Endangered and Threatened Wildlife and Plants; Endangered Status and Designation of Critical Habitat for Spikedace and Loach Minnow

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2010-0072; MO 92210-0-0009-B4]

RIN 1018-AX17

Endangered and Threatened Wildlife and Plants; Endangered Status and Designation of Critical Habitat for Spikedace and Loach Minnow

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to change the status of spikedace (

Meda fulgida

) and loach minnow (

Tiaroga cobitis

) from threatened to endangered under the Endangered Species Act of 1973, as amended, and to designate critical habitat for both species. In total, we are proposing approximately 1,168 kilometers (726 mi) of streams as critical habitat for spikedace, and 1,141 kilometers (709 miles) of streams as critical habitat for loach minnow. The proposed critical habitat is located in Apache, Cochise, Gila, Graham, Greenlee, Navajo, Pima, Pinal, and Yavapai Counties, Arizona, and Catron, Grant, and Hidalgo Counties in New Mexico.

DATES:

We will consider comments received or postmarked on or before December 27, 2010. We must receive requests for public hearings, in writing, at the address shown in the

FOR FURTHER INFORMATION CONTACT

section by December 13, 2010.

ADDRESSES:

You may submit comments by one of the following methods:

•

Federal eRulemaking Portal: http://www.regulations.gov.

Follow the instructions for submitting comments to Docket No. FWS-R2-ES-2010-0072.

•

U.S. mail or hand-delivery:

Public Comments Processing, Attn: [Docket Number FWS-R2-ES-2010-0072]; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, VA 22203.

We will not accept e-mail or faxes. We will post all comments on

http://www.regulations.gov.

This generally means that we will post any personal information you provide us (see the Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT:

Steve Spangle, Field Supervisor, U.S. Fish and Wildlife Service, Arizona Ecological Services Office, 2321 W. Royal Palm Road, Suite 103, Phoenix, AZ 85021; telephone (602) 242-0210; facsimile (602) 242-2513. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Public Comments

This document consists of: (1) A proposed rule to reclassify spikedace (

Meda fulgida

) and loach minnow (

Tiaroga cobitis

) from threatened to endangered status; and (2) a proposed rule to designate critical habitat for the two species.

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning this proposed rule. We particularly seek comments concerning:

(1) The factors that are the basis for making a listing determination for a species under section 4(a) of the Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531

et seq.

), which are:

(a) The present or threatened destruction, modification, or curtailment of its habitat or range;

(b) Overutilization for commercial, recreational, scientific, or educational

purposes;

(c) Disease or predation;

(d) The inadequacy of existing regulatory mechanisms; or

(e) Other natural or manmade factors affecting its continued existence.

(2) Additional information concerning the range, distribution, and population size of this species, including the locations of any additional populations of this species.

(3) Any information on the biological or ecological requirements of the species.

(4) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531

et seq.

) including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation such that the designation of critical habitat may not be prudent.

(5) Specific information on:

• The amount and distribution of spikedace and loach minnow habitat;

• What areas occupied at the time of listing and containing features essential to the conservation of the species should be included in the designation and why;

• Special management considerations or protections that features essential to the conservation of spikedace and loach minnow, as identified in this proposal, may require, including managing for the potential effects of climate change; and

• What areas not occupied at the time of listing are essential for the conservation of the species and why.

(6) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(7) Any probable economic, national security, or other impacts of designating any area that may be included in the final designation. We are particularly interested in any impacts on small entities or families, and the benefits of including or excluding areas that exhibit these impacts.

(8) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

(9) Information on whether the benefit of an exclusion of any particular area outweighs the benefit of inclusion under section 4(b)(2) of the Act. We specifically solicit the delivery of spikedace- and loach minnow-specific management plans for areas included in this proposed designation. Management plans considered in previous critical habitat exclusions for spikedace and loach minnow are available through the contact information listed in the

FOR FURTHER INFORMATION CONTACT

section.

(10) Information on the projected and reasonably likely impacts of climate change on spikedace and loach minnow and on the critical habitat areas we are proposing.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the

ADDRESSES

section. We will not accept comments sent by e-mail or fax or to an address not listed in the

ADDRESSES

section.

We will post your entire comment—including your personal identifying information—on

http://www.regulations.gov.

If you provide personal identifying information, such as your street address, phone number, or e-mail address, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on

http://www.regulations.gov,

or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Arizona Ecological Services Office (see

FOR FURTHER INFORMATION CONTACT)

.

Background

It is our intent to discuss only those topics directly relevant to the proposed reclassification and proposed designation of critical habitat for spikedace and loach minnow in this proposed rule. For more information on the species themselves, refer to the final listing rule (51 FR 23769, July 1, 1986 (spikedace), and 51 FR 39468, October 28, 1986 (loach minnow)) and the previous critical habitat designation (72 FR 13356, March 21, 2007).

Spikedace

The spikedace is a member of the minnow family Cyprinidae, and is the only species in the genus

Meda.

The spikedace was first collected from the San Pedro River in 1851. The spikedace is a small, slim fish less than 75 millimeters (mm) (3 inches (in)) in length (Sublette

et al.

1990, p. 136). Spikedace have olive-gray to brownish skin, with silvery sides and vertically elongated black specks. Spikedace have spines in the dorsal fin (Minckley 1973, pp. 82, 112, 115).

Spikedace are found in moderate to large perennial streams, where they inhabit shallow riffles (those shallow portions of the stream with rougher, choppy water) with sand, gravel, and rubble substrates (Barber and Minckley 1966, p. 31; Propst

et al.

1986, p. 12; Rinne and Kroeger 1988, p. 1; Rinne 1991, pp. 8-10). Specific habitat for this species consists of shear zones where rapid flow borders slower flow; areas of sheet flow at the upper ends of mid-channel sand or gravel bars; and eddies at downstream riffle edges (Rinne 1991, p. 11; Rinne and Kroeger 1988, pp. 1, 4). Recurrent flooding and a natural flow regime are very important in maintaining the habitat of spikedace and in helping maintain a competitive edge over invading nonnative aquatic species (Propst

et al.

1986, pp. 76-81; Minckley and Meffe 1987, pp. 97, 103-104).

The spikedace was once common throughout much of the Gila River basin, including the mainstem Gila River upstream of Phoenix, and the Verde, Agua Fria, Salt, San Pedro, and San Francisco subbasins. Habitat destruction and competition and predation by nonnative aquatic species reduced its range and abundance (Miller 1961, pp. 365, 377, 397-398; Lachner

et al.

1970, p. 22; Ono

et al.

1983, p. 90; Moyle 1986, pp. 28-34; Moyle

et al.

1986, pp. 416-423; Propst

et al.

1986, pp. 82-84).

Spikedace are now restricted to portions of the upper Gila River (Grant, Catron, and Hidalgo Counties, New Mexico); Aravaipa Creek (Graham and Pinal Counties, Arizona); Eagle Creek (Graham and Greenlee Counties, Arizona); and the Verde River (Yavapai County, Arizona) (Marsh

et al.

1990, pp. 107-108, 111; M. Brouder, U.S. Fish and Wildlife Service (Service), pers. comm. 2002; Stefferud and Reinthal 2005, pp. 16-21; Paroz

et al.

2006, pp. 62-67; Propst 2007, pp. 7-9, 11-14).

In 2007, spikedace were translocated into Hot Springs Canyon, in Cochise County, Arizona, and Redfield Canyon, in Cochise and Pima Counties, Arizona, and these streams were subsequently augmented (Robinson 2008a, pp. 2, 6; T. Robinson, Arizona Game and Fish Department (AGFD), pers. comm. 2008b; D. Orabutt, AGFD, pers. comm. 2009; Robinson 2009a, pp. 2, 5-8). (We use the term “translocate” to describe stocking fish into an area where suitable habitat exists, but for which there are no documented collections.) Both Hot Springs and Redfield canyons are tributaries to the San Pedro River. Spikedace were also translocated into Fossil Creek, a tributary to the Verde River in Gila County, Arizona, in 2007, and were subsequently augmented in 2008 (Carter 2007b, p. 1; Carter 2008a, p. 1; Robinson 2009b, p. 9; Boyarski

et al.

2010, in draft, p. 7). In 2008, spikedace were translocated into Bonita Creek, a tributary to the Gila River in Graham County, Arizona (H. Blasius, U.S. Bureau of Land Management (BLM), pers. comm. 2008; D. Orabutt, AGFD, pers. comm. 2009; Robinson

et al.

2009a, p. 209), and were repatriated to the upper San Francisco River in Catron County, New Mexico (D. Propst, New Mexico Department of Game and Fish (NMDGF), pers. comm. 2010). (We use the term “repatriate” to describe stocking fish into an area where we have historical records of prior presence.) Augmentations with additional fish will occur for the next several years at all sites, if adequate numbers of fish are available. Monitoring at each of these sites is ongoing to determine if populations ultimately become self-sustaining.

The species is now common only in Aravaipa Creek in Arizona (AGFD 1994; Arizona State University (ASU) 2002; P. Reinthal, University of Arizona, pers. comm. 2008, Reinthal 2009, pp. 1-2) and one section of the Gila River south of Cliff, New Mexico (NMDGF 2008; Propst

et al.

2009, pp. 14-17). The Verde River is presumed occupied; however, the last captured fish from this river was from a 1999 survey (M. Brouder, Service, pers. comm. 2002; AGFD 2004). Spikedace from the Eagle Creek population have not been seen for over a decade (Marsh 1996, p. 2), although they are still thought to exist in numbers too low for the sampling efforts to detect (Carter

et al.

2007, p. 3; see Minckley and Marsh 2009). The Middle Fork Gila River population is thought to be very small and has not been seen since 1991 (Jakle 1992, p. 6), but sampling is localized and inadequate to detect a sparse population.

Population estimates have not been developed as a result of the difficulty in detecting the species, the sporadic nature of most surveys, and the difference in surveying techniques that have been applied over time. Based on the available maps and survey information, we estimate the spikedace's present range to be approximately 10 percent or less of its historical range, and the status of the species within occupied areas ranges from common to very rare. Data indicate that the population in New Mexico has declined in recent years (Paroz

et al.

2006, p. 56). Historical and current records for spikedace are summarized in three databases (ASU 2002, AGFD 2004, NMDGF 2008), which are referenced throughout this document.

A species' geographic range is the total area that encompasses all known locations of that species. As noted above, spikedace occur in several streams in portions of Arizona and New Mexico. For purposes of this document, we have used watershed boundaries associated with the Verde, Salt, San Pedro, Gila, and San Francisco rivers to define the geographic range of spikedace. All known records of spikedace occur within these watershed boundaries.

We evaluated species detections and habitat descriptions in various databases, formal and informal survey records, agency and researcher field notes, and published literature to determine which geographic areas were reasonably occupied by the species at the time of listing. Surveys have been infrequent or inconsistent for this species. Further, even where surveys occur, the species can be difficult to detect due to its small body size. As a result, the lack of a positive detection in any specific area may not mean that the area is not occupied. Therefore, relying strictly on point-specific survey results

for historical occupancy information would likely create an incomplete picture of occupied area. The extent of a stream reach that is occupied up- or downstream of a known occupied site is generally limited only by availability of suitable habitat. Therefore, we assume that for areas where the species has been documented, it was likely also present in the adjacent stream segments if adjacent segments were connected and contain suitable habitat.

In addition, this document discusses areas occupied at the time of listing. We are defining areas occupied at the time of listing to include streams for which we have spikedace records up to 1986, when they were first listed. These records include the Agua Fria River; the Verde River and its tributaries Beaver Creek and West Clear Creek; the Salt River and its tributary Tonto Creek; the San Pedro River and its tributary Aravaipa Creek; Eagle Creek; the San Francisco River; and the Gila River and its tributaries East, Middle, and West Fork Gila, and Blue Creek.

Loach Minnow

The loach minnow is a member of the minnow family Cyprinidae. The loach minnow was first collected in 1851 from the San Pedro River in Arizona and was described by those specimens in 1865 by Girard (pp. 191-192). The loach minnow is a small, slender fish less than 80 mm (3 in) in length. It is olive-colored overall, with black mottling or splotches. Breeding males have vivid red to red-orange markings on the bases of fins and adjacent body, on the mouth and lower head, and often on the abdomen (Minckley 1973, p. 134; Sublette

et al.

1990, p. 186).

Loach minnow are found in small to large perennial streams and use shallow, turbulent riffles with primarily cobble substrate and swift currents (Minckley 1973, p. 134; Propst

et al.

1988, pp. 36-43; Rinne 1989, pp. 113-115; Propst and Bestgen 1991, pp. 29, 32-33). The loach minnow uses the spaces between, and in the lee (sheltered) side of, rocks for resting and spawning. It is rare or absent from habitats where fine sediments fill these interstitial spaces (Propst and Bestgen 1991, p. 34).

Loach minnow are now restricted to portions of the Gila River and its tributaries, the West, Middle, and East Fork Gila River (Grant, Catron, and Hidalgo Counties, New Mexico) (Paroz and Propst 2007, p. 16; Propst 2007, pp. 7-8, 10-11, 13-14); the San Francisco and Tularosa rivers and their tributaries Negrito and Whitewater creeks (Catron County, New Mexico) (Propst

et al.

1988, p. 15; ASU 2002; Paroz and Propst 2007, p. 16; Propst 2007, pp. 4-5); the Blue River and its tributaries Dry Blue, Campbell Blue, Pace, and Frieborn creeks (Greenlee County, Arizona and Catron County, New Mexico) (Miller 1998, pp. 4-5; ASU 2002; C. Carter 2005, pp. 1-5; C. Carter, AGFD, pers. comm. 2008b; Clarkson

et al.

2008, pp. 3-4; Robinson 2009c, p. 3); Aravaipa Creek and its tributaries Turkey and Deer creeks (Graham and Pinal Counties, Arizona) (Stefferud and Reinthal 2005, pp. 16-21); Eagle Creek (Graham and Greenlee Counties, Arizona), (Knowles 1994, pp. 1-2, 5; Bagley and Marsh 1997, pp. 1-2; Marsh

et al.

2003, pp. 666-668; Carter

et al.

2007, p. 3; Bahm and Robinson 2009a, p. 1); and the North Fork East Fork Black River (Apache and Greenlee Counties, Arizona) (Leon 1989, pp. 1-2; M. Lopez, AGFD pers. comm. 2000; S. Gurtin, AGFD, pers. comm. 2004; Carter 2007b, p. 2; Robinson

et al.

2009b, p. 4); and possibly the White River and its tributaries, the East and North Fork White River (Apache, Gila, and Navajo Counties, Arizona). The present range is 15 to 20 percent of its historical range, and the status of the species within occupied areas ranges from common to very rare.

As noted above, a species' range includes the total area that encompasses all known locations of that species. As with spikedace, loach minnow are known to occur in several streams in portions of Arizona and New Mexico. For purposes of this document, we have used watershed boundaries associated with the Verde, Salt, San Pedro, Gila, and San Francisco rivers to determine the range of loach minnow. All known loach minnow records occur within these watershed boundaries.

We evaluated species detections and habitat descriptions in various databases, formal and informal survey records, agency and researcher field notes, and published literature to determine which geographic areas were reasonably occupied by the species at the time of listing. Surveys have been infrequent or inconsistent for this species. Further, even where surveys occur, the species can be difficult to detect due to its small body size. As a result, the lack of a positive detection in any specific area may not mean that the area is not occupied. Therefore, relying strictly on point-specific survey results for historical occupancy information would likely create an incomplete picture of occupied areas. The extent of a stream reach that is occupied up- or downstream of a known occupied site is generally limited only by availability of suitable habitat. Therefore, we assume that for areas where the species has been documented, it was likely also present in the adjacent stream segments if adjacent segments were connected and contain suitable habitat.

In addition, this document discusses areas occupied at the time of listing. We are defining areas occupied at the time of listing to include streams for which we have loach minnow records up to 1986, when the species was first listed. These records include the Verde River and its tributary Beaver Creek; the White River and its tributary East Fork White River; Aravaipa Creek; the San Pedro River; Eagle Creek; the Blue River and its tributaries Campbell Blue, Dry Blue, and Little Blue creeks; the San Francisco River and its tributary Tularosa River; and the Gila River and its tributaries West Fork, Middle Fork, and East Fork Gila Rivers and Whitewater Creek. In addition, loach minnow were identified from several tributary streams following 1986. As no reintroduction efforts had taken place prior to discovering each of these populations, it is assumed they were occupied at listing, but undetected. We are therefore including these areas as occupied at listing: Deer Creek and Turkey Creek (tributaries to Aravaipa Creek); Frieborn Canyon and Pace Creek (tributaries to the Blue River); and North Fork East Fork Black River, and Negrito Creek (tributary to the Tularosa River).

Although suitable habitat existed in Hot Springs, Redfield Canyons, Fossil Creek, or Bonita Creek, loach minnow had not previously been documented there. In 2007, loach minnow were translocated into Hot Springs and Redfield canyons in Cochise County, Arizona (Robinson 2008a, pp. 2, 6; T. Robinson, AGFD, pers. comm. 2008b; D. Orabutt, AGFD, pers. comm. 2009); both of these streams are tributaries to the San Pedro River. Fish were also translocated into Fossil Creek, a tributary to the Verde River in Gila County, Arizona (Carter 2007a, p. 1; Carter 2008a, p. 1; Robinson 2009b, p. 9; Orabutt and Robinson 2010, in draft, p. 12). In 2008, loach minnow were translocated into Bonita Creek, a tributary to the Gila River in Graham County, Arizona (H. Blasius, BLM, pers. comm. 2008; D. Orabutt, AGFD, pers. comm. 2009). Augmentations with additional fish will occur for the next several years. Monitoring will be conducted at each of these sites to determine if populations ultimately become established at these new locations.

Loach minnow is now common only in Aravaipa Creek, the Blue River, and limited portions of the San Francisco, upper Gila, and Tularosa rivers in New Mexico. Since listing, loach minnow have been found in small tributary

streams, including Pace, Frieborn, Negrito, Turkey, and Deer creeks (Stefferud and Reinthal 2005, pp. 16-21; Paroz and Propst 2007, p. 16; NMDGF 2008). In addition, two previously undocumented populations of loach minnow have been discovered, one in Eagle Creek (Knowles 1994, p. 1; Marsh

et al

. 2003, p. 666) and one in the North Fork East Fork Black River (Bagley

et al

. 1997, p. 8). However, following a wildfire in the Black River watershed, a salvage rescue operation in the area known to be occupied by the loach minnow in 2004 resulted in the capture of only two loach minnow (S. Gurtin, AGFD, pers. comm. 2004). Both of these newly identified populations appear to be very small, but each represents a remnant portion of the historical range that was thought to be extirpated. Little information is available on the White River population due to the proprietary nature of Tribal survey information. Historical and current records for loach minnow are summarized in three databases (ASU 2002, AGFD 2004, NMDGF 2008), which are referenced throughout this document.

Previous Federal Actions

The spikedace was listed as threatened on July 1, 1986 (51 FR 23769); the loach minnow was listed as threatened on October 28, 1986 (51 FR 39468). The Service received a petition to uplist these species from threatened to endangered status on September 22, 1993. On July 11, 1994, we published 90-day and 12-month findings on the petition to amend the List of Threatened and Endangered Wildlife (59 FR 35303). We found that the petitioners presented substantial scientific information indicating that reclassifying spikedace and loach minnow as endangered was warranted but precluded by other listing actions (59 FR 35303). We restated this conclusion on January 8, 2001 (66 FR 1295), and considered the reclassification of spikedace and loach minnow each year in our Candidate Notice of Review. Our most recent Candidate Notice of Review was published on November 9, 2009 (74 FR 57804).

We designated critical habitat for both species on March 8, 1994 (59 FR 10898 (loach minnow); 59 FR 10906 (spikedace)). Those critical habitat designations were set aside by court order in

Catron County Board of Commissioners, New Mexico

v.

U.S. Fish and Wildlife Service,

CIV No. 93-730 HB (D.N.M. 1994) due to our failure to analyze the effects of critical habitat designation under the National Environmental Policy Act (NEPA) (42 U.S.C. 4321

et seq.

).

We subsequently published a proposed critical habitat designation on December 10, 1999 (64 FR 69324), and a final critical habitat designation on April 25, 2000 (65 FR 24328). However, in

New Mexico Cattle Growers' Association and Coalition of Arizona/New Mexico Counties for Stable Economic Growth

v.

United States Fish and Wildlife Service,

CIV 02-0199 JB/LCS (D.N.M), the plaintiffs challenged the April 25, 2000, critical habitat designation for the spikedace and loach minnow because the economic analysis had been prepared using the same methods that the Tenth Circuit had held to be invalid. The Service agreed to a voluntary vacatur of the critical habitat designation, except for the Tonto Creek Complex. On August 31, 2004, the United States District Court for the District of New Mexico set aside the April 25, 2000, critical habitat designation in its entirety and remanded it to the Service for preparation of a new proposed and final designation.

On December 20, 2005, we published a proposed critical habitat designation (70 FR 75546), and on March 21, 2007, we published a final critical habitat designation (72 FR 13356) for the spikedace and loach minnow. In

Coalition of Arizona/New Mexico Counties for Stable Economic Growth, et al

. v.

Salazar, et al

. (D.N.M.), two sets of plaintiffs challenged the Service's critical habitat designation for the spikedace and the loach minnow on the grounds that we designated critical habitat without adequate delineation or justification. We filed a motion for voluntary remand of the final rule on February 2, 2009, in order to reconsider the final rule in light of a recently issued Department of the Interior Solicitor's Opinion, which discusses the Secretary of the Interior's authority to exclude areas from a critical habitat designation under section 4(b)(2) of the ESA. On May 4, 2009, the Court granted our motion for voluntary remand.

There are differences in the areas included in this proposed designation from those included in the critical habitat designations published in 1994, 2000, and 2007. We have gained new information on species' distribution since the 1994 designation. We have acknowledged the flaws in the 2007 designation through our voluntary vacatur. This proposal is most similar to the 2000 designation. However, in contrast to the 2000 designation, we have not included every complex for spikedace and for loach minnow. Instead, we have attempted to consider occupancy data and habitat parameters specific to each species, and identified some areas that are suitable for one or the other species, but not both. While there is still considerable overlap in the designation, so that most areas are designated for both species, we have included some areas only for spikedace or only for loach minnow within this proposed designation.

For more information on previous Federal actions concerning the spikedace and loach minnow, refer to previous publications, including listing documents published in 1985 and 1986 (50 FR 25380, June 18, 1985; 50 FR 25390, June 18, 1985; 51 FR 39468, October 28, 1986; 51 FR 23769, July 1, 1986), as well as previous critical habitat designations in 1994 (59 FR 10898, March 8, 1994; 59 FR 10906, March 8, 1994), 1999 and 2000 (64 FR 69324, December 10, 1999; 65 FR 24328, April 25, 2000), and 2005 and 2007 (70 FR 75546, December 20, 2005; 72 FR 13356, March 21, 2007).

Summary of Factors Affecting the Species

Under the Act and our implementing regulations, a species may warrant listing if it is endangered or threatened throughout all or a significant portion of its range. Both spikedace and loach minnow currently exist in a small portion of their historical range (10 percent, or less, for spikedace, and 15 to 20 percent for loach minnow), and the threats continue throughout its range. Accordingly, our assessment and determination applies to each species throughout its entire range.

Section 4 of the Act (16 U.S.C. 1533), and implementing regulations (50 CFR part 424), set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors: (1) The present or threatened destruction, modification, or curtailment of its habitat or range; (2) overutilization for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) the inadequacy of existing regulatory mechanisms; or (5) other natural or manmade factors affecting its continued existence. In making this finding, information pertaining to spikedace and loach minnow, in relation to the five factors provided in section 4(a)(1) of the Act, are discussed below.

In considering what factors might constitute threats to a species, we must look beyond the exposure of the species to a factor to evaluate whether the species may respond to the factor in a way that causes actual impacts to the species. If there is exposure to a factor

and the species responds negatively, the factor may be a threat and we attempt to determine how significant a threat it is. The threat is significant if it drives, or contributes to, the risk of extinction of the species such that the species warrants listing as endangered or threatened as those terms are defined in the Act.

A. The Present or Threatened Destruction, Modification, or Curtailment of Habitat or Range

The majority of historical native habitat for spikedace and loach minnow has been altered or destroyed. Activities such as groundwater pumping, surface water diversions, impoundments, dams, channelization (straightening of the natural watercourse, typically for flood control purposes), improperly managed livestock grazing, wildfire, agriculture, mining, road building, residential development, and recreation all contribute to habitat loss and stream habitat degradation in Arizona and New Mexico (Minckley and Deacon 1991, pp. 15-18; Tellman

et al

. 1997, pp. 1, 4; Propst 1999, pp. 14-15; Minckley and Marsh 2009, pp. 24-48).

The aforementioned activities are human-caused; thus the local and regional effects of most of these activities are expected to increase with an increasing local human population. As of 2005, Arizona was recognized as the second fastest in Statewide population growth in the nation. The population of the State of Arizona is projected to grow by 66 percent by the year 2030, while the population in New Mexico is expected to grow by 33 percent (Southwest Climate Change 2009, p. 1). Arizona experienced a 28.6 percent population growth from 2000 to 2009, while New Mexico experienced growth at 10.5 percent during the same period (U.S. Census Bureau 2010, pp. 1, 3). An example of this population growth is on the Verde River (Yavapai County, Arizona), which likely includes a remnant spikedace population, and is important recovery habitat for spikedace and loach minnow. Yavapai County experienced a 28.8 percent increase in human population between 2000 and 2009. Groundwater use for municipal, industrial, and agricultural purposes has continued to increase since 1971 (Arizona Water Atlas 2010, p. 292) which increases the competition for the limited water resources used by spikedace and loach minnow.

Portions of some rivers receive protection as specially designated areas. In the upper Gila River, spikedace and loach minnow habitat receives some protection along the portions of the river that flow through the U.S. Forest Service Gila Wilderness and the Gila River Research Natural Area, which have use and access restrictions. Some portions of the river in the Gila National Forest are still affected by past and present uses within the watershed and riparian zone, such as grazing, timber harvest, and road development, and by water diversion for public and private uses. Other areas designated for special uses and subject to access and use restrictions include the Blue Range Primitive Area, the lower Gila River Bird Habitat Management Area, and the Gila River Research Natural Area.

Water Withdrawals

Water resources are limited in the Southwestern United States and have led to the conversion of portions of habitat to intermittent streams or reservoirs unsuitable for spikedace or loach minnow. Growing water demands reduce southern Arizona perennial surface water in the Gila Basin, and threaten aquatic species. Historically, water withdrawals led to the conversion of large portions of flowing streams into intermittent streams, large reservoirs, or dewatered channels, thus eliminating suitable spikedace and loach minnow habitat in impacted areas (Propst

et al

. 1986, p. 3; Tellman

et al

. 1997, pp. 37, 50, 63-64, 66, 103). These habitat changes, together with the introduction of nonnative fish species (see factors C and E), have resulted in the extirpation of spikedace and loach minnow throughout an estimated 80 to 90 percent of their historical ranges.

After leaving the Mogollon Mountains in New Mexico, the Gila River is affected by agricultural and industrial water diversions, impoundment, and channelization. In the Gila River, agricultural diversions and groundwater pumping have caused declines in the water table, and surface flows in the central portion of the river basin are diverted for agriculture (Leopold 1997, pp. 63-64; Tellman

et al

. 1997, pp. 101-104; Arizona Department of Water Resources 2000, pp. 16-17). On the mainstem Salt River, impoundments have permanently limited the flow regime and suitability for spikedace or loach minnow.

Of particular concern to spikedace and loach minnow survival in the Gila River is the implementation of Public Law 108-451, the Arizona Water Settlements Act. Title II of the Arizona Water Settlements Act would facilitate the exchange of Central Arizona Project water within and between southwestern river basins in Arizona and New Mexico. The Arizona Water Settlements Act may also result in the construction of new water development projects. For example, Section 212 of the Arizona Water Settlements Act pertains to the New Mexico Unit of the Central Arizona Project. Development of the New Mexico Unit may facilitate diversion of water via the construction of an on- or off-stream reservoir on the Gila River in New Mexico. Implementation of the Arizona Water Settlement Act is in its early stages on the Gila River, such that the exact location, scope, scale, timing, and effects of those efforts on the spikedace and its habitat in the Gila River cannot be definitively analyzed at present. However, should water be diverted from the river, there would be a diminished flow that could potentially result in direct and indirect loss and degradation of habitat for aquatic and riparian species. Because the Gila River is a stronghold for spikedace and loach minnow, impacts to those portions of the Gila River in New Mexico are of particular concern for the persistence of these species.

The San Francisco River has undergone sedimentation, riparian habitat degradation, and extensive water diversion and at present has an undependable water supply throughout much of its length. Groundwater pumping also poses a threat to surface flows in the remaining spikedace and loach minnow habitat in Eagle Creek. Groundwater withdrawal in Eagle Creek, primarily for water supply for a large open-pit copper mine at Morenci, dries portions of the stream (Sublette

et al

. 1990, p. 19; Service 2005; Propst

et al

. 1986, p. 7). Mining is the largest industrial water user in southeastern Arizona. The Morenci mine on Eagle Creek is North America's largest producer of copper, covering 60,000 acres. Water for the mine is imported from the Black River, diverted from Eagle Creek as surface flows, or withdrawn from the Upper Eagle Creek Well Field (Arizona Department of Water Resources 2009, p. 1).

Aravaipa Creek is relatively protected from further habitat loss because it is within a Bureau of Land Management (BLM) Wilderness and is a Nature Conservancy preserve. However, Aravaipa Creek is affected by upstream uses in the watershed, primarily groundwater pumping for irrigation. Irrigation can reduce creek flows, as crop irrigation uses large amounts of water, especially during the summer months when the creek flows are already at their lowest. Increased groundwater pumping from wells is known to be linked to reduced creek flows (Fuller 2000, pp. 4-8).

Water depletion is also a concern for the Verde River. In 2000, the Arizona Department of Water Resources (2000,

p. 1-1) reported that the populations of major cities and towns within the Verde River watershed had more than doubled in the last 20 years, resulting in more than a 39 percent increase in municipal water usage. The Arizona Department of Water Resources (2000, p. 1-1) anticipated that human populations in the Verde River watershed are expected to double again before 2040, resulting in more than a 400 percent increase over the 2000 water usage. The middle and lower Verde River has limited or no flow during portions of the year due to agricultural diversion and upstream impoundments, and has several impoundments in its middle reaches, which could expand the area of impacted spikedace and loach minnow habitat. The Little Chino basin within the Verde River watershed has already experienced significant groundwater declines that have reduced flow in Del Rio Springs (Arizona Department of Water Resources 2000, pp. 1-1, 1-2). Blasch

et al

. (2006, p. 2) suggests that groundwater storage in the Verde River watershed has already declined due to groundwater pumping and reductions in natural channel recharge resulting from streamflow diversions.

Also impacting water in the Verde River, the City of Prescott, Arizona, experienced a 22 percent increase in population between 2000 and 2005 (U.S. Census Bureau 2010b, p. 1), averaging around 4 percent growth per year (City of Prescott 2010, p. 1). In addition, the towns of Prescott Valley and Chino Valley experienced growth rates of 66 and 67 percent, respectively (Arizona Department of Commerce 2009a, p. 1; 2009b, p. 1). This growth is facilitated by groundwater pumping in the Verde River basin. In 2004, the cities of Prescott and Prescott Valley purchased a ranch in the Big Chino basin in the headwaters of the Verde River, with the intent of drilling new wells to supply up to approximately 4,000 acre-feet (AF) of groundwater per year. If such drilling occurs, it could have serious adverse effects on the mainstem and tributaries of the Verde River. Scientific studies have shown a link between the Big Chino aquifer and spring flows that form the headwaters of the Verde River. It is estimated that 80 to 86 percent of baseflow in the upper Verde River comes from the Big Chino aquifer (Wirt 2005, p. G8). However, while these withdrawals could potentially dewater the upper 42 kilometers (km) (26 miles (mi)) of the Verde River (Wirt and Hjalmarson 2000, p. 4), it is uncertain that this project will occur given the legal and administrative challenges it faces. This upper portion of the Verde River is considered currently occupied by spikedace, and barrier construction and stream renovation plans are underway with the intention of using this historically occupied area for recovery of native fishes including loach minnow. Reductions of available water within this reach could preclude its use for recovery purposes. This area is currently considered occupied by spikedace, that are considered genetically (Tibbets 1993, pp. 25-29) and morphologically (Anderson and Hendrickson 1994, pp. 148, 150-154) distinct from all other spikedace populations.

There are numerous surface water diversions in spikedace and loach minnow habitats, including the Verde River, Blue River, San Francisco River, Gila River, and Eagle Creek. Larger dams may prevent movement of fish between populations and dramatically alter the flow regime of streams through the impoundment of water (Ligon

et al

. 1995, pp. 184-189). These diversions also require periodic maintenance and re-construction, resulting in potential habitat damages and inputs of sediment into the active stream.

Water withdrawals have occurred historically, and continue to occur, throughout the ranges of spikedace and loach minnow. Groundwater pumping and surface diversions used for agricultural, industrial, and municipal purposes can lead to declines in the water table and dewatering of active stream channels. Ongoing water withdrawals are known to occur on the Gila, San Francisco, and Verde rivers, and are occurring at limited levels, with the potential for increased withdrawal, on Aravaipa Creek.

Stream Channelization

Sections of many Gila Basin rivers and streams have been, and continue to be, channelized for flood control, which disrupts natural channel dynamics (sediment scouring and deposition) and promotes the loss of riparian plant communities. Channelization changes the stream gradient above and below the channelization. Water velocity increases in the channelized section, which results in increased rates of erosion of the stream and its tributaries, accompanied by gradual deposits of sediment in downstream reaches that may increase the risk of flooding (Emerson 1971, p. 326; Simpson 1982, p. 122). Channelization can affect spikedace and loach minnow habitat by reducing its complexity, eliminating cover, reducing nutrient input, improving habitat for nonnative species, changing sediment transport, altering substrate size, increasing flow velocities, and reducing the length of the stream (and therefore the amount of aquatic habitat available) (Gorman and Karr 1978, pp. 512-513; Simpson 1982, p. 122; Schmetterling

et al

. 2001, pp. 7-10). Historical and ongoing channelization will continue to contribute to riparian and aquatic habitat decline most notably eliminating cover and reducing nutrient input.

Water Quality

In the past, the threat from water pollution was due primarily to catastrophic pollution events (Rathbun 1969, pp. 1-5; Eberhardt 1981, pp. 3-6, 8-10) or chronic leakage (Eberhardt 1981, pp. 2, 16) from large mining operations. Although this is not as large a problem today as it was historically, some damage to spikedace and loach minnow populations still occurs from occasional spills or chronic inability to meet water quality standards (

United States

v.

ASARCO,

No. 98-0137 PHX-ROS (D. Ariz. June 2, 1998)). Mine tailings from a number of past and present facilities throughout the Gila Basin would threaten spikedace populations if catastrophic spills occur (Arizona Department of Health Services 2010, p. 3). Spills or discharges have occurred in the Gila River and affected streams within the watersheds of spikedace and loach minnow, including the Gila River, San Francisco River, San Pedro River, and some of their tributaries (Environmental Protection Agency 1997, pp. 24-67; Arizona Department of Environmental Quality 2000, p. 6; Church

et al

. 2005, p. 40; Arizona Department of Environmental Quality 2007, p. 1).

In January of 2006, the Arizona Department of Environmental Quality announced that it had been conducting a remedial investigation at the Klondyke Tailings site on Aravaipa Creek, which currently supports one of the two remaining populations where spikedace and loach minnow are considered common. The Klondyke tailings site was a mill that processed ore to recover lead, zinc, copper, silver, and gold between the 1920s and the 1970s. There are eight contaminants in the tailings and soil at the Klondyke tailings site that are at levels above regulatory limits. These contaminants include antimony, arsenic, beryllium, cadmium, copper, lead, manganese, and zinc. Samples of shallow groundwater collected at the site contained arsenic, beryllium, cadmium, chromium, lead, and nickel above regulatory limits (Arizona Department of Environmental Quality 2006, p. 2). A preliminary study in Aravaipa Creek has found high levels of

lead in two other native fish species, Sonora sucker (

Catostomus insignis

) and roundtail chub (

Gila robusta

), as well as in the sediment and in some of the invertebrates. These lead levels are high enough that they could negatively impact reproduction (P. Reinthal, University of Arizona pers. comm. 2010). We do not know with certainty whether these levels of lead would affect spikedace or loach minnow, but we assume the same negative effects would occur.

Pollution is increasingly more widespread and more often from non-point sources. Urban and suburban development is one source of non-point pollution. Increasing the area subject to runoff from roads, golf courses, and other sources of petroleum products, pesticides, and other toxic materials, can cause changes in fish communities (Wang

et al

. 1997, pp. 6, 9, 11). Nutrient and sediment loads are increasing in urban areas (King

et al

. 1997, pp. 7-24, 38, 39) and, combined with depleted stream flows, can be serious threats to aquatic ecosystem during some periods of the year. Bridges and roads increase with increasing rural and urban populations in Arizona (Arizona Department of Transportation 2000, pp. 1-3), and pose significant risks to the fish from increases in toxic materials along roadways (Trombulak and Frissall 2000, pp. 22-24). As noted previously, human populations within the ranges of spikedace and loach minnow are expected to increase over the next 20 years. Therefore, we expect a corresponding increase in non-point source pollution.

Based on historical records and long-term tree-ring records, wildfires have increased in the ponderosa pine forests of the Southwest, including the range of the spikedace and loach minnow (Swetnam and Betancourt 1990, pp. 1017, 1019; Swetnam and Betancourt 1998, pp. 3131-3135). This is due to a combination of decades of fire suppression, increases in biomass due to increased precipitation after 1976, and warming temperatures coupled with recent drought conditions (University of Arizona 2006, pp. 1, 3). As wildfires increase, so does the use of fire retardant chemical applications. Some fire retardant chemicals are ammonia-based, which is toxic to aquatic wildlife; however, many formulations also contain yellow prussiate of soda (sodium ferrocyanide), which is added as an anticorrosive agent. Such formulations are toxic for fish, aquatic invertebrates, and algae (Angeler

et al

. 2006, pp. 171-172; Calfee and Little 2003, pp. 1527-1530; Little and Calfee 2002, p. 5; Buhl and Hamilton 1998, p. 1598; Hamilton

et al

. 1998, p. 3; Gaikwokski

et al

. 1996, pp. 1372-1373). Toxicity of these formulations is enhanced by sunlight (Calfee and Little 2003, pp. 1529-1533). In a 2008 biological opinion issued by the U.S. Fish and Wildlife Service to the Forest Service on the nationwide use of fire retardants, the U.S. Fish and Wildlife Service concluded that the use of fire retardants can cause mortality to fish by exposing them to ammonia. We concluded in the opinion that the proposed action, which included the application of fire retardants throughout the range of the species, was likely to jeopardize the continued existence of the spikedace and loach minnow (Service 2008a).

Severe wildfires capable of extirpating or decimating fish populations are a relatively recent phenomenon, and result from the cumulative effects of historical or ongoing grazing (removes the fine fuels needed to carry fire) and fire suppression (Madany and West 1983, pp. 665-667; Savage and Swetnam 1990, p. 2374; Swetnam 1990, p. 12; Touchan

et al

. 1995, pp. 268-271; Swetnam and Baisan 1996, p. 29; Belsky and Blumenthal 1997, pp. 315-316, 324-325; Gresswell 1999, pp. 193-194, 213). Historical wildfires were primarily cool-burning understory fires with return intervals of 4 to 8 years in ponderosa pine (Swetnam and Dieterich 1985, pp. 390, 395). Cooper (1960, p. 137) concluded that prior to the 1950s, crown fires were extremely rare or nonexistent in the region. However, since 1989, high-severity wild fires, and subsequent floods and ash flows, have caused the extirpation of several populations of Gila trout in the Gila National Forest, New Mexico (Propst

et al

. 1992, pp. 119-120, 123; Brown

et al

. 2001, pp. 140-141). It is not known if spikedace or loach minnow have suffered local extirpations; however, native fishes, including spikedace and loach minnow, in the West Fork Gila River, showed 60 to 80 percent decreases in population following the Cub Fire in 2002, due to flooding events after the fire (Rinne and Carter 2008, pp. 171). Increased fines and ash may be continuing to affect the populations on the West Fork Gila, near the Gila Cliff Dwellings (D. Propst. NMDGF, pers. comm. 2004).

Effects of fire may be direct and immediate or indirect and sustained over time. Because spikedace and loach minnow are found primarily in the lower elevation, higher-order streams, they are most likely affected by the indirect effects of fire (

e.g.,

ash flows), not direct effects (

e.g.,

drastic changes in pH, ammonium concentrations). Indirect effects of fire include ash and debris flows, increases in water temperature, increased nutrient inputs, and sedimentation (Propst

et al

. 1992, pp. 119-120; Gresswell 1999, pp. 194-211; Rinne and Carter 2008, pp. 169-171). Of these, ash flows probably have the greatest effect on spikedace and loach minnow. Ash and debris flows may occur months after fires, when barren soils are eroded during monsoonal rain storms (Bozek and Young 1994, pp. 92-94). Ash and fine particulate matter created by fire can fill the interstitial spaces between gravel particles, eliminating spawning habitat or, depending on the timing, suffocating eggs that are in the gravel. Ash and debris flows can also decimate aquatic invertebrate populations that the fish depend on for food (Molles 1985, p. 281).

Recreation

The impacts to spikedace and loach minnow from recreation can include movement of livestock along streambanks, trampling, loss of vegetation, and increased danger of fire (Northern Arizona University 2005, p. 136; Monz

et al

. 2010, pp. 553-554). In the arid Gila River Basin, recreational impacts are disproportionately distributed along streams as a primary focus for recreation (Briggs 1996, p. 36). Within the range of spikedace and loach minnow, the majority of the occupied areas occur on Federal lands, which are managed for recreation and other purposes. Spikedace and loach minnow are experiencing increasing habitat impacts from such use in some areas. For example, Fossil Creek experienced an increase in trail use at one site, with an estimated 8,606 hikers using the trail in 1998, and an estimated 19,650 hikers using the trail in 2003. Dispersed camping also occurs in the area. The greatest impacts from camping were vegetation loss and litter (Northern Arizona University 2005, pp. 134-136). Similar impacts have been observed at Aravaipa Creek. Vegetation loss is often accompanied by soil compaction, which when combined with vegetation loss, can result in increased runoff and sedimentation in waterways (Monz

et al

. 2010, pp. 551-553; Andereck 1993, p. 2).

Roads and Bridges

Roads impact Gila River Basin streams (Dobyns 1981, pp. 120-129, 167, 198-201), including spikedace, loach minnow, and their habitats (Jones

et al

. 2000, pp. 82-83). The need for bridges and roads increases with increasing rural and urban populations in Arizona (Arizona Department of

Transportation 2000, pp. 1-3). In addition, existing roads and bridges have ongoing maintenance requirements that result in alterations of stream channels within spikedace and loach minnow habitats (Service 1994a, pp. 8-12; Service 1995a, pp. 10-12; Service 1995b, pp. 5-7; Service 1997a, pp. 10-15; Service 1997b, pp. 54-77). Bridge construction or repair causes channel alteration and, if not carefully executed, can result in long-term channel adjustments, altering habitats upstream and downstream. In some areas, low-water ford crossings exist within occupied spikedace and loach minnow habitats and cause channel modification and habitat disruption. Low-water crossings on general-use roads exist in a number of areas that may support spikedace and loach minnow. These crossings frequently require maintenance following minor flooding.

Repeated road repairs near the Gila Cliff Dwellings on the West Fork Gila River have occurred because the bridge span is too short to accommodate peak flows. This is a common problem on bridges that cross the Gila River, and on other rivers occupied by spikedace and loach minnow in the Southwest. In an attempt to protect bridges, large amounts of fill (such as boulders, rip rap, and dirt) are used to confine and redirect the river. Typically, this habitat alteration is detrimental to spikedace and loach minnow because it changes the channel gradient and substrate composition, and reduces habitat availability. Eventually, peak flows remove the fill material, roads and bridges are damaged, and the resulting repairs and reconstruction lead to additional habitat disturbance (Service 1998, 2002, 2005, 2008b, 2008c, 2009, 2010a).

Livestock Grazing

Livestock grazing has been one of the most widespread and long-term adverse impacts to native fishes and their habitat (Miller 1961, pp. 394-395, 399), but is one of the few threats where adverse effects to species such as spikedace and loach minnow are decreasing, due to improved management on Federal lands (Service 1997c, pp. 121-129, 137-141; Service 2001, pp. 50-67). This improvement occurred primarily by discontinuing grazing in the riparian and stream corridors. However, although adverse effects are less than in the past, livestock grazing within watersheds where spikedace and loach minnow and their habitats are located continues to cause adverse effects. These adverse effects occur through watershed alteration and subsequent changes in the natural flow regime, sediment production, and stream channel morphology (Platts 1990, pp. I-9—I-11; Belsky

et al

. 1999, pp. 1-3, 8-10; Service 2001, pp. 50-67).

Livestock grazing can destabilize stream channels and disturb riparian ecosystem functions (Platts 1990, pp. I-9—I-11; Armour

et al.

1991, pp. 7-10; Tellman

et al.

1997, pp. 20-21, 33, 47, 101-102). Improper livestock grazing can negatively affect spikedace and loach minnow through removal of riparian vegetation (Propst

et al.

1986, p. 3; Clary and Webster 1989, p. 1; Clary and Medin 1990, p. 1; Schulz and Leininger 1990, p. 295; Fleishner 1994, pp. 631-633, 635-636), which can result in reduced bank stability and higher water temperatures (Kauffman and Krueger 1984, pp. 432-434; Platts and Nelson 1989, pp. 453, 455; Fleishner 1994, pp. 635-636; Belsky

et al.

1999, pp. 2-5, 9-10). Livestock grazing can also cause increased sediment in the stream channel, due to streambank trampling and riparian vegetation loss (Weltz and Wood 1986, pp. 364-368; Pearce

et al.

1998, pp. 302, 307; Belsky

et al.

1999, p. 10). Livestock can physically alter the streambank through trampling and shearing, leading to bank erosion (Trimble and Mendel 1995, pp. 243-244; Belsky

et al.

1999, p. 1). In combination, loss of riparian vegetation and bank erosion can alter channel morphology, including increased erosion and deposition, increased sediment loads, downcutting, and an increased width-to-depth ratio, all of which lead to a loss of spikedace and loach minnow habitat components. Livestock grazing management also continues to include construction and maintenance of open stock tanks, which are often stocked with nonnative aquatic species harmful to spikedace and loach minnow (Service 1997b, pp. 54-77) if they escape or are transported to waters where these native fish occur.

Summary of Factor A

Impacts associated with roads and bridges, changes in water quality, and recreation have altered or destroyed many of the rivers, streams, and watershed functions in the ranges of the spikedace and loach minnow. As discussed above, activities such as groundwater pumping, surface water diversions, impoundments, dams, channelization, improperly managed livestock grazing, wildfire, agriculture, mining, road building, residential development, and recreation all contribute to riparian habitat loss and degradation of aquatic resources in Arizona and New Mexico. Changes in flow regimes are expected to continue into the foreseeable future. Therefore, we find that the spikedace and loach minnow are threatened by the destruction, modification, or curtailment of their habitats.

B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes

Currently, collection of spikedace and loach minnow in Arizona is prohibited by Arizona Game and Fish Commission Order 40, except where such collection is authorized by special permit (AGFD 2009, p. 5). The collection of these species is prohibited in the State of New Mexico except by special scientific permit (NMDGF 2010, p. 4). Because spikedace and loach minnow do not grow larger than 80 mm (3 in), we believe that angling for this species is not a threat. No known commercial uses exist for spikedace or loach minnow. A limited amount of scientific collection occurs, but does not pose a threat to these species because it is regulated by the States. Therefore, we have determined that overutilization for commercial, recreational, scientific, or educational purposes is not a threat to spikedace or loach minnow.

C. Disease or Predation

The introduction and spread of nonnative species has been identified as one of the primary factors in the continuing decline of native fishes throughout North America and particularly in the Southwest (Miller 1961, pp. 365, 397-398; Lachner

et al.

1970, p. 21; Ono

et al.

1983, pp. 90-91; Carlson and Muth 1989, pp. 222, 234; Fuller

et al.

1999, p. 1). Miller

et al.

(1989, pp. 22, 34, 36) concluded that introduced nonnative species were a causal factor in 68 percent of fish extinctions in North America in the last 100 years. For the 70 percent of fish species that are still extant, but are considered to be endangered or threatened, introduced nonnative species are a primary cause of the decline (Lassuy 1995, pp. 391-394). Release or dispersal of new nonnative aquatic organisms is a continuing phenomenon in the species' range (Rosen

et al.

1995, p. 254). Currently, all native fishes in Arizona and 80 percent of native fishes in the Southwest are on either State or Federal protection lists.

Nonnative fish introductions in the Southwestern United States began before 1900, and have steadily increased in frequency (Rinne and Stefferud 1996b, p. 29). New species are continually being introduced through various mechanisms, including aquaculture, aquarium trade, sport fish stocking, live bait use, interbasin water

transfers, and general “bait bucket transport,” where people move fish from one area to another without authorization and for a variety of purposes (Service 1994b, pp. 12-16; Service 1999, pp. 24-59). Nearly 100 kinds of nonnative fishes have been stocked or introduced into streams in the Southwest (Minckley and Marsh 2009, p. 51). Nonnative fishes known to occur within the historical range of the spikedace include channel catfish (

Ictalurus punctatus

), flathead catfish (

Pylodictis olivaris

), red shiner (

Cyprinella lutrensis

), fathead minnow (

Pimephales promelas

), green sunfish (

Lepomis cyanellus

), largemouth bass (

Micropterus salmoides

), smallmouth bass (

Micropterus dolomieui

), rainbow trout (

Oncorhynchus mykiss

), mosquitofish (

Gambusia affinis

), carp (

Cyprinus carpio

), bluegill (

Lepomis macrochiris

), yellow bullhead (

Ameiurus natalis

), black bullhead (

Ameiurus melas

), and goldfish (

Carassius auratus

) (ASU 2002).

In the Gila River basin, introduction of nonnative species is considered a primary factor in the decline of native fish species (Minckley 1985, pp. 1, 68; Williams

et al.

1985, pp. 1-2; Minckley and Deacon 1991, pp. 15-17; Douglas

et al.

1994, pp. 9-11; Clarkson

et al.

2005 p. 20; Olden and Poff 2005, pp. 79-87). Aquatic and semi-aquatic mammals, reptiles, amphibians, crustaceans, mollusks (snails and clams), parasites, disease organisms, and aquatic and riparian vascular plants outside of their historical range, have all been documented to adversely affect aquatic ecosystems (Cohen and Carlton 1995, pp. i-iv). The effects of nonnative fish competition on spikedace and loach minnow can be classified as either interference or exploitive. Interference competition occurs when individuals directly affect others, such as by fighting, producing toxins, or preying upon them (Schoener 1983, p. 257). Exploitive competition occurs when individuals affect others indirectly, such as through use of common resources (Douglas

et al.

1994, p. 14). Interference competition in the form of predation is discussed here, while a discussion of the history of nonnative species introductions and resulting interference competition for resources are discussed under Factor E below.

Predation

Nonnative channel catfish, flathead catfish, and smallmouth bass all prey on spikedace and loach minnow, as indicated by prey remains of native fishes in the stomachs of these species (Propst

et al.

1986, p. 82; Propst

et al.

1988, p. 64; Bonar

et al.

2004, pp. 13, 16-21). Channel catfish move into riffles to feed, preying on the same animals most important to loach minnows, while juvenile flathead catfish prey on loach minnows (Service 1991a, p. 5). Smallmouth bass are known to co-occur with spikedace and are documented predators of the species (Service 1991b, p. 6). Green sunfish are also thought to be a predator, likely responsible for replacement of native species like spikedace and loach minnow. While no direct studies have been completed on predation by green sunfish on spikedace or loach minnow, they are a known predator of fish that size, and they occur within areas occupied by these species.

Declines of native fish species appear linked to increases in nonnative fish species. For example, in 1949, 52 spikedace were collected at Red Rock on the Gila River, while channel catfish composed only 1.65 percent of the 607 fish collected. However, in 1977, only six spikedace were located at the same site, and the percentage of channel catfish had risen to 14.5 percent of 169 fish collected. The decline of spikedace and the increase of channel catfish is likely related (Anderson 1978, pp. 2, 13, 50-51). Similarly, interactions between native and nonnative fishes were observed in the upper reaches of the East Fork of the Gila River. Prior to the 1983 and 1984 floods in the Gila River system, native fish were limited, with spikedace being rare or absent, while nonnative channel catfish and smallmouth bass were moderately common. After the 1983 flooding, adult nonnative predators were generally absent, and spikedace were collected in moderate numbers in 1985 (Propst

et al.

1986, p. 83).

The majority of areas considered occupied by spikedace and loach minnow have seen a shift from a predominance of native fishes to a predominance of nonnative fishes. For spikedace, this is best demonstrated on the upper Verde River, where native species dominated the total fish community at greater than 80 percent from 1994 to 1996, before dropping to approximately 20 percent in 1997 and 19 percent in 2001. At the same time, three nonnative species increased in abundance between 1994 and 2000 (Rinne

et al.

2004, pp. 1-2). Similar changes in the dominance of nonnative fishes have occurred on the Middle Fork Gila River, with a 65 percent decline of native fishes between 1988 and 2001 (Propst 2002, pp. 21-25).

In other areas, nonnative fishes may not dominate the system, but their abundance has increased, while spikedace and loach minnow abundance has declined. This is the case for the Cliff-Gila Valley area of the Gila River, where nonnative fishes increased from 1.1 percent to 8.5 percent, while native fishes declined steadily over a 40-year period (Propst

et al.

1986, pp. 27-32). At the Redrock and Virden valleys on the Gila River, the relative abundance in nonnative fishes in the same time period increased from 2.4 percent to 17.9 percent (Propst

et al.

1986, pp. 32-34). Four years later, the relative of abundance of nonnative fishes increased to 54.7 percent at these sites (Propst

et al.

1986, pp. 32-36). The percentage of nonnative fishes increased by almost 12 percent on the Tularosa River between 1988 and 2003, while on the East Fork Gila River, nonnative fishes increased to 80.5 percent relative abundance in 2003 (Propst 2005, pp. 6-7, 23-24). Nonnative fishes are also considered a management issue in other areas including Eagle Creek, the San Pedro River, West Fork Gila River, and to a lesser extent on the Blue River and Aravaipa Creek.

Generally, when the species composition of a community shifts in favor of nonnative fishes, a decline in spikedace or loach minnow abundance occurs (Olden and Poff 2005, pp. 79-86). Propst

et al.

(1986, p. 38) noted this during studies of the Gila River between 1960 and 1980. While native species, including spikedace, dominated the study area initially, red shiner, fathead minnow, and channel catfish were more prevalent following 1980. Propst

et al.

(1986, pp. 83-86) noted that drought and diversions for irrigation first brought a decline in habitat quality, followed by the establishment of nonnative fishes in remaining suitable areas, thus reducing the availability and utility of these areas for native species. It should be noted that the effects of nonnative fishes often occur with, or are exacerbated by, changes in flow regimes or declines in habitat conditions (see Factor A above) and should be considered against the backdrop of historical habitat degradation that has occurred over time (Minckley and Meffe 1987, pp. 94, 103; Rinne 1991, p. 12).

Nonnative channel catfish, flathead catfish, and smallmouth bass are present in most spikedace habitats, including the Verde River (Minckley 1993, pp. 7-13; Jahrke and Clark 1999, pp. 2-7; Rinne 2004, pp. 1-2; Bahm and Robinson 2009, pp. 1-4; Robinson and Crowder 2009, pp. 3-5); the Gila River (Propst

et al.

1986, pp. 14-31; Springer 1995, pp. 6-10; Jakle 1995, pp. 5-7; Propst

et al.

2009, pp. 14-17); the San Pedro River (Jakle 1992, pp. 3-5; Minckley 1987, pp. 2, 16); the San Francisco River (Papoulias

et al.

1989, pp. 77-80; Propst

et al.

2009, pp. 5-6);

the Blue River (ASU 1994, multiple reports; ASU 1995, multiple reports; Clarkson

et al.

2008, pp. 3-4); the Tularosa River, East Fork Gila River, West Fork Gila River, and Middle Fork Gila River (Propst

et al.

2009, pp. 7-13; NMDGF 2009

in draft,

pp. 2-14); and Eagle Creek (Marsh

et al.

2003, p. 667; ASU 2008, multiple reports; Bahm and Robinson 2009a, pp. 2-6).

Pilger

et al.

(2010, pp. 311-312) studied the food webs in six reaches of the Gila River. Their study attempted to quantify resource overlap among native and nonnative fishes. Their study determined that nonnative fishes consumed a greater diversity of invertebrates and more fish than native species, and that nonnative fishes consumed predacious invertebrates and terrestrial invertebrates more frequently than native fishes. They found that, on average, the diets of adult nonnative fishes were comprised of 25 percent fish, but that there was high variability among species. Only 6 percent of the diet of channel catfish was fish, while fish made up 84 percent of the diet of flathead catfish. They found that both juvenile and adult nonnative species could pose a predation threat to native fishes.

As noted below under Factor E, nonnative fishes also compete for resources with native fishes. While nonnative fishes were preying on native fishes, small-bodied nonnative fishes are potentially affecting native fishes through competition (discussed further under Factor E), so that native fishes are impacted by both competition and predation. Pilger

et al.

(2010, p. 312) note that removal and preclusion of nonnative predators and competitors may be necessary for conservation of native fishes in the upper Gila River in order to mitigate the effects they have on native species. Pilger

et al.

(2010, p. 312) note that, in the upper Verde River, native fishes have declined precipitously since the mid-1990s, which may indicate that a stressor threshold has been crossed. They conclude that there are declining trends of native fish abundances in the upper Gila River, and that the coexistence of native and nonnative fishes there may indicate that the threshold has not been reached, but may be imminent.

Disease

Various parasites may affect spikedace and loach minnow. Asian tapeworm (

Bothriocephalus acheilognathi

) was introduced into the United States with imported grass carp (

Ctenopharyngodon idella

) in the early 1970s. It has since become well established in areas throughout the southwestern United States. The definitive host in the life cycle of Asian tapeworm is a cyprinid fish (carp or minnow), and therefore it is a potential threat to spikedace and loach minnow, as well as other native cyprinids in Arizona. The Asian tapeworm adversely affects fish health by impeding the digestion of food as it passes through the intestinal track. Emaciation and starvation of the host can occur when large enough numbers of worms feed off of the fish directly. An indirect effect is that weakened fish are more susceptible to infection by other pathogens. Asian tapeworm invaded the Gila River basin and was found during the Central Arizona Project's fall 1998 monitoring in the Gila River at Ashurst-Hayden Dam. It has also been confirmed from Bonita Creek in 2010 and from Fossil Creek in 2004 and 2010 (U.S. Fish and Wildlife Service National Wild Fish Health Survey 2004, 2010). This parasite can infect many species of fish and is carried into new areas along with nonnative fishes or native fishes from contaminated areas.

The parasite (

Ichthyophthirius multifiliis

) (Ich) usually occurs in deep waters with low flow and is a potential threat to spikedace and loach minnow. Ich has occurred in some Arizona streams, probably encouraged by high temperatures and crowding as a result of drought (Mpoame 1982, pp. 45-47). This parasite was observed being transmitted on the Sonora sucker (

Catostomus insignis

), although it does not appear to be host-specific and could be transmitted by other species (Mpoame 1982, p. 46). It has been found on desert and Sonoran suckers, as well as roundtail chub (Robinson

et al.

1998, p. 603). This parasite becomes embedded under the skin and within the gill tissues of infected fish. When Ich matures, it leaves the fish, causing fluid loss, physiological stress, and sites that are susceptible to infection by other pathogens. If Ich is present in large enough numbers, it can also impact respiration because of damaged gill tissue. There are recorded spikedace mortalities in captivity due to Ich. Ich is known to be present in Aravaipa Creek (Mpoame 1982, p. 46), which is currently occupied by both spikedace and loach minnow.

Anchor worm (

Lernaea cyprinacea

), an external parasite, is unusual in that it has little host specificity, infecting a wide range of fishes and amphibians. Infection by this parasite has been known to kill large numbers of fish due to tissue damage and secondary infection of the attachment site (Hoffnagle and Cole 1999, p. 24). Presence of this parasite in the Gila River basin is a threat to spikedace, loach minnow, and other native fishes. In July 1992, the BLM found anchor worms in Bonita Creek. They have also been documented in Aravaipa Creek and the Verde River (Robinson

et al.

1998, pp. 599, 603-605). Both spikedace and loach minnow occur in Bonita and Aravaipa Creeks.

Summary of Factor C

Both spikedace and loach minnow have been severely impacted by the presence of nonnative predators. Aquatic nonnative species have been introduced or spread into new areas through a variety of mechanisms, including intentional and accidental releases, sport stocking, aquaculture, aquarium releases, and bait-bucket release. Channel catfish, flathead catfish, and smallmouth bass appear to be the most prominent predators, although other species contribute to the decline of native fishes in the Southwest, including spikedace and loach minnow. Spikedace and loach minnow have been replaced by nonnative fishes in several Arizona streams. In addition to threats from predation, we also conclude that both spikedace and loach minnow are reasonably certain to become impacted by parasites that have been documented in the Gila River basin and that are known to adversely affect or kill fish hosts. For these reasons, we find that the spikedace and loach minnow are threatened by disease and predation.

D. The Inadequacy of Existing Regulatory Mechanisms

Because of the complex, indirect, and cumulative nature of many of the threats to spikedace and loach minnow, existing regulatory mechanisms are often inadequate to address or ameliorate the threats. Causes of the declining status of these species are a mix of many human activities and natural events, which makes it difficult to remove those threats through regulation. Spikedace is listed by New Mexico as an endangered species, while loach minnow is listed as threatened (Bison-M 2010). These designations provide the protection of the New Mexico Wildlife Conservation Act. However, the primary focus of the New Mexico Wildlife Conservation Act and other State legislation is to prevent actual destruction or harm to individuals of the species. Since most of the threats to these species come from actions that do not directly kill individuals, but indirectly result in their death from the lack of some habitat requirement or an inability to reproduce, the State protection is only

partially effective for this species. Similarly, spikedace and loach minnow are listed as species of concern by the State of Arizona. The listing under the State of Arizona law does not provide protection to the species or their habitats; however, AGFD regulations prohibit possession of these species (AGFD 2006, Appendix 10, p. 4).

As discussed above under Factor C, the introduction and spread of nonnative aquatic species is a major threat to spikedace and loach minnow. Neither the States of New Mexico and Arizona nor the Federal government has adequate regulatory mechanisms to address this issue. Programs to introduce, augment, spread, or permit such actions for nonnative sport, bait, aquarium, and aquaculture species continue. Regulation of these activities does not adequately address the spread of nonnative species, as many introductions are conducted through incidental or unregulated actions.

New Mexico water law does not include provisions for instream water rights to protect fish and wildlife and their habitat. Arizona water law does recognize such provisions; however, because this change is relatively recent, instream water rights have low priority and are often overcome by more senior diversion rights. Arizona State law also allows surface water depletion by groundwater pumping.

There are many Federal statutes that potentially afford protection to spikedace and loach minnow. A few of these are section 404 of the Clean Water Act (33 U.S.C. 1251

et seq.

), Federal Land Policy and Management Act (43 U.S.C. 1701-1782), National Forest Management Act (16 U.S.C. 1600

et seq.

), NEPA, and the Act. However, in practice these statutes have not been able to provide sufficient protection to prevent the downward trend in the populations and habitat of spikedace and loach minnow and the upward trend in threats. Section 404 of the Clean Water Act regulates placement of fill into waters of the United States, including most of spikedace and loach minnow habitat. However, many actions highly detrimental to spikedace and loach minnow and their habitats, such as gravel mining and irrigation diversion structure construction and maintenance, are often exempted from the Clean Water Act. Other detrimental actions, such as bank stabilization and road crossings, are covered under nationwide permits that receive little or no Service review. A lack of thorough, site-specific analyses for projects can allow substantial adverse effects to spikedace, loach minnow, and their habitat.

The Federal Land Policy and Management Act and National Forest Management Act provide mechanisms for protection and enhancement of spikedace, loach minnow, and their habitat on Federal lands; however, these laws have been in effect longer than the 24 years since spikedace and loach minnow were listed. Although the Forest Service has made significant progress on some stream enhancements (Fossil Creek, Blue River), the multiple-use mission and limited staffing and resources has limited measureable on-the-ground success, and the status of these species has continued to decline.

Spikedace and loach minnow are currently listed as threatened under the Act and therefore are afforded the protections of the Act. Special rules were promulgated for spikedace and loach minnow in 1986, which prohibit taking of the species, except under certain circumstances in accordance with applicable State fish and wildlife conservation laws and regulations. Violations of the special rules are considered violations of the Act (50 CFR 17.44(p) for spikedace and 50 CFR 17.44(q) for loach minnow). As a result of the special rules for spikedace and loach minnow, the AGFD is issuing scientific collecting permits. This authority was granted at 50 CFR 17.44(p) for spikedace and 50 CFR 17.44(q) for loach minnow. This is confirmed through Arizona Commission Order 40 and New Mexico special permit (19 New Mexico Administrative Code 33.6.2).

Under section 7 of the Act, Federal agencies must insure that any action they authorize, fund, or carry out is not likely to jeopardize the continued existence of any endangered or threatened species or result in the adverse modification or destruction of designated critical habitat. The Service promulgated regulations extending take prohibitions under section 9 for endangered species to threatened species. Prohibited actions under section 9 include, but are not limited to, take (i.e., harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or attempt to engage in such activity). Critical habitat designation alerts the public that the areas designated as critical habitat are important for the future recovery of the species, as well as invoking the review of these areas under section 7 of the Act with regard to any possible Federal actions in that area.

Section 10 of the Act allows for the permitting of take in the course of otherwise lawful activities by private entities, and may involve habitat conservation plans which can ultimately benefit spikedace or loach minnow. The habitat conservation plan prepared by Salt River Project is expected to benefit spikedace and loach minnow in the Verde River.

Summary of Factor D

In summary, prohibitions against taking the species have been in place for decades, but these prohibitions have limited ability to address the numerous habitat impacts, particularly water diversion and the distribution and abundance of nonnative fishes, affecting spikedace and loach minnow. Therefore, we find that the spikedace and loach minnow are threatened by the inadequacy of existing regulatory mechanisms.

E. Other Natural or Manmade Factors Affecting the Species' Continued Existence

Nonnative Fishes

As described under Factor C above, nonnative fishes pose a significant threat to Gila River basin native fishes, including spikedace and loach minnow (Minckley 1985, pp. 1, 68; Williams

et al.

1985, pp. 3, 17-20; Minckley and Deacon 1991, pp. 15-17). Competition with nonnative fish species is considered a primary threat to spikedace and loach minnow (predation by nonnative fish species is discussed under Factor C). The effects of nonnative fish species are often exacerbated by changes in flow regimes or declines in habitat conditions associated with water developments, as discussed above, and should be considered against the backdrop of historical habitat degradation that has occurred over time (Minckley and Meffe 1987, pp. 94, 103; Rinne 1991, p. 12). Stefferud and Rinne (1996b, p. 25) note that a long history of water development and diversion coupled with nonnative fish introductions has resulted in few streams in Arizona retaining their native fish communities. Using the Gila River as an example, Propst

et al.

(1988, p. 67) note that natural (e.g., drought) and human-induced (e.g., flow level reductions through irrigation diversion) factors combined to reduce loach minnow abundance in the Gila River. They note that where canyon habitat would normally continue to contain surface flows and suitable habitat for loach minnow, the establishment of nonnative fishes in canyon reaches has reduced their suitability as habitat for the minnow. Minckley and Douglas (1991, pp. 7-17) concluded that, for fishes native to the Southwest, the combination of changes in stream discharge patterns and nonnative fish

introductions have reduced the range and numbers of all native species of fish, and has led to extinction of some.

As with many fish in the West, spikedace and loach minnow lacked exposure to a wider range of species, so that they seem to lack the competitive abilities and predator defenses developed by fishes from regions where more species are present (Moyle 1986, pp. 28-31; Douglas

et al.

1994, pp. 9-10). As a result, the native western fish fauna is significantly impacted by interactions with nonnative species. The introduction of more aggressive and competitive nonnative fish has led to significant losses of spikedace and loach minnow (Douglas

et al.

1994, pp. 14-17).

The aquatic ecosystem of the central Gila River basin has relatively small streams with warm water and low gradients, and many of the native aquatic species are small. Therefore, the primary threat to native fishes comes from small, nonnative fish species (Deacon

et al.

1964, pp. 385, 388). Examples of this are the impacts of mosquitofish and red shiner, which may compete with, or predate upon, native fish in the Gila River basin (Meffe 1985, pp. 173, 177-185; Douglas

et al.

1994, pp. 1, 13-17).

Nonnative fishes known to occur within the historical range of spikedace and loach minnow in the Gila River basin include channel catfish, flathead catfish, red shiner, fathead minnow, green sunfish, largemouth bass, smallmouth bass, rainbow trout, western mosquitofish, carp, warmouth (

Lepomis gulosus

), bluegill, yellow bullhead, black bullhead, and goldfish (Miller 1961, pp. 373-394; Nico and Fuller 1999, pp. 16, 21-24; Clark 2001, p. 1; AGFD 2004, Bahm and Robinson 2009b, p. 3). Additionally, as discussed above, parasites introduced incidentally with nonnative species may jeopardize spikedace and loach minnow populations. For spikedace and loach minnow, every habitat that has not been renovated or protected by barriers has at least six nonnative fish species present, at varying levels of occupation. In addition, occupied habitats have also been invaded by nonnative crayfish (

Orconectes virilis

) (Taylor

et al.

1996, p. 31; Carter

et al.

2007, p. 4; Robinson and Crowder 2009, p. 3; Robinson

et al.

2009b, p. 4). Crayfish are known to eat eggs, especially those bound to the substrate (Dorn and Mittlebach 2004, p. 2135), as is the case for spikedace and loach minnow. Additionally, crayfish cause decreases in macroinvertebrates, amphibians, and fishes (Hanson

et al.

1990, p. 69; Lodge

et al.

2000, p. 11). Several of the nonnative species now in spikedace and loach minnow habitats arrived there since the species were listed, such as red shiner in Aravaipa Creek (Stefferud and Reinthal 2005, p. 51) and Asian tapeworm in the middle Gila River.

Interference competition occurs with species such as red shiner. Nonnative red shiners compete with spikedace for suitable habitats, as the two species occupy essentially the same habitat types. The red shiner has an inverse distribution pattern in Arizona to spikedace (Minckley 1973, p. 138). Where the two species occur together, there is evidence of displacement of spikedace to less suitable habitats than previously occupied (Marsh

et al.

1989, pp. 67, 107). As a result, if red shiners are present, suitable habitat for spikedace is reduced. In addition, the introduction of red shiner and the decline of spikedace have occurred simultaneously (Minckley and Deacon 1968, pp. 1427-1428; Douglas

et al.

1994, pp. 13, 16-17). The red shiner was introduced in the mainstem Colorado River in the 1950s, spreading upstream to south-central Arizona by 1963, and by the late 1970s eastward into New Mexico. Spikedace disappeared at the same time and in the same progressively upstream direction, likely as a result of interactions with red shiner and in response to impacts of various water developments (Minckley and Deacon 1968, pp. 1427-1428; Minckley and Deacon 1991, pp. 7, 15; Douglas

et al.

1994, pp. 13-17).

One study focused on potential impacts of red shiner on spikedace in three areas: (1) Portions of the Gila River and Aravaipa Creek having only spikedace; (2) a portion of the Verde River where spikedace and red shiner co-occurred for three decades; and (3) a portion of the Gila River where red shiner invaded areas and where spikedace have never been recorded. The study indicated that, for reaches where only spikedace were present, spikedace displayed a preference for slower currents and smaller particles in the substrate than were generally available throughout the Gila River and Aravaipa Creek systems. Where red shiner occur in the Verde River, the study showed that red shiner occupied waters that were generally slower with smaller particle sizes in the substrate than were, on average, available in the system. The study concludes that spikedace, where co-occurring with red shiner, move into currents swifter than those selected when in isolation, while red shiner occupy the slower habitat, whether alone or with spikedace (Douglas

et al.

1994, pp. 14-16). Red shiners are known to occur in the Verde River (Minckley 1993, p. 10; Jahrke 1999, pp. 2-7; Bahm and Robinson 2009b, pp. 3-5), Aravaipa Creek (P. Reinthal, University of Arizona, pers. comm. 2008; Reinthal 2009, pp. 1-2), Blue River (ASU 2004, multiple reports; ASU 2005, multiple reports), and Gila River (Minckley 1973, pp. 136-137; Marsh

et al.

1989, pp. 12-13; Propst

et al.

2009, pp. 14-18).

As with spikedace, exploitive competition also appears to occur between red shiner and loach minnow. Red shiners occur in all places known to be formerly occupied by loach minnow, and are absent or rare in places where loach minnow persists. Because of this, red shiner has often been implicated in the decline of loach minnow. Loach minnow habitat is markedly different than that of red shiner, so interaction between the two species is unlikely to cause shifts in habitat use by loach minnow (Marsh

et al.

1989, p. 39). Instead, studies indicate that red shiner move into voids left when native fishes such as loach minnow are extirpated due to habitat degradation in the area (Bestgen and Propst 1986, p. 209). Should habitat conditions improve and the habitat once again become suitable for loach minnow, the presence of red shiner may preclude occupancy of loach minnow, although the specific mechanism of this interaction is not fully understood.

Prior to 1960, the Glenwood-Pleasanton reach of the Gila River supported a native fish assemblage of eight different species. Post-1960, four of these species became uncommon, and ultimately three of them were extirpated. In studies completed between 1961 and 1980, it was determined that loach minnow was less common than it had been, while the diversity of the nonnative fish community had increased in comparison to the pre-1960 period. Following 1980, red shiner, fathead minnow, and channel catfish were all regularly collected. Drought and diversions for irrigation resulted in a decline in habitat quality, with canyon reaches retaining most habitat components for native species. However, establishment of nonnative fishes in the canyon reaches has reduced the utility of these areas for native species (Propst

et al.

1988, pp. 51-56).

Western mosquitofish were introduced outside of their native range to help control mosquitoes. Because of their aggressive and predatory behavior, mosquitofish may negatively affect populations of small fishes through predation and competition (Courtenay and Meffe 1989, pp. 320-324).

Introduced mosquitofish have been particularly destructive to native fish communities in the American West, where they have contributed to the elimination or decline of populations of federally endangered and threatened species, such as the Gila topminnow (

Poeciliopsis occidentalis occidentalis

) (Courtenay and Meffe 1989, pp. 323-324).

Pilger

et al.

(2010, p. 312) found that the generalist feeding strategy of small-bodied nonnative fishes could further affect native fishes through competition, particularly if there is a high degree of overlap in habitat use. In their study on the upper Gila River, they determined that the diets of nonnative, small-bodied fishes and all age groups of native fishes overlapped, so that the presence of both juvenile and adult nonnative species could pose a competitive threat to native fishes (Pilger

et al.

2010, p. 311).

Restoration efforts have led to limited success in removing large-bodied predators, but the small-bodied competitors present more of a challenge. In the desert Southwest, the habitat conditions are so limited that native fish reintroductions can occur only in those areas where the competition and predation of nonnative fishes can be physically precluded, such as above a fish barrier.

Drought

The southwestern United States is currently experiencing drought conditions (University of Nebraska-Lincoln 2010, p. 1). Drought conditions are reported as severe to extreme for the watersheds within the Verde River, San Pedro River, Bonita Creek, Eagle Creek, Blue River, and San Francisco River subbasins in Arizona (Arizona Department of Water Resources 2009, p. 1). Portions of New Mexico are also considered abnormally dry, but not in areas currently occupied by spikedace and loach minnow (University of Nebraska-Lincoln 2010, p. 1). While spikedace and loach minnow have survived many droughts in their evolutionary histories, the present status of these species and their habitats are so degraded that the effects of the drought are more difficult for the species to withstand. In some areas of spikedace and loach minnow habitat, drought results in lower streamflow, and consequently warmer water temperatures beyond the species' tolerance limits, and more crowded habitats with higher levels of predation and competition. In other areas, drought reduces flooding, that would normally rejuvenate habitat and tend to reduce populations of some nonnative species, which are less adapted to the large floods of southwestern streams (Minckley and Meffe 1987, pp. 94, 104; Stefferud and Rinne 1996a, p. 80). The conjunction of drought with ongoing habitat loss and alteration; increased predation, competition, and disease from nonnative species; the uncertainties associated with climate change; and the general loss of resiliency in highly altered aquatic ecosystems have had negative consequences for spikedace and loach minnow populations.

Genetics

Each remaining population of spikedace is genetically distinct. Genetic distinctiveness in the Verde River and Gila River fishes indicates that these populations have been historically isolated. The center of the spikedace's historical distribution is permanently altered, and the remaining populations are isolated and represent the fringes of the formerly occupied range. Isolation of these populations has important ramifications for the overall survival of the species. Loss of any population may be permanent, as there is little ability to repopulate isolated areas, due largely to habitat alterations in areas between remaining populations (Propst

et al.

1986, pp. 38, 86). No genetic exchange is possible between the remaining populations of spikedace without human assistance. In addition, because genetic variation is important to the species' fitness and adaptive capability, losses of genetic variation represent a threat to the species (Meffe and Carroll 1997, pp. 162-172).

Spikedace believed to remain in the upper Verde River are genetically different than those that were translocated to Fossil Creek; however, there is a minimal opportunity for the two populations to interbreed due to the length of the river between the two occupied areas. While the Verde River supports many of the habitat features for spikedace, it currently supports a high number of nonnative species that compete with, and prey on, spikedace. We anticipate that, until extensive management takes place, spikedace in the two areas will remain isolated. The spikedace translocation in Fossil Creek has been in place for approximately 2 years. It is not known if that translocation effort will succeed.

As with spikedace, each remaining population of loach minnow is genetically distinct. Genetic subdivision into three geographic regions indicates that gene flow has been low but not historically absent (Tibbets 1993, pp. 22-24, 33). The center of the loach minnow's historical distribution is permanently gone, and the remaining populations are isolated and represent the fringes of the formerly occupied range. Isolation of these populations has important ramifications for the overall survival of the species. Loss of any population may be permanent, as there is little ability to repopulate isolated areas, due largely to habitat alterations in areas between remaining populations (Propst

et al.

1988, p. 65). No genetic exchange is likely between the remaining populations of loach minnow without human assistance. In addition, because genetic variation is important to the species' fitness and adaptive change, losses of genetic variation represent a threat to the species' ability to adapt and persist, and further compromise their continued existence (Meffe and Carroll 1997, pp. 162-172).

Climate Conditions

Climate conditions have contributed to the status of the spikedace and loach minnow now and will likely continue into the foreseeable future. While floods may benefit the species, habitat drying affects the occurrence of natural events, such as fire, drought, and forest die-off, and increases the chances of disease and infection.

Climate simulations of Palmer Drought Severity Index (PSDI) (a calculation of the cumulative effects of precipitation and temperature on surface moisture balance) for the Southwest for the periods of 2006-2030 and 2035-2060 predict an increase in drought severity with surface warming. Additionally, drought still increases during wetter simulations because the effect of heat-related moisture loss (Hoerling and Eicheid 2007, p. 19). Annual mean precipitation is likely to decrease in the Southwest as well as the length of snow season and snow depth (IPCC 2007, p. 887). Most models project a widespread decrease in snow depth in the Rocky Mountains and earlier snowmelt (IPCC 2007, p. 891). Exactly how climate change will affect precipitation is less certain, because precipitation predictions are based on continental-scale general circulation models that do not yet account for land use and land cover change effects on climate or regional phenomena. Consistent with recent observations in changes from climate, the outlook presented for the Southwest predicts warmer, drier, drought-like conditions (Seager

et al.

2007, p. 1181; Hoerling and Eischeid 2007, p. 19). A decline in water resources with or without climate change will be a significant factor in the compromised watersheds of the desert southwest.

Summary of Factor E

The small and declining spikedace and loach minnow populations make these species susceptible to natural environmental variability, including climate conditions such as drought. The high level of nonnative fish species competing for food resources and spawning conditions will exacerbate the compromised conditions where spikedace and loach minnow can occur. These native fishes are unable to maintain a competitive edge in areas where resources are already limited, and these resources are likely to become more limited due to water developments and drought. The demands on water resources, decreases in precipitation, and increases in temperatures are likely to further limit the areas where spikedace or loach minnow can persist. Therefore, we find that the spikedace and loach minnow are threatened by other natural or manmade factors.

Available Conservation Measures

Conservation measures provided to spikedace and loach minnow under the Act include several reintroduction and augmentation projects. Some of these projects have already begun; others are in the planning stage. Project planning is underway for renovation efforts in Blue River and Spring Creek in Arizona. Other recovery actions include reintroduction or translocation of spikedace into streams within its historical range. In 2007, translocations included 210 spikedace into Hot Springs Canyon, 210 spikedace into Redfield Canyon, and 124 spikedace into Fossil Creek. Monitoring and augmentation with 500 additional spikedace each at Hot Springs and Redfield and 600 additional spikedace at Fossil Creek occurred at these sites in 2008. In 2008, 448 spikedace were reintroduced into Bonita Creek, Arizona. Spikedace were also reintroduced into the San Francisco River in New Mexico. Augmentation and monitoring will occur at these sites as well. Monitoring conducted at each of these sites will be used to determine if populations ultimately become self-sustaining at these new locations.

Several translocation projects for loach minnow are also in the planning stages. These projects may occur with or without construction of fish barriers. Loach minnow may also benefit from the Blue River and Spring Creek renovation projects mentioned above.

Additional recovery actions include translocations or reintroduction of loach minnow into streams within its historical range. In 2007, translocations included 205 loach minnow into Hot Springs Canyon, 205 loach minnow into Redfield Canyon, and 124 loach minnow into Fossil Creek. Monitoring and augmentation with 1,000 additional loach minnow each at Hot Springs and Redfield canyons and 2,004 additional loach minnow at Fossil Creek occurred in 2008. In 2008, 678 loach minnow were translocated into Bonita Creek, Arizona. Augmentation and monitoring will occur at this site as well. Monitoring conducted at each of these sites will be used to determine if populations ultimately become self-sustaining at these new locations.

The AGFD and Bureau of Reclamation continue to fund equipment and staff to run the Bubbling Ponds Native Fish Research Facility through the Gila River Basin Native Fishes Conservation Program (formerly known as the Central Arizona Project Fund Transfer Program). Salt River Project's habitat conservation plan was signed in 2008, and is expected to benefit both the spikedace and the loach minnow in the Verde River watershed. Also in 2008, AGFD staff managed original source stock and their progeny at the Bubbling Ponds facility, totaling 740 Gila River spikedace, 1,650 Aravaipa Creek spikedace, 670 Blue River loach minnow, and 3,250 Aravaipa Creek loach minnow. Plans are underway to bring in stock from every extant population of loach minnow, including those in the San Francisco River, the three forks of the Gila River, the upper Gila River in New Mexico, and Eagle and the Black River system in Arizona. Bubbling Ponds will serve as a refuge for some populations, and as a captive breeding facility for others, depending on the status of the population and availability of translocation sites.

Proposed Determination

As required by the Act, we considered the five factors in assessing whether the spikedace and loach minnow are endangered or threatened throughout all or a significant portion of their range. We carefully assessed the best scientific and commercial information available regarding reclassification of the spikedace and the loach minnow from threatened to endangered. We believe there are many threats to both species, including habitat loss and modifications (Factor A) caused by historical and ongoing land uses such as water diversion and pumping, livestock grazing, and road construction. However, competition with, or predation by, nonnative species, such as channel and flathead catfish, green sunfish, and red shiner, is likely the largest remaining threat to the species (Factors C and E). Existing regulatory mechanisms (Factor D) have not proven adequate to halt the decline of spikedace or loach minnow since the time of their listing as threatened species. In addition, the warmer, drier, drought-like conditions predicted to occur due to climate change (Factor E) will further reduce available resources for spikedace and loach minnow.

In 1991, we completed a 5-year review for spikedace and loach minnow in which we determined that the species' status was very precarious and that a change in status from threatened to endangered was warranted. Since that time, although some recovery actions have occurred, the majority of the areas historically occupied by spikedace and loach minnow have seen a shift from a predominance of native fishes to a predominance of nonnative fishes. The low numbers of spikedace and loach minnow, their isolation in tributary waters, drought, ongoing water demands, and other threats indicate that the species are now in danger of extinction throughout their ranges.

We determined in 1994 that reclassifying spikedace and loach minnow to endangered status was warranted but precluded (59 FR 35303, July 11, 1994), and restated this conclusion on January 8, 2001 (66 FR 1295). We reanalyzed the determination each year in our Candidate Notice of Review, and determined that reclassification to endangered is warranted, with the most recent Candidate Notice of Review published on November 9, 2009 (74 FR 57804). Based on this information, as well as the above review of the best scientific and commercial information available, we find that both species meet the definition of endangered species under the Act, and propose that spikedace and loach minnow be reclassified as endangered.

If we finalize the reclassification of spikedace and loach minnow to endangered status, we would remove the special rules for these species at 50 CFR 17.44(p) and 17.44(q), respectively. Special rules apply only to threatened species; therefore, if spikedace and loach minnow were listed as endangered, these special rules would no longer apply.

Critical Habitat

Background

Critical habitat is defined in section 3 of the Act as:

(i) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are

found those physical or biological features:

(I) Essential to the conservation of the species and

(II) Which may require special management considerations or protection; and

(ii) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided under the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the prohibition against Federal agencies carrying out, funding, or authorizing actions that are likely to result in the destruction or adverse modification of critical habitat. Section 7(a)(2) requires consultation on Federal actions that may affect critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures. Where a landowner seeks or requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal agency and the applicant is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

For inclusion in a critical habitat designation, the habitat within the geographical area occupied by the species at the time it was listed must contain the physical and biological features (PBFs) essential to the conservation of the species, and be included only if those features may require special management considerations or protection. Critical habitat designations identify, to the extent known using the best scientific and commercial data available, habitat areas that provide essential life cycle needs of the species (areas on which are found the PBFs laid out in the appropriate quantity and spatial arrangement for the conservation of the species). Under the Act and regulations at 50 CFR 424.12, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed only when we determine that those areas are essential for the conservation of the species and that designation limited to those areas occupied at the time of listing would be inadequate to ensure the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the

Federal Register

on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When determining which areas should be designated as critical habitat, our primary source of information is generally developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion or personal knowledge.

Habitat is often dynamic, and species may move from one area of a river system to another over time. Furthermore, we recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be required for recovery of the species.

Areas that are important to the conservation of the species, but are outside the critical habitat designation, will continue to be subject to conservation actions we implement under section 7(a)(1) of the Act. Areas that support populations are also subject to the regulatory protections afforded by the section 7(a)(2) jeopardy standard, as determined on the basis of the best available scientific information at the time of the agency action. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

Physical and Biological Features (PBFs)

In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and the regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied at the time of listing to propose as critical habitat, we consider the physical and biological features essential to the conservation of the species which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historic, geographical, and ecological distributions of a species.

We considered the specific PBFs essential to the conservation of the species and in the appropriate quantity and spatial arrangement for the conservation of the species. We derived the specific PBFs from the biological needs of spikedace and loach minnow.

Space for Individual and Population Growth and for Normal Behavior

Spikedace

Microhabitats.

Habitat occupied by spikedace can be broken down into smaller, specialized habitats called microhabitats. These microhabitats vary by stream, by season, and by species' life stage. Studies on habitat use have been completed on the Gila River in New Mexico, and the Verde River and Aravaipa Creek in Arizona. Generally, spikedace occupy moderate to large perennial streams at low elevations over substrates (river bottom material) of sand, gravel, and cobble (Barber and Minckley 1966, p. 31; Propst

et al.

1986, pp. 3, 12; Rinne and Kroeger 1988, p. 1). Occupied streams are typically of low gradient (Barber

et al.

1970, p. 10; Rinne and Kroeger 1988, p. 2; Rinne 1991, pp. 8-12; Rinne and Stefferud 1996, p. 17), and less than 1 meter (m) (3.28 feet (ft)) in depth (Propst

et al.

1986, p. 41; Minckley and Marsh 2009, p. 155).

Larval spikedace occur most frequently in slow-velocity water near stream margins or along pool edges. Most larvae are found over sand substrates. Juvenile spikedace tend to be found over a greater range of water velocities than larvae, but still in shallow areas. Juvenile spikedace occupy areas with a gravel or sand substrate, although some have been found over cobble substrates as well. Larvae and juveniles may occasionally be found in quiet pools or backwaters (

e.g.,

pools that are connected with, but out of, the main river channel) (Sublette

et al.

1990, p. 138).

Adult spikedace occur in the widest range of flow velocities. They are typically associated with shear zones (areas within a stream where more rapidly flowing water abuts water moving at slower velocities), downstream of sand bars, and in eddies or small whirlpools along downstream margins of riffles (those shallow portions of the stream with rougher, choppy water). Adult spikedace are found in shallow water over predominantly gravel-dominated substrates (Propst

et al.

1986, p. 40; Rinne 1991, pp. 8-12; Rinne and Stefferud 1997, p. 21; Rinne and Deacon 2000, p. 106; Rinne 2001, p. 68), but also over cobble and sand substrates (Minckley and Marsh 2009, p. 155; Rinne and Kroeger 1988, p. 3; Sublette

et al.

1990, p. 138).

In addition to substrate type, the amount of embeddedness (filling in of spaces by fine sediments) is also important to spikedace. Spikedace more commonly occur in areas with low to moderate amounts of fine sediment and substrate embeddedness, which is important for the healthy development of eggs. Spawning has been observed in areas with sand and gravel beds and not in areas where fine materials smaller than sand coats the sand or gravel substrate. Additionally, low to moderate fine sediments ensure that eggs remain well-oxygenated and will not suffocate due to sediment deposition (Propst

et al.

1986, p. 40).

Water temperatures of occupied spikedace habitat vary with time of year. Water temperatures have been collected at Aravaipa Creek, and on the Gila River in the Forks area and at the Cliff-Gila Valley. Summer water temperatures were between 19.3 degrees Celsius (°C) (66.7 degrees Fahrenheit (°F)) (Gila River, Forks Area) and 27 °C (80.6 °F) (Aravaipa Creek). Winter water temperatures ranged between 8.9 °C (48.0 °F) at Aravaipa Creek and 11.7 °C (53.1 °F) in the Cliff-Gila Valley (Barber and Minckley 1966, p. 316; Barber

et al.

1970, pp. 11, 14; Propst

et al.

1986, p. 57).

Recent studies by the University of Arizona focused on temperature tolerances of spikedace. In the study, fish were acclimated to a given temperature, and then temperatures were increased by 1 °C (1.8 °F) per day until test temperatures were reached. The study determined that no spikedace survived exposure of 30 days at 34 or 36 °C (93.2 or 96.8 °F), and that 50 percent mortality occurred after 30 days at 32.1 °C (89.8 °F). In addition, growth rate was slowed at 32 °C (89.6 °F), as well as at the lower test temperatures of 10 and 4 °C (50 and 39.2 °F). Multiple behavioral and physiological changes were observed, indicating the fish became stressed at 30, 32, and 33 °C (86, 89.6 and 91.4 °F) treatments. The study concludes that temperature tolerance in the wild may be lower due to the influence of additional stressors, including disease, predation, competition, or poor water quality. Survival of fish in the fluctuating temperature trials in the study likely indicates that exposure to higher temperatures for short periods during a day would be less stressful to spikedace. The study concludes that 100 percent survival of spikedace at 30 °C (86 °F) in the experiment suggests that little juvenile or adult mortality would occur due to thermal stress if peak water temperatures remain at or below that level (Bonar

et al.

2005, pp. 7-8, 29-30).

Spikedace occupy streams with low to moderate gradients (Propst

et al.

1986, p. 3; Rinne and Stefferud 1997, p. 14; Stefferud and Rinne 1996, p. 21; Sublette

et al.

1990, p. 138). Specific gradient data are generally lacking, but the gradient of occupied portions of Aravaipa Creek and the Verde River varied between approximately 0.3 to < 1.0 percent (Barber

et al.

1970, p. 10; Rinne and Kroeger 1988, p. 2; Rinne and Stefferud 1997, p. 14).

Table 1 compares specific parameters of habitat occupied by spikedace at various ages as identified through studies completed to date. Studies on flow velocity in occupied spikedace habitat have been completed on the Gila River, Aravaipa Creek, and the Verde River (Barber and Minckley 1966, p. 321; Minckley 1973, p. 114; Anderson 1978, p. 17; Schreiber 1978, p. 4; Turner and Tafanelli 1983, pp. 15-16; Propst

et al.

1986, pp. 39-41; Rinne and Kroeger 1988, p. 1; Hardy

et al.

1990, pp. 19-20, 39; Sublette

et al.

1990, p. 138; Rinne 1991, pp. 9-10; Rinne 1999, p. 6).

Table 1—Habitat Parameters for Varying Life Stages of Spikedace

Larvae

Juveniles

Adults

Flow Velocity in centimeters per second (inches per second)

8.4 (3.3)

16.8 (6.6)

23.3-70.0 (9.2-27.6).

Depth in centimeters (inches)

3.0-48.8 (1.2-19.2)

3.0-45.7 (1.2-18.0)

6.1-42.7 (2.4-16.8).

Gradient (percent)

No data

No data

0.3 to < 1.0.

Substrate

Primarily sand, with some over gravel or cobble

Primarily gravel, with some sand and cobble

Sand, gravel, cobble, and low amounts of fine sediments.

In studies on the Gila River, there were seasonal shifts in microhabitats used, involving depth or velocity, depending on the study site. It is believed that seasonal shifts in microhabitat use reflect selection by spikedace for particular microhabitats. In the cold season, when their metabolic rate decreases, spikedace near the Forks

area on the Gila River seek protected areas among the cobble of stream channel margins, where water is shallower and warmer. In other areas such as the Cliff-Gila Valley, cobbled banks for protection were generally not available, but slow-velocity areas in the lee of gravel bars and riffles were common, and spikedace shifted to these protected areas of slower velocity during the cold season. Seasonal changes in microhabitat preference by spikedace are not entirely understood, and additional study is needed (Propst

et al.

1986, pp. 47-49).

Studies indicate a geographic variation in the portion of the stream used by spikedace. On the Verde River, outside of the April to June breeding season, 80 percent of the spikedace collected used run and glide habitat. For this study, a glide was defined as a portion of the stream with a lower gradient (0.3 percent), versus a run which had a slightly steeper gradient (0.3-0.5 percent) (Rinne and Stefferud 1996, p. 14). In contrast, spikedace in the Gila River were most commonly found in riffle areas of the stream with moderate to swift currents (Anderson 1978, p. 17) and some run habitats (J.M. Montgomery 1985, p. 21), as were spikedace in Aravaipa Creek (Barber and Minckley 1966, p. 321).

Flooding.

In part, suitable habitat conditions are maintained by flooding. Periodic flooding appears to benefit spikedace in three ways: (1) Removing excess sediment from some portions of the stream; (2) removing nonnative fish species from a given area; and (3) increasing prey species diversity. Items 2 and 3 will be addressed in greater detail below.

Flooding in Aravaipa Creek has resulted in the transport of heavier loads of sediments, such as cobble, gravel, and sand, that are deposited where the stream widens, gradient flattens, and velocity and turbulence decreases. Dams formed by such deposition can temporarily cause water to back up and break into braids downstream of the dam. The braided areas provide excellent nurseries for larval and juvenile fishes (Velasco 1997, pp. 28-29).

On the Gila River in New Mexico, flows fluctuate seasonally with snowmelt, causing spring pulses and occasional floods, and late-summer or monsoonal rains produce floods of varying intensity and duration. These high flows likely rejuvenate spikedace spawning and foraging habitat (Propst

et al.

1986, p. 3). Floods likely benefit native fish by breaking up embedded bottom materials (Mueller 1984, p. 355). A study of the Verde River analyzed the effects of flooding in 1993 and 1995, finding that the floods either stimulated spawning, enhanced recruitment of three native species, or eliminated one of the nonnative fish species (Stefferud and Rinne 1996a, p. 80).

In summary, based on the best scientific and commercial information available for spikedace, we have developed the following ranges in habitat parameters, as follows:

• Shallow water generally less than 1 m (3.3 ft) in depth;

• Slow to swift flow velocities between 5 and 80 cm per second (sec) (1.9 and 31.5 in. per sec);

• Glides, runs, riffles, the margins of pools and eddies, and backwater components;

• Sand, gravel, and cobble substrates with low or moderate amounts of fine sediment and substrate embeddedness, as maintained by a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments;

• Low gradients of less than approximately one percent;

• Water temperatures in the general range of 8 to 28 °C (46.4 to 82.4 °F); and

• Elevations below 2,100 m (6,890 ft).

Loach Minnow

Microhabitat.

The best scientific and commercial information available indicates that, in general, loach minnow live on the bottom of small to large streams or rivers with low gradients within shallow, swift, and turbulent riffles. They are also known to occupy pool, riffle, and run habitats in some areas. They live and feed among clean, loose, gravel-to-cobble substrates. Their reduced air bladder (the organ that aids in controlling a fish's ability to float without actively swimming) allows them to persist in high-velocity habitats with a minimal amount of energy, and they live in the interstitial spaces (openings) between rocks (Anderson and Turner 1977, pp. 2, 6-7, 9, 12-13; Barber and Minckley 1966, p. 315; Lee

et al.

1980, p. 365; Britt 1982, pp. 10-13, 29-30; J.M. Montgomery 1985, p. 21; Marsh

et al.

2003, p. 666; Minckley 1981, p. 165; Propst

et al.

1988, p. 35; Rinne 1989, p. 109; Velasco 1997, p. 28; Sublette

et al.

1990, p. 187; AGFD 1994, pp. 1, 5-11; Bagley

et al.

1995, pp. 11, 13, 16, 17, 22; Rinne 2001, p. 69; Minckley and Marsh 2009, p. 174). Loach minnow are sometimes found in or near filamentous (threadlike) algae, which are attached to the stream substrates (Anderson and Turner 1977, p. 5; Lee

et al.

1980, p. 365; Minckley 1981, p. 165; Sublette

et al.

1990, p. 187; Marsh and Minckley 2009, p. 174).

Microhabitats used by loach minnow vary by life stage and stream. Adult loach minnow occupy a broad range of water velocities, with the majority of adults occurring in swift flows. Their eggs are adhesive, and are placed on the undersurfaces of rocks in the same riffles that they themselves occupy. After hatching, larval loach minnow move from the rocks under which they were spawned to areas with slower velocities than the main stream, typically remaining in areas with significantly slower velocities than juveniles and adults. Larval loach minnow occupy areas that are shallower and significantly slower than areas where eggs are found (Propst

et al.

1988, p. 37; Propst and Bestgen 1991, p. 32). Juvenile loach minnow generally occur in areas where velocities are similar to those used by adults, and that have higher flow velocities than those occupied by larvae (Propst

et al.

1988, pp. 36-37).

Substrate is an important component of loach minnow habitat. Studies in Aravaipa Creek and the Gila River indicate that loach minnow prefer cobble and large gravel, avoiding areas dominated by sand or fine gravel. This may be because loach minnow maintain a relatively stationary position on the bottom of a stream in flowing water. An irregular bottom, such as that created by cobble or larger gravels, creates pockets of lower water velocities around larger rocks where loach minnow can remain stationary with less energy expenditure (Turner and Tafanelli 1983, pp. 24-25). In the Gila and San Francisco rivers, the majority of loach minnow captured occurred in the upstream portion of a riffle, rather than in the central and lower sections of the riffle, where loose materials are more likely to fall out of the water column and settle on the stream bottom. This is likely due to the availability of interstitial spaces in the cobble-rubble substrate, which became filled with sediment more quickly in the central and lower sections of a riffle (Propst

et al.

1984, p. 12).

Varying substrates are used during different life stages of loach minnow. Adults occur over cobble and gravel, and place their eggs in these areas. Larval loach minnow are found where substrate particles are smaller than those used by adults. Juvenile loach minnow occupy areas with substrates of larger particle size than larvae. Generally, adults exhibited a narrower preference for depth and substrate than did juveniles, and were associated with gravel to cobble substrates within a narrower range of depths (Propst

et al.

1988, pp. 36-39; Propst and Bestgen 1991, pp. 32-33).

Loach minnow have a fairly narrow range in temperature tolerance, and their upstream distributional limits in some areas may be linked to low winter stream temperature (Propst

et al.

1988, p. 62). Suitable temperature regimes appear to be fairly consistent across geographic areas. Studies of Aravaipa Creek, East Fork White River, the San Francisco River, and the Gila River determined that loach minnow were present in areas with water temperatures in the range of 9 to 22 °C (48.2 to 71.6 °F) (Britt 1982, p. 31; Propst

et al.

1988, p. 62; Leon 1989, p. 1; Propst and Bestgen 1991, p. 33; Vives and Minckley 1990, p. 451).

Recent studies by the University of Arizona focused on temperature tolerances of loach minnow. In one study, fish were acclimated to a given temperature, and then temperatures were increased by 1 °C (1.8 °F) per day until test temperatures were reached. The study determined that no loach minnow survived for 30 days at 32 °C (89.6 °F), and that 50 percent mortality occurred after 30 days at 30.6 °C (87.1 °F). In addition, growth rate slowed at 28 and 30 °C (82.4 and 86.0 °F) compared to growth at 25 °C (77 °F), indicating that loach minnow were stressed at sublethal temperatures. Survival of fish in the fluctuating temperature trials of the study likely indicates that exposure to higher temperatures for short periods during a day would be less stressful to loach minnow. The study concludes that temperature tolerance in the wild may be lower due to the influence of additional stressors, including disease, predation, competition, or poor water quality. The study concludes that since 100 percent survival of loach minnow at 28 °C (82.4 °F) was observed, that little juvenile or adult mortality would occur due to thermal stress if peak water temperatures remain at or below that level (Bonar

et al.

2005, pp. 6-8, 28, 33).

Gradient may influence the distribution and abundance of loach minnow. In studies of the San Francisco River, Gila River, Aravaipa Creek, and the Blue River, loach minnow occurred in stream reaches where the gradient was generally low, ranging from 0.3 to 2.2 percent (Rinne 1989, p. 109; Rinne 2001, p. 69).

Table 2 compares specific parameters of microhabitats occupied by loach minnow at various ages as identified through studies completed to date. Studies on habitat occupied by loach minnow have been completed on the Gila River, Tularosa River, San Francisco River, Aravaipa Creek, Deer Creek, and Eagle Creek (Barber and Minckley 1966, p. 321; Britt 1982, pp. 1, 5, 10-12, 29; Turner and Tafanelli 1983, pp. 15-20, 26; Propst

et al.

1984, pp. 7-12; Propst

et al.

1988, pp. 32, 36-39; Rinne 1989, pp. 111-113, 116; Propst and Bestgen 1991, p. 32; Vives and Minckley 1990, pp. 451-452; Propst and Bestgen 1991, pp. 32-33; Velasco 1997, pp. 5-6; Marsh

et al.

2003, p. 666).

Table 2—Habitat Parameters for Varying Life Stages of Loach Minnow

Egg

Larvae

Juveniles

Adults

Flow Velocity in centimeters per second (inches per second)

3.0-91.4 (1.2-36.0)

0.0-48.8 (0.0-19.2)

3.0-85.3 (1.2-33.6)

0.0-79.2 (0.0-31.2).

Depth in centimeters (inches)

3.0-30.5 (1.2-12)

3.0-45.7 (1.2- 8.0)

6.1-42.7 (2.4-16.8)

6.1-45.7 (2.4-18.0).

Substrate

Large gravel to rubble

No data

No data

Gravel to cobble.

There are some differences in microhabitats occupied by loach minnow in different areas. Studies completed in New Mexico determined that there were significant differences in water velocities occupied among the three study sites, with the mean velocities at 37.4 (Tularosa River), 56.3 (Forks area of the Gila River) and 60.5 cm per second (Cliff-Gila Valley site on the Gila River). Differences in water depth were not as pronounced, however. Much of the variation in microhabitat utilization may be explained by habitat availability, as the compared streams varied in size (Propst

et al.

1988, pp. 37-43).

Flooding.

Flooding also plays an important role in habitat suitability for loach minnow. In areas where substantial diversions (structures created to divert water to pools for pumping from the stream) or impoundments have been constructed, loach minnow are less likely to occur (Propst

et al.

1988, pp. 63-64; Propst and Bestgen 1991, p. 37). This is in part due to habitat changes caused by the construction of the diversions, and in part due to the reduction of beneficial effects of flooding on loach minnow habitat. Flooding appears to positively affect loach minnow population dynamics by resulting in higher recruitment (reproduction and survival of young) and by decreasing the abundance of nonnative fishes (addressed further below) (Stefferud and Rinne 1996b, p. 1).

Flooding also cleans, rearranges, and rehabilitates important riffle habitat (Propst

et al.

1988, pp. 63-64). Flooding allows for the scouring of sand and gravel in riffle areas, which reduces the degree of embeddedness of cobble and boulder substrates (Britt 1982, p. 45). Typically, sediment is carried along the bed of a stream and deposited at the downstream, undersurface side of cobbles and boulders. Over time, this can result in the filling of cavities created under cobbles and boulders (Rinne 2001, p. 69). Flooding removes the extra sediment, and cavities created under cobbles by scouring action of the flood waters provides enhanced spawning habitat for loach minnow.

Studies on the Gila, Tularosa, and San Francisco rivers found that flooding is primarily a positive influence on native fish, and apparently had a positive influence on the relative abundance of loach minnow (Britt 1982, p. 45). Rather than following a typical pattern of winter mortality and population decline, high levels of loach minnow recruitment occurred after the flood, and loach minnow relative abundance remained high through the next spring. Flooding enhanced and enlarged loach minnow habitat, resulting in a greater survivorship of individuals through winter and spring (Propst

et al.

1988, p. 51). Similar results were observed on the Gila and San Francisco rivers following flooding in 1978 (Britt 1982, p. 45).

In summary, based on the best scientific and commercial information available for loach minnow, we have developed generalized ranges in habitat parameters within streams or rivers, as follows:

• Shallow water generally less than 1 m (3.3 ft) in depth;

• Slow to swift flow velocities between 0 and 80 cm per sec (0.0 and 31.5 in. per sec);

• Pools, runs, riffles and rapids;

• Sand, gravel, cobble, and rubble substrates with low or moderate amounts of fine sediment and substrate embeddedness, as maintained by a

natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, flow regime that allow for adequate river functions, such as flows capable of transporting sediments;

• Water temperatures in the general range of 8 to 25 °C (46.4 to 77 °F);

• Low stream gradients of less than approximately 2.5 percent; and

• Elevations below 2,500 m (8,202 ft).

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Spikedace

Food.

Spikedace are active, highly mobile fish that visually inspect drifting materials both at the surface and within the water column. Gustatory inspection, or taking the potential prey items into the mouth before either swallowing or rejecting it, is also common (Barber and Minckley 1983, p. 37). Prey body size is small, typically ranging from 2 to 5 mm (0.08 to 0.20 in) long (Anderson 1978, p. 36).

Stomach content analysis of spikedace determined that mayflies, caddisflies, true flies (Order Diptera), stoneflies, and dragonflies (Order Odonata) are all potential prey items. In one Gila River study, the frequency of occurrence was 71 percent for mayflies, 34 percent for true flies, and 25 percent for caddisflies (Propst

et al.

1986, p. 59). A second Gila River study of four samples determined that total food volume was composed of 72.7 percent mayflies, 17.6 percent caddisflies, and 4.5 percent true flies (Anderson 1978, pp. 31-32). At Aravaipa Creek, mayflies, caddisflies, true flies, stoneflies, and dragonflies were all prey items for spikedace, as were some winged insects and plant materials (Schreiber 1978, pp. 12-16, 29, 35-37). Barber and Minckley (1983, pp. 34-38) found that spikedace at Aravaipa Creek also consumed ants and wasps (Order Hymenoptera), spiders (Order Areneae), beetles (Order Coleoptera), true bugs, and water fleas (Order Cladocera).

Spikedace diet varies seasonally (Barber and Minckley 1983, pp. 34-38). Mayflies dominated stomach contents in July, but declined in August and September, increasing in importance again between October and June. When mayflies were available in lower numbers, spikedace consumed a greater variety of foods, including true bugs, true flies, beetles, and spiders.

Spikedace diet varies with age class as well. Young spikedace fed on a diversity of small-bodied invertebrates occurring in and on sediments along the margins of the creek. True flies were found most frequently, but water fleas and aerial adults of aquatic and terrestrial insects also provide significant parts of the diet. As juveniles grow and migrate into the swifter currents of the channel, mayfly nymphs (invertebrates between the larval and adult life stages, similar to juveniles) and adults increase in importance (Barber and Minckley 1983, pp. 36-37).

Spikedace are dependent on aquatic insects for sustenance, and the production of the aquatic insects consumed by spikedace occurs mainly in riffle habitats (Propst

et al.

1986, p. 59). Barber and Minckley (1983, pp. 36-37, 40) found that spikedace in pools had eaten the least diverse food, while those from riffles contained a greater variety of taxa, indicating that the presence of riffles in good condition and abundance help to ensure that a sufficient number and variety of prey items will continue to be available for spikedace.

Aquatic invertebrates that constitute the bulk of the spikedace diet have specific habitat parameters of their own. Mayflies occur primarily in fresh water with an abundance of oxygen. Spikedace consume mayflies from the genus

Baetidae

(Schreiber 1978, p. 36), which are free-ranging species of rapid waters that maintain themselves in currents by clinging to pebbles. Spikedace also consumed individuals from two other mayfly genera (

Heptageniidae

and

Ephemerellidae

), which are considered “clinging species,” as they cling tightly to stones and other objects and may be found in greatest abundance in crevices and on the undersides of stones (Pennak 1978, p. 539). The importance of gravel and cobble substrates is illustrated by the fact that the availability of these prey species, which make up the bulk of the spikedace diet, requires these surfaces to persist.

The availability of food for spikedace is affected by flooding. The onset of flooding corresponds with an increased diversity of food items, as inflowing flood water carries terrestrial invertebrates, such as ants, bees, and wasps, into aquatic areas (Barber and Minckley 1983, p. 39).

Water.

As a purely aquatic species, spikedace are entirely dependent on streamflow habitat for all stages of their life cycle. Therefore, perennial flows are an essential feature. Areas with intermittent flows may serve as connective corridors between occupied or seasonally occupied habitat through which the species may move when the habitat is wetted.

In addition to water quantity, water quality is important to spikedace. Water with no or low levels of pollutants is essential for the survival of spikedace. For spikedace, pollutants such as copper, arsenic, mercury, cadmium, human and animal waste products, pesticides, suspended sediments, ash, and gasoline or diesel fuels should not be present at high levels (D. Baker, Service, pers. comm. 2005). In addition, for freshwater fish, dissolved oxygen should generally be greater than 3.5 cubic centimeters per liter (cc per l) (Bond 1979, p. 215). Below this, some stress to fish may occur.

Fish kills have been documented within the range of the spikedace, including on the San Francisco River (Rathbun 1969, pp. 1-2) and the San Pedro River (Eberhardt 1981, pp. 1-4, 6-9, 11-12, 14, 16, and Tables 2-8). Occupancy by spikedace at the San Francisco River site is less certain, but spikedace were present in the Gila River upstream of its confluence with the San Francisco. Spikedace were present in the San Pedro River up through 1969 within the area affected by the Cananea Mine spill, which extended 97 km (60 mi) north of the United States/Mexico border (Eberhardt 1981, p. 3). All aquatic life within this 97-km (60-mi) stretch was killed between 1977 and 1979, and no spikedace records are known after that time. For both the San Francisco and San Pedro rivers, leaching ponds associated with copper mines released waters into the streams, resulting in elevated levels of toxic chemicals. For the San Pedro River, this included elevated levels of iron, copper, manganese, and zinc. Both incidents resulted in die-offs of species inhabiting the streams. Eberhardt (1981, pp. 1, 3, 9, 10, 14-15) noted that no bottom-dwelling aquatic insects, live fish, or aquatic vegetation of any kind were found in the area affected by the spill. Rathbun (1969, pp. 1-2) reported similar results for the San Francisco River. As detailed above under the threats discussion, spills or discharges have occurred in the Gila River and affected streams within the watersheds of spikedace, including the Gila River, San Francisco River, San Pedro River, and some of their tributaries (Environmental Protection Agency 1997, pp. 24-67; Arizona Department of Environmental Quality 2000, p. 6; Church

et al.

2005, p. 40; Arizona Department of Environmental Quality 2007, p. 1).

Based on the information above, we identify an appropriate prey base and water quality to be a PBF for spikedace, as follows:

• An abundant aquatic insect food base consisting of mayflies, true flies,

black flies, caddisflies, stoneflies, and dragonflies;

• Streams with no or no more than low levels of pollutants;

• Perennial flows, or interrupted stream courses that are periodically dewatered but that serve as connective corridors between occupied or seasonally occupied habitat and through which the species may move when the habitat is wetted;

• Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Loach Minnow

Food.

Loach minnow are opportunistic, feeding on riffle-dwelling larval mayflies, black flies, and true flies, as well as from larvae of other aquatic insect groups such as caddisflies and stoneflies. Loach minnow in the Gila, Tularosa, and San Francisco rivers consumed primarily true flies and mayflies, with mayfly nymphs being an important food item throughout the year. Mayfly nymphs constituted the most important food item throughout the year for adults studied on the Gila and San Francisco Rivers, while larvae of true flies (insects of the order Diptera) were most common in the winter months (Propst

et al.

1988, p. 27; Propst and Bestgen 1991, p. 35). In Aravaipa Creek, loach minnow consumed 11 different prey items, including mayflies, stoneflies, caddisflies, and true flies. Mayflies constituted the largest percentage of their diet during this study except in January, when true flies made up 54.3 percent of the total food volume (Schreiber 1978, pp. 40-41).

Loach minnow consume different prey items during their various life stages. Both larvae and juveniles primarily consumed true flies, which constituted approximately 7 percent of their food items in one year, and 49 percent the following year in one study. Mayfly nymphs were also an important dietary element at 14 percent and 31 percent during a one-year study. Few other aquatic macroinvertebrates were consumed (Propst

et al.

1988, p. 27). In a second study, true fly larvae and mayfly nymphs constituted the primary food of larval and juvenile loach minnow (Propst and Bestgen 1991, p. 35).

The availability of pool and run habitats affects availability of prey species. While most of the food items of loach minnow are riffle species, two are not, including true fly larvae and mayfly nymphs. Mayfly nymphs, at times, made up 17 percent of the total food volume of loach minnow in a study at Aravaipa Creek (Schreiber 1978, pp. 40-41). The presence of a variety of habitat types is, therefore, important to the persistence of loach minnow in a stream, even though they are typically associated with riffles.

Water Quality.

Water, with no or low pollutant levels, is important for the conservation of loach minnow. For loach minnow, waters should have no more than low levels of pollutants, such as copper, arsenic, mercury, cadmium, human and animal waste products, pesticides, suspended sediments, and gasoline or diesel fuels (D. Baker, Service, pers. comm. 2005). In addition, for freshwater fish, dissolved oxygen should generally be greater than 3.5 cc per l (Bond 1979, p. 215). Below this, some stress to the fish may occur.

Fish kills associated with previous mining accidents, as well as other contaminants issues, are detailed under the spikedace discussion above. These incidents occurred within the historical range of the loach minnow. As with spikedace, loach minnow were known to occur in the area affected by the Cananea Mine spill up through 1961. All aquatic life within the affected area was killed between 1977 and 1979, and no loach minnow records are known after that time. On the San Francisco River, loach minnow are known to have occurred in the general area of the spill in the 1980s and 1990s (ASU 2002). Additional spills or discharges have occurred in the Gila River and affected streams within the watersheds occupied by loach minnow, including the Gila River, San Francisco River, San Pedro River, and some of their tributaries (Environmental Protection Agency 1997, pp. 24-67; Arizona Department of Environmental Quality 2000, p. 6; Church

et al.

2005, p. 40; Arizona Department of Environmental Quality 2007, p. 1).

Based on the information above, we identify an appropriate prey base and water quality to be a PBF for the loach minnow, as follows:

• An abundant aquatic insect food base consisting of mayflies, true flies, black flies, caddisflies, stoneflies, and dragonflies;

• Streams with no or no more than low levels of pollutants;

• Perennial flows, or interrupted stream courses that are periodically dewatered but that serve as connective corridors between occupied or seasonally occupied habitat and through which the species may move when the habitat is wetted; and

• Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Cover or Shelter

Spikedace.

No specific information on habitat parameters used specifically for cover and shelter is available for spikedace. Therefore, we have not identified any specific physical and biological features specific to cover and shelter for spikedace.

Loach Minnow.

As noted above, adult loach minnow are sometimes associated with filamentous algae, which may serve as a protective cover (Anderson and Turner 1977, p. 5; Lee

et al.

1980, p. 365; Minckley 1981, p. 165; Sublette

et al.

1990, p. 187; Marsh and Minckley 2009, p. 174).

Loach minnow adults place their adhesive eggs on the undersides of rocks, with the rock serving as protective cover. Probst

et al.

(1988, p. 21) found that the rocks used were typically elevated from the surface of the streambed on the downstream side, with most rocks flattened and smooth-surfaced. Adult loach minnow remain with the eggs, so that the rock serves as a protective cover for them as well (Propst

et al.

1988, pp. 21-25, 36-39).

Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

Spikedace

Suitable sites.

Spikedace occur in specific habitat during the breeding season, with female and male spikedace becoming segregated. Females occupy pools and eddies, while males occupy riffles flowing over sand and gravel beds in water approximately 7.9 to 15.0 cm (3.1 to 5.9 in) deep. Females then enter the riffles occupied by the males before eggs are released into the water column (Barber

et al.

1970, pp. 11-12).

Spikedace eggs are adhesive and develop among the gravel and cobble of the riffles following spawning. Spawning in riffle habitat ensures that the eggs are well oxygenated and are not normally subject to suffocation by sediment deposition due to the swifter flows found in riffle habitats. However, after the eggs have adhered to the gravel and cobble substrate, excessive sedimentation could cause suffocation of the eggs (Propst

et al.

1986, p. 40).

Larval and juvenile spikedace occupy peripheral portions of streams that have slower currents (Anderson 1978, p. 17; Propst

et al.

1986, pp. 40-41). Gila River studies found larval spikedace in velocities of 8.4 cm per second (3.3 in. per sec) while juvenile spikedace occupy areas with velocities of approximately 16.8 cm per second (6.6 in. per sec) (Propst

et al.

1986, p. 41).

Once they emerge from the gravel of the spawning riffles, spikedace larvae disperse to stream margins where water velocity is very slow or still. Larger larval and juvenile spikedace (those fish 25.4 to 35.6 mm (1.0 to 1.4 in) in length) occurred over a greater range of water velocities than smaller larvae, but still occupied water depths of less than 32.0 cm (12.6 in) (Propst

et al.

1986, p. 40). Juveniles and larvae are also occasionally found in quiet pools or backwaters (e.g., pools that are connected with, but out of, the main river channel) lacking streamflow (Sublette

et al.

1990, p. 138).

During a study on the Gila River, 60 percent of spikedace larvae were found over sand-dominated substrates, while 18 percent were found over gravel, and an additional 18 percent found over cobble-dominated substrates. While 45 percent of juvenile spikedace were found over sand substrates, an additional 45 percent of the juveniles were found over gravel substrates, with the remaining 10 percent associated with cobble-dominated substrates. Juveniles occupy a wider range in flow velocities than larvae (0.0 to 57.9 cm per second (22.8 in. per second)), but occurred at similar depths as larvae (Propst

et al.

1986, pp. 40-41).

As noted above, excessive sedimentation can lead to suffocation of eggs. Clean substrates are therefore essential for successful breeding. Both flooding and unaltered flow regimes are essential for maintenance of suitable substrates. As noted above under habitat requirements, periodic flooding appears to benefit spikedace by removing excess sediment from some portions of the stream, breaking up embedded bottom materials, or rearranging sediments in ways that restore suitable habitats. Flooding may also stimulate spawning or enhance recruitment (Mueller 1984, p. 355; Propst

et al.

1986, p. 3; Stefferud and Rinne 1996a, p. 80; Minckley and Meffe 1987, pp. 99, 100; Rinne and Stefferud 1997, pp. 159, 162; Velasco 1997, pp. 28-29).

Streams in the southwestern United States have a wide fluctuation in flows and some are periodically dewatered. While portions of stream segments included in this proposed designation may experience dry periods, they are still considered important because the spikedace is adapted to stream systems with fluctuating water levels. While they cannot persist in dewatered areas, spikedace will use these areas as connective corridors between occupied or seasonally occupied habitat when they are wetted. Areas that serve as connective corridors are those ephemeral or intermittent stream segments that connect two or more other perennial stream segments.

Therefore, based on the information above, we identify the following to be PBFs for spikedace:

• Sand, gravel, and cobble substrates;

• Riffle habitat;

• Slower currents along stream margins with appropriate stream velocities for larvae;

• Appropriate water depths for larvae and juvenile spikedace;

• Flow velocities that encompass the range of 8.5 cm per sec (3.3 in. per sec) to 57.9 cm per sec (22.8 in. per sec); and

• Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Loach Minnow

Adult loach minnow attach eggs to the undersurfaces of rocks in the same riffles in which they are typically found. In studies conducted on the Gila River, water velocities in these areas ranged from 3.0 to 91.4 cm per second (36.0 in. per second). The majority of rocks with attached eggs were found in water flowing at approximately 42.7 cm per second (16.8 in. per second). The range of depths in which rocks with eggs attached were found was 3.0 to 30.5 cm (1.2 to 12 in), with the majority found between 6.1 and 21.3 cm (2.4 and 8.4 in) (Propst

et al.

1988, pp. 36-39).

Loach minnow larvae occupy shallower and slower water than eggs. In Gila River studies, larvae occurred in flow velocities averaging 7.9 cm per second (3.1 in. per second), and in depths between 3.0 to 45.7 cm (1.2 to 18 in). Juveniles occurred in areas with higher velocities, ranging between 35.1 and 85.3 cm per second (13.8 and 33.6 in. per second). Juveniles occurred in slightly deeper water of approximately 6.1 to 42.7 cm (2.4 to 16.8 in) (Propst

et al.

1988, pp. 36-39).

As noted above under general habitat requirements, flooding is important in maintaining loach minnow habitat, including habitats used for breeding. Flooding reduces embeddedness of cobble and boulder substrates under which eggs are placed (Britt 1982, p. 45).

The construction of water diversions have reduced or eliminated riffle habitat in many stream reaches, resulting in pool development. Loach minnow are generally absent in stream reaches affected by impoundments. While the specific factors responsible for this are not known, it is likely related to modification of thermal regimes, habitat, food base, or discharge patterns (Propst

et al.

1988, p. 64; Minckley 1973, pp. 1-11).

Therefore, based on the information above, we identify the following to be PBFs for loach minnow:

• Cobble substrates;

• Riffle habitats;

• Slower currents along stream margins with appropriate stream velocities for larvae;

• Appropriate water depths for larvae and juvenile loach minnow;

• Flow velocities that encompass the range of 6.1 to 42.7 cm (2.4 to 16.8 in); and

• Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Habitats Protected From Disturbance or Representative of the Historical, Geographical, and Ecological Distributions of the Species

Spikedace

Nonnative aquatic species.

One of the primary reasons for the decline of native species is the presence of nonnative fishes, as described above under Factors C and E above. Interactions with nonnative fishes can occur in the form of interference competition (e.g., predation) or exploitive competition (competition for resources), and introduced species are considered a primary factor in the decline of native species (Anderson 1978, pp. 50-51; Miller

et al.

1989, p. 1; Lassuy 1995, p. 392). Multiple nonnative fish species are now present in the range of spikedace and loach minnow. In addition, nonnative parasites are also present.

Flooding may help to reduce the threat presented by nonnative species. Minckley and Meffe (1987, pp. 99-100) found that flooding, as part of a natural flow regime, may temporarily remove nonnative fish species, which are not adapted to flooding patterns in the Southwest. Thus flooding consequently removes the competitive pressures of nonnative fish species on native fish species which persist following the flood. Minckley and Meffe (1987, pp. 99-100) studied the differential response of native and nonnative fishes in seven unregulated and three regulated streams or stream reaches that were sampled before and after major flooding and noted that fish faunas of canyon-bound reaches of unregulated streams invariably shifted from a mixture of native and nonnative fish species to predominantly, and in some cases exclusively, native fishes after

large floods. Samples from regulated systems indicated relatively few or no changes in species composition due to releases from upstream dams at low, controlled volumes. However, during emergency releases, effects to nonnative fish species were similar to those seen with flooding on unregulated systems. There is some variability in fish response to flooding. Some nonnative species, such as smallmouth bass and green sunfish, appear to be partially adapted to flooding, and often reappear in a few weeks (Minckley and Meffe 1987, p. 100).

The information presented above indicates the detrimental effects of interference and exploitive competition with nonnative species to spikedace, as well as the issues presented by the introduction of nonnative parasites. Therefore, based on this information, we identify the necessary PBFs for spikedace to be:

• Habitat devoid of nonnative aquatic species, or habitat in which nonnative aquatic species are at levels that allow persistence of spikedace.

Loach Minnow

As with spikedace (discussed above), interference and exploitive competition with nonnative species can be detrimental to loach minnow. Interference competition, in the form of predation, may result from interactions between loach minnow and nonnative channel and flathead catfish, while exploitive competition likely occurs with red shiner. The discussion under Factor C above on disease and predation includes information on other nonnative aquatic species, such as Asian tapeworm, anchor worm, and Ich, which are also detrimental to loach minnow.

The discussion under spikedace on flooding and its benefits in potentially minimizing threats from nonnative fishes applies to loach minnow as well.

The information presented above indicates the detrimental effects of interference and exploitive competition with nonnative species to loach minnow, as well as the issues presented by the introduction of nonnative parasites. Therefore, based on this information, we identify the PBFs for loach minnow as follows:

• Habitat devoid of nonnative aquatic species, or habitat in which nonnative aquatic species are at levels that allow persistence of loach minnow; and

• Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Physical and Biological Features for Spikedace and Loach Minnow

Based on the above needs and our current knowledge of the life history, biology, and ecology of the species and the habitat requirements for sustaining the essential life history functions of the species, we have determined that PBFs for the spikedace are:

(1) Habitat to support all egg, larval, juvenile, and adult spikedace. This habitat includes perennial flows with a stream depth generally less than 1 m (3.3 ft), and with slow to swift flow velocities between 5 and 80 cm per second (1.9 and 31.5 in. per second). Appropriate stream microhabitat types include glides, runs, riffles, the margins of pools and eddies, and backwater components over sand, gravel, and cobble substrates with low or moderate amounts of fine sediment and substrate embeddedness. Appropriate habitat will have a low gradient of less than approximately 1.0 percent, at elevations below 2,100 m (6,890 ft). Water temperatures should be in the general range of 8.0 to 28.0 °C (46.4 to 82.4 °F);

(2) An abundant aquatic insect food base consisting of mayflies, true flies, black flies, caddisflies, stoneflies, and dragonflies;

(3) Streams with no or no more than low levels of pollutants;

(4) Perennial flows, or interrupted stream courses that are periodically dewatered but that serve as connective corridors between occupied or seasonally occupied habitat and through which the species may move when the habitat is wetted;

(5) No nonnative aquatic species, or levels of nonnative aquatic species that are sufficiently low as to allow persistence of spikedace; and

(6) Streams with a natural, unregulated flow regime that allows for periodic flooding or, if flows are modified or regulated, a flow regime that allows for adequate river functions, such as flows capable of transporting sediments.

Based on the above needs and our current knowledge of the life history, biology, and ecology of the species and the habitat requirements for sustaining the essential life history functions of the species, we have determined that PBFs for the loach minnow are:

(1) Habitat to support all egg, larval, juvenile, and adult loach minnow. This habitat includes perennial flows with a stream depth of generally less than 1 m (3.3 ft), and with slow to swift flow velocities between 0 and 80 cm per second (0.0 and 31.5 in. per second). Appropriate mic

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