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ASSESSMENT OF TAXA OF MANAGEMENT CONCERN IN THE COLORADO 

RIVER ECOSYSTEM, GLEN AND GRAND CANYONS, ARIZONA, USA: HABITAT 

NEEDS, AVAILABILITY AND ECOSYSTEM ROLES

DRAFT FINAL REPORT 15 JUNE 2011

EXECUTIVE SUMMARY 

Introduction

The loss of native species is one of the three largest human impacts on natural 

ecosystems. Removal of ecologically important foundation taxa (e.g., dominant trees, abundant 

prey taxa) or keystone species (e.g., species that influence trophic structure and composition), 

and the substitution of non-native taxa into those roles in altered habitats, affect structure, 

composition, function, and resilience, as well as the goods and services provided by those 

ecosystems. Understanding the distribution and ecological roles of native species that are 

declining or no longer present in altered environments provides long-term guidance on the 

stewardship of human-dominated ecosystems.

Here we describe the species known or suspected to be missing or in decline in the 

Colorado River ecosystem (CRE) in lower Glen Canyon and throughout Grand Canyon on the 

southern Colorado Plateau (Fig. 1). We provide approaches to understanding restoration 

potential to the Adaptive Management Work Group (AMWG) in response to its April 2009 

motion: “In recognition of GCDAMP [Glen Canyon Dam Adaptive Management Program] goals 

toward management of the Colorado River through an ecosystem approach, AMWG directs the 

TWG [Technical Work Group] to establish the Species of Concern Ad Hoc Committee 

[SMCAHC, (the Committee)] and requests the participation of GCMRC [U.S. Geological Survey 

Glen Canyon Monitoring and Research Center] in that ad hoc committee, to produce a draft 

report to be presented to AMWG on or before by May 1, 2011, that contains the following with 

regard to species of management concern in the CRE: A review of information about an 

assessment of the status of habitat needs and availability, and ecosystem roles of the species.”

The focus of this report is the array of native plant and animal taxa of management 

concern (TMC) in the CRE. TMC were defined as native CRE species that were: presently or 

recently federally listed or were recent candidate species; federally or state protected; believed 

by the Committee to be declining, extirpated, or extinct; or rare endemic taxa or highly isolated 

populations, as well as those for which too few data are available to assess present status 

(Appendix A). TMC were selected by the Goal 3 Ad Hoc Committee (the Committee) based on 

peer-review published and government literature, recommendations from staff and independent 

experts, and published and unpublished literature (including Grand Canyon Wildlands Council, 

Inc. 2009).

Methods

The Committee developed the TMC list from diverse information sources, and 

investigated four restoration prioritization approaches. All approaches involved multiple 

unweighted criteria, scoring by independent experts and knowledgeable TWG staff, and 

considerable discussion within the Committee. The Committee considered a suite of 18 issues 

that influence decisions about population restoration (Table 1). These questions involved the role 

of the dam in the population decline, conceptual and practical restoration issues (e.g., stock 

availability), the ease with which restoration could be accomplished, the conservation 

significance of the action, and the level of stakeholder agreement for restoration. Scoring was 
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performed by Committee members, expert staff from TWG participating agencies, and 

independent academic experts, each of whom scored each issue for each taxon with which they 

were familiar. We used a 0 (no value, low restoration potential) to 4 (high importance, high 

restoration potential) scoring scale, and variables were not weighted. A total score was calculated 

for each species based on the total percent possible of non-blank issues scores. Other 

prioritization approaches involved consideration of policy but less quantification: 1) extirpated 

taxa; 2) TMC that were endangered, declining, rare, or already included in existing conservation 

plans; 3) taxa of interest because: a) distribution and status data are insufficient; b) species of 

individual agency concern, including Tribally important taxa; c) incidentally occurring rare 

species; d) species known or suspected to be affected by dam operations, which may be 

increasing; e) species suspected to be declining directly or indirectly due to dam operations; f)

federally protected non-native taxa (feral burro). Lastly, we conducted a post-process “reality 

check” by the Committee to confirm whether information was sufficient to recommend a taxon 

to the AMWG for further consideration. We also reviewed the trophic status of each TMC in 

relation to the overall CRE and we discuss restoration requirements and long-term ecosystem 

management implications of these findings. 

Results

Extirpated Taxa: At least 14, and as many as 23 animal species that formerly bred in the CRE 

have been extirpated, with only two of those prior extirpations occurring prior to the closure of 

Glen Canyon Dam in 1963 (Table 2; Appendix A). TMC known to have been extirpated include: 

4 fish (Colorado pikeminnow – Pychocheilus lucius, razorback sucker – Xyrauchen texanus, and 

bonytail and roundtail chub – Gila elegans and G. robusta, respectively), 2 amphibians 

(Lithobates pipiens and L. nr. yavapaiensis), zebra-tailed lizard, 4 birds (breeding southwestern 

willow flycatcher – Empidonax trailii extimus; western yellow-billed cuckoo - Coccyzus 

americanus occidentalis, Gambel’s quail - Callipepla gambelii, and California condor -

Gymnogyps californianus, which was reintroduced outside the CRE in 1996); and 3 mammals 

(badger – Taxodea taxa; the likely extinct southwestern river otter – Lutra canadensis Sonora;

and gray wolf, Canis lupus youngi which was extirpated from northern Arizona by 1945). The 

status of several apparently rare herpetofauna (e.g., regal ring-necked snake – Diadophis 

punctatus regalis, western threadsnake – Leptotyphlops humilis, other snakes), as well as 

numerous rare plant and invertebrate taxa, remains unknown. 

Endangered or Previously Listed TMC: A total of 18 taxa (21.2 percent) are presently or 

recently have been federally or state-protected, or are of specific importance to Tribes, either 

through the ESA, through separate federal legislation, or through state or Tribal recognition. 

Among these 18 taxa are at least 10 extant endangered species in the CRE, including: 1 

terrestrial gastropod , 1 fish species, 4 bird species, and several incidentally-occurring listed bird 

taxa.

Non-listed Extirpated, Declining, and At-risk TMC: Extirpated or at-risk species that are not 

federally listed make up the majority of those on the list in the CRE in post-dam time. A total of 

46 (54 percent) of the TMC had restoration potential scores >50, suggesting that they may 

warrant management attention or at least monitoring. However, the quality of status and 

distribution data on at least 52 (61 percent) of the TMC was inadequate to determine 
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management needs or options, including rare invertebrate, herpetofaunal (especially amphibians 

and snakes), rodent, and migratory bird and bat taxa. 

Non-Native Species: Although the focus of this report is on native TMC, we note the presence of 

several hundred non-native taxa (particularly plants, fish, several invertebrates, and several bird 

taxa) that occur in the river corridor, interact with native species in complex fashions, and play 

important ecological roles in the CRE. A more comprehensive ecosystem-based understanding of 

the role of non-native species is warranted.

Dispersal Limitations: Glen Canyon Dam may play a long-term role in CRE diversity through 

interruption of passive downstream or upstream propagule distribution. Prior to 1963, “waif” 

plant and animal species were transported via hydrochory or gravity into the CRE, becoming 

established, but often being too rare or physiologically stressed to reproduce successfully. Many 

unlisted but rare taxa identified in this analysis were downstream-dispersed waif species, known 

only from a few collections in the post-dam CRE. Upstream colonization via animal or wind 

transport is generally slower than downstream or gravity-based waifing recruitment, but both

dispersal processes are important long-term diversity in the CRE (Stevens and Waring 1987; 

Stevens and Polhemus 2008; Stevens and Bailowitz 2009). Glen Canyon Dam likely has limited 

the dispersal of waif taxa propagules (e.g., Shafroth et al. 2002), potentially reducing long-term 

CRE biodiversity.

Trophic Status of TMC: We analyzed the trophic status of extirpated and at-risk TMC among 

the array of narrow and wide reaches of the CRE (Schmidt and Graf 1990), demonstrating that 

the presently monitoring focus on 3 TMC (i.e., humpback chub – Gila cypha, Kanab ambersnail

– Oxyloma haydeni kanabensis, and southwestern willow flycatcher) occupy lower and middle 

trophic positions. While those focal species are administratively important, they may not provide 

adequate “umbrella” protection for most other CRE TMC and important ecological processes. 

Therefore, the usefulness of these 3 endangered taxa for understanding and managing the full 

array of ecosystem dynamics is limited (Stevens et al. 2001). Two groups of terrestrial CRE 

species in particular have not received sufficient monitoring or conceptual attention: top riparian 

predators, and rare or endemic taxa, including insects. Additional monitoring data are needed on 

such species to develop a more thoroughly linked aquatic-terrestrial conceptual ecosystem model 

for the CRE, and such an effort is likely to better serve long-term CRE management and the 

AMP. 

TMC Restoration

Restoration of TMC must be consistent with NPS and other managing agencies 

reintroduction policies, but heretofore has been regarded as a tertiary priority, behind improving 

the population health of one federally listed fish species (humpback chub), and sediment 

management. Thus, questions of whether, how and when to restore other at-risk or extirpated 

endangered or non-listed species remain unaddressed. Unfortunately, major information gaps 

exist with regards to understanding the distribution and present status of many TMC in the CRE. 

Such information and discussion may play an important role in the planning and implementation 

of population reintroduction and restoration actions. We describe and discuss issues associated 

with reintroduction of extirpated CRE TMC, including: a) development of the administrative 

context; b) compiling relevant information, stock assessment, and prioritization, c) plan 
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development, d) multi-agency compliance, e) implementation, potentially with multiple stocking 

efforts, and f) integration of monitoring and feedback information.

Discussion

Ecosystem management requires adequate understanding of the ecological role and 

potential for restoration of extant TMC as well as extirpated species and processes.

Understanding the feasibility and advisability of restoration of extirpated species is coordinated 

through Goal 3 of the AMWG mission, and also by the wildlife managing agency stakeholders, 

most notably the NPS, FWS, and AGFD, and several Native American Tribes. Filling 

information gaps about missing or declining species is needed to more fully inform the Secretary 

of the Interior about Glen Canyon Dam impacts, as well as providing information for the 

compliance requirements of AMWG cooperating agencies needed to undertake reintroduction 

efforts. Through its multi-stakeholder structure, AMWG is uniquely poised to recommend to the 

Secretary of the Interior the technical, interagency, and societal information needs and processes 

through which to achieve the purposes of AMWG’s Goal 3. There is at present no commitment 

for the AMP to fund TMC restoration efforts, as such activities may be the specific purview of 

the resource managing agencies. Nonetheless, the AMWG can play an important multi-agency 

advisory role to the Secretary in evaluating TMC restoration priorities and potential in the CRE. 

In addition, the AMP may benefit from monitoring information about reintroduced or 

translocated TMC, as well as in public outreach. We provide previously uncompiled background 

information on missing and at-risk species, and summarize approaches to assess TMC 

prioritization potential. We offer this information as guidance to the AMWG, recognizing that 

the diverse views among AMWG stakeholders as to the AMP’s responsibilities require further 

discussion about roles and responsibilities for CRE management.

Two administrative issues emerged from this analysis that previously have not been 

discussed by the AMWG. First, many TMC were recognized in the CRE that may warrant 

management or monitoring attention, either by the AMWG and/or by other managing agencies. 

A total of 47 (54 percent) of the 85 TMC considered here had potential restoration scores > 50 

percent (Table 2; Appendix A). Also, many species with scores <50 percent lacked critical 

information on distribution, habitat use, or population status. Abundant opportunity exists to 

improve the quality of basic information on TMC in the CRE. 

Second, AMWG monitoring recommendations currently focus primarily on humpback 

chub, as well as flow and sediment transport, with less attention on Kanab ambersnail and 

southwestern willow flycatcher. However, at least 5 species (1 plant, 1 lizard, and 3 non-listed 

fish) scored higher than humpback chub in our analyses. Concern for Goodding’s willow arose 

due to its CRE-wide demise in the post-dam river corridor. Concern for the 3 non-listed CRE 

fish arose from the desire of the Committee to prevent those species from becoming federally 

endangered. The zebra-tailed lizard scored above HBC because its population restoration would 

be inexpensive and easily accomplished. AMWG may choose to engage in further discussion of 

the restoration potential of these and other TMC, and we hope that the information provided here 

contributes to those discussions and to improved stewardship of the CRE.
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INTRODUCTION

Impacts of Native Species Loss on Ecosystems

The loss of native species is one of the three largest human impacts on natural 

ecosystems. Removal of ecologically important foundation taxa (e.g., dominant trees, abundant 

prey taxa) or keystone species (e.g., taxa that strongly influence trophic structure and 

composition), and the substitution of non-native taxa into those roles in altered habitats affect the 

structure, composition, function, and resilience, as well as the goods and services provided by 

those ecosystems. Understanding the distribution and ecological roles of native species that are 

declining or no longer present in regulated rivers, such as the Colorado River ecosystem (CRE) 

in lower Glen Canyon and throughout Grand Canyon on the southern Colorado Plateau, is 

fraught with uncertainties because: 1) information on the natural condition of those populations

and the ecosystem in general often is limited, and 2) novel arrays of environmental gradients and 

trophic linkages arise in anthropogenically altered ecosystems, affecting native species 

population dynamics, as well as ecosystem processes and functions. Accounting for missing or 

declining species and the ecological processes that characterized the natural ecosystem is 

fundamental to adaptive management (Walters et al. 2000). Failure to account for missing 

species, coupled with continued species loss, means that iterative planning and stewardship 

efforts result in stepwise degradation of ecosystem integrity. Understanding the extent of species 

loss and restoration potential allows ecosystem stewards to define and manage for desired future 

ecosystem conditions (Schmidt et al. 1998, Myers et al. 2007).

Figure 1: Map of the Colorado River ecosystem between Glen Canyon Dam and Lake Mead, 

Arizona. Turbidity segments: VT – variably turbid, UT – usually turbid.
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Species Loss in the Grand Canyon Region

As has occurred in many of the nation’s great landscape parks, a substantial number of 

native taxa have been extirpated or appear to be at risk in the CRE (Minckley 1991, Newmark 

1995, Stevens et al. 2001, Stevens and Gold 2003). Much ecological research has been devoted 

to the study of reduced or dwindling populations of currently endangered species in the CRE, 

particularly the big river fishes, and specifically humpback chub (HBC; Gila cypha; Minckley 

1991; Valdez and Ryel, 1995, 1997; Marsh and Douglas 1997; Stone and Gorman 1999; Gloss et 

al. 2005; Coggins 2008; Coggins and Walters 2009; Andersen et al. 2010; Yard et al. 2011), as 

well as one landsnail (Kanab ambersnail – KAS, Oxyloma haydeni kanabensis; Spamer and 

Bogan 1994; Meretsky et al. 2000) and one bird species (southwestern willow flycatcher –

SWFL, Empidonax trailii extimus; summarized in Paxton et al. 2007). Federal listing prompted 

ecological research on other formerly listed CRE taxa, including bald eagle (Haliaeetus 

leucocephalus; Brown et al. 1989, 1998; Brown and Stevens 1997) and peregrine falcon (Falco 

peregrinus anatum; Brown et al. 1992; Stevens et al. 2009). However, the ecological roles and 

distributions of other endangered species that occur incidentally in or near the river corridor 

(e.g., California condor - Gymnogyps californicus; Mexican spotted owl - Strix occidentalis 

lucida), as well as non-listed endemic, declining, or extirpated species, is less well known. 

Umbrella species are those that, when conserved, provide protection to co-occurring taxa, 

habitats, or ecosystems. While often a useful effort, meta-analyses of this process suggested that 

focal species selection required careful assessment of the ecological roles of many species 

(Branton and Richardson 2010). Importantly, federally endangered (“listed”) taxa may not 

necessarily serve as adequate umbrella taxa (Roberge and Angelstam 2004), particularly in 

complex landscapes. Ozaki et al. (2006) reported that northern goshawk (Accipiter gentilis), a 

wide-ranging predator that facultatively adapts to anthropogenically altered landscapes, did not 

provide adequate protection for associated species and habitats. 

Although HBC is used as a focal species for CRE management, but adults are relatively 

low-vagility fish that and almost exclusively spawn in the lower Little Colorado River, a springfed tributary in Grand Canyon. Therefore, HBC may not well represent the ecosystem 

requirements of more highly migratory fish species, such as razorback sucker (RBS; Xyrauchen 

texanus) or Colorado pikeminnow (CPM; Pychocheilus lucius), both of which have been 

extirpated, or terrestrial species (e.g., KAS or SWFL; Stevens et al. 2001). A broader 

examination of the status of taxa of management concern (TMC) in the CRE can provide insight 

into improved stream-riparian ecosystem restoration options, consideration by the Glen Canyon 

Dam Adaptive Management Program (AMP), and provide support to the National Park Service 

(NPS) and other resource managers working to fulfill responsibilities, such as that of the NPS to 

“... strive to understand, maintain, restore, and protect the inherent integrity of the natural 

resources, processes, systems, and values of parks ... (U.S. National Park Service 2006:36). 

Ecosystem Roles of Extirpated or Declining Taxa 

Extirpated and declining taxa, both federally listed or not, may have had important 

ecosystem roles, and the loss of those species may greatly compromise ecosystem function

(Soulé et al. 2005; Myers et al. 2007). Because of the important role of keystone (ecologically 

strongly interacting species) on ecosystem function, and because the legal framework may not 

have kept up with advances in ecosystem and conservation ecology, Soulé et al. (2005) 

recommend that natural resource managers...”adhere to a doctrine of ‘best conservation 

practices based on the best science,’ applying a more rigorous standard for the management of 
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relatively interactive species than may be mandated by older statutes and effected by current 

practice and convention.” In addition, little scientific attention has been paid to the distribution 

and conservation of rare and endemic taxa, in Grand Canyon and elsewhere, particularly 

invertebrates, for which few population status or life history data exist. The continued health of 

those populations may be jeopardized by uninformed or insensitive land management practices. 

For example, Stevens and Polhemus (2008) reported that 52.6% of 89 aquatic Heteroptera 

species in the Grand Canyon region were found at 3 or fewer sites, and that more than 25% were 

found only at single localities, primarily springs. Springs in the vicinity of Grand Canyon are 

widely recognized as being threatened by regional groundwater pumping. External threats to the 

regional aquifers around Grand Canyon may affect discharge of springs and therefore the 

habitats of many springs-requiring species. Groundwater pumping may threaten the flow of Blue 

Springs in the lower Little Colorado River, a springs complex that provides essential flow for 

spawning humpback chub. Therefore, management of both species and habitats in a regional 

context may be needed to maintain and restore species and ecosystem health.

Species Translocations and Reintroductions in the Grand Canyon Region 

The establishment and translocation of native and non-native species has a lengthy 

history in the CRE. Federal management of the North Rim early in the 20th Century involved 

widespread elimination of upland predators, actions that may have had large impacts on 

ecosystem structure (Rasmussen 1941). Exotic plants in the CRE include tamarisk (Tamarix

spp.), Russian olive (Elaeagnus angustifolia), and more than 75 other species (Stevens and Ayers 

2002). Numerous aquatic invertebrate taxa were released by the AGFD into the tailwaters of 

Glen Canyon Dam in the mid-late 1960’s to improve the aquatic foodbase (Stone and Queenan, 

1967; Stone and Rathbun 1968, 1969). Endangered Kanab ambersnail were successfully 

introduced into upper Royal Arch Creek in Grand Canyon in 1998 by AGFD and the NPS to 

develop a refuge population if dam operations negatively affect natural snail habitat at Vaseys 

Paradise Spring in the CRE (Spamer and Bogan 1994; Sorensen 2005). Introduced fish include 

common carp (Cyprinus carpio) and catfish (Ictaluridae), which already were the most abundant 

fish in the lower Colorado River by the turn of the Twentieth Century (Grinnell 1914). Rainbow 

(Oncorhynchus mykiss) and brown trout (Salmo trutta) were released by the NPS shortly after 

the establishment of Grand Canyon National Park, and 17 other non-native fish species also have 

become established. Rainbow trout became an important recreational resource in Glen Canyon 

following closure of the dam in 1963, but trout piscivory may threaten native fish (Yard et al. 

2011). The NPS, FWS, and AGFD have translocated HBC into previously unoccupied habitat in 

the Little Colorado River, upstream from a barrier falls (U.S. Fish and Wildlife Service 2010), 

and into Shinumo Creek. Non-native burros (Equus asinus) were widely introduced by early 

prospectors, and were removed from Grand Canyon National Park and most of the CRE in the 

early 1980s. Semi-native terrestrial vertebrate introductions include: wild turkey (Meleagris 

gallopavo; Brown et al. 1987), bighorn sheep (Ovis canadensis nelsoni) in upper Grand Canyon. 

Restoration of endangered California condor (Gymnogyps californianus) generally has been 

successful (Southwest Condor Release Team 2007); however, Meretsky et al. (2000a) question 

whether reintroduction can be successful because of condor susceptibility to lead poisoning, an 

issue that has lead to a proposed ban on lead shot. Grand Canyon supports the largest breeding 

population of previously federally listed peregrine falcons (Falco peregrinus anatum) of any 

land management area in the lower 48 states as a result of pesticide control and reintroduction 

efforts elsewhere in the Colorado River basin in the early 1980’s (Brown et al. 1992; Stevens et 
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al. 2009). Louisiana river otters (Lontra canadensis lataxina.) were translocated into the upper 

Colorado River and Verde River drainage in Arizona, restoring their contribution to ecosystem

function (GCWC 2005). Clearly, much of the CRE has been affected by these introductions and

translocations. 

Adaptive Management Goal 3

The Adaptive Management Work Group (AMWG) approved the following motion at its 

April 2009 meeting: 

In recognition of GCDAMP [Glen Canyon Dam Adaptive Management Program] 

goals toward management of the Colorado River through an ecosystem approach, 

AMWG directs the TWG [Technical Work Group] to establish the Species of 

Concern Ad Hoc Committee (SMCAHC) and requests the participation of 

GCMRC [U.S. Geological Survey Glen Canyon Monitoring and Research Center] 

in that ad hoc committee, to produce a draft report to be presented to AMWG on 

or before by May 1, 2011, that contains the following with regard to species of 

management concern in the CRE: A review of information about an assessment of 

the status of habitat needs and availability, and ecosystem roles of the species.

This directive requires a more complete review of information on the distribution, status, 

ecological role(s) than has heretofore existed, as well as development and testing potential 

methods to prioritize the reintroduction potential of extirpated and at-risk TMC to better

understand and manage the CRE as an ecosystem. 

Here we present a list of the native CRE TMC, including extirpated, endangered, 

declining, or those for which insufficient data exist to determine current population status. We 

describe the distribution, habitat requirements, ecological role(s), status, and the quality of 

information available on those species. We integrate selected taxa into a conceptual trophic 

diagram of the CRE, discuss the advantages and challenges associated with developing a more 

complete understanding of their status, and present approaches for prioritizing the reintroduction 

potential of extirpated, endangered, or declining species.. We briefly review the compliance 

requirements of participating agencies in relation to reintroduction efforts. We provide this 

information to assist in the adaptive management process for the CRE move towards a more 

comprehensive ecosystem management perspective. 

METHODS

Study Area 

The CRE under the purview of the AMWG extends from the forebay of Lake Powell and 

Glen Canyon Dam in Glen Canyon National Recreation Area (GLCA) and for a total distance of 

447 km downstream through Grand Canyon National Park (GRCA) to the boundary of Lake 

Mead National Recreation Area at about Colorado River Mile (RM) 278 (Fig. 1). The CRE 

includes the river and shorelines within the 100-yr flood stage, the lower portions of selected 

tributaries, and the lower 15 km of the Little Colorado River. River mile (RM) from Lees Ferry 

is traditionally used to designate location in the CRE, with mileage measured for both upstream 

(negative) and downstream (positive) distance. The side of the river is designated looking 

downstream (right=R or left=L).
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The CRE is managed under several administrative processes. The National Park Service 

(NPS) manages natural and cultural resources of 2 NPS unit (Grand Canyon National Park and 

Glen Canyon National Recreation Area), pursuant to Grand Canyon National Park enabling 

legislation (1919), Glen Canyon National Recreation Area enabling legislation (1972), the NPS 

Organic Act (1916), and subsequent legislation including the 1992 Grand Canyon Protection 

Act, and in accord with: the U.S. Fish and Wildlife Service (FWS) and the Endangered Species 

Act of 1973 (ESA) and the Fish and Wildlife Coordination Act (FWCA); the Arizona 

Department of Water Resources and the Arizona Game and Fish Department (AGFD) 

administrative water, fish and wildlife policies and regulations; and those of six actively 

participating Native America Tribes. Glen Canyon Dam management is achieved though 

Secretarial advisement by the Bureau of Reclamation’s Adaptive Management Work Group 

(AMWG)—a Federal Advisory Committee composed of representatives from the major 

stakeholder groups (Stevens and Gold 2003, Melis and Lovich 2005), and by the Colorado River 

Annual Operating Plan (AOP) group. The Secretary of the Interior is the Water Master of the 

Colorado River and integrates recommendations from both AMWG and the AOP group. Goal 3 

of the Glen Canyon Dam Adaptive Management Program (AMP) is to “Restore populations of 

extirpated species, as feasible and advisable.” The AMWG developed the above-quoted motion 

to provide relevant information as a comprehensive first step towards achieving Goal 3.

Information Sources

The focus of this document is the array of native plant and animal taxa of management 

concern (TMC) in the CRE. TMC were defined as native CRE species (but including federally 

protected non-native feral ass, Equus asinus) that were: presently or recently federally listed or 

were recent candidate species; Arizona state listed; federally protected; believed by the 

Committee to be declining, extirpated, or extinct; or rare endemic taxa or highly isolated 

populations, as well as those for which too few data are available to assess present status

(Appendix A). TMC were selected by the Goal 3 Ad Hoc Committee (the Committee) based on 

peer-review published and government literature, and recommendations from staff and 

independent experts, as well as the published and unpublished literature, including a regional 

conservation area plan developed by Grand Canyon Wildlands Council, Inc. (2009).

Restoration Scoring and Prioritization

The Committee developed the TMC list from diverse information sources, and 

investigated four restoration prioritization approaches. First, the Committee considered a suite of 

18 issues that influence decisions about population restoration (Table 1). These questions 

involved the role of the dam in the population decline, conceptual and practical restoration issues 

(e.g., stock availability), the ease with which restoration could be accomplished, the conservation 

significance of the action, and the level of stakeholder agreement for restoration. Scoring was 

performed by Committee members, expert staff from TWG participating agencies, and 

independent academic experts, each of whom scored each issue for each taxon with which they 

were familiar. We used a 0 (no value, low restoration potential) to 4 (high importance, high 

restoration potential) scoring scale, and variables were not weighted. A total score was calculated 

for each species based on the total percent possible of non-blank issues scores. The level of 

stakeholder agreement was not sufficiently well-understood by the collaborators, so that criterion 

was excluded from the scoring analysis. Other prioritization approaches involved consideration 

of policy issues, including whether the TMC: 1) had been extirpated; 2) were endangered, 
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Table 1: Issues related to restoration potential of species of management concern in the CRE. 

Each issue was scored on a 0 to 4 scale by each expert within a taxon, where information was 

deemed sufficient. The total score was the percent of possible scores excluding missing or blank 

values. Asterisk (*) denotes an issue not included in analyses.

Potential Restoration Issues

Influence of Glen Canyon Dam on population

Conservation relevance

Quality of background information

Stock availability for restoration

Legal mandates, requirements

Habitat availability under present dam operations

Habitat availability under realistic future dam operations

Technical feasibility

* Agreement among stakeholders

Inexpensiveness (low cost=high score)

Time-frame for success (short=high, long=low)

Logistical ease

Ease of compliance

Are genetics issues easily resolved?

Lack of disease transmission potential

Urgency in relation to climate change impacts

Beneficial interactions with other species

declining, rare, or already included in existing conservation plans; 3) were of interest because: a) 

distribution and status data were insufficient; b) were species of individual agency concern, 

including Tribally important taxa; c) occurred incidentally; d) were known or suspected to be 

positively affected by dam operations; e) were known or suspected to be declining directly or 

indirectly due to dam operations; or f) were federally protected non-native taxa (i.e., feral burro). 

Lastly, the Committee conducted a post-process “reality check” to confirm whether the compiled 

information about each TMC was sufficient to forward a recommendation to the AMWG for 

further consideration. Reality check responses were summarized into 3 categories of response: 

“yes” (unanimous agreement of those voting), “mixed” (a mixture of yes and no votes), and “no” 

(unanimous agreement not to consider a taxon further in this process). Although a “no” vote may 

apply to the AMWG process, individual agencies still maintain management interests in those 

species, both within and outside the CRE. All of the above prioritization approaches involved 

multiple unweighted criteria, scoring by independent experts and knowledgeable TWG staff, and 

considerable discussion within the Committee. We also reviewed the trophic status of each TMC 

in relation to the overall CRE, and we discuss restoration requirements and long-term ecosystem 

management implications of these findings. 

RESULTS

Overview

We assessed the status and restoration potential of a list of 85 TMC from the CRE

(Appendix A; Table 2). A total of 18 taxa (21.2 percent) are presently or recently have been 

federally or state-protected. Four federally endangered fish species have been extirpated, as have 

2 candidate leopard frog species, and 3 bird species. Formerly listed peregrine falcon and bald
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Table 2: Summary of prioritization approaches for taxa of management concern (TMC) in the 

Colorado River ecosystem downstream from Glen Canyon Dam. Cells totals do not sum because 

some taxa qualify in multiple categories. Appendix A contains detailed accounts of the scoring 

of each TMC.

Number of CRE TMC

Criterion

PlantsTrematodeInsectsSnailsFishAmphibiansReptilesBirdsMammals

Total

Extirpated 2? 0 2? 0 4 2 2 3 

(4) 8 14-23

Federally ES or recent ES 0 0 0 1 5 2 0 9 1 18

Composite Score >50 0 1 3 1 8 3 3 9 19 47

3a. TMC about which little is known 1 0 9 0 3 2 5 6 26 52

3b. TMC of individual agency concern 6 0 3 1 8 4 3 16 21 62

3c. Rare or endemic TMC 1 1 3 1 0 1 0 5 2 14

3d-e. TMC affected by dam, (+ 

increasing or - decreasing) 6 1 4 1 8 4 4 13 11 52

Reality Check ("yes") 4 0 0 1 6 0 0 2 0 13

Reality Check ("mixed") 3 1 9 0 2 4 6 17 31 73

Total number TMC * 7 7 9 1 8 4 6 19 31 85

eagle are extant. All presently or formerly ESA-listed and candidate species also are recognized 

as Species of Greatest Conservation Need in Arizona’s State Wildlife Action Plan (SWAP; 

AGFD 2006). Several TMC not federally listed have been extirpated, including one lizard and 

the likely extinct southwestern river otter, with loss of river ecosystem function (GCWC 2005). 

Only 2 species (HBC, KAS; 2.5 percent of the total TMC) are regularly monitored by the 

AMWG program, while the NPS monitors SWFL. 

A total of 46 (54 percent) of the TMC had restoration potential scores >50, suggesting 

that they may warrant management attention or at least monitoring. All native migratory bird 

species are federally protected under the Lacey Act of 1900 and the Migratory Bird Protection 

Act of 1918, and their habitats whenever flows in the Colorado River are modified due to 

operations of Glen Canyon Dam under the Fish and Wildlife Coordination Act (FWCA) of 1934, 

as amended. Additionally, the habitat requirements of fish species that are not listed and 

protected by the Endangered Species Act of 1973, as amended, are similarly protected under the 

FWCA. However, the quality of status and distribution data on at least 52 (61 percent) of the 

TMC was inadequate to determine management needs or options, including rare invertebrate, 

herpetofaunal (especially amphibians and snakes), rodent, and migratory bird and bat taxa. In the 

following section, we describe extirpated, federally or state listed or former candidate taxa, and 

rare, endemic and at-risk TMC.
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SPECIES ACCOUNTS

Extirpated Taxa

At least 14, and as many as 23 animal species have been extirpated from the CRE, all but 

two of those since the closure of Glen Canyon Dam in 1963 (Table 2; Appendix A). TMC known 

to have been extirpated include: 4 fish (Colorado pikeminnow, razonback sucker, and bonytail 

and roundtail chub), 2 amphibians (Lithobates pipiens and L. nr. yavapaiensis), zebra-tailed 

lizard, 4 birds (i.e., breeding southwestern willow flycatcher; yellow-billed cuckoo, Gambel’s 

quail, and California condor, which was reintroduced outside the CRE ON 12 December 1996; 

and 3 mammals (including: badger – Taxodea taxa, southwestern river otter – Lutra canadensis 

sonora, and gray wolf, Canis lupus, extirpated from northern Arizona by 1945). The status of 

several apparently rare herpetofauna, including regal ring-necked snake, western threadsnake, 

and other snakes remains unknown. 

Razorback Sucker (RBS; Xyrauchen texanus): RBS were previously widely distributed and 

highly migratory in the Colorado River, but have been extirpated from the CRE (Dowling et al. 

1996, Mueller et al. 2000). RBS presently are being raised and restocked into lower Colorado 

River reservoirs, including golf course ponds. RBS restoration downstream from Glen Canyon 

Dam may require continued stocking if recruitment fails and non-native predator control efforts 

are not successful. Discussion of RBS reintroduction into Grand Canyon is on-going. RBS in 

spawning condition and early stage larvae have recently been collected near the CRE inflow to 

Lake Mead, and the species is recruiting successfully in other parts of Lake Mead (http://www. 

usbr.gov/uc/feature/Razorback/index.html, accessed February 7, 2011 )

Colorado Pikeminnow (CPM; Ptychocheilus lucius): CPM were the largest native fish in the 

pre-dam Colorado River. Called “white salmon” or “Colorado River salmon” by early settlers,

this species apparently undertook long annual migrations through much of the Colorado River

basin (Sigler and Sigler 1996). Breeding populations are now restricted to the upper Colorado 

River basin. CPM is a large, piscivorous species, and restoration of CPM in the CRE likely will 

require analysis of reintroduction success in this regulated reach, as well as potential predation 

impacts on HBC.

Bonytail and Roundtail Chub (BTC, RTC; Gila elegans and G. robusta, respectively): BTC 

were previously known from near Glen Canyon Dam and Lake Mead (Minckley 1973), but at 

this time there are no known wild populations of Gila in the mainstream lower Colorado River

downstream from Grand Canyon. Augmented populations are sustained by stocking in both Lake 

Havasu and Lake Mohave. The pre-dam distribution of RTC is not well documented, but is 

reported as primarily taking place in tributaries of the Colorado basin, not in the mainstem

Colorado River downstream of Glen Canyon Dam (Holden and Stalnaker, 1975). Restoration or 

reintroduction of BTC and RTC generally have not been considered because of the potential for 

hybridization with HBC. Douglas and Douglas (2006) analyzed Gila genetics, concluding that 

the Grand Canyon population was distinct, but indicating some intergradation with other Gila

species. Therefore, introduction of other Gila species into Grand Canyon is contraindicated, at 

least at present, as it might threaten the genetic integrity of the Grand Canyon HBC population.

Lowland Leopard Frog (Lithobates nr. yavapaiensis; LLF): A single population of leopard 

frog was detected in lower Grand Canyon at Surprise Canyon (Colorado River Mile 248R; 
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Brennan and Holycross 2005). This population has been documented along the Colorado River

(L.E. Stevens, unpublished photograph) but not in recent decades, and primarily occurs several 

km upstream in Surprise Canyon. This leopard frog population is highly isolated and may be a 

unique form of L. yavapaiensis (Oláh-Hemmings et al. 2010). 

Northern Leopard Frog (NLF, Lithobates pipiens): Northern leopard frog was detected at 

Cardenas Creek (RM 71L; Tompko 1976; Miller et al. 1981) and at -9 Mile Marsh upstream 

from Lees Ferry (Brennan and Holycross 2005). The Cardenas Marsh backwater has filled with 

sediment and both historical sites have been heavily colonized by Phragmites australis, 

rendering them unsuitable as NLF habitat. NLF have not been detected at Cardenas Marsh since 

1975 or at -9 Mile Marsh since the late 1990s, and this species is considered to have been 

extirpated from the CRE. A small population also was detected at Hidden Sloughs (-6.5R) in the 

mid-1990’s but was likely introduced there and has not persisted (J. Spence, NPS Biologist, 

personal communication). Historical records of northern leopard frogs exist from Bright Angel Creek 

and lower Kanab Creek, but recent, intensive searches by the U.S. Geological Survey and Northern 

Arizona University have failed to reveal any extant populations (C. Drost, U.S. Geological Survey 

biologist, personal communication).

Southwestern Willow Flycatcher: Migrant and breeding SWFL have been documented in the 

CRE at Lees Ferry and in lower Marble Canyon since the 1930s (Brown et al. 1987). However, 

breeding SWFL have disappeared from their historic range in eastern Grand Canyon, where they 

regularly nested until the late 1990s (Paxton et al. 2007). Loss of this nesting population has been 

attributed to external factors, such as winter habitat alteration, as well as changes in the CRE, 

such as increased brown-headed cowbird (Molothrus ater) brood parasitism (Brown et al. 1992; 

review in Paxton et al. 2007). Single male SWFL are still occasionally detected singing along the 

river in upper Grand Canyon, and limited breeding occasionally occurs along the Colorado River 

in Lake Mead, but such activities are erratic. Although SWFL occupies earlier successional 

stages of riparian habitat, effective conservation of SWFL could umbrella coverage of some of 

the more than two dozen other neotropical migrant birds that nest in the CRE riparian zone 

(Brown et al. 1987; Stevens et al. 2001). Many other neotropical breeding species also are 

negatively affected by cowbird brood parasitism. 

Western Yellow-billed Cuckoo (YBCU; Coccyzus americanus occidentalis): Listed as a 

federally threatened species, YBCU requires gallery riparian forest, and therefore is not wellprotected by conservation of endangered SWFL, which requires relatively early seral 

successional riparian vegetation (Layman and Halterman 1987, Brown et al. 1987). In contrast, 

YBCU requires more-or-less continuous tall-canopy riparian cottonwood and willow cover. 

YBCU is known in the CRE from a single report in Marble Canyon by Brown et al. (1987), at 

RM -14.2 in 1995, and at Lee's Ferry (LaRue et al. 2001), but it has not been detected in the CRE 

in more a decade. YBCU is identified as a Species of Greatest Conservation Need in Arizona’s 

SWAP (AGFD 2006). Depending on how the NPS manages tamarisk in the wake of the arrival 

of tamarisk leaf beetles (Diorhabda spp.), suitable riparian habitat can be promoted that may 

support this and many other neotropical migrant birds in the CRE. 

Plains Gray Wolf (Canis lupus youngi): Wolves were extirpated from the region by 1945 

(Rasmussen 1941, Hoffmeister 1986); however, John D. Lee reported seeing wolves on the south 

(left) bank of the river at Lees Ferry early in his tenure as ferryman there in the early 1960s 
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(Brooks and Cleland 2004). Wolf restoration is being tested to the south of the Grand Canyon 

region in Arizona; however, the subspecies most often suggested for restoration is the Mexican 

wolf (C. l. baileyi). Hoffmeister (1986) explicitly states that C. l .baileyi did not occur on either 

the south or north rims of Grand Canyon. Introduction of Mexican wolf north of the Colorado 

River could threaten the genetic integrity of the plains gray wolf farther north, and therefore is 

not advised. Consideration of wolf population restoration in the CRE was rejected by the 

Committee, as there is little to no relationship of dam operations on wolf recovery. 

Extant Endangered Taxa 

Overview: A total of 18 taxa (21.2 percent) are presently or recently have been federally or stateprotected, either through the ESA, through separate federal legislation, or through state or Tribal 

recognition, including 2 taxa protected under federal legislation in addition to the ESA. Extant 

endangered species in the CRE include 1 terrestrial gastropod , 1 fish species, 4 bird species, and 

several incidentally-occurring listed bird taxa.

Kanab Ambersnail: KAS occurs naturally in Arizona only at Vaseys Paradise Springs in the 

Colorado River in Grand Canyon, where it remains the focus of considerable taxonomic, 

ecological, and management debate (Spamer and Bogan 1993, Stevens et al. 2001). Although 

this taxon likely will be synonymized with O. h. haydeni on the basis of genetic analyses, until 

those analyses are published in the peer-reviewed scientific literature, KAS remains an 

endangered species and a highly restricted population, and therefore of concern in CRE 

management. The AGFD, NPS, FWS, Department of Interior Central Utah Project Completion 

Act Office, and Upper Colorado River Basin Office of the Bureau of Reclamation partnered 

beginning in 1996 to translocate populations of KAS into remote, off-river tributaries and springs 

in Grand Canyon, and the population in Royal Arch Creek has persisted since the 1998 

translocation, with protection under the ESA. This effort helped mitigate planned flooding 

impacts at Vaseys Paradise under a FWS Reasonable and Prudent Measure in 1996 and 1997 to 

find or create at least one population of KAS not influenced by Glen Canyon Dam (summarized 

by Sorensen 2005). 

 

Humpback Chub: HBC has received most of the species management attention in the AMWG 

program because Grand Canyon supports the largest naturally reproducing population of this 

endangered minnow species in the vicinity of the Little Colorado River (LCR). Intensive 

monitoring and non-native trout control programs (Grand Canyon Monitoring and Research 

Center 2008; Coggins et al. 2011; Yard et al. 2011) provide improved insight into long-term 

population trends, and in situ HBC population augmentation in the Little Colorado River 

upstream from the previously known range of HBC has been successfully undertaken by FWS, 

adding to the in-LCR population (Sponholtz and Stone 2004). Translocation also has been 

conducted by the NPS, FWS, AGFD, and collaborators into Shinumo and Havasu Creeks in 

central Grand Canyon, tributary populations that may help ensure in-Canyon persistence of the 

species (GCWC 2008; NPS 2011). The NPS and FWS also have discussed HBC translocation 

into Bright Angel Creek.

California Condor (Gynogyps californianus): External to the AMWG program and the National 

Park Service, reintroduction of endangered California condor into the Grand Canyon region has 

been remarkably successful, and Grand Canyon nests have successfully fledged young (Snyder 
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and Snyder 2000; Alagona 2004). Occupation and use of the CRE by condors is opportunistic, 

but external restoration efforts have restored this important top scavenger into the CRE. 

Management of condor-human interactions has proven challenging because condors are naturally 

attracted to human activities. 

Mexican Spotted Owl (MSOW); Strix occidentalis lucida): MSOW occasionally occur in the 

CRE, coming down from their normal ranges at the back of nearly every large tributary in central 

Grand Canyon (REF). MSOW have been observed and photographed at the mouths of tributaries 

such as Shinumo Creek and National Canyon (LES unpublished data, LaRue et al. 2001). 

Although apparently incidental in the CRE, the high density of riparian rodents may attract this 

species; however, MSOW occurrence in the CRE is fairly rare and the population certainly does 

not depend on riparian or dam-related resources. 

Bald Eagle (BAEA; Haliaeetus leucocephalus): Although fully delisted since 2007, BAEA are 

still protected under the 1940 Bald Eagle Protection Act, and therefore continue to be TMC in 

the CRE. Wintering BAEA colonized Grand Canyon beginning in 1982, and were regularly 

monitored until the mid-1990s (Brown et al. 1989). Their feeding behavior and distribution are 

strongly affected by dam operations and human recreational disturbance (Brown and Stevens 

1997, Brown et al. 1998). However, CRE monitoring data on CRE bald eagles over the past 

decade are not known to us. 

Peregrine Falcon (PEFA; Falco peregrinus): Delisted from endangered species status in 1999, 

PEFA have become a common top predator in the CRE (Brown et al. 1992, Stevens et al. 2009). 

Grand Canyon PEFA are presently monitored by NPS, but population trends and ecological 

impacts on the CRE avian assemblage, if any, are unclear. 

Incidentally-Occurring Listed Species: Several other listed species occur or may occur on an 

incidental basis in the CRE, including: mountain plover (Charadrius montanus), which is 

proposed for listing as threatened (proposed rule June 29, 2010, FR 75 37353), and the recently 

delisted brown pelican (BRPE; Pelicanus occidentalis). The occurrence of these species is 

incidental in the CRE (Brown et al. 1987; Stevens et al. 1997a), and CRE management attention 

is unlikely to influence their populations. 

Non-listed Extirpated or At-risk Taxa

Overview: Extirpated or at-risk species that are not federally listed make up the majority of 

those on the list in the CRE in post-dam time. The following list is not exhaustive, but represents 

a number of rare, endemic, or ecologically important taxa that have received little attention as 

being at-risk in the CRE. 

Plants: Although no plant species to our knowledge have been verified as extirpated from the 

CRE, the status of rare and declining wetland and riparian taxa is of concern to long-term 

ecological processes. Although extirpated from Grand Canyon, Yerba mansa (Anemopsis 

californica) only occurred in GRCA at Indian Gardens on Garden Creek, not in or near the CRE. 

Nonetheless, the diminished presence and importance of Goodding’s willow, Fremont 

cottonwood, coyote willow, honey mesquite, netleaf hackberry, and other plant species in the 
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CRE is of sufficient magnitude that loss of their respective ecological functions may limit 

associated faunal species and habitats. 

The persistence of Goodding’s willow trees (Salix gooddingii) in the CRE is unlikely

because bank-dwelling beavers (Castor canadensis) in the mainstream have removed most of the 

pre-dam trees (Mast and Waring1997, Mortenson et al. 2008), and no recruitment is occurring. A 

recent survey by Grand Canyon Wildlands Council, Inc. (2009) found that Goodding’s willow 

has been eliminated from 8 of 17 (47.1%) sites between Lees Ferry and Diamond Creek where 

the tree occurred prior to the closure of Glen Canyon Dam. At most sites, trees had been felled 

by beaver and continued beaver attack removed resprouting stems until the trees perished. 

Successful recruitment was not observed at any of those 17 sites, or elsewhere along the river 

during that and other vegetation surveys over the past three decades.

Fremont cottonwood (Populus fremontii) was relatively rare in the pre-dam CRE, but a 

large stand existed at Lees Ferry and the mouth of Bright Angel Creek, and a large individual 

tree existed near RM 193L in pre-dam time (Clover and Jotter 1944, Turner and Karpiscak 

1980). This species shares a similar fate with Goodding’s willow and cottonwood recruitment 

requirements are similar to those of the willow. Although cottonwood seedlings occasionally are 

detected along the river, establishment fails because, like Goodding’s willow, virtually all 

individuals are attacked by beaver. These Salicaceae are renowned as ecologically important 

species in southwestern rivers, diversifying canopy and subcanopy structure, and supporting high 

concentrations of neotropical migrant birds (e.g., Carothers et al. 1974). 

Although non-native tamarisk extensively colonized the lower riparian zone of the CRE 

immediately after dam closure, clonal coyote willow (Salix exigua) had become a co-dominant 

species by 1980 (Stevens 1985, 1989). In recent decades CRE coyote willow, like the other 

Salicaceae, has declined in response to intensive beaver attack, with every clone undergoing 

repeated harvest by beaver. Like Fremont cottonwood and Goodding’s willow, coyote willow 

supports more than 100 native herbivore and primary consumer taxa. Insect taxa, such as larval

viceroy butterfly (Limenitis archippus) are host specific on Salix exigua in the Southwest. The 

disappearance of viceroy butterflies from the CRE since 1982 reflects on-going reduction and 

disappearance of host plants along the river.

Honey mesquite (Prosopis glandulosa var. torreyana) is abundant on pre-dam terraces in 

from Mile 39 to 140 and from Mile 165 to Lake Mead, and makes up a large portion of the relict 

pre-dam riparian vegetation zone (Carothers et al. 1979, Anderson and Ruffner 1989; Waring et 

al. 2010). While this species is actively colonizing the lower riparian zone in post-dam time, no 

recruitment is occurring on on upper riparian terraces, where historically it was the dominant 

species (Waring et al. 2010). Two long-term issues about this pre-dam mesquite belt are the 

change in potential fire frequency driven by invasion of non-native Bromus grasses, and the 

potential for gradual replacement of mesquite by facultatively riparian catclaw (Fabaceae: 

Acacia greggii).

Netleaf hackberry (Celtis laevigata var. reticulata) also does not appear to be recruiting 

successfully in Grand Canyon. Individual stems of this clonal species in the CRE date back to 

1776 (Salzer et al. 1996); however, most existing clones appear to be decadent and few 

seedlings have been reported in post-dam time. Hackberry is remarkably tightly restricted to the 

pre-dam 2-year flood return stage (ca. 2,830 m3

/s) along the Colorado River, but unlike honey 

mesquite, it does not appear to be colonizing the lower riparian zone. Therefore, hackberry may 

warrant monitoring and determination of flow and habitat requirements for sustainable 

management. 
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Several other non-listed native plants are endemic in the CRE riparian zone, and more 

than 150 plant taxa are known from fewer than 4 records there, including many first-records for 

the state of Arizona (e.g., Ayers and Stevens 1994, Ayers et al. 1994). Other common riparian 

taxa in the upper Colorado River in Utah and Glen Canyon are rare in Grand Canyon. Absence 

of these plant taxa may reflect natural physiological or biogeographic limitations, or 

susceptibility to river flow and sediment management. 

Invertebrates: Several hundred of invertebrate taxa are rare but of unknown status in the CRE. 

Among these, several previously documented or reported insect species now are either extremely 

rare or may have been extirpated from the CRE, including: viceroy butterfly (Limenitis 

archippus; Garth 1950, L.E. Stevens unpublished data), dark buckeye (Junonia genoveva 

nigrosuffusa; L.E. Stevens unpublished data), and the recently described noctuid moth (Schinia 

immaculata Pogue 2004). Several endemic chironomid midges were collected along the 

Colorado River in the mid-1970s but have not subsequently been reported (Sublette et al. 1998), 

and several black fly and other nematoceran Diptera collected in the 1970s have not been found 

in the river corridor recent decades (Stevens, unpublished data). A single population of the

nepomorph waterbug, Belostoma nr. flumineum (Belostomatidae) exists in Vulcan’s Well Spring 

(179L; Stevens and Polhemus 2008). Niobrara ambersnail (Oxyloma h. haydeni) occur only at 

Leopard Frog Marsh (CR -9 L) Springs and at Indian Gardens on the Tonto Platform in Grand 

Canyon (Sorensen and Nelson 2003) and are the only documented extant populations of this 

genus in Arizona. The Niobrara ambersnail is identified as a Species of Greatest Conservation 

Need in Arizona’s SWAP (AGFD 2006). The only known population of the trematode snail 

parasite, Leucochloridium cyanocittae McIntosh 1932 in Arizona occurs in endangered Kanab 

ambersnail and Catinella nr. vermeta snails at Vaseys Paradise (Sorensen et al., unpublished 

data). 

Numerous endemic or extremely isolated insect populations are found adjacent to the 

CRE and particularly in the lower reaches of perennial springfed streams in Grand Canyon, but 

their status in the CRE remains unknown. Such species include masked clubskimmer (Odonata –

dragonflies, Brechmorhoga pertinax) and Grand Canyon wetsalts tiger beetle (Cicindela 

haemorrhagica arizonae), both of which occur in tributaries segments near the Colorado River 

from Nankoweap Creek (Mile 52R) downstream to Stone Creek (Mile 132R). The distribution 

and status of the Little Colorado River hairy-necked tiger beetle (Cicindela hirsuta coloradula), 

which is endemic to the riparian zone of lower Little Colorado River, have not been determined 

(Stevens and Huber 2004; Pearson et al. 2005). The only known U.S. population of the saldid 

waterbug, Micracanthia quadrimaculata occurs at and below the pre-dam 10 year flood stage at 

“Upper Bass Cable Springs” near Mile 108R (Stevens and Polhemus 2008). Similarly, endemic 

or isolated nepomorph water bugs (Hemiptera: Belostomatidae, Abedus breviceps in Boucher 

Creek and Ochteridae, Ochterus rotundus at low elevation desert springs in the middle reaches of 

Grand Canyon), and several chironomid midge taxa described by (Sublette et al. 1998), and the 

empidid Wiedemannia (Sinclair 2007) occur at individual springs or springfed desert springs 

along the Colorado River. A newly described asilid robber fly (Efferia tapeats Aubrey et al. in 

prep.) occurs on CRE sandbars and in adjacent tributary riparian zones in the middle reaches of 

Grand Canyon. Numerous other rare or undescribed invertebrate species exist in the CRE, but 

their distribution, status, and the potential impacts of dam operations on them remain unstudied.
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Vertebrates: Non-listed extirpated, seriously declining, or rare and apparently at-risk vertebrate 

species in the CRE include many species, of which several ecologically important taxa are 

described below.

1) The only population of CRE zebra-tailed lizard (ZTL; Callisaurus draconoides) was 

extirpated in 1983 when river-runner trucks conducting take-outs were redirected onto the upper 

sand dunes at Diamond Creek (Tompko 1976; Miller et al. 1981; Stevens et al. 2001, Brennan 

and Holycross 2005). ZTL still occur upstream in the Peach Springs Wash drainage, and a 

population could easily be reintroduced to the mouth of Diamond Creek. 

2) The western threadsnake (Leptotyphlops humilis) is known in the CRE from three records in 

the CRE and lower Little Colorado River (Stevens 1983, Brennan and Holycross 2005, D. Stone, 

FWS, unpublished data). All records of this species are from sand-dominated habitats in the 

riparian zone of the Colorado River and the lower Little Colorado River; however, its present 

status is unknown. Likewise, a single record of regal ring-necked snake (Diadophis punctatus 

regalis) exists from RM 194L by LES in 1978. The large, sandbar grassland in which it was 

detected was eliminated by mid-1980’s high flows. The status of several other rare CRE snake 

taxa also remains unknown. 

3) Muskrat (Ondatra zibithecus; Hoffmeister 1986; Stevens 1983; Stevens et al. 2001; NPS files) 

have been reported several times from the post-dam Colorado River corridor in Grand Canyon, 

and a skull was reported from Tapeats Creek in the 1990’s. Additional evidence of this species’ 

presence was detected after 2000 near Mile 77R. This is presently a rare species in the CRE, but 

muskrats have been detected recently at Lees Ferry and by GCMRC fisheries biologists as 

occasionally occurring in the lower Little Colorado River (Stone et al. 2008, 2010).

4) Southwestern river otter (SRO, Lontra canadensis sonora; Hoffmeister 1986; GCWC 2005; 

NPS files) is likely extinct in Grand Canyon. Although several reports of otter in the CRE exist 

from prior to 2000, repeated searches over 30 years have failed to document live individuals. If a 

resident population of SRO still exists, the introduction of extra-regional otter subspecies in 

upper Colorado River drainages and the Verde River is likely to eliminate the pure otter 

genotype through hybridization (Stevens et al. 2001). GCWC (2005) conducted an analysis of 

the potential for otter reintroduction into Grand Canyon to restore the missing ecological role of 

this top mammalian fish predator in the CRE; however, interagency concerns over potential 

impacts of otter on HBC have been raised and need to be resolved for restoration of the otter’s 

ecological role (GCWC 2005)..

5) Bank-dwelling American beaver (Castoridae: Castor canadensis) play an important role 

consuming and disturbing the CRE riparian zone vegetation (Mortenson et al. 2008). Beaver 

strongly affect establishment and survivorship of Salicaceae (e.g., Goodding’s willow and 

Fremont cottonwood) and other plant species along the river. Improved understanding of longterm beaver habitat availability, population dynamics, and distribution require additional

research and more consistent monitoring. 

6) Badger (Taxodea taxa) were last reported in the CRE in mid-winter 1990-1991 by National 

Park Service Biological Technician N. Kline at Hidden Sloughs (Colorado River Mile -6.5R; 
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Stevens unpublished data). Jacob Hamblin reportedly shot a badger near the mouth of Badger 

Creek (Colorado River Mile 8R) in the 1850’s (Wixom 1997). Similarly, the distribution and 

status of other carnivore populations is poorly known and not regularly monitored along the 

river, including: Procyonidae - ringtail (Basariscus astutus) and raccoon (Procyon lotor); 

Canidae - coyote (Canis latrans) and gray fox (Urocyon cinereoargeus); Mustellidae - spotted 

skunk (Spilogale gracilis), striped skunk (Mephitis mephitis), and hognosed skunk (Conepatus 

leuconotus); Felidae - bobcat (Lynx rufus) and mountain lion (Puma concolor); and Ursidae -

black bear (Ursus americanus). 

7) The nativity of painted turtle (Chrysemys picta) is uncertain in Arizona, but there are multiple 

observations of this species in the pre-dam Colorado River in Glen Canyon and near Lees Ferry. 

S. Johnson recalled collecting turtles from the mouth of the Paria River in the late 1920's (oral 

communication, LES files). Observations and movie footage of this species were made by T. 

Nichols in Glen Canyon in the 1950’s. Woodbury et al. (1959) reported several records of C. 

picta in Glen Canyon prior to the construction of Glen Canyon Dam. The species is now 

extremely rare in Arizona, and has been extirpated from the CRE. 

8) Gambel’s quail (Callipepla gambelii) were detected up until the early 1990’s along the lower 

CRE (Brown et al. 1987, L.E. Stevens unpublished field notes), but have not been reported 

recently. This species may have been introduced into the CRE, but more information is needed, 

as it was previously abundant along the western South Rim (Brown et al. 1987). Although 

common on the North Rim, wild turkey (Meleagris gallopavo) occasionally colonize the river 

corridor, but populations rarely persist more than 1-2 yr.

9) Numerous vagrant and accidentally occurring bird species have been detected in the CRE. At 

least 61 waterbird species in five guilds have been detected in the CRE: shorebirds, waders,

raptors, waterfowl, and kingfishers (Brown et al. 1987, Stevens et al. 1997, LaRue et al. 2001). 

Dam operations may affect waterbird populations directly (e.g., by forcing waterfowl and BAEA 

to shift their feeding strategies) or indirectly (e.g., stable flows may permit expansion of 

shoreline vegetation, increasing breeding habitat for mallards (Anas platyrhynos), but eliminating 

spotted sandpipers (Actitis macularia) breeding habitat – no breeding sandpipers have been

reported in recent decades in the CRE. Many waterbird species occur in migration and use the 

river corridor as wintering habitat. Protected as a migratory bird species, but not otherwise 

federally listed, white pelicans (Pelicanus erythrorhynchos) regularly pass through Grand 

Canyon during the migratory period (April and October; Stevens et al. 1997). Single individuals 

or small flocks are regularly reported, and flocks in excess of 200 birds have been sighted on the 

river (LaRue et al. 2001). Concern about range connectivity for this species may result in 

increased conservation attention in the future (e.g., Anderson and King 2005). Several waterbird 

species occur as vagrants or accidental species, including: 2 records of magnificent frigatebird

(Fregata magnificens), several records of trumpeter swan (Cygnus buccinator), a lone harlequin 

duck (Histrionicus histrionicus,seen between miles 49-52 in 2006-2007), and a single record of a 

snow goose (Chen caerulescens) observed at Lees Ferry in April 2011. Similarly, many rare 

terrestrial bird species occur as accidental or vagrant species in the CRE (e.g., painted bunting -

Passerina ciris; groove-billed ani - Crotophaga sulcirostris; scissor-tailed flycatcher – Tyrannus 

forficatus). We excluded these vagrant or accidental bird taxa from the analysis unless they were 

ESA- or specifically federally protected.
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10) Gila monster (Heloderma suspectum) are known from a very few detections in the lower 

CRE, primarily between Mile 202 to Diamond Creek on the left side of the river.

11) In the absence of monitoring, the impacts of dam operations on riverine amphibians may go 

undetected. For example, Rocky Mountain toad (Anaxyrus w. woodhousei ) diet, movement, 

reproduction success, and potential hybridization with other congeneric taxa (i.e., red-spotted 

toad, A. punctatus) may be affected by season, flow, and nearshore habitat availability, but the 

ecology of this species in relation to flow regulation has yet to be examined in the CRE.

CRE Species Rarity 

Three general patterns of rarity appear to exist among rare but unlisted species in the 

CRE. Relatively few species are unique to the CRE (Stevens and Polhemus 2008), although 

Grand Canyon endemic Flaveria macdougallii, Euphorbia arron-rossii, other endemic plant 

taxa, and several insect taxa occasionally occur along the river. Most endemic taxa in Grand 

Canyon appear to exist in springs or in harsh but evolutionarily persistent habitats (Phillips et al. 

1987). 

A more pronounced pattern of rarity involves propagules of headwaters species

transported via hydrochory or gravity into the CRE, become established, but are too rare or 

physiologically stressed to reproduce. These “waif” species include the following examples. 

Only 3 individuals of poison ivy (Anacardiaceae: Toxicodendron rydbergii) are known at CRE 

springs (32R, 136R, and 142R). A single individual of Asteraceae: Aster utahensis was detected 

at 123L in the middle riparian zone by M. Yeatts (Hopi Tribe, personal communication). Only a 

few individual of common dunebroom (Fabaceae: Pareyella fillifolia) exist in the CRE (Lees 

Ferry, RM 68R, RM 91R). Four individuals of Euphorbiaceae: Reverchonia arenaria were 

detected at Mile 142R by Ayers and Stevens (1994). Many other unlisted waif plant species are 

rare and known only from <3 collections in the CRE. The presence of Glen Canyon Dam likely 

limits downstream dispersal of waif propagules (e.g., Shafroth et al. 2002), and likely has 

interrupted long-term distributional processes that may reduce CRE riparian diversity. 

A third process is the upstream immigration into the CRE through anemochory or 

zoochory (wind or animal dispersal), and is more likely to occur in lower reaches of the river 

corridor. For example, the range of desert mistletoe (Phoradendron californicum) extends 

upriver as far as Mile 159R in catclaw. Scale-dependent dispersal (Aukema 2004) and the 

laxative properties of mistletoe berries (Willson and Travaset 1992) prevent Phainopepla 

(Phainopepla nitens), western bluebirds (Sialia mexicana) and other mistletoe seed dispersers 

from reaching the next Acacia upstream in the steep, narrow, sparsely vegetated Muav gorge. 

Similarly, whipple yucca (Liliaceae: Yucca whipplei), creosotebush (Larrea tridentata), ocotillo 

(Fouquieria splendens) and other Mohave Desert plant species have extended their ranges 

upstream as far the Muav Gorge, but have been blocked by the steep topography of that reach 

(Stevens and Polhemus 2008). In contrast, desert-broom (Baccharis sarothroides) likely 

colonized upriver via anemochory and has extended its range upstream through the CRE to the 

upper Muav Gorge. Its germination requirements involve unvegetated silty fine sand and moist 

soils after flooding (Stevens and Waring 1985), conditions which rarely exist in the 

contemporary CRE. Its continued expansion into the eastern basin of Grand Canyon is likely 

reduced by the coarser grainsize of the post-dam river corridor (Stevens 1989). Upstream 

colonization is generally slower than downstream or gravity-based waifing recruitment and non-
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native plant distribution, although both processes are important long-term biogeographic 

processes in the CRE riparian zone (Stevens and Waring 1985). 

Non-native Species

While the focus of this report is on native TMC, the diversity and ecological roles of nonnative taxa deserves mention. The total number of non-native taxa in the CRE likely exceeds 300 

species (Stevens and Ayers 2002). The list of non-native species is strongly dominated by more 

than 200 species of plants, several of which strongly preempt colonization space, increase fire 

frequency, and affect food resources and pollinator populations (e.g., Tamarix spp., Bromus

spp.). Several dozen non-native inverterate taxa have been detected in the CRE, including: 

important fish parasites (e.g., Asian tapeworm, Bothriocephalus acheilognathi; and anchorworm, 

Lernaea cyprinacea; Hoffnagle and Cole 1999); important food species for fish (e.g., Gammarus 

lacustris) and birds (e.g., tamarisk leafhopper, Opsius stactogalus); nursery escapees (e.g., Anatis 

lecontei ladybird beetles); nuisance species (e.g., New Zealand mudsnail, Potomopyrgus 

antipodarum; rock dove – Columba livia, European starling – Sternus vulgaris, and house 

sparrow- Passer domesticus); and non-native predators (e.g., Procambaruss crayfish and 

softshelled turtles in lowermost Grand Canyon. Pending invasions by other invertebrates, such as 

(Dreissena rostriformis bugensis) guagga mussel and Halyomorpha halys stinkbugs, may 

substantially alter CRE structure. Among CRE vertebrates, approximately 19 non-native fish 

species have been detected in the Colorado River in recent decades, with salmonids implicated in 

declines in native fish (Marsh and Douglas 1997; Yard et al. 2011). Feral burros were 

intentionally removed from the CRE by the NPS in 1982, but burros remain federally protected. 

 Non-native species, as well as several native populations that have proliferated in postdam time, strongly affect ecosystem form and function in the CRE. However, interactions among 

these species are complicated and require further study before restoration of native populations. 

Among several examples are the following:

1) Although non-native rainbow trout (RBT) removal around the Little Colorado River 

confluence coincided with stabilization of a declining HBC population, field data and 

modeling indicates that HBC recovery began prior to trout removal. In addition, the role 

of relatively warmer water during the same time period confound conclusions regarding 

the benefit of nonnative fish removal (Coggins 2008; Yard et al. 2011).

2) Translocation of HBC into Shinumo Creek (RM 109R) is being undertaken following 

attempts to remove non-native rainbow trout by electrofishing (GCWC 2008, NPS 2011); 

however, robust populations of native speckled dace (Rhinichthys osculus) and bluehead 

sucker (Catostomus discobolus) co-exist with RBT in that stream, indicating that in some 

settings, native and nonnative fish species coexist over long time periods. This topic 

merits additional research. 

3) Large Goodding’s willow trees commonly co-occur with non-native tamarisk, and the 

willow has largely been lost to beaver foraging (the beaver population in Grand Canyon 

is likely much larger than in pre-dam time; Mortenson et al. 2008). Therefore, successful 

restoration of Goodding’s willow stands requires both the elimination of spacepreempting nonnative plant species as well as protection of plantings from beaver attack.

4) SWFL and other native neotropical migrant birds in the CRE preferentially nest in nonnative tamarisk (Brown and Trossett 1989), a common phenomenon throughout Arizona, 

and SWFL decline has been related to native brown-headed cowbird brood parasitism. To 
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22

what extent does SWFL restoration require maintenance of suitable vegetation stands 

from which cowbirds are excluded?

5) The upstream movement of non-native crayfish (Procambarus clarkii) from Lake Mead, 

the potential for downstream dispersal from Glen Canyon and headwater tributaries south 

of Grand Canyon, and the potential for accidental or deliberate introduction into the CRE 

poses a serious threat to Grand Canyon’s 50 or so perennial tributaries. These are some of 

the only remaining largely pristine streams in western North America, and are among the 

only streams in Arizona not invaded by crayfish. As important natural laboratories and 

sentinel sites for understanding stream-riparian ecosystem ecology and restoration, these 

streams should be rigorously protected from crayfish invasion.

6) On-going invasion of Dreissena mussels into the lower Colorado River basin almost 

certainly will be followed by invasion into upper basin streams and reservoirs. The 

impacts of this mussel on the CRE and Grand Canyon tributaries are unknown, but may 

strongly affect river ecosystem structure and function (Nalepa 2010).

7) Conflicting reports exist over the ecological significance of New Zealand mudsnail 

(NZM) in the CRE. Cross et al. (2010) reported no impact of NZM on the CRE foodbase, 

while Melis et al. (2010) and Rosi-Marshall et al. (2010) simultaneously reported 

extensive impacts of NZM on the CRE foodbase.

8) Tamarisk leaf-beetles (Diorhabda spp.) are presently defoliating tamarisk stands 

throughout the CRE. Despite the recent closure of the beetle release program, this nonnative beetle species is well established upstream of Colorado River, and is presently 

erupting in the CRE. Diorhabda invasion may greatly negatively influence river corridor 

bird habitat and populations, as most of the two dozen neotropical migrant bird species in 

Grand Canyon nest commonly or preferentially in tamarisk. The NPS is actively 

monitoring this developing situation which, next to the completion of Glen Canyon Dam, 

is likely to be the largest anthropogenic change to the CRE in recent history.

Trophic Status of TMC

The CRE encompasses clear water to usually turbid reaches (Fig. 1) through a complex 

suite of wide or narrow reaches, and TMC populations are variously distributed through those 

reaches across time and in response to flow regimes (Schmidt and Graf 1990; Schmidt et al. 

1998; Walters et al. 2000; Stevens and Polhemus 2008). We mapped the trophic status of 

extirpated and at-risk TMC in the CRE, demonstrating that focal TMC (i.e., HBC, KAS, and 

SWFL) occupy lower and middle trophic positions (Fig. 2). While those focal species occupy 

selected aquatic, wetland, and riparian habitats, respectively, they may not provide adequate 

protection for most other CRE TMC and ecological processes. Therefore, the usefulness of this

small group of endangered species for understanding and managing the full array of ecosystem 

dynamics is limited (Stevens et al. 2001). Two groups of species in the CRE terrestrial domain 

have not received sufficient monitoring or conceptual modeling attention: top riparian predators,

and rare or endemic taxa, including insects. Additional monitoring data are needed on such 

species to develop a more robust aquatic-terrestrial conceptual ecosystem model for the CRE, 

and such an effort will likely better serve long-term CRE management. 
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Fig. 2: The Colorado River ecosystem, depicting four major trophic levels affected by the dam 

and physical environmental factors, through the geomorphic reaches of the river and over time. 

The trophic relationships of selected taxa of management concern are depicted as circles (see 

Appendix A for abbreviations). Most management attention in the CRE has been focused on 

HBC, KAS, and SWWL (large circles), but other endangered (red text), threatened (blue text), 

and non-federally listed rare taxa (black text) are ecologically important in the CRE and may be 

at risk of extirpation.

THE REINTRODUCTION PROCESS 

Reintroduction Justification, Planning, Compliance, and Implementation

Restoration of TMC consistent with NPS and other stewardship agency reintroduction 

policies has heretofore been regarded as a tertiary priority in the CRE, behind improving the 

population health of federally listed species, and sediment management. Thus, questions of 

whether, how and when to restore at-risk or extirpated endangered or non-listed species remain 

unaddressed, but require prioritization. Unfortunately, major information gaps exist with regards 

to the distribution and present status of many TMC in the CRE. For example, the importance and 

phenological timing of imprinting on spawning habitat stream waters among young native fishes 

remains an important but largely unaddressed issue that is highly relevant to fish translocation 

Aquatic vegetation Riparian vegetation Uplands vegetation

Climate, Geomorphology, Solar radiation, Dam, Tributary Effects

Aquatic 1o consumers Riparian 1o consumers Upland 1o consumers

Aquatic 2o consumers Riparian 2o consumers Upland 2o consumers

Aquatic 3o consumers Riparian 3o consumers Upland 3o consumers

1o decomposers

2o decomposers

3o decomposers

Glen Canyon Reach

Upper Lake Mead Reach

Lower Canyon Reach

Marble Canyon Reach

Permian Reach

Furnace Flats Reach

Time 2

Time X

SIMPLIFIED CONCEPTUAL MODEL OF THE COLORADO RIVER ECOSYSTEM,

SHOWING THE TROPHIC POSITION OF EXTIRPATED AN LISTED FAUNA

Isles

Lower Granite Gorge

Lower Cyn Reach

Muav Gorge

S+R

RBS

RTC BTC

CPM

SWWF YBCU ZTL

CRO

MR VBF

Bdgr PRFA CACO

WBS

KAS

NLF RLF

HBC

BAEA PEFA SpS

SNPL

KEY: 

Fed. endangered

Fed or AZ threatened

Not listed

Active mgt

Passive mgt

Formerly listed

Up. Gran. Grg.

Isles Reach

Time 1

BobC

GAQU
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and reintroduction efforts. Also, the issue of range restoration for native fish remains outstanding. For example, a large concentration of HBC occurred at the mouth of the Paria River at 

the time of dam construction (Minckley 1973), but HBC have since disappeared from that reach, 

and little attention to range restoration of HBC has been entertained by the AMWG to date. Such 

information and discussion may play an important role in the planning and implementation of 

population reintroduction and restoration actions.

Reintroduction of extirpated CRE species requires several phases of effort, including: a) 

development of the administrative context; b) compiling relevant information, stock assessment, 

and prioritization, c) plan development, d) multi-agency compliance, e) implementation,

potentially with multiple stocking efforts, and f) monitoring and feedback. 

a) Administrative oversight for reintroduction can be complex. The NPS has direct oversight of 

natural and cultural resource management of the CRE, as it carries out NPS statutorily-based 

actions in behalf of the Secretary of the Interior (U.S. Department of the Interior 2006:45). 

However, several agencies also have oversight for CRE fish and wildlife management. . Other 

agencies/entities that advise and assist the NPS on management of Grand Canyon plant and 

wildlife species include: individual NPS units; the FWS, AGFD; several Native American Indian 

tribes; the Bureau of Reclamation; the U.S. Geological Survey; the State of Arizona; and various 

other cooperating stakeholders in the Glen Canyon Dam AMWG. Each of these entities has its 

own mission, and differences in management focus are the norm, making reintroduction of some 

extirpated species more difficult. The first step in a reintroduction program is to have clearly 

defined interagency agreement on the effort and clear identification of funding; however, while 

the administrative context for reintroduction of extirpated species is explicit in the policies of the 

NPS and in AMWG Goal 3, reintroduction actions remain administratively challenging. For 

example, reintroduction of razorback sucker into the CRE is regarded as the easiest and most 

justifiable action, but discussions of this topic began before 1989 and continue to the present day 

without any action. Administratively successful examples include translocation of KAS into 

Royal Arch Creek and HBC into Shinumo Creek (NPS 2011).

b) The second step in CRE reintroduction projects involves compilation of sufficient information 

on the ecology, life history, diseases and parasites, status of remaining populations as potential 

stock, reasons for extirpation, trophic role(s), relationships to other species, and other 

information to support reintroduction efforts. . This information needs to be evaluated in a matrix 

approach to allow the CRE managing agencies to clearly justify and prioritize reintroduction 

efforts, including where and when reintroduction efforts should be conducted. The action 

prioritization process should include consideration of all aspects of reintroduction, including: 

legal and managerial justification, funding, stock availability and genetic issues, potential socioecosystem impacts, , reintroduction logistics, treatment for diseases and parasites, risks and 

contingency planning, monitoring protocols and schedules, reporting, feedback related to 

improvement of techniques, public relations, and administrative accounting. Clear definiation of 

such issues are critical to NPS and other resource-managing agency’s decisions regarding 

reintroduction or rehabilitation of TMC. 

c) Development of a reintroduction, translocation, or population augmentation plan is based on 

the findings in (b) above. The plan should include all aspects of the reintroduction process, 

including detailed stock assessment to guarantee, to the greatest extent possible, that the 
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reintroduced stock is the most fit and genetically the most capable of surviving the translocation 

process and proliferating in the renewed landscape. Parasite treatment may be required, as the 

stock to be translocated should be parasite-free. Also, it is important to determine the level of 

population take that an existing native species can withstand and still remain functional. The plan 

must be regarded as a living document, as it will require continued updating as challenges are 

discovered in the initial phases of the effort. The plan will require agreement by the cooperating 

agencies.

d) Compliance requirements for species translocation, augmentation, or reintroduction differ and 

overlap to various extents among the several stakeholders with wildlife management 

responsibilities in the CRE. NPS compliance requirements for such activities include attention to 

autecological (stock source), synecological, cultural, other tribal, recreational, natural quiet, and 

other resource impacts, in accordance with National Environmental Policy Act and the Code of 

Federal Regulations (24.4.5i.i, 24.6.a.2). FWS reintroduction requirements involve consideration 

of Section 7 of the 1973 ESA and other obligations. Wildlife reintroduction actions by the AGFD 

involve a 12-step reintroduction process (AGFD 1987) and Arizona Game and Fish Commission 

approval. All wildlife stewardship agencies generally have interacted in proposing and 

accomplishing previous translocation, augmentation, or reintroduction projects in the region 

(e.g., KAS, California condor, HBC). 

DISCUSSION

Ecosystem management requires adequate understanding of the ecological role and 

potential for restoration of extant as well as extirpated species and processes. Understanding the 

feasibility and advisability of restoration of extirpated species is mandated through Goal 3 of the 

AMWG mission, and also is mandated by the wildlife managing agency stakeholders, most 

notably the NPS, FWS, and AGFD, and several Native American Tribes. Filling information 

gaps about missing or declining species is needed to more fully inform the Secretary about Glen 

Canyon Dam impacts, as well as providing information for the compliance requirements of 

AMWG cooperating agencies needed to foster reintroduction efforts. Through its multistakeholder structure, AMWG is uniquely poised to recommend to the Secretary of the Interior 

the technical, interagency, and societal information needs and processes through which to 

achieve the purposes of AMWG’s Goal 3. However, there is at present no commitment that the 

AMP will fund species restoration efforts, as such activities are the specific purview of the 

resource managing agencies. Nonetheless, the AMWG can play an important and beneficial 

multi-agency advisory role to the Secretary in evaluating TMC restoration priorities and potential 

in the CRE, and AMWG may benefit from monitoring information on reintroduced or 

translocated TMC.

The responsibility of the AMWG is to advise the Secretary of the Interior on the

environmental and economic impacts of Glen Canyon Dam operations, and the potential to 

mitigate impacts within the context of existing law. Our analysis here addresses a motion from 

AMWG in relation to Goal 3 of the AMP to compile information on the restoration needs and 

potential for missing and at-risk native species in the CRE. We provide previously uncompiled 

background information, and an assessment approaches to prioritize TMC reintroduction

potential. We offer this information as guidance to the AMWG, recognizing the diverse views 

among AMWG stakeholders as to the AMP’s responsibilities regarding CRE management. Our 

primary objective here has been to present information on the status and priorities for 
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26

management of rare and declining CRE species to better help AMWG manage the river corridor 

as an ecosystem. 

Two administrative issues emerged from this analysis that previously have not been 

discussed by the AMWG. First, many TMC were recognized from the CRE that may warrant 

management attention, if not by the AMWG, then by other managing agencies. A total of 47 (54 

percent) of the 85 TMC considered in here had potential restoration scores > 50 percent (Table 

2; Appendix A). Also, many species with scores <50 percent lacked critical information on 

distribution, habitat use, or population status. There appears to be considerable opportunity for 

improving the quality of basic information on TMC. 

Second, AMWG monitoring recommendations currently focus primarily on HBC, as well 

as flow and sediment transport, with minor attention to KAS. However, at least 5 species (1 

plant, 1 lizard, and 3 non-listed fish) scored higher than HBC in our analysis. Concern for the 3 

non-listed CRE fish arose from the desire of the Committee to prevent those species from 

becoming federally endangered. The zebra-tailed lizard scored above HBC because it would be 

such an inexpensive and easily-accomplished restoration action. AMWG may choose to engage 

in further discussion of the restoration potential of these TMC, and we hope that the information 

provided here contributes to those discussions and to improved stewardship of the CRE.

ACKNOWLEDGEMENTS

The members of the Goal 3 Ad Hoc Committee included: L.E. Stevens (GCWC, Chair); 

Jeff Sorensen and Bill Steward (AGFD); Shaula Hedwall, Sam Spiller, and Pam Sponholtz 

(FWS); Ted Melis, Bill Persons, and David Ward (GCMRC); Mike Yeatts (Hopi Tribe); Todd 

Chaudhry, Brian Healy, Martha Hahn, and Melissa Trammell (NPS); Marianne Crawford 

(Reclamation); and Shane Capron (Western). We thank the ad hoc committee members and the 

following taxon experts for their efforts scoring the species: L. Makarik and R.V. Ward (NPSGrand Canyon); Carol Chambers, Neil Cobb, Tad Theimer (Northern Arizona University, 

Flagstaff); and Richard Bailowitz and R. Roy Johnson of Tucson. Bill Persons and Melissa 

Trammel provided valuable comments on early versions of this manuscript. We kindly thank Ms. 

Linda Whetton (Reclamation) for her tireless administrative support of these proceedings. L.E. 

Stevens efforts on this project were partially supported by the Annenburg Foundation. 

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APPENDIX A:

TAXA OF MANAGEMENT CONCERN IN THE CRE,

SCORING SHEETS, ALTERNATIVE APPROACHES,

AND COMMENTS BY EXPERTS

(Provided in electronic Excel format only)