. 145,
148–149).
Construction and maintenance of
roads and highways near riparian areas
can be a source of sediment and
pollutants (Waters 1995, p. 42; Wheeler
et al. 2005, pp. 145, 148–149). Sediment
can adversely affect fish populations by
interfering with respiration; reducing
the effectiveness of fish’s visually-based
hunting behaviors; and filling in
interstitial spaces of the substrate,
which reduces reproduction and
foraging success of fish (Wheeler et al.
2005, p. 145). Excessive sediment also
fills in intermittent pools that roundtail
chub utilize as habitat. Fine sediment
pollution in streams impacted by
highway construction without the use of
sediment control structures was 5 to 12
times greater than control streams
(Wheeler et al. 2005, p. 144). Excessive
sediment can also affect the ability of
roundtail chubs to forage.
Sedimentation can alter the aquatic
macroinvertebrate community, thereby
reducing the food base for roundtail
chubs. Increased turbidity may impede
the ability of roundtail chubs to forage
by reducing underwater visibility
(Barrett et al. 1992, p. 437; Waters 1995,
pp. 173–175).
Contaminants (hydrocarbons such as
petroleum based products, and metals,
including iron, zinc, lead, cadmium,
nickel, copper, and chromium) are
associated with highway construction
and use (Foreman and Alexander 1998,
p. 220; Wheeler et al. 2005, pp. 146–
149). Many of these contaminants are
suspected toxicants to aquatic
organisms. Few studies have addressed
the toxicity of highway runoff, but some
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comparisons of macroinvertebrate
communities above and below highway
crossings indicate that there are
reductions in diversity and pollutionsensitive species below highway
crossings, especially where small
streams receive runoff from large
highway sections (Wheeler et al. 2005,
p. 148). In areas with cold winter
weather conditions, deicing is common
to clear snow and ice from roadways.
Deicing can contribute sodium chloride
and other chemical contaminants to
water ways, reducing water quality,
which can cause fish stress or mortality
(Wheeler et al. 2005, p. 147). Roads also
inevitably contribute to contaminant
spills from vehicle accidents. Most
hazardous chemicals are transported by
trucks, and such spills are common and
can contaminate water bodies and cause
fish kills (Wheeler et al. 2005, pp. 147–
148).
Road construction can also impact
roundtail chub through physical
changes to the stream channel.
Channelization, often a necessary
component of urban road construction,
can have numerous effects on the
natural structure and ecosystem
function of stream systems (Poff et al.
1997, p. 773; Poole 2002, p. 641). As
discussed in the ‘‘Logging, Fuel Wood
Cutting, Mining, and Channelization’’
section, channelization can affect
roundtail 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, p.
507; Simpson et al. 1982, pp. 122–132;
Propst 1999, p. 25; Schmetterling et al.
2001, p. 6).
Roads can restrict the movement of
stream fishes, resulting in populations
becoming more isolated and fragmented.
Culverts, a common feature of road
stream crossings, are a well-known
barrier to fish movement. Culverts
themselves provide poor fish habitat
due to low-bottom complexity and
uniformly high-flow velocities (Slawski
and Ehlinger 1998, p. 676). Fish
movement is inhibited or prevented by
high current velocities and shallow
depths inside culverts, along with
vertical drops commonly associated
with the culvert outflow (U.S.
Department of Transportation 2007, pp.
3–9). Warren and Pardew (1998, p. 637)
found that overall fish movement was
an order of magnitude lower through
culverts than through other crossing
types or natural channels in small
streams. Such barriers can isolate fish
populations, resulting in reduced
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genetic diversity and increased
probability of extinction due to
demographic instability and impeded
recolonization. Fragmentation of
roundtail chub habitat increases the
probability of local extirpation (Fagan et
al. 2002, p. 3250).
By definition, roads create access to
otherwise inaccessible areas or increase
access to previously remote areas. This
increased access results in increased
human visitation, thereby increasing the
frequency and significance of
anthropogenic threats to aquatic
ecosystems and further fragmenting the
landscape. Further, increased access
often leads to increased urban and
agricultural development. Urbanization
is the most significant of these
development activities; it alters a
watershed, such as through building
construction, which changes rural areas
from such uses as farming and grazing
to residential and industrial areas.
Wheeler et al. (2005; pp. 149–150)
concluded that ‘‘new highways clearly
and purposely provide impetus for
urban development’’ although they
noted that few studies, if any, have
specifically documented this. Roads
nonetheless do clearly have a
relationship to urban and rural
development, which can alter physical
and chemical characteristics of streams
due to increases in contaminants and
changes to the watershed that alter
stream flow, as discussed in the ‘‘Urban
and Rural Development’’ section above.
Recreation
As discussed above, population
growth trends are expected to continue
into the future throughout the range of
the roundtail chub in the lower
Colorado River basin, dramatically
increasing human populations.
Expanding population growth leads to
higher demand for recreational
opportunities and recreational use. In
the arid Southwest, the human desire to
recreate in or near water, and the
relative scarcity of such recreational
opportunities, tends to focus impacts on
riparian areas. Recreation-related
impacts to aquatic ecosystems are
particularly evident along stream
reaches of the Salt and Verde River
watersheds near the Phoenix
metropolitan area, which are visibly
degraded by ongoing use. Impacts of
recreation are highly dependent on the
type of activity, with activities such as
hiking having little impact and activities
such as off-highway vehicle (OHV) use
potentially having severe impacts on
aquatic habitats.
An example of a recreation use
impacted area within the existing
distribution of the roundtail chub is the
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Verde Valley. The reach of the Verde
River that winds through the Verde
Valley receives a high amount of
recreational use from people living in
central Arizona (Paradzick et al. 2006,
pp. 107–108). Increased human use
results in trampling of nearshore
vegetation and reduced water quality.
Recreational impacts in Fossil Creek
illustrate that such damage can be quite
severe. Fossil Creek is a tributary of the
Verde River and an extant locality of
roundtail chub. A number of
environmental groups recently sent a
letter to the Coconino National Forest
requesting emergency action to address
the effects of ongoing recreational use in
Fossil Creek. The authors cited
excessive and damaging impacts of
recreational uses on the creek and
riparian habitat, including vehicles
crushing vegetation, proliferation of
social trails, kayak impacts, severe
sanitation deficiencies, and an
exceptional amount of trash (American
Rivers et al. 2007, pp. 1–4). The effects
to roundtail chub from these actions are
unknown, but potentially adverse.
OHV use has grown considerably in
Arizona, and is a recreational use that
can have severe adverse impacts to
natural areas. As of 2007, 385,000 OHVs
were registered in Arizona (a 350
percent increase since 1998) and 1.7
million people (29 percent of the
Arizona’s public) engaged in off-road
activity from 2005–2007. Over half of
OHV users reported that driving off-road
was their primary activity, versus using
the OHV for the purpose of access or
transportation to hunting, fishing, or
hiking. Ouren et al. (2007, pp. 16–22)
provide additional data on the effects of
OHV use on wildlife. OHV trails often
travel through undeveloped habitat and
cross directly through water bodies.
OHV use may also reduce vegetation
cover and plant species diversity,
reducing infiltration rates, increasing
erosion, and reducing habitat
connectivity (Ouren et al. 2007, pp. 6–
7, 11, 16). As discussed above, reducing
vegetative cover and increasing
sedimentation is a result of other land
uses as well, such as livestock grazing
and urbanization, and can have
numerous adverse effects to roundtail
chub. Voeltz (2002) noted specific OHV
use-related problems with recreation in
two streams with known populations of
roundtail chub, the upper Gila River
and Oak Creek. Recreation occurs in
every stream occupied by roundtail
chub in the lower Colorado River basin
(Cantrell 2009, p. 15).
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Logging, Fuel Wood Cutting, Mining,
and Channelization
Logging and mining were more
widespread historically and likely were
responsible for alteration of much of the
roundtail chub’s historical habitat.
Chamberlain in 1904 listed mining as
one of three primary causes of
‘‘extinction’’ of fishes in the lower
Colorado River basin (along with
vegetation removal from grazing, logging
and other activities, and water use)
(Minckley 1999, p. 215). The current
mining of sand, gravel, iron, gold,
copper, or other materials remains a
potential threat to the habitat of
roundtail chub for many of these same
reasons. Drilling for fuels such as oil
and natural gas has very similar effects
(Hartman 2007, p. 1) and is occurring
within the range of the roundtail chub
in Arizona (Cantrell 2009, p. 12). 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 (Arizona
Department of Environmental Quality
1993, pp. 61–63). Sand and gravel
mining removes riparian vegetation and
destabilizes streambanks, resulting in
habitat loss for the roundtail chub
(Brown et al. 1998, p. 979). Voeltz
(2002, pp. 34–35, 42) identified mining
as a significant threat in Boulder, Burro,
and Eagle Creeks due to the release of
toxic effluents into aquatic systems from
mining operations, and water depletion
for use in mining operations, and noted
that contaminants in the form of
acidified flows originating from mining
operations in Cananea, Mexico, have
been documented in the past in the San
Pedro River, a stream in which the
roundtail chub no longer occurs.
Girmendonk and Young (1997, p. 35)
noted that sand and gravel mining on
West Clear Creek may have limited the
suitability of that stream to support
roundtail chub near the mouth of the
Verde River. Mining is a land use in the
basins of 24 out of 31 currently extant
roundtail chub populations (Voeltz
2002; Cantrell 2009).
Logging and fuel wood cutting is
largely a threat of the past (resulting
from previous management practices no
longer in place), although these
activities resulted in profound changes
in many streams of the Southwest
including those in which the roundtail
chub occurs (Minckley and Rinne 1985,
pp. 150–151; Minckley 1999, p. 216).
The alteration of watersheds resulting
from logging is deleterious to fish and
other aquatic life forms (e.g., Burns
1972, p. 1; Eaglin and Hubert 1993, p.
844), largely due to increases in surface
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runoff, sedimentation, and mudslides,
and the destruction of riparian
vegetation (Lewis 1998, p. 55; Jones et
al. 2000, p. 81). All of these effects
negatively impact fish (Burns 1972, p.
15; Eaglin and Hubert 1993, p. 844;
Barrett et al. 1992, p. 437; Warren and
Pardew 1998, p. 637) by lowering water
quality and reducing the quality and
quantity of pools, either by filling them
with sediment, reducing the quantity of
large woody debris necessary to form
pools, or imposing barriers to
movement. Logging is a land use in the
watersheds of 17 of the remaining 31
streams known to contain roundtail
chub populations (Voeltz 2002).
Channelization of streams is also a
major factor in loss of habitat for
roundtail chub. The U.S. Environmental
Protection Agency defines
channelization as: ‘‘any activity that
moves, straightens, shortens, cuts off,
diverts, or fills a stream channel,
whether natural or previously altered.
Such activities include the widening,
narrowing, straightening, or lining of a
stream channel that alters the amount
and speed of the water flowing through
the channel. Examples of channelization
are: lining channels with concrete;
pushing gravel from the stream bed and
placing it along the banks; and placing
streams into culverts’’ (U.S.
Environmental Protection Agency 2005,
p. 1). Channelization has occurred or is
occurring in roundtail chub habitats to
drain marshes and reclaim bottomlands
for agriculture or roads (Hendrickson
and Minckley 1984, p. 131; Propst 1999,
p. 25); to create irrigation diversions; to
control mosquitoes; to reduce
evapotranspiration and speed water
delivery to downstream metropolitan
and agricultural areas (U.S. Soil
Conservation Service 1949, p. 3;
Burkham 1970, p. B1); and as flood
control to protect fields, buildings, or
structures such as bridges (Pearthree
and Baker 1987, p. 49). Channelization
can affect roundtail chub habitat by
reducing its complexity, eliminating
cover, reducing nutrient input,
improving habitat for nonnative species,
changing sediment transport, altering
substrate size (usually from coarse
sediments like gravel and sand to a finer
silt substrate), and reducing the length
of the stream and therefore the amount
of aquatic habitat available (Gorman and
Karr 1978, p. 513; Simpson et al. 1982,
pp. 122–132; Propst 1999, p. 25;
Schmetterling et al. 2001, p. 6; U.S.
Environmental Protection Agency 2005,
pp. 1–4). Moyle (1976, p. 179) compared
channelized and unchannelized
sections of a California stream and
found a two-thirds reduction in the
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biomass of fish and invertebrates in
channelized locations compared to
unchannelized reaches, as well as
differences in fish and
macroinvertebrate (animals lacking a
vertebral column, such as aquatic
insects) species composition.
Channelization may reduce the
recruitment of fishes by eliminating
nursery habitat through the removal of
gradually sloping streambanks, reducing
the extent of nearshore habitats with
low water velocity (Scheidegger and
´
Bain 1995, p. 125; Merigoux and Ponton
1999, p. 177; Meng and Matern 2001, p.
750).
High-Intensity Wildfires
Low-intensity fire has been a natural
disturbance factor in forested
landscapes for centuries, and lowintensity fires were common in
southwestern forests and grasslands
prior to European settlement (Rinne and
Neary 1996, pp. 135–136). Rinne and
Neary (1996, p. 143) discuss the current
effects of fire management policies on
aquatic communities in Madrean Oak
Woodland biotic communities, a
community type that comprises large
portions of some watersheds occupied
by roundtail chub. They concluded that
existing wildfire suppression policies
intended to protect the expanding
number of human structures on forested
public lands have altered the fuel loads
in these ecosystems and increased the
probability of devastating wildfires.
Other researchers have also found that
fire suppression policies in combination
with other land uses have increased the
probability of high-intensity fire due to
past land use, fire suppression, and
unnaturally high fuel loadings (Cooper
1960, pp. 161–162; Covington and
Moore 1994, pp. 45–46; Swetnam and
Baison 1994, pp. 12–13; Touchan et al.
1995, pp. 268–272; White 1985, p. 589).
Not surprisingly, the intensity (size and
severity) of forest fires has increased in
recent times (Covington and Moore
1994, p. 40; Westerling et al. 2006, p.
940).
The effects of these catastrophic
wildfires include the removal of
vegetation, the degradation of watershed
condition, altered stream behavior, and
increased sediment and ash flows into
streams. These effects can harm fish
communities, as observed in the 1990
Dude Fire, when corresponding ash
flows drastically reduced some fish
populations in Dude Creek and the East
Verde River (Voeltz 2002, p. 77). Fire
has become an increasingly significant
threat in lower-elevation communities
as well. Esque and Schwalbe (2002, pp.
180–190) discuss the effect of wildfires
in the upper and lower subdivisions of
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Sonoran desertscrub. The widespread
invasion of nonnative annual grasses,
such as brome (Bromus sp.) and
Mediterranean grasses (Schismus sp.),
appear to be largely responsible for
altered fire regimes that have been
observed in these communities, which
are not adapted to fire (Esque and
Schwalbe 2002, p. 165). African
buffelgrass (Pennisetum ciliare) is
recognized as another invading
nonnative plant species throughout the
lower elevations of northern Mexico and
Arizona. Nijhuis (2007, pp. 1–7)
discusses the spread of nonnative
buffelgrass within the Sonoran Desert of
Arizona and adjoining Mexico, citing its
ability to out-compete native vegetation
and present significant risks of fire in an
ecosystem that is not adapted to fire. In
areas comprised entirely of native plant
species, ground vegetation density is
mediated by barren spaces that do not
allow fire to carry itself across the
landscape. However, in areas where
nonnative grasses have become
established, the fine fuel load is
continuous, and fire is capable of
spreading quickly and efficiently (Esque
and Schwalbe 2002, p. 175). These
nonnative grasses thus increase the
potential for catastrophic wildfire.
After disturbances such as fire,
nonnative grasses may exhibit dramatic
population explosions, which hasten
their effect on native vegetative
communities. Additionally, with
increased fire frequency, these
population explosions ultimately lead to
a type-conversion of the vegetative
community from desertscrub to
grassland (Esque and Schwalbe 2002,
pp. 175–176). Fires carried by the fine
fuel loads created by nonnative grasses
often burn at unnaturally high
temperatures, which may result in soils
becoming hydrophobic (water
repelling), exacerbate sheet erosion, and
contribute large amounts of sediment to
receiving water bodies, thereby affecting
the health of the riparian community
(Esque and Schwalbe 2002, pp. 177–
178). The siltation of isolated, remnant
pools in intermittent streams
significantly affects lower-elevation
species by increasing the water
temperature, reducing dissolved oxygen,
and reducing or eliminating the
permanency of pools, as observed in
pools occupied by lowland leopard
frogs (Rana yavapaiensis) and native
fish (Esque and Schwalbe 2002, p. 190).
Fires in the Southwest frequently
occur during the summer monsoon
season. As a result, fires are often
followed by rain that washes ash-laden
debris into streams. Rinne (2004, p. 151)
found significant reductions in fish
abundance as a result of these ash flows,
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with reductions in fish abundance
ranging from 70 to 100 percent. Extreme
summer fires, such as the 1990 Dude
Fire, and corresponding ash flows, have
drastically reduced some fish
populations. Some recent examples of
extreme summer fires that have reduced
native fish populations include the 2002
Rodeo-Chedeski Fire, the 2003 Aspen
Fire, and the 2004 Willow Fire, all of
which burned parts of watersheds
occupied by roundtail chub. Carter and
Rinne (unpubl. data) found that the
Picture Fire both benefited and
eliminated headwater chub, a closely
related species that occurs in similar
habitat, from portions of Spring Creek.
The fire eliminated chubs from Turkey
Creek, a tributary to Spring Creek. In
other parts of Spring Creek, however,
chubs initially declined but later thrived
after the fire, presumably because most
of the nonnative fishes were eliminated.
Dunham et al. (2003, pp. 189–190)
examined how fire affects nonnative
species invasions; although habitat
alteration over time can facilitate
nonnative species with wider habitat
tolerances, native species may be better
able to withstand ash flows and
flooding. Thus immediately post-fire,
nonnatives may be completely
eliminated and the few natives present
can take advantage of the reduction in
predators. But such events, at a
minimum, represent a genetic
bottleneck (drastic reduction in
population size) for the species that
could adversely impact populations via
genetic threats, such as inbreeding
depression (reduced health due to
elevated levels of inbreeding) and
genetic drift (a reduction in gene flow
within the species that can increase the
probability of unhealthy traits) (Meffe
and Carrol 1994, pp. 156–167). Many
roundtail chub populations are
fragmented and isolated. Fagan et al
(2002, p. 3254) found that, as a result of
this fragmentation and isolation,
roundtail chub has moderately high risk
of local extirpation. Dunham et al.
(2003, pp. 188–189) found that the
threat of fire to fish populations is much
greater for highly fragmented and
isolated populations of fishes.
Undocumented Immigration and
International Border Enforcement and
Management
Cantrell (2009, p. 12) indicated that
undocumented immigration and
international border enforcement and
management could be a threat in nine
areas occupied by roundtail chub.
Because the roundtail chub is extirpated
from most of the southern portions of its
range, such as the San Pedro River, this
threat is more likely to affect potential
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recovery areas than currently occupied
habitats, but is a possible threat in some
occupied streams. Undocumented
immigrants and smugglers attempt to
cross the International border from
Mexico into the United States in areas
historically and currently occupied by
the roundtail chub. These illegal border
crossings and the corresponding efforts
to enforce U.S. border laws and policies
have been occurring for many decades
with increasing intensity and have
resulted in unintended adverse effects
to biotic communities in the border
region. During the warmest months of
the year, many attempted border
crossings occur in riparian areas that
serve to provide shade, water, and
cover. Increased U.S. border
enforcement efforts that began in the
early 1990s in California and Texas have
resulted in a shift in crossing patterns
and increasingly concentrated levels of
attempted illegal border crossings into
Arizona (Segee and Neeley 2006, p. 6).
Traffic on new roads and trails from
illegal border crossing and enforcement
activities, as well as the construction,
use, and maintenance of enforcement
infrastructure (e.g., fences, walls, and
lighting systems), leads to compaction
of streamside soils, and the destruction
and removal of riparian vegetation.
Current border infrastructure projects,
including vehicle barriers and
pedestrian fences, are located
specifically in valley bottoms and have
resulted in direct impacts to water
courses and altered drainage patterns
(Service 2008, p. 4). These activities also
produce sediment in streams, which
affects their suitability as habitat for
roundtail chub by reducing their
permanency and altering their physical
and chemical parameters. Riparian areas
along the upper San Pedro River have
been impacted by abandoned fires that
undocumented immigrants started to
keep warm or prepare food (Segee and
Neeley 2006, p. 23).
Undocumented immigrants use
wetlands for bathing, drinking, and
other uses (Segee and Neeley 2006, pp.
21–22). These activities can contaminate
the water quality of the wetlands and
lead to reductions in habitat quality for
roundtail chub (Rosen and Schwalbe
1988, p. 43; Segee and Neeley 2006, pp.
21–22). In addition, numerous
observations of littering and destruction
of vegetation and wildlife occur
annually throughout the border region,
which can adversely affect the quality of
habitat for the roundtail chub (Service
2006, p. 95).
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Conservation Actions Relevant to
Factor A
There are several existing
conservation agreements for native fish
species that include roundtail chub
(discussed in detail in Factor E below):
the Utah Department of Natural
Resources’ ‘‘Range-wide conservation
agreement and strategy for roundtail
chub (Gila robusta), bluehead sucker
(Catostomus discobolus), and
flannelmouth sucker (Catostomus
latipinnis)’’ (Range-wide Agreement;
Utah Department of Natural Resources
2002); the New Mexico Department of
Game and Fish’s (NMDGF) ‘‘Colorado
River Basin Chubs Recovery Plan’’ (New
Mexico Plan; Carman 2006), which
includes the headwater and Gila chubs;
and the AGFD’s ‘‘Arizona Statewide
Conservation Agreement for Roundtail
Chub (Gila robusta), Headwater Chub
(Gila nigra), Flannelmouth Sucker
(Catostomus latipinnis), Little Colorado
River Sucker (Catostomus spp.),
Bluehead Sucker (Catostomus
discobolus), and Zuni Bluehead Sucker
(Catostomus discobolus yarrowi)’’
(Arizona Agreement; AGFD 2006).
The Range-wide Agreement, Arizona
Agreement, and New Mexico Plan all
include actions intended to reduce the
threat of habitat loss. The Range-wide
Agreement recommends enhancing and
maintaining habitat for roundtail chub,
including: Enhance and/or restore
connectedness and opportunities for
migration of the subject species to
disjunct populations where possible;
restore altered channel and habitat
features to suitable conditions; provide
flows needed for all life stages; maintain
and evaluate fish habitat improvements;
and install regulatory mechanisms for
the long-term protection of habitat (e.g.,
conservation easements, water rights).
The Arizona Agreement identifies the
need to secure, enhance, and create
habitat as one of its conservation
strategy tasks and includes these
subtasks:
(1) Maintain instream flow;
(2) Manage detrimental nonnative fish
and other aquatic species;
(3) Evaluate effectiveness of nonnative
management efforts;
(4) Restore natural fire regimes;
(5) Manage the spread of infectious
diseases and parasites to habitats of the
subject species;
(6) Enhance and/or restore
connectedness;
(7) Develop appropriate flow
recommendations for areas where
existing flow regimes are inadequate;
(8) Implement flow recommendations;
(9) Restore altered channel and
habitat features;
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(10) Create, maintain, and evaluate
fish refugia throughout historic range;
and
(11) Maintain habitat quality.
The New Mexico Plan identifies the
need to address habitat loss, including:
(1) Identify and determine habitat
requirements for all life history stages of
roundtail chub in the San Juan and Gila
River basins;
(2) Support efforts within existing
programs to enable habitat restoration
and protection for recovery;
(3) Identify and secure resources to
promote habitat restoration and
protection;
(4) Rehabilitate, restore, and secure
historical habitats where chub
restoration is possible;
(5) Inform private and public
landowners about practices that
promote diverse, functional aquatic and
riparian habitats;
(6) Inform private and public
landowners about how to protect chub
habitat;
(7) Identify and secure funding to
promote habitat restoration and
protection; and
(8) Establish formal agreements with
willing participants to enhance habitat
and/or populations for recovery of
roundtail chub.
Several actions are planned or have
been implemented as a result of the
conservation agreements that address
the threat of habitat loss. They are
discussed below.
The Nature Conservancy
(Conservancy) is a signatory to the
Arizona Agreement. In Arizona, the
Conservancy has launched its Nature
Matters fundraising campaign. This
program raises private donations to
support cooperative land and water
protection projects. The Conservancy
contacts landowners to explore their
interest in placing their property in a
permanently protected status, then
works cooperatively with its agency
partners to negotiate purchase and sale
agreements and to develop fundraising
proposals and project financing.
Properties are identified and prioritized
based on the quality of their riparian
and aquatic habitat as well as
opportunities to secure surface water
rights or to file for new water rights to
maintain instream flow.
In 2007, the Conservancy purchased
the Upper Verde River Wildlife Area, a
313-acre (ac) (127-hectare (ha)) parcel
downstream from the Verde River
confluence with Granite Creek near
Paulden, Arizona. The Conservancy
later received the donation of an
additional 160 ac (65 ha). In total, the
acquisition secured the largest
remaining portion of the Verde River
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headwaters still in private ownership
and protects roughly 1 mi (1.6 km) of
high quality riparian and aquatic habitat
from development and improper
livestock grazing. In 2008, the
Conservancy conveyed 293 ac (119 ha)
of this property to the AGFD to be
added to the Upper Verde River Wildlife
Area. In July of 2008, the Conservancy
and AGFD each filed for instream flow
water rights with the Arizona
Department of Water Resources for the
properties.
In 2008, the Conservancy completed
two land acquisitions on the middle
Verde River within the 33-mi (53-km)
stretch that Arizona State Parks has
designated for acquisition as the Verde
River Greenway: a 20-ac (8-ha) parcel
upstream of Camp Verde that is adjacent
to U.S. Forest Service frontage on the
river; and the 209-ac (85-ha) Rockin’
River Ranch property purchased with
Arizona State Parks. The Rockin’ River
property, located at the confluence of
the Verde River and West Clear Creek,
includes 55 ac (22 ha) under irrigation
with surface water rights dating back to
1889. Protection of the property
provides an opportunity to retire and
dedicate water rights to instream flow
for the benefit of wildlife including
roundtail chub. The Conservancy
continues to meet with landowners on
a willing-seller basis to explore
opportunities to protect additional lands
along the river and in the Big Chino
Valley, which overlays the aquifer that
is the primary groundwater source for
the upper Verde River, and to pursue
private and public funding to support
land and water protection in the Verde
watershed. These actions could help
secure instream flow and protect
riparian areas from harmful land uses,
benefitting roundtail chub.
In 2006, the Conservancy received as
a donation the Cobra Ranch property at
the headwaters of Aravaipa Creek near
Klondyke, Arizona. The addition of this
property to the Conservancy’s Aravaipa
Canyon Preserve protects over 1 mi (1.6
km) of stream channel and presents
significant habitat restoration
opportunities. The Conservancy plans to
restore native vegetation on 100 ac (40
ha) of farm ground, and retire irrigation,
which will reduce draw-down of the
aquifer and create improved infiltration
patterns on the farm. They will also
strategically plant native vegetation
along the active channel to restore the
natural river channel. Fencing is being
installed to remove grazing from
riparian areas, and planning is ongoing
to restore a natural fire regime. These
actions will serve to restore a historical
cienega that once existed in the
headwaters of Aravaipa Creek, and will
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32369
reduce overgrazing, dewatering, and
sedimentation effects to the roundtail
chub in Aravaipa Creek.
The U.S. Forest Service is also a
signatory to the Arizona Agreement. The
Tonto National Forest is working to
establish an instream flow water right
on approximately 36 mi (58 km) of U.S.
Forest Service lands along Cherry Creek
from its headwaters to the confluence
with the Salt River. Once in place, the
water right should protect enough flow
to provide for roundtail chub habitat in
perpetuity. Similarly, through the
Horseshoe and Bartlett Habitat
Conservation Plan, Salt River Project
(SRP), a large water and electricity
provider for portions of Arizona, is
implementing watershed management
efforts to maintain or improve stream
flows in the Verde River, including
funding of stream gages and scientific
studies, in-kind support for watershed
improvements, and administrative and
legal efforts to curtail stream flow
reductions from illegal surface water
diversions and groundwater pumping.
The Arizona Agreement also includes
provisions for addressing the threat of
catastrophic wildfire. A conservation
strategy task is to restore natural fire
regimes in the watersheds of extant
populations of roundtail chub,
including securing habitat through the
use of prescribed fire and
noncommercial understory thinning to
restore natural fire regimes. Controlled
prescribed fires reduce the risk of
catastrophic wild fires by reducing fuel
loads. The New Mexico Plan also
identifies the need to support research
to determine the tolerance of roundtail
chub to water quality parameters,
particularly those that may be altered
during and after forest fires.
Summary of Factor A
Rivers, streams, and riparian habitats
that are essential for the survival of the
roundtail chub are being adversely
affected and eliminated throughout the
range of the species. Threats, including
water diversions, groundwater
pumping, dams, channelization, and
erosion-related effects, are occurring
that impact both the amount of water
available for habitat, as well as the
water’s suitability for roundtail chub.
Threats from flood control,
development, roads, water withdrawal,
improper livestock grazing, recreation,
and high-intensity wildfire dry up, silt
in, physically alter, and chemically
pollute habitats of the roundtail chub
such that habitats become permanently
unsuitable. These threats have been
documented historically and are either
occurring or likely to occur throughout
the range of the roundtail chub. These
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threats reduce the habitat’s suitability as
cover for protection from predators, as
a foraging area, and as spawning and
nursery areas. Despite the conservation
actions discussed above, the dewatering
of aquatic habitats in the arid lower
Colorado River basin poses a significant
threat to all native fish of the region,
including roundtail chub. All of these
threats are anthropogenic and can be
expected to continue, if not increase,
given the predictions for increases in
human population expansion in the
region. Efforts to ameliorate these
threats through established conservation
agreements have met with some success,
but are in the early stages of
implementation.
times grew only 12.8 percent of their
initial weight compared to fish not
recaptured, which grew 29.7 percent of
their initial weight. Ward et al. (in
press) also found some mortality from
use of passive integrated transponder
tags in related Gila chub (G. intermedia)
and bonytail, although mortality rate
was low. We believe the level of
handling of roundtail chubs for
scientific purposes is low, and the
results of these studies suggest that
handling roundtail chubs for scientific
purposes is not a significant threat to
the species.
Factor B. Overutilization for
Commercial, Recreational, Scientific, or
Educational Purposes
Overutilization of roundtail chub for
commercial, recreational, scientific, or
educational purposes is not considered
a significant threat to the roundtail chub
in the lower Colorado River basin.
Roundtail chub is a permitted sport fish
in Arizona (AGFD 2008). One roundtail
chub greater than 13 in. (33 cm) is
allowed via angling per day. The AGFD
has also established a catch-and-release
only, artificial fly and lure only, single
barbless hook, 7-month fishing season
for roundtail chub in Fossil Creek. A
4.5-mi (7.2-km) middle reach segment of
Fossil Creek will be open to catch-andrelease fishing for roundtail chub from
Oct 3, 2009, through April 30, 2010. The
remainder of the year, the area is closed
to all fishing. But angler use of roundtail
chub is light (C. Cantrell, AGFD, pers.
comm. 2009), and we do not believe that
overutilization from current levels of
angling is a threat to the species in
Arizona. In the upper Gila River in New
Mexico, where the species is not a legal
sport fish (NMDGF 2008), there are
reports of anglers purposefully
discarding chub species, which may be
having a negative effect on populations
of roundtail chub locally (Voeltz 2002).
Several studies of fish species closely
related to roundtail chub indicate that
handling for scientific purposes
(research and monitoring) may have
some adverse effects on individual fish.
Ruppert and Muth (1997, p. 314) found
that electrofishing caused spinal
hemorrhages in some juvenile
humpback chub (Gila cypha), a closely
related species to roundtail chub, but
did not affect short-term growth or
survival. Paukert et al. (2005, p. 649)
found that use of hoop nets affected fish
growth and condition of bonytail; fish
captured multiple times grew less in
length and weight than fish not
recaptured. Fish recaptured up to five
Overutilization of roundtail chub is
not believed to be a threat to the species
and is therefore not addressed in
conservation planning efforts. All three
conservation agreements include action
items to identify threats; thus, if there is
some unidentified threat from
overutilization or the degree of the
threat has been underestimated, the
conservation agreements should serve to
help identify this in the future.
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Conservation Actions Relevant to
Factor B
Summary of Factor B
Although roundtail chub is a legal
sport fish in Arizona, available
information indicates that the species is
not threatened by overutilization as a
game species from current levels of
angling. There is some information that
collection for scientific purposes has
some adverse effects on individual fish;
however, we do not believe that
handling roundtail chubs for scientific
purposes is a significant threat to the
species.
Factor C. Disease or Predation
Nonnative Species
Nonnative species that compete with
or prey on roundtail chub are a serious
and persistent threat to the continued
existence of the roundtail chub.
Nonnative aquatic species include
fishes, aquatic and semi-aquatic
mammals, reptiles, amphibians,
crustaceans, mollusks (snails and
clams), insects, zooplankton,
phytoplankton, parasites, disease
organisms, algae, and aquatic and
riparian vascular plants. 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, p. 365; Lachner
et al. 1970, pp. 1–4; Ono et al. 1983, p.
90; Minckley and Deacon 1991; Carlson
and Muth 1989, p. 220; Cohen and
Carlton 1995, p.1; Fuller et al. 1999, pp.
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1–3; Clarkson et al. 2005, p. 20; Mueller
2005, pp. 10–12; Olden and Poff 2005,
p. 75). Nonnative species may affect
native fish and other aquatic fauna
through numerous means, including (all
of which may be applicable to the
roundtail chub): Predation (Meffe et al.
1983, p. 316; Meffe 1985, p. 173; Marsh
and Brooks 1989, p. 188; Propst et al.
1992, p. 177; Blinn et al. 1993, p. 139;
Rosen et al. 1995, p. 251), competition
(Lydeard and Belk 1993, p. 370; Baltz
and Moyle 1993, p. 246; Scoppotone
1993, p. 139; Douglas et al. 1994, pp.
15–17), aggression (Meffe 1984, p. 1525;
Karp and Tyus 1990, p. 25), habitat
disruption (Hurlbert et al. 1972, p. 639;
Fernandez and Rosen 1996, p. 3),
introduction of diseases and parasites
(Clarkson et al. 1997, p. 66; Robinson et
al. 1998, p. 599), and hybridization
(Dowling and Childs 1992, p. 355;
Echelle and Echelle 1997, p. 153).
Because the impacts of competition
with and predation by nonnative
species are often interrelated and
difficult to discuss separately, we will
discuss all impacts of nonnative species
in this section.
In an evolutionary context, the native
fish community of the lower Colorado
River basin, including roundtail chub,
evolved with low species diversity and
with few predators and competitors and
thus co-evolved with few predatory fish
species. In contrast, many of the
nonnative species co-evolved with high
species diversity and many predatory
species (Clarkson et al. 2005, p. 21). A
contributing factor to the decline of
native fish species cited by Clarkson et
al. (2005, p. 21) is that most of the
nonnative species evolved behaviors,
such as nest guarding, to protect their
offspring from these many predators,
while native species are generally
broadcast spawners that provide no
parental care. In the presence of
nonnative species, the reproductive
behaviors of native fish fail to allow
them to compete effectively with the
nonnative species, and, as a result, the
viability of native fish populations is
reduced.
In the Southwest, Miller et al. (1989,
p. 22) 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 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, p. 391). The
widespread decline of native fish
species from the arid southwestern
United States and Mexico from
interactions with nonnative species has
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been manifested in the listing rules of
nine native species listed under the Act
whose historical ranges overlap with the
historical and current distribution of the
roundtail chub: Bonytail (Gila elegans)
(45 FR 27710; April 23, 1980),
humpback chub (Gila cypha) (32 FR
4001; March 11, 1967), Gila chub (Gila
intermedia) (70 FR 66663; November 2,
2005), Colorado pikeminnow
(Ptychocheilus lucius) (32 FR 4001;
March 11, 1967), spikedace (Meda
fulgida) (51 FR 23769; July 1, 1986),
loach minnow (Tiaroga cobitis) (51 FR
39468; October 28, 1986), razorback
sucker (Xyrauchen texanus) (56 FR
54957; October 23, 1991), desert pupfish
(Cyprinodon macularius) (51 FR 10842;
March 31, 1986), and Gila topminnow
(Poeciliopsis occidentalis) (32 FR 4001;
March 11, 1967). In total within
Arizona, 19 of 31 (61 percent) native
fish species are listed under the Act.
Arizona ranks the highest of all 50
States in the percentage of native fish
species with declining trends (85.7
percent, Stein 2002, p. 21; Warren and
Burr 1994, pp. 6–18). In the Gila River
basin, introduction of nonnatives is
considered a major factor in the decline
of all native fish species (Miller 1961,
pp. 377–379; Williams et al. 1985, p. 1;
Minckley and Deacon 1991). In Arizona,
release or dispersal of new nonnative
aquatic organisms is a continuing
phenomenon (Rosen et al. 1995, p. 259;
Service 2008, p. 264).
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 (Service 2008,
p. 1), sport fish stocking (Clarkson et al.
2005, p. 20), aquaculture and aquarium
releases (Courtenay 1993, pp. 35–62;
Crossman 1991, p. 46; Crossman and
Cudmore 2000, pp. 129–134; Mackie
2000, pp. 135–150), bait-bucket release
(release of fish used as bait by anglers)
(Crossman 1991, p. 50; Litvak and
Mandrak 1993, p. 6), and to control
other species (such as the introduction
of herbivorous fish to control aquatic
plants) (Bailey 1978, p. 181; Courtney
1993, p. 37).
In the Verde River system alone,
Rinne et al. (1998, p. 3) estimated that
over 5,300 independent stocking actions
occurred that involved 12 different
species of nonnative fish species since
the 1930s and 1940s. If we extrapolate
that effort over the same timeframe for
other historically occupied, larger-order
systems known as recreational fisheries
(such as the Salt, upper Gila, Bill
Williams, and San Pedro Rivers, and
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Oak Creek and other tributaries with
significant flow throughout central and
southern Arizona), in addition to the
other private stockings of stock tanks
and other isolated habitat, the
magnitude of the nonnative species
invasion over this timeframe becomes
clear. Subsequent to these efforts, but to
a lesser extent, the spread of bullfrogs
and crayfish, both purposefully and
incidentally, commenced during the
1970s and 1980s (Tellman 2002, p. 43).
We estimate that nearly 100 percent of
the habitat that historically supported
roundtail chub has been invaded over
time, either purposefully or indirectly
through dispersal, by nonnative fishes
and other aquatic species.
Nonnative fishes known from within
the historical range of roundtail chub in
the lower Colorado River basin include
channel catfish (Ictalurus punctatus),
flathead catfish (Pylodictis olivaris), red
shiner (Cyprinella lutrensis), fathead
minnow (Pimephales promelas), green
sunfish (Lepomis cyanellus), warmouth
(L. gulosus), bluegill (L. macrochiris),
largemouth bass (Micropterus
salmoides), smallmouth bass (M.
dolomieui), rainbow trout (Oncorynchus
mykiss), western mosquitofish
(Gambusia affinis), carp (Cyprinus
carpo), yellow bullhead (Ameiurus
natalis), black bullhead (A. melas), and
goldfish (Carassius auratus) (Bestgen
and Propst 1989, pp. 409–410; Marsh
and Minckley 1990, p. 265; Sublette et
al. 1990, pp. 112, 243, 246, 304, 313,
318; Abarca and Weedman 1993, pp. 6–
12; Stefferud and Stefferud 1994, p. 364;
Weedman and Young 1997, p. 1,
Appendices B, C; Rinne et al. 1998, pp.
3–6; Voeltz 2002, p. 88; Bonar et al.
2004, pp. 1–108; Fagan et al. 2005, pp.
34, 38–39, 41). The fastest expanding
nonnative species are red shiner,
fathead minnow, green sunfish,
largemouth bass, western mosquitofish,
and channel catfish. These species are
considered to be the most invasive in
terms of their negative impacts on
native fish communities (Olden and Poff
2005, p. 75).
Smaller size classes (juvenile and
subadult fish) are more vulnerable to
predation because the size of a fish that
a predatory fish can consume is limited
by the predator’s gape size. Brouder et
al. (2000, p. 13) found that size class of
native fishes consumed (including
roundtail chub) by predatory nonnative
fishes in the Verde River was 1.3 to 3.5
in (34 to 90 millimeters (mm)). This
winnowing effect results in a population
of only large adult fish, which
eventually crashes. A spectacular
example of this is the case of the
razorback sucker in Lake Mohave in
Arizona and Nevada. For decades, no
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recruitment was documented within the
population, although large adults
(razorback sucker is a large species, with
adults up to 20 in. (500 mm) or longer
in total length) remained common. This
situation was possible because
razorback sucker are very long-lived,
living 40 years or more (McCarthy and
Minckley 1987, p. 87). The population
eventually crashed in the 1990s because
of a total lack of recruitment due to
predation by nonnative fish species on
smaller, younger fish, although
conservation efforts have resulted in
maintenance of a much smaller stocked
population (Service 2002a, pp. 9, 11;
Mueller 2005, p. 11). A similar
population crash likely happened to
bonytail, a species closely related to
roundtail chub, in Lake Mohave, with
the crash happening sooner because
bonytail likely have a shorter life span
(Service 2002b, p. 11, A–6).
The introduction of more aggressive
and competitive nonnative fish has
likely led to losses of roundtail chub
(Voeltz 2002, p. 88). Dudley and Matter
(2000, p. 24) found that nonnative green
sunfish prey on, compete with, and
virtually eliminate recruitment of Gila
chub (a closely related species to
roundtail 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.
2004, pp. 86–87), with recruitment of
Gila chub effectively eliminated by
nonnative green sunfish. In the Verde
River mainstem, Bonar et al. (2004, p.
57) found that nonnative fishes were
approximately 2.6 times more dense per
unit volume of river than native fishes,
and their populations were
approximately 2.8 times that of native
fishes per unit volume of river. Bonar et
al. (2004, pp. 6–7) found that
largemouth bass, smallmouth bass,
bluegill, green sunfish, channel catfish,
flathead catfish, and yellow bullhead all
consumed native fish; although
roundtail chub was not detected in the
diet of any nonnative fishes, this is
likely only due to the relative rarity of
the species compared with other native
fish, as well as the short time necessary
for a fish to be digested. Roundtail
chubs have been found in stomachs of
largemouth bass in the lower Salt River
(P. Unmack, Arizona State University,
pers. comm. 2008). Bestgen and Propst
(1989, p. 406) reported that, of
nonnatives present in New Mexico,
smallmouth bass, flathead catfish, and
channel catfish most impacted roundtail
chub via predation. Native fishes,
including roundtail chub, have
experienced significant declines in the
Salt River above Roosevelt Lake,
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concurrent with a significant increase in
flathead and channel catfish numbers
(Creef and Clarkson 1992, p. 5; Jahrke
and Clark 1999 p. 9). Brouder et al.
(2000, p. 9), based on population
estimates, determined that nonnative
species were likely suppressing
roundtail chub populations in two areas
of the upper Verde River. Yard et al.
(2008) found that rainbow trout
predation on humpback chub in Grand
Canyon likely resulted in significant
levels of humpback chub mortality
(Yard et al. 2008, p. 53).
In some areas, the presence of
nonnative species appears to be limiting
recruitment of roundtail chub, with only
large adults encountered during surveys
(Cantrell 2009, p. 10). Red shiner is
known to compete with native
southwestern cyprinids (Minckley and
Deacon 1968, pp. 1427–1428; Minckley
1973, p. 138; Douglas et al. 1994, p. 9),
and prey on larval fishes (Ruppert et al.
1993, p. 397). In a study of the roundtail
chub population in the lower Salt and
Verde Rivers, Bryan and Hyatt (2004, p.
3) estimated adult population size of
roundtail chub to be 1,657, and found
that this was a 74 percent decrease from
just 3 years earlier. Bryan and Hyatt
(2004, pp. 12–13) concluded that the
roundtail chub population in the lower
Salt and Verde Rivers was declining
rapidly due to low recruitment and high
natural mortality, and identified the
‘‘negative impacts of competition and
predation [from the] introduction of
nonnative fishes into roundtail chub
habitat’’ as the likely cause of
recruitment failure. They recommended
that stocking nonnative sport fish ‘‘be
carefully evaluated and probably
suspended, especially with regards to
predatory species’’ and that stocking
rainbow trout ‘‘be thoroughly evaluated
to determine its economic impact and
the specific impacts to the [roundtail]
chub population.’’
Few if any studies of roundtail chub
have effectively demonstrated
competition with nonnative fishes,
although numerous authors have
considered it a threat (Bestgen and
Propst 1989; Brouder et al. 2000; Voeltz
2002; AGFD 2006, p. 5). Bestgen (1985,
p. 53) found that diets between rainbow
trout and roundtail chub differed to an
extent that suggested interactive
segregation of habitat and competition
for food resources, and although the
health of the chub population indicated
competition was not severe, in higher
densities, trout competition could
impact roundtail chub. Dudley and
Matter (2000, p. 24) found that green
sunfish utilized the same habitats as
Gila chub, a closely related species to
roundtail chub, and appeared to
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competitively exclude them from
preferred habitats. In the Colorado River
in Grand Canyon, Arizona, diet studies
of humpback chub and rainbow trout
show strong overlap for aquatic
invertebrates such as blackfly larvae
(Simuliidae) and Gammarus (Valdez
and Ryel 1995; Yard et al. 2008), and
removal of nonnative trout is one factor
suspected to be responsible for a recent
increase in humpback chub numbers in
Grand Canyon (U.S. Geological Survey
2006, p. 2). But because rainbow and
brown trout (Salmo trutta) have also
been shown to prey on humpback chub
in the Grand Canyon (Yard et al. 2008),
either a reduction in predation of
humpback chub, or a reduction in
competition with humpback chub, or
both, may be responsible. Intuitively,
both scenarios seem likely, and this is
the conventional wisdom of many
researchers studying the effects of
nonnative fishes on natives in the
southwest United States (Marsh and
Douglas 1997; Brouder et al. 2000;
Voeltz et al. 2002; AGFD 2006, p. 5).
Interestingly, Bestgen (1985, p. 53)
noted that any competition between
rainbow trout and roundtail chub would
likely be significant only if rainbow
trout occurred in high densities, and in
Grand Canyon, high densities of
rainbow trout appear to be impacting
the humpback chub population (Yard et
al. 2008; U.S. Geological Survey 2006).
Marks et al. (in press) found that when
nonnative fish species were removed,
roundtail chub numbers and
recruitment increased dramatically.
Again, whether this is because
nonnative species were preying on or
competing with roundtail chub is still a
question, but perhaps one that is not
necessary to answer, for as Marks et al.
(2008) illustrate, the remedy for this
threat is obvious.
Aquatic habitat alterations due to land
use practices such as livestock grazing
and dams and dam operation may
facilitate the spread and persistence of
nonnative fishes. Dams by their very
purpose and nature serve to reduce
flood flows and increase base flows.
Floods have been identified as a
potential means to disadvantage
nonnative fishes and thereby advantage
native fishes (Meffe 1984, p. 1525).
Haney et al. (2008, p. 61) suggested that
diminished river flow due to diversion
may be an important factor in loss of
native fish from the Verde River.
Variation in river flows may provide
both advantages and disadvantages to
aquatic species. The timing, duration,
intensity, and frequency of flood events
has been altered to varying degrees by
the presence of dams along many stream
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courses within the range of the
roundtail chub, which affects fish
communities. Flood pulses may help to
reduce populations of nonnative species
because, unlike native fish that are
adapted to dramatic fluctuations in
water conditions and flow regimes
(including random high-intensity
events, such as flooding, extreme water
temperatures, and excessive turbidity),
nonnative fishes appear to be less welladapted to such events. Dams, through
their amelioration of flood flows and
increased base flows, may provide more
suitable habitat for nonnative fishes
(Meffe 1984, p. 1525; Haney et al. 2008,
p. 61).
Livestock tanks also may facilitate the
persistence and spread of nonnative
species of fish, amphibians, and crayfish
that are intentionally or unintentionally
stocked by anglers and private
landowners (Rosen et al. 2001, p. 24).
The management of stock tanks is an
important consideration for native fish
restoration. Stock tanks associated with
livestock grazing can be intermediary
‘‘stepping stones’’ in the dispersal of
nonnative species from larger source
populations to new areas, and serve as
source populations themselves (Rosen et
al. 2001, p. 24; Stone et al. 2007, p. 133).
Recent assessments of the fish fauna
of the lower Colorado River basin have
provided additional insight into the
importance of nonnative fishes as a
threat to native fish including the
roundtail chub. The Desert Fishes Team
is an ‘‘independent group of biologists
and parties interested in protecting and
conserving native fishes of the Colorado
River basin’’ and includes personnel
from the U.S. Forest Service, U.S.
Bureau of Reclamation, Bureau of Land
Management (BLM), University of
Arizona, Arizona State University, the
Conservancy, and independent experts
(Desert Fishes Team 2003, p. 1). Desert
Fishes Team (2003, p. 1) declared the
native fish fauna of the Gila River basin
to be critically imperiled, citing habitat
destruction and nonnative species as the
primary factors for the declines. The
Desert Fishes Team recommended
control and removal of nonnative fish as
an overriding need to prevent the
decline and ultimate extinction of
native fish species within the basin.
Clarkson et al. (2005) discuss
management conflicts as a primary
factor in the decline of native fish
species in the southwestern United
States and declare the entire native
fauna as imperiled. The investigators
cite nonnative species as the most
consequential factor leading to rangewide declines that prevent or negate
recovery efforts from being
implemented or being successful
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(Clarkson et al. 2005, p. 20). Clarkson et
al. (2005, p. 20) note that over 50
nonnative species have been introduced
into the Southwest as either sport fish
or bait fish and are still being actively
stocked, managed for, and promoted by
both Federal and State agencies as
nonnative recreational fisheries. To help
resolve the conflicting management
mandates of native fish recovery and the
promotion of recreational fisheries,
Clarkson et al. (2005, pp. 22–25)
propose the designation of entire
watersheds as having either native or
nonnative fisheries and the management
of watersheds to aggressively meet these
goals. Clarkson et al. (2005, p. 25)
suggest that current management of
fisheries within the southwestern
United States as status quo will have
serious adverse effects on native fish
species and affect the long-term viability
of these species.
Mash and Pacey (2005, p. 59)
concluded, ‘‘The presence of nonnative
fishes alone precludes life-cycle
completion by the natives. In the
absence of nonnatives, however, the
natives thrive even in severely altered
habitats.’’ This statement appears to
apply well to roundtail chub, and the
best evidence is provided by the
response of the species when nonnative
fishes are removed. Marks et al. (in
press) examined the effect of the
removal of nonnative species on native
species by measuring fish abundance
before and after a restoration project to
restore flow and chemically remove
nonnative fishes (using the chemical
rotenone, a fish pesticide) to benefit
native fish species including the
roundtail chub. They found that
roundtail chub abundance increased
dramatically after restoration, and
attributed most of this response to the
removal of nonnative fish species.
Marks et al. (in press) suggested that
nonnative fish removal may be a more
cost effective method to restore native
fish populations than flow restoration,
because the cost of chemical renovation
was one-tenth the cost of flow
restoration at Fossil Creek. Roundtail
chub is a stream species that appears to
require flow (Service 1987; Marks et al.
in press). However, AGFD has found
that roundtail chub can thrive in pond
habitats that are free from nonnative
species (AGFD 2009). Similarly, Mueller
(2008, p. 2) examined the creation and
performance of various nonnative fishfree habitats for bonytail chub, a species
closely related to the roundtail chub,
and found that recruitment occurred in
hatchery-style holding ponds, seemingly
a less than optimal habitat for a species
that occurs in large rivers. Mueller
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(2008) concluded, ‘‘In all cases, the
common denominator was not physical
habitat conditions; it was simply the
absence of nonnative predators.’’ As
these findings illustrate, habitat may not
be the biggest concern for roundtail
chub because the species can thrive
even in habitats that are seemingly less
than ideal, as long as nonnative species
are not present. Despite some lack of
direct evidence of the effect of predation
and recruitment on roundtail chub, the
results of removal of nonnative fish
clearly demonstrate that either
predation or competition is occurring
and is a serious threat to the species.
Nonnative species predation may be
having an effect on roundtail chub that
is known as the ‘‘predator pit’’
hypothesis (Messier 1994, p. 480). This
hypothesis proposes that as a
population of a species decreases,
especially when this happens rapidly,
the predators of the species will have an
increasing impact on its survival due to
the relatively constant consumption
amount, and thus increased
consumption rate. In situations where
predator populations also increase, the
effect can be substantial. Given the
variety of habitat-altering activities that
appear to be affecting roundtail chub
throughout the lower Colorado River
basin, activities such as dewatering and
urbanization are likely reducing
roundtail populations. With these
reductions, predation by nonnative
species create a ‘‘predator pit’’ scenario.
At least two species of crayfish, the
red swamp crayfish (Procambaris clarki)
and the northern or virile crayfish
(Orconectes virilis), have been
introduced into Arizona aquatic
ecosystems and are now widely
distributed and locally abundant in a
broad array of natural and artificial freeflowing and still-water habitats
throughout the State, including
numerous streams within the historical
and current range of the roundtail chub
(Inman et al. 1998, p. 3; Voeltz 2002, pp.
15–88). Crayfish appear to negatively
impact native fishes and aquatic
habitats through habitat alteration by
burrowing into stream banks and
removing aquatic vegetation, resulting
in decreases in vegetative cover and
increases in turbidity (Lodge et al. 1994,
p. 1270; Fernandez and Rosen 1996, pp.
10–12). Carpenter (2005, pp. 338–340)
documented that crayfish may reduce
the growth rates of native fish through
competition for food and noted that the
significance of this impact may vary
between species. Crayfish also prey on
fish eggs and larvae (Inman et al. 1998,
p. 17). Crayfish alter the abundance and
structure of aquatic vegetation by
grazing on aquatic and semiaquatic
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vegetation, which reduces the cover for
fish (Fernandez and Rosen 1996, pp.
10–12). Creed (1994, p. 2098) found that
filamentous alga (Cladophora
glomerata) was at least 10-fold greater in
aquatic habitat absent crayfish.
Filamentous alga is an important
component of aquatic vegetation that
provides cover and food for fish,
including roundtail chub.
Diseases and Parasites
Diseases, specifically parasite
infestations, are a threat to the roundtail
chub. Asian tapeworm (Bothriocephalus
acheilognathi) was introduced into the
United States via imported grass carp
(Ctenopharyngodon idella) in the early
1970s. Asian tapeworm 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
roundtail 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 (1)
impeding the digestion of food as it
passes through the intestinal track, and
(2) causing emaciation and starvation
when large numbers of worms feed off
of the fish. The Asian tapeworm is
present in the Colorado River basin in
the Virgin River (Heckman et al. 1986,
p. 662) and the Little Colorado River
(Clarkson et al. 1997, p. 66). It has
recently invaded the Gila River basin
and was found in 1998 in the Gila River
near Ashurst-Hayden Dam. Research
and monitoring of the effects of Asian
tapeworm on a related species, the
humpback chub, indicate that this
parasite may be a significant cause of
mortality because large numbers of
Asian tapeworm have been detected in
wild humpback chub, and laboratory
studies indicate that such infestations
cause mortality in Gila species (U.S.
Geological Survey 2004, p. 1; 2005, pp.
2–3).
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. Infections
of Lernaea sp. may have increased in
recent years. James (1968, pp. 21–29)
found that Lernaea sp. was very rare in
museum specimens collected prior to
the 1930s, but increased in intensity
from the 1930s to the 1960s, with
roundtail chubs exhibiting the greatest
increase (10.8 percent). Hendrickson
(1993, pp. 45–46) noted very high
infections of Lernaea sp. during warm
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periods in the Verde River, and Voeltz
(2002, p. 69) 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.’’
Girmendonk and Young (1997, p. 55)
concluded that ‘‘parasitic infestations
may greatly affect the health and thus
population size of native fishes.’’ A dieoff of fish including roundtail chub in
Trout Creek was likely due to heavy
infestations of black grub (Neascus sp.),
an internal parasite, which may have
weakened the fish sufficiently to cause
bacteria hemorrhagic septicemia or
blood poisoning (Voeltz 2002, p. 33).
The parasite Ichthyophthirius
multifiliis, or ‘‘Ich’’, is a potential threat
to roundtail chub. ‘‘Ich’’ has occurred in
some Arizona streams, probably favored
by high temperatures and crowding as a
result of drought (Mpoame 1982, p. 45).
This protozoan becomes embedded
under the skin and within the gill
tissues of infected fish. When the ‘‘Ich’’
matures, it leaves the fish, causing fluid
loss, physiological stress, and sites that
are susceptible to infection by other
pathogens. If the ‘‘Ich’’ are present in
large enough numbers, they can also
impact respiration because of damaged
gill tissue.
Conservation Actions Relevant to
Factor C
All three of the conservation
agreements have various provisions to
address the threat of nonnative species.
The Range-wide Agreement
recommends that State conservation
agreements include provisions to
control (as feasible and where possible)
threats posed by nonnative species that
compete with, prey upon, or hybridize
with roundtail chub. The Arizona
Agreement addresses the threat of
predation and competition from
nonnative species, as well as the threat
of disease and parasites, in its
provisions for habitat protection. These
provisions include: managing
detrimental nonnative aquatic species in
streams designated for conservation of
the subject species; evaluating
effectiveness of nonnative management
efforts; and managing the spread of
infectious diseases and parasites to
habitats of the subject species. The
Arizona Agreement also includes an
indentified deliverable of a native fish
management plan that would also serve
to address this threat.
The New Mexico Plan includes the
following provisions to address the
threat of nonnative species:
(1) Determine the distribution and
abundance of nonnative species in the
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San Juan and Gila River watersheds and
the physical barriers to their expansion;
(2) Investigate the impacts,
particularly competition, habitat
modification, and predation, of
nonnative species on roundtail chub;
(3) Determine areas of the San Juan
and Gila River watersheds where
limited nonnative species distribution
and abundance may provide
opportunities for chub restoration;
(4) Work with sport fish managers to
coordinate native and nonnative fish
management and identify stream areas
expressly for recovery of native species;
(5) When appropriate and feasible,
remove nonnative species that present a
threat to roundtail, Gila, and headwater
chubs;
(6) Prevent the introduction of
nonnative species into the watersheds
utilizing existing information and
programs when possible;
(7) Support efforts to re-establish the
historical native aquatic community in
ecologically appropriate habitats in the
San Juan and Gila River basins utilizing
existing programs when possible; and
(8) Inform local resource users about
the impacts of nonnative species on
roundtail chub.
Specific actions implemented through
the conservation agreements to address
the threats under Factor C include
fisheries management planning efforts
and creation of new chub populations in
nonnative-fish-free habitats. AGFD
convened a Statewide Fish Management
Team in 2008, which developed a
process to delineate fish management
strategies Statewide to address the dual
mandates of providing native fish
habitat and sport fish angling
opportunities for the public. AGDF
intends that this process will serve as
the deliverable management plan for the
Arizona Agreement, and will facilitate
sport fish and native fish management
decisions throughout Arizona. As
discussed in the Status and Distribution
of the Lower Colorado River DPS
section above, AGFD and NMDGF have
created four new populations of
roundtail chub, two in streams (Ash
Creek and Roundtree Canyon) and two
in pond refuges (the Southwest
Academy and Gila River Ranch Preserve
refuge ponds). These efforts are too new
to evaluate their success, but such
projects will be essential to reversing
the decline of the roundtail chub.
Summary of Factor C
Predation and competition with
nonnative aquatic species, and in
particular fish, are, along with
dewatering of habitat, the most
significant threats to the roundtail chub
in the lower Colorado River basin.
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Nonnative aquatic species are a threat to
every population of roundtail chub with
the possible exception of recent
transplants into Roundtree Canyon and
Ash Creek, and perhaps Fossil Creek
and Aravaipa Creek, based on long-term
low levels of occurrence of nonnatives
in these streams and presence of natural
or manmade fish barriers (Voeltz 2002,
p. 47; U.S. Forest Service 2004, p. 1). No
attempt has been made to quantify the
amount of range of these species
affected by parasites, however, parasites
have been documented in numerous
populations and likely occur throughout
the range of these species (Voeltz 2002,
pp. 18–19). Although some actions have
been implemented through conservation
agreements for roundtail chub to
address this threat, these actions are
either not yet complete or too recently
completed to evaluate their success and
contribution to the status of the
roundtail chub.
Factor D. The Inadequacy of Existing
Regulatory Mechanisms
Existing Regulatory Mechanisms
There are currently no specific
Federal protections for roundtail 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 been inadequate to
ameliorate the threats to roundtail chub
in the lower Colorado River basin.
Existing Federal and State regulations
and planning have not achieved
significant conservation of roundtail
chub and its habitat. Although we are
aware that roundtail chub occurs on
Tribal lands, we do not have sufficient
information to evaluate the effectiveness
of Tribal management.
As described in Factor C,
introductions of nonnative fish are
likely a significant threat to roundtail
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 or 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. The use of live bait
is restricted in some of the Gila River
system in Arizona (AGFD 2008, p. 28),
but the use of live bait species (such as
green sunfish) is still permitted in areas
such as the Verde River that currently
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have roundtail chub populations. New
Mexico only allows the use of fathead
minnow as a live bait-fish in the Gila
River drainage in New Mexico, which
covers the extent of the range of
roundtail chub in the lower Colorado
River basin in New Mexico (NMDGF
2008, p. 8). Arizona and New Mexico
also continue to stock nonnative sport
fishes, including such likely predators
and competitors as largemouth bass,
channel catfish, rainbow trout, and
brown trout, for recreational angling
within areas that are connected to
habitat of roundtail chub.
Although restrictions on use of live
bait help reduce the input of nonnative
species into roundtail chub habitat, this
does little to reduce unauthorized bait
use or other forms of ‘‘bait-bucket’’
transfer (e.g., illegal stock of sport fish,
dumping of unwanted aquarium fish)
not directly related to bait use. Such
‘‘bait-bucket’’ transfers can be 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.
AGFD also regulates nonnative
species that can be legally 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 being prohibited unless
specifically allowed. This 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
roundtail chub’s range in the lower
Colorado River basin occurs within
Arizona.
Existing water laws in Arizona and
New Mexico are inadequate to protect
wildlife. The presence of water is
clearly a requirement for the roundtail
chub. Gelt (2008, pp. 1–12) highlighted
the fact that, because existing water
laws are old, they reflect a legislative
interpretation of the resource that is not
consistent with what is known today
about hydrology. For example, over 100
years ago when Arizona’s water laws
were written, the important connection
between groundwater and surface water
was not known (Gelt 2008, pp. 1–12).
Gelt (2008, pp. 8–9) suggested that
preserving stream flows and riparian
areas may be better accomplished by
curtailing surface water uses rather than
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groundwater uses, and that the prior
appropriation doctrine (appropriation of
water rights based upon the water law
concept of ‘‘first in use, first in rights’’)
may be outdated and impractical for
arid areas like Arizona.
The Federal Land Policy and
Management Act of 1976 (43 U.S.C.
1701 et seq.) and the National Forest
Management Act of 1976 (16 U.S.C.
1600 et seq.) direct the Secretary of the
Interior, through BLM, and Forest
Service, respectively, to prepare
programmatic-level management plans
to guide long-term resource
management decisions. In addition, the
U.S. Forest Service is required to
manage habitat to provide appropriate
ecological conditions to support a
diversity of native plant and animal
species (36 CFR 219.10). The Forest
Service is the largest landowner and
manager of roundtail chub habitat and
lists the roundtail chub as a sensitive
species in the lower Colorado River
basin in the southwestern region
(Arizona and New Mexico). The BLM is
updating its sensitive species list for
Arizona and has indicated they will add
roundtail chub. However, a sensitive
species designation provides little
protection to the roundtail chub because
it only requires the Forest Service and
BLM to analyze the effects of their
actions on sensitive species, but does
not require that they choose
environmentally benign actions. Most of
these areas where the majority of extant
populations of roundtail chub occur are
managed by the Forest Service or BLM;
thus ongoing management by these
agencies has not prevented adverse
impacts to roundtail chub habitat.
Although both agencies have riparian
protection goals, neither agency has
specific management plans for the
roundtail chub.
Wetland values and water quality of
aquatic sites inhabited by the roundtail
chub are afforded varying protection
under the Federal Water Pollution
Control Act of 1948 (Clean Water Act;
33 U.S.C. 1251–1376), as amended;
Federal Executive Orders 11988
(Floodplain Management) and 11990
(Protection of Wetlands); and section
404 of the Clean Water Act, which
regulates dredging and filling activities
in waterways. Water quality in the range
of the roundtail chub has declined
despite these laws. The Arizona
Department of Environmental Quality
(2008) has identified several streams
with water quality problems occupied
by roundtail chub. Oak Creek exceeds
the total maximum daily load for
Escherichia coli (E. coli) contamination,
due to a combination of recreation,
septic systems, urban runoff, and
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livestock grazing. Boulder Creek
exceeds the total maximum daily load
for benzene, manganese, mercury, pH,
arsenic, copper, and zinc as a result of
mining activities. The Verde River
exceeds the total maximum daily load
for turbidity/sediment due to livestock
grazing, urban development, and road
use and maintenance. The Arizona
Department of Environmental Quality is
implementing actions through drainage
water quality plans to correct these
problems, but they are ongoing and not
likely to be resolved in the near future.
Our information indicates that the status
of the roundtail chub in these areas has
declined, although it is unclear whether
this is due to these water quality issues
(Voeltz 2002, pp. 35, 72).
The NMDGF has adopted a wetland
protection policy whereby they do not
endorse any project that would result in
a net decrease in either wetland acreage
or wetland habitat values. This policy
may afford some protection to roundtail
chub habitat, although it is advisory
only and destruction or alteration of
wetlands is not regulated by State law.
The State of Arizona Executive Order
Number 89–16 (Streams and Riparian
Resources), signed on June 10, 1989,
directs State agencies to evaluate their
actions and implement changes, as
appropriate, to allow for restoration of
riparian resources. Implementation of
this regulation may have reduced
adverse effects of some State actions on
the habitat of the roundtail chub;
however, we have no monitoring
information on the effects of this State
Executive Order, nor do we have
information indicating that actions
taken under it have been effective in
reducing adverse effects to the roundtail
chub.
The National Environmental Policy
Act of 1969 (NEPA) (42 U.S.C. 4321 et
seq.) requires Federal agencies to
consider the environmental impacts of
their actions. Most actions taken by the
Forest Service, BLM, and other Federal
agencies that affect the roundtail are
subject to NEPA. NEPA requires Federal
agencies to describe the proposed
action, consider alternatives, identify
and disclose potential environmental
impacts of each alternative, and involve
the public in the decision-making
process. However, Federal agencies are
not required to select the alternative
having the least significant
environmental impacts. A Federal
action agency may select an action that
will adversely affect sensitive species
provided that these effects were known
and identified in a NEPA document.
The status of roundtail chub on Tribal
lands is not well known. Any regulatory
or other protective measures for the
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species on Tribal lands would be at the
discretion of the individual Tribe, and
non-Tribal entities often have little
information with which to evaluate
effectiveness. The San Carlos Apache
Tribe has developed a fisheries
management plan that provides
protection to roundtail chub, although
there are only two populations that
potentially occur on San Carlos Apache
lands, representing a very small
percentage of the overall range of the
species in the lower Colorado River
basin. We have limited information on
threats to populations of roundtail chub
on Tribal lands, but land uses on Tribal
lands include livestock grazing,
recreation, limited fuel wood harvest,
limited agriculture, fisheries and
wildlife management, and localized
municipal, urban, and rural
development and associated water use.
The White Mountain Apache Tribe is
preparing a fisheries management plan
that, when completed, could benefit
roundtail chub because 8 of the 31
populations occur wholly or in part on
White Mountain Apache Tribal lands.
The State of New Mexico lists the
roundtail chub as ‘‘State Endangered’’
under its Wildlife Conservation Act,
which prohibits take (New Mexico
Wildlife Conservation Act 17–2–41(B)).
In the State of New Mexico, an
‘‘Endangered Species’’ is defined as
‘‘any species of fish or wildlife whose
prospects of survival or recruitment
within the State are in jeopardy due to
any of the following factors: (1) The
present or threatened destruction,
modification, or curtailment of its
habitat; (2) overutilization for scientific,
commercial or sporting purposes; (3) the
effect of disease or predation; (4) other
natural or manmade factors affecting its
prospects of survival or recruitment
within the State; or (5) any combination
of the foregoing factors’’ as per New
Mexico Statutory Authority 17–2–38.D.
‘‘Take,’’ defined as ‘‘to harass, hunt,
capture or kill any wildlife or attempt to
do so’’ by New Mexico Statutory
Authority 17–2–38.L., is prohibited
without a scientific collecting permit
issued by the NMDGF as per New
Mexico Statutory Authority 17–2–41.C
and New Mexico Administrative Code
19.33.6. However, while the NMDGF
can issue monetary penalties for illegal
take of roundtail chub, the same
provisions are not in place for actions
that result in loss or modification of
habitat (New Mexico Statutory
Authority 17–2–41.C and New Mexico
Administrative Code 19.33.6).
The roundtail chub is identified on
the AGFD draft document (never
finalized), Wildlife of Special Concern
(AGFD 2006b, p. 5). The purpose of the
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Wildlife of Special Concern list is to
provide guidance in habitat
management implemented by land
management agencies. Additionally, the
roundtail chub is considered a ‘‘Tier 1b
Species of Greatest Conservation Need’’
in the AGFD draft document, Arizona’s
Comprehensive Wildlife Conservation
Strategy (AGFD 2006c, p. 371). The
purpose for the Comprehensive Wildlife
Conservation Strategy is to ‘‘provide an
essential foundation for the future of
wildlife conservation and a stimulus to
engage the States, federal agencies, and
other conservation partners to
strategically think about their individual
and coordinated roles in prioritizing
conservation efforts’’ (AGFD 2006c, p.
2). A ‘‘Tier 1b Species of Greatest
Conservation Need’’ is one that requires
immediate conservation actions aimed
at improving conditions through
intervention at the population or habitat
level (AGFD 2006c, p. 32).
As discussed in Factor B, up to one
roundtail chub may be taken and
possessed per day via angling Statewide
in Arizona, with the exception of Fossil
Creek, which is catch and release only,
from Oct 3, 2009, through April 30,
2010. Take of roundtail chub is also
permitted in Arizona via issuance of a
scientific collecting permit (Ariz.
Admin. Code R12–4–401 et seq.). While
the AGFD can seek criminal or civil
penalties for illegal take of roundtail
chub, the same provisions are not in
place for actions that result in
destruction or modification of roundtail
chub habitat.
SRP has completed two habitat
conservation plans (HCPs) for its
operation of Roosevelt Dam and Lake
and its operation of Horseshoe and
Bartlett reservoirs (SRP 2006, 2008,
2009). Through implementation of the
Roosevelt Habitat Conservation Plan,
SRP has permanently protected and will
manage land and water rights for more
than 2,000 ac (809 ha) of riparian and
aquatic habitat along Tonto Creek and
the middle Gila, lower San Pedro, and
Verde Rivers. Conservation measures on
these properties, such as increasing
instream flows, excluding livestock,
improving channel integrity, excluding
vehicle and off-road vehicle traffic,
abating wildfires, and promoting
riparian ecosystem health, will continue
in perpetuity and will directly benefit
native fishes, including the roundtail
chub. For example, one such SRPowned and maintained property is the
Camp Verde Riparian Preserve near
Camp Verde, Arizona, on the Verde
River, which contains a portion of the
Verde River occupied by roundtail chub
(SRP 2006, pp. 26–28).
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The HCP for Horseshoe and Bartlett
Reservoirs specifically covers the
roundtail chub and includes numerous
minimization and mitigation measures
that will benefit the species, including:
rapid drawdown of Horseshoe Lake
annually to disadvantage nonnative fish
species by adversely affecting the
recruitment and growth of these species;
providing funding to AGFD for creation
and maintenance of fish rearing
facilities at its Bubbling Ponds State
Fish Hatchery; providing funding and
support for native fish stocking,
including stocking of roundtail chub;
watershed management efforts that
serve to maintain quality and quantity
of instream flows; native fish
monitoring; and public outreach (SRP
2008, pp. 193–201). SRP is also a
signatory to the Arizona Agreement, and
in this capacity, has funded roundtail
chub genetics research and development
of roundtail chub broodstock. SRP also
works with AGFD to salvage roundtail
chub from its canals (SRP 2009, pp.
6–7).
Roundtail chub derives some
conservation benefit from its cooccurrence with other listed species and
critical habitat in the lower Colorado
River basin. As an example, Bureau of
Reclamation’s interagency consultation
(section 7 compliance) on the operation
and maintenance of the Central Arizona
Project (CAP), a water delivery system
designed to bring water from the
Colorado River to portions of Pima,
Pinal, and Maricopa counties in
Arizona, has greatly benefited the
species. Biological opinions on the CAP
addressed the spread of nonnative
aquatic species through the project
canals from the Colorado River into the
Gila and Santa Cruz River basins
(Service 2001, 2008). Conservation
measures included in these biological
opinions to benefit listed fish and
amphibian species (including the
spikedace, loach minnow, Gila
topminnow, desert pupfish, Gila chub,
and Chiricahua leopard frog (Rana
chiricahuensis)) have benefitted the
roundtail chub and likely will into the
future. In 2004, nonnative fish were
removed from Fossil Creek through
chemical renovation to benefit native
fish species including the roundtail
chub. The Bureau of Reclamation, in
cooperation with AGFD, the Service,
and the Forest Service, also installed a
fish barrier in lower Fossil Creek to
prevent reinvasion of nonnative fish.
The Fossil Creek restoration project was
a conservation measure included in the
CAP biological opinion issued to the
Bureau of Reclamation, and it resulted
in the creation of the only stable-secure
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population of roundtail chub currently
in existence in the lower Colorado River
basin.
Conservation Actions Relevant to
Factor D
The Range-wide Agreement
recommends that the State plans
include provisions to assure adequate
regulatory protection for the roundtail
chub, flannelmouth sucker, and
bluehead sucker within the signatory
States, and to install regulatory
mechanisms for the long-term
protection of habitat (e.g., conservation
easements, water rights). The Rangewide Agreement also recommends that
States develop multi-State nonnative
stocking procedure agreements that
protect all three species and potential
reestablishment sites from the threat of
nonnative species. The Arizona
Agreement includes the provision to
maintain instream flow by securing
habitat through acquisition of water
rights or agreements with water rights
holders to maintain instream flow.
Implementation of these provisions so
far has resulted in the U.S. Forest
Service application for an instream flow
right on Cherry Creek, which contains
roundtail chub, and SRP and
Conservancy applications to the Arizona
Department of Water Resources for
instream flow rights on the Verde River.
These measures and actions may result
in further regulatory protection for
roundtail chub by legally protecting
flows for the species.
Summary of Factor D
Existing regulations within the range
of the roundtail chub address the direct
take of individuals without a permit,
and unpermitted take is not thought to
be a threat to roundtail chub. However,
Arizona and New Mexico statutes do
not provide protection of habitat and
ecosystems. Currently, there are no
regulatory mechanisms in place that
specifically target the conservation of
roundtail chub or its habitat. General
regulatory mechanisms protecting the
quantity and quality of water in riparian
and aquatic communities are inadequate
to protect water resources for the
roundtail chub, particularly in the face
of the significant human population
growth expected within the historical
range of the chub discussed under
Factor A. Conservation actions defined
in existing conservation agreements may
provide some additional regulatory
protection, in particular through
development of instream flow rights to
protect habitat for the roundtail chub,
but no instream flow rights have yet
been acquired, although several
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applications for specific waters have
been submitted.
Factor E. Other Natural or Manmade
Factors Affecting Its Continued
Existence
Fragmented Populations and Stochastic
Events
The rarity of roundtail chub increases
the possible extinction risk associated
with stochastic events such as drought,
flood, and wildfire. Roundtail chub
populations have been fragmented and
isolated to smaller stream segments and
may be vulnerable to natural or
manmade factors (e.g., drought,
groundwater pumping) that might
further reduce their population sizes.
Maintaining several populations with
relatively independent susceptibility to
threats is an important consideration in
the long-term viability of a species
(Shaffer 1987; Goodman 1987).
Redundant populations provide security
from catastrophic events or repeated
recruitment failure. For example,
consider that a single hypothetical
population has a probability of
extinction from a catastrophic event of
10 percent in 200 years. If two
populations are independent, the
probability of both going extinct is 1
percent (0.12). For three populations,
the probability reduces to 0.1 percent
(0.13). Even with an extinction
probability of 25 percent for one
population, the probability of extinction
for two and three populations is 6.3
percent and 1.6 percent, respectively
(Casagrandi and Gatto 1999). Fagan et
al. (2002) determined that individual
roundtail chub populations have a 0.41
percent probability of extirpation given
current status and levels of
fragmentation and isolation. Providing
for multiple populations that are secure
and stable (as defined above in Table 1,
a population that is recruiting with
multiple age classes and that is free
from threats) in a single drainage basin
will provide increased redundancy and
reduce the likelihood of extirpation. We
consider a particular basin or
management area 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. We only
consider roundtail chub to be stablesecure in one stream, Fossil Creek.
In general, Arizona is an arid State;
about one-half of Arizona receives less
than 10 in. (25 cm) of rain a year.
Dewatering and other forms of habitat
loss have resulted in fragmentation of
roundtail chub populations. We
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anticipate that water demands from a
rapidly increasing human population
may further reduce habitat available to
this species, and could further fragment
populations. In examining the
relationship between species
distribution and extinction risk in
southwestern fishes, Fagan et al. (2002,
p. 3250) found that the number of
occurrences or populations of a species
is less significant a factor in determining
extinction risk than is habitat
fragmentation. Fragmentation of habitat
may also cause the roundtail chub to be
vulnerable to extinction from threats of
further habitat loss and competition
from nonnative fish because
immigration and recolonization from
adjacent populations is less likely. The
risk of extirpation of individual
populations of this species appears to be
quite high given the degree of
fragmentation (Fagan et al. 2002, p.
3254), that only one population is
considered stable and secure, and that
many threats are predicted to increase
in severity in the future.
Climate Change
Several recent studies predict
continued drought in the southwestern
United States, including the lower
Colorado River basin, due to global
climate change. Seager et al. (2007, pp.
1181–1184) analyzed 19 different
computer models of differing variables
to estimate the future climatology of the
southwestern United States and
northern Mexico in response to
predictions of changing climatic
patterns. All but one of the 19 models
predicted a drying trend within the
Southwest (Seager et al. 2007, p. 1181).
A total of 49 projections were created
using the 19 models, and all but 3
predicted a shift to increasing aridity
(dryness) in the Southwest as early as
2021–2040 (Seager et al. 2007, p. 1181).
Recently published projections of
potential reductions in natural flow in
the Colorado River basin by the mid21st century range from approximately
45 percent by Hoerling and Eischeid
(2006, p. 3989) to approximately 6
percent by Christensen and Lettenmaier
(2006, pp. 3727–3729). The U.S. Climate
Change Science Program recently
completed a report entitled ‘‘Abrupt
Climate Change, A report by the U.S.
Climate Change Science Program and
the Subcommittee on Global Change
Research’’ (U.S. Climate Change Science
Program 2008a). Regarding the
southwest United States, the summary
and findings concluded: ‘‘Climate
model studies over North America and
the global subtropics indicate that
subtropical drying will likely intensify
and persist in the future due to
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greenhouse warming. This drying is
predicted to move northward into the
southwestern United States. If the
model results are correct, then the
southwestern United States may be
beginning an abrupt period of increased
drought’’ (U.S. Climate Change Science
Program 2008b, p. 2).
If predicted effects of climate change
result in persistent drought conditions
in the Colorado River basin similar or
worse than those seen in recent years,
water resources will become
increasingly taxed as supplies dwindle
and demand stays the same or increases.
Likewise, there would be increased
demand on surface and groundwater
supplies in Arizona. Clearly, permanent
water is crucial for the continued
survival of native fish in the region,
including roundtail chub. Essentially
the entire range of the roundtail chub in
the lower Colorado River basin is
predicted to be at risk of becoming more
arid (Seager et al. 2007, pp. 1183–1184),
which has severe implications to the
integrity of aquatic and riparian
ecosystems and the water that supports
them. Perennial streams in the region
may become intermittent and streams
that are currently intermittent may
become unsuitable or dry completely.
Changes to climatic patterns may
warm water temperatures, alter stream
flow events, and increase demand for
water storage and conveyance systems
(Rahel and Olden 2008, pp. 521–522).
Warmer water temperatures across
temperate regions are predicted to
expand the distribution of existing
aquatic nonnative species by providing
31 percent more suitable habitat for
aquatic nonnative species. This
conclusion is based upon studies that
compared the thermal tolerances of 57
fish species with predictions made from
climate change temperature models
(Mohseni et al. 2003, p. 389). Eaton and
Scheller (1996, p. 1111) reported that
while several cold-water fish species in
North America are expected to have
reductions in their distribution from
effects of climate change, several
warmwater fish species are expected to
increase their distribution. In the
southwestern United States, this
situation may occur where water
persists but water temperature warms to
a level suitable for nonnative species
that were previously physiologically
precluded from occupation of these
areas. Species that are particularly
harmful to roundtail chub populations
such as the green sunfish, channel
catfish, largemouth bass, and bluegill
are expected to increase their
distribution by 7.4 percent, 25.2
percent, 30.4 percent, and 33.3 percent,
respectively (Eaton and Scheller 1996,
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p. 1111). Rahel and Olden (2008, p. 526)
expect that increases in water
temperatures in drier climates such as
the southwestern United States will
result in periods of prolonged low flows
and stream drying. These effects from
changing climatic conditions may have
profound effects on the amount,
permanency, and quality of habitat for
the roundtail chub. Warmwater
nonnative species such as red shiner,
common carp, mosquitofish, and
largemouth bass are expected to benefit
from prolonged periods of low flow
(Rahel and Olden 2008, p. 527).
Rahel et al. (2008, p. 551) examined
climate change models, nonnative
species biology, and ecological
observations, and concluded that
climate change could foster the
expansion of nonnative aquatic species
into new areas, magnify the effects of
existing aquatic nonnative species
where they currently occur, increase
nonnative predation rates, and heighten
the virulence of disease outbreaks in
North America. Many of the nonnative
species have similar, basic ecological
requirements as our native species, such
as the need of nonnative fish species for
permanent or nearly permanent water.
Rahel et al. (2008, pp. 554–555; and
from Carveth et al. 2006, p. 1435) found
that climate change will likely favor
nonnative fish species such as
largemouth bass, yellow bullhead, and
green sunfish over roundtail chub, in
part because they have higher
temperature tolerances. Also, drying of
stream channels will create less habitat
and greater competition due to limited
space and habitat. Thus climate change
can eliminate roundtail chub habitat
through at least two mechanisms:
directly, by drying up aquatic habitats
due to decreases in precipitation and
stable or increasing human demand for
water resources; and indirectly by
improving conditions for nonnative
species, increasing their proliferation,
and thereby increasing the threat from
nonnative fish predation and
competition.
Rahel et al. (2008, p. 555) also noted
that climate change could facilitate
expansion of nonnative parasites. This
could be an important threat to
roundtail chub. Optimal Asian
tapeworm development occurs at 25–30
°C (77–86 °F) (Granath and Esch 1983,
p. 1116), and optimal anchorworm
temperatures are 23–30 °C (73–86 °F)
(Bulow et al. 1979, p. 102). Cold water
temperatures in parts of the range of the
roundtail chub may have prevented
these parasites from completing their
life cycles and limited their distribution.
Warmer climate trends could result in
warmer overall water temperatures,
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increasing the prevalence of these
parasites.
The effects of the water withdrawals
discussed above may be exacerbated by
the current, long-term drought facing
the arid southwestern United States.
Philips and Thomas (2005, pp. 1–4)
provided streamflow records that
indicate that the drought Arizona
experienced between 1999 and 2004
was the worst drought since the early
1940s and possibly earlier. The Arizona
Drought Preparedness Plan Monitoring
Technical Committee (2008) assessed
Arizona’s drought status through June of
2008 in watersheds where the roundtail
chub occurs or historically occurred.
They found that the Verde and San
Pedro watersheds continue to
experience moderate drought (Arizona
Drought Preparedness Plan Monitoring
Technical Committee 2008), and the
Salt, Upper Gila, Lower Gila, and Lower
Colorado watersheds were abnormally
dry (Arizona Drought Preparedness Plan
Monitoring Technical Committee 2008).
Ongoing drought conditions have
depleted recharge of aquifers and
decreased baseflows in the region.
While drought periods have been
relatively numerous in the arid
Southwest from the mid-1800s to the
present, the effects of human-caused
impacts on riparian and aquatic
communities may compromise the
ability of these communities to function
under the additional stress of prolonged
drought conditions.
Conservation Agreements
As discussed in the ‘‘Conservation
Actions Relevant to Factor A’’ section
above, there are three wide-ranging
plans that address the ongoing
conservation of the roundtail chub. The
Utah Department of Natural Resources’
Range-wide Agreement was finalized
and signed by all the Colorado River
basin States in 2004. The Range-wide
Agreement depends heavily on
individual State plans for its
implementation. The objectives of the
Range-wide Agreement are to:
(A) Establish or maintain populations
sufficient to ensure the conservation of
each species within the State;
(B) Establish or maintain sufficient
connectivity between populations so
that viable metapopulations are
established or maintained;
(C) As feasible, identify, significantly
reduce or eliminate threats to the
conservation of these species.
To meet its obligations under the
Range-wide Agreement, New Mexico
completed a recovery plan for the
roundtail chub in November of 2006,
the ‘‘Colorado River Basin Chubs
Recovery Plan’’ (New Mexico Plan)
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(Carman 2006, p. 39). The New Mexico
Plan includes a management strategy
with the goal of establishing roundtail
chub populations that are secure and
self-sustaining throughout their
historical ranges in New Mexico, and
the objective for at least one sufficient,
self-sustaining, secure population of
roundtail chub in the mainstem of the
Gila River in New Mexico (Carman
2006, p. 49). The New Mexico Plan
management strategy also includes
specific and comprehensive
management issues and strategies with
corresponding implementation tasks
and a timeline for completion. The
implementation tasks provide a
comprehensive list of conservation
measures including: compiling
information on status and potential
habitat; improving knowledge of
historical and current population
dynamics; creating refuge populations
of chub lineages; restoring and securing
habitats; if necessary, augmenting
populations; if possible, establishing
additional populations; restricting
angling take of headwater chub;
controlling nonnative species;
identifying and reducing information
gaps; and establishing agreements and
partnerships to implement the plan
(Carman 2006, pp. 55–57). Actions
taken to date in implementation of the
New Mexico Plan include the creation
of a new refuge population of roundtail
chub at the Conservancy’s Gila River
Preserve farm pond in 2008 using
offspring of wild-caught Verde River
fish from the AGFD Bubbling Ponds
Fish Hatchery. The NMDGF plans to
complete health and genetic studies on
these fish, and if appropriate, their
offspring will be stocked into the
mainstem Gila River in New Mexico.
The NMDGF has also been working with
partners to secure habitat through
purchases and land management. In
2007, the Department and the
Conservancy purchased 168 ac (68 ha)
of riparian and river habitat in the GilaCliff Valley.
The goal of the Arizona Agreement is
to ensure the conservation of roundtail
chub, headwater chub, flannelmouth
sucker, Little Colorado River sucker,
bluehead sucker, and Zuni bluehead
sucker populations throughout Arizona.
The Arizona Agreement’s objective is to
address and ameliorate the five listing
factors in accordance with section
4(a)(1) of the Act; the Arizona
Agreement objectives also correspond to
those in the Range-wide Agreement (see
above). The Arizona Agreement
includes a strategy that is
comprehensive and includes numerous
conservation strategy tasks. Key tasks
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include: create a management plan;
create a Statewide management team;
conduct status assessments; identify
threats; conduct research; secure,
enhance, maintain, and create habitat;
manage detrimental nonnative fish/
aquatic species; manage the spread of
infectious diseases and parasites;
enhance or restore connectedness and
opportunities for migration; create,
maintain and evaluate fish refugia;
establish and enhance populations;
monitoring; and outreach (AGFD 2006a,
pp. 45–52). The Arizona Agreement also
includes success criteria, including:
population stability criteria for sizes and
numbers of populations to maintain
roundtail chub; threat reduction success
criteria, to determine if threats have
been adequately mitigated or
eliminated, and monitoring to evaluate
status and trend of populations, and
determine if habitat is being adequately
maintained.
AGFD has established a Statewide
Management Team to implement the
Arizona Agreement; signatories include
the Bureau of Reclamation, the Hualapai
Tribe; SRP; BLM; the Arizona State
Lands Department; the Arizona
Department of Water Resources; the
Conservancy; the Forest Service; and the
Fish and Wildlife Service. Under the
Arizona Agreement, AGFD and its
partners have implemented several
conservation actions that have benefited
the roundtail chub, including stocking
roundtail chub into two new habitats
that are free from nonnative fishes,
Roundtree Canyon and Ash Creek.
These stockings are too new to evaluate
whether roundtail chub has become
established, but if successful, these
efforts will help conserve the species by
creating two new populations that are
largely free from significant threats.
AGFD plans to establish another new
population of roundtail chub in
Houston Creek in 2009. AGFD is also
working with various partners to
develop operating criteria for Alamo
Dam on the Bill Williams River to
conserve roundtail chub, and is
finalizing broodstock and fishery
management plans, which will guide
the maintenance and propagation of
different stocks for use in restoration of
populations throughout the range of the
DPS and management of individual
population units, management areas,
and conservation units.
The Range-wide Agreement and the
Arizona Agreement depend on goodfaith efforts from signatories for their
implementation, and identify the need
to develop funding sources for their
implementation. Likewise, the New
Mexico Plan commits to using existing
resources and funding sources, to the
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32379
extent possible, to implement the plan,
and also identifies the need for
additional sources for full
implementation. No funding agreements
are in place to support these efforts.
Although a few conservation actions
have been implemented to benefit
roundtail chub, as discussed above, the
Range-wide Agreement, the Arizona
Agreement, and the New Mexico Plan,
and their comprehensive lists of tasks,
which if fully implemented would
significantly aid in the conservation of
roundtail chub, are in the early stages of
implementation at this point in time.
Specific actions identified in these
plans, either planned or implemented,
that address individual threats are
identified in Factors A to E as
appropriate.
The Arizona Agreement has resulted
in two new populations of roundtail
chub, one in a 1.2-mi (2-km) tributary to
the Verde River, Roundtree Canyon, and
one in a 0.6-mi (1-km) tributary of the
Salt River, Ash Creek. These
translocations are too new to evaluate
their success, having been completed in
2008 and 2007 respectively, but they
could potentially benefit the species.
AGFD is also planning to execute a
translocation into a second tributary of
the Verde River, Houston Creek, on the
Tonto National Forest, in 2009. Another
conservation measure being undertaken
as a result of the conservation
agreements is the establishment of
refuge populations and broodstock.
Refuge or sanctuary populations have
proven to be important in the
conservation of native fish in the
Southwest by creating predator-free
habitats (Mueller 2008), and use of
broodstock populations has prevented
the extinction of bonytail (Hedrick et al.
2000). AGFD has developed broodstock
management plans for the Verde River
and Chevelon Creek (Cantrell 2009, p.
5). Refuge populations provide both
broodstock and a secure population to
preserve the genetic integrity of a
population. AGFD and the NMDGF
recently created a refuge population in
New Mexico at the Conservancy Gila
River Preserve refuge pond near the Gila
River. AGFD has also created a refuge at
the Southwest Academy on Wet Beaver
Creek near Camp Verde, Arizona. Both
of these refuges were created with Verde
River broodstock from a broodstock
population at the AGFD Bubbling Ponds
fish hatchery. AGFD plans to create
additional refuge/broodstock
populations for other conservation
management units, with a minimum of
one for each management area (Cantrell
2009, p. 5).
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Conservation Actions Relevant to
Factor E
The Arizona Agreement includes
provisions to address the threat of
population fragmentation, identifying
the need to maintain connectivity, or at
least gene flow, even by artificial means,
between populations. If connectivity
between occupied habitats cannot be
maintained via natural connection, the
Arizona Agreement recommends
considering the practice of moving
individuals of the subject species
between fragmented populations.
Further, reducing existing stressors by
implementing the conservation
agreements will give existing
populations additional resiliency to face
the stresses presented by climate
change.
Summary of Factor E
Threats to roundtail chub are
magnified by the fragmentation of
existing populations. All but one model
evaluating changing climatic patterns
for the southwestern United States and
northern Mexico predict a drying trend
for the region (Seagar et al. 2007, pp.
1181–1184). We acknowledge that
drought and the loss of surface water in
riparian and aquatic communities are
related to changing climatic conditions
(Seagar et al. 2007, pp. 1181–1184). The
extent to which changing climate
patterns will affect the roundtail chub is
not known with certainty at this time.
However, threats to the roundtail chub
identified in Factors A and C will likely
be exacerbated by changes to climatic
patterns in the southwestern United
States due to increasing drought and
reduction of surface waters if the
predicted patterns are realized.
Conservation agreements and associated
plans have been developed for roundtail
chub in the lower Colorado River basin,
and some actions have been
implemented as a result that benefit and
help conserve the roundtail chub, such
as the establishment of new populations
in nonnative fish-free habitats and the
development of broodstock for use in
establishing and augmenting
populations. These plans also include
numerous actions to help reduce the
threats to the roundtail chub. While we
recognize the importance of working
with our partners in conserving the
roundtail chub through the
implementation of these plans, and
recognize that if implemented, they will
greatly assist in the conservation of
roundtail chub, these agreements have
only recently been completed and are in
the early stages of implementation.
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Summary of Status and Threats
The following discussion illustrates
how the threats to the species have
affected and are affecting the roundtail
chub across the DPS. Based on museum
records documented in Voeltz (2002,
Appendices), we suspect that the
roundtail chub retained much of its
historical distribution in the lower
Colorado River basin within the United
States up to and likely through the
1920s. Activities such as the
construction of dams and water
diversions that occurred throughout the
early to mid-1900s for agriculture and
regional economic development likely
eliminated surface flow throughout
stream reaches with occupied habitat,
which led to widespread extirpations of
roundtail chub populations in areas
such as the lower Gila and Salt Rivers
in Arizona. After the period of dam
construction and the subsequent
creation of reservoirs, widespread
nonnative fish stocking efforts ensued
throughout Arizona beginning in mid
1900s. The effects from this influx of
nonnative species throughout the
Southwest resulted in significant
declines in native fish and ranid frog
distribution and abundance, and the
subsequent listing of 19 of Arizona’s 31
native fish species throughout the last
35 years (see discussion in the
‘‘Nonnative Species’’ section above).
Currently, there are three specific
Management Areas of the DPS.
Management Area A contains three river
basins with the same lineage of
roundtail chub: The Gila, Salt, and
Verde Rivers (Dowling et al. 2008).
However, these three basins have very
limited connectivity between them
today, and the status of each basin may
best be described separately. We will
therefore discuss each of these river
basins separately to better understand
the status of the Management Area.
The roundtail chub populations in the
Verde River basin have the best
hydrological connectivity between
populations of any basin and the only
‘‘stable-secure’’ population, in Fossil
Creek (Table 2). However, the Verde
River is fragmented due to the presence
of Horseshoe and Bartlett reservoirs.
Fossil Creek was restored in 2004, and
has been stocked with native fishes
including roundtail chub. Of the other
five natural populations in the Verde
River, one is extirpated, two are ‘‘stablethreatened’’ and two are ‘‘unstablethreatened.’’ Reproduction and
recruitment is documented in the two
‘‘stable-threatened’’ populations, but
even in these, appears sporadic over
time (Brouder et al. 2001, p. 9). As
discussed above (see the Summary of
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Factors Affecting the Species section),
the Verde River is experiencing threats
from numerous land uses, especially
water withdrawal with increasing
demand for the Big Chino aquifer, the
source of the Verde River. Nonnative
species are present in all populations
with the exception of Fossil Creek.
Throughout the Verde River basin,
populations seem at risk of not
achieving long-term persistence due to
threats, as only sporadic recruitment
documented.
The Salt River populations are
difficult to assess due to land
ownership. The success of Tribal
fisheries management plans is
uncertain. The San Carlos Apache Tribe
Fisheries Management Plan is complete,
but the species has limited occurrence
on that reservation. The White
Mountain Apache Tribe has begun work
on a fisheries management plan, which
is not yet complete. Tribal management
affects all but two populations in the
Salt River basin. Of the two completely
non-Tribal populations, one is ‘‘stablethreatened’’ and one is ‘‘unstablethreatened.’’ Cherry Creek, the lone
‘‘stable-threatened’’ population, is
disconnected from other populations in
the Management Area, and a single
stochastic event, such as wildfire, which
has recently affected nearby
populations, could eliminate the
population.
The roundtail chub populations in the
Gila River are almost completely
extirpated, with the only ‘‘stablethreatened’’ population in Aravaipa
Creek. Aravaipa Creek is protected by
fish barriers, erected by the Bureau of
Reclamation as a result of the CAP
biological opinions (Service 2001,
2008). Thus the roundtail chub in
Aravaipa Creek has also benefited from
its co-occurrence with the Federally
listed spikedace and loach minnow.
Aravaipa Creek has also benefitted from
other conservation actions, including
those undertaken through conservation
agreements, such as actions of the
Conservancy taken for its protection,
discussed above (see Conservation
Actions Relevant to Factor A). But
nonnative fish species do occur above
the barrier in Aravaipa Creek and could
conceivably spread. The only other
populations in the Management Area
are Eagle Creek and the upper Gila River
in New Mexico. Roundtail chub in both
of these locations has become very rare
in recent years (Carman 2006, p. 7;
Cantrel 2009, p. 9). Both of these
populations are subject to numerous
threats, including abundant nonnative
species and dewatering due to ongoing
mining operations and potential water
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projects resulting from recent water
rights settlements.
Management Area A is thus at a high
risk of extirpation for several reasons.
The management area is made up of
fractured basins, the Gila, Salt, and
Verde Rivers. Many populations have
been extirpated, and roundtail chub in
Eagle Creek and the Upper Gila River
has become very rare. A number of
populations are on Tribal lands and are
difficult to evaluate in terms of status
and future management. Two
populations are fairly well protected
and have a stable status, Fossil and
Aravaipa Creeks. However, these two
locations are no longer connected, and
we find that their current status is
largely due to special management
resulting from their co-occurrence with
already listed fish species. All of the
other populations apart from Fossil and
Aravaipa Creeks in Management Area A
are likely at significant risk from Factors
A and C, and in particular, predation
from nonnative fish species and
dewatering.
Management Area B is the Bill
Williams River Basin. Streams in the
Bill Williams Management Area are
highly fragmented and subject to
summer drying, even under normal
conditions, because the area is in the
driest part of the DPS (Green and Sellers
1964, Figs. 3–5). It is likely that all
populations in Management Area B are
fragmented and isolated during the dry
season. Remaining populations face
increasing groundwater development
particularly in the Boulder Creek subbasin, and in Kirkland Creek in
particular. Only four of the nine extant
populations are ‘‘stable-threatened’’ and
those are in isolated portions of the
drainage. Trout Creek is completely
isolated, and the Big Sandy River is
extirpated. The Burro Creek drainage,
which includes Boulder and Conger
Creeks, has some redundancy, but
effluent from mining operations and the
presence of green sunfish, red shiner,
and yellow bullhead in Boulder Creek
pose a threat to these populations. The
Santa Maria sub-basin contains three
populations, including Kirkland and
Sycamore Creeks, all of which are
considered ‘‘unstable-threatened’’ and at
risk from increased groundwater
pumping and the presence of nonnative
fish species. According to AGFD, these
streams may dry completely in drought
and are more vulnerable to the effects of
climate change (A. Clark, AGFD, pers.
comm. 2009). Thus, Management Area B
is a collection of highly isolated,
threatened populations, in a very dry
region of the DPS.
Management Area C is the Little
Colorado River Basin. Only two
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populations remain: Clear Creek (East
Clear Creek) and Chevelon Creek. Both
are ‘‘unstable-threatened.’’ Recent
surveyors have commented with
surprise that these populations persist.
For example, Clarkson and Marsh
(2005b, p. 9) remarked that the
occurrence of roundtail chub and
juvenile roundtail chub in Clear Creek
was shocking given the lack of
occurrence in surveys a year before, and
especially given the co-occurrence and
dominance of nonnative fish species in
the area. The authors would not even
speculate on why this rare situation
existed, but noted that in similar
situations in the Southwest, ‘‘natives
eventually decline and succumb in the
presence of nonnative fish populations
(Marsh and Pacey 2005).’’ Further, they
found that other natives including
speckled dace (Rhinichthys osculus),
bluehead sucker, and Little Colorado
spinedace (Lepidomeda vittata) were
absent from Clear Creek, which
Clarkson and Marsh (2005b, p. 9) state
‘‘is likely testament to the continuing
deterioration of the native fish fauna in
this area.’’ Threats to these two
populations include both nonnative
species and water use. The aquifer that
feeds these streams in their lower
reaches has recently been the subject of
study for its use as a water supply for
nearby mining operations and future
development in towns of the region
such as Flagstaff, Winslow, and
Holbrook. Therefore, further strain on
these systems from increased surface
and groundwater diversions is likely. Of
the three management areas,
Management Area C appears to be the
most threatened and has the poorest
status. Given the lack of redundancy
and resiliency in these populations, the
loss of the two populations seems very
likely in the near future without
aggressive conservation to reduce
threats.
Foreseeable Future
The Act does not define the term
‘‘foreseeable future.’’ However, in a
January 16, 2009, memorandum
addressed to the Acting Director of the
U.S. Fish and Wildlife Service, the
Office of the Solicitor, Department of
the Interior, concluded, ‘‘* * * as used
in the [Act], Congress intended the term
‘foreseeable future’ to describe the
extent to which the Secretary can
reasonably rely on predictions about the
future in making determinations about
the future conservation status of the
species.’’ In discussing the concept of
foreseeable future for the lower
Colorado River basin DPS of the
roundtail chub, we considered: (1) The
biological and demographic
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characteristics of the species (such as
generation times, population genetics,
trends in evidence of recruitment within
current populations, etc.); (2) our ability
to predict or extrapolate the effects of
threats facing the DPS into the future;
and (3) the relative permanency or
irreversibility of these threats.
Of the threats to the roundtail chub
described in our analysis, the threats of
habitat loss and nonnative species are
the most significant. Habitat loss has
resulted in the loss of large sections of
the species’ former range in the lower
Colorado River basin because suitable
habitat is now gone or so altered as to
be permanently unsuitable, and the
same land use practices that have led to
this habitat loss are still occurring
throughout the range of the DPS and
therefore continue to constitute a
significant threat. The threat of habitat
loss is likely to not only continue in the
future but increase in severity given the
environmental changes resulting from
climate change and increasing human
populations. The widespread,
imminent, and serious threat to the
long-term sustainability of roundtail
chub in the lower Colorado River basin
from the presence of nonnative aquatic
species, especially nonnative fishes,
compounds the threat of habitat loss.
The elimination of the single threat of
nonnative species, especially fishes,
may lessen the severity of all other
threats. We find that because of the
potential for habitat loss due to various
land uses, in particular dewatering, the
presence of significant levels of
nonnative fish in all but one population,
and the extent of threats and lack of
stability to populations throughout the
lower Colorado River basin, the viability
of the DPS is in question into the
foreseeable future.
In response to the impacts to the
roundtail chub discussed above and in
our analysis of threats, the roundtail
chub in the lower Colorado River basin
has been eliminated from approximately
68 to 82 percent of its historical range
over the last 80 years (Voeltz 2002, p.
83). The most significant period of
declines and subsequent extirpations of
entire populations of roundtail chub
likely coincided with the proliferation
of nonnative species beginning in the
1940s and 1950s, most notably with the
widespread introduction and expansion
of nonnative fish such as common carp,
largemouth bass, green sunfish, and
channel and flathead catfish. In some
areas, the presence of these nonnative
species appears to be limiting
recruitment of roundtail chub, with only
large adults encountered during surveys
(Cantrell 2009, p. 10).
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Voeltz (2002, p. 5) defined ‘‘unstablethreatened’’ populations of roundtail
chub as those which exhibited over the
past 5–10 years a declining population
with limited recruitment, and noted 13
such populations. Specific instances of
apparent recruitment failure have been
noted in the Verde and Salt Rivers, and
in Wet Beaver Creek (Girmendonk and
Young 1997, pp. 21, 25, 34; Voeltz 2002,
p. 71; Bryan and Hyatt 2004, p. 3).
Based on the best available information,
we consider 13 populations to be
lacking recruitment, and are thus
‘‘unstable-threatened.’’ Also, there are
nine populations for which we have
limited status information and must
consider ‘‘unknown.’’ Since roundtail
chubs appear to live 5 to 7 years
(Bestgen 1985, pp. 72–75; Brouder et al.
2000, p. 10; Brouder 2005, p. 866), total
recruitment failure over a 10-year
timeframe could extirpate a population.
Because this is a relatively short period
of time (compared to longer-lived
species like the razorback sucker or
bonytail), recruitment failure may be
difficult to detect without significant
monitoring efforts. Recruitment failure
is particularly apparent in areas where
habitat remains structurally intact, but
where nonnative species maintain stable
populations and native species persist at
low levels. In Fossil Creek, a restoration
effort in 2004 created a nonnative fish
barrier and renovated 9.5 mi (15.3 km)
of stream (U.S. Forest Service 2004, p.
9), which removed all nonnative fish
species, which were previously
abundant, from Fossil Creek. Roundtail
chub abundance increased dramatically
after the restoration effort, illustrating
clearly the significance of predation by
and competition from nonnative fish
species on limiting recruitment and
abundance of the chub populations
(Marks et al. in press, pp. 22–24). The
observed effects of nonnative species on
age-class distribution and recruitment
are an important influence on the
maintenance of current populations to
be considered in our evaluation of the
foreseeable future for this species.
Predicting how current populations
will fare over time is confounded by a
lack of monitoring data and population
and survivorship estimates. Although
roundtail chub has persisted in many
currently occupied locations for some
time, there is little information on status
over time, with often only one or two
surveys to determine status. There is no
status information available for one
third of the populations. Of the
remainder, many appear to be in a
downward trend. Voeltz (2002) found
that roundtail chub was extirpated from
the Little Colorado River, Bill Williams
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River, Big Sandy River, Lower Gila
River, San Pedro River, San Francisco
River, Dry Beaver Creek, Zuni River,
and Blue River (Voeltz 2002; see Table
2). All of these extirpated populations
experienced reductions in flow, and
many of the remaining populations are
subjected to this threat. All of the
remaining established populations are
also subject to the threat of nonnative
species with the exception of Fossil
Creek, Ash Creak, and Roundtree
Canyon. Generally, population trends
appear to be declining throughout the
lower Colorado River basin (Voeltz
2002, p. 85; Cantrell 2009, pp. 10–11).
Few efforts specifically examining trend
have been conducted; two population
estimate studies conducted for the
species in the lower Colorado River
basin indicated a declining trend
(Brouder et al. 2000, p. 8–9; Bryan and
Hyatt 2004, p. 3). For the lone ‘‘stablesecure’’ population, a recently
completed study of Fossil Creek
indicates a significant increase in
abundance of roundtail chub as a result
of flow increases and nonnative species
removal (Marks et al. in press).
We conclude that remaining
populations are subject to a high risk of
extirpation, given that: (1) Roundtail
chub have a relatively high risk of
localized extirpation due to habitat
fragmentation (Fagan et al. 2002, p.
3254); (2) remaining populations are
highly vulnerable to the effects of
threats discussed in detail in Factors A
through E above; (3) the significant
threat of predation from nonnative fish
species; (4) nonnative species show an
alarming trend of eventually completely
overtaking native species where they cooccur (Marsh and Pacey 2005, p. 59); (5)
all but three existing established
population of roundtail chub is believed
to contain nonnative fish species (Voeltz
2002); (6) the few existing studies of
population trend and overall status
assessments indicate a continuing
decline in abundance, likely due to low
recruitment as a result of predation from
nonnative fishes (Voeltz 2002, pp. 83–
88; Bryan and Hyatt, 2004, pp. 3, 12–
13); and (7) many threats are projected
to increase over time, including those
most detrimental to the long-term
viability of the DPS, such as the
continued proliferation of nonnative
species, and projected increases in
human population and water use, both
of which are likely to be exacerbated by
the environmental effects resulting from
climate change.
Finding
We have carefully assessed the best
scientific and commercial information
available regarding the past, present,
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and future threats faced by the lower
Colorado River basin roundtail chub.
We reviewed the petition, information
available in our files, and other
published and unpublished information
submitted to us by the public following
our 90-day petition finding, and
consulted with recognized roundtail
chub experts and other Federal and
State resource agencies. On the basis of
the best scientific and commercial
information available, we find that the
population segment satisfies the
discreteness and significance elements
of the DPS policy, and therefore
qualifies as a DPS under our policy. We
further find that listing the lower
Colorado River basin DPS of roundtail
chub is warranted. However, listing the
lower Colorado River basin DPS of
roundtail chub is precluded by higher
priority listing actions at this time, as
discussed in the Preclusion and
Expeditious Progress section below.
In making this finding, we recognize
that there have been declines in the
distribution and abundance of the
roundtail chub, primarily attributed to
the introduction of and subsequent
predation by nonnative fishes, as
documented in the body of scientific
research on the distributions and impact
of introduced fishes in relation to the
roundtail chub. Direct predation by
nonnative fishes on this species has
resulted in rangewide population
declines and local extirpations. Because
nonnative species are present in all but
one of the remaining established
populations of this species, we conclude
that remaining populations are at risk of
declines and extirpation as a result of
predation by nonnative species.
Furthermore, the result of the past
effects of these threats is that many of
the remaining populations are
fragmented and isolated, making them
vulnerable to further declines and local
extirpations from other factors (Fagan et
al. 2002, p. 3250). Populations that go
extinct following habitat fragmentation
and population isolation are unlikely to
be naturally recolonized due to both the
isolation from, and lack of connectivity
to, potential source populations.
The isolation of remaining roundtail
chub populations and habitat
fragmentation as a result of nonnative
fish introductions and habitat alteration
has made remaining populations
vulnerable to extinction from stochastic
events. Stochastic events such as fire
have only recently been recognized as
an important factor in the decline of this
species (Dunham et al. 2003, p. 183;
Rinne 2004, p. 151). Other factors
include parasitism and the inadequacy
of existing regulatory mechanisms.
These factors may contribute to declines
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or extirpations of roundtail chub. In
addition, these factors are exacerbated
by the effects that have been caused by
nonnative fishes. Also, a significant new
threat appears to be environmental
changes that result from climate change,
which may have the potential to
drastically reduce existing habitat
through further stream dewatering, as
well as result in habitat change by, for
example, increasing water temperatures
that will aid the spread and
establishment of nonnative predators
and parasites.
A number of habitat altering land uses
further threaten remaining populations
of roundtail chub. These include dams,
diversions, and groundwater
withdrawal; livestock grazing; logging,
fuel wood cutting, mining, and
channelization; road construction, use,
and maintenance; urban and rural
development; recreation; and highintensity wildfires. These threats
negatively impact the rivers, streams,
and riparian habitats that are essential
for the survival of the roundtail chub.
These threats have been documented
historically, are either ongoing or likely
to occur throughout the range of the
roundtail chub in the lower Colorado
River basin, and will reduce the
suitability of roundtail chub habitat as
cover for protection from predators, as
a foraging area, and as spawning and
nursery areas. Despite the conservation
actions discussed above, the dewatering
of aquatic habitats in the arid lower
Colorado River basin poses a significant
threat to all native fish of the region,
including roundtail chub. All of these
threats are anthropogenic and can be
expected to continue, if not increase,
given the predictions for increases in
human population in the region.
Efforts to improve the status of the
roundtail chub in the lower Colorado
River basin began in earnest in 2006.
These conservation efforts, notably the
Arizona Agreement and New Mexico
Plan, include many actions to stabilize
populations, establish new populations,
increase the range of the species, and
ameliorate threats. The conservation
agreements have met with some success
in this regard. Two populations have
been created, as have two refuge
populations and a refuge-broodstock
population at a hatchery. Efforts to
purchase land and water rights to
reduce threats to habitat have met with
some limited success. These
conservation efforts can conserve the
roundtail chub if fully implemented.
Currently, however, they are in the early
stages of implementation.
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Preclusion and Expeditious Progress
Preclusion is a function of the listing
priority of a species in relation to the
resources that are available and
competing demands for those resources.
Thus, in any given fiscal year (FY),
multiple factors dictate whether it will
be possible to undertake work on a
proposed listing regulation or whether
promulgation of such a proposal is
warranted but precluded by higherpriority listing actions.
The resources available for listing
actions are determined through the
annual Congressional appropriations
process. The appropriation for the
Listing Program is available to support
work involving the following listing
actions: proposed and final listing rules;
90-day and 12-month findings on
petitions to add species to the Lists of
Endangered and Threatened Wildlife
and Plants (Lists) or to change the status
of a species from threatened to
endangered; annual determinations on
prior ‘‘warranted but precluded’’
petition findings as required under
section 4(b)(3)(C)(i) of the Act; proposed
and final rules designating critical
habitat; and litigation-related,
administrative, and program
management functions (including
preparing and allocating budgets,
responding to Congressional and public
inquiries, and conducting public
outreach regarding listing and critical
habitat). The work involved in
preparing various listing documents can
be extensive and may include, but is not
limited to: gathering and assessing the
best scientific and commercial data
available and conducting analyses used
as the basis for our decisions; writing
and publishing documents; and
obtaining, reviewing, and evaluating
public comments and peer review
comments on proposed rules and
incorporating relevant information into
final rules. The number of listing
actions that we can undertake in a given
year also is influenced by the
complexity of those listing actions; that
is, more complex actions generally are
more costly. For example, during the
past several years, the cost (excluding
publication costs) for preparing a 12month finding, without a proposed rule,
has ranged from approximately $11,000
for one species with a restricted range
and involving a relatively
uncomplicated analysis to $305,000 for
another species that is wide-ranging and
involving a complex analysis.
We cannot spend more than is
appropriated for the Listing Program
without violating the Anti-Deficiency
Act (see 31 U.S.C. 1341(a)(1)(A)). In
addition, in FY 1998 and for each fiscal
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32383
year since then, Congress has placed a
statutory cap on funds which may be
expended for the Listing Program, equal
to the amount expressly appropriated
for that purpose in that fiscal year. This
cap was designed to prevent funds
appropriated for other functions under
the Act (for example, recovery funds for
removing species from the Lists), or for
other Service programs, from being used
for Listing Program actions (see House
Report 105–163, 105th Congress, 1st
Session, July 1, 1997).
Recognizing that designation of
critical habitat for species already listed
would consume most of the overall
Listing Program appropriation, Congress
also put a critical habitat subcap in
place in FY 2002 and has retained it
each subsequent year to ensure that
some funds are available for other work
in the Listing Program: ‘‘The critical
habitat designation subcap will ensure
that some funding is available to
address other listing activities’’ (House
Report No. 107–103, 107th Congress, 1st
Session, June 19, 2001). In FY 2002 and
each year until FY 2006, the Service has
had to use virtually the entire critical
habitat subcap to address courtmandated designations of critical
habitat, and consequently none of the
critical habitat subcap funds have been
available for other listing activities. In
FY 2007, we were able to use some of
the critical habitat subcap funds to fund
proposed listing determinations for
high-priority candidate species. In FY
2008, while we were unable to use any
of the critical habitat subcap funds to
fund proposed listing determinations,
we did use some of this money to fund
the critical habitat portion of some
proposed listing determinations, so that
the proposed listing determination and
proposed critical habitat designation
could be combined into one rule,
thereby being more efficient in our
work. In FY 2009, we anticipate being
able to do the same.
Thus, through the listing cap, the
critical habitat subcap, and the amount
of funds needed to address courtmandated critical habitat designations,
Congress and the courts have in effect
determined the amount of money
available for other listing activities.
Therefore, the funds in the listing cap,
other than those needed to address
court-mandated critical habitat for
already listed species, set the limits on
our determinations of preclusion and
expeditious progress.
Congress also recognized that the
availability of resources was the key
element in deciding whether, when
making a 12-month petition finding, we
would prepare and issue a listing
proposal or instead make a ‘‘warranted
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but precluded’’ finding for a given
species. The Conference Report
accompanying Public Law 97–304,
which established the current statutory
deadlines and the warranted-butprecluded finding, states (in a
discussion on 90-day petition findings
that by its own terms also covers 12month findings) that the deadlines were
‘‘not intended to allow the Secretary to
delay commencing the rulemaking
process for any reason other than that
the existence of pending or imminent
proposals to list species subject to a
greater degree of threat would make
allocation of resources to such a petition
[that is, for a lower-ranking species]
unwise.’’
In FY 2009, expeditious progress is
that amount of work that can be
achieved with $8,808,000, which is the
amount of money that Congress
appropriated for the Listing Program
(that is, the portion of the Listing
Program funding not related to critical
habitat designations for species that are
already listed). Our process is to make
our determinations of preclusion on a
nationwide basis to ensure that the
species most in need of listing will be
addressed first and also because we
allocate our listing budget on a
nationwide basis. The $8,808,000 is
being used to fund work in the
following categories: compliance with
court orders and court-approved
settlement agreements requiring that
petition findings or listing
determinations be completed by a
specific date; section 4 (of the Act)
listing actions with absolute statutory
deadlines; essential litigation-related,
administrative, and listing program
management functions; and highpriority listing actions for some of our
candidate species. The allocations for
each specific listing action are identified
in the Service’s FY 2009 Allocation
Table (part of our administrative
record).
In FY 2007, we had more than 120
species with an LPN of 2, based on our
September 21, 1983, guidance for
assigning an LPN for each candidate
species (48 FR 43098). Using this
guidance, we assign each candidate an
LPN of 1 to 12, depending on the
magnitude of threats (high vs. moderate
to low), immediacy of threats (imminent
or nonimminent), and taxonomic status
of the species (in order of priority:
monotypic genus (a species that is the
sole member of a genus); species; or part
of a species (subspecies, distinct
population segment, or significant
portion of the range)). The lower the
listing priority number, the higher the
listing priority (that is, a species with an
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LPN of 1 would have the highest listing
priority). Because of the large number of
high-priority species, we further ranked
the candidate species with an LPN of 2
by using the following extinction-risk
type criteria: International Union for the
Conservation of Nature and Natural
Resources (IUCN) Red list status/rank,
Heritage rank (provided by
NatureServe), Heritage threat rank
(provided by NatureServe), and species
currently with fewer than 50
individuals, or 4 or fewer populations.
Those species with the highest IUCN
rank (critically endangered), the highest
Heritage rank (G1), the highest Heritage
threat rank (substantial, imminent
threats), and currently with fewer than
50 individuals, or fewer than 4
populations, comprised a list of
approximately 40 candidate species
(‘‘Top 40’’). These 40 candidate species
have had the highest priority to receive
funding to work on a proposed listing
determination. As we work on proposed
and final listing rules for these 40
candidates, we are applying the ranking
criteria to the next group of candidates
with LPN of 2 and 3 to determine the
next set of highest priority candidate
species.
To be more efficient in our listing
process, as we work on proposed rules
for these species in the next several
years, we are preparing multi-species
proposals when appropriate, and these
may include species with lower priority
if they overlap geographically or have
the same threats as a species with an
LPN of 2. In addition, available staff
resources are also a factor in
determining high-priority species
provided with funding. Finally,
proposed rules for reclassification of
threatened species to endangered are
lower priority, because as listed species,
they are already afforded the protection
of the Act and implementing
regulations.
We assigned the lower Colorado River
basin DPS of the roundtail chub an LPN
of 9, based on our finding that the
subspecies faces threats that are
imminent and of moderate magnitude,
including the present or threatened
destruction, modification or curtailment
of its habitat; the impacts of nonnative
species; and the inadequacy of existing
regulatory mechanisms. We consider the
threat magnitude moderate because,
while all populations are experiencing
threats, the populations occur in
multiple watersheds, and the threats
acting on the DPS are not occurring
uniformly throughout the range of the
species; therefore not all populations are
likely to be impacted simultaneously by
any of the known threats. Additionally,
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the existence of conservation
agreements has resulted in the
implementation of actions to improve
the status of the DPS and reduce the
severity of threats. We anticipate that
these conservation agreements will
continue to benefit the species with
additional actions to improve status and
reduce or eliminate threats. Although
implemented too recently to assess,
recent efforts to create new populations
of the DPS in relatively threat-free
habitats may prove to be successful, and
additional restoration efforts are being
planned.
We consider the threats imminent
because they are currently occurring in
all of the existing populations. Under
the 1983 Guidelines (48 FR 43098), a
subspecies or DPS receives a lower
priority than a full species and a full
species receives a lower priority than a
monotypic genus, thus a DPS facing
imminent moderate-magnitude threats
is assigned an LPN of 9. Therefore, work
on a proposed listing determination for
the lower Colorado River basin DPS of
roundtail chub is precluded by work on
higher priority candidate species (i.e.,
entities with LPN of 8 or lower); listing
actions with absolute statutory, court
ordered, or court-approved deadlines;
and final listing determinations for
those species that were proposed for
listing with funds from FY 2008. This
work includes all the actions listed in
the tables below under expeditious
progress.
As explained above, a determination
that listing is warranted but precluded
must also demonstrate that expeditious
progress is being made to add or remove
qualified species to and from the Lists
of Endangered and Threatened Wildlife
and Plants. (Although we do not discuss
it in detail here, we are also making
expeditious progress in removing
species from the list under the Recovery
program, which is funded by a separate
line item in the budget of the
Endangered Species Program. As
explained above in our description of
the statutory cap on Listing Program
funds, the Recovery Program funds and
actions supported by them cannot be
considered in determining expeditious
progress made in the Listing Program.)
As with our ‘‘precluded’’ finding,
expeditious progress in adding qualified
species to the Lists is a function of the
resources available and the competing
demands for those funds. Given that
limitation, we find that we are making
progress in FY 2009 in the Listing
Program. This progress included
preparing and publishing the following
determinations:
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FY 2009 COMPLETED LISTING ACTIONS
Publication date
Title
Actions
10/15/2008 ........
90-Day Finding on a Petition To List the Least
Chub
Listing 48 Species on Kauai as Endangered and
Designating Critical Habitat
90-Day Finding on a Petition to List the Sacramento Valley Tiger Beetle as Endangered
90-Day Finding on a Petition To List the Dusky
Tree Vole as Threatened or Endangered
12-Month Finding on a Petition To List the Northern Mexican Gartersnake as Threatened or
Endangered With Critical Habitat; Proposed
Rule
90-Day Finding on a Petition To List the Blacktailed Prairie Dog as Threatened or Endangered
90-Day Finding on a Petition To List the Sacramento Mountains Checkerspot Butterfly as
Endangered with Critical Habitat
90-Day Finding on a Petition to Change the Listing Status of the Canada Lynx
Partial 90-Day Finding on a Petition To List 475
Species in the Southwestern United States as
Threatened or Endangered With Critical Habitat
Partial 90-Day Finding on a Petition To List 206
Species in the in the Midwest and Western
United States as Threatened or Endangered
With Critical Habitat
90-Day Finding on a Petition To List the Wyoming Pocket Gopher as Threatened or Endangered With Critical Habitat
Listing Phyllostegia hispida as Endangered
Throughout Its Range
12-Month Finding on a Petition to List the Yellow-Billed Loon as Threatened or Endangered
12-Month Finding on a Petition to List the San
Francisco Bay-Delta Population of the Longfin
Smelt as Endangered
90-Day Finding on a Petition To List the
Tehachapi Slender Salamander as Threatened
or Endangered
90-Day Finding on a Petition To List the American Pika as Threatened or Endangered with
Critical Habitat
12-Month Finding on a Petition to List the Coaster Brook Trout as Endangered
90-Day Finding on a Petition to List Oenothera
acutissima as Threatened or Endangered
Notice of 90-day Petition Finding, Substantial .....
73 FR 61007–61015
Proposed Listing, Endangered; Proposed Critical
Habitat.
Notice of 90-day Petition Finding, Not substantial
73 FR 62591–62742
Notice of 90-day Petition Finding, Substantial .....
73 FR 63919–63926
Notice of 12-month petition finding, Warranted
but precluded.
73 FR 71787–71826
Notice of 90-day Petition Finding, Substantial .....
73 FR 73211–73219
Notice of 90-day Petition Finding, Substantial .....
73 FR 74123–74129
Notice of 90-day Petition Finding, Substantial .....
73 FR 76990–76994
Notice of 90-day Petition Finding, Not substantial
74 FR 419–427
Notice of 90-day Petition Finding, Not substantial
74 FR 6122–6128
Notice of 90-day Petition Finding, Substantial .....
74 FR 6558–6563
Final Listing Endangered ......................................
74 FR 11319–11327
Notice of 12-month petition finding, Warranted
but precluded.
Notice of 12-month petition finding, Not warranted.
74 FR 12931–12968
Notice of 90-day Petition Finding, Substantial .....
74 FR 18336–18341
Notice of 90-day Petition Finding, Substantial .....
74 FR 21301–21310
Notice of 12-month petition finding, Not warranted.
Notice of 90-day Petition Finding, Not substantial
74 FR 23376 23376–
23388
74 FR 27266–27271
10/21/2008 ........
10/24/2008 ........
10/28/2008 ........
11/25/2008 ........
12/02/2008 ........
12/05/2008 ........
12/18/2008 ........
1/06/2009 ..........
2/05/2009 ..........
2/10/2009 ..........
3/17/2009 ..........
3/25/2009 ..........
4/09/2009 ..........
4/22/2009 ..........
5/07/2009 ..........
5/-/2009 .............
6/09/2009 ..........
Our expeditious progress also
included work on listing actions, which
we funded in FY 2009 but have not yet
been completed to date. These actions
are listed below. Actions in the top
section of the table are being conducted
under a deadline set by a court. Actions
in the middle section of the table are
being conducted to meet statutory
timelines, that is, timelines required
under the Act. Actions in the bottom
section of the table are high priority
listing actions. These actions include
work primarily on species with an LPN
of 2, and selection of these species is
partially based on available staff
resources, and when appropriate,
include species with a lower priority if
FR pages
73 FR 63421–63424
74 FR 16169–16175
they overlap geographically or have the
same threats as the species with the
high priority. Including these species
together in the same proposed rule
results in considerable savings in time
and funding, when compared to
preparing separate proposed rules for
each of them in the future.
ACTIONS FUNDED IN FY 2009 BUT NOT YET COMPLETED
Species
Action
Actions Subject to Court Order/Settlement Agreement
Slickspot peppergrass ..............................................................................................................................................
Coastal cutthroat trout .............................................................................................................................................
Mono basin sage-grouse .........................................................................................................................................
Sacramento Mtns. checkerspot butterfly .................................................................................................................
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Final listing determination.
Final listing determination.
12-month petition finding.
12-month petition finding.
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ACTIONS FUNDED IN FY 2009 BUT NOT YET COMPLETED—Continued
Species
Action
SW Bald eagle population .......................................................................................................................................
Black-tailed prairie dog ............................................................................................................................................
Lynx (include New Mexico in listing.) ......................................................................................................................
White-tailed prairie dog ............................................................................................................................................
Big Lost River whitefish ...........................................................................................................................................
Hermes copper butterfly ..........................................................................................................................................
Thorne’s hairstreak butterfly ....................................................................................................................................
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
90-day petition finding.
90-day petition finding.
Actions With Statutory Deadlines
48 Kauai species .....................................................................................................................................................
Black-footed albatross .............................................................................................................................................
Mount Charleston blue butterfly ...............................................................................................................................
Goose Creek milk-vetch ..........................................................................................................................................
Mojave fringe-toed lizard 1 .......................................................................................................................................
Pygmy rabbit (rangewide) 1 ......................................................................................................................................
Kokanee—Lake Sammamish population 1 ..............................................................................................................
Ashy storm petrel .....................................................................................................................................................
Delta smelt (uplisting) ..............................................................................................................................................
Cactus ferruginous pygmy owl 1 ..............................................................................................................................
Tucson shovel-nosed snake 1 ..................................................................................................................................
Northern leopard frog ...............................................................................................................................................
Tehachapi slender salamander ...............................................................................................................................
Northern leopard frog ...............................................................................................................................................
4 subspecies of Pseudocopaeodes enunus ............................................................................................................
Southeastern pop snowy plover & wintering pop. of piping plover .........................................................................
Berry Cave salamander 1 .........................................................................................................................................
Ozark chinquapin 1 ...................................................................................................................................................
Smooth-billed ani .....................................................................................................................................................
Bay Springs salamander 1 .......................................................................................................................................
Mojave ground squirrel 1 ..........................................................................................................................................
Llanero coqui ...........................................................................................................................................................
Gopher tortoise—eastern population .......................................................................................................................
Mojave ground squirrel ............................................................................................................................................
Pacific walrus ...........................................................................................................................................................
32 species of snails and slugs ................................................................................................................................
Calopogon oklahomensis .........................................................................................................................................
Susan’s purse-making caddisfly ..............................................................................................................................
Striped newt .............................................................................................................................................................
American dipper—Black Hills population .................................................................................................................
Sprague’s pipit .........................................................................................................................................................
Southern hickorynut .................................................................................................................................................
5 Southwest mussel species ...................................................................................................................................
Sonoran desert tortoise ...........................................................................................................................................
Chihuahua scarfpea .................................................................................................................................................
Jemez Mtns. salamander .........................................................................................................................................
White-sided jackrabbit ..............................................................................................................................................
Wrights marsh thistle ...............................................................................................................................................
White-bark pine ........................................................................................................................................................
Puerto Rico harlequin ..............................................................................................................................................
Fisher—Northern Rocky Mtns. population ...............................................................................................................
42 snail species (Nevada & Utah) ...........................................................................................................................
HI yellow-faced bees ...............................................................................................................................................
206 species (partially completed) ............................................................................................................................
475 Southwestern species (partially completed) .....................................................................................................
Final listing determination.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
12-month petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
90-day petition finding.
High Priority Listing Actions 3
19 Oahu candidate species (16 plants, 3 damselflies) (15 with LPN = 2, 3 with LPN = 3, 1 with LPN = 9) ........
2 HI damselflies (LPN = 2) ......................................................................................................................................
17 Maui-Nui candidate species (14 plants, 3 tree snails) (12 with LPN = 2, 3 with LPN = 3, 3 with LPN = 8) ....
Sand dune lizard (LPN = 2) .....................................................................................................................................
2 Arizona springsnails (Pyrgulopsis bernadina (LPN = 2), Pyrgulopsis trivialis (LPN = 2)) ...................................
2 New Mexico springsnails (Pyrgulopsis chupaderae (LPN = 2), Pyrgulopsis thermalis (LPN = 11)) ...................
2 mussels (rayed bean (LPN = 2), snuffbox No LPN) ............................................................................................
2 mussels (sheepnose (LPN = 2), spectaclecase (LPN = 4),) ...............................................................................
Ozark hellbender 2 (LPN = 3) ..................................................................................................................................
3 southeast aquatic species 1 (Georgia pigtoe, interrupted rocksnail, rough hornsnail) (all with LPN = 2) ...........
Altamaha spinymussel (LPN = 2) ............................................................................................................................
5 southeast fish (rush darter (LPN = 2), chucky madtom (LPN = 2), yellowcheek darter (LPN = 2), Cumberland
darter (LPN = 5), laurel dace (LPN = 5)).
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Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
Proposed
listing.
listing.
listing.
listing.
listing.
listing.
listing.
listing.
listing.
listing.
listing.
listing.
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ACTIONS FUNDED IN FY 2009 BUT NOT YET COMPLETED—Continued
Species
Action
8 southeast mussels (southern kidneyshell (LPN = 2), round ebonyshell (LPN = 2), Alabama pearshell (LPN =
2), southern sandshell (LPN = 5), fuzzy pigtoe (LPN = 5), Choctaw bean (LPN = 5), narrow pigtoe (LPN =
11), and tapered pigtoe (LPN = 11)).
3 Colorado plants (Pagosa skyrocket (Ipomopsis polyantha) (LPN = 2), Parchute beardtongue (Penstemon
debilis) (LPN = 2), Debeque phacelia (Phacelia submutica) (LPN = 8)).
Casey’s june beetle (LPN = 2) ................................................................................................................................
Proposed listing.
Proposed listing.
Proposed listing.
1 Funds
for listing actions for these species were provided in previous FYs.
funded a proposed rule for this subspecies with an LPN of 3 ahead of other species with LPN of 2, because the threats to the species
were so imminent and of a high magnitude that we considered emergency listing if we were unable to fund work on a proposed listing rule in FY
2008.
3 Funds for these high priority listing actions were provided in FY 2008 and 2009.
2 We
We have endeavored to make our listing
actions as efficient and timely as possible,
given the requirements of the relevant law
and regulations, and constraints relating to
workload and personnel. We are continually
considering ways to streamline processes or
achieve economies of scale, such as by
batching related actions together. Given our
limited budget for implementing section 4 of
the Act, these actions described above
collectively constitute expeditious progress.
The lower Colorado River basin DPS
of roundtail chub will be added to the
list of candidate species upon
publication of this 12-month finding.
We will continue to monitor the status
of this species as new information
becomes available. This review will
determine if a change in status is
warranted, including the need to make
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prompt use of emergency listing
procedures.
We intend that any proposed listing
action for the lower Colorado River
basin DPS of roundtail chub will be as
accurate as possible. Therefore, we will
continue to accept additional
information and comments from all
concerned governmental agencies, the
scientific community, industry, or any
other interested party concerning this
finding.
References Cited
A complete list of all references cited
in this document is available upon
request from the Field Supervisor at the
Arizona Ecological Services Office (see
ADDRESSES section).
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Author
The primary authors of this document
are the staff members of the Arizona
Ecological Services Office (see
ADDRESSES section).
Authority
The authority for this action is the
Endangered Species Act of 1973, as
amended (16 U.S.C. 1531 et seq.).
Dated: June 24, 2009.
Marvin E. Moriarty,
Acting Director, U.S. Fish and Wildlife
Service.
[FR Doc. E9–15828 Filed 7–6–09; 8:45 am]
BILLING CODE 4310–55–P
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Agencies
[Federal Register Volume 74, Number 128 (Tuesday, July 7, 2009)]
[Proposed Rules]
[Pages 32352-32387]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-15828]
[[Page 32351]]
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Part V
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition To List a Distinct Population Segment of the Roundtail Chub
(Gila robusta) in the Lower Colorado River Basin; Proposed Rule
Federal Register / Vol. 74, No. 128 / Tuesday, July 7, 2009 /
Proposed Rules
[[Page 32352]]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[FWS-R2-ES-2009-0004; MO 92210530083-B2]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List a Distinct Population Segment of the Roundtail
Chub (Gila robusta) in the Lower Colorado River Basin
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
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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 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 listing action
is warranted, but precluded by higher priority actions to amend the
Lists of Endangered and Threatened Wildlife and Plants. Upon
publication of this 12-month petition finding, this species will be
added to our candidate species list. We will develop a proposed rule to
list this population segment of the roundtail chub pursuant to our
Listing Priority System. Any determinations on critical habitat will be
made at that time.
DATES: The finding announced in this document was made on July 7, 2009.
ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R2-ES-2009-0004. Supporting
documentation we used in preparing this finding is available for public
inspection, by appointment, during normal business hours at the U.S.
Fish and Wildlife Service, Arizona Ecological Services Office, 2321
West Royal Palm Road, Suite 103, Phoenix, AZ 85021-4951. Please submit
any new information, materials, comments, or questions concerning this
finding to the above address.
FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor,
Arizona Ecological Services Office (see ADDRESSES), telephone 602-242-
0210. If you use a telecommunications device for the deaf (TDD), please
call the Federal Information Relay Service (FIRS) at 800-877-8339.
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 Lists of Endangered and Threatened
Wildlife and Plants that contains substantial scientific or commercial
information that the action may be warranted, we make a finding within
12 months of the date of the receipt of the petition on whether the
petitioned action is: (a) Not warranted, (b) warranted, or (c)
warranted but the immediate proposal of a regulation implementing the
petitioned action is precluded by other pending proposals to determine
whether species are 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 we treat a petition for which the requested
action is found to be warranted but precluded as though resubmitted on
the date of such finding, that is, requiring a subsequent finding to be
made within 12 months. We must publish these 12-month findings in the
Federal Register.
Previous Federal Actions
In 1985, the roundtail chub (Gila robusta) was placed on the list
of candidate species as a category 2 species (50 FR 37958). Category 2
species were those for which existing information indicated that
listing was possibly appropriate, but for which substantial supporting
biological data were lacking. Due to lack of funding to gather existing
information on the roundtail chub, the species remained in category 2
through the 1989 (54 FR 554), 1991 (56 FR 58804) and 1994 (59 FR 58982)
candidate notices of review. In the 1996 candidate notice of review (61
FR 7596), category 2 was eliminated, and roundtail chub no longer had
formal status under the candidate identification system.
On April 14, 2003, we received a petition from the Center for
Biological Diversity requesting that we list a DPS of the roundtail
chub (Gila robusta) in the lower Colorado River basin (defined as all
waters tributary to the Colorado River in Arizona and the portion of
New Mexico in the Gila River and Zuni River basins) as endangered or
threatened, that we list the headwater chub (Gila nigra) as endangered
or threatened, and that we designate critical habitat concurrently with
the listing for both species.
Following receipt of the 2003 petition, and pursuant to a
stipulated settlement agreement, on July 12, 2005, we published our 90-
day finding that the petition presented substantial scientific
information indicating that listing the headwater chub and a DPS of the
roundtail chub in the lower Colorado River basin may be warranted, and
we initiated 12-month status reviews for these species (70 FR 39981).
On May 3, 2006, we published our 12-month finding that listing was
warranted for the headwater chub, but precluded by higher priority
listing actions, and that listing of a population segment of the
roundtail chub in the lower Colorado River basin was not warranted
because it did not meet our definition of a DPS (71 FR 26007).
On September 7, 2006, we received a complaint from the Center for
Biological Diversity for declaratory and injunctive relief, challenging
our decision not to list the lower Colorado River basin population of
the roundtail chub as an endangered species under the Act. On November
5, 2007, in a stipulated settlement agreement, we agreed to commence a
new status review of the lower Colorado River basin population segment
of the roundtail chub and to submit a 12-month finding to the Federal
Register by June 30, 2009. On March 3, 2009, we published a notice in
the Federal Register that we were initiating a status review and
soliciting new information for reevaluating the 2003 petition to list a
lower Colorado River basin DPS of the roundtail chub (74 FR 9205).
Defining a Species Under the Act
Section 3(16) of the Act defines ``species'' to include ``any
subspecies of fish or wildlife or plants, and any distinct population
segment of any species of vertebrate fish or wildlife which interbreeds
when mature'' (16 U.S.C. 1532(16)). Our implementing regulations at 50
CFR 424.02 provide further guidance for determining whether a
particular taxon or population is a species or subspecies for the
purposes of the Act: ``[T]he Secretary shall rely on standard taxonomic
distinctions and the biological expertise of the Department and the
scientific community concerning the relevant taxonomic group'' (50 CFR
424.11(a)). As previously discussed, the population segment of
roundtail chub in the lower Colorado River basin is classified as Gila
robusta, the same as other roundtail chub populations, and as such we
do not consider the population segment of roundtail chub in the lower
Colorado River basin to constitute a distinct species or subspecies.
Since the population segment of roundtail chub in the lower Colorado
River basin is not a
[[Page 32353]]
distinct species or subspecies, we then evaluated whether it is a
distinct population segment to determine whether it would constitute a
listable entity under the Act.
To interpret and implement the DPS provisions of the Act and
Congressional guidance, the Service and the National Marine Fisheries
Service (now the National Oceanic and Atmospheric Administration--
Fisheries), published the Policy Regarding the Recognition of Distinct
Vertebrate Population Segments Under the Endangered Species Act (DPS
Policy) in the Federal Register on February 7, 1996 (61 FR 4722). Under
the DPS Policy, three elements are considered in the decision regarding
the establishment and classification of a population of a vertebrate
species as a possible DPS. These are applied similarly for additions to
and removals from the Lists of Endangered and Threatened Species. These
elements are (1) the discreteness of a population in relation to the
remainder of the species to which it belongs, (2) the significance of
the population segment to the species to which it belongs, and (3) the
population segment's conservation status in relation to the Act's
standards for listing, delisting, or reclassification (i.e., is the
population segment endangered or threatened?).
Distinct Vertebrate Population Segment Analysis
In the 2003 petition, we were asked to consider listing a DPS for
the roundtail chub in the lower Colorado River basin (the Colorado
River and its tributaries downstream of Glen Canyon Dam including the
Gila and Zuni River basins in New Mexico). Per our November 5, 2007,
stipulated settlement agreement, we are reevaluating our May 3, 2006,
determination (71 FR 26007) that listing the roundtail chub population
segment in the lower Colorado River basin was not warranted because it
did not meet our definition of a DPS.
In accordance with our DPS Policy, this section details our
analysis of the first two elements we consider in a decision regarding
the status of a possible DPS as endangered or threatened under the Act.
These elements are (1) the population segment's discreteness from the
remainder of the species to which it belongs and (2) the significance
of the population segment to the species to which it belongs.
Discreteness
The DPS policy's standard for discreteness requires an entity to be
adequately defined and described in some way that distinguishes it from
other representatives of its species. A population segment of a
vertebrate species may be considered discrete if it satisfies either
one of the following two conditions: (1) It is markedly separated from
other populations of the same taxon as a consequence of physical,
physiological, ecological, or behavioral factors (quantitative measures
of genetic or morphological discontinuity may provide evidence of this
separation); or (2) it is delimited by international governmental
boundaries within which significant differences in control of
exploitation, management of habitat, conservation status, or regulatory
mechanisms exist.
The historical range of roundtail chub included both the upper and
lower Colorado River basins in the States of Wyoming, Utah, Colorado,
New Mexico, Arizona, and Nevada (Propst 1999, p. 23; Bezzerides and
Bestgen 2002, p. 25; Voeltz 2002, pp. 19-23), but the roundtail chub
was likely only a transient in Nevada. Currently roundtail chubs occur
in both the upper and lower Colorado River basins in Wyoming, Utah,
Colorado, New Mexico, and Arizona. Bezzerides and Bestgen (2002, p. 24)
concluded that historically there were two discrete population centers,
one in each of the lower and upper basins, and that these two
population centers remain today. Numerous authors have noted that
roundtail chub was very rare with few documented records in the
mainstem Colorado River between the two basins (Minckley 1973, p. 102;
Minckley 1979, p. 51; Valdez and Ryel 1994, pp. 5-10-5-11; Minckley
1996, p. 75; Bezzerides and Bestgen 2002, pp. 24-25; Voeltz 2002, pp.
19, 112), so we do not consider the mainstem to have been occupied
historically, and have not considered the Colorado River in our
estimates of historical range. Early surveyors also variably used the
term ``bonytail'' to describe roundtail chub (Valdez and Ryel 1994, pp.
5-7), further clouding information on historical distribution, as some
accounts of roundtail chub in the mainstem may have been bonytail (Gila
elegans), which is a mainstem species in the Colorado River. Records
from the mainstem Colorado River also may have been transients from
nearby populations, such as some records from Grand Canyon, which may
have been from the Little Colorado River (Voeltz 2002, p. 112). One
record from between the two basins, a record of two roundtail chubs
captured near Imperial Dam in 1973, illustrates this. Upon examining
these specimens, Minckley (1979, p. 51) concluded that they were strays
washed downstream from the Bill Williams River based on their heavily
blotched coloration. This is a logical conclusion considering that
roundtail chub from the Bill Williams River typically exhibit this
blotched coloration (Rinne 1969, pp. 20-21; Rinne 1976, p. 78).
Minckley (1979, p. 51), Minckley (1996, p. 75), and Mueller and Marsh
(2002, p. 40) also considered roundtail chub rare or essentially absent
in the Colorado River mainstem based on the paucity of records from
numerous surveys of the Colorado River mainstem.
We conclude that historically, roundtail chub occurred in the
Colorado River basin in two population centers, one each in the upper
(largely in Utah and Colorado, and to a lesser extent, in Wyoming and
New Mexico) and lower basins (Arizona and New Mexico), with apparently
little, if any, mixing of the two populations. If there was one
population, we would expect to find a large number of records in the
mainstem Colorado River between the San Juan and Bill Williams Rivers,
but very few records of roundtail chub exist from this reach of stream.
Also, there is a substantial distance between these areas of roundtail
chub occurrence in the two basins. The mouth of the Escalante River,
which contains the southernmost population of roundtail chub in the
upper basin, is approximately 275 river miles (mi) (443 kilometers
(km)) upstream from Grand Falls on the Little Colorado River, the
historical downstream limit of the most northern population of the
lower Colorado River basin. The lower Colorado River basin roundtail
chub population segment meets the element of discreteness because it
was separate historically, and continues to be markedly separate today.
In more recent times, the upper and lower basin populations of the
roundtail chub have been physically separated by Glen Canyon Dam, but
that artificial separation is not the sole basis for our finding that
the lower basin population is discrete from the upper basin. The
historical information on collections suggests that there was limited
contact even before the dam was built. Available molecular information
for the species, although sparse, seems to support this; mitochondrial
DNA markers (mtDNA; a type of genetic material) of roundtail chub in
the Gila River basin are entirely absent from upper basin populations
(Gerber et al. 2001, p. 2028; see Significance discussion below).
[[Page 32354]]
Significance
If we have determined that a vertebrate population segment is
discrete under our DPS policy, we consider its biological and
ecological significance to the taxon to which it belongs in light of
Congressional guidance (see Senate Report 151, 96th Congress, 1st
Session) that the authority to list DPSs be used ``sparingly'' while
encouraging the conservation of genetic diversity. To evaluate whether
a discrete vertebrate population may be significant to the taxon to
which it belongs, we consider available scientific evidence of the
discrete population segment's importance to the taxon to which it
belongs. Since precise circumstances are likely to vary considerably
from case to case, the DPS policy does not describe all the classes of
information that might be used in determining the biological and
ecological importance of a discrete population. However, the DPS policy
describes four possible classes of information that provide evidence of
a population segment's biological and ecological importance to the
taxon to which it belongs. This consideration may include, but is not
limited to: (1) Persistence of the discrete population segment in an
ecological setting that is unusual or unique for the taxon; (2)
evidence that loss of the discrete population segment would result in a
significant gap in the range of the taxon; (3) evidence that the
discrete population segment represents the only surviving natural
occurrence of a taxon that may be more abundant elsewhere as an
introduced population outside its historical range; or (4) evidence
that the discrete population segment differs markedly from other
populations of the species in its genetic characteristics.
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 ecoregions display
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 (in) per year
(8-165 centimeters (cm) per year)) (Jeppson 1968, p. 1) somewhat less
arid than the lower basin (5-25 in per year (13-64 cm per year)) (Green
and Sellers 1964, pp. 8-11).
The type (snow or rain) and timing of precipitation are major
factors determining the pattern of annual streamflow. A hydrograph
depicts the amount of runoff or discharge over time (Leopold 1997, pp.
49-50). 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, pp.
B3-B7; Green and Sellers 1964, pp. 8-11; Minckley and Rinne 1991,
p.12). 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, pp. B3-B7; Ray et al. 2007, p. 1617).
In the upper basin, roundtail chub habitats have strong snowmelt
hydrographs, with some summer, fall, and winter precipitation, but with
the majority of major flow events in spring and early summer (Bailey
1995, p. 341; Carlson and Muth 1989, p. 222; Woodhouse et al. 2003, p.
1551). 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; in contrast, this is typically the
wettest period in the upper basin (Carlson and Muth 1989, p. 222).
Regarding the differences between the two basins, Carlson and Muth
(1989), for example, conclude, ``The upper basin produced most of the
river's discharge, and peak flows occurred after snowmelt in spring and
early summer. Maximum runoff in the lower basin often followed winter
rainstorms.'' Sediment loads vary substantially between streams in both
basins, but are generally lesser in the upper basin than the lower, 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.
Gap in the Range. Roundtail chub in the lower Colorado River basin
can be considered significant under our DPS analysis because loss of
the lower Colorado River populations of roundtail chub would result in
a significant gap in the range of the taxon; this area constitutes over
one third of the species' historical range (2 out of 6 States),
including the species' entire current range in two States (Arizona and
New Mexico) and all of several major river systems, including the
Little Colorado, Bill Williams, and Gila River basins. Additionally
there are 74 populations of roundtail chub remaining in the upper basin
and 31 in the lower basin; thus, the lower basin populations also
constitute approximately one third (30 percent) of the remaining
populations of the species (Bezzerides and Bestgen 2002, pp. 28-29,
Appendix C; Voeltz 2002, pp. 82-83). The populations in the lower basin
also account for approximately 107,300 square mi (270,906 square km; 49
percent) of the 219,310 square mi (568,010 square km) of the Colorado
River Basin (U.S. Geological Survey 2006, pp. 94-102). In addition, the
roundtail chub historically occupied up to 2,796 mi (4,500 km) of
stream in the lower basin and currently occupies between 497 mi (800
km) and 901 mi (1450 km) of stream habitat in the lower basin. These
populations are not newly established, ephemeral, or migratory; the
species has been well established in the lower Colorado River basin,
and has represented a large portion of the species' range for a long
period of time (Bezzerides and Bestgen 2002, pp. 20-29; Voeltz 2002,
pp. 82-83).
[[Page 32355]]
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 historical 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.
Marked Differences in Genetic Characteristics. Long-standing
difficulties in morphological discrimination and taxonomic distinction
among members from the lower Colorado G. robusta complex, and the genus
Gila as a whole, due in part to the role hybridization has played in
its evolution, have plagued conservation efforts. But it is important
to consider variation throughout the entire Colorado River basin to
place variation and divergence in the lower basin Gila robusta complex
in appropriate context. Two isolated species of hybrid origin
(involving G. robusta with G. elegans and G. cypha) can be found in the
Virgin and White River drainages (G. seminuda--DeMarais et al. 1992, p.
2747; G. jordani--Gerber et al. 2001, p. 2033, respectively). Gila
robusta is relatively abundant in the mainstem Colorado River and
tributaries above the Glen Canyon Dam in the upper basin. All
individuals from the headwaters of the Little Colorado River and the
mainstem Colorado River and tributaries above Glen Canyon Dam in the
upper basin possess G. cypha or G. elegans mtDNA (Dowling and DeMarais
1993, pp. 444-446; Gerber et al. 2001, p. 2028). However, populations
of the G. robusta complex of the lower basin in the Bill Williams and
Gila River basins (including G. robusta, G. intermedia, and G. nigra)
possess a unique, divergent mtDNA lineage that has never been found
outside the lower basin (Dowling and DeMarais 1993, pp. 444-446; Gerber
et al. 2001, p. 2028). But as Gerber et al. (2001, p. 2037) noted,
genetic information in Gila poorly accounts for species morphology,
stating ``the decoupling of morphological and mtDNA variation in
Colorado River Gila illustrates how hybridization and local adaptation
can play important roles in evolution.'' Although individuals in the
Little Colorado River illustrate some minor genetic uniqueness, the
evidence, though limited (samples size in Gerber et al. 2001 was
limited to 7 individuals) indicates these populations align more
closely with the upper Colorado River basin populations. But
discriminating between populations of Gila based on these data is
difficult, and more data and analysis may help to place these
populations in better perspective.
DPS Conclusion
We have reevaluated the lower Colorado River populations of the
roundtail chub to determine whether they meet the definition of a DPS,
addressing discreteness and significance as required by our policy. We
have considered the extent of the range of the roundtail chub in the
lower Colorado River basin relative to the rest of the species' range,
the ecological setting of roundtail chub in the lower Colorado River
basin, and available information on the genetics of the species. We
conclude that the lower Colorado River populations are discrete from
the upper Colorado River basin populations on the basis of their
present and historical geographic separation of 275 river mi (444 km)
and because few historical records have been detected in the mainstem
Colorado River between the two population centers that would confirm
significant connectivity historically. We also conclude that the lower
Colorado River basin roundtail chub is significant because of its
unique ecological setting compared to the upper basin, and because the
loss of the species from the lower basin would result in a significant
gap in the range of the species. Genetic information for this species
has long been difficult to interpret, and additional data and analysis
may help to clarify this.
In our 2006 finding, we made the determination that the roundtail
chub in the lower Colorado River basin did not meet our definition of a
DPS. We have reevaluated that determination and now find the best
available information has demonstrated that these populations are
discrete, persist in an ecological setting that is unique for the
taxon, and, if lost, would result in a significant gap in the range of
the taxon. Because this population segment meets both the discreteness
and significance elements of our DPS policy, the lower Colorado River
population segment of the roundtail chub qualifies as a DPS in
accordance with our DPS policy, and as such, is a listable entity under
the Act. Below we provide a summary of the biology, status, and
distribution of the DPS, and an analysis of threats to the DPS, based
on the five listing factors established by the Act.
Biology
The roundtail chub is a cyprinid fish (member of Cyprinidae, the
minnow family) with a streamlined body shape. Color in roundtail chub
is usually olive-gray to silvery, with the belly lighter, and sometimes
with dark blotches on the sides. Roundtail chubs are generally 9 to 14
in. (25 to 35 cm) in length, but can reach 20 in. (50 cm) (Minckley
1973, pp. 101-103; Sublette et al. 1990, pp. 126-129; Propst 1999, pp.
23-25; Minckley and Demaris 2000, pp. 251-256; Voeltz 2002, pp. 8-11).
Baird and Girard first described roundtail chub from specimens
collected from the Zuni River in northeastern Arizona and northwestern
New Mexico (Baird and Girard 1853, pp. 368-369). Roundtail chub has
been recognized as a distinct species since the 1800s (Miller 1945, p.
104; Holden 1968, pp. 27-28; Rinne 1969, pp. 27-42; Holden and
Stalnaker 1970, p. 409; Rinne 1976, pp. 87-91; Smith et al. 1979, p.
623; DeMarais 1986, p. iii; Douglas et al. 1989, p. 653; Rosenfeld and
Wilkinson 1989, p. 232; DeMarais 1992, pp. 63-64; Dowling and DeMarais
1993, p. 444; Douglas et al. 1998, p. 169; Minckley and DeMarais 2000,
p. 255; Gerber et al. 2001, p. 2028), and is currently recognized as a
species by the American Fisheries Society (Nelson et al. 2004, p. 71).
The chubs of the genus Gila in the lower Colorado River basin are all
closely related and are often regarded as a species complex (Minckley
1973, p. 101; DeMarais 1992, p. 150; Dowling and DeMarais 1993, p. 444;
Minckley and DeMarais 2000, p. 251; Gerber et al. 2001, p. 2028).
Roundtail chubs in the lower Colorado River basin are found in cool
to warm waters of rivers and streams, and often occupy the deepest
pools and eddies of large streams (Minckley 1973, p. 101; Brouder et
al. 2000, pp. 6-8; Minckley and DeMarais 2000, p. 255; Bezzerides and
Bestgen 2002, pp. 17-19). Although roundtail chubs are often associated
with various cover features, such as boulders, vegetation, and undercut
banks, they are less apt to use cover than other related species such
as the headwater chub and Gila chub (Gila intermedia) (Minckley and
DeMarais 2000, p. 2145). Water temperatures of habitats occupied by
roundtail chub vary between 0 degrees and greater than 32 degrees
Celsius ([deg]C) (32 to 90 degrees Fahrenheit ([deg]F)) (Bestgen 1985,
p. 14). Carveth et al. (2006, p. 1435) reported the upper thermal
tolerance of roundtail chub to be 36.6 [deg]C (97.9 [deg]F); spawning
has been documented from 14 to 24 [deg]C (57 to 75 [deg]F) (Bestgen
1985, p. 14; Kaeding et al. 1990, p. 139; Brouder et
[[Page 32356]]
al. 2000, p. 13). Spawning occurs from February through June in pool,
run, and riffle habitats, with slow to moderate water velocities (Neve
1976, p. 32; Bestgen 1985, pp. 56-67; Propst 1999, p. 24; Brouder et
al. 2000, p. 12; Voeltz 2002, p. 16). Roundtail chubs live for 5 to 7
years and spawn from age 2 on (Bestgen 1985, p. 62; Brouder et al.
2000, p. 12). Roundtail chubs are omnivores, consuming foods
proportional to their availability, including aquatic and terrestrial
invertebrates, aquatic plants, detritus, and fish and other
vertebrates; algae and aquatic insects can be major portions of the
diet (Bestgen 1985, pp. 46-53; Schreiber and Minckley 1981, pp. 409,
415; Propst 1999, p. 24).
Status and Distribution of the Lower Colorado River DPS
The historical distribution of roundtail chub in the lower Colorado
River basin is poorly documented because there were few early
collections, and perhaps more importantly, because many populations of
native fish, including roundtail chub, were likely lost prior to early
comprehensive fish surveys because habitat-altering actions (e.g.,
dewatering, livestock grazing, mining) were widespread, and had already
severely altered aquatic habitats (Girmendonk and Young 1997, p. 50;
Minckley 1999, p. 179; Voeltz, 2002, p. 19). Roundtail chub was
historically considered common throughout its range (Minckley 1973, p.
101; Holden and Stalnaker 1975, p. 222; Propst 1999, p. 23). Voeltz
(2002), estimating historical distribution based on museum collection
records, agency database searches, literature searches, and discussion
with biologists, found that roundtail chub in the lower Colorado River
basin was historically found in the Gila and Zuni Rivers in New Mexico;
the Black, Colorado (though likely only as a transient), Little
Colorado, Bill Williams, Gila, San Francisco, San Carlos, San Pedro,
Salt, Verde, White, and Zuni Rivers in Arizona: and numerous
tributaries within those basins. Voeltz (2002, p. 83) estimated the
lower Colorado River basin roundtail chub historically occupied
approximately 2,796 mi (4,500 km) of rivers and streams in Arizona and
New Mexico. Although roundtail chubs were never collected from the
Colorado River or San Pedro River basin in Mexico, they may have
occurred in these areas based on records near the international border
in the lower Colorado River and upper San Pedro River and the
occurrence of suitable habitat in these streams in Mexico (Voeltz 2002,
p. 20).
Miller (1961) first comprehensively documented the decline of
fishes of the southwestern United States in 1961, but interestingly,
F.M. Chamberlain made similar observations in Arizona in 1904;
roundtail chub was included in these assessments and in subsequent
evaluations of imperiled fish species of the region (Miller 1961, pp.
373-379; Miller 1972, p. 242; Deacon et al. 1979, p. 34; Minckley 1999,
pp. 215-218). The decline of the species has been documented both in
the scientific peer-reviewed literature (Bestgen and Propst 1989, p.
402) and in State agency reports (Girmendonk and Young 1997, p. 49;
Propst 1999, p. 23; Brouder et al. 2000, p. 1; Bezzerides and Bestgen
2002, pp. iii-iv; Voeltz 2002, p. 83). Roundtail chub is considered
vulnerable by the American Fisheries Society (Jenks et al. 2008, p.
390).
Roundtail chub in the lower Colorado River basin in Arizona
currently occurs in two tributaries of the Little Colorado River
(Chevelon and East Clear Creeks); several tributaries of the Bill
Williams River basin (Boulder, Burro, Conger, Francis, Kirkland,
Sycamore, Trout, and Wilder Creeks); the Salt River and four of its
tributaries (Ash Creek, Black River, Cherry Creek and Salome Creek);
the Verde River and five of its tributaries (Fossil, Oak, Roundtree
Canyon, West Clear, and Wet Beaver Creeks); Aravaipa Creek (a tributary
of the San Pedro River); Eagle Creek (a tributary of the Gila River);
and in New Mexico, in the upper Gila River (Voeltz 2002, pp. 82-83; the
upper Gila River is used in this document to denote that portion of the
Gila River basin in New Mexico). The Salt River and Verde River are
occupied in several reaches that are fragmented and separated by two
large dams and reservoirs on the Verde River, and four large dams and
reservoirs on the Salt River. Roundtail chubs also occur in canals in
Phoenix that are fed by the lower Salt and Verde Rivers. Roundtail
chubs inhabit several streams in the Salt River drainage, although
survey information on the San Carlos Apache Reservation and White
Mountain Apache Reservation is proprietary and confidential, and their
status is not currently known; these streams include Canyon, Carrizo,
Cedar, Cibecue, and Corduroy Creeks, and the White River (Voeltz 2002,
pp. 82-83).
The Arizona Game and Fish Department (AGFD) conducted a
comprehensive status review of roundtail and headwater chub (Voeltz
2002) in the lower Colorado River basin that included a review of all
available current and historical survey records and estimated
historical and current range of roundtail chub using information from
museum collections, agency databases, records found in literature, and
consultation with experts. The report found that roundtail chub
populations and distribution had declined significantly from historical
levels. Based on Voeltz (2002), roundtail chub is known to occupy only
18 percent of its former range in the lower Colorado River basin;
status in an additional 14 percent of its range is unknown. Based on
the best available scientific information in Voeltz (2002), the
roundtail chub in the lower Colorado River basin appears to occupy
about 18 to 32 percent of its former range (approximately 497 mi (800
km) out of the 2,796 mi (4,500 km)) considered to be formerly occupied)
in Arizona and New Mexico. We now consider the Colorado River in the
lower Colorado River basin to be outside the historical range of the
species (Voeltz considered it to have been occupied); given this,
roundtail chub has been extirpated from 672 mi (965 km) of 2,197 mi
(3,535 km; approximately 60 percent) of its formerly occupied range. Of
the populations for which status and threat information is available,
all but one of the remaining natural populations are considered
threatened by both the presence of nonnative species and habitat-
altering land uses.
In the report, Voeltz (2002) used a classification system to report
status and threat information. Populations were defined as an
occurrence at a stream-specific locality. A population was considered
``stable-secure,'' ``stable-threatened,'' or ``unstable-threatened,''
based on abundance, population trend, and threat information for the
locality (see Table 1, Voeltz 2002, p. 5). Voeltz (2002, p. 5)
considered a population ``extirpated'' if the species was no longer
believed to occupy the site, and ``unknown'' if there are too few data
to determine status. Note that the term ``threatened'' as used by
Voeltz (2002, p. 5) is not the definition of ``threatened'' used in the
Act in which a species is likely to become endangered in the
foreseeable future, but rather is an estimate of the likelihood that a
population is likely to become extirpated. Of 40 populations of
roundtail chub in the lower Colorado River basin identified in the
report, Voeltz (2002, pp. 82-87) found that none were ``stable-
secure,'' 6 were ``stable-threatened,'' 13 were ``unstable-
threatened,'' 10 were ``extirpated,'' and 11 were of ``unknown''
status. Populations with an ``unknown'' status in Voeltz (2002)
included nine populations wholly or partly on Tribal lands. Tribes are
sovereign nations and
[[Page 32357]]
survey data is proprietary and confidential, but existing survey
information for these streams was provided and indicated occupancy. The
remaining two populations with ``unknown'' status lacked sufficient
information to assign a category.
Table 1--Definitions of Status Description Categories Used to Describe
Roundtail Chub Populations
[From Voeltz 2002]
------------------------------------------------------------------------
Status Definition
------------------------------------------------------------------------
Stable-Secure (SS)........................... Chubs are abundant or
common, data over the
past 5-10 years shows a
stable, reproducing
population with
successful recruitment
(survival of young to
Age 2, reproductive
age); no impacts from
nonnative aquatic
species exist; and no
current or future
habitat altering land or
water uses were
identified.
Stable-Threatened (ST)....................... 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 (UT)..................... 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 (E)............................... Chubs are no longer
believed to occur in the
system.
Unknown (UN)................................. Lack of data precludes
determination of status.
------------------------------------------------------------------------
We have updated this assessment with new data from various sources,
particularly Cantrell (2009) as provided in Table 2 below. It is
important to recognize that these status categories are qualitative,
and based on very limited data in most instances. We have very little
information on the population size, length of the stream reach,
survivorship, recruitment (survival of young to Age 2, reproductive
age), or age structure of these populations. These categories are also
often based on only a few surveys conducted over decadal time scales.
We now consider 1 population ``stable-secure,'' 8 populations ``stable-
threatened,'' 13 populations ``unstable-threatened,'' and 9 populations
``unknown.'' Ten populations remain extirpated although we now consider
what was called a population in the Colorado River to have been
occupied only by transient individuals. In the nine populations with
``unknown'' status, two (Ash Creek and Roundtree Creek) are newly
established via translocation and have not been extant long enough to
determine successful establishment. Information on the Black River and
Conger Creek provided since the 2002 report resulted in
recategorization of both of those sites from ``unknown'' to ``stable-
threatened'' and for recategorization of Eagle Creek from ``unknown''
to ``unstable-threatened.'' Improved status at Fossil Creek that allows
that population to reach ``stable-secure'' is due to removal of the
power plant and associated structures, construction of a new fish
barrier, and chemical renovation to remove nonnative fish species.
Recent surveys have confirmed some of the information in Voeltz's 2002
status review; in the upper Black River, Chevelon Creek, and East Clear
Creek, the species persists in the presence of abundant nonnative
predators, and apparently reproduces successfully, but distribution
appears limited, abundance is unknown, and other signs, such as
abundance of other native fish species, indicate these native fisheries
are deteriorating (AGFD 2005a, p. 4; 2005b, pp. 4-5; Clarkson and Marsh
2005a, pp. 6-8; 2005b, pp. 6-7). Other roundtail chub populations in
waters with abundant nonnative predators are less able to reproduce
successfully and the particular circumstances at these three sites are
worth further investigation. Roundtail chub in the lower Colorado River
basin in New Mexico may now be extirpated. The species has long been
considered extirpated in many Gila River tributaries in New Mexico, and
has become very rare in the mainstem Gila River (Carman 2006, pp. 9,
18).
Table 2--Summary of Roundtail Chub Status and Threats by Stream Reach
[Voeltz 2002, Cantrell 2009, service files]
------------------------------------------------------------------------
Regional historical or
Location Current status current threats
------------------------------------------------------------------------
Management Area A--Gila River Basin
------------------------------------------------------------------------
Aravaipa Creek................. ST Factor A: Water
diversions,
groundwater pumping,
recreation, mining,
livestock grazing,
road use.
.............. Factor C: Nonnative
species.
Blue River..................... E Factor A: Water
diversions,
groundwater pumping,
logging and fuel wood
cutting, recreation,
livestock grazing,
road use.
.............. Factor C: Nonnative
species.
Eagle Creek.................... UT Factor A: Dams, water
diversions,
groundwater pumping,
recreation, mining,
livestock grazing.
.............. Factor C: Nonnative
species.
San Francisco River............ E Factor A: Dams, water
diversions,
groundwater pumping,
dewatering, logging
and fuel wood cutting,
recreation, mining,
urban and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
Upper Gila River............... UT Factor A: Dams, water
diversions,
groundwater pumping,
dewatering, logging
and fuel wood cutting,
recreation, mining,
urban and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
Lower Gila River............... E Factor A: Dams, water
diversions,
groundwater pumping,
dewatering, logging
and fuel wood cutting,
recreation, mining,
urban and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
San Pedro River................ E Factor A: Dams, water
diversions,
groundwater pumping,
dewatering, logging
and fuel wood cutting,
recreation, mining,
urban and agricultural
development, livestock
grazing.
[[Page 32358]]
.............. Factor C: Nonnative
species.
------------------------------------------------------------------------
Management Area A--Salt River Basin
------------------------------------------------------------------------
Ash Creek...................... UN Factor A: Recreation,
logging and fuel wood
cutting, livestock
grazing.
Black River.................... ST Factor A: Water
diversions,
groundwater pumping,
recreation, livestock
grazing, mining,
logging and fuel wood
cutting, urban and
agricultural
development.
.............. Factor C: Nonnative
species.
Canyon Creek................... UN Factor A: Livestock
grazing, recreation,
limited fuelwood
harvest, limited
agriculture, fisheries
and wildlife
management, and
localized municipal,
urban and rural
development and
associated water use.
.............. Factor C: Nonnative
species.
Carrizo Creek.................. UN Factor A: Livestock
grazing, recreation,
limited fuelwood
harvest, limited
agriculture, fisheries
and wildlife
management, and
localized municipal,
urban and rural
development and
associated water use.
.............. Factor C: Nonnative
species.
Cedar Creek.................... UN Factor A: Livestock
grazing, recreation,
limited fuelwood
harvest, limited
agriculture, fisheries
and wildlife
management, and
localized municipal,
urban and rural
development and
associated water use.
.............. Factor C: Nonnative
species.
Cherry Creek................... ST Factor A: Water
diversions,
groundwater pumping,
mining, recreation,
livestock grazing,
logging and fuel wood
cutting, urban and
agricultural
development.
.............. Factor C: Nonnative
species.
Cibecue Creek.................. UN Factor A: Livestock
grazing, recreation,
limited fuelwood
harvest, limited
agriculture, fisheries
and wildlife
management, and
localized municipal,
urban and rural
development and
associated water use.
.............. Factor C: Nonnative
species.
Corduroy Creek................. UN Factor A: Livestock
grazing, recreation,
limited fuelwood
harvest, limited
agriculture, fisheries
and wildlife
management, and
localized municipal,
urban and rural
development and
associated water use.
.............. Factor C: Nonnative
species.
Salome Creek................... UT Factor A: Recreation,
logging and fuel wood
cutting, livestock
grazing.
.............. Factor C: Nonnative
species.
Salt River..................... UT Factor A: Dams, water
diversions,
groundwater pumping,
dewatering, logging
and fuel wood cutting,
recreation, mining,
urban and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
White River.................... UN Factor A: Water
diversions,
groundwater pumping,
recreation, livestock
grazing, mining,
logging and fuel wood
cutting, urban and
agricultural
development.
.............. Factor C: Nonnative
species.
------------------------------------------------------------------------
Management Area A--Verde River Basin
------------------------------------------------------------------------
Dry Beaver Creek............... E Factor A: Water
diversions,
dewatering, livestock
grazing, logging and
fuel wood cutting,
recreation.
.............. Factor C: Nonnative
species.
Fossil Creek................... SS Factor A: Water
diversions,
groundwater pumping,
dewatering, mining,
contaminants, urban
and agricultural
development, livestock
grazing.
Oak Creek...................... UT Factor A: Water
diversions,
groundwater pumping,
dewatering, mining,
contaminants, urban
and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
Roundtree Canyon............... UN Factor A: Recreation,
logging and fuel wood
cutting, livestock
grazing.
Verde River.................... ST Factor A: Water
diversions,
groundwater pumping,
dewatering, mining,
contaminants, urban
and agricultural
development, livestock
grazing.
.............. Factor C: Nonnative
species.
West Clear Creek............... ST Factor A: Water
diversions,
dewatering, livestock
grazing, logging and
fuel wood cutting,
recreation.
.............. Factor C: Nonnative
species.
Wet Beaver Creek............... UT Factor A: Water
diversions,
dewatering, livestock
grazing, logging and
fuel wood cutting,
recreation.
.............. Factor C: Nonnative
species.
------------------------------------------------------------------------
Management Area B--Bill Williams River Basin
------------------------------------------------------------------------
Big Sandy River................ E Factor A: Water
diversions,
groundwater pumping,
recreation, mining,
livestock grazing,
residential
development.
.............. Factor C: Nonnative
species.
Bill Williams River............ E Factor A: Water
diversions,
groundwater pumping,
recreation, mining,
livestock grazing.
.............. Factor C: Nonnative
species.
Boulder Creek.................. ST Factor A: Groundwater
pumping, recreation,
livestock grazing.
.............. Factor C: Nonnative
species.
Burro Creek.................... UT Factor A: Water
diversions,
groundwater pumping,
recreation, mining,
livestock grazing,
residential
development,
contaminants.
.............. Factor C: Nonnative
species.
Conger Creek................... ST Factor A: Groundwater
pumping, mining,
livestock grazing,
recreation.
.............. Factor C: Nonnative
species.
Francis Creek.................. UT Factor A: Groundwater
pumping, mining,