# 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

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URL: https://www.frixlaw.com/law-library/documents/fr%3AE9-15828

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** July 7, 2009
- **Citation:** 74 FR 32352

## Text

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.

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
http://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

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).

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).

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 (°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

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

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]

Location

Current
status

Regional historical or 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.

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, livestock grazing, recreation.

Factor C: Nonnative species.

Kirkland Creek
UT
Factor A: Groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.

Factor C: Nonnative species.

Santa Maria River
UT
Factor A: Groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.

Factor C: Nonnative species.

Sycamore Creek
UT
Factor A: Water diversions, groundwater pumping, recreation, mining, livestock grazing, residential development, contaminants.

Factor C: Nonnative species.

Trout Creek
ST
Factor A: Water diversions, groundwater pumping, recreation, residential development.

Factor C: Nonnative species.

Wilder Creek
UN
Factor A: Groundwater pumping, mining, livestock grazing, recreation.

Factor C: Nonnative species.

Management Area C—Little Colorado River Basin

Chevelon Creek
UT
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.

East Clear Creek
UT
Factor A: Logging and fuel wood cutting, recreation, mining, livestock grazing, contaminants.

Factor C: Nonnative species.

Little Colorado 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.

Zuni River
E
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.

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 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).

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 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 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

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 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 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

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 late-1880s 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 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 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

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 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 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 rest-rotation 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,

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), 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 nutrient-enriched 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 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

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 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 comparisons of macroinvertebrate communities above and below highway crossings indicate that there are reductions in diversity and pollution-sensitive 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

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 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).

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

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 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; Mérigoux 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 low-intensity 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 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,

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 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).

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;

(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 h

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3AE9-15828. Public record. Not legal advice.