1 

Glen Canyon Dam Technical Work Group 

Agenda Item Information 

June 22-23, 2009

Agenda Item

Comprehensive Plan for the Management and Conservation of Humpback Chub (Gila cypha) in the 

Lower Colorado River Basin 

Action Requested

 Review the draft document and consider forwarding it to AMWG for their review. 

 Proposed Motion: 

The TWG accepts the HBC Comprehensive Plan and forwards it to AMWG for review, 

comment, and consideration for transmission to its Implementation Plan Ad Hoc Group. 

Presenter

Shane Capron, TWG Chair 

Humpback Chub Comprehensive ad hoc 

Documents

AIF Humpback Chub Comprehensive Plan 

Draft June 16, 2009 Humpback Chub Comprehensive Plan 

Science Advisor Comments on draft plan 

HBC ad hoc response to Science Advisor comments 

Background Information

In 2003, in response to a continuing decline in the Grand Canyon population of humpback chub 

(GCMRC 2003a), the AMWG began a process to identify a comprehensive approach to the 

management of humpback chub in Grand Canyon. The specific charge was to “consider actions to 

implement a comprehensive research and management program for the humpback chub” (motion 

passed January 28, 2003). This charge resulted in the Status and Management Strategy for 

Humpback Chub in Grand Canyon (Humpback Chub Ad Hoc Committee 2003). In subsequent 

review of the Plan, the AMWG determined that there are management needs for humpback chub 

that are within the scope of the adaptive management program, as well as management needs 

outside the scope of the program which will require alternative funding sources for implementation 

(i.e. actions needed for recovery). This focus is clear in the AMWG motion that directed the 

preparation of this document (motion passed on March 3, 2005; see minutes of February 2-3, 2005 

TWG and March 3-4, 2005 AMWG meetings): 

The AMWG directs the TWG to further develop the humpback chub comprehensive plan, 

as follows: 

1. Describe linkages, sequences, and feedback loops among projects. 

2. Identify priorities and a timeline for completion of each action within the comprehensive 

plan. 
2 

3. Spell out specific steps and criteria for any actions that would be needed if a crisis occurs 

(e.g., severe population decline). 

4. Continue to include active participation by GCMRC staff and any additional expertise. 

5. Incorporate comments from the Science Advisors. The TWG will include a response to 

comments document in their final draft. 

The AMWG also directs the creation of a humpback chub implementation plan Ad Hoc 

Group. This Ad Hoc Group will: 

1. Determine which actions identified in the humpback chub comprehensive plan can be 

accomplished under the AMP. 

2. Explore the various options for completing actions that do not fall under the authorities 

of the AMP. 

To complete this charge, the TWG formed the Humpback Chub Comprehensive Plan Ad Hoc 

Group (Ad Hoc) to revise the Plan, and the AMWG formed the Humpback Chub Implementation 

Ad Hoc Group to determine which aspects of the Plan would be carried out by the AMP.2 The Ad 

Hoc interpreted these charges to mean that the Plan should include all aspects necessary to 

accomplish recovery of the lower basin recovery unit because the AMWG specifically asked for 

actions that are both within, and outside, the scope of the AMP. 

The purpose and scope of the plan is to compile information on the status of the Grand Canyon 

population of humpback chub (i.e. lower basin recovery unit as defined by the U.S. Fish and Wildlife 

Service), summarize the threats to this population, and define a comprehensive strategy, which 

includes specific research and management actions, to improve the status of the population and 

minimize or eliminate threats. The Plan also responds to the AMWG charge to describe linkages, 

sequences, and feedback loops among projects, identify priorities and a timeline for completion of 

actions, and determine steps and criteria for actions needed in a crisis (e.g., severe population 

decline). 
DRAFT 

Comprehensive Plan for the Management and Conservation of 

Humpback Chub (Gila cypha) in the Lower Colorado River Basin 

Prepared by 

The Glen Canyon Dam Adaptive Management Program 

Technical Work Group 

Humpback Chub Comprehensive Plan Ad Hoc Group 

June 16, 2009 

ABSTRACT 

 Humpback chub in Grand Canyon1

 remain threatened by habitat alteration due to the 

presence and operation of Glen Canyon Dam, presence of nonnative competitors, predators, and 

parasites, and the threat of stochastic events. The Glen Canyon Dam Adaptive Management 

Program (AMP) created this Comprehensive Plan for the Management and Conservation of 

Humpback Chub in the Lower Colorado River Basin (Plan) to provide a comprehensive list of 

actions designed to better understand and ameliorate these threats to assist in recovery of the 

humpback chub. The primary actions thought to ameliorate these threats include but may not be 

limited to habitat improvement in the mainstem Colorado River to improve its capability for 

spawning and rearing of humpback chub, especially via increased water temperatures, either 

through modified releases from Glen Canyon Dam or modification of the dam itself via a 

selective withdraw structure and related infrastructure; control and removal of nonnative fish; the 

use of translocation to increase the range of spawning and rearing of humpback chub in Grand 

Canyon; the creation of offsite refuge populations of humpback chub to guard against stochastic 

event-driven catastrophic loss; and planning documents to guide long-term threat abatement. 

PREFACE 

The Glen Canyon Dam Adaptive Management Program is a unique program developed to 

provide an organization and process for cooperative integration of dam operations, downstream 

resource protection and management, and monitoring and research information, as well as to 

improve the values for which the Glen Canyon National Recreation Area and Grand Canyon 

National Park were established. Adaptive management is a dynamic process where people of 

many talents and disciplines come together to develop recommendations in the interest of 

resource improvement using a structured, iterative process of optimal decision making in the face 

of uncertainty, with an aim to reduce uncertainty over time via system monitoring (Holling 

1978,Walters 1986). The AMP evolved from various laws and legislation, including the Law of 

the River (numerous laws and compacts that adjudicate the Colorado River), the Grand Canyon 

 

1

 In this document, references to Grand Canyon include the geographic areas of both Marble and Grand canyons, 

unless otherwise specified. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 2

Protection Act, the Endangered Species Act, the National Environmental Policy Act, and the 

National Historic Preservation Act. In 1989, the Secretary of the Interior directed an 

Environmental Impact Statement (EIS) be prepared regarding the operation of Glen Canyon Dam 

by the Bureau of Reclamation. The Final EIS was completed in March 1995. Findings from the 

EIS indicated that many uncertainties still exist regarding the downstream impacts of water 

releases from Glen Canyon Dam on significant resources, including water, sediment, fish, 

vegetation, wildlife and habitat, endangered and other special status species, cultural resources, 

air quality, recreation, hydropower, and non-use values. The endangered humpback chub was, 

and continues to be, a primary resource of concern. 

In compliance with the Grand Canyon Protection Act, the EIS proposed utilizing the 

process of adaptive management whereby the effects of dam operations on downstream 

resources would be monitored, assessed, and managed. The EIS also recommended formation of 

a Federal Advisory Committee in order to comply with the consultation requirement in Section 

1805 of the Grand Canyon Protection Act. In January 1997, Interior Secretary Babbitt signed a 

Notice of Establishment for this Federal Advisory Committee, naming it the Glen Canyon 

Adaptive Management Work Group (AMWG). The Charter of this group was signed on January 

15, 1997. 

The AMP consists of a diverse group of stakeholders, including state and federal 

agencies, water users, customers who purchase federal power, environmental groups, recreation 

interests, and American Indian tribes, that directs coordinated scientific studies conducted by the 

Grand Canyon Monitoring and Research Center (GCMRC) of the U.S. Geological Survey 

(USGS). The AMWG provides the opportunity for public involvement in the decision-making 

process and includes those stakeholders with interest in the operation of Glen Canyon Dam and 

downstream resources. The Adaptive Management Program is administered through a senior 

Department of the Interior official, the “Secretary’s designee,” who also acts as chair of the 

AMWG. Three other groups serve to advise the AMWG; the Technical Work Group (TWG) as 

a subgroup to work on technical tasks charged to them by the AMWG; the GCMRC, a USGS 

science center tasked specifically with administering science directed at AMP needs; and 

independent advisory panels, contracted groups of scientists tasked with reviewing the products 

of the AMP program. Together, these bodies form the AMP, advising the Secretary of the 

Interior, through an adaptive management framework, on management of Glen Canyon Dam. 

Because the AMP is made up of federal and state agencies, tribes, and private groups, many of 

these entities have authorities and responsibilities for AMP resources. These authorities are 

presented in detail in the AMP Strategic Plan (2002). 

1.0 INTRODUCTION 

1.1 Background 

 The humpback chub (Gila cypha) is a large cyprinid fish endemic to the Colorado River 

Basin (Miller 1946) that attains a maximum size of about 480 mm total length (TL) and 1.2 kg in 

weight (Valdez and Ryel 1997). The humpback chub is currently listed as “endangered” under 

the Endangered Species Act of 1973, as amended (ESA; 16 U.S.C. 1531 et. seq.). Critical 

habitat was published on March 21, 1994 (U.S. Fish and Wildlife Service 1994). The latest 

revised humpback chub recovery plan was approved on September 19, 1990 (U.S. Fish and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 3

Wildlife Service 1990). Recovery goals for humpback chub were completed in 2002 (U.S. Fish 

and Wildlife Service 2002), and draft revised goals completed in 2008 (U.S. Fish and Wildlife 

Service 2008). 

The decline of the humpback chub throughout its range and continued threats to its 

existence are due to habitat modification and streamflow regulation (including cold-water dam 

releases and habitat loss, described further in relation to Glen Canyon Dam below), competition 

with and predation by nonnative fish species, parasitism, hybridization, and pollutants (U.S. Fish 

and Wildlife Service 2002). Dams and associated streamflow regulation, in general, alters flows 

and temperatures that may be needed for spawning and successful recruitment (Muth et al. 

2000), but also may reduce the availability of habitats created by fine sediment such as 

backwaters which may be important to native fish (U.S. Geological Survey 2007, 2008a). This 

loss of habitat is exacerbated by predation and competition from nonnative fishes (Minckley 

1991, Marsh and Douglas 1997, Valdez and Ryel 1997, Chart and Lentsch 2000, Pilger et al. 

2008). Parasitism, (especially by nonnative Asian tapeworm Bothriocephalus acheilognathi), 

hybridization with other native Gila, and pesticides and pollutants are also factors in the decline 

(U.S. Fish and Wildlife Service 2002). 

 The recovery goals define two recovery units: the upper Colorado River basin, and the 

lower Colorado River basin (divided at Glen Canyon Dam, Arizona; U.S. Fish and Wildlife 

Service 2008). Recovery criteria were developed for each of the two recovery units (i.e., the 

upper basin, including the Green River and upper Colorado River subbasins; and the lower basin, 

including the mainstem and its tributaries from Glen Canyon Dam downstream to Lake Mead 

National Recreation Area), to address unique threats and site-specific management actions 

necessary to minimize or remove those threats. The recovery units encompass three 

management areas under different and separate recovery or conservation programs (i.e., Upper 

Colorado River Recovery Program, the AMP, and Lower Colorado River Multi-Species 

Conservation Program; see section 1.3 for description of geographic coverage by each of the 

programs). The lower Colorado River basin recovery unit consists of all of the aggregations of 

humpback chub in Marble and Grand canyons (see Section 2.2 below). This Plan was developed 

for conservation of the lower Colorado River basin recovery unit. 

 A U.S. District Court ruling on January 18, 2006, set aside the recovery goals, essentially 

because they lacked time and cost estimates for recovery. The court did not fault the recovery 

goals as deficient in any other respect, thus the Fish and Wildlife Service and the AMP continue 

to utilize the underlying science in the recovery goals, including in the development of this Plan. 

As part of the review and revision of the goals, the U. S. Fish and Wildlife Service will analyze 

time and cost estimates for recovery, and will provide this information in an updated version of 

the recovery goals. A draft revision was completed and made available by the U.S. Fish and 

Wildlife Service in 2008; this version will be further revised based on comments received for a 

final version. 

 In 1995, the Fish and Wildlife Service completed a jeopardy biological opinion on the 

operation of Glen Canyon Dam. The biological opinion concluded that the Modified Low 

Fluctuating Flow Alternative, the preferred alternative in the Bureau of Reclamation’s EIS on the 

Operation of Glen Canyon Dam (Bureau of Reclamation 1995), was likely to jeopardize the 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 4

continued existence of the humpback chub and razorback sucker (Xyrauchen texanus), and was 

likely to destroy or adversely modify designated critical habitat. The biological opinion included 

a Reasonable and Prudent Alternative with four elements: 1) Development of an adaptive 

management program that implements research and management actions to attain river 

conditions that support all life stages of endangered and native fish species; 2) Development of a 

management plan for the Little Colorado River; 3) Development of a management plan for 

razorback sucker in Grand Canyon; and 4) Establishment of a second spawning aggregation of 

humpback chub in Grand Canyon (U.S. Fish and Wildlife Service 1995). 

As explained in the preface, the AMP is a conservation program that was established by 

the Secretary of the Interior under the Federal Advisory Committee Act in 1996 to provide 

oversight on the operation of Glen Canyon Dam to protect and/or enhance development of the 

Colorado River ecosystem through Grand Canyon. The AMP defined goals for target resources 

in its Strategic Plan (AMP 2001) including humpback chub. The AMP goal for humpback chub 

is to maintain or attain viable populations, remove jeopardy and prevent adverse modification to 

humpback chub critical habitat. As stated, the goals of the AMP focus on meeting the 

requirements of the 1995 jeopardy biological opinion, which is limited to minimizing and 

removing the threats from operation of Glen Canyon Dam. The AMP goals do not specifically 

address the need to recover the species because program members have determined that recovery 

of humpback chub is beyond the scope of the program. 

In 2003, in response to a continuing decline in the Grand Canyon population of 

humpback chub (GCMRC 2003a), the AMWG began a process to identify a comprehensive 

approach to the management of humpback chub in Grand Canyon. The specific charge was to 

“consider actions to implement a comprehensive research and management program for the 

humpback chub” (motion passed January 28, 2003). This charge resulted in the Status and 

Management Strategy for Humpback Chub in Grand Canyon (Humpback Chub Ad Hoc 

Committee 2003). In subsequent review of the Plan, the AMWG determined that there are 

management needs for humpback chub that are within the scope of the adaptive management 

program, as well as management needs outside the scope of the program which will require 

alternative funding sources for implementation (i.e. actions needed for recovery). This focus is 

clear in the AMWG motion that directed the preparation of this document (motion passed on 

March 3, 2005; see minutes of February 2-3, 2005 TWG and March 3-4, 2005 AMWG 

meetings): 

The AMWG directs the TWG to further develop the humpback chub comprehensive plan, as 

follows: 

1. Describe linkages, sequences, and feedback loops among projects. 

2. Identify priorities and a timeline for completion of each action within the 

comprehensive plan. 

3. Spell out specific steps and criteria for any actions that would be needed if a crisis 

occurs (e.g., severe population decline). 

4. Continue to include active participation by GCMRC staff and any additional expertise. 

5. Incorporate comments from the Science Advisors. The TWG will include a response 

to comments document in their final draft. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 5

The AMWG also directs the creation of a humpback chub implementation plan Ad Hoc 

Group. This Ad Hoc Group will: 

1. Determine which actions identified in the humpback chub comprehensive plan can be 

accomplished under the AMP. 

2. Explore the various options for completing actions that do not fall under the authorities 

of the AMP. 

To complete this charge, the TWG formed the Humpback Chub Comprehensive Plan Ad 

Hoc Group (Ad Hoc) to revise the Plan, and the AMWG formed the Humpback Chub 

Implementation Ad Hoc Group to determine which aspects of the Plan would be carried out by 

the AMP.2

 The Ad Hoc interpreted these charges to mean that the Plan should include all 

aspects necessary to accomplish recovery of the lower basin recovery unit because the AMWG 

specifically asked for actions that are both within, and outside, the scope of the AMP. 

In 2007, the Secretary of the Interior responded to an AMWG recommendation to 

develop a Lower Colorado River Fish Recovery Implementation Program. The Secretary 

recognized that recovery of the humpback chub in the lower basin exceeded the limited authority 

and role of the AMP. The Secretary further directed that the Fish and Wildlife Service take the 

lead in developing a recovery implementation program for the humpback chub population in 

Grand Canyon (i.e. the lower basin recovery unit). The Ad Hoc anticipates that this recovery 

implementation program will develop separate documents to recover the lower basin recovery 

unit of humpback chub, and will assimilate resources to implement actions that are beyond the 

scope of the AMP. 

In December 2007, the U.S. Fish and Wildlife Service issued a biological opinion on the 

proposed adoption of Colorado River Interim Guidelines for Lower Basin Shortages and 

Coordinated Operations for Lake Powell and Lake Mead (Interim Guidelines) (U.S. Fish and 

Wildlife Service 2007). With respect to Glen Canyon Dam, the guidelines essentially broadened 

the range of possible annual release volumes. The biological opinion concluded that 

implementation of the Interim Guidelines, including a set of conservation measures, was not 

likely to jeopardize the continued existence of the humpback chub, and was not likely to destroy 

or adversely modify designated critical habitat. 

In February 2008, the U.S. Fish and Wildlife Service issued a new biological opinion on 

the operation of Glen Canyon Dam that replaced the 1995 jeopardy biological opinion. The 

biological opinion concluded that a five year program including a 2008 High Flow Test, 

Modified Low Fluctuating Flows with Steady Flows in September and October, and a set of 

conservation measures, was not likely to jeopardize the continued existence of the humpback 

chub, and was not likely to destroy or adversely modify designated critical habitat. The 

conservation measures included elements of the Plan, including: implementation of the Plan, 

humpback chub translocation, nonnative fish control, a humpback chub nearshore ecology study, 

maintenance of humpback chub refuges, and Little Colorado River watershed planning. A list of 

 

2

 The TWG had passed a motion proposing to complete the Plan if directed by the AMWG in February 2005. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 6

these conservation measures, as well as conservation measures from the biological opinion on 

the Shortage Criteria, are provided in Appendix F. 

On May 26, 2009, the District Court of Arizona found in favor of the Grand Canyon 

Trust with respect to their complaint that the 2008 Biological Opinion was in violation of the 

Endangered Species Act. The court remanded that section of the biological opinion assessing the 

effects of the Modified Low Fluctuating Flow (MLFF), and specifically, effects of the MLFF on 

humpback chub, its critical habitat, and its recovery. The remanded portion of the biological 

opinion is ordered to be revised by October 30, 2008. 

The AMP defined goal for humpback chub (AMP 2001) is to maintain or attain viable 

populations, remove jeopardy and prevent adverse modification to humpback chub critical 

habitat. As stated, the goals of the adaptive management plan focus on meeting the requirements 

of the 1995 jeopardy biological opinion, which is limited to minimizing and removing the threats 

from operation of Glen Canyon Dam. Although the AMP goals do not specifically address the 

need to recover the species, and program members have determined that recovery of humpback 

chub is beyond the scope of the program in its current form, there is no preclusion to evaluate 

actions to recover the species, or to implement actions that assist in recovery of the species. 

1.2 Purpose and Scope 

The purpose and scope of this Plan is to compile information on the status of the Grand 

Canyon population of humpback chub (i.e. lower basin recovery unit as defined by the U.S. Fish 

and Wildlife Service), summarize the threats to this population, and define a comprehensive 

strategy, which includes specific research and management actions, to improve the status of the 

population and minimize or eliminate threats. The Plan also responds to the AMWG charge to 

describe linkages, sequences, and feedback loops among projects, identify priorities and a 

timeline for completion of actions, and determine steps and criteria for actions needed in a crisis 

(e.g., severe population decline). 

The Plan relies upon the Humpback Chub (Gila cypha) Recovery Goals (U.S. Fish and 

Wildlife Service 2002, 2008) and other available information and knowledge, and was developed 

by and for the Glen Canyon Dam Adaptive Management Program. The Plan should be used to 

identify needs that can be met by the Adaptive Management Program, as well as those that are 

outside the scope of the program and thus require additional resources. The Ad Hoc believes 

that, used in this way, the Plan will help guide the efforts of the new recovery implementation 

effort. 

The Ad Hoc recognizes that although this Plan is specifically directed at one species, the 

humpback chub, other native fish species within the Colorado River ecosystem will benefit from 

the actions recommended here. These include the endangered razorback sucker (a rare species 

that is considered extirpated in Grand Canyon but is found in limited numbers downstream in 

areas of Lake Mead), speckled dace (Rhinichthys osculus), bluehead sucker (Catostomus 

discobolus), and the flannelmouth sucker (Catostomus latipinnis). The flannelmouth and 

bluehead suckers are considered special status species by all of the Colorado River basin states in 

which they occur, and are the subjects, in part, of both a range-wide and an Arizona state-wide 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 7

conservation agreement (Arizona Game and Fish Department 2006a). Goal 2 of the AMP, as 

defined in the AMP Strategic Plan, is to“[m]aintain or attain viable populations of existing native 

fish, remove jeopardy for humpback chub and razorback sucker, and prevent adverse 

modification to their critical habitat.” These other native fishes should also benefit from many of 

the recommendations and projects in this Plan. 

1.3 Recovery or Conservation Programs 

The Glen Canyon Dam Adaptive Management Program (AMP). The AMP is a conservation 

program that was established by the Secretary of the Interior in 1996 following the Record of 

Decision on the Environmental Impact Statement assessing operation of Glen Canyon Dam (U.S. 

Department of the Interior 1995). The AMWG is a federal advisory committee that provides 

recommendations to the Secretary of the Interior regarding operation of Glen Canyon Dam and 

other measures to protect and/or enhance the Colorado River ecosystem through Grand Canyon, 

defined geographically as the mainstem Colorado River and its tributaries from Glen Canyon 

Dam downstream to Grand Wash Cliffs, River Mile (RM) 276.5. The AMP addresses elements 

of the EIS on the operation of Glen Canyon Dam and requirements of U.S. Fish and Wildlife 

biological opinions for the humpback chub and razorback sucker (U.S. Fish and Wildlife Service 

2007, 2008). The AMP considers findings of the GCMRC and a group of Science Advisors 

during development of recommendations regarding dam operations, management actions and 

conservation of the endangered fishes. 

Upper Colorado River Endangered Fish Recovery Program: The Upper Colorado River 

Endangered Fish Recovery Implementation Program (UCRIP) is a recovery program that was 

initiated under a Cooperative Agreement signed by the Secretary of the Interior on January 22, 

1988, as a coordinated effort of State and Federal agencies, water users, customers who purchase 

federal power, and environmental groups, to recover four endangered fishes in the upper basin 

downstream to the inflow of Lake Powell, excluding the San Juan River (U.S. Fish and Wildlife 

Service 1987, Wydoski and Hamill 1991, Evans 1993). It functions under the general principles 

of adaptive management and consists of the following seven program elements: instream flow 

protection; habitat restoration; reduction of nonnative fish and sportfish impacts; propagation and 

genetics management, research, monitoring, and data management; information and education; 

and program management. As stated in its governing document (U.S. Fish and Wildlife Service 

1987), the program goal is to recover the endangered fishes while allowing water development to 

proceed in compliance with state and federal laws, including the Endangered Species Act (ESA), 

state water laws, interstate compacts, the Law of the River and federal trust responsibilities to 

Native American tribes. Funding for the UCRIP will continue through 2013 (soon to be 2023) 

under extension of the cooperative agreement (signed December 6, 2001) pursuant to the 

authorizing legislation passed in October 2000 (P.L. 106-392). 

Recovery Implementation Plan Scientific Workgroup: In 1999, the U.S. Fish and Wildlife 

Service Region 2 convened a group of biologists, formally named the Scientific Workgroup, to 

develop a Recovery Implementation Plan for the endangered native fishes of the Lower Colorado 

River Basin from Glen Canyon Dam to the Gulf of California (Mexico). Primary emphasis was 

to be placed on recovery of bonytail, humpback chub, Colorado pikeminnow, and razorback 

sucker. The workgroup met regularly initially but then less frequently in subsequent years and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 8

completed a final management plan for the Lower Colorado River Basin (U.S. Fish and Wildlife 

Service 2005) as its final product. The plan identifies Grand Canyon as a geographic recovery 

subunit for humpback chub and provides downlisting and delisting criteria equivalent to those 

identified in the Recovery Goals (U.S. Fish and Wildlife Service 2002). 

Lower Colorado River Multi-Species Conservation Program: The Lower Colorado River 

Multi-Species Conservation Program (MSCP) was established in response to environmental 

compliance needs of water and power entities in Arizona, California and Nevada. The program 

is intended to remove jeopardy and work toward recovery of listed species, including the 

razorback sucker, bonytail, and humpback chub, while accommodating current water diversions 

and power production. In return, member stakeholders are seeking incidental take authorization 

under the ESA from the U.S. Fish and Wildlife Service to allow for implementation of covered 

activities and conservation measures over the next 50 years. The MSCP planning area 

encompasses the Colorado River from the Lake Mead full pool elevation of 1229 feet to the 

Southerly International Boundary with Mexico. At this elevation, the inflow area of the 

Colorado River is influenced by the reservoir as far upstream as Separation Rapids (RM 239.5). 

These rapids are about 37 river miles upstream of Grand Wash Cliffs (RM 276.5), the western 

boundary of the AMP, and so a geographic overlap exists between the programs. This overlap 

has been recognized by the MSCP in a commitment to support the AMP for humpback chub as 

follows: “Provide $10,000/year for 50 years (total: $500,000) to the Glen Canyon Dam Adaptive 

Management Workgroup to support implementation of planned, but unfunded, species 

conservation measures and, as appropriate, to fund species conservation measures in the lower 

canyon of the Colorado River upstream of Lake Mead.” In 2007, the U.S. Fish and Wildlife 

Service completed a biological opinion on the Colorado River Interim Guidelines for Lower 

Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead (U.S. Fish and 

Wildlife Service 2007), which included, as a conservation measure, creation and maintenance of 

an off-site refuge population of humpback chub, to be funded by Reclamation by providing 

expedited advancement of $200,000 in funding to the U.S. Fish and Wildlife Service from the 

$500,000 commitment for the species by the MSCP. 

Lower Colorado River Recovery Implementation Program: In 2007, the Secretary of the 

Interior responded to an AMWG recommendation to develop a Lower Colorado River Fish 

Recovery Implementation Program. The Secretary recognized that recovery of the humpback 

chub in the lower basin exceeded the limited authority and role of the AMP. The Secretary 

further directed that the U.S. Fish and Wildlife Service take the lead in developing a recovery 

implementation program for the humpback chub population in Grand Canyon (i.e. the lower 

basin recovery unit). The Ad Hoc anticipates that this recovery implementation program will 

develop a plan to recover the lower basin recovery unit of humpback chub, and will assimilate 

resources to implement actions that are beyond the scope of the AMP. 

2.0 STATUS OF HUMPBACK CHUB IN THE COLORADO RIVER BASIN 

2.1 Status of Humpback Chub Populations in the Upper Colorado River Basin 

 There are five populations of humpback chub located above Glen Canyon Dam in the 

Upper Colorado River Basin. These populations include three in the Colorado River, at Cataract 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 9

Canyon, Utah, Black Rocks, Colorado, and Westwater Canyon, Utah; one in the Green River in 

Desolation and Grey canyons in Utah, and one in the Yampa and Green Rivers in Dinosaur 

National Monument. Population estimates for humpback chub using mark-recapture estimators 

began in 1998 with the Black Rocks and Westwater Canyon populations, and were conducted 

during 1998-2000 and 2003-2005. These estimates show the Black Rocks population between 

about 1,000 and 2,000 adults (age 4+) and the Westwater Canyon population between about 

1,700 and 5,100 adults (McAda 2002, 2004, 2006, Hudson and Jackson 2003a, 2003b, Jackson 

2004a, 2004b). Population estimates for Desolation/Gray Canyon in 2001-2003 show the 

population between about 1,000 and 2,600 adults (Jackson and Hudson 2005). The Cataract 

Canyon and Yampa Canyon populations were recently estimated at about 100 and 400 adults, 

respectively (Valdez and Badame 2005, Finney 2006). 

2.2 Status of Humpback Chub in the Lower Colorado River Basin 

 Humpback chub in the lower Colorado River basin below Glen Canyon Dam occur in the 

Colorado River in Marble and Grand canyons, and in the lower 18 km (11 miles) of the Little 

Colorado River, constituting the Grand Canyon population, which also represents the lower basin 

recovery unit (U.S. Fish and Wildlife Service 2002). Critical habitat in Arizona includes most of 

the habitat now used by the Grand Canyon population of humpback chub. Designated reaches 

are the lower 8 miles (12.9 km) of the Little Colorado River and from RM 34 (Nautiloid Canyon) 

to RM 208 (Granite Park) along the Colorado River. This represents approximately 28 percent 

of the historical habitat for the species, and 48 percent of critical habitat. The dominant factors 

affecting critical habitat in Grand Canyon are habitat alteration due to the presence and operation 

of Glen Canyon Dam and the presence of nonnative fish that prey on and compete with native 

fishes. The known constituent elements of critical habitat are present and functional throughout 

designated critical habitat in the action area, primarily in the Little Colorado River; the mainstem 

Colorado River may provide all constituent elements, but at times appears too cold or has too 

many nonnative fishes to fully function. 

Historically, humpback chub were likely distributed throughout Grand Canyon, with 

local concentrations, although there is little information to gauge historical abundance. Valdez 

and Ryel (1995) estimate that the range of humpback chub in Grand Canyon has declined by 

about 61 miles or 24 percent since Glen Canyon Dam was completed, based on historical 

captures of humpback chub from the dam site to Separation Canyon (RM 241), and current 

capture locations from South Canyon (RM 30.0) to Separation Canyon (RM 239.5). 

Mark-recapture methods have been used since the late 1980s to assess trend in adult 

abundance and recruitment of the Little Colorado River aggregation of humpback chub. These 

estimates indicate that adult population declined through the 1980s and early 1990s but has been 

increasing for the past decade (Coggins et al. 2003, Coggins 2006, 2007, Coggins and Walters 

2008). Coggins (2007) summarized information on abundance and analyzed monitoring data 

collected since the late 1980s and found that the adult population had declined from about 8,900-

9,800 in 1989 to a low of about 4,500-5,700 in 2001. Current methods for assessment of 

humpback chub abundance rely on the Age-Structured Mark-Recapture model (ASMR). The 

ASMR has limited capability to provide abundance estimates because of the uncertainty 

associated with assigning an age to an individual fish based on its length. Coggins and Walters 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 10

(2009) however conclude that “considering a range of assumed natural mortality-rates and 

magnitude of ageing error, it is unlikely that there are currently less than 6,000 adults or more 

than 10,000 adults” and estimate the current adult (age 4 years or more) population is 

approximately 7,650 fish. Coggins and Walters (2009) caution however that, because of the 

variance in the model, “we suggest that the most robust finding in this report is the increasing 

trend in adult abundance, and that there is considerably more uncertainty about the 2008 absolute 

adult abundance estimate.” 

 The sampling program for the Little Colorado River aggregation of humpback chub also 

results in a second set of population estimates for the humpback chub in the Little Colorado 

River only. These efforts are designed to be directly comparable to prior studies of humpback 

chub abundance in the early 1990s (Douglas and Marsh 1996). Two pass mark-recapture 

surveys are conducted in the spring and fall each year. Abundance estimates are derived using 

the Chapman Petersen closed model. These estimates show a similar pattern to the ASMR. 

Abundance declined from the 1996 level, but has recently increased dramatically. The 2007 

spring estimate for humpback chub greater than 150 mm total length in the Little Colorado River 

was 5,124 (CI 4,295-5,953); the closed population estimate of April 1992 was 5,555 (CI 4,416-

7,067). Closed population estimates thus also indicate recent increases in adult abundance (Van 

Haverbeke and Stone 2008). 

The improvement in the status of the Little Colorado River aggregation of humpback 

chub appears due to an increase in recruitment, which was particularly high in the 2003-4 period 

(Coggins and Walters 2009). Interestingly, recruitment began to improve in the mid-1990s, prior 

to warmer mainstem water temperatures (due to drought and low Lake Powell levels), efforts to 

mechanically remove nonnative fishes, and translocation. Although the 2000 low summer steady 

flow (that resulted in warmer mainstem water temperatures) could have benefitted the brood 

years as early as 1998, recruitment appears to have increased prior to this flow experiment 

(Coggins and Wlaters 2009). No explanations for this recruitment increase have been proposed 

to date. The increase could have been due to factors associated with the Little Colorado River, 

the mainchannel Colorado River (the switch to MLFF flows for example), or from changes in 

both rivers. 

The Grand Canyon population consists primarily of adults residing in and near the Little 

Colorado River, with much smaller aggregations of the species scattered throughout 

approximately 180 river miles of the mainstem Colorado River. Valdez and Ryel (1995) 

identified nine mainstem aggregations of humpback chub in Grand Canyon: 30 mile (RM 29.8 to 

31.3); Little Colorado River Inflow (RM 57.0-65.4); Lava to Hance (RM 65.7-76.3); Bright 

Angel Creek Inflow (RM 83.8-93.2); Shinumo Creek Inflow (RM 108.1-108.6); Stephen Aisle 

(RM 114.9-120.1); Middle Granite Gorge (RM 126.1-129.0); Havasu Creek Inflow (RM 155.8-

156.7); and Pumpkin Spring (RM 212.5-213.2). Monitoring continues to confirm the persistence 

of these aggregations (Trammell et al. 2002), although few or no humpback chub have been 

caught at the Havasu Inflow and Pumpkin Spring aggregations since 2000 (Ackerman 2007). 

Humpback chub have been caught infrequently downstream of Pumpkin Spring. One adult was 

captured downstream of Maxson Canyon (RM 244) in 1994 (Valdez 1994), and four humpback 

chub were caught at Separation Canyon (RM 239.5) in 2006 (Arizona Game and Fish 

Department 2006b). The Little Colorado River Inflow is the largest aggregation, which is in the 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 11

lower 13 km of the Little Colorado River and the adjoining 15 km of the Colorado River (RM 

57.0-65.4). This aggregation has been expanded upstream of Chute Falls through mechanical 

translocation of fish (Stone 2007). The contribution of mainstem aggregations, other than the 

Little Colorado River Inflow aggregation, to the overall Grand Canyon population are not 

known. 

New information also shows greater numbers of young humpback chub in the mainstem 

than in previous years. Catch-rate indices indicate increases in numbers of sub-adult humpback 

chub (150-199 mm TL [5.91-7.83 in]; Coggins 2007). During 2002-2006, a total of 442 

humpback chub <100 mm (3.94 in) TL were captured upstream of the Little Colorado River 

Inflow (RM 61.3) as far upstream as RM 30.7 (Ackerman 2007). Of the 442 fish, 225 (13-66 

mm [0.51-2.60 TL) were caught between RM 30 and RM 50. The 30-Mile aggregation is 

located 31 miles upstream of the Little Colorado River inflow and it is unlikely that the young 

humpback chub swam upstream that distance, especially given cool mainstem temperatures. 

Furthermore, the distribution of these fish, as well as average size above (mean = 38 mm [1.50 

in] TL) and below the Little Colorado River (mean = 67 mm [2.64 in] TL), indicate that the natal 

source is upstream of RM 50 and not from the Little Colorado River. The causes for these recent 

increases in young humpback chub in the mainstem Colorado River are uncertain, but declines in 

nonnative trout over this period as well as warmer river temperatures due to low reservoir levels 

in Lake Powell, have been implicated. 

Young-of-year and juvenile humpback chub observed outside the Little Colorado River 

aggregation were most abundant at RM 110-130 (Stephen Aisle and Middle Granite Gorge 

aggregations) during 2000 and 2004 and RM 160-200 during 2000 (Johnstone and Lauretta 

2004, 2007, Trammell et al. 2002, Arizona Game and Fish Department 1996, Ackerman 2007). 

Seine catches of all young-of-year humpback chub outside the nine aggregations were at their 

highest in 21 years during 2004 (Johnstone and Lauretta 2007). Four humpback chub were also 

collected at Separation Canyon (RM 239.5) in 2005 (Ackerman et al. 2006). The Middle Granite 

Gorge aggregation (which includes adults) has been stable or increasing in size since 1993 

(Trammell et al. 2002) and may be sustained via immigration from the Little Colorado River 

aggregation, as well as local reproduction. No humpback chub have been caught at the Havasu 

Inflow and Pumpkin Spring aggregations since 2000 (Ackerman 2007). Valdez and Ryel (1995) 

provided mark-recapture estimates for PIT-tagged humpback chub adults (≥200 mm [7.87 in] 

TL) in five of the remaining eight aggregations, including 30-Mile (estimate, n-hat = 52), 

Shinumo Inflow (n-hat = 57), Middle Granite Gorge (n-hat = 98), Havasu Inflow (n-hat = 13), 

and Pumpkin Spring (n-hat = 5). Population estimates have not been made for other mainstem 

aggregations since 1993 (Trammell et al. 2002). 

Translocations may have increased the range and size of the Little Colorado River Inflow 

aggregation. In August 2003, nearly 300 young humpback chub were translocated above a 

natural barrier, Chute Falls, in the Little Colorado River approximately 16 km above the 

confluence. This translocation was followed by another translocation of 300 fish in July 2004, 

and 567 fish in July 2005 (Stone 2006). Results indicate that translocated fish had high survival 

and growth rates. Reproduction above Chute Falls and downstream movement below Chute 

Falls has also been documented (Stone 2006). An additional 299 juvenile humpback chub were 

translocated in July 2008. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 12

Douglas and Douglas (2007) provided a thorough analysis of the genetic structure of 

humpback chub, examining all extant populations including the nine aggregations in Marble and 

Grand Canyon. They concluded that genetic differences among the Marble and Grand canyon 

aggregations of humpback chub were difficult to distinguish at the microsatellite level. 

Aggregations appeared to be connected by geneflow, suggesting downstream drift of larvae and 

juveniles as a likely mechanism. Aggregations were relatively homogeneous when compared to 

each other. They also found that the Grand Canyon population (the nine aggregations considered 

as a group), is markedly distinct from upper basin populations based on microsatellites, although 

there was no differentiation between the upper and lower basins in the mitochondrial DNA 

analysis. On the basis of these results, Douglas and Douglas (2007) recommended the 

aggregations in Marble and Grand canyons be treated as a single management unit. They also 

found that the Grand Canyon population (the nine aggregations considered as a group), is 

markedly distinct from upper basin populations based on microsatellite DNA analysis, although 

there was no differentiation between the upper and lower basins in the mitochondrial DNA 

analysis. On the basis of these results, Douglas and Douglas (2007) recommended the 

aggregations in Marble and Grand canyons be treated as a single management unit, and that both 

the upper and lower basins be considered as a single species. 

Although Douglas and Douglas (2007) concluded that the Little Colorado River 

population appeared to be the primary source aggregation in the Grand Canyon population, they 

found that contribution from occasional local reproduction by mainstem aggregates could not be 

excluded. They found two individuals in the 30-mile aggregation in Marble Canyon with G. 

elegans haplotypes, and the microsatellite profile for this population was intermediate between 

genotypes found in Desolation Canyon (a hypothesized hybrid population) and Grand Canyon. 

Although reproduction has been documented for the 30-mile aggregation, it appears to have very 

low numbers of fish. As the only population in Grand Canyon that is upstream from the Little 

Colorado River, it is least likely to receive migrants from downstream locations such as the Little 

Colorado River aggregation. Nevertheless, although Douglas and Douglas (2007) recommended 

further study of the 30-mile aggregation to evaluate the potential distinctiveness of these fish, 

they concluded that the entire Grand Canyon population should be considered a single 

management unit. This is consistent with the 2002 and draft 2008 Humpback Chub Recovery 

Goals which consider the Grand Canyon population a single and separate recovery unit (U.S. 

Fish and Wildlife Service 2002). 

 

3.0 THREATS TO HUMPBACK CHUB IN GRAND CANYON 

3.1 Baseline Condition for Humpback Chub in the Lower Colorado River Basin 

The decline of humpback chub in Grand Canyon has long been thought to be due 

primarily to emplacement of Glen Canyon Dam. The predam river was a highly variable 

ecosystem. Flow varied greatly between seasons, from peak flood flows in May or June with a 

median monthly discharge of about 50,000 cubic feet per second (cfs), to low flows in January 

with a median monthly discharge of about 5,000 cfs. Flood flows of over 120,000 cfs were 

relatively common, occurring about every six years, and low flows of 500-1,000 cfs were also 

common. Daily variation in discharge was relatively small, with a median of about 542 cfs 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 13

(Topping et al. 2003). A turbid and sediment-laden stream much of the year, the river was nearly 

clear at low flows (Blinn and Cole 1990). Temperatures varied from about 0 to 30°C (32 to 

86°F)(Korn and Vernieu 1998). Minckley (1991) suggested that food base for fishes was likely 

meager due to the high turbidities seasonally present and the scouring nature of the river, 

although allochthonous inputs, much reduced post dam, may have provided a significant source 

of macroinvertebrates as well as nutrients for autochthonous production (Minckley and Rinne 

1985, Haden et al. 1999). The fish fauna was notably already dominated by nonnative carp and 

catfish which may have depressed native fish populations at the time of dam construction 

(McDonald and Dotson 1960). 

In contrast, the post-dam river is a more stable environment in all ways except for daily 

variation in discharge. The river now is limited by the 1996 ROD to discharges between 5,000 

and 25,000 cfs (with the exception of high flow tests which may be up to 45,000 cfs), and a 

maximum daily fluctuation of 8,000 cfs (U.S. Bureau of Reclamation 1996). Releases from Glen 

Canyon Dam are varied throughout the day to meet the demand for electricity. The post-dam 

median daily change in discharge (8,580 cfs) is now approximately 15 times greater than predam (542 cfs) and actually exceeds the pre-dam median discharge (7,980 cfs; Topping et al. 

2003). Post-dam changes in discharge created dramatic changes in diurnal river stage, up to 2 

meters (m, 6.6 ft) in some areas; pre-dam, diurnal stage change was seldom more than 0.3 m (1.0 

ft) (GCMRC unpublished data). The river is now perennially cold, although warmer in the 

winter than predam (Voichick and Wright 2007). Glen Canyon Dam releases hypolimnetic 

water (the deeper layer of the reservoir) with a relatively constant temperature which typically 

ranges from 8-10 °C at high reservoir levels (46-50 °F; GCMRC unpublished data), although 

releases from 2004-2006 were much warmer due to low Lake Powell reservoir levels. Post-dam 

productivity is much higher in terms of algal and invertebrate biomass, thus food availability for 

fishes is likely greater than pre-dam (Blinn and Cole 1991). Turbidity is almost nil, 

approximately 84-94 percent of the fine sediment input is now trapped behind the dam, and the 

post-dam median discharge of 12,600 cfs causes remaining fine sediment to be lost continually 

(Topping et al. 2000, Topping et al. 2003, Wright et al. 2005). 

Much of the Grand Canyon population of humpback chub, and the majority of all 

spawning, occurs in the lower 16 km (10 miles) of the Little Colorado River (Valdez and Ryel 

1995; Paukert et al. 2006). The Little Colorado River appears to be little changed hydrologically 

from pre-Anglo settlement times, and is similar in some respects to the pre-dam Colorado River. 

Flow ranges from a median low discharge of about 200 cfs in June to a median high discharge in 

April of about 600 cfs. When at low or base flow, this travertine system is relatively clear and 

turquoise blue in color. During floods, the Little Colorado River carries large sediment loads 

and is extremely turbid. Water temperatures range from near freezing to about 25°C (77°F; 

Voichick and Wright 2007). At low flow, the Little Colorado River at Cameron is dry, with flow 

in the lower river supplied entirely by Blue Springs, about 20 km (12.5) miles upstream from the 

confluence. Blue Spring is warm spring, with a constant outflow temperature of 22.6°C (Mattes 

1993). The seasonally-warm water temperatures in the Little Colorado River provide near 

optimal spawning and rearing habitat for humpback chub. 

Many of the physical changes in the post-dam Colorado River are believed to have 

contributed to eliminating spawning and recruitment of humpback chub in the mainstem river. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 14

Humpback chub require a minimum of about 16°C (60°F) for successful spawning, hatching and 

rearing of young fish (Hamman 1982; Marsh 1985; Clarkson and Childs 2000; Muth et al. 2000). 

Bulkley et al. (1982) found that young humpback chub 73-134 mm (2.9-5.28 in) TL forced to 

swim at a velocity of 0.51 m/sec fatigued after an average of 85 minutes at 20°C, (68°F) but 

fatigued after only 2 minutes at 14°C (57°F); a decrease of 6°C (11°F) reduced fatigue time by 

98 percent. From the time that Lake Powell first filled in about 1980 until about 2000, cold 

hypolimnetic releases of 8-10°C (46-50°F; GCMRC unpublished data) were characteristic of 

Glen Canyon Dam operations. These cold temperatures largely prevented mainstem 

reproduction by humpback chub, except perhaps in localized warm springs (Valdez and Masslich 

1999). Throughout this post-dam period, low survival of larval and post-larval fish led to low 

recruitment to the adult population. This trend was attributed to effects of cold water 

temperatures (thermal shock, and poor swimming performance and predator avoidance) and 

nonnative fish predators and competitors (Lupher and Clarkson 1994, Valdez and Ryel 1995, 

Marsh and Douglas 1997, Clarkson and Childs 2000 Robinson and Childs 2001, Ward et al. 

2002). Because cold temperatures can also cause larvae and juvenile fish to experience thermal 

shock (Berry 1988), and swimming ability is greatly reduced (Berry and Pimentel 1985, Ward 

and Bonar 2003), juvenile humpback chub exiting the warm Little Colorado River and entering 

the cold mainstem may be too lethargic to effectively avoid predation or swim to suitable 

nearshore habitats (Valdez and Ryel 1995, Robinson et al. 1998). 

Although Glen Canyon Dam releases have been relatively constant at 8-10 °C (46-50 °F; 

GCMRC unpublished data) since Lake Powell filled, they are influenced by lake elevation, 

inflow hydrology, release volumes and meteorological conditions. Release temperatures have 

varied from 7 to 16 °C (45-60 °F) from 2000 through 2006. Between 1999 and 2005, Lake 

Powell elevations dropped more than 140 feet as a result of a basin-wide drought. Glen Canyon 

Dam release temperatures increased to 16 °C (60 °F) in the fall of 2005. The drop in Lake 

Powell elevation (e.g. level) resulted in warmer releases because the epilimnion was closer to the 

penstock withdrawal zone. Release temperatures from Glen Canyon Dam during 2004 and 2005 

were the highest since August 1971 when the reservoir was filling. Since 2005, reservoir levels 

have increased resulting in cooler release temperatures. Releases are predicted to remain cool to 

cold for the next 5-10 years (i.e. there is a 75 percent chance that reservoir levels will remain 

above 3,600 ft and corresponding release temperatures will be <11 °C (51.8 °F) from 2009-

2013)(U.S. Bureau of Reclamation 2007). 

The ongoing drought and corresponding low reservoir levels and warm-water releases in 

2004-2006 illustrate the potential for climate change to impact humpback chub. Some authors 

have indicated that this drought is the beginning of a shift to a more arid climate in the American 

Southwest (Seager et al. 2007, USCCSP 2008). The Fourth Assessment Report (Summary for 

Policymakers) of the Intergovernmental Panel on Climate Change (IPCC 2007) presented a 

selection of key findings regarding projected changes in precipitation and other climate variables 

as a result of a range of unmitigated climate changes projected over the next century. Although 

annual average river runoff and water availability are projected to decrease by 10-30 percent 

over some dry regions at mid-latitudes, information with regard to potential impacts on specific 

river basins was not included. Recently published projections of potential reductions in natural 

flow on the Colorado River Basin by the mid-21st century range from approximately 45 percent 

by Hoerling and Eischeid (2006) to approximately 6 percent by Christensen and Lettenmaier 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 15

(2006). If predicted effects of climate change result in persistent drought conditions in the 

Colorado River basin similar to those seen in recent years, warm-water conditions below Glen 

Canyon Dam may become the norm rather than the exception. 

Fluctuations also influence water temperatures in the mainstem river. Temperature 

differences between mainchannel and nearshore habitats can be especially pronounced in 

backwaters and other low velocity areas. But the amount of warming that occurs in backwaters 

is affected by daily fluctuations, which cause mixing with cold mainchannel waters (Arizona 

Game and Fish Department 1996). Hoffnagle (1996) found that mean, minimum, and maximum 

temperatures of backwaters were higher under steady versus daily fluctuating flows, with mean 

daily temperatures (14.5 °C [58.1 °F]) under steady flows about 2.5 °C (4.5 °F) greater than 

those under fluctuating flows. Differences in the mainchannel temperatures during steady and 

fluctuating flows were also statistically significant, but mean temperatures differed by only 0.5 

°C (0.9 °F). Similar results were documented by Trammell et al. (2002), who found backwater 

temperatures during the 2000 low steady summer flow experiment to be 2-4 °C (3.6-7.2 °F) 

above those during 1991-1994 under fluctuating flows. Korman et al. (2006) also found warmer 

backwater temperatures under steady flow conditions, concluding that backwaters were cooler 

during fluctuations because of the daily influx of cold main channel water. Vegetation, talus, and 

debris fan shorelines appear to be important nearshore habitats for juvenile humpback chub 

(Converse et al. 1998). The relative importance is poorly understood and subject of current 

study (the nearshore ecology study, Project 8 of this plan). 

Korman et al. (2006) also noted that nearshore areas affected by fluctuating flows (i.e., in 

the varial zone) warmed substantially for brief periods each day, which posits an ecological 

trade-off for fish utilizing these areas. On the one hand, fish may choose to exploit the warmer 

temperatures of the fluctuating zone on a daily basis and simply sustain any bioenergetic 

disadvantages of acclimating to rapidly changing discharge; or they may choose to remain in the 

permanently wetted zone which is always wetted, but colder than the immediate nearshore 

margin. In addition to increasing energy demands to fish that must move out of backwaters due 

to fluctuating flows, there is also an increased vulnerability to predation (Korman et al. 2004). 

As discussed above, Glen Canyon Dam caused reductions in sediment supply, because 

Glen Canyon Dam and Lake Powell trap most of the sediment transported by the Colorado 

River. This has likely altered the number and quality of nearshore habitats that may be important 

for small bodied fishes such as juvenile humpback chub. Tributaries downstream of the dam are 

now the only renewable sediment source to Glen, Marble, and Grand canyons. The dam and 

reservoir have also reduced annual flood peaks and increased moderate flows. The altered flow 

releases from the dam have less capacity to transport sand and coarser sized sediments than 

under pre-dam conditions with frequent floods (U.S Geological Survey 2007). How these 

changes have effected rearing of juvenile humpback chub is not well understood. An ongoing 

study (Project 8, the nearshore ecology study) to investigate the ecology of nearshore aquatic 

habitats will help to better understand how sediment influences nearshore habitat and how fish 

utilize these habitats. 

The high flow tests of 1996 and 2004 were found effective at building or rebuilding 

sandbars, although persistence of the sandbars is variable. Preliminary results appear similar for 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 16

the 2008 high flow test. The 1996 beach/habitat-building flow deposited more sandbars and at a 

faster rate than predicted (Webb et al. 1999). Repeat topographic and hydrographic mapping of 

33 sandbar-eddy complexes showed that the 1996 beach/habitat-building flow rebuilt previously 

eroded high-elevation sandbars, regardless of location, bar type, or canyon width (Hazel et al. 

1999). More than half of the sand deposited at higher elevations was taken from the lower 

portions of the sandbars (Schmidt 1999) rather than being derived from tributary sand supplies 

accumulated on the channel bed, as originally hypothesized in the 1995 EIS (Wright et al. 2005). 

Over time, however, this resulted in a net decrease in total eddy-sandbar area and volume 

(Topping et al. 2004); many sandbars built during the 1996 high flow test eroded in as little as 

several days following the experiment. 

In contrast to the 1996 high flow test, the 2004 high flow test was strategically timed to 

take advantage of highly sediment-enriched conditions (U.S. Geological Survey 2007a). 

Suspended sediment concentrations during the 2004 experiment were 60 to 240 percent of those 

measured during the 1996 experiment, although there was less sand in suspension below RM 42 

(Topping et al. 2004). This resulted in creation of larger sandbars than those observed during the 

1996 experiment in Marble Canyon, but area and volume of sandbars downstream of RM 42 

actually decreased due to comparatively less sand in that area in 2004 than in 1996. Thus, it was 

clear from results of the 2004 high flow test that high flows conducted under sediment-depleted 

conditions (such as 1996) cannot be used to sustain sandbar area and volume (Topping et al. 

2004); additionally, it became evident that more sand would be needed during future high flow 

tests to restore sandbars throughout Marble and upper Grand canyons. 

In 2007, sand inputs from the Paria River were at least 2.5 million metric tons, or about 

2.5 times the historical average (U.S. Geological Survey 2007). Together with inputs from the 

Little Colorado River in 2006 and unexpected retention of sediment from both tributaries during 

2006, sand inputs were at least 3 times the amount that triggered the 2004 high flow test, and 

greater than since at least 1998 (U.S. Geological Survey 2007). This presented a unique 

opportunity to evaluate effects of a high flow test under sand-enriched conditions greater than 

ever tested before. The 2008 high flow test initially resulted in beach and bar building similar to 

results seen in the 2004 test, although positive results were spread throughout the canyon, as 

opposed to the 2004 test which resulted in bar building primarily in upper Marble Canyon 

(GCMRC, unpublished data). 

Backwaters are thought to be important rearing habitat for fish due to low water velocity, 

warm water and high levels of biological productivity (Hoffnagle 1996, Goeking et al. 2003). 

They are created as water velocity in eddy return channels decline to near zero with falling river 

discharge, leaving an area of stagnant water surrounded on three sides by sand deposits and open 

to the mainchannel environment on the fourth side (Rubin et al. 1990). Reattachment sandbars 

are the primary geomorphic features that function to isolate nearshore habitats from the cold, 

high velocity mainchannel environment. 

Backwater numbers vary spatially among geomorphic reaches in Grand Canyon and tend 

to occur in greatest number in river reaches with the greatest active channel width, including the 

reach immediately downstream from the Little Colorado River (RM 61.5-77)(McGuinn-Robbins 

1995). Numbers and size also vary temporally as a function of sediment availability and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 17

hydrology, and their size can vary within a year at a given site. Backwaters declined in number 

from 1990 to 1992 under experimental high fluctuating flows and MLFF, but a rapid but short 

lived increase in backwater numbers resulted from high inputs and flows from the Little 

Colorado River in 1993 as a result of high flood flows (Beus et al. 1994, McGuinn-Robbins 

1995). Backwaters created in 1993 declined in 1994 under more average sediment and flow 

conditions (McGuinn-Robbins 1995). Backwater number can also vary tremendously depending 

on flow elevation during sampling and tends to be greatest at low flow elevations. Stevens and 

Hoffnagle (1999) noted that backwater numbers and area were reduced at flows greater than 

10,000 cfs at any given point in time. McGuinn-Robbins found more backwaters during 1990 at 

the 5,000 cfs level than at the 8,000 cfs level, although backwater area was greatest at the 8,000 

cfs level. 

Persistence of backwaters created during the 1996 high flow test appeared to be strongly 

influenced by post-high flow dam operations. Whereas the 1996 test resulted in creation of 26 

percent more backwaters, potentially available as rearing areas for Grand Canyon fishes, most of 

these newly created habitats disappeared within two weeks due to reattachment bar erosion 

(Brouder et al. 1999, Hazel et al. 1999, Parnell et al. 1997, Schmidt et al. 2004). Nearly half of 

the total sediment aggradation in recirculation zones had eroded away during the 10 months 

following the experiment and was associated in part with relatively high fluctuating flows of 

15,000-20,000 cfs (Hazel et al. 1999). 

Goeking et al. (2003) found no relationship between backwater number and flood 

frequency, although backwater size tends to be greatest following high flows and less in the 

absence of high flows due to infilling. Considering both area and number, however, no net 

positive or negative trend in backwater availability was noted during 1935 through 2000. At the 

decadal scale, several factors confound interpretation of high flow effects on backwaters 

bathymetry, including site-specific relationships between flow and backwater size, temporal 

variation within individual sites, and high spatial variation in reattachment bar topography 

(Goeking et al. 2003). Efficacy of high flow tests at creating or enlarging backwaters also 

depends on antecedent sediment load and distribution, hydrology of previous years (Rakowski 

and Schmidt 1999) and post-high flow river hydrology, which can shorten the longevity of 

backwaters to a few weeks depending on return channel deposition rates or erosion of 

reattachment bars (Brouder et al. 1999). 

The 1996 high flow caused an immediate reduction in benthic invertebrate numbers and 

fine particulate organic matter (FPOM) through scouring (Brouder et al. 1999, Parnell et al. 

1999). Invertebrates had rebounded to pre-test levels by September 1996, but it is thought that 

the rate of recolonization was hindered by a lack of FPOM. Still, recovery of key benthic taxa 

such as chironomids and other Diptera was relatively rapid (3 months), certainly rapid enough 

for use as food by the following summer’s cohort of young-of-year native fish (Brouder et al. 

1999). Also during the 1996 high flow test, Parnell et al. (1999) documented burial of 

autochthonous vegetation during reattachment bar aggradation, which resulted in increased 

levels of dissolved organic carbon, nitrogen and phosphorus in sandbar ground water and in 

adjacent backwaters. These nutrients are thus available for uptake by aquatic or emergent 

vegetation in the backwater. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 18

Dam operations may influence the food base and hence food availability for humpback 

chub. Humpback chub are usually considered an omnivore with a diet consisting of insects, 

crustaceans, plants, seeds, and occasionally small fish and reptiles. They appear to be 

opportunistic feeders, capable of switching diet according to available food sources, and 

ingesting food items from the water’s surface, mid-water, and river bottom. Arizona Game and 

Fish Department (1996) reported that juvenile humpback chub in Grand Canyon consumed 19 

different prey items, eight more than any other species examined, which included chironomid 

larvae, terrestrial insects, simuliid larvae, and copepods. The green alga Cladophora has often 

been recorded as a large component of humpback chub diet, mixed with a variety of 

invertebrates and detritus (Minckley et al. 1980, Carothers and Minckley 1981, Kubly 1990, 

Valdez and Ryel 1995). Valez and Ryel (1995) found that humpback chub in the mainstem river 

consumed 14 invertebrate taxa and nine terrestrial taxa (Valdez and Ryel 1995), including 

simuliids (blackflies, in 77.8% of fish), chironomids (midges, 57.6%), Gammarus (freshwater 

shrimp, 50.6%), Cladophora (23.4%), Hymenoptera (wasps, 20.9%), and cladocerans (water 

fleas, 19.6%). Seeds and human food remains were found in eight (5.1%) and seven (4.4%) fish 

respectively. Diet composition was related to food availability, illustrating the opportunistic 

feeding habit of humpback chub; for example, simuliids were available and consumed 

throughout the canyon, but terrestrial invertebrates replaced Gammarus in lower reaches where 

the latter were absent. Adult humpback chub in the Little Colorado River have also been reported 

to be cannibalistic on their young during periods of high reproductive success (Gorman 1994). 

Drift, organic matter drifting with the current in the water column, is an important aspect 

of the food base because particulate organic matter becomes available to downstream organisms 

to feed on via drift. Researchers in Grand Canyon have not had consistent results when 

examining the link between seasonality and drift, with the greatest quantities found in either the 

spring (McKinney et al. 1999) or summer (Shannon et al. 1996). There does appear to be a direct 

relationship between the amount of organic matter in the drift and flow volume (Angradi and 

Kubly 1994, Benenati et al. 2001 ). Fluctuations in flow can also influence drift directly because 

periodic desiccation can weaken algae and invertebrates causing fragmentation and subsequent 

entrainment by the river (Kennedy and Gloss 2005) or indirectly through the concomitant daily 

increases in flow volume (Shannon et al. 1996). McKinney et al. (1999) found that the density 

of Gammarus in the drift increased on the descending limb of the fluctuating hydrograph in Glen 

Canyon. Kennedy and Gloss (2005) summarized that the reduction in fluctuations from MLFF 

likely increased food base overall, especially the standing crops of important food items like 

Gammarus and Cladophora, due to a net increase in the amount of river bottom that is 

permanently submerged, but they also noted that large changes in monthly volume present under 

MLFF may periodically destroy significant quantities of food available for fish (Kennedy and 

Gloss 2005). 

In a study conducted in the upper Colorado River basin (middle Green River, Utah) 

Grand et al. (2006) found that the most important biological effect of fluctuating flows in 

backwaters is reduced availability of invertebrate prey caused by dewatered substrates (see also 

Blinn et al. 1995), exchange of water (and invertebrates) between the mainchannel and 

backwaters, and (to a lesser extent) reduced temperature. As the magnitude of within-day 

fluctuations increases, so does the proportion of backwater water volume influx, which results in 

a net reduction in as much as 30 percent of daily invertebrate production (Grand et al. 2006). 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 19

Potential geomorphic differences between the Grand Canyon and the Upper Colorado River 

basin underline the need for additional research investigation. 

An outstanding information need for management of Grand Canyon backwaters is the 

relationship between backwater bathymetry and suitability as fish habitat, specifically the 

relationship between depth, area, volume and thermal characteristics. Goeking et al. (2003) 

point out large backwaters may not incur as many benefits to young native fish as smaller 

backwaters because the latter will warm faster and thus remain warmer over time than larger 

backwaters; however, due to their depth, they may be more frequently available as fish habitat 

over a greater range of flows. In the Upper Colorado River basin, Colorado pikeminnow were 

found to utilize backwaters with average depths greater than 0.3 m (1.0 ft)(Trammell and Chart 

1999) and average areas of 992 m2 (0.245 acre)(Day et al. 1999). The issue of backwater depth 

is a research need from the standpoint that while greater depths afford more availability over a 

wide range of flows (Muth et al. 2000), the concurrent increase in volume with depth may slow 

warming rates. 

Water temperatures in the mainstem Colorado River downstream of Glen Canyon Dam 

were relatively constant during the period from 1980 to 2000. In 2000, the AMP conducted a 

low summer steady flow experiment during which Glen Canyon Dam releases were dominated 

by a steady flow of 8,000 cfs. The experiment resulted in significant warming of the mainstem, 

likely due to the reduced volume and somewhat secondarily to a lack of a fluctuating flow 

regime. Subsequent efforts to develop a mainstem temperature model for the Colorado River 

below Glen Canyon Dam corroborate that release volume has a strong effect on downstream 

temperature (Anderson and Wright 2007), although reservoir elevation appears to have a 

stronger effect (Wright et al. 2008). Drought conditions in the Colorado River basin since 2000 

have resulted in low Lake Powell reservoir levels such that dam release water temperature was 

significantly increased. Increased water temperature of releases has continued through 2008 as a 

result of inflow and/or reservoir elevations, with the warmest years occurring from 2004-2006 

(GCMRC unpublished data). These warmer temperatures have provided a test of the hypothesis 

of how native fish would respond to dam modifications (i.e. a selective withdrawal structure) or 

changes in operations to warm release water temperatures. The positive change in the status of 

native fishes during this period would seem to support this approach. However other actions 

during this period, such as the removal of nonnative fishes (discussed below) may have 

contributed to this response. Additionally, in a workshop conducted by GCMRC in April of 

2007 to support the Bureau of Reclamation’s Long Term Experimental Plan development (U.S. 

Geological Survey 2008a), a panel of scientists concluded that although the single most 

important condition that would benefit the humpback chub in the near term is warming mainstem 

nearshore habitats, control of nonnative species is also key. The panel further noted that the 

most readily available tool to stabilize the presence and persistence of warm nearshore habitats is 

steady flows from Glen Canyon Dam and that a selective withdrawal structure should be built 

only if it is designed to release the warmest water possible and also have the ability to release 

cool water under all conditions, including when reservoir conditions are relatively low and 

release water would normally be warm. Warmer water, either that provided through a selective 

withdrawal structure or due to drought or climate change could result in invasion of nonnative 

warm-water piscivorous fish (Johnstone and Lauretta 2007, Rahel et al. 2008). The ability to 

also release cool water was thought to be necessary to control any future expansions or invasions 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 20

of warmwater nonnative aquatic species, especially nonnative fish. The Bureau of Reclamation 

prepared a draft risk assessment model to evaluate risks and benefits from a two-unit selective 

withdrawal structure on Glen Canyon Dam. The assessment showed benefits to all native fish 

species, but also benefits to most nonnative fish species, especially rainbow trout, brown trout, 

and smallmouth bass. Interestingly, the abundance and distribution of channel catfish was 

relatively unaffected by the selective withdrawal structure (Valdez and Speas 2007). 

 Nonnative fish species have been present in the lower Colorado River, and likely in 

Grand Canyon, for over a century (Mueller and Marsh 2002). Programs to introduce non-native 

species for sport and food into Grand Canyon began at the turn of the century. Most releases 

were trout species, although warm-water fish, including carp, were also stocked. Trout were 

introduced for sport purposes by the National Park Service (NPS), Arizona Game and Fish 

Department, and the US Fish and Wildlife Service in the 1920s. NPS ceased stocking in 1964, 

the Arizona Game and Fish Department continued to plant rainbow trout near Lees Ferry until 

the 1990's. Since 1956, 24 nonnative fish species have been reported from Grand Canyon; 17 of 

which were present before the closure of Glen Canyon Dam (Valdez and Ryel 1995, Wieringa 

and Morton 1996). In Grand Canyon, brown trout, channel catfish, black bullhead, and rainbow 

trout have been identified as principal predators of young humpback chub (Marsh and Douglas 

1997, Valdez and Ryel 1997). Valdez and Ryel (1997) also theorized that common carp 

(Cyprinus carpio) could be a significant predator of incubating humpback chub eggs in the Little 

Colorado River. Minckley (1991) suggested that nonnative fish predation is the single most 

important threat to the persistence of native fishes in Marble and Grand Canyons. The potential 

for invasion of black bass species under warmer water conditions in Grand Canyon may pose a 

serious threat; smallmouth bass (Micropterus dolomieu) have become a significant predator in 

the Yampa River (U.S. Fish and Wildlife Service 2008), and largemouth bass (Micropterus 

salmoides) appear to be a significant predator on native fishes in the San Juan River (Pilgera et 

al. 2008). 

Generally, the upper reaches of the mainstem river are dominated by coldwater nonnative 

species, such as rainbow trout, and the lower reaches by warmwater species such as channel 

catfish and common carp. Brown trout are captured in greatest numbers in and near Bright 

Angel Creek (Rogers and Makinster 2006, Johnstone and Lauretta 2007). Catfish appear to be 

the dominant species in the mainstem below Diamond Creek and above the Lake Mead delta 

area (Ackerman 2007). Other nonnative species such as bullhead (Ameiurus spp.), fathead 

minnow (Pimephales promelas), red shiner (Cyprinella lutrensis), and plains killifish (Fundulus 

zebrinus) are primarily tributary species, mostly in the Little Colorado River (Van Haverbeke 

2006) but can occur in the mainstem, especially in backwaters immediately downstream of the 

confluence of the Little Colorado River (Johnstone and Lauretta 2007). These small-bodied 

species may be important predators and competitors of young humpback chub, especially in 

backwaters and other sheltered near-shore habitats, and given their occurrence in areas and 

habitats of high importance. 

The Lee’s Ferry Reach (dam to Paria River) supports a self-sustaining fishery of rainbow 

trout, whose population and food base are influenced by dam operations (McKinney et al. 1999, 

McKinney and Persons 1999, McKinney et al. 2001, Speas 2004, Speas et al. 2004, Korman et 

al. 2005). Brown trout occasionally move into the reach between the dam and the Paria River 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 21

from downstream populations, but is not managed as part of the sport fishery and is not a desired 

species in this reach. Although their abundance has declined significantly over the last seven 

years, rainbow trout are still the dominant nonnative species between the Paria River and the 

Little Colorado River (Ackerman 2007, Johnstone and Lauretta 2007). Other nonnative species 

sporadically found in that reach include brown trout, common carp, channel catfish and fathead 

minnow. Invasion of nonnative fish from the upper Little Colorado River has recently been 

documented (Stone et al. 2007). 

Floods have, for some time, been identified in small streams as a potential means to 

disadvantage nonnative fishes and thereby advantage native fishes (Meffe 1984, Minckley and 

Meffe 1987) although that potential in a large river system remains unproven. Dam operations 

have been speculated as a means of disadvantaging nonnative fishes via artificial floods or other 

flows from displacement due to flooding, stranding, or altering spawning and rearing habitats. 

The 1996 Glen Canyon Dam beach habitat building flow appeared to have only short-term 

effects on the densities of some nonnative fishes (primarily small-bodied forms like plains 

killifish and fathead minnow; Hoffnagle et al. 1999, Valdez et al. 1999), perhaps because at 

45,000 cfs, the flow was still less than the pre-dam one-year return interval flood of 50,000 cfs 

(Hoffnagle et al. 1999, Topping et al. 2003). From 2003-2005, releases from Glen Canyon Dam 

included “experimental fluctuating flows”, high fluctuating releases of 5,000-20,000 cfs per day 

from January-March, to test their capability to reduce the survival rate of young rainbow trout to 

reduce the size of the Lees Ferry trout population. These flows had little effect on incubation 

mortality and consequently adult population size (Korman et al. 2005). Additionally, reductions 

in early life stages appeared to be offset by compensatory survival at larger life stages (Korman 

et al. 2005). Korman et al. 2005 did note however that because young-of-year rainbow trout 

generally remain at the daily minimum flow elevation in Lees Ferry, and because September 

flow reductions during the study resulted in density reductions documented in Glen Canyon, as 

well as substantial literature on stranding impacts to young trout, a ‘stranding’ flow operation 

from Glen Canyon Dam targeted at reducing young-of-year rainbow trout recruitment could be 

very effective. 

The Grand Canyon fish community has apparently shifted over the past five years from 

one dominated by nonnative salmonids to one dominated by native species (Trammell et al. 

2002, Johnstone et al. 2003, Arizona Game and Fish Department 2006b, Lauretta and Serrato 

2006, Ackerman 2007). Electrofishing catch rates of flannelmouth and bluehead suckers have 

increased four to six-fold in the past seven years, whereas trout catch rates have correspondingly 

declined (Arizona Game and Fish Department 2006b, Arizona Game and Fish Department 

2008); a similar trend is evident from trammel net data (Johnstone et al. 2003, Lauretta and 

Serrato 2006). Riverwide, young flannelmouth suckers were more abundant in 2004 than the 

previous 16 years (Johnstone and Lauretta 2007) and speckled dace were abundant in hoop net 

and seining samples, particularly in downstream reaches (Ackerman 2007). It is hypothesized 

that the recent shift from nonnative to native fish is due in part to warmer water temperatures, 

although the decline of coldwater salmonid competitors (due to mechanical removal, temperature 

increases, or other causes) is also a potential cause (USGS 2006, Ackerman 2007). Rainbow 

trout currently appear to be increasing in abundance system-wide (AGFD unpublished data). 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 22

Recent declines in trout abundance in the Lees Ferry tailwater may be due to a variety of 

factors, including, but probably not limited to, increased daily fluctuations during the 2003-2005 

period, increased water temperatures with commensurate increased trout metabolic demands, 

excessive population for available food supply, periodic oxygen deficiencies and nuisance 

aquatic invertebrates (e.g., New Zealand mudsnails Potamopyrgus antipodarum). The individual 

or collective contribution of these factors, if any, to the decline is uncertain at this time. Whirling 

disease, a fish disease that can decimate trout populations, was detected in Lees Ferry in June of 

2007, but at a very low level, and has not been detected since, and is not likely a cause of the 

decline in trout abundance. Highly invasive quagga mussels (Dreissena sp.) were discovered in 

Lake Mead during the summer of 2007. Because of their high filtration and reproductive rates, 

quagga mussels frequently alter aquatic food webs and damage water supply infrastructure. A 

risk assessment on the establishment potential of quagga mussels in the Colorado River below 

Glen Canyon Dam concluded that there is low risk of these mussels becoming established in 

high densities in the Colorado River or its tributaries below Lees Ferry (Kennedy 2007), 

although conditions in the clear tailwater reach immediately below the dam appear more suitable 

for establishment of this species. 

The nonnative fish fauna of the Lees Ferry reach historically included less frequent taxa 

including common carp, largemouth bass (Micropterus salmoides), golden shiner (Notemigonus 

crysoleucas), redside shiner (Richardsonius balteatus), striped bass (Morone saxatilis), and 

threadfin shad (Dorosoma petenense) (GCMRC unpublished data). In more recent years, 

however, young-of-year green sunfish (Lepomis cyanellus), smallmouth bass, brown trout, and 

channel catfish have been collected in this reach; mature smallmouth bass and walleye 

(Stizostedion vitreum) have also been collected (GCMRC unpublished data). Sources of these 

fish are unknown, but the closest source containing green sunfish, catfish and smallmouth bass 

would be Lake Powell; means of introduction is unknown, but Reclamation is currently assessing 

risk potential for entrainment of Lake Powell fish through the dam penstocks. 

Recently, a few smallmouth bass and striped bass were collected in the vicinity of the 

Little Colorado River (GCMRC unpublished data), but no population-level establishment has 

been documented to date. There are also recent records of green sunfish, black bullhead, yellow 

bullhead (Ameiurus natalis), red shiner, plains killifish and largemouth bass downstream of the 

Little Colorado River, usually associated with warm springs, tributaries, and backwaters 

(Johnstone and Lauretta 2007, GCMRC unpublished data). Striped bass are found in relatively 

low numbers below Lava Falls (Ackerman 2007). 

Stone et al. (2007) reported common carp, fathead minnow and red shiner below Grand 

Falls (an ephemeral reach of the Little Colorado River), which indicates that the Little Colorado 

River is a viable conduit for introduction of nonnative fish from areas higher in the watershed. 

Other nonnative fish documented in the upstream reaches of the Little Colorado River basin 

include golden shiner, black bullhead, yellow bullhead, channel catfish, rock bass (Ambloplites 

rupestris), bluegill, green sunfish, smallmouth bass, and largemouth bass (Stone et al. 2007); 

thus these species could eventually occur in Grand Canyon. 

Fish samples collected below Diamond Creek in 2005 (Ackerman et al. 2006) were 

comprised primarily of red shiner (28 percent), channel catfish (18 percent), common carp (12 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 23

percent), and striped bass (9 percent); smallmouth bass, mosquitofish (Gambusia affinis), and 

fathead minnow were also present in low numbers. Bridge Canyon Rapid impedes upstream 

movement of most fish species, except for the striped bass, walleye, and channel catfish (Valdez 

1994, Valdez et al. 1995). Nonnative fish species increased from 11 above to 18 below the rapid 

(Valdez 1994, Valdez et al. 1995). Above Bridge Canyon Rapid, the red shiner was absent, but 

below the rapid it comprised 50 percent and 72 percent of all fish captured in tributaries and the 

mainstem, respectively (Valdez 1994, Valdez et al. 1995). Other common fish species found 

below Bridge Canyon Rapid include common carp, fathead minnow, and channel catfish; 

however, very little fish habitat exists in this reach due to declining elevations of Lake Mead and 

subsequent downcutting of accumulated deltaic sediments in inflow areas. Flannelmouth suckers 

comprised about 15 percent of the total catch from this reach during 2005 (Ackerman et al. 

2006), several times greater than the 1.3 percent observed during 1992-1995 (Valdez et al. 1995). 

Percentage of speckled dace in the reach has not changed appreciably over the last decade, and 

no bluehead suckers were collected during 2005 (Valdez et al. 1995, Ackerman et al. 2006). 

In an attempt to benefit native species, mechanical removal targeted at nonnative 

salmonid species in the mainchannel Colorado River and tributaries in Grand Canyon took place 

during 2003-2006 (Coggins and Yard 2003). Removal of salmonids and other nonnative fish 

(black bullhead, fathead minnow, common carp, brown trout) in the vicinity of the Little 

Colorado River by electrofishing contributed to a 90 percent reduction in rainbow trout over a 

four year period, although trout also declined significantly throughout this period in Glen, 

Marble, and Grand canyons, perhaps due to warmer water or other factors as discussed above. 

Main channel water temperatures during the removal period were as high as 6 °C (11 °F) above 

the 1990-2002 average. At the same time, electrofishing catch rates of young-of-year and age-1 

flannelmouth sucker, bluehead sucker, and humpback increased by as much as a factor of ten; 

catch rates of speckled dace also increased. Recent monitoring indicates rainbow trout are 

increasing in this reach, although data not yet analyzed (AGFD unpublished data). 

Mechanical removal of spawning brown trout through weir operations in Bright Angel 

Creek yielded inconclusive results. During operations in 2002 (November-January), over 400 

brown trout were removed from Bright Angel Creek and euthanized (Leibfried et al. 2005). 

When a similar removal effort was conducted in November-January of 2006, only 54 brown 

trout were removed, and rainbow trout catches were decreased by a similar proportion 

(Sponholtz and VanHaverbeke 2007). The decline cannot be attributed to weir operations alone, 

however, because of the considerable system-wide decline in abundance of these species during 

this time (Arizona Game and Fish Department 2008). 

Multi-pass backpack electrofishing was evaluated as a mechanical control technique in 

Bright Angel and Shinumo creeks. In a 3.35 km reach of Bright Angel Creek, approximately 55 

percent and 57 percent of the brown and rainbow trout populations, respectively, were removed 

through as many as 4 electrofishing passes. At Shinumo Creek, 35 to 85 percent of rainbow 

trout were removed through similar methods (Leibfried et al. 2006). In both creeks, however, 

recolonization rates from upstream and downstream have not been evaluated. Recently, 

GCMRC has proposed to implement a strategy to reduce warmwater nonnative fish (including 

crayfish) abundance and negative impacts to native fish found in the Colorado River in Grand 

Canyon (Hilwig et al., in review). This strategy would very likely be needed to offset potential 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 24

undesirable positive responses of nonnative fish to artificial or natural increases in river 

temperatures. The draft plan consists of short-term period to collect baseline information needs 

followed by implementation of longer-term nonnative fish control and management programs. 

Another aspect of the changes in sediment supply in Grand Canyon that may affect 

humpback chub is turbidity. Predam, turbidity was very high much of the year except during 

base flows. As discussed above, the dam largely eliminated turbid mainstem conditions. The 

mainstem is turbid now only at times of tributary flooding. With increases in nonnative fishes 

over the last century in Grand Canyon, especially sight-feeding predators like rainbow trout, this 

loss of turbidity may exacerbate the losses of humpback chub to piscivory of nonnative fishes. 

Turbidity has been shown to decrease the reactive distance of rainbow trout (Barrett et al. 1992). 

Johnson and Hines (1999) found that decreased turbidity resulted in significantly greater rates of 

predation of razorback sucker from both native Colorado pikeminnow and green sunfish. 

Interestingly, data collected on diet of rainbow and brown trout in the Colorado River in Grand 

Canyon during mechanical removal of these species indicated that turbidity had little effect on 

incidence of predation of native fish (GCMRC, unpublished data). 

Asian fish tapeworm (Bothriocephalus acheilognathi), and anchor worm (Lernaea 

cyprinacea), may pose threats to native fish below Glen Canyon Dam. Asian tapeworm, first 

reported from Grand Canyon in 1990, is currently the most abundant fish parasite in the Little 

Colorado River, infecting 23-51 percent of all humpback chub (Clarkson et al. 1997, Choudhury 

et al. 2004) and also a variety of cyprinids. Main channel infestation rates are much lower and 

may be temperature-limited (4-22 percent) (Valdez and Ryel 1995). Optimal B. acheilognathi

development occurs at 20-30 °C (68-86 °F) (Granath and Esch 1983). Choudhury et al. (2004) 

hypothesized that infection rates were positively related to both fish host and copepod density in 

the Little Colorado River and parasitic fauna found there have diversified through invasion of 

nonnative host fish species. Lernaea cyprinacea infects humpback chub at a higher rate than 

other species of fish in Grand Canyon (Hoffnagle 2000) and favors temperatures greater than 18 

°C (64 °F) (Grabda 1963), with 23-30 °C (73-86 °F) being optimum (Bulow et al. 1979). Postdam mainstem temperatures have prevented L. cyprinacea from completing its life cycle and 

limited its distribution to warmer waters. Infestation apparently does not increase fish mortality 

in the Upper Colorado Basin (Valdez and Ryel 1995). 

3.2 Summary of Current Threats to Humpback Chub in the Lower Colorado River Basin 

by Recovery Factor 

 As described in the preceding baseline discussion, past habitat alteration and invasion of 

nonnative fishes have contributed to the current status of the humpback chub in Grand Canyon 

and are continuing threats. These threats are summarized here from threats identified in the 

Humpback Chub Recovery Goals and draft Humpback Chub Recovery Goals 2008 Revisions 

(U.S. Fish and Wildlife Service 2002, 2008) and other documents including three AMP reports 

(Gloss and Coggins 2005, Melis et al. 2006b, U.S. Geological Survey 2008a). The Ad Hoc 

refers the reader to these documents and sections for a more complete picture of our status of 

knowledge of these threats. The Ad Hoc found that there is uncertainty associated with many of 

these threats with regard to their respective severity and interaction. Threats to the humpback 

chub in Grand Canyon, listed by recovery factor, are summarized as follows. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 25

Recovery Factor A.─ Adequate Habitat and Range for Recovered Populations Provided 

1. Inadequate flows to support all life stages 

As described in the preceding seection, flows have changed dramatically in Grand Canyon since 

closure of Glen Canyon Dam in 1962. Spring peak flows are much reduced and base flows in 

summer through winter have increased. Daily fluctuations in flow, unknown in the ecosystem 

historically, are now the norm. These changes may no longer provide the necessary 

requirements for all life stages of humpback chub in the mainstem river. Little is known about 

the overall and continuing effect of these changes, but some aspects, such as effects on mainstem 

temperature and sediment transport are available and are discussed below. 

2. Inadequate habitat due to streamflow regulation 

As described above in the baseline discussion, streamflow regulation by Glen Canyon Dam has 

resulted in drastic changes in the riverine ecosystem in Marble and Grand canyons, changes that 

have contributed to the decline in status of the humpback chub. Daily flow fluctuations may 

alter habitat suitability, structure, and availability, especially for young fish. Fluctuations cause 

destabilization of nearshore habitats (Hoffnagle 2000), which has been implicated in increased 

energy demand and increased predation of humpback chub (Korman et al. 2004, 2006), and also 

causes colder water temperatures in backwaters, which may be important habitats for native fish 

(Arizona Game and Fish Department 1996, Trammel et al. 2002, Korman et al. 1996). In the 

Upper Colorado River basin (in the Green River in Utah), Grand et al. (2006) found that 

fluctuating flows significantly reduced the availability of invertebrate prey, an important food 

source for young fish, due to dewatered substrates, exchange of water (and invertebrates) 

between the main channel and backwaters, and reduced temperature. Robinson et al. (1998) and 

Stone and Gorman (2005) hypothesized that fluctuations reduced the growth and survival of young 

humpback chub Fluctuations are also directly proportional to export of sediment; thus dam 

operations may contribute to the loss of important nearshore habitats, especially those that depend on 

sand bar formation, such as backwaters (Melis et al. 2006b). 

Cold hypolimnetic releases from Glen Canyon Dam have long been acknowledged as a major 

threat to humpback chub (Maddux et al. 1987). Generally water temperature in the mainstem 

Colorado River is primarily a function of: 1) Lake Powell reservoir level; 2) release volume; 3) 

inflow volume and temperature; and 4) ambient air temperature. This function typically results 

in release temperatures 8-10 °C (46-50 °F; GCMRC unpublished data). Release volume and 

Lake Powell reservoir level have been shown to have a significant effect on mainstem water 

temperature (Anderson and Wright 2007, Wright et al. 2008). Effects of cold temperatures are 

further discussed below. 

3. Inadequate water temperatures to support all life stages 

The humpback chub is an obligate warm-water species that requires relatively warm water 

temperatures of about 16-22 °C (61-72 °F) for spawning, egg incubation, and survival of young 

(Hamman 1982, Marsh 1985). Typical mainstem temperatures range from about 10-12 °C (50-

54 °F; Gloss and Coggins 2005), although have recently been as warm as 17 °C (64°F) in 2005 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 26

(GCMRC unpublished data) due to drought. Because cold temperatures can also cause larvae 

and juvenile fish to experience thermal shock (Berry 1988), and swimming ability is greatly 

reduced (Berry and Pimentel 1985, Ward and Bonar 2003), juvenile humpback chub exiting the 

warm Little Colorado River and entering the cold mainstem may be too stunned to effectively 

avoid predation or swim to suitable nearshore habitats (Lupher and Clarkson 1994, Valdez and 

Ryel 1995, Marsh and Douglas 1997, Robinson et al. 1998, Clarkson and Childs 2000, Robinson 

and Childs 2001, Ward et al. 2002, U.S. Geological Survey 2008a). 

An important aspect of mainstem water temperature is the effect on nonnative fishes. Cold 

mainstem water temperatures that have been the norm since Lake Powell filled 30 years ago 

have advantaged nonnative salmonids and apparently disadvantaged warm-water species such as 

green sunfish, smallmouth bass, and to some extent carp and channel catfish (Valdez and Ryel 

1995, Johnstone and Lauretta 2007). Temperature must continually be examined for its effect on 

management of both native and nonnative fish species in Grand Canyon. Efforts to modify the 

dam or operations to warm mainstem temperatures, or “natural” warming due to drought and 

effects of climate change, could enhance conditions for invasion of warm-water nonnative fishes. 

4. Inadequate food base to support all life stages 

Many variables, including flow, turbidity, and temperature may affect humpback chub food base. 

Our understanding of how dam operations affect food base, the degree to which food base is 

limiting, and what threat exists in this, regard is limited. Understanding the food web and how it 

is affected by both dam operations and nonnative species is an important information need (U.S. 

Geological Survey 2008b). 

5. Inadequate water quality to support all life stages 

As discussed previously, turbidity may have some effect on nonnative fish predation on native 

fishes in Grand Canyon (Barrett et al. 1992, Johnson and Hines 1999). Since closure of Glen 

Canyon Dam, flow in the mainstem Colorado River is much less turbid. Also, selenium or other 

contaminants could affect reproduction or other aspects of humpback chub life history. Many 

potential contaminants (e.g., petroleum products, radionuclides, selenium, pesticides, and heavy 

metals such as mercury) could affect water quality in the form of nonpoint source pollution. 

Understanding how contaminants act to suppress populations is not well understood (Hinck et al. 

2007). Another identified concern is the potential for a hazardous materials spill on the Highway 

89 Bridge at Cameron, Arizona, which is approximately 60 km (37 miles) upstream of occupied 

habitat in the Little Colorado River. Although much of this reach of the river is dry during most 

of the year, floods create flow in this reach almost annually, and a spill could have disastrous 

affects on water quality downstream in the prime humpback chub spawning habitat of the Little 

Colorado River. 

Recovery Factor B.─Protection from Overutilization for Commercial, Recreational, Scientific, or 

Educational Purposes 

6. Over-handling for scientific studies 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 27

Despite the essential need to monitor humpback chub status, netting and electrofishing as well as 

marking fish, such as with PIT tags, can cause mortality. Trammel netting likely causes the most 

mortality of the gears employed in Grand Canyon to survey humpback chub, but electrofishing 

and hoop netting also likely cause some level of mortality (Ruppert and Muth 1997, Paukert et 

al. 2005, Ward et al. 2008). Although unlikely to cause population-level affects singularly, 

cumulatively, with effects from other threats, this threat could be significant. 

 

7. Adverse effects from recreational use 

Very little data exist on the effects of recreation on humpback chub. Recreational use of the 

Little Colorado River may affect reproductive habitat or interfere with reproduction. Although 

the potential for adverse effects has been recognized, and some regulations have been 

implemented to address this threat, more research is needed in this area (National Park Service 

2007). 

 

Recovery Factor C.─Adequate Protection from Disease or Predation 

8. Asian tapeworm, Lernaea sp., other parasites and diseases 

Asian tapeworm, and anchor worm (Lernaea cyprinacea), may pose threats to native fish below 

Glen Canyon Dam. Asian tapeworm, first reported from Grand Canyon in 1990, is currently the 

most abundant fish parasite in the Little Colorado River, infecting 23-51 percent of all humpback 

chub (Clarkson et al. 1997, Choudhury et al. 2004) and also a variety of cyprinids. Main channel 

infestation rates are much lower (4-22 percent) and may be temperature-limited (Valdez and 

Ryel 1995). Optimal B. acheilognathi development occurs at 20-30 °C (68-86 °F) (Granath and 

Esch 1983). Choudhury et al. (2004) hypothesized that infection rates were positively related to 

both fish host and copepod density in the Little Colorado River and parasitic fauna found there 

have diversified through invasion of nonnative host fish species. Lernaea cyprinacea infests 

humpback chub at a higher rate than other species of fish in Grand Canyon (Hoffnagle 2000) and 

favors temperatures greater than 18°C (64 °F)(Grabda 1963), with 23-30 °C (73-86 °F) being 

optimum (Bulow et al. 1979). Postdam mainstem temperatures have prevented L. cyprinacea

from completing its life cycle and limited its distribution to warmer backwaters. Infestation 

apparently does not increase fish mortality in the Upper Colorado Basin (Valdez and Ryel 1995). 

Intestinal nematodes and trematodes (Ornithodiplostomum sp. and Rhabdochona sp.) have been 

documented from humpback chub in the Little Colorado River (Hoffnagle et al. 2000). 

9. New intentional and unintentional introductions of nonnative aquatic species in the 

Colorado River and its tributaries in Grand Canyon 

Invasions of nonnative species can have devastating impacts on native species, even to the extent 

of causing extinction. Numerous potential predators and competitors of humpback chub occupy 

the mainstem Colorado River and its tributaries in proximity to Marble and Grand Canyons, and 

could invade given suitable habitat conditions. Many of these species are contacted in Marble 

and Grand canyons at low levels, such as green sunfish, smallmouth bass and walleye. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 28

Stone et al. (2007) found that non-native fish are transported to the lower reaches of the Little 

Colorado River during floods from presently unknown sources in higher reaches of the 

watershed. GCMRC conducted a nonnative species workshop in December 2008; workshop 

participants determined that identifying and eliminating sources of nonnative species is a high 

priority for conservation of humpback chub. 

The nonnative invasive quagga mussel, a close relative of the zebra mussel (Dreissena 

polymorpha), has recently invaded the lower Colorado River as far upstream as Lake Mead, and 

could invade Grand Canyon. GCMRC conducted a risk assessment on the potential for quagga 

mussel to invade the Colorado River Ecosystem (defined as the segment of the Colorado River 

from just below Glen Canyon Dam to Diamond Creek; Kennedy 2007). The assessment 

concluded that there is low risk of these mussels becoming established in high densities in the 

Colorado River or its tributaries below Lees Ferry due to poor habitat conditions, although 

conditions in the clear tailwater reach immediately below the dam appear more suitable for 

establishment. 

10. Nonnative fish species present in Grand Canyon 

Minckley (1991) considered nonnative fish predation to be the single most important threat to the 

persistence of native fishes in Marble and Grand Canyons. Brown trout (Salmo trutta), rainbow 

trout (Oncorhynchus mykiss), channel catfish (Ictalurus punctatus) and black bullhead (Ameiurus 

melas) are all locally common in the Colorado River in Grand Canyon and have been identified 

as principal predators of young humpback chub, with consumption estimates that suggest loss of 

complete year classes to predation (Marsh and Douglas 1997, Valdez and Ryel 1997). Data 

collected during nonnative removal efforts by the AMP from 2003-2006 indicate that predation 

rate by rainbow trout on humpback chub is substantial when trout densities are high. Common 

carp, also common in Grand Canyon, could be a significant predator of incubating humpback 

chub eggs in the Little Colorado River (Valdez and Ryel 1997). Small-bodied fishes such as red 

shiner and fathead minnow can be common in the Little Colorado River and the Colorado River 

in Grand Canyon and may compete with and prey upon young native fish in nursery habitats. As 

discussed above, efforts to target removal of these nonnative species have met with some 

success, particularly for rainbow trout (GCMRC unpublished data). 

Recovery Factor D.─Adequate Existing Regulatory Mechanisms 

11. Lack of legal protection of habitat and flow 

Long-term legal protection of habitat and flow in the Little Colorado River and mainstem is 

necessary for long-term conservation of humpback chub. The draft Recovery Goals (U.S. Fish 

and Wildlife Service 2008) identify the need to determine and implement mechanisms for legal 

protection of adequate habitat in the mainstem Colorado River through Grand Canyon and the 

Little Colorado River through instream-flow rights, contracts, agreements, or other means 

necessary to provide adequate habitat and sufficient range for all life stages of humpback chub to 

support a recovered Grand Canyon population. 

12. Need for conservation plans 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 29

The draft Recovery Goals (U.S. Fish and Wildlife Service 2008) require that conservation plans 

be developed for use after delisting to provide for the long-term management and protection of 

humpback chub populations. Example elements of such plans include provision of flows for 

maintenance of adequate habitat conditions for all life stages of humpback chub, regulation 

and/or control of nonnative fishes, minimization of the risk of hazardous-materials spills, 

minimization of risks of parasites, and monitoring of populations and habitats. Development of 

conservation plans is not an identified project of this plan because their development is more 

appropriate, and conservation needs for the species post-delisting will be better understood when 

humpback chub are considered for down-listing. 

Recovery Factor E.─ Other Natural or Manmade Factors 

13. Non-point source pollutants in the Little Colorado River watershed 

A number of potential sources of pollution exist in the Little Colorado River watershed. 

Collectively, these may affect water quality in occupied and critical habitat in the Little Colorado 

River and could affect reproduction and survival of all life stages of humpback chub. Many 

potential contaminants (e.g., petroleum products, radionuclides, selenium, pesticides, and heavy 

metals such as mercury) could affect water quality in the form of nonpoint source pollution. 

Understanding how contaminants act to suppress populations is not well understood (Hinck et al. 

2007). 

14. Hazardous materials spills at bridges over the Little Colorado River 

As discussed above, minimizing the risk of hazardous-materials spills into critical habitat is a 

priority. A spill at one of the Little Colorado River bridges such as the Highway 89 bridge at 

Cameron, Arizona, could be transported downstream to occupied and critical habitat, resulting in 

possible losses of all ages of humpback chub at the primary spawning location for the species in 

Grand Canyon. 

15. The interaction of threats 

Many of the threats listed here are known to interact, but the relationships are poorly understood. 

Cold water temperatures can cause thermal shock of juvenile humpback chub, for example, 

which could cause juvenile humpback chub to be more susceptible to predation by nonnative 

fishes. Management actions which could benefit humpback chub may have unintended 

consequences. While increased turbidity resulting from high flow tests may reduce predation 

pressure from nonnative fishes on humpback chub, it could also reduce primary production and 

ultimately food base available for humpback chub and other native fishes. Also, providing 

warmer water temperatures using steady flows or a selective withdrawal structure could benefit 

nonnative warm-water fishes more than native fishes, negating any beneficial effects to native 

species from increased predation losses. 

Another way to look at the interaction of threats is from a cumulative perspective. Examining 

native fish species records in the American Southwest (including humpback chub), Fagan et al. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 30

(2002) illustrated that as populations grow smaller and more isolated their risk of extinction 

increases. This is likely because the population is less robust and able to withstand some loss 

without long-term harm to the population structure and there is a lower likelihood that local 

losses will be offset by immigration from nearby populations. Another example is the “predator 

pit” hypothesis (Messier 1994). This hypothesis proposes that as a population of a species 

shrinks, especially when this happens rapidly, the predators of the species will have a greater and 

greater impact on its survival due to the relatively constant consumption amount, and thus 

increased consumption rate. In situations where predator populations also increase, the effect 

can be substantial. Mechanical removal of nonnative fish in the Colorado River in Marble and 

Grand Canyons from 2003-2006 indicated that while predation rate by rainbow trout on 

humpback chub was low, rainbow trout can reach densities where predation losses are significant 

(GCMRC unpublished data). Development of a comprehensive Colorado River ecosystem 

model would likely help to understand these interactions. 

3.3 An Overview of the Use of Management Actions to Address Threats 

Threats to the species and corresponding recommended management actions are provided 

in the strategy section 4.0. Of the 15 threats previously identified, some require more immediate 

attention to either ameliorate the threat or better understand its severity. Complex interactions 

among these threats may challenge future management, and our understanding of this is limited. 

Several threats to humpback chub in Grand Canyon require immediate attention; however, we 

lack sufficient information to prioritize these threats. These threats and current or potential 

management actions to address them include the following: 

 Water temperature: Cold water releases are known to inhibit mainstem 

reproduction, swimming ability, and growth of humpback chub. The AMP 

science advisors completed a risk assessment recommending a selective 

withdrawal structure on Glen Canyon Dam be built and tested (Baron et al. 2003); 

a recent panel of scientists concluded a selective withdrawal structure presents a 

serious risk because of the potential to advantage nonnative species, and 

recommended that it only be built if it could provide both warm and cool water at 

a wide range of reservoir elevations (U.S. Geological Survey 2008a). Also, 

temperatures of Glen Canyon Dam releases in recent years were much warmer 

due to the 2000 Low Summer Steady Flow and drought during the period 2000-

2008; warmer releases could continue given the predicted effects of global 

climate change (USCCP 2008). More evaluation of the effects of these 

temperatures is needed to determine the overall effect to native and nonnative 

fishes. 

 Predators: Control of nonnative species that prey on and compete with humpback 

chub in the Colorado River above and below the confluence of the Little Colorado 

River was implemented as an adaptive management experiment from 2003-2006 

for rainbow trout, brown trout, and other fish species susceptible to electrofishing 

(Coggins 2008). A corollary effort, using a weir, was implemented by the 

National Park Service (NPS) in 2005-2007 to remove trout from Bright Angel 

Creek (Leibfried et al. 2005). The NPS is also conducting feasibility studies for 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 31

removing non-native fish from other tributaries within Grand Canyon National 

Park. These efforts should be continued to better evaluate their benefit to 

humpback chub (U.S. Geological Survey 2008a). Mechanical removal of 

nonnative fishes in the mainstem was restarted in 2009 as a conservation measure 

or the 2008 biological opinion. Efforts are underway to address control of nonsalmonid predators, including in the mainstem, the Little Colorado River, and 

other tributaries, and development of nonnative control plans to address this 

threat. 

 Hazardous materials spills: The risk of hazardous materials spills continues to 

loom over the Little Colorado River. Immediate actions are needed to develop 

and implement a plan to minimize this risk (U.S. Fish and Wildlife Service 2008). 

 Parasites: Asian tapeworm and Lernaea copepod are the two parasites of most 

concern for humpback chub. Investigations should continue to assess extent of 

infestation, the risks of increased infection in the mainstem under warmer water 

conditions, and the potential for treatment to reduce infestation levels in the 

humpback chub population. 

 Flow regimes from dam releases: The effects of dam releases are not fully 

understood relative to humpback chub, but experimental flows continue to 

provide information under adaptive management. The U.S. Fish and Wildlife 

Service’s 2008 biological opinion included a conservation measure to conduct a 

nearshore ecology study to further develop information on the effect of flows on 

mainstem habitats for humpback chub. The Nearshore ecology study is planned 

to begin in FY 2009-2010 as a joint project between GCMRC and an external 

cooperator (U.S. Geological Survey 2008b). 

 Threat interactions: Although many possible interactions have been identified, 

these interactions are poorly understood, and require more study. The Ad Hoc 

recommends that an overall Colorado River ecosystem model be developed to 

better understand these interactions. 

4.0 STRATEGY FOR IMPROVING CONDITIONS FOR HUMPBACK CHUB IN THE 

LOWER COLORADO RIVER BASIN 

The AMP goals for humpback chub are to maintain or attain viable populations, remove 

jeopardy and prevent adverse modification to humpback chub critical habitat. This plan expands 

that goal to include assisting in achieving recovery goals for humpback chub in Grand Canyon 

by expanding the population size, improving recruitment and reducing threats to the population. 

This will be accomplished by (1) expanding the range of spawning and rearing in Grand Canyon 

for humpback chub, (2) increasing survival and recruitment of humpback chub, and (3) reducing 

the threat of catastrophic events or unintended consequences that may negatively affect the wild 

population of humpback chub. The Ad Hoc acknowledges that implementation of some 

elements of the strategy will be outside the scope of the AMP and will require additional and 

different funding sources and processes. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 32

4.1 Expanding the Range of Spawning and Rearing and Increasing Survival and 

Recruitment for Humpback Chub 

One mechanism for expanding range is to increase the suitability of the mainstem 

Colorado River for reproduction and recruitment of humpback chub. This may be accomplished 

by warming dam releases with a selective withdrawal structure and/or modifying dam releases to 

provide flows necessary for spawning and rearing, and mechanical removal of predators and 

competitors of humpback chub from both the mainstem and selected tributaries. A panel of 

scientists convened by GCMRC in 2007 concluded that utilizing stable flows is the only readily 

available means to achieve flow related habitat changes currently, and recommended providing 

stable releases from July 15 through mid-October. However, much uncertainty surrounds this 

action, necessitating scientific planning and assessment. Transloctaion to tributary streams in 

Grand Canyon also may serve to expand the reange of humpback chub in Grand Canyon, may 

provide habitat relatively free from threats, and have watersheds largely contained on Tribal or 

Federal land. Actions that are believed to help expand the range of humpback chub in the Lower 

Colorado River include: 

(1) Further explore the need to modify operations of Glen Canyon Dam either 

through construction and testing a selective withdrawal structure, by testing stable flow 

releases, or both, to improve habitat in the mainstem for humpback chub. Improving 

temperature conditions in the mainstem may improve humpback chub reproduction and 

survivorship. However, warmer temperatures in the mainstem may increase other threats 

such as predation by nonnative fishes and diseases and parasites, and thus should be 

thoroughly scientifically evaluated. Warmer water temperatures have been the norm rather 

the exception since 2003 and could continue to be released given the effects of increased 

demands of human populations on the Colorado River and the effects on runoff in the 

Colorado Basin from global climate change. A selective withdrawal structure should be able 

to supply cold water as well as the warmest water possible over a range of reservoir 

elevations to be effective and have the capability to minimize the spread of warm-water 

nonnative species. 

(2) Control existing non-native predators and competitors and prevent new 

introductions of nonnative species to reduce impacts to humpback chub and other native 

species. This would also help ensure that any negative impacts from temperature 

modification would not be exacerbated by an already high predator/competitor load. 

Additional research is needed to determine which non-natives have the greatest impact on 

humpback chub mortality, and which might be controlled by mechanical or other removal 

methods. Mainstem and tributary control actions should target non-native species using the 

most appropriate and effective methods. Monitoring of native and non-native fish species 

must be able to detect changes in these populations that may result from management 

actions. Development of a stocking plan for nonnative fish similar to the agreement between 

the U. S. Fish and Wildlife Service and the states of Utah and Colorado would help to 

prevent further incursions of predators and competitors into Grand Canyon. Completion and 

implementation of an invasive species management plan for the Little Colorado River Basin 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 33

that defines provisions for controlling escapement of non-native fishes may help to protect 

humpback chub in the reach of critical habitat in the lower Little Colorado River. 

(3) Use dam releases to improve habitat. Dam releases should continue to be 

evaluated as a means to: potentially displace or disadvantage non-native fish; maintain levels 

of turbidity that reduce predation by sight-feeding non-natives in the mainstem; improve 

spawning and rearing habitat for native fish in the mainstem, such as through creation of 

sediment-formed habitats such as backwaters); and controlling the spread of non-native 

species. All of these actions are poorly understood at the present time and will require 

additional monitoring and research. 

(4) Research the potential to control parasites and diseases. Additional monitoring 

and research is needed to determine the level of infestation and to examine the need to 

develop control methods. Warmer dam releases may increase the spread or impact of 

disease and parasites on humpback chub in the mainstem. 

(5) Translocation of humpback chub to other tributaries. Humpback chub have 

already been successfully translocated within the Little Colorado River above a natural 

barrier, Chute Falls. These translocated fish have become established, exhibited fast growth 

rates, and spawned, essentially increasing the range of the species by several kilometers 

within the Little Colorado River, and likely increasing the population size by several 

hundred fish or more (Stone 2006, 2007). Translocating humpback chub to other tributary 

streams within Grand Canyon, such as Havasu, Shinumo, Bright Angel creeks or the Paria 

River, could also result in new, successful populations, and should be investigated (Valdez 

et al. 2000, Stevens et al. 2006). A number of factors will have to be considered in 

translocation of humpback chub. For example, care must be taken to ensure that genetics of 

translocated populations are representative of the Grand Canyon population, and that 

translocation efforts do not result in overharvest of wild fish from the Little Colorado River 

aggregation. Genetic concerns regarding translocation should be addressed by development 

of a genetics management plan. 

(6) Consider the use of other management actions such as sediment/turbidity 

augmentation to disadvantage non-native fish and provide cover for native species. An 

experimental test of increased turbidity is could determine the ecological impacts of such 

augmentation, with particular regard to effects on sight-feeding predators of humpback chub 

and effects on fish food resources. Such tests could also be conducted ex situ in a laboratory 

setting. 

(7) Explore methods to reduce impacts from scientific and recreational uses. The 

recently completed Protocol Evaluation Panel on the AMP’s fish monitoring programs 

identify the need to continually modify sampling efforts to reduce the effect of handling 

stress on humpback chub. 

4.2 Reducing the Threat of Catastrophic Events 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 34

There is a risk of extirpation resulting from catastrophic events in the Little Colorado 

River, such as hazardous materials spills or dewatering of the regional aquifer supporting Blue 

Springs, because it is currently the primary spawning location for humpback chub in Grand 

Canyon, and is occupied by much of the population at any given time. Also, increasing water 

temperatures in the mainstem Colorado River and other management actions intended to benefit 

the humpback chub carry the risk of unintended consequences that may negatively affect the 

humpback chub population. 

The top priorities to protect against such risks are (1) expand the range of the population 

both above and below the Little Colorado River confluence (both mainstem and tributaries) so 

that a catastrophic event is less likely to negatively affect the entire population, (2) develop and 

implement an action plan to alleviate threats that may originate in the Little Colorado River 

watershed, including plans for early response to toxic spills, pollution control, and invasive 

species and (3) establish one or more refuge populations and/or captive breeding populations, 

consistent with a genetics management plan, for protection against the loss of the Grand Canyon 

population. 

4.3 Monitoring and Assessment 

Monitoring is a key component of adaptive management (Nyberg 1998, Walters 1986, 

Taylor et al. 1997) and monitoring of the Grand Canyon humpback chub population and its 

habitat and assessment of the trend in their status is essential to this plan. The AMP has already 

established a sufficient program of monitoring for fishes and the aquatic ecosystem. This 

program should continue, and continue to be evaluated in light of new information. 

Longstanding efforts to monitor the primary humpback chub aggregation in the Little Colorado 

River, and newer efforts to monitor fishes throughout Grand Canyon, including the reach 

between Diamond Creek and Lake Mead, should likewise continue. The AMP should also 

continue to monitor fish diseases and parasites, the aquatic food base, and Little Colorado River 

hydrology and water quality, to provide an extensive, integrated monitoring framework for 

humpback chub. The AMP should continue to maintain this level of monitoring effort, and 

continue to periodically evaluate monitoring protocols to improve their accuracy, precision, and 

consistency. Humpback chub demographic modeling should be consistent with U.S. Fish and 

Wildlife Service requirements. Comprehensive ecosystem models are necessary to test the 

tradeoffs inherent in different management alternatives and should be an important component of 

monitoring and assessment. 

5.0 STRATEGY IMPLEMENTATION - PROPOSED PROJECTS 

The first draft of this document, completed in 2003, utilized an approach that relied on a 

set of projects targeted at specific research needs or conservation actions identified by committee 

to implement the conservation strategy. We continue that approach here, and link them 

conceptually. This current iteration consists of 14 projects, listed in Table 1, that the Ad Hoc 

believes are necessary to conserve humpback chub in the Lower Colorado River Basin. Some 

projects are identified only at a feasibility level; that is, they are studies that will lead the way to 

evaluation and testing, likely as pilot projects, through the AMP adaptive management process to 

determine their utility in contributing to the recovery goals. Some projects are already funded 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 35

and are being implemented through the AMP by GCMRC either internally or through contracts. 

We provide project descriptions in Appendix B, including the project’s current status and 

expected completion timeframe. More detail on these projects can be found in work plans 

produced by GCMRC for fiscal year (FY) 2002-2009. Other projects outside the purview of the 

AMP would likely require funding as part of a recovery program for humpback chub in Lower 

Colorado River Basin. The Humpback Chub Implementation Ad Hoc will evaluate all of the 

projects for their potential inclusion in the AMP in a separate report. 

Table 1. Projects to facilitate conservation of the humpback chub in the Lower Colorado River 

Basin. 

1 Humpback Chub Genetics Management Plan 

2 Humpback Chub Refuge Creation 

3 Glen Canyon Dam Operations 

4 Glen Canyon Dam Selective Withdraw Structure 

5 Sediment Augmentation 

6 Aquatic Food Base Monitoring and Research 

7 Young Humpback Chub Habitat Enhancement in the Little Colorado River and other Grand 

Canyon Tributaries 

8 Fate of Young Humpback Chub in the Colorado River in Grand Canyon (Nearshore Ecology 

Study) 

9 Nonnative Control 

 a. Nonnative Control in Tributaries of the Colorado River in Grand Canyon 

 b. Nonnative Control Near the Mouth, and/or in the Lower 15 km, of the Little Colorado River 

 c. Develop Nonnative and Invasive Species Control Plan for the Grand Canyon Region 

 d. Develop Nonnative Stocking Procedures for Grand Canyon Region 

10 Effects of Scientific Work and Recreational Activities on Humpback Chub 

11 Monitoring and Control of Humpback Chub Diseases and Parasites 

12 Translocation of Native fishes in Grand Canyon 

 a. Translocation of Humpback Chub above Chute Falls in the Little Colorado River 

 b. Translocation of Native fish to Grand Canyon Tributaries other than the Little Colorado River 

13 Monitor Humpback Chub Population Dynamics, Distribution, and Habitat 

 a. Monitor Hydrology and Water Quality in the Little Colorado River 

 b. Maintain a Core Monitoring Effort for Humpback Chub in Grand Canyon 

 c. Monitor the Status and Trends of the Downstream Fish Community in Grand Canyon 

 d. Monitor the Status and Trends of Fishes below Diamond Creek 

14 Planning Documents to Assist Conservation of Humpback Chub 

 a. Develop Watershed Management Plan for the Little Colorado River 

 b. Develop Emergency Response/Contingency Plan for the Little Colorado River 

 c. Develop Pollution Control Plan for Little Colorado River 

5.1 Project Linkages, Sequences and Feedback Loops 

Defining the interaction of the projects is difficult because there is uncertainty associated 

with the threats to humpback chub with regard to their respective severity and interaction. Thus, 

the possible interaction of various projects is likewise difficult to determine. In addition, many 

of the projects are general in nature and may represent several separate projects when funded and 

implemented. However, we have attempted to provide this in Figure 1, which illustrates that 

projects fit into three categories that correspond to the overall conservation strategy: 1, those that 

serve to expand the range and/or survivorship of humpback chub; 2, those that reduce the threat 

of catastrophic events; and 3, those that provide monitoring and assessment of conservation 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 36

efforts. Within these categories, projects are in various stages of development, unfunded and/or 

not implemented, in a feasibility/research phase, or ongoing (see Figure 1). Project timing is also 

illustrated in this way, and is also provided in the status section of individual project synopses in 

Appendix B. 

Figure 1. Diagram illustrating linked elements of the conservation strategy for humpback chub in 

Grand Canyon, including associated projects and their status. 

5.2 Project Prioritization 

Numerous examples of how to prioritize and rank threats are provided in the National 

Marine Fisheries Service Interim Recovery Planning Handbook (2007a). Rarely is enough 

information available to rank threats based on numerical values. In almost all cases in recovery 

planning, agencies have resorted to using qualitative criteria based on expert opinion. Usually 

there is some data to weight the available evidence, but not to conduct an entire ranking analysis. 

A “weight of evidence” approach was used by NMFS to assess the relative impact of 

each threat (factor) in the most recent Steller Sea Lion Recovery Plan (NMFS 2008). This 

qualitative assessment approach was selected rather than a quantitative approach because of the 

substantial uncertainty in the understanding of each threat’s influence on sea lion population 

dynamics. Using the extensive expertise of the recovery team, they were able to identify three 

relative threat levels, Low, Medium, and High. 

The assessment allowed the development of a recovery strategy and prioritization of 

recovery actions. It is expected that in future plans that these threats will be more finely 

assessed. Although the rankings were developed to be relative to each other, a conceptual 

definition of each level is provided below: 

Expanding Range/Increasing Survival 

Ongoing Research 

3. Glen Canyon Dam Operations 

9. Nonnative Control 

12. Translocation of Native Fish in Grand Canyon 

(Little Colorado River and Shinumo Creek)

Expanding Range/Increasing Survival 

Ongoing Feasibility/Research 

4. Glen Canyon Dam Selective Withdraw Structure 

6. Aquatic Food Base Monitoring and Research 

8. Fate of Young Humpback Chub in the Colorado 

River in Grand Canyon 

10. Effects of Scientific Work and Recreational 

Activities on Humpback Chub 

11. Monitoring and Control of Humpback Chub 

Diseases and Parasites 

Reducing the Threat of Catastrophic Events 

Ongoin/Research 

1. Humpback Chub Genetics Management Plan 

2. Humpback Chub Refuge Creation (1 refuge) 

12. Translocation of Native Fish in Grand Canyon (Little 

Colorado River and Shinumo Creek)

Reducing the Threat of Catastrophic Events 

Not funded or initiated 

2. Humpback Chub Refuge Creation (additional refuges) 

14. Planning Documents to Assist Conservation of Humpback 

Chub 

Expanding Range/Increasing Survival 

Not funded or initiated 

5. Sediment Augmentation 

7. Young Humpback Chub Habitat Enhancement in 

Grand Canyon Tributaries 

12. Translocation of Native fishes in Grand Canyon 

(other Grand Canyon tributaries)

Monitoring and Assessment 

Ongoing 

6. Aquatic Food Base Monitoring and Research 

11. Monitoring and Control of Humpback Chub Diseases and 

Parasites 

13 Monitor Humpback Chub Population Dynamics, 

Distribution, and Habitat 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 37

High: a threat with substantial impacts to recovery requiring mitigation and/or further 

research to identify impacts 

Medium: a threat with moderate impacts which if mitigated could increase the likelihood 

of recovery, but in and of itself has limited impact on population trajectories 

Low: a source of mortality that likely has little impact on population trajectory 

NMFS used the following parameters to describe each threat: (1) the mechanism by 

which each threat operates (bottom-up, or top-down, or both); (2) the age-class most vulnerable 

to the threat; (3) the relative frequency that the threat occurs; (4) the uncertainty in the evidence 

used to determine the relative impact; and (5) the feasibility of mitigation. 

 The Ad Hoc conducted a similar exercise to help prioritize the projects. The 14 humpback 

chub projects were ranked using 5 criteria (on a scale of 1-5, 5 being best): benefit, cost, 

feasibility, learning, and timeframe. The results for the project rankings were summarized both 

unweighted and utilizing a weighted value for the “benefit” criteria, which provides a ranking 

that emphasizes the potential benefit of a project to humpback chub over the other criteria. The 

benefit-weighted ranking was the preferred ranking of the Ad Hoc. The rankings are presented in 

Appendix D, and are provided as guidance to assist in planning and budget development. 

However all 14 of the projects included in this report are considered to be important by the Ad 

Hoc, and are strongly recommended for consideration to support conservation of humpback 

chub. 

5.3 Reducing the Threat of Catastrophic Events 

The current humpback chub population in the lower Colorado River is primarily 

concentrated in the Little Colorado River (Paukert et al. 2006). For some time this has caused 

concern for managers because of the potential for an event that results in a severe population 

decline in humpback chub, such as a contaminant spill at one of the bridges that cross the Little 

Colorado River upstream of the population. Reducing this threat is a key component of the 

strategy of this plan. As discussed above, the plan includes mechanisms to protect against such 

risks by: expanding the range of the population in Grand Canyon; developing and implementing 

action plans to alleviate threats that may originate in the Little Colorado River watershed, 

including plans for early response to toxic spills, pollution control, and invasive species; and 

establishing one or more refuge populations and/or captive breeding populations, consistent with 

a genetics management plan, for protecting against the loss of the Grand Canyon population. 

There are four projects proposed in this plan that are key to achieving these strategy elements: 

Project 1, the Humpback Chub Genetics Management Plan; Project 2, Humpback Chub Refuge 

Creation; Project 9, Nonnative Control; and Project 14, Planning Documents to Assist 

Conservation of Humpback Chub. 

The Humpback Chub Genetics Management Plan will guide development of one or more 

refuge populations and/or captive breeding populations, as well as translocation of humpback 

chub to other areas, and ensure that these actions follow the U. S. Fish and Wildlife Service 

policy on controlled propagation (U.S. Fish and Wildlife Service 2000). A number of 

precautions must be employed when utilizing captive populations in conservation of a species. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 38

Development of broodstock should not compromise the viability of any extant aggregations (i.e., 

it may be appropriate only to collect gametes or young-of-year from the mainstem aggregations). 

Guidelines should be developed for creation and maintenance of refuge populations, and for 

translocation. Criteria must be developed to determine when stocking of captive bred individuals 

will be employed as a conservation action. The genetics management plan will be the guidance 

document for these actions. 

A refuge is defined as a place that provides shelter or protection, in the case of this plan, 

for humpback chub. The term refugium (pl., refugia) is often mistakenly used in this context (a 

refugium is a relict area of relatively unaltered climate that is inhabited by plants and animals 

during a period of continental-scale climatic change). The Ad Hoc recommends maintaining 

several refuge populations as a tool in conservation of Grand Canyon humpback chub to ensure 

species persistence and to protect against potentially catastrophic events until threats can be 

alleviated, habitat improved, and the range of humpback chub expanded to the point that low 

population levels and catastrophic events are no longer considered a threat. The Ad Hoc does 

not recommend stocking captive reared humpback chub into Grand Canyon at this time. 

Control of nonnative species, including a plan to control invasion of new nonnative 

species, will reduce the threat that nonnative species will lead to a catastrophic loss of humpback 

chub from Grand Canyon. There are also several planning documents proposed collectively as 

Project 14 that also serve to reduce the threat of catastrophic events. In particular, development 

of an emergency response plan for the Little Colorado River will provide a contingency plan to 

help address the threat of a contaminant spill. A Little Colorado River watershed management 

plan and pollution control plan, also recommended by the Ad Hoc, will also aid in reducing 

threats to critical habitat in the Little Colorado River. 

5.4 Implications of Implementation 

Implementation of management actions to benefit the humpback chub may impact other 

resources in Grand Canyon. These impacts may occur as a result of redirected efforts and 

funding for humpback chub research, monitoring, and management actions. Implementation of 

these actions must be consistent with the mission and management objectives of the AMP. 

Management actions recommended in this report are intended to complement and support the 

mission of AMP, but it is also recognized that implementing a part or all of these actions will 

likely require additional or different funding sources. 

6.0 Discussion 

The recent improvement in the status of the humpback chub in Grand Canyon provides 

an opportunity to learn about the causal factors that may be important in its recovery. Numerous 

factors, including cold water temperatures, have been identified as potential factors in the decline 

of the species and may be critical in its recovery. A number of management actions were tested 

during this period of recovery, including high flow and low steady flow testing, nonnative 

removal, and translocations. These activities may have contributed to the improvement in status 

and should continue to be evaluated for efficacy. Translocation in particular may be an important 

tool in expanding the range of humpback chub in Grand Canyon, particularly translocation into 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 39

tributaries. Tributary translocations should be considered in suitable streams to expand the range 

of spawning and rearing of humpback chub and to reduce the risk of extirpation in Grand 

Canyon due to a catastrophic event in the Little Colorado River. 

An important consideration for managers is that actions that may have positive benefits 

for some resources can also have negative consequences. For example, the low summer steady 

flow in 2000 created relatively warm water temperatures in the mainstem river (Andersen 2009), 

but low flows can adversely affect food base by limiting primary production (Kennedy and Gloss 

2005). Likewise, augmenting sediment to create turbidity could provide cover for native fishes 

and reduce predation from nonnative fish (Valdez and Ryel 1995), but increases in turbidity 

could also decrease food base by decreasing primary production (Blinn et al. 1992). The recent 

increase in humpback chub abundance (Andersen 2009) was likely driven in part by warmer 

water temperatures, which may have improved growth and survivorship of juvenile humpback 

chub in the mainstem river. However, warmer water temperatures may also benefit nonnative 

fishes (Valdez and Speas 2007), and any benefits to humpback chub could be negatively offset 

by losses to predation, especially if new nonnative species were to invade and become 

established. Nonnative removal has proven effective in removing trout, but the benefits of 

removing trout to humpback chub is uncertain (Coggins 2008), and other nonnative species are 

less susceptible to current capture methods and may pose a more significant predation risk to 

humpback chub (Arizona Game and Fish Department 2008). The efficacy of removing 

nonnative fishes to benefit humpback chub is still an open question, as is the most effective 

means of nonnative removal. Research should be implemented to provide insight into these 

questions and tradeoffs. This may entail rethinking the AMWG priority questions for humpback 

chub to focus attention on determining the causal factors of the recent positive population 

trajectory. 

Although many uncertainties remain with regard to the most efficient and cost-effective 

means to recover the humpback chub in Grand Canyon, ongoing research and management 

actions taken by the Adaptive Management Program may provide many important answers over 

the next 5-10 years. Clearly it will be a challenge to manage these tradeoffs within the Adaptive 

Management Program. Development of comprehensive models to further evaluate the effect of 

these treatments on humpback chub recruitment in an ecosystem context will be essential in this 

process. The goal of adaptive management is improved decision making through learning by 

doing (Williams et al. 2007). If implemented correctly, adaptive management will vastly 

improve the power of managers to make decisions that are not just effective, but are also lower 

risk and cost-effective (Williams et al. 2007). The Adaptive Management Program has made 

great strides in improving our understanding of how best to conserve humpback chub in the 

Grand Canyon. Important questions remain, but if recovery of humpback chub in Grand Canyon 

is to be successful, its best hope lies in the continued application of adaptive management. 

7.0 Conclusions 

The purpose of this plan is to compile information on the status of the Grand Canyon 

population of humpback chub (i.e. the lower basin recovery unit as defined by the U.S. Fish and 

Wildlife Service, 2008), summarize the threats to this population, and define a comprehensive 

strategy, which includes specific research and management actions, to improve the status of the 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 40

population and minimize or eliminate threats. The AMP was created by the Department of the 

Interior to ensure, as defined in Section 1802 of the Grand Canyon Protection Act, that Glen 

Canyon Dam is operated "... in such a manner as to protect, mitigate adverse impacts to, and 

improve the values for which Grand Canyon National Park and Glen Canyon National 

Recreation Area were established, including, but not limited to natural and cultural resources and 

visitor use." The AMWG directed that this report be updated to guide efforts to accomplish this 

for the humpback chub, although much of what is recommended in this report will also benefit 

other native species that occur in Marble and Grand canyons. Not all actions described here are 

necessarily the requirement of the AMP. A separate process will be used by the AMWG to 

determine what elements of this plan should be recommended to the Secretary for 

implementation by the AMP. 

The status of the Grand Canyon population of humpback chub appears to be improving 

following a significant decline. Adult population estimates for an age-structured Jolly–Seber 

model ranged from about 14,500 in 1989 to about 2,400 in 2001; a similar model, the ASMR, 

estimated population size from 10,000-11,000 adults in 1989 to 3,100-4,400 in 2001 (Coggins et 

al. 2006). The main cause for the decline appears to be a decline in recruitment such that adult 

mortality exceeds recruitment. Recent ASMR analyses indicate that the Grand Canyon 

population appears to have increased to 7,650 (CI 6,000-10,000), and that the decline in 

recruitment began to stabilize or reverse in the mid-1990s (Coggins and Walters 2009). New 

information also indicates that there are greater numbers of humpback chub in the mainstem 

Colorado River than in previous years (Johnstone and Lauretta 2004, 2007, Trammell et al. 2002, 

Arizona Game and Fish Department 1996, Ackerman et al. 2006, Ackerman 2007). The range 

and size of the Little Colorado River Inflow aggregation has also increased as a direct result of 

translocating humpback chub from the Little Colorado River above Chute Falls (a natural barrier 

waterfall) in the Little Colorado River approximately 16 km above the confluence. Results 

indicate that translocated fish had high survival and growth rates, and reproduction and 

downstream movement has been documented (Stone 2006), as well as recruitment into the adult 

population (Stone 2007). 

 The AMP has undertaken a number of actions to benefit humpback chub. In 2000, a low 

summer steady flow was conducted which significantly warmed mainstem Colorado River water 

temperatures (GCMRC unpublished data). From 2003 to 2006, nonnative fishes were removed 

using electrofishing from the Little Colorado River inflow reach. In 1996, 2004, and 2008 high 

flow tests were conducted to rebuild sand-formed habitats. Humpback chub were translocated 

within the Little Colorado River to improve growth and survival from 2003-2005 and in 2008. 

All of these actions met with some degree of success and likely provided a conservation benefit 

to the species. Additionally, Reclamation has undertaken a number of conservation measures as 

part of two biological opinions to conserve humpback chub (see Appendix F) many of which are 

recommended projects in this plan. 

While the recent increase in population size and stability of the Grand Canyon population 

of humpback chub has previously been attributed to increased recruitment resulting from warmer 

water temperatures, mechanical removal of nonnative piscivorous fish and/or experimental flows 

(high flow tests, steady flows in 2000), recent modeling suggests that initiation of increased 

recruitment predates each of these factors by at least four years (Coggins 2007, Coggins and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 41

Walters 2009). No explanations for this recruitment increase have been proposed to date. The 

increase could have been due to factors associated with the Little Colorado River, the 

mainchannel Colorado River, or both parts of the system. 

The Ad Hoc recommends working to further improve status of the humpback chub with a 

3 tiered strategy: (1) expanding the range of spawning and rearing in Grand Canyon, (2) 

increasing survival and recruitment, and (3) reducing the threat of catastrophic events or 

unintended consequences. Expanding the range of humpback chub and improving survival and 

recruitment can be achieved in numerous ways, but mainstem habitat conditions, and in 

particular, the water temperature of the mainstem and suitability of nearshore habitats for rearing 

young are likely most important, but nonnative species could offset these actions via predation 

and competition. Improving mainstem habitats for humpback chub will likely require 

modifications to the infrastructure or operations of Glen Canyon Dam, and prior actions by the 

AMP such as the 2000 Low Summer Steady Flow have contributed to our learning in this regard. 

The Ad Hoc agrees with previous assessments (U.S. Geological Survey 2008a) that any efforts to 

modify Glen Canyon Dam address the capability to release both warm and cold water as needed 

to better address the threat of inadvertently benefitting warm water nonnative species. We note 

that global climate change may also warm the Colorado River (USCCP 2008). New initiatives to 

reduce the threat of catastrophic events recommended in this report are currently underway, such 

as creation of a humpback chub refuge, but additional efforts are needed, such as the longstanding need to develop an emergency response/contingency plan for protection of the 

downstream ecosystem from contaminant spills into the Little Colorado River at Cameron 

Bridge or other potential sites. Controlling nonnative species continues to be identified as the 

most critical need for this species. Preventing the invasion and expansion of nonnative species is 

likely the most important and difficult action required for the continued conservation of 

humpback chub. 

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Draft Humpback Chub Comprehensive Plan – June 16, 2009 59

APPENDIX A: Members of the Humpback Chub Comprehensive Plan Ad Hoc Group

Name Affiliation E-mail Address 

Dennis Kubly Bureau of Reclamation dkubly@uc.usbr.gov 

Larry Stevens Grand Canyon Wildlands Council farvana@commspeed.com 

Bill Persons Arizona Game and Fish 

Department 

bpersons@azgfd.gov 

Gary Burton Western Area Power Admin. burton@wapa.gov 

Shane Capron Western Area Power Admin. capron@wapa.gov 

Mark Steffen Federation of Fly Fishers steffenflyrod@lycos.com 

Pam Sponholtz U.S. Fish and Wildlife Service pam_sponholtz@fws.gov 

Kerry Christensen Hualapai Tribe cuszhmann@yahoo.com

Norm Henderson National Park Service Norm Henderson@nps.gov 

Steve Mietz National Park Service Ken McMullen@nps.gov 

Bill Davis Ecoplan, Colorado River Energy 

Distributors Aassociation 

wdavis@ecoplanaz.com 

Matthew Andersen U.S. Geological Survey mandersen@usgs.gov 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 60

APPENDIX B: Project Synopses 

Projects to Facilitate Conservation of the Federally Endangered Humpback 

Chub (Gila cypha) in the Lower Colorado River Basin 

The Adaptive Management Workgroup of the Glen Canyon Dam Adaptive Management 

Program (AMP) commissioned a Humpback Chub Ad Hoc Committee in early 2003 to develop 

a comprehensive suite of proposed projects or management actions believed necessary to ensure 

conservation of the humpback chub in the lower Colorado River basin (i.e. the lower Colorado 

River basin recovery unit in the U.S. Fish and Wildlife Service draft Humpback Chub Recovery 

Goals 2008 Revisions). 

This document represents the latest edition of the report to the AMP, and, like previous versions, 

lists and describes projects deemed necessary to ensure recovery of the humpback chub in the 

lower Colorado River basin. The projects have been updated by the Ad Hoc. This document 

contains synopses of the projects organized in a manner that groups related projects, provides an 

update on their implementation status, and suggests an appropriate sequence for their 

implementation. Although these projects are designed with humpback chub specifically in mind, 

other native fishes should also benefit. Some of these proposed projects have already been 

accepted and are underway or completed. Some projects are outside the scope of the AMP and 

may need to be addressed by other processes. 

Project Synopses 

Genetic, Augmentation and Hatchery Considerations. Developing an effective recovery 

strategy for a species requires a thorough understanding of its genetic characteristics and 

relationships among populations. Genetic information will be assimilated and utilized in 

developing a genetics management plan. The genetic management plan will be used to guide 

recovery efforts and management actions, such as projects that enhance species recovery or 

safeguard against catastrophic loss of a single population. 

01. Develop and implement a genetics management plan for humpback chub in Grand 

Canyon. 

Propagation and genetics management is one of the seven elements of the Upper Colorado 

Endangered Fish Recovery Program. Guidance for controlled propagation of federally listed 

species has been promulgated by the U. S. Fish and Wildlife Service (2000). A genetics 

management plan is a necessary precursor to several elements of genetic management for 

humpback chub: translocation, refuge creation, captive grow-out of wild caught fish, or 

stocking from captive breeding stocks. Such a plan has been developed for populations of 

humpback chub and the other three big river endangered fish for use in the Upper Colorado 

Endangered Fish Recovery Program (Czapla 1999), but no corollary plan has been finalized 

for humpback chub in Grand Canyon. The Upper Colorado plan: (1) identifies and classifies 

endangered fish stocks, (2) describes criteria for decisions related to genetics management, 

(3) establishes priorities for effective and rational genetics management for species and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 61

stocks, and (4) recommends management actions by species and stocks. The genetics 

management plan for humpback chub in Grand Canyon should be in place and be used for 

planning: (1) removal of humpback chub for creation of refuge populations; (2) translocation 

of humpback chub to other tributaries in Grand Canyon; (3) or for captive propagation of 

individuals as a source for restocking. 

Several projects recently completed by the AMP will aid development of the genetics 

management plan. Douglas and Douglas (2007) recently completed a study evaluating the 

interrelationships among populations of the endangered Gila cypha within Grand Canyon. 

This report helps identify genetic distinctiveness of aggregations in the mainstem Colorado 

River, their interrelationships, and how they can be adaptively managed in a dam-perturbed 

environment. Dexter National Fish Hatchery has also recently completed a study analyzing 

the genetic makeup of approximately 75 humpback chub housed at Willow Beach National 

Fish hatchery. This assessment will be useful in determining the genetic value of these fish to 

recovery of humpback chub. The Pinetop Fishery Resources Center has completed a report 

entitled “The Feasibility of Developing a Program to Augment the Population of Humpback 

Chub (Gila cypha) in Grand Canyon” (Van Haverbeke and Simmonds 2003). This document 

provides a valuable assessment of the benefits and risks associated with three potential 

methods of augmenting humpback chub populations: (1) captive propagation of wild caught 

individuals removed from the Little Colorado River to a hatchery facility to produce progeny 

for restocking; (2) removing wild caught young-of-year humpback chub from the Little 

Colorado River to a grow-out facility and rearing them to a large size in captivity and then 

restocking them; and, (3) translocation of wild caught humpback chub upstream to 

unoccupied habitat in the Little Colorado River and from the Little Colorado River to other 

tributaries. The Arizona Game and Fish Department has recently completed an evaluation of 

hatcheries, aquaria, and established refuge facilities within the United States as potential 

refuge locations for humpback chub from Grand Canyon (Childs 2005). This suite of 

projects, all contributed by the AMP or by AMP stakeholders, will be important in 

development of the genetics management plan. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.4 – Establish humpback chub spawning 

aggregations outside the Little Colorado River in the Colorado River ecosystem below Glen 

Canyon Dam to remove jeopardy. 

Humpback Chub Recovery Goals

Downlisting and delisting of humpback chub require demographically and genetically viable 

populations. A genetics management plan is a necessary precursor to developing refuge 

populations and stocking from captive breeding stocks to augment declining wild populations 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 62

of humpback chub and is a component of the propagation and genetics management segment 

of the Upper Basin Endangered Fish Recovery Program. 

Status: Dexter National Fish Hatchery is expected to complete the Genetics Management 

Plan in 2009. 

02. Create one or more refuge populations of humpback chub. 

The Ad Hoc recommends that off-river refuges that replicate the diversity of the wild 

population be created for the Grand Canyon population of humpback chub to protect the 

genetic integrity of this population. Young humpback chub have been abundant recently in 

the lower reach of the Little Colorado River. These fish are subject to high mortality. 

Collection of young humpback chub for use in a refuge population at such times when they 

are abundant will provide a safeguard against future catastrophic loss with very low risk to 

the overall population from collection and removal. This project will: 1) refine the methods 

for translocation of wild caught humpback chub to a refuge facility; 2) refine the methods for 

holding humpback chub in captivity; 3) establish one or more refuges to protect the genetic 

integrity of wild humpback chub from the Grand Canyon population; 4) potentially provide a 

source of humpback chub for use in ex-situ experiments (either from progeny or replacement 

of senescent individuals). 

The humpback chub genetics management plan will provide specific information on how to 

best create and maintain refuge populations with regard to numbers of humpback chub 

necessary to maintain genetic integrity in a refuge population that is representative of the 

wild population. However, the genetics management plan is not necessary as a precursor to 

begin this project. Efforts could begin prior to completion of the genetics management plan 

as multiple collections of humpback chub are anticipated. Preliminary research suggests that 

collections of young humpback chub at the mouth of the Little Colorado River are 

representative at least of the Little Colorado River aggregation, the primary aggregation in 

need of protection. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.4 – Establish humpback chub spawning 

aggregations outside the Little Colorado River in the Colorado River ecosystem below Glen 

Canyon Dam to remove jeopardy. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Humpback Chub Refuge – Once appropriate planning documents are in place, and refuge 

populations of humpback chub are created (as a conservation measure of the Shortage 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 63

Guidelines biological opinion), Reclamation will assist FWS in maintenance of a humpback 

chub refuge population at a Federal hatchery or other appropriate facility by providing 

funding to assist in annual maintenance. In case of a catastrophic loss of the Grand Canyon 

population of humpback chub, a humpback chub refuge will provide a permanent source of 

sufficient numbers of genetically representative stock for repatriating the species. This 

action would also be an important step toward attaining recovery. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Humpback Chub Refuge – Reclamation will assist FWS in development and funding of a 

broodstock management plan and creation and maintenance of a humpback chub refuge 

population at a Federal hatchery or other appropriate facility by providing expedited 

advancement of $200,000 in funding to the FWS during CY 2008; this amount shall be 

funded from, and within, the amount identified in the MSCP BO (FWS 2005a; page 26). 

Creation of a humpback chub refuge will reduce or eliminate the potential for a catastrophic 

loss of the Grand Canyon population of humpback chub by providing a permanent source of 

genetically representative stock for repatriating the species. 

Humpback Chub Recovery Goals

Downlisting and delisting of humpback chub require demographically and genetically viable 

populations. Refuge populations of humpback chub are needed to ensure that a source of fish 

is available should captive propagation and repatriation of captive breed individuals becomes 

necessary due to some unforeseen catastrophic loss of the Grand Canyon population. 

Status: The Fish and Wildlife Service, Arizona Game and Fish Department, and the Hualapai 

Nation have initiated a project to create a refuge population of humpback chub on Hualapai 

tribal lands. Juvenile humpback chub were removed from the Little Colorado River in 2008 

and are currently being maintained at Dexter National Fishery. Future collections will be 

needed to augment and maintain this new refuge.

In Situ Conservation The placement and operation of Glen Canyon Dam and the introduction, 

invasion, and establishment of nonnative organisms are strongly implicated as causes of the 

decline of humpback chub in Grand Canyon. These projects explore the extent to which these 

factors may be mitigated to improve habitats in Grand Canyon in support a self-sustaining 

population of humpback chub. 

03. Use dam operations, or mitigate the effects of dam operations, to benefit humpback 

chub. 

The operation of Glen Canyon Dam is thought to directly and indirectly affect the 

endangered humpback chub (U.S. Fish and Wildlife Service 2008a, 2008b; U.S. Geological 

Survey 2008b). There are linkages between such variables as flow, temperature, sediment, 

flow, food base, native/nonnative species interactions, and water quality. Since 1996, the 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 64

AMP has conducted a number of ecosystem experiments designed to test specific physical 

and biological hypotheses (e.g. 1996 Beach/Habitat Building Flow, 1997 and 1999 Habitat 

Maintenance Flows, 2000 Low Steady Summer Flow, the 2003-2006 experimental removal 

of nonnative fishes from the mouth of the Little Colorado River, the 2004 and 2008 High 

Flow Tests). These experiments not only investigated the ecosystem reaction to flow 

perturbations, but also attempted to determine what habitat conditions are necessary to 

sustain a recovered population of humpback chub. The AMP should continue to propose and 

support dam operation experiments to benefit humpback chub through adaptive management. 

The current experiment is to test the Modified Low Fluctuating Flow in concert with the 

2008 high flow test and steady flows in September and October from 2008-2012. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Humpback Chub Recovery Goals

 

5.2.2.1 Factor A. – Adequate habitat and range for recovered populations provided 

Management Action A-1 – Investigate the role of the mainstem Colorado River in 

maintaining the Grand Canyon humpback chub population and provide appropriate habitats 

in the mainstem as necessary for recovery. 

 Task A-1.1 – Identify life stages and habitats of humpback chub in the mainstem 

Colorado River and determine the relationship between individuals in the mainstem 

Colorado River and Little Colorado River. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1). 

Management Action A-2 – Provide flows necessary for all life stages of humpback chub to 

support a recovered Grand Canyon population, based on demographic criteria. 

 Task A-2.1 – As determined necessary and feasible, continue to operate Glen Canyon 

Dam water releases under adaptive management to benefit humpback chub in the 

mainstem Colorado River through Grand Canyon. 

 Task A-2.3 – Provide flow regimes (as determined under Tasks A-2.1 and A-2.2 that are 

necessary for all life stages of humpback chub to support a recovered Grand Canyon 

population. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 65

Status: Reclamation has committed to implement a program of experimentation to benefit 

the humpback chub through the AMP. The current experiment is to test the Modified Low 

Fluctuating Flow in concert with the 2008 high flow test and steady flows in September and 

October from 2008-2012. 

04. Complete feasibility study of the selective withdrawal structure on Glen Canyon Dam. 

Cold-water releases from Glen Canyon Dam are below optimal for the existing trout fishery 

and far below those temperatures needed to allow the humpback chub to thrive in the 

mainstem of the Colorado River. Cold-water releases may improve the efficiency of trout 

preying on young, native, warm-water fish. Thermal shock from cold mainstem temperatures 

has been recognized as a likely cause of mortality for young endangered fish leaving 

seasonally warmed tributaries, and growth of humpback chub is markedly decreased in cold 

mainstem waters (Valdez and Carothers 1999). Increasing the temperature of dam releases 

could be an effective tool to reduce thermal shock and improve growth, survival, and 

recruitment of humpback chub that descend the Little Colorado River to the mainstem. 

The 2000 Low Summer Steady Flow resulted in significant warming in the mainstem 

Colorado River downstream of Glen Canyon Dam. Since 2000, drought has resulted in the 

decline of Lake Powell elevation to a level where increased temperatures of dam releases are 

being documented. Recent positive changes in the status of humpback chub have coincided 

with this warming. Catch-rate data from near the confluence of the Colorado and Little 

Colorado rivers, and from in middle and lower Marble Canyon, indicate an increased 

abundance of juvenile humpback chub since 2003 and an overall increase in recruitment, 

possibly since the late 1990s (Coggins and Walters 2009), suggesting more favorable 

conditions for spawning and incubation in these reaches. Continued monitoring of these 

warmer temperatures may provide important insights into the effects of these physical 

parameters on humpback chub. 

Warming the Colorado River could have unintended negative consequences by improving 

conditions for warm-water nonnative fish, increasing diseases and parasites, and affecting the 

artificially cold-adapted food base of algae and aquatic invertebrates. However, the Science 

Advisors to the AMP evaluated these risks and concluded that there is adequate potential 

benefit to justify modifying Glen Canyon Dam and testing a selective withdrawal structure, 

particularly if actions are developed to mitigate subsequent negative consequences (Baron et 

al. 2003), stating: “The Advisors think sufficient knowledge exists to make an informed 

policy decision about proceeding or not proceeding with this adaptive management option. 

That decision would be for the AMWG to move forward as rapidly as possible with an 

Adaptive Management Program that incorporates construction and operation of a TCD 

[temperature control device] at Glen Canyon Dam.” A GCMRC- led knowledge assessment 

workshop in 2005 also concluded that warmer water might benefit all life stages of 

humpback chub (Melis et al. 2006b). However, in a workshop conducted by GCMRC in 

April of 2007, a panel of scientists concluded that a selective withdrawal structure should be 

only be built if it hast the capability to release both cool water and warm water to address the 

potential threat of expansion of warm-water nonnative aquatic species (U.S. Geological 

Survey 2008a). The capability to design and build a selective withdrawal structure that can 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 66

release both cool and warm water at a wide range of Lake Powell reservoir elevations has not 

been assessed by the Bureau of Reclamation. 

The Humpback Chub Comprehensive Plan Ad Hoc recommends that the AMP continue 

intensive study of the effects of warmer water on the Colorado River ecosystem and 

humpback chub below Glen Canyon Dam, utilizing laboratory study and in situ study of 

warmer water due to drought and low reservoir levels in Lake Powell, and that the AMP 

recommend to the Secretary’s designee that the Bureau of Reclamation proceed with 

compliance, building, and testing of a selective withdrawal structure on Glen Canyon Dam if 

the capability exists to deliver both cold and warm water at as wide a range of Lake Powell 

elevations as possible. 

Relationship to Programs:

Adaptive Management Program

Strategic Plan, Management Objective 7.1 – Attain water temperature ranges and seasonal 

variability in the mainstem necessary to maintain or attain desired levels of desirable 

biological resources (e.g., native fish, foodbase and trout). 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 

Humpback Chub Recovery Goals

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided 

Management Action A-3. - Investigate the anticipated effects of and options for providing 

warmer water temperatures in the mainstem Colorado River through Grand Canyon that 

would allow for range expansion of the Grand Canyon humpback chub population and 

provide appropriate water temperatures if determined feasible and necessary for recovery. 

Task A-3.1 - Determine the effects and feasibility of a temperature control device for 

Glen Canyon Dam under the Glen Canyon Dam Adaptive Management Program 

(U.S. Bureau of Reclamation 1999) to increase water temperatures in the mainstem 

Colorado River through Grand Canyon that would allow for range expansion of 

humpback chub. 

 Task A-3.1.2. - Implement a temperature control device for Glen Canyon Dam if 

determined feasible and necessary for recovery of humpback chub. 

Status: There are no current efforts to plan or test a selective withdrawal structure at Glen 

Canyon Dam. 

05. Sediment augmentation to benefit native fish (e.g. sediment pipeline from Lake Powell), 

both long-term feasibility and short term experiment. 

This project has two components: (1) evaluate the effects of increased turbidity or an 

extension of the period of turbidity on interactions between native and nonnative fish 

experimentally, either in a laboratory setting or in situ in the Colorado River, potentially at 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 67

the mouth of the Paria River or the mouth of the Little Colorado River; and, (2) evaluate the 

potential for delivering sufficient amounts of fine sediment to reverse the present decline of 

these sediments in Marble Canyon and thus increase mainstem turbidity. An experimental 

test of increased turbidity is proposed to determine the ecological impacts of such 

augmentation, with particular regard to effects on sight-feeding predators of humpback chub 

and effects on fish food resources. Turbidity will either be tested in a laboratory setting or by 

increasing turbidity in situ, for example through additions of fine sediments in the reach 

below the Paria River. Turbidity could be tested in situ either via small or large-scale 

experiments. The latter would require a significant compliance effort. 

Relationship to Programs: 

Humpback Chub Recovery Goals 

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided. 

Management Action A-1 - Investigate the role of the mainstem Colorado River in maintaining 

the Grand Canyon humpback chub population and provide appropriate habitats in the 

mainstem as necessary for recovery. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1 [of the Recovery Goals]). 

Status: The Bureau of Reclamation completed a feasibility assessment for large-scale 

sediment augmentation in 2002 that concluded such a project is feasible, though costs were 

estimated at $140 million for construction and $3.6 million annually for operation. Other 

aspects of this project have not been funded or implemented. 

06. Examine the effects of flows, temperature, and sediment on food base, and protect and 

improve food base for humpback chub. 

The importance of the linked aquatic-terrestrial food base on the distribution, condition, and 

abundance of native fish, including humpback chub, is poorly understood. Are Grand 

Canyon fish food-limited, and if so, what foods are important and can dam operations be 

used to improve food availability? Past and present efforts have focused on the reach-varying 

structure and seasonal variation in lower trophic level biomass and production in relation to 

dam operations and turbidity. Some research has suggested relationships between aquatic 

food base and nonnative trout growth in upper reaches of the study area; however, little 

critical linkage has been established between the aquatic food base and native fish population 

dynamics downstream from Lees Ferry. 

Several topics require direct measurement before comprehensive food base-fisheries 

modeling can be achieved. First, it is important to understand seasonal and interannual 

distribution, population dynamics, and variation in the diets of larval, young, subadult, and 

adult age classes of all important native and nonnative fish species. Next, additional 

taxonomic information and physical habitat requirements are needed of the primary 

producers and consumers. Third, thorough quantification of the structure, density, and 

production/delivery of aquatic algae and invertebrates, terrestrial leaf litter, and invertebrates 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 68

is needed. With the above information in hand, it will then be possible to frame experiments 

to test the role of dam flows and temperature on food base limitations on native and 

nonnative fish populations. Appropriate laboratory and small scale in situ experiments should 

be undertaken to construct and test interacting life history models for the important fish 

species in relation to their food base. Enhanced plankton delivery rates are anticipated from 

the selective withdrawal structure, and the consequences of increased food availability on 

interactions among native and nonnative fish species also deserves experimental exploration 

and monitoring. Such investigations will greatly improve predictive modeling of flows and 

temperature on fish population dynamics. 

The resulting trophically-based, multi-species fish population model can be used to run 

various scenarios of dam and natural flow and temperature variation on the food base and 

fisheries responses. Such modeling will establish the degree to which fish are limited by food 

resources, by either low production at the base of the food web or via shunting of energy to 

nonnative animals such as New Zealand mudsnails or rainbow trout. This information will 

provide guidance to managers considering various management options, and will establish 

baselines for use in comparing the effects of experimental treatments of varying flows, 

temperatures, and turbidities, and their interactions on native and nonnative fisheries. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 1.3 – Maintain or attain biomass and composition of 

primary producers (algae, diatoms, and macrophytes) on cobble bars in the mainstem 

Colorado River below the Paria River. 

Strategic Plan, Management Objective 1.4 – Maintain or attain biomass and composition of 

benthic invertebrates on cobble bars in the mainstem Colorado River below the Paria River. 

Strategic Plan, Management Objective 1.5 – Maintain or attain abundance of food base drift 

on cobble bars in the mainstem Colorado River below the Paria River. 

Humpback Chub Recovery Goals 

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided. 

Management Action A-1 - Investigate the role of the mainstem Colorado River in maintaining 

the Grand Canyon humpback chub population and provide appropriate habitats in the 

mainstem as necessary for recovery. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1 [of the Recovery Goals]). 

Status: Portions of this project are currently underway and should be completed in 2009. 

07. Examine the use of young humpback chub habitat enhancement in the Little Colorado 

River or other tributaries in Grand Canyon.
Draft Humpback Chub Comprehensive Plan – June 16, 2009 69

This project proposes to conduct an investigation into the feasibility of temporarily 

modifying tributary shorelines to improve in-tributary rearing of native fish, particularly 

native cyprinids and humpback chub. The Little Colorado River and other tributaries have 

relatively little shoreline slackwater or backwater habitat. This project will test the utility of 

shoreline modification using rock and/or inflatable shoreline dams to construct slackwater 

habitats, and determine whether such efforts can be used to: 1) increase the retention of 

young native fish in the tributary; 2) increase in-tributary growth of native fish; and 3) reduce 

population losses due to drift into the mainstem and consequent thermal shock. In addition, 

the role of water depth, shading, and other microsite conditions will be tested. Surrogate 

species may be considered prior to testing on humpback chub. Such efforts may be used to 

replicate or restore, to a limited extent, the ponding of the Little Colorado River that occurred 

during mainstem floods, and to determine whether such microsite restoration efforts can 

improve growth and survival of young native fish, particularly humpback chub. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Humpback Chub Recovery Goals 

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided. 

Management Action A-1 - Investigate the role of the mainstem Colorado River in maintaining 

the Grand Canyon humpback chub population and provide appropriate habitats in the 

mainstem as necessary for recovery. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1 [of the Recovery Goals]). 

Status: This project has not been funded or implemented. 

08. Study the fate of young humpback chub in the Colorado River in Grand Canyon 

(Nearshore Ecology Study). 

Losses of young humpback chub produced in the Little Colorado River are widely regarded 

as limiting to growth and expansion of the Grand Canyon humpback chub population. 

Humpback chub are believed to enter the mainstem Colorado River between 1 and 12 months 

after hatching, where survival is very low. Suboptimal summertime river temperatures, lack 

of suitable habitat, and predation by and competition from nonnative fishes are all thought to 

play a role in the poor survival of humpback chub in the mainstem, but the most important 

limiting factor or factors are not definitively known. Critical science questions presented in 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 70

GCMRC planning documents (i.e. Strategic Science Plan, and the Monitoring and Research 

Plan; examples below) address these information needs. Increasing the understanding of the 

causes for loss of young humpback chub in the mainstem would be of great value to 

managers and scientists seeking to protect and expand this population. 

This project recommends that GCMRC, in coordination with appropriate Technical Work 

Group members, develop a work plan that addresses critical science questions to serve as the 

basis for a request for proposals (RFP) to study the fate of young humpback chub in the 

Colorado River in Grand Canyon. The primary objective of the project will be to determine 

where and why young humpback chub are usually lost after being produced in the Little 

Colorado River. 

Critical Science Questions: 

Strategic Science Question 1-1: To what extent are adult populations of native fish controlled 

by production of young fish from tributaries, spawning and incubation in the mainstem, 

survival of young-of-year and juvenile stages in the mainstem, or by changes in growth and 

maturation in the adult population as influenced by mainstem conditions? 

Science Advisors humpback chub 1: What are the most limiting factors to successful 

humpback chub adult recruitment in the mainstem: spawning success, predation on YOY and 

juveniles, habitat (water, temperature), pathogens, adult maturation, food availability, 

competition? 

SSQ 5-6: Do the potential benefits of improved rearing habitat (warmer, more stable, more 

backwater and vegetated shorelines, more food) outweigh negative impacts due to increases 

in nonnative fish abundance? 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Humpback Chub Recovery Goals

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided. 

Management Action A-1 - Investigate the role of the mainstem Colorado River in maintaining 

the Grand Canyon humpback chub population and provide appropriate habitats in the 

mainstem as necessary for recovery. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1 [of the Recovery Goals]). 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures
Draft Humpback Chub Comprehensive Plan – June 16, 2009 71

Humpback Chub Nearshore Ecology Study – In coordination with other DOI AMP 

participants and through the AMP, Reclamation will implement a nearshore ecology study 

that will relate river flow variables to ecological attributes of nearshore habitats (velocity, 

depth, temperature, productivity, etc.) and the relative importance of such habitat conditions 

to important life stages of native and nonnative fishes. This study will incorporate planned 

science activities for evaluating the high flow test on nearshore habitats as well as the 5-year 

period of steady flow releases in September and October. A research plan will be developed 

with FWS via the AMP for this study by August 1, 2008, and a 5-year review report will be 

completed by 2013. The plan will include monitoring of sufficient intensity to ensure 

significant relationships can be established, as acceptable to the FWS. This conservation 

measure is consistent with the Sediment Research conservation measure in the Shortage 

Guidelines biological opinion. This study will help clarify the relationship between flows 

and mainstem habitat characteristics and availability for young-of-year and juvenile 

humpback chub, other native fish, and competitive or predaceous nonnative fish, and support 

continued management to sustain mainstem aggregations. The feasibility and effectiveness 

of marking small humpback chub (<150 and <100 mm TL [5.91 and 3.93 in]) will also be 

evaluated as part of the study, and if effective, marking young fish will be utilized in the 

study. Marking young humpback chub, if feasible and effective, could greatly aid in 

developing information on the early life history, growth and survival of young humpback 

chub. 

Status: This project is funded in the GCMRC work plan for fiscal years 2009. 

09. Control nonnative fish to reduce their predation on/competition with humpback 

chub. 

 a. Evaluate and, if feasible, control nonnative fish in selected tributaries of the Colorado 

River in Grand Canyon National Park and tribal lands. 

This project is designed to explore the feasibility of removing nonnative fishes from 

tributaries of the Colorado River in Grand Canyon that may include the Little Colorado 

River, Bright Angel Creek, Tapeats Creek, Havasu Creek, Shinumo Creek and Kanab Creek. 

Reduction of nonnatives is a necessary precursor for translocation of humpback chub and for 

supporting other native fishes in these streams. Nonnatives that will be targeted include 

salmonids, carp, channel catfish, and yellow and black bullhead, but may include other 

nonnatives as well. The level of control necessary to reduce nonnatives, including most 

efficient removal methods, including reduction of by-catch and how long suppression lasts, 

will be investigated. Removal equipment will include trammel nets, fyke nets, hoop nets, 

hook-and-line, and weirs at the mouths of tributaries. Feasibility of electroshocking using 

canoes, rafts and backpack units will also be explored as it relates to species-specific capture 

frequencies and minimization of incidental by-catch. Feasibility of using chemical fish 

toxicants, such as rotenone or antimycin, will also be evaluated. Sample size will be related 

to initial capture densities and be modified based on success or failure of a particular method. 

Relationship to Programs: 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 72

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Strategic Plan, Management Objective 2.4 – Establish humpback chub spawning 

aggregations outside the Little Colorado River in the Colorado River ecosystem below Glen 

Canyon Dam to remove jeopardy. 

Strategic Plan, Management Objective 2.6 – Reduce native fish mortality due to nonnative 

fish predation so that it does not impinge on viability. 

 Humpback Chub Recovery Goals

5.2.2.3 Factor C: – Adequate protection from diseases and predation. 

Management Action C-3 – Control problematic nonnative fishes as needed. 

Task C-3.1 – Develop rainbow trout, channel catfish, black bullhead, and common carp 

control programs in the Little Colorado River to identify levels of control that will 

minimize predation on humpback chub (see section 4.3.2 and A.8 for discussion of 

effects of nonnative fishes). 

Task C-3.2 – Implement identified levels (as determined under Task C-3.1) of rainbow 

trout, channel catfish, black bullhead, and common carp control in the Little Colorado 

River.

Task C-3.3: – Brown trout and rainbow trout control programs developed and 

implemented to identify levels of control that will minimize predation on humpback chub 

in the Colorado River through Grand Canyon. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 73

Status: The project is currently being funded and implemented by the National Park Service 

in Shinumo creek with assistance from the Bureau of Reclamation and AMP. 

 b. Mechanical removal of nonnative fishes from the Colorado River and Little Colorado 

River. 

A hypothesized factor in the decline in humpback chub recruitment in recent years is 

negative interactions (predation and competition) with nonnative fish. Interaction with 

nonnative fish is implicated in the decline and extinction of native fishes throughout the 

Colorado River Basin. Increased recruitment of rainbow and brown trout occurred during 

operation of Glen Canyon Dam under Modified Low Fluctuating Flows, the preferred 

alternative of the Glen Canyon Dam EIS, and populations in the Colorado River increased 

dramatically. This project is the continuation of a multi-objective study to evaluate the 

potential effect of rainbow and brown trout predation on humpback chub recruitment and the 

efficacy of mechanical removal of rainbow and brown trout from the Little Colorado River 

inflow reach (GCMRC 2003b). Non-native fishes were removed from a 17-mile stretch of 

the mainstem Colorado River using boat-mounted electrofishing units. Reduction efforts took 

place in 2003 – 2006 as part of a long-term experimental design to test the benefit to 

humpback chub. Efforts are also being directed at evaluating control methods for other nonnative fishes such as common carp, channel catfish, black bullhead, and small-bodied 

nonnative species such as red shiner. Efforts will also consider bioenergetic community 

interactions of fish species to better select those species that pose the greatest risk to native 

fishes and to humpback chub, as well as the geospatial proximity and vagility of potential 

predators and competitors. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Strategic Plan, Management Objective 2.6 – Reduce native fish mortality due to nonnative 

fish predation so that it does not impinge on viability. 

Humpback Chub Recovery Goals

5.2.2.3 Factor C: – Adequate protection from diseases and predation. 

Management Action C-3 – Control problematic nonnative fishes as needed. 

Task C-3.1 – Develop rainbow trout, channel catfish, black bullhead, and common carp 

control programs in the Little Colorado River to identify levels of control that will 

minimize predation on humpback chub (see section 4.3.2 and A.8 for discussion of 

effects of nonnative fishes). 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 74

Task C-3.2 – Implement identified levels (as determined under Task C-3.1) of rainbow 

trout, channel catfish, black bullhead, and common carp control in the Little Colorado 

River.

Task C-3.3: - Brown trout and rainbow trout control programs developed and 

implemented to identify levels of control that will minimize predation on humpback chub 

in the Colorado River through Grand Canyon. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Nonnative Fish Control – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue efforts to control both cold- and warm-water nonnative fish 

species in the mainstem of Marble and Grand canyons, including determining and 

implementing levels of nonnative fish control as necessary. Control of these species using 

mechanical removal and other methods will help to reduce this threat. 

Status: This project is funded for implementation through the AMP in 2009 following a two 

year hiatus. Preliminary survey data indicate an increase in trout numbers in the Little 

Colorado River inflow reach. Results from 2003-2006 removal efforts indicate that the 

program was highly effective at removing rainbow trout, and increases in humpback chub 

may be due in part to this removal. GCMRC continues to test efforts to better remove other 

nonnative species. 

c. Develop a nonnative and invasive species control plan for the Colorado River 

ecosystem, Grand Canyon region. 

The continued introduction of aquatic invasive species in the Colorado River poses a serious 

threat to aquatic resources and an already imperiled fauna. These non-native plants and 

animals are transported into and throughout the Colorado River via recreational boating, 

fisherman, researchers, through the release of unwanted aquarium contents, or a variety of 

other transport vectors related to human activities. Because they have few natural controls in 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 75

their new environments, these species have great potential for rapid colonization and are 

already having significant impacts on the biodiversity and integrity of aquatic habitats in the 

Lower Colorado River, e.g. Giant salvinia and quagga mussel. Many of the tributaries to the 

Colorado River in Grand Canyon originate in Grand Canyon National Park, and therefore are 

under less threat to invasive species introductions. Other tributaries, including the Little 

Colorado River, traverse large distances before reaching the mainstem and pass through 

numerous jurisdictions where there is limited coordination in addressing invasive species. 

This project would develop a response plan to detect and quickly act should additional 

nonnative species become established in the Colorado River ecosystem as well as develop of 

additional measures as part of the Little Colorado River Watershed Management Plan to 

prevent further introductions. The focus should be to prevent further introductions, yet with 

potential temperature modification, a coordinated response that acts quickly to contain the 

nonnative introduction and prevent further spread is necessary. It should include an 

evaluation of effective ways to detect new species within the Colorado River ecosystem, 

designate an interagency response team to respond to new introductions, and develop a 

response plan that would go into effect if new introductions were detected, including 

necessary NEPA compliance. It should include standard protocols to be used by researchers 

to prevent unintentional introductions. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Goal 7 – Establish water temperature, quality and flow dynamics to achieve AMP ecosystem 

goals. 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 76

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Nonnative Fish Control – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue efforts to control both cold- and warm-water nonnative fish 

species in the mainstem of Marble and Grand canyons, including determining and 

implementing levels of nonnative fish control as necessary. Control of these species using 

mechanical removal and other methods will help to reduce this threat. 

Humpback Chub Recovery Goals

5.2.2.3 Factor C – Adequate protection from diseases and predation 

5.2.2.4 Factor D – Adequate existing regulatory mechanisms 

Management Action D-2 – Provide for the long-term management and protection of 

humpback chub populations and their habitats. 

Task D-2.1 – Identify elements needed for the development of conservation plans that are 

necessary to provide for the long-term management and protection of humpback chub 

populations. 

Task D-2.2 – Develop and implement conservation plans and execute agreements among 

State agencies, Federal agencies, Native American tribes, and other interested parties to 

provide reasonable assurances that conditions needed for recovered humpback chub 

populations will be maintained. 

Executive Order 13112 - “By the authority vested in me as President by the Constitution and 

the laws of the United States of America, including the National Environmental Policy Act of 

1969, as amended (42 U.S.C. 4321 et seq.), Nonindigenous Aquatic Nuisance Prevention and 

Control Act of 1990, as amended (16 U.S.C. 4701 et seq.), Lacey Act, as amended (18 

U.S.C. 42), Federal Plant Pest Act (7 U.S.C. 150aa et seq.), Federal Noxious Weed Act of 

1974, as amended (7 U.S.C. 2801 et seq.), Endangered Species Act of 1973, as amended (16 

U.S.C. 1531 et seq.), and other pertinent statutes, to prevent the introduction of invasive 

species and provide for their control and to minimize the economic, ecological, and human 

health impacts that invasive species cause..... 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 77

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 

Status: The AMP is currently funding development of a nonnative species control plan by 

GCMRC.

 d. Develop nonnative stocking procedures for the Lower Colorado River and tributaries 

from Glen Canyon Dam to Lake Mead. 

The threat of predation and competition by nonnative fishes on humpback chub has been 

recognized in Grand Canyon; brown trout (Salmo trutta), channel catfish (Ictalurus 

punctatus), black bullhead (Ameiurus melas), and rainbow trout (Oncorhynchus mykiss) have 

been identified as principal predators of juvenile humpback chub, with consumption 

estimates that suggest loss of complete year classes to predation (Marsh and Douglas 1997, 

Valdez and Ryel 1997). Marsh and Douglas (1997) documented predation on humpback 

chub in the Little Colorado River by rainbow trout, channel catfish, and black bullhead. 

Valdez and Ryel (1997) identified brown trout, rainbow trout, and channel catfish as known 

predators of humpback chub in the mainstem Colorado River in Grand Canyon, and 

suggested that common carp (Cyprinus carpio) could be a significant predator of incubating 

humpback chub eggs in the Little Colorado River. 

The Colorado River in Grand Canyon is now occupied by at least 12 nonnative fish species. 

In addition to the ones already mentioned, fathead minnow (Pimephales promelas), green 

sunfish (Lepomis cyanellus), largemouth bass (Micropterus salmoides), plains killifish 

(Fundulus zebrinus), red shiner (Cyprinella lutrensis), striped bass (Morone saxatailis), and 

yellow bullhead (Ameiurus natalis) are also known from the region. Recently, walleye 

(Sander vitreus) was collected from below Glen Canyon Dam, and green sunfish and 

smallmouth bass (Micropterus dolomieu) were collected from near the mouth of the Little 

Colorado River. 

Control of the release and escapement of nonnative fishes into the Colorado River in Grand 

Canyon and its tributaries is a necessary management action to limit the impact of currently 

present nonnative species, stop the introduction of new fish species into occupied habitats 

and to thwart periodic escapement of highly predaceous or competitive nonnatives from 

connected waters throughout the basin. Procedures for the stocking of nonnatives have been 

developed and associated implementing agreements have been signed among the U. S. Fish 

and Wildlife Service and the States of Colorado, Utah, and Wyoming to review and regulate 

all stockings within the Upper Colorado River Basin (U.S. Fish and Wildlife Service 1996) in 

order to reduce the introduction and expansion of nonnative fishes. Similar procedures need 

to be developed and implemented to protect the Grand Canyon population of humpback 

chub, including all portions of the Lower Colorado River Basin between Glen Canyon Dam 

and Hoover Dam, including the two mainstem reservoirs (U.S. Fish and Wildlife Service 

2002). 

Relationship to Programs: 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 78

Adaptive Management Program

Strategic Plan, Management Objective 2.6 - Reduce native fish mortality due to non-native 

fish predation/competition as a percent of overall mortality in the Little Colorado River and 

mainstem to increase native fish recruitment.”

Humpback Chub Recovery Goals

5.2.2.3 Factor C - Adequate protection from diseases and predation 

Management Action C-2 - Regulate nonnative fish releases and escapement into the main 

river, floodplain, and tributaries. 

Task C-2.1 - Develop, implement, evaluate, and revise (as necessary through 

adaptive management) procedures for stocking and to minimize escapement of 

nonnative fish species into the Colorado River and its tributaries through Grand 

Canyon to minimize negative interactions between nonnative fishes and 

humpback chub (see sections 4.3.2 and A.8 for discussion of effects of nonnative 

fishes). 

Task C-2.2 - Finalize and implement procedures (as determined under Task 

C-2.1) for stocking and to minimize escapement of nonnative fish species into the 

Colorado River and its tributaries through Grand Canyon to minimize negative 

interactions between nonnative fishes and humpback chub. 

Status: This project has not been funded or implemented. 

10. Understand the impacts and identify the threats of scientific work and recreational 

activities on humpback chub populations in the Grand Canyon region. 

This project will assess the impacts of repetitive habitat disturbance, capture, and handling on 

Grand Canyon humpback chub populations and develop modified protocols and management 

policies to maximize recreation opportunity and scientific information collection while 

minimizing the impacts of these activities on humpback chub individuals and populations. 

Humpback chub in Grand Canyon, particularly the Little Colorado River aggregation, have 

endured significant environmental manipulation and individual physical handling for the last 

20 years. PIT tagging efforts alone have resulted in the majority of adult humpback chub 

being recognized individually from multiple recaptures over time. Sediment, flow, and 

temperature studies, among others, affect mainstem populations to some degree through 

habitat disruption and invasion by investigative crews and equipment. Targeted studies affect 

humpback chub directly; studies targeting other species affect humpback chub indirectly, as 

an unintended consequence. Repetitive disturbance, capture, and handling are continual 

sources of stress, health risk, and potential injury for individuals and the population as a 

whole. 

Upper Basin managers and investigators have similar concerns, but have not initiated specific 

studies to directly quantify the effects, if any. They have, however, produced several studies 

investigating the impacts of electrofishing on native fish and developed modified protocols to 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 79

minimize the risks (Muth 1996, Hawkins 2002, 2003). They also have limited population 

estimate efforts to three initial estimate years followed by alternating two years off and two 

years on to reduce the stress of population monitoring on humpback chub populations (Tom 

Chart and Tom Czapla personal communication, Valdez and Ryel 2000). 

Scientific investigation and monitoring must continue in support of the AMP. However, the 

threat exists that research activities may in fact have a detrimental effect on humpback chub. 

This effect is ongoing for the foreseeable future and may have immediate consequences for 

humpback chub as long as intensive scientific effort is focused on this species and its habitat. 

The physical risk of injury and death associated with repeated handling and disturbance 

should be evaluated. Research and monitoring protocols modified to reduce frequency and 

severity of handling and disturbance could allow continued data collection with minimal 

impact to humpback chub. However, the cost of implementing such modified protocols must 

be weighed against the sacrifice of statistical precision required to make appropriate adaptive 

management decisions. Several laboratory studies have been completed. Paukert et al. (2005) 

for example, found that repeated hoop netting and handling of bonytail (Gila elegans) 

affected growth of that species. Additional research is needed to better understand this threat 

to humpback chub. 

Disturbance associated with recreational activities (boating, swimming, fishing, etc.) in the 

Grand Canyon and especially in the lower portions of the Little Colorado River also may 

cause adverse affects to humpback chub. Repetitive disturbance may be a continual source of 

stress, health risk, and potential injury for individuals and the population as a whole. There 

are no assessments of the potential impact of such activities on humpback chub. Additional 

research is needed to better understand this threat to humpback chub. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Humpback Chub Recovery Goals

5.2.2.2 Factor B – Protection from overutilization for commercial, recreational, scientific, or 

educational purposes.

Management Action B-1 – Protect humpback chub populations from overutilization for 

commercial, recreational, scientific, or educational purposes. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 80

Task B-1.1 – Reevaluate and, if necessary, identify actions to ensure adequate protection 

from overutilization for commercial, recreational, scientific, or educational purposes; not 

currently identified as an existing threat (see section 4.2). 

Task B-1.2 – Implement identified actions (as determined under Task B-1.1.) to ensure 

adequate protection from overutilization for commercial, recreational, scientific, or 

educational purposes. 

Status: This project received funding from the AMP in FY 2004/2005. A study examining 

the effects of hoop netting and PIT tagging, using bonytail (Gila elegans) as a surrogate, has 

been completed and published (Paukert et al. 2005). Studies evaluating other aspects of this 

project have not been funded or undertaken. 

11. Monitor and investigate control of fish diseases and parasites affecting humpback chub 

in the Colorado River, Grand Canyon region. 

This project includes two elements: (1) development and implementation of a monitoring 

plan for fish diseases and parasites in the Colorado River and its tributaries, with emphasis on 

those infecting humpback chub; and, (2) investigation of mechanisms for control and 

suppression of important diseases and parasites. 

At least four exotic parasites are known to infect fishes of the Little Colorado River. Two of 

these parasites, Asian fish tapeworm Bothriocephalus acheilognathi (Cestoda) and anchor 

worm Lernaea cyprinacea (Copepoda) infect humpback chub at a higher rate than any other 

species in the system (Brouder and Hoffnagle 1997; Hoffnagle and Cole 1999; Hoffnagle et 

al 2000). Both B. acheilognathi and L. cyprinacea have been reported as pathogenic and 

potentially fatal (directly or indirectly) to fish of various age classes (Schäpperclaus 1986). 

Bothriocephalus acheilognathi has caused high mortality in native fishes that it has infected 

outside of its native range (Hoffman and Schubert 1984). These parasites cannot complete 

their life cycles in the mainstem Colorado River under present, cold water conditions. 

However they may be transported by infected individuals to other warmer tributaries. 

Information on disease and parasite distribution, and the impact of water temperature regimes 

on diseases and parasites is needed for decisions regarding the future operation of Glen 

Canyon Dam and the proposed selective withdrawal structure. Previous studies (Brouder and 

Hoffnagle 1997, Hoffnagle and Cole 1999, Hoffnagle et al 2000, Cole et al 2002, Hoffnagle 

et al. 2006) have identified parasites of native and non-native fishes of the lower Little 

Colorado River. Recent research by Dr. Rebecca Cole, (see FY2005 GCMRC Work Plan) 

has helped define the distribution of fish diseases and parasites of the colder Colorado River 

and other tributaries in Grand Canyon. This project will survey the river and tributaries for a 

complete inventory of diseases and parasites present, and will recommend a monitoring plan 

for fish parasites and diseases in the Colorado River ecosystem and selected tributaries. 

Recent research by Ward (2007) has evaluated the use of praziquantel to remove Asian 

tapeworm from Gila species in the laboratory, and 30 humpback chub were evaluated for 

tapeworms in the Little Colorado River in both 2005 and 2006 – thus the beginnings of a 

monitoring data set are in place. There is also a need to assess the status of other parasite and 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 81

disease organisms in other parts of the watershed that could invade the Colorado River 

ecosystem in Grand Canyon. 

The second phase of this project will investigate effects of diseases and parasites on 

humpback chub, or a surrogate species, in laboratory settings and the feasibility of control 

and suppression in the wild of diseases and parasites important to the health and survival of 

humpback chub. For example, praziquantel has been used since 1985 to remove parasites in 

many different fish species in hatcheries and ornamental fish ponds. Initial investigations of 

Asian tapeworm have found that praziquantel can effectively remove tapeworm from 

humpback chub in both the laboratory and field settings, although dosages commonly 

reported in the literature were insufficient (Ward in press). Additional study is needed to 

ensure that praziquantel is safe for use on fish prior to further use and refine non-lethal 

methods for removing tapeworms from endangered cyprinid fishes. It will also refine 

efficacy in field situations where reinfestation rates may be high. Management 

recommendations will include a standardized protocol for the use of praziquantel to treat 

Asian fish tapeworm as well as recommendations for reducing the impacts of Asian fish 

tapeworm in humpack chub. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.5 – Attain humpback chub condition in the Little 

Colorado River and other aggregations for viable populations and to remove jeopardy. 

Humpback Chub Recovery Goals

5.2.2.3 Factor C – Adequate protection from diseases and predation 

Management Action C-1 – Control Asian tapeworm as needed 

Task C-1.1 – Develop an Asian tapeworm control program in the Little Colorado River to 

identify the levels of control that will minimize the negative effects of parasitism on the 

humpback chub population (see section 4.3.1 and Appendix A for discussion of diseases 

and parasites). 

Task C-1.2 – Implement identified levels (as determined under Task C-1.1) of Asian 

tapeworm control in the Little Colorado River. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Parasite Monitoring – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue to support research on the effects of Asian tapeworm 

(Bothriocephalus acheilognathi) on humpback chub and potential methods to control this 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 82

parasite. Continuing research will help better understand the degree of this threat and the 

potential for management actions to minimize it. 

Status: The project has been partially funded and implemented by the AMP. Additional 

work, as explained above, is needed and has yet to be funded or implemented. 

12. Translocation of native fishes including humpback chub in the Grand Canyon region. 

a. Translocations of humpback chub in the Little Colorado River above Chute Falls. 

The majority of young humpback chub that disburse or are displaced into the Colorado River 

from the Little Colorado River are presumed to perish due to cold water temperatures, diel 

discharge fluctuations, and predation by nonnative fishes. Most humpback chub that recruit 

to adulthood are believed to be individuals that remain in the warmer Little Colorado River 

for longer periods of time to grow and become less susceptible to the inhospitable conditions 

in the mainstem. Endemic speckled dace and a few, primarily small-bodied, nonnative fishes 

have consistently been the only species detected above a barrier waterfall, Chute Falls, 

during ichthyofauna surveys over the last two decades. Translocation of juvenile humpback 

chub from near the confluence of the Colorado and Little Colorado rivers to the reach of the 

Little Colorado River above Chute Falls increases the numbers of younger humpback chub 

that recruit to adulthood via improved survivorship due to greater food abundance, warmer 

water temperatures, and reduced competition and predation (because there are fewer largebodied fishes in this area, and the thermal shock issue is eliminated) and expands suitable 

humpback chub rearing habitats within the Little Colorado River. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Humpback Chub Translocation – In coordination with other Department of the Interior 

(DOI) AMP participants and through the AMP, Reclamation will assist NPS and the AMP in 

funding and implementation of translocation of humpback chub into tributaries of the 

Colorado River in Marble and Grand canyons. Nonnative control in these tributaries will be 

an essential precursor to translocation, so Reclamation will help fund control of both cold 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 83

and warm-water nonnative fish in tributaries, as well as efforts to translocate humpback chub 

into these tributaries. Havasu, Shinumo and Bright Angel creeks will initially be targeted for 

translocation, although other tributaries may be considered. Reclamation will work with 

FWS, NPS and other cooperators to develop translocation plans for each of these streams, 

utilizing existing information available such as SWCA and Grand Canyon Wildlands (2007) 

and Valdez et al. (2000a). These plans will consider and utilize genetic assessments 

(Douglas and Douglas 2007, Keeler-Foster in prep.), identify legal requirements and 

jurisdictional issues, methods, and assess needs for nonnative control, monitoring and other 

logistics, as well as an implementation schedule, funding sources, and permitting. 

Reclamation and the AMP will also fund and implement translocation of up to 500 young 

humpback chub from the lower Little Colorado River to above Chute Falls in 2008 if FWS 

determines that a translocation is warranted. Reclamation and the AMP will continue to 

monitor humpback chub in the reach of the Little Colorado River above Chute Falls for the 

5-year period of the proposed action, and will undertake additional translocations above 

Chute Falls as deemed necessary by FWS. 

Status: Translocation began as a conservation measure of the December 6, 2002, Biological 

Opinion. Small humpback chub (50-100 mm TL) from the lower Little Colorado River have 

been moved to above Chute Falls in an attempt to improve survival of young of year 

humpback chub in 2003, 2004, 2005, and 2008. To date, approximately 1,500 humpback 

chub have been moved. Monitoring has indicated translocated humpback chub have persisted 

above Chute Falls, shown impressive growth rates, and appear to have spawned in 2005. 

Translocation is currently funded by the AMP and is planned for 2009-2012. 

 b. Translocation of native fishes to tributaries of the Colorado River in Grand Canyon 

National Park and on tribal lands. 

This project is linked to project 9a, which involves removal of nonnative fish from tributaries 

selected for translocation. Nonnative suppression likely is a necessary prerequisite for 

translocation of humpback chub into tributaries having suitable physical habitat for this 

purpose. The goal of this project is to expand the demographic range of humpback chub and 

reduce the risk of catastrophic events in the Little Colorado River by using other tributaries 

as grow out areas for small humpback chub. The objective is to transplant young-of-year 

Little Colorado River humpback chub that likely would be transported to the Colorado River 

and otherwise not survive to potentially suitable tributaries within Grand Canyon National 

Park and adjoining tribal lands to improve their survival. Based on evaluations conducted by 

Valdez and others (2000), the probability of establishing sustained reproducing and recruiting 

humpback chub populations in these tributaries is small. Young humpback chub translocated 

to tributaries with suitable juvenile habitat and reduced predator numbers that grow to a size 

large enough to survive in the mainstem have an opportunity to join existing mainstem 

aggregations. There they may serve to augment founder populations if mainstem conditions 

improve sufficiently to allow reproduction and recruitment, e.g. if water temperatures 

increase following implementation of a selective withdrawal structure.

Relationship to Programs: 

Adaptive Management Program
Draft Humpback Chub Comprehensive Plan – June 16, 2009 84

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Strategic Plan, Management Objective 2.4 – Establish humpback chub spawning 

aggregations outside the Little Colorado River in the Colorado River ecosystem below Glen 

Canyon Dam to remove jeopardy. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Humpback Chub Translocation – In coordination with other Department of the Interior 

(DOI) AMP participants and through the AMP, Reclamation will assist NPS and the AMP in 

funding and implementation of translocation of humpback chub into tributaries of the 

Colorado River in Marble and Grand canyons. Nonnative control in these tributaries will be 

an essential precursor to translocation, so Reclamation will help fund control of both cold 

and warm-water nonnative fish in tributaries, as well as efforts to translocate humpback chub 

into these tributaries. Havasu, Shinumo and Bright Angel creeks will initially be targeted for 

translocation, although other tributaries may be considered. Reclamation will work with 

FWS, NPS and other cooperators to develop translocation plans for each of these streams, 

utilizing existing information available such as SWCA and Grand Canyon Wildlands (2007) 

and Valdez et al. (2000a). These plans will consider and utilize genetic assessments 

(Douglas and Douglas 2007, Keeler-Foster in prep.), identify legal requirements and 

jurisdictional issues, methods, and assess needs for nonnative control, monitoring and other 

logistics, as well as an implementation schedule, funding sources, and permitting. 

Reclamation and the AMP will also fund and implement translocation of up to 500 young 

humpback chub from the lower Little Colorado River to above Chute Falls in 2008 if FWS 

determines that a translocation is warranted. Reclamation and the AMP will continue to 

monitor humpback chub in the reach of the Little Colorado River above Chute Falls for the 

5-year period of the proposed action, and will undertake additional translocations above 

Chute Falls as deemed necessary by FWS. 

Status: Grand Canyon National Park has acquired the necessary funding for, and is working 

to complete the necessary compliance on, translocation of humpback chub into Shinumo 

Creek in 2009. Juvenile humpback chub were removed from the lower Little Colorado River 

and are currently being housed at Dexter National Fish Hatcher for translocation into 

Shinumo in 2009. Additional collections of juvenile humpback chub for translocation into 

Shinumo are planned. Translocations to other tributaries have not been funded or implement, 

but have been evaluated (Valdez et al. 2000). 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 85

Monitoring humpback chub Population Dynamics, Distribution, and Habitat Paramount to 

evaluating the status of humpback chub in the Grand Canyon are scientifically defensible 

estimates of its population size, dynamics with respect to recruitment, and distribution. Several 

areas of uncertainty or lack of consensus remain regarding how and where this information is 

obtained. Equally important is an understanding of habitat changes over time. 

13. Monitor humpback chub population dynamics, distribution and habitat in the Grand 

Canyon region. 

a. Monitoring hydrology and water quality in the Little Colorado River. 

While anthropogenic changes in the mainstem Colorado River are often cited as contributing 

to the decline of humpback chub, little is known about historical or recent changes in 

physical and chemical characteristics of the Little Colorado River in Grand Canyon, and how 

these may have affected the humpback chub. The Little Colorado River stream gage was 

reestablished in 2003, using newer and more effective (acoustic) technologies for measuring 

river stage. Operation of the gage record by the GCMRC Integrated Downstream Quality of 

Water Program (DIQWP) is aimed at establishing a continuous stage and discharge record to 

support ongoing fisheries monitoring and research in the lower 15 km of the Little Colorado 

River. The gage will also support future monitoring efforts for targeted water quality 

parameters associated with flows in the Little Colorado River related to Blue Spring and 

other sources upstream. Also needed is a monitoring program for basic water quality 

parameters, contaminants, and a review of existing historical hydrological and water quality 

data. This project will allow for continued operation of the gage and development of a 

monitoring program for other water quality data in the Lower Little Colorado River. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Humpback Chub Recovery Goals

5.2.2.1 Factor A. - Adequate habitat and range for recovered populations provided. 

Management Action A-1 - Investigate the role of the mainstem Colorado River in maintaining 

the Grand Canyon humpback chub population and provide appropriate habitats in the 

mainstem as necessary for recovery. 

 Task A-1.2 - Provide appropriate habitats for humpback chub in the mainstem Colorado 

River (as determined necessary under Task A-1.1 [of the Recovery Goals]). 

Status: This project is not currently funded or implemented. 

b. Maintain a core monitoring and research effort for the humpback chub in the Grand 

Canyon region. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 86

Effective monitoring of humpback chub is an essential element to this plan. Since 2000, 

GCMRC has implemented a rigorous stock assessment program for the Little Colorado River 

aggregation of humpback chub as a priority component, as well as long-term fish monitoring 

in Grand Canyon. This effort has consisted of several separate monitoring projects relying on 

mark-recapture efforts in both the Little Colorado River and mainstem. 

Criticisms of the GCMRC method have largely been associated with the degree to which the 

mainstem Colorado River and Little Colorado River need to be monitored to obtain an 

accurate and precise abundance estimate for the entire Grand Canyon population of 

humpback chub (recognizing that this population is centered predominantly around the Little 

Colorado River, and migrates into the Little Colorado River during spawning). Currently, 

population estimates for humpback chub are conducted in the Little Colorado River in the 

fall of each year to estimate abundance of smaller chub and to make an early estimate of the 

survival and potential recruitment of a given year class. Sampling is also conducted in the 

spring primarily aimed at marking as many humpback chub as feasible to provide 

information through capture and subsequent recapture for stock assessment models. 

Depending on the quality of data with respect to meeting assumptions of mark-recapture 

population estimation models, these spring data may also be used to generate a point estimate 

of the population size. There has and continues to be uncertainty regarding how well point 

estimates derived solely from Little Colorado River sampling represent the status and trends 

of the ‘Little Colorado River population’, which contains individuals that are known to move 

back and forth between the Little Colorado River and mainstem, particularly during the 

spawning period. There is also concern about adopting consistent population estimation 

procedures for populations of humpback chub in the Upper and Lower Basin to satisfy 

criteria identified in the Recovery Goals. 

Seasonal movement and distribution of humpback chub complicate finding the ideal 

sampling schedule for this effort. It is assumed that the largest proportion of the population 

goes into the Little Colorado River for spawning and may or may not remain there during 

part or all of the mark-recapture sampling there (i.e., the timing of movement in and out 

varies from year to year and good predictors of when migration will occur is lacking). 

Sampling in the spring would add information about the distribution of fish and their 

movement but could violate model assumptions for simple mark-recapture population 

estimation. 

Recent modeling research by Dr. David Otis at the University of Iowa, utilizing data 

developed from the GCMRC monitoring program, indicated that adjusting current levels of 

effort and employing additional statistical estimators may improve GCMRC’s estimation 

technique. Another important consideration in refining this project is the need to include 

translocated humpback chub in the population estimate. For example, a total of 

approximately 1,500 humpback chub have been moved above a natural barrier (Chute Falls) 

in the Little Colorado River. Subsequent monitoring of these translocated humpback chub 

revealed that many of the translocated individuals were found to have persisted, grown to 

adult size, and spawned. Given this, there may also be a need to conduct a stock assessment 

of the Chute Falls segment of the population and incorporate it into ongoing stock 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 87

assessments occurring below Chute Falls to provide an accurate overall stock assessment of 

the entire Grand Canyon population as required by the recovery goals. GCMRC is currently 

conducting a Protocol Evaluation Panel, which may result in changes to the fish monitoring 

program. 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 2.2 – Maintain or attain year class strength of 

juvenile humpback chub in the Little Colorado River and other aggregations for viable 

populations and removal of jeopardy. 

Strategic Plan, Management Objective 2.3 – Maintain or attain humpback chub recruitment 

in the Little Colorado River and other aggregations for viable populations and removal of 

jeopardy. 

Strategic Plan, Management Objective 2.4 – Establish humpback chub spawning 

aggregations outside the Little Colorado River in the Colorado River ecosystem below Glen 

Canyon Dam to remove jeopardy. 

Strategic Plan, Management Objective 7.1 – Attain water temperature ranges and seasonal 

variability in the mainstem necessary to maintain or attain desired levels of desirable 

biological resources (e.g., native fish, foodbase and trout). 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 

Humpback Chub Recovery Goals

5.3.1.1 Demographic criteria for downlisting (population demographics in both

recovery units must be met in order to achieve downlisting)

Status: This project is ongoing, and does not currently have an expected completion date. A 

2009 PEP will guide future implementation.

c. Monitoring the Status and Trends of the Downstream Fish Community in Grand 

Canyon. 

The downstream fish community is an assemblage of native and non-native fish that occur in 

the Colorado River ecosystem. This assemblage is exclusive of the trout fishery that is 

managed in Glen Canyon by the Arizona Game and Fish Department. The constituents 

include four native fish and introduced competitors/predators including rainbow trout, brown 

trout, channel catfish, carp, and other nonnative species. The status and trends of the fishery 

are regulated by biotic and abiotic mechanisms that may in turn be affected by the operations 

of Glen Canyon Dam. Monitoring basic population statistics including recruitment, 

abundance, and distribution of native and nonnative fishes provide the fundamental 

information necessary to assess the status of these resources and the attainment of AMP goals 

and objectives. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 88

Since 2000, GCMRC and cooperators have been developing a long-term monitoring program 

for fishes in the Colorado River ecosystem. To date, significant progress has been made 

toward this end such that it is now appropriate for GCMRC to formalize a longterm 

monitoring program for key nonnative fishes (i.e. rainbow trout, brown trout, and common 

carp). A key aspect of this program will be the development of a conceptual ecosystem 

model. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.6 – Reduce native fish mortality due to nonnative 

fish predation so that it does not impinge on viability. 

Strategic Plan, Management Objective 2.8 – Maintain or attain abundance of flannelmouth 

sucker, bluehead sucker, and speckled dace at levels to be determined. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Nonnative Fish Control – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue efforts to control both cold- and warm-water nonnative fish 

species in the mainstem of Marble and Grand canyons, including determining and 

implementing levels of nonnative fish control as necessary. Control of these species using 

mechanical removal and other methods will help to reduce this threat. 

Humpback Chub Recovery Goals

5.2.2.3 Factor C: – Adequate protection from diseases and predation. 

Management Action C-3 – Control problematic nonnative fishes as needed. 

Task C-3.1 – Develop rainbow trout, channel catfish, black bullhead, and common carp 

control programs in the Little Colorado River to identify levels of control that will 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 89

minimize predation on humpback chub (see section 4.3.2 and A.8 for discussion of 

effects of nonnative fishes). 

Task C-3.2 – Implement identified levels (as determined under Task C-3.1) of rainbow 

trout, channel catfish, black bullhead, and common carp control in the Little Colorado 

River.

Task C-3.3: - Brown trout and rainbow trout control programs developed and 

implemented to identify levels of control that will minimize predation on humpback chub 

in the Colorado River through Grand Canyon. 

5.3.1.1 Demographic criteria for downlisting (population demographics in both

recovery units must be met in order to achieve downlisting)

Status: This project is ongoing, and does not currently have an expected completion date. A 

2009 PEP will guide future implementation.

 d. Develop a monitoring program for the Colorado River downstream of Diamond 

Creek to detect changes in habitat and aquatic communities and complement the 

monitoring program upstream of Diamond Creek. 

Lake Mead’s full pool elevation is at 1229 feet. At this elevation, the inflow area of Colorado 

River is influenced by the reservoir as far upstream as Separation Rapids (RM 239.5). This 

location is about 37 miles upstream of Grand Wash Cliffs (RM 276.5), the western boundary 

of Grand Canyon National Park and the eastern boundary of Lake Mead National Recreation 

Area. The 1992 Grand Canyon Protection Act (GCPA) uses Grand Wash Cliffs in Grand 

Canyon National Park as the western boundary of the AMP. In past years, there was no 

monitoring of fishes or fish habitat below the confluence of Diamond Creek with the 

mainstem Colorado River (RM 226). The area between Separation Rapid and Grand Wash 

Cliffs overlaps with the area for the Lower Colorado River Multi-Species Conservation 

Program (MSCP), so this reach is of interest to both programs. This project would develop a 

monitoring program for the river downstream of Diamond Creek to detect changes in habitat 

and fish communities resulting from dam operations or other causes. Monitoring of 

nonnative and native fish in this reach may become increasingly important to both the AMP 

and MSCP, particularly if there is upstream movement of nonnative fish out of Lake Mead 

into Grand Canyon. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.6 – Reduce native fish mortality due to nonnative 

fish predation so that it does not impinge on viability. 

Strategic Plan, Management Objective 2.8 – Maintain or attain abundance of flannelmouth 

sucker, bluehead sucker, and speckled dace at levels to be determined. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures
Draft Humpback Chub Comprehensive Plan – June 16, 2009 90

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through 

the AMP, continue efforts to assist NPS and the AMP in control of both cold- and warmwater nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the 

period of the proposed action, control of nonnative trout may be particularly important. 

Control of these species will utilize mechanical removal, similar to recent efforts by the 

AMP, and may utilize other methods, to help to reduce this threat. GCMRC is preparing a 

nonnative fish control plan through the AMP process that addresses both cold and warmwater species that will further guide implementation of this conservation measure. 

2007 Biological Opinion for the Bureau of Reclamation’s Proposed Adoption of Colorado 

River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake 

Powell and Lake Mead Conservation Measures

Nonnative Fish Control – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue efforts to control both cold- and warm-water nonnative fish 

species in the mainstem of Marble and Grand canyons, including determining and 

implementing levels of nonnative fish control as necessary. Control of these species using 

mechanical removal and other methods will help to reduce this threat. 

Humpback Chub Recovery Goals

5.2.2.3 Factor C: – Adequate protection from diseases and predation. 

Management Action C-3 – Control problematic nonnative fishes as needed. 

Task C-3.1 – Develop rainbow trout, channel catfish, black bullhead, and common carp 

control programs in the Little Colorado River to identify levels of control that will 

minimize predation on humpback chub (see section 4.3.2 and A.8 for discussion of 

effects of nonnative fishes). 

Task C-3.2 – Implement identified levels (as determined under Task C-3.1) of rainbow 

trout, channel catfish, black bullhead, and common carp control in the Little Colorado 

River.

Task C-3.3: - Brown trout and rainbow trout control programs developed and 

implemented to identify levels of control that will minimize predation on humpback chub 

in the Colorado River through Grand Canyon. 

Lower Colorado River Multi-Species Conservation Program

The Little Colorado River-MSCP has established basic performance standards to meet to be 

in compliance with terms and conditions of an incidental take permit for covered projects. 

The Little Colorado River-MSCP identified the need to provide a level of support to the 

AMP for humpback chub. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 91

Status: Monitoring of fish and crayfish below Diamond Creek using various gear types has 

occurred annually since 2004. This project is ongoing, and does not currently have an 

expected completion date. A 2009 PEP will guide future implementation.

14. Develop planning documents to assist with conservation of humpback chub in the 

Grand Canyon region. 

a. Develop a watershed management plan for the Little Colorado River. 

This project focuses on the improvement and protection of the Little Colorado River 

watershed to ensure appropriate habitat conditions downstream on the Little Colorado River 

in the area occupied by the humpback chub. Potential issues to be addressed include surface 

and groundwater quantity and quality, pesticides and other hazardous substances, and 

nonnative fish stocking. Several of these issues are addressed in separate projects listed 

below which should become components in a Little Colorado River watershed management 

plan that includes the hydrologic boundaries of the watershed. 

The Little Colorado River watershed is a large area with many political jurisdictions and 

authorities. For this effort to be successful, these parties must work cooperatively together as 

they consider their various ideas and responsibilities. The Little Colorado River Watershed 

Coordinating Council (Little Colorado RiverWCC) has been organized to facilitate 

discussions among these various interests. The Bureau of Reclamation, Arizona Game and 

Fish Department, and the U.S. Fish and Wildlife Service are involved in this council. This 

project will review the status of this effort and its development of a watershed management 

plan, and then assist in the development and implementation of such a plan. The plan should 

identify ways to protect instream flows from Blue Spring for humpback chub recovery. This 

project will assist in meeting the recovery goal of assuring continued protection of conditions 

needed for humpback chub recovery by assisting the development of a watershed 

management plan for the Little Colorado River. Specifically this effort would cooperatively 

develop a watershed-based management plan to provide a strategy for protecting the 

endangered humpback chub and other federally listed species while at the same time 

continuing with necessary water and resource development, prioritize necessary actions to 

achieve these goals, identify funding sources, construct management objectives and targets 

for measuring success, develop the framework for cooperative agreements, and identify a 

timeline for completion of tasks and measurement of success. 

Relationship to Programs: 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 92

Humpback Chub Recovery Goals

 

Humpback Chub 5.2.2.4 Factor D – Adequate existing regulatory mechanisms 

Management Action A-2 – Provide flows necessary for all life stages of humpback chub to 

support a recovered Grand Canyon population, based on demographic criteria. 

Task A-2.2 – Identify, implement, evaluate, and revise (as necessary through adaptive 

managment) a flow regime in the Little Colorado River to benefit humpback chub. 

Management Action D-2 – Provide for the long-term management and protection of 

humpback chub populations and their habitat. 

Task D-2.2 - Develop and implement conservation plans and execute agreements among 

State agencies, Federal agencies, American Indian tribes, and other interested parties to 

provide reasonable assurances that conditions needed for recovered humpback chub 

populations will be maintained. 

2008 Biological Opinion on the Operation of Glen Canyon Dam Conservation Measures

Little Colorado River Watershed Planning – Reclamation will continue its efforts to help 

other stakeholders in the Little Colorado River watershed develop watershed planning 

efforts, with consideration for watershed level effects to the humpback chub in Grand 

Canyon. 

Status: The project described here has not been funded or implemented. The Bureau of 

Reclamation is working to finish a Little Colorado River watershed report. Continued 

coordination with the Little Colorado River WCC and the AMP is needed. 

 b. Develop an emergency response/contingency plan for protection of downstream 

species from spills into the Little Colorado River at Cameron or other potential sites. 

The humpback chub recovery goals discuss the need to “Review and modify, if necessary, 

state and federal hazardous spills emergency response plans to insure adequate protection 

from spills, including prevention and quick response to spills; develop and implement a 

hazardous spills protocol for the Cameron Bridge.” This project would develop a welldesigned contingency plan providing details about each step involved in preparing for, and 

responding to, spills of materials into the Little Colorado River channel at Cameron Bridge 

on Highway 89 or other potential sites for the express purpose of protecting native fish 

species in the Little Colorado River. 

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 93

 Humpback Chub Recovery Goals

5.2.2.4 Factor D – Adequate existing regulatory mechanisms 

Management Action D-2 – Provide for the long-term management and protection of 

humpback chub populations and their habitats. 

 Task D-2.1 – Identify elements needed for the development of conservation plans that are 

necessary to provide for the long-term management and protection of humpback chub 

populations. 

 Task D-2.2 – Develop and implement conservation plans and execute agreements among 

State agencies, Federal agencies, Native American tribes, and other interested parties to 

provide reasonable assurances that conditions needed for recovered humpback chub 

populations will be maintained. 

5.225 Factor E – Other natural or manmade factors for which protection has been provided. 

Management Action E-1 – Minimize the risk of hazardous-materials spills in critical habitat. 

 Task E-1.1 – Review and recommend modifications to State and Federal hazardousmaterials spills emergency-response plans to ensure adequate protection for humpback 

chub populations from hazardous–materials spills, including prevention and quick 

response to hazardous-materials spills. 

 Task E-1.2 – Implement State and Federal emergency-response plans that contain the 

necessary preventive measures for hazardous-materials spills. 

 Task E-1.3 – Identify measures to minimize the risk of hazardous-materials spills from 

transport of materials along U.S. Highway 89 at and near the two Cameron bridges 

spanning the Little Colorado River. 

 Task E-1.4 – Implement measures to minimize risk of hazardous-materials spills from 

transport of materials along U.S. Highway 89 at and near the two Cameron bridges 

spanning the Little Colorado River. 

 

Status: This project has not been funded or implemented. 

 c. Develop a pollution control plan for Little Colorado River Basin. 

The plan would provide a comprehensive evaluation of threats to the humpback chub and its 

critical habitat that may arise from pollution generating activities in the Little Colorado River 

Basin and suggest potential actions to ameliorate these threats. This would first entail a 

comprehensive review of existing plans and projects of federal, state, tribal, local and private 

entities as well as adopted and planned water quality standards and objectives for the 

watershed related specifically to aquatic life. Next, the project would identify various 

pollution scenarios related to both point and nonpoint sources of pollutants. Subsequently, 

the project would identify appropriate response actions that could be employed to address the 

identified pollution scenarios. The project would be implemented in such a manner as to 

complement and be consistent with other Little Colorado River watershed plans. It should 

provide appropriate background information on watershed activities representing potential 

pollution threats with particular emphasis on humpback chub, identify all relevant 

institutional responsibilities and contact information, and available response capabilities 

including equipment. The project should also identify existing best management practices, 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 94

treatment and control practices, likely sources of unintended pollution scenarios, and 

recommendations regarding response scenarios and responsibilities.

Adaptive Management Program

Strategic Plan, Management Objective 2.1 – Maintain or attain humpback chub abundance in 

the Little Colorado River and other aggregations at appropriate levels for viable populations 

and to remove jeopardy. 

Strategic Plan, Management Objective 7.2 – Maintain water quality in the mainstem of the 

Colorado River ecosystem. 

 

 Humpback Chub Recovery Goals

 

5.2.2.4 Factor D – Adequate existing regulatory mechanisms 

Management Action D-2 – Provide for the long-term management and protection of 

humpback chub populations and their habitats. 

Task D-2.1 – Identify elements needed for the development of conservation plans that are 

necessary to provide for the long-term management and protection of humpback chub 

populations. 

Task D-2.2 – Develop and implement conservation plans and execute agreements among 

State agencies, Federal agencies, Native American tribes, and other interested parties to 

provide reasonable assurances that conditions needed for recovered humpback chub 

populations will be maintained. 

Status: This project has not been funded or implemented.
Draft Humpback Chub Comprehensive Plan – June 16, 2009 

APPENDIX C. Project Cross Reference Table B-1. List of Humpback Chub Comprehensive Plan projects cross-referenced with the Draft 2008 Recovery 

Humpback Chub (U.S. Fish and Wildlife Service 2008) and conservation measures from the Biological Opinion Adoption of Colorado River Interim Guidelines for Lower Basin Shortages (SBO, U.S. Fish and Wildlife Service Biological Opinion for the Operation of Glen Canyon Dam (GBO, U.S. Fish and Wildlife Service 2008). Threats 

defined in the Draft 2008 Recovery Goals for Humpback Chub (U.S. Fish and Wildlife Service 2008): Factor A-

range for recovered populations provided, Factor B-Protection from overutilization fro commercial, recreational, 

educational purposes, Factor C-Adequate protection from diseases or predation, Factor D-Adequate existing reguFactor E-Other natural or manmade factors for which protection has been provided. Monitoring is essential to the 

threats and thus is considered to address all threats. 

Project Title Recovery Goals 

CoM

1 Humpback Chub Genetics Management Plan Action 5.3.1.1 2 Humpback Chub Refuge Creation Action 5.3.1.1 SB3 Glen Canyon Dam Operations Task A-1.1.-A-1.2, 

Task A-2.1-A-2.2 

4 Glen Canyon Dam Selective Withdraw Structure Task A-1.1-A1.2, 

Task A-3.1-3.2 

5 Sediment Augmentation Task A-1.1.-A-1.2 6 Aquatic Food Base Monitoring and Research Task A-1.1.-A-1.2 7 Young Humpback Chub Habitat Enhancement in the Little Colorado River and other 

Grand Canyon Tributaries Action 5.3.1.1 

8 Fate of Young Humpback Chub in the Colorado River in Grand Canyon Task A-1.1 SB9 Nonnative Control Task C-3.1.-C-3.6 SB

 a. Nonnative Control in Tributaries of the Colorado River in Grand Canyon Task C-3.1.-C-3.6 SB b. Nonnative Control Near the Mouth, and/or in the Lower 15 km, of the Little Colorado 

River Task C-3.1.-C-3.6 SB

 c. Develop Nonnative and Invasive Species Control Plan for the Grand Canyon Region Task C-3.1.-C-3.6 SB d. Develop Nonnative Stocking Procedures for Grand Canyon Watershed Task C-2.1.-C-2.2 

10 Effects of Scientific Work and Recreational Activities on Humpback Chub Task B-1.1-B-1.2 11 Monitoring and Control of Humpback Chub Diseases and Parasites Task C-1.1-C-1.2 SB12 Translocation of Native fishes in Grand Canyon Action 5.3.1.1 G

 a. Translocation of Humpback Chub above Chute Falls in the Little Colorado River Action 5.3.1.1 G b. Translocation of Native fish to Grand Canyon Tributaries other than the Little Colorado 

River Action 5.3.1.1 G

13 Monitor Humpback Chub Population Dynamics, Distribution, and Habitat Action 5.3.1.1 G

 a. Monitor Hydrology and Water Quality in the Little Colorado River Task A-2.2 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 

 b. Maintain a Core Monitoring Effort for Humpback Chub in Grand Canyon Action 5.3.1.1 G c. Monitor the Status and Trends of the Downstream Fish Community in Grand Canyon Action 5.3.1.1 G d. Monitor the Status and Trends of Fishes, Crayfish, and Quagga Mussel below Diamond 

Creek Action 5.3.1.1 G

14 Planning Documents to Assist Conservation of Humpback Chub 

a. Develop Watershed Management Plan for the Little Colorado River 

Task A-2.2, Task D-2.2 G

b. Develop Emergency Response/Contingency Plan for the Little Colorado River 

Task D-2.1-2.2, Task E-1.1-1.4 

 c. Develop Pollution Control Plan for Little Colorado River Task D-2.1-2.2 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 

APPENDIX D. Project Ranking Table C-1. In October 2006, the Ad Hoc was asked to rate the 14 humpback chub projects in this plan (some wi5 criteria (on a scale of 1-5, 5 being best): benefit, cost, feasibility, learning, and timeframe. The results are summ

below by a percentage score of the total points possible, the mean score (Avg), the sample variance (Var), and thresults for the project rankings were summarized using a weighted value for the “benefit” criteria (by a factor of ranking that emphasizes the potential benefit of a project to humpback chub over the other criteria; the Ad Hoc pto the unweighted ranking. The Average and Variance are not weighted. Ten Ad Hoc members participated in thNote that subprojects are ranked separately within their parent project and are italicized.

Number Project Title Weighted Score Avg 

2 Humpback Chub Refuge Creation 85.6 3.9 1 Humpback Chub Genetics Management Plan 84.6 4.3 

10 Effects of Scientific Work and Recreational Activities on Humpback Chub 79.4 3.7 11 Monitoring and Control of Humpback Chub Diseases and Parasites 76.9 3.5 12 Translocation of Native fishes in Grand Canyon 76.0 3.8 

 a. Translocation of humpback chub above Chute Falls in the Little Colorado River. 75.9 4.0  b. Translocation of native fish to Grand Canyon tributaries other than the Little Colorado 

River 68.5 3.5 

13 Monitor Humpback Chub Population Dynamics, Distribution, and Habitat 74.4 3.7 

 a. Monitor hydrology and water quality in the Little Colorado River 69.9 3.7  b. Maintain a core monitoring effort for humpback chub in Grand Canyon 75.1 3.8  c. Monitor the status and trends of the downstream fish community in Grand Canyon 72.8 3.6  d. Monitor the status and trends of fishes and crayfish below Diamond Creek 62.2 3.4 

6 Aquatic Food Base Monitoring and Research 73.6 3.4 8 Fate of Young Humpback Chub in the Colorado River in Grand Canyon 73.6 3.2 4 Glen Canyon Dam Selective Withdraw Structure 71.7 2.9 9 Nonnative Control 70.4 3.0 

 a. Nonnative control in tributaries of the Colorado River 59.3 2.9  b. Nonnative control near the mouth of, and/or in the lower 15 km, of the Little Colorado 

River 73.7 3.4 

 c. Develop nonnative and invasive species control plan for the Grand Canyon region 77.0 3.6  d. Develop nonnative stocking procedures for Grand Canyon region 65.7 3.4 

14 Planning Documents to Assist Conservation of Humpback Chub 63.9 3.2 

a. Develop watershed management plan for the Little Colorado River. 67.4 3.2 b. Develop emergency response/contingency plan for the Little Colorado River. 77.9 3.7 c. Develop pollution control plan for Little Colorado River. 67.6 3.2 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 

7 Young Humpback Chub Habitat Enhancement in Grand Canyon Tributaries 58.8 2.8 3 Glen Canyon Dam Operations 53.9 2.7 5 Sediment Augmentation 45.2 2.0 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 99

APPENDIX E. Deleted Projects 

The following projects were included in previous versions of this plan, but were deleted from 

this version of the plan for various reasons, as listed below in bold/italics. Citations of 

completed projects are also listed, where applicable. 

Determine genetic relationships within and among populations of the endangered humpback 

chub (Gila cypha) in the Colorado River Basin. COMPLETED: Douglas, M. E. and M. R. 

Douglas. 2006. Conservation Genetics of Gila Cypha in the Colorado River Ecosystem. Report 

prepared for the Glen Canyon Dam Adaptive Management Program. 

Assess genetics of humpback chub being held at Willow Beach National Fish Hatchery for their 

potential as a refugium stock and as brood stock for captive propagation. COMPLETED: 

Strand, A. 2006. Analysis of a preliminary microsatellite dataset for wild and captive 

populations of Humpback chub, Gila cypha. 

Determine feasibility of developing a program to augment the population of humpback chub 

(Gila cypha) in Grand Canyon. COMPLETED: Van Haverbeke, D. R. and R. L. Simmonds. 

2004. The feasibility of developing a program to augment the population of humpback chub 

(Gila cypha) in Grand Canyon. Final Report, July 2004. Document No. - USFWS-AZFRO-FL03-007. 

Humpback Chub Hatchery Evaluation and Evaluation of Prospective Refuge Facilities. 

COMPLETED: Childs, M. 2005. Humpback chub hatchery evaluation: prospective refuge 

facilities. Arizona Game and Fish Department, Research Branch, Heritage Program, May 2005. 

Improve rearing habitat for early life stage humpback chub in the Little Colorado River to 

improve growth and survival, particularly of those individuals who would disperse to the 

mainstream. REPLACED BY PROJECT 7.

Mechanical removal of warm-water nonnative fishes from the Colorado River in Grand Canyon. 

COMBINED WITH PROJECT 9B.

Monitoring humpback chub in the Little Colorado River above Chute Falls COMBINED WITH 

PROJECT 13B.

Conduct concurrent estimates of humpback chub in Little Colorado River and mainstem to 

develop/confirm population estimates. Evaluate the age group survivability for all age classes, 

including recruitment. COMBINED WITH PROJECT 13B.

Develop an Adaptive Management Work Group Outreach Program. COMPLETED: 

http://www.AMP.gov/index.html. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 100

APPENDIX F. Conservation Measures 

Conservation measures from the Final Biological Opinion for the Operation of Glen 

Canyon Dam, February 27, 2008 

Humpback Chub 

Humpback Chub Consultation Trigger – Pursuant to 50 CFR § 402.16 (c), reinitiation of 

formal consultation is required and shall be requested by the Federal agency or by the FWS, 

where discretionary Federal involvement or control over the action has been retained or is 

authorized by law and if new information reveals effects of the action that may affect listed 

species or critical habitat in a manner or to an extent not previously considered. Reclamation 

and FWS agree to specifically define this reinitiation trigger relative to humpback chub, in part, 

as being exceeded if the population of adult humpback chub (≥200 mm [7.87 in] TL) in Grand 

Canyon declines significantly, or, if in any single year, based on the age-structured mark 

recapture model (ASMR; Coggins 2007), the population drops below 3,500 adult fish within the 

95 percent confidence interval. FWS and Reclamation have agreed on this trigger based on the 

current estimated population size and past population trend, genetic considerations, and the 

capabilities of the ASMR model to estimate population size. This number was derived as a 

conservative approach to preventing the population from declining to the minimum viable 

population size for humpback chub, estimated to be 2,100 adult fish (U.S. Fish and Wildlife 

Service 2002a), with consideration for a buffer and acknowledging the variance inherent in the 

ASMR resulting from age estimation based on recent results from this model (Coggins 2007). 

This trigger provides additional protection against possible adverse affects to humpback chub 

from the proposed action. If the population of humpback chub declines to this level, 

Reclamation and FWS will consider appropriate actions through reinitiated section 7 

consultation, for example, extending the period of steady releases to include July and August. 

Conversely, if the population of humpback chub expands significantly, FWS and Reclamation 

will consider the potential for reinitiation of consultation to determine if steady flows continue to 

be necessary. 

Comprehensive Plan for the Management and Conservation of Humpback Chub in Grand 

Canyon – Reclamation has been a primary contributor to the development of the AMP’s 

Comprehensive Plan for the Management and Conservation of Humpback Chub in Grand 

Canyon. Reclamation will continue to work with AMP cooperators to develop a comprehensive 

approach to management of humpback chub. Reclamation has committed to specific 

conservation measures in this biological opinion, but will also consider funding and 

implementing other actions not identified here to implement the plan. 

Humpback Chub Translocation – In coordination with other Department of the Interior (DOI) 

AMP participants and through the AMP, Reclamation will assist NPS and the AMP in funding 

and implementation of translocation of humpback chub into tributaries of the Colorado River in 

Marble and Grand canyons. Nonnative control in these tributaries will be an essential precursor 

to translocation, so Reclamation will help fund control of both cold and warm-water nonnative 

fish in tributaries, as well as efforts to translocate humpback chub into these tributaries. Havasu, 

Shinumo and Bright Angel creeks will initially be targeted for translocation, although other 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 101

tributaries may be considered. Reclamation will work with FWS, NPS and other cooperators to 

develop translocation plans for each of these streams, utilizing existing information available 

such as SWCA and Grand Canyon Wildlands (2007) and Valdez et al. (2000a). These plans will 

consider and utilize genetic assessments (Douglas and Douglas 2007, Keeler-Foster in prep.), 

identify legal requirements and jurisdictional issues, methods, and assess needs for nonnative 

control, monitoring and other logistics, as well as an implementation schedule, funding sources, 

and permitting. Reclamation and the AMP will also fund and implement translocation of up to 

500 young humpback chub from the lower Little Colorado River to above Chute Falls in 2008 if 

FWS determines that a translocation is warranted. Reclamation and the AMP will continue to 

monitor humpback chub in the reach of the Little Colorado River above Chute Falls for the 5-

year period of the proposed action, and will undertake additional translocations above Chute 

Falls as deemed necessary by FWS. 

Nonnative Fish Control – As first presented in the biological opinion on the Shortage 

Guidelines, Reclamation will, in coordination with other DOI AMP participants and through the 

AMP, continue efforts to assist NPS and the AMP in control of both cold- and warm-water 

nonnative fish species in both the mainstem of Marble and Grand canyons and in their 

tributaries, including determining and implementing levels of nonnative fish control as 

necessary. Because Reclamation predicts that dam releases will be cool to cold during the period 

of the proposed action, control of nonnative trout may be particularly important. Control of 

these species will utilize mechanical removal, similar to recent efforts by the AMP, and may 

utilize other methods, to help to reduce this threat. GCMRC is preparing a nonnative fish control 

plan through the AMP process that addresses both cold and warm-water species that will further 

guide implementation of this conservation measure. 

Humpback Chub Nearshore Ecology Study ¬– In coordination with other DOI AMP 

participants and through the AMP, Reclamation will implement a nearshore ecology study that 

will relate river flow variables to ecological attributes of nearshore habitats (velocity, depth, 

temperature, productivity, etc.) and the relative importance of such habitat conditions to 

important life stages of native and nonnative fishes. This study will incorporate planned science 

activities for evaluating the high flow test on nearshore habitats as well as the 5-year period of 

steady flow releases in September and October. A research plan will be developed with FWS via 

the AMP for this study by August 1, 2008, and a 5-year review report will be completed by 

2013. The plan will include monitoring of sufficient intensity to ensure significant relationships 

can be established, as acceptable to the FWS. This conservation measure is consistent with the 

Sediment Research conservation measure in the Shortage Guidelines biological opinion. This 

study will help clarify the relationship between flows and mainstem habitat characteristics and 

availability for young-of-year and juvenile humpback chub, other native fish, and competitive or 

predaceous nonnative fish, and support continued management to sustain mainstem aggregations. 

The feasibility and effectiveness of marking small humpback chub (<150 and <100 mm TL [5.91 

and 3.93 in]) will also be evaluated as part of the study, and if effective, marking young fish will 

be utilized in the study. Marking young humpback chub, if feasible and effective, could greatly 

aid in developing information on the early life history, growth and survival of young humpback 

chub. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 102

Monthly Flow Transition Study – Transitions between monthly flow volumes can often result 

in drastic changes to nearshore habitats. For example, past transitions from August to September 

in some years have consisted of a transition from a lower limit of 10,000 cfs in August to an 

upper limit of 10,000 cfs in September. Such a transition results in a river stage level that is 

below the varial zone of the previous month’s flow, and may be detrimental to fishes and food 

base for fish. Reclamation has committed to adjusting daily flows between months to attempt to 

attenuate these transitions such that they are more gradual, and to studying the biological effects 

of these transitions, in particular to humpback chub. If possible, Reclamation will work to adjust 

September and October monthly flow volumes to achieve improved conditions for young-ofyear, juvenile, and adult humpback chub, as acceptable to the FWS. 

Humpback Chub Refuge – Once appropriate planning documents are in place, and refuge 

populations of humpback chub are created (as a conservation measure of the Shortage Guidelines 

biological opinion), Reclamation will assist FWS in maintenance of a humpback chub refuge 

population at a Federal hatchery or other appropriate facility by providing funding to assist in 

annual maintenance. In case of a catastrophic loss of the Grand Canyon population of humpback 

chub, a humpback chub refuge will provide a permanent source of sufficient numbers of 

genetically representative stock for repatriating the species. This action would also be an 

important step toward attaining recovery. 

Little Colorado River Watershed Planning – Reclamation will continue its efforts to help 

other stakeholders in the Little Colorado River watershed develop watershed planning efforts, 

with consideration for watershed level effects to the humpback chub in Grand Canyon. 

Kanab Ambersnail 

Habitat Protection – Reclamation will, through the AMP, temporarily remove and safe-guard 

all Kanab ambersnails found in the zone that would be inundated during the high flow test, as 

well as approximately 15 percent (17 m2 [180 ft2]) of the Kanab ambersnail habitat that would 

be flooded by the experimental high flow test. The ambersnails would be released above the 

inundation zone, and habitat would be held locally above the level of inundation until the high 

flow test has ended (approximately 60 hours). Habitat will be replaced in a manner that will 

facilitate regrowth of vegetation. Subsequent monitoring of this conservation measure will be 

coordinated with GCMRC. 

Conservation measures from the Final Biological Opinion for the Proposed Adoption of 

Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated 

Operations for Lake Powell and Lake Mead, December 12, 2007 

Humpback Chub 

Nonnative Fish Control – In coordination with other DOI AMP participants and through the 

AMP, Reclamation will continue efforts to control both cold- and warm-water nonnative fish 

species in the mainstem of Marble and Grand canyons, including determining and implementing 

levels of nonnative fish control as necessary. Control of these species using mechanical removal 

and other methods will help to reduce this threat. 
Draft Humpback Chub Comprehensive Plan – June 16, 2009 103

Humpback Chub Refuge – Reclamation will assist FWS in development and funding of a 

broodstock management plan and creation and maintenance of a humpback chub refuge 

population at a Federal hatchery or other appropriate facility by providing expedited 

advancement of $200,000 in funding to the FWS during CY 2008; this amount shall be funded 

from, and within, the amount identified in the MSCP BO (FWS 2005a; page 26). Creation of a 

humpback chub refuge will reduce or eliminate the potential for a catastrophic loss of the Grand 

Canyon population of humpback chub by providing a permanent source of genetically 

representative stock for repatriating the species. 

Genetic Biocontrol Symposium – Reclamation will transfer up to $20,000 in fiscal year 2008 to 

FWS to help fund an international symposium on the use and development of genetic biocontrol 

of nonnative invasive aquatic species which is tentatively scheduled for October 2009. Although 

only in its infancy, genetic biocontrol of nonnative species is attracting worldwide attention as a 

potential method of controlling aquatic invasive species. Helping fund an effort to bring 

researchers together will further awareness of this potential method of control and help mobilize 

efforts for its research and development. 

Sediment Research – In coordination with other DOI AMP participants and through the AMP, 

Reclamation will monitor the effect of sediment transport on humpback chub habitat and will 

work with the GCMRC to develop and implement a scientific monitoring plan acceptable to 

FWS. Although the effects of dam operation-related changes in sediment transport on 

humpback chub habitat are not well understood, humpback chub are known to utilize backwaters 

and other habitat features that require fine sediment for their formation and maintenance. 

Additional research will help clarify this relationship. 

 

Parasite Monitoring – In coordination with other DOI AMP participants and through the AMP, 

Reclamation will continue to support research on the effects of Asian tapeworm 

(Bothriocephalus acheilognathi) on humpback chub and potential methods to control this 

parasite. Continuing research will help better understand the degree of this threat and the 

potential for management actions to minimize it. 

Kanab Ambersnail 

Monitoring and Research – Through the AMP, Reclamation will continue to monitor Kanab 

ambersnail and its habitat in Grand Canyon and the effect of dam releases on the species, and 

Reclamation will also continue to assist FWS in funding morphometric and genetic research to 

better determine the taxonomic status of the subspecies. 

Southwestern Willow Flycatcher 

Monitoring and Research – Through the AMP, Reclamation will continue to monitor 

southwestern willow flycatcher and its habitat and the effect of dam releases on the species 

throughout Grand Canyon and report findings to FWS, and will work with the National Park 

Service (NPS) and other AMP participants to identify actions to conserve the flycatcher. 
A REVIEW OF 

A COMPREHENSIVE PLAN FOR THE MANAGEMENT 

AND CONSERVATION OF HUMPBACK CHUB (GILA CYPHA) 

IN GRAND CANYON, ARIZONA 

BY 

GCD AMP SCIENCE ADVISORS 

JUNE, 2007 
2

A REVIEW OF 

A COMPREHENSIVE PLAN FOR THE MANAGEMENT 

AND CONSERVATION OF HUMPBACK CHUB (GILA CYPHA) 

IN GRAND CANYON, ARIZONA 

BY 

GLEN CANYON DAM ADAPTIVE MANAGEMENT PROGRAM 

(GCD AMP) SCIENCE ADVISORS1

INTRODUCTION AND BACKGROUND 

 

In 2003, the Adaptive Management Work Group (AMWG) formed an Ad Hoc 

Committee to respond to science analyses developed between 2000 and 2002 that suggested the 

adult Humpback Chub (HBC) populations in the Grand Canyon area were in significant decline 

and approaching minimal viable population levels. That Ad Hoc Committee deliberated and 

proposed a broad set of actions to insure that chub populations be protected and enhanced and 

that new knowledge bases be created. Those recommendations were summarized in an initial 

draft set of Humpback Chub Actions. 

 By 2005 several of the key management action recommendations were being 

implemented by managers. These activities included predation control experiments, the 

evaluation of refugia, and translocation of fish, among others. In 2005 the AMP science 

community released additional assessments in the Score Report that sustained the argument that 

the HBC adult populations were continuing to decline and approaching critical minimal levels. 

The AMWG decided to continue the HBC Ad Hoc Committee and broaden its charge to develop 

the original set of proposed HBC actions into a HBC Comprehensive Plan that would: 

 Describe linkages, sequences and feed back loops among projects 

 Identify project priorities and completion timelines 

 

1

 The GCD AMP Science Advisors include Dale Robertson, USGS; Jill Baron, USGS; Virginia Dale, Oak Ridge 

Laboratories; Jim Kitchell, University of Wisconsin; Lance Gunderson, Emory University; Don Fowler, University 

of Nevada Reno; Harold Tyus, University of Colordo Boulder; and Lawrence D. Garrett, M3 Research, as the 

Executive Secretary. Due to conflicts Jim Kitchell could not contribute to this review. 
3

 Identify a broad array of alternatives that address threats, define criteria and steps for 

action should a crisis develop; i.e., severe population decline 

An Implementation Committee was also formed by AMWG to: 

 Determine proposed actions that would be completed under GCD AMP and, 

 Explore opportunities to complete actions that did not fall under AMP direction. 

In 2005 the science advisors reviewed the initial draft HBC Actions, and recommended 

the document be improved in two areas. The first would be to more clearly articulate the goals 

and objectives of the program, and the second was to clarify how management activities, 

programs and projects would meet those goals and objectives. That plan was revised, and a 

revised draft was completed in 2007 under the title; A Comprehensive Plan For The 

Management and Conservation of Humpback Chub (Gila cypha) In Grand Canyon, Arizona. 

The remainder of this report provides comments and suggestions on the 2007 Comprehensive 

Plan. 

GENERAL COMMENTS ON PLAN 

 The 2007 HBC Comprehensive Plan represents significant improvement over the 2005 

document, in that goals and objectives are more clearly specified in Sections 4.0, 4.1 and 4.3 and 

implementation strategies and procedures are articulated more clearly in Sections 5.0-5.4 and in 

Appendix B in association with individual projects. 

 However, we do not feel this document, as presented, is a “Comprehensive Plan” of the 

GCD AMP for HBC science and management programs, but more clearly a “HBC 

Comprehensive Activities Proposal”. We suggest using the former title connotes a much more 

robust treatment of science and management planning than is intended for this document. For 

example, the former would include more extensive treatment of project schedules, procedures, 

linkages, budgets, etc. than is provided in this plan. Further, it would also include more 

extensive contingency planning to address potential threats to the HBC. Without these changes, 

a title change might be considered. 

 There is concern about mixed reference to the intent or goal of the proposed activities to 

contribute to “HBC recovery” and “removal of jeopardy”. There is no official recovery 

implementation program for the HBC in the Grand Canyon segment of the Colorado River and 

these references should be dropped. There is an official jeopardy opinion and the proposed 
4

activities clearly address necessary and prudent actions under the opinion. That should be the 

basis for the plan. 

The 2007 draft plan addresses present GCDAMP efforts for conservation of the 

humpback chub (HBC) in the Grand Canyon. It contains a great deal of important information 

but it still could be improved in focus, organization and clarity. It needs to be issue driven and 

clearly specify applied science as the paradigm for management of conservation problems. 

Because of a potential diverse audience, the report could benefit from an abstract or executive 

summary section, and a conclusions section. These will aid comprehension and use as a briefing 

document. 

The purpose of the GCDAMP as stated in the “Background” section of the report is: “to 

make recommendations to the Secretary of the Interior regarding Glen Canyon Dam operating 

criteria and effects on downstream resources”. Clearly, the focus of the document should be on 

the effects caused by the operation of the dam on the humpback chub. It should contain enough 

information about past and proposed future operation of the dam, including resultant effects on 

the population and habitats of the fish, to allow policy makers at various government levels and 

disciplines to understand implicated cause and effect relationships. The document correctly 

identifies GCDAMP goals for the humpback chub as those needed to avoid jeopardizing the 

continued existence of the species and destruction or adverse modification of critical habitat. 

These goals are the direct result of the Section 7 ESA finding from the U.S. Fish and Wildlife 

Service, which is a mandate to the Bureau of Reclamation as a federal agency affected by the 

Act. These goals may be related to recovery issues, but they are not sufficient or intended to 

result in recovery of the species. By organizing the document by broad recovery goals the focus 

on adverse effects caused by operation of GCD is obscured and clarity lost. 

We suggest text revisions wherein the focus of the science and management activities 

proposed would be on the actions to remove jeopardy and not on recovery. This is currently 

partly obscured in the text by discussions arranged around recovery goals. However, it is clearly 

stated in Appendix B in introducing all proposed projects as follows. “All projects are directed 

at achieving Goal 2 of the GCDAMP, which is to maintain or attain viable populations of 

existing native fish, remove jeopardy for humpback chub and razorback sucker, and prevent 

adverse modification to their critical habitat”. This statement does raise another general 
5

question. Does it mean that there will be comprehensive plans to address other general 

questions? Should other native fishes and razorback sucker be considered as part of this 

comprehensive plan? 

SPECIFIC COMMENTS ON VARIOUS SECTIONS OF THE PLAN 

 1.0 Introduction. An effective Introduction section should clearly identify and define

the problem being addressed, provide a review of relevant information to orient the reader, and 

indicate how an investigation might proceed on selected goals. Subheadings in the introduction 

might include, General, Environmental Setting, Effect of Dam on Grand Canyon HBC, Program 

Goals, etc. 

The present Introduction section goals statement should be rewritten i.e., “The GCDAMP 

goals for humpback chub are to operate GCD to maintain or attain, etc.” 

The introduction section should clearly identify the purpose of this report in a straight 

forward manner to provide the reviewer with the nature and scope of the problem being 

addressed. At present it is more like a preface to the report than an introduction. 

The goals appear to be correctly stated and the audience is targeted, however the focus 

here should be directed to the effects caused by the operation of Glen Canyon Dam. There 

should be a brief discussion of the historic environmental setting of the Colorado River and 

associated riparian zone in Grand Canyon, and the environmental impacts associated with the 

construction and operation of Glen Canyon Dam. 

It should be clearly noted that construction effects of the dam occurred before 1973 and 

are thus not under Section 7 authority, while operations of the dam are. The plan should identify 

potential downstream impacts on HBC associated with operation of the dam in a general way 

that have affected the fish “e.g. changes in the river caused by the dam”. (Chapter 6, NRC 

1996). In this way, the Plan would provide the necessary background for identifying how the 

environment for humpback chub has been changed by the dam, and for seeking ways to avoid or 

mitigate those effects that pose a threat to the fish. At a minimum, it is necessary to identify the 

magnitude of changes that have occurred to historic habitat, changes that constitute a threat, and 

how threats might be avoided or reduced by operation of the dam. 
6

In addition to a summary of past findings about effects of dam operation, the Introduction 

section also should relate how future impacts will be evaluated, i.e., what methodology will be 

used to evaluate/rank perceived threats, how future studies will be selected or ranked, etc. 

 1.1 Background. This section could be summarized into a preface or as one paragraph 

in the introduction. Use of acronyms should be minimized. 

2.0 Status of Humpback Chub in the Colorado River Basin. This subsection should be 

merged with other information and placed in the Introduction section in a subsection dedicated to 

the environmental setting. The first part (2.1) is confusing. What is the significance of humpback 

chub aggregations? What are the sizes of these aggregations? Are these aggregations purported 

subpopulations or just places where a certain life history stage is captured? 

You might want to consider a first sentence that reads; “There is one known population 

of HBC in GC, and 9 locations support higher densities of the fish”. Two different views about 

population size of HBC in GC are given on P 3. The authors should resolve the differences in 

those numbers clearly with reference to the scientific basis for each number. The presentation 

should have sufficient scientific rigor and clarity to convince the reader that the population 

values determined earlier (2002-2005) were not as accurate as values determined in 2006. For 

example, why in a five year period has the AMP position on this species shifted from near 

apparent crisis to a position of a stable adult population of 5000 adult fish. These measures are 

the driving force in major policy shifts and require clear scientific explanation. 

As presented in this document, the concept of stabilizing a declining population is 

confusing. Results of sampling the humpback chub population show a declining post-dam 

trajectory from 1989, with no detectable increase and further, that declines below 2100 

individuals would presumably occur in 10 to 15 years. Perhaps the wording could be changed to: 

“presently stabilized at a lower level" to avoid giving the impression that the population is 

recovering. The humpback chub population in Grand Canyon apparently is supported entirely by 

habitat in the Little Colorado River and may be at or near the capacity of the Little Colorado 

River to support it. At present it seems that the few adult chub in the mainstream are not 

contributing to population size. 

In the last paragraph on P 3, the current population is given as 5,000 fish, presumably a 

population mean? In view of the importance of this number it requires more elucidation. The 
7

value should be given as a mean with appropriate confidence limits. To be meaningful, this 

population value should be considered with respect to the presumed size of the historic 

population of humpback chub in the affected area, such as a percent of the historic size. 

A discussion of minimum viable population (MVP) size in respect to the humpback chub 

in Grand Canyon would be helpful. It appears that the Grand Canyon fish are isolated from 

humpback chub populations in the remainder of the Colorado River basin. Thus, downlisting 

criteria provided earlier will probably need revision if the Grand Canyon/Little Colorado 

population is isolated and not considered part of a larger metapopulation . In this case MVP 

requirements may be greater than the 2100 number that is often given to protect local 

adaptations. For wild vertebrate populations this number could be near 7000 individuals to 

insure persistence (e.g. 99% confidence of persistence for 40 generations; Reed et al. 2003). All 

animal populations will fluctuate, and maintenance of a target population size will require a 

much larger geometric mean population size to avoid future fluctuations that could reduce the 

number below the target. (e.g., see Thomas 1990, Reed et. al. 2003). If such a target population 

size cannot be determined at this time, those factors that need to be considered for doing so in the 

future should be identified. 

Section 2.2 gives status of HBC in the upper Colorado river basin. We suggest that this 

be changed to status in the entire basin and provide the same information in table 1 for all areas 

for comparison, and appear before information presented in the present Section 2.1. In Table 1, 

“Occasions” needs to be defined. What percentage of the historic HBC range remains? 

The last paragraph on P 4 seems out of place. Perhaps this should be merged with a 

Preface or placed in the Introduction after some rewriting. 

There appears to be two Section 2.2, one on P 3 and the other on P 5. We suggest that the 

Section 2.2 beginning on P 5 be removed or placed in an appendix. It adds little to this report. 

3.0 Threats to Humpback Chub. This should be renamed, “Threats to Humpback chub 

from GCD Operation”. As presented, some threats are not threats (e.g. food base is not a threat, 

but a declining food base is a threat). Also, threats should be organized according to those 

changes from historic conditions that have resulted from operation of the dam, e.g., hydrological 

change, changes in water temperature, and changes in sediment or turbidity. 
8

We think the Plan would be greatly improved by using some type of conceptual approach 

to indicate the magnitude and interaction of various threats. The use of Recovery Factors A - E 

are inappropriate and confusing because the goal of this plan is to reduce jeopardy and avoid 

adverse modification of critical habitat from operation of GCD, not species recovery. 
9

It could be argued that some threats listed are not directly or indirectly attributable 

to operation of GCD. However, it must be recognized that operation of the dam has 

reduced the abundance and distribution of humpback chub in the GC. Extinctions of 

widespread species have been associated with major events that produce stresses of the 

type or magnitude not previously been experienced by the species. Such an event can 

result in a lower population size and restricted range, which make the species vulnerable 

to stresses that would previously have had little or no effect. 

It might be argued that HBC population vulnerability to disease, handling, 

contaminants, and other impacts may be related to construction and operation of GCD. In 

other words, GCD was a major event (i.e., catastrophic) that could have made the HBC 

vulnerable to stressors that would not normally have threatened its historic population. As 

a major event, GCD has at least three catastrophic components for the fish. The first is 

habitat destruction and alteration on a major scale, the second is fragmentation of range 

and the third is the speed at which it was accomplished. Natural processes would have 

taken thousands of years to accomplish such changes and thus natural selection cannot 

produce adaptations fast enough to compensate. 

How were five threats identified for immediate attention, P 8, last paragraph.? 

(Note: six items were presented on P 9 instead of five). The process needs to be outlined. 

We suggest that these threats be highlighted after they have been identified in the 

preceding section. Add to “Cold water releases” an increase in predation risk in HBC. 

The part about “Flow regimes from dam releases” is inadequate. Much is known about 

the impact of flows on the habitat and life histories of native fishes. The part on “Threat 

interactions” needs to be expanded. Reduced population size and restricted range of 

HBC induces vulnerability to multiple threats. This section should be immediately 

followed by another section that address how each threat will be reduced by changing 

GCD operation or by further study to find out how it could be changed. Instead the next 

section (4.0) falls short of this need, and needs to be more robust. 

The Strategy for Improving Conditions for Humpback Chub. This section 

should provide contingency planning for dealing with threats identified in previous 

sections and needs to include a list of recommendations to avoid jeopardy from the 

operation of GCD. Instead it purports to expand that goal to include assisting in 
10

achieving recovery goals in the Grand Canyon. It should be stated that avoiding jeopardy 

will assist in achieving recovery goals, and thus it is not a new concept. However, this 

choice of direction clouds the real issue. Even though the actions needed to remove the 

threats imposed by GCD also are related to recovery, they cannot result in recovery 

unless the fish is also recovered elsewhere in the basin. Thus, the concept introduced 

here of recovery in the Grand Canyon seems obscure. Perhaps it should be restated to 

assist with recovery of the fish throughout its range, or in keeping with the theme, to 

indicate the goal is to avoid jeopardy which also will assist in attaining recovery goals. 

Separating section 4.0 from the rest of the document adds nothing and results in 

more confusion. We recommend that this section be significantly revised as stated 

above, or be dropped and the items listed under Sections 4.1, 4.2, and 4.3, be included 

with the rest of the items included as threats to the fish associated with the operation of 

GCD, and how to avoid threats as stated above. 

The Strategy Implementation Section. This section, including proposed projects

is not a strategic approach for implementing actions to reduce the threat of jeopardy from 

operation of GCD. Instead it seems that a tactical approach is used by promoting various 

projects whose value in addressing strategic needs is not presented. Although it is 

intuitive that the GCD Operations project would be ranked high, it was ranked at the 

bottom (i.e., 13 out of 14 projects; Appendix C). 

In this section, various projects are listed but they are not directly linked to 

specific threats identified earlier. To be effective, the Plan should identify threats, 

prioritize the threats for needed action, and indicate which projects address them. In that 

way, progress toward avoiding jeopardy could be assessed. 

Instead the projects seem to have a life of their own. For example, projects are 

prioritized in Section 5.2, but the threats are not. Under the circumstances, ranking of 

projects seems a moot exercise. 

Reducing the Threat of Catastrophic Events. This section discusses two 

catastrophic events but the two could be combined. Regarding threat of extinction, a 

catastrophic event leading to extinction has been considered a natural or human change in 

the environment that species have not experienced and thus have not developed 

adaptations in response. In this context, construction and operation of GCD is a 
11

catastrophic event because of the magnitude of habitat destruction and the rapidity of its 

action. 

Section 5.4 Implications of Implementation. This section appears to be added as 

an after thought. It is an important issue, but as written it does not contribute to the 

document. The authors might want to consider developing a general risk differential 

assessment of implementing such a high cost program with related probabilities of 

success in various areas. It could provide some guidance on where budgets, at least in the 

short run, might best be spent. 

Conclusions. This plan has no conclusion section. It needs one to indicate the 

direction of the program and to summarize progress in avoiding jeopardy to HBC. 

Without some sort of summary or conclusion one is left to ponder what is the point of 

this document. 

Appendix B. Appendix B is significantly expanded from the previous SA review 

of this document. And, the additional information provided on most projects does help 

the reader understand selected elements of each project. However, the section could be 

improved significantly by documenting information that reviewers could use in 

evaluating the collection of projects as a “program”. 

 First and foremost, a schematic or figure that provides an overall design as to how 

the projects are linked would be most helpful. Second, a table outlining several critical 

elements of each study would be helpful in better understanding each project, but also 

how the projects are integrated as a program. The authors might consider the following 

elements to describe each project and project linkages. 

 Project title and area of contribution; i.e., predation, food base, etc. 

 Objectives 

 General procedures 

 Linkage to other projects or management 

 Science understanding sought 

 Appendix C. Project Ranking. Ranking of these projects by this small group does 

not seem to be a useful exercise. It could be a partial set of information from 

stakeholders that might be improperly used by policy makers. 

References 
12

Reed, D.H., J.J. O'Grady, B.W. Brook, J.D. Ballou and R. Frankham. 2003. Estimates of 

minimum viable population sizes for vertebrates and factors influencing those estimates. 

Biological Conservation 113(1):23-34 

Thomas, C.D. 1990. What do real population dynamics tell us about minimum viable 

population sizes? Conservation Biology 4:323-327 
1 

DRAFT 

Humpback Chub Comprehensive Plan Ad Hoc Group Response to the June 2007 

Science Advisors’ Review of March 2007 Comprehensive Plan for the Management 

and Conservation of Humpback Chub (Gila cypha) in the Lower Colorado River 

Basin 

February 17, 2009 

Introduction 

This document is a summary of the comments received in a review by the Glen Canyon 

Dam Adaptive Management Program (AMP) Science Advisors of a document created by 

the Technical Work Group Humpback Chub Comprehensive Plan Ad Hoc Group (Ad 

Hoc) “A Comprehensive Plan for the Management and Conservation of Humpback Chub 

(Gila cypha) in Grand Canyon, Arizona” (Plan). The Ad Hoc provides a summary of the 

review by attempting to identify specific comments and provides a brief response to each 

identified comment, but the Ad Hoc refers the reader to the revised Plan and the June 

2007 Science Advisor review for more information. 

Comments and Ad Hoc Responses 

1. The Plan is a comprehensive list of projects, not a comprehensive plan; consider 

“HBC Comprehensive Activities Proposal” for the title. Or include more extensive 

treatment of project schedules, procedures, linkages, budgets, etc. than is provided 

in this plan. 

The Ad Hoc felt the title was appropriate, although the title has been changed to more 

accurately describe the geographic and programmatic scope. Also, a new table has been 

added that provides additional information regarding projects. The Ad Hoc feels that the 

detailed level of planning requested by the science advisors would be more appropriately 

accomplished by a recovery program, in concert with stakeholders tasked specifically 

with achieving recovery. While the AMP Comprehensive Plan will help guide such an 

effort, we lack the resources to provide that level of detail here. 

2. Plan should focus on removal of jeopardy, because a recovery program is not in 

place in Grand Canyon. 

The Adaptive Management Work Group (AMWG) motion that directed the revision of 

the Comprehensive Plan directed the Ad Hoc to identify actions to be taken that can be 

both accomplished within the AMP and those that may be considered outside the 

authority of the AMP. Thus, the Ad Hoc strived to create a plan to conserve the lower 

Colorado River basin recovery unit of humpback chub, as defined by the U.S. Fish and 

Wildlife Service. However, the plan is not a recovery plan or an outline for a recovery 

program. The Ad Hoc Group utilized the 2002 U.S. Fish and Wildlife Service 

Humpback Chub Recovery Goals and the 2008 Draft Revised Recovery Goals as the best 
2 

available information in preparation of the plan. A recovery program for the lower basin 

recovery unit in Grand Canyon is an identified need by the AMP. In a May 21, 2007, 

response to a December 6, 2006, Adaptive Management Work Group (AMWG) motion, 

in which the AMWG recommended that the Secretary of Interior task the U.S. Fish and 

Wildlife Service with developing a lower Colorado River Recovery Program to include 

humpback chub in Grand Canyon, Deputy Secretary Lynn Scarlett tasked the U.S. Fish 

and Wildlife Service with providing feedback to AMWG on a timeline, scope, and 

development of an outreach program to potentially involved stakeholders, and report 

findings to the DOI Policy Group and identify information needs to develop a recovery 

program. In response to this charge, the U.S. Fish and Wildlife Service created the 

“Draft Recovery Implementation Program (RIP) for the Humpback Chub (Gila cypha) in 

the Grand Canyon: Report on Analysis and Recommendations to Support Stakeholder 

Driven Outreach Program and Identification of Information Needs.” This draft report 

utilizes information from the Comprehensive Plan. The Ad Hoc also added sections in 

the report to better explain the meaning of recovery, recovery units, and the lower 

Colorado River basin recovery unit of humpback chub. 

3. Improve focus, organization, and clarity of the report, and use applied science as 

a paradigm. Add abstract and conclusions. 

The Ad Hoc added an abstract, preface, conclusions, and a discussion section, and 

provided additional information and tables to clarify the report. 

4. Document should focus on the effects caused by the operation of the dam on the 

humpback chub, because this is the limit of Glen Canyon Dam AMP. 

The responsibilities of the Adaptive Management Work Group as delineated in Bureau of 

Reclamation’s 1995 Glen Canyon Dam Environmental Impact Statement, include the 

following: 

“Develops recommendations to the Secretary of the Interior for modifying operating 

criteria and other resource management actions, policies, or procedures.” 

Further, the AMWG specifically directed in 2003 that the ad hoc “consider actions to 

implement a comprehensive research and management program for the humpback chub” 

and then in 2005, directed “the creation of a humpback chub implementation plan Ad 

Hoc Group” to “1. Determine which actions identified in the humpback chub 

comprehensive plan can be accomplished under the Glen Canyon Dam AMP” and “2. 

Explore the various options for completing actions that do not fall under the authorities of 

the Glen Canyon Dam AMP.” 

5. Appendix B correctly introduces all proposed projects as follows: “All projects 

are directed at achieving Goal 2 of the Glen Canyon Dam AMP, which is to 

maintain or attain viable populations of existing native fish, remove jeopardy for 

humpback chub and razorback sucker, and prevent adverse modification to their 

critical habitat”. Will other comprehensive plans address other general questions? 
3 

Should other native fishes and razorback sucker be considered as part of this 

comprehensive plan? 

The Ad Hoc added a discussion of the relevance of the report to Goal 2 and other native 

fishes in Grand Canyon. Generally, the recommendations of the report would benefit all 

native fishes and therefore work to achieve Goal 2. 

6. The Introduction should identify and define the problem being addressed, 

provide a review of relevant information and indicate how investigations might 

proceed on selected goals. Consider including subheadings General, Environmental 

Setting, Effect of Dam on Grand Canyon HBC, Program Goals, etc. 

The Introduction section has been revised and other sections revised and added to clarify 

the plan. 

7. Introduction section goals statement should be rewritten i.e., “The Glen Canyon 

Dam AMP goals for humpback chub are to operate Glen Canyon Dam to maintain 

or attain, etc.” 

 

The AMWG charge to the Ad Hoc was to consider a comprehensive set of actions both 

within and outside of the AMP’s responsibility to present a comprehensive approach to 

management of humpback chub in the lower Colorado River basin. The Ad Hoc has 

developed the Plan to meet that charge. The Ad Hoc also added to language in the Plan 

to help explain the applicability to AMP Goal 2. 

8. Introduction is more like a preface. Focus should be directed to effects of 

operation of Glen Canyon Dam. Discuss the historic environment, impacts 

associated with the construction and operation of Glen Canyon Dam. Note 

construction effects occurred before 1973/ESA. Identify magnitude of changes from 

dam ops that have occurred, changes that constitute a threat, how threats might be 

avoided or reduced. 

The Ad Hoc provided additional information in the Introduction to attempt to better 

explain the role of the AMP in conservation of humpback chub and provided a Preface 

section. 

9. The Introduction section should relate how future impacts will be evaluated, i.e., 

what methodology will be used to evaluate/rank perceived threats, how future 

studies will be selected or ranked, etc. 

The Ad Hoc attempted to address prioritization throughout the document, and a 

discussion of methodology of threat prioritization has been added. However, the Ad Hoc 

found that it lacks the resources to provide thorough analysis of threat prioritization for 

this plan and suggests that a Recovery Program would be more appropriate to provide 

this. 
4 

10. Summarize “1.1 Background” into a one-paragraph preface. 

The Ad Hoc added a preface that provides information formerly in Section 1.1. 

11. Minimize use of acronyms. 

The Ad Hoc revised the report to reduce the use of acronyms. 

12. Merge 2.0 Status with other information and place in the Introduction as 

subsection. 

The Ad Hoc revised section 2.0 and the Introduction to address this comment. 

13. Define significance and sizes of these aggregations relative to subpopulations or 

locations where a certain life history stage is captured. 

The Ad Hoc made changes to the Plan to better define the aggregations, their size, 

location and significance to the Grand Canyon population. 

14. Clarify and explain shift in view about population size of HBC in GC (near 

apparent crisis to a stable adult population of 5000 adult fish). 

The Ad Hoc provided additional information on the status of the humpback chub in the 

lower Colorado River Basin. We refer to citations in the Plan utilized in the discussion of 

the status of the humpback chub for a complete discussion of the current status and 

changes in status over time. 

15. Define the statement “stabilizing a declining population.” Consider rewording 

to: “presently stabilized at a lower level.” Define the relationship of the Little 

Colorado River to the mainstem relative to the size of the humpback chub 

population. 

The Ad Hoc revised the section on status to explain that the status of humpback chub has 

apparently been in decline since monitoring began in the late 1980s but has improved 

and/or stabilized since about 2002. The lack of clarity on this issue is the result of the 

limitations of the current model in use to track humpback chub status, the Age-Structured 

Mark Recapture model, and we refer to relevant publications on the use of this model. 

16. Is the current population estimate of 5,000 fish a population mean? Add 

confidence limits, describe in relation to historical population size, percent of 

historical size. 

 

The Ad Hoc revised the status section to address this comment. 

17. Discuss the minimum viable population (MVP) size for humpback chub in 

Grand Canyon. Because the species is isolated in this part of its range, and not a 
5 

metapopulation, downlisting criteria may need revision. Consider 7000 individuals 

to insure persistence (e.g. 99% confidence of persistence for 40 generations) and 

larger geometric mean population size to avoid fluctuations that could reduce the 

number below the target. If such a target population size cannot be determined at 

this time, those factors that need to be considered for doing so in the future should 

be identified. 

The Ad Hoc felt that this discussion was outside its purview and more appropriately 

addressed in the ongoing revision of the U.S. Fish and Wildlife Services’ revision of the 

recovery goals for humpback chub, and forwarded this comment to the U.S. Fish and 

Wildlife Service. 

18. Change status to include entire basin and provide same info for all areas and 

move to an earlier section. List the percentage of historical humpback chub range 

that remains occupided. 

The Ad Hoc revised the status section to address this comment. 

19. Rewrite the section discussing the recovery goals revision and move to 

Preface/Introduction. 

The Ad Hoc made this revision. 

20. The numbering of sections is in error. Suggest removing Section 2.2 on page 5 

or place in an appendix. 

This numbering was a typo that the Ad Hoc corrected. The Ad Hoc also revised these 

sections and the Appendices to address this comment. 

21. Rename Section 3.0 Threats to “Threats to Humpback chub from Glen Canyon 

Dam Operation.” Food base is not a threat – redefine as declining food base. 

Organize according to changes from historic conditions, e.g., hydrological change, 

changes in water temperature, and changes in sediment or turbidity. 

The Ad Hoc respectfully disagrees with the scope of the Plan as discussed above, but did 

update threat information in the threats section (3.0) to better explain threats to humpback 

chub. 

22. The goal of the Plan should be to reduce jeopardy and avoid adverse 

modification of critical habitat from operation of Glen Canyon Dam, not species 

recovery. Use a conceptual approach to indicate the magnitude and interaction of 

various dam-related threats instead of Recovery Factors A – E. 

As explained above, the Ad Hoc respectfully disagrees with the Science Advisors view of 

the scope of the Plan and developed a comprehensive plan per the charge from AMWG. 
6 

23. Not all the threats listed are attributable to the operation of Glen Canyon Dam. 

However, the dam has resulted in reduced abundance and distribution of humpback 

chub. Lower population size and restricted range may make HBC more vulnerable 

to stresses that otherwise had little or no effect. Discuss threats in relation to Glen 

Canyon Dam. For example, vulnerability to disease, handling, contaminants, and 

other impacts may be related to construction and operation of Glen Canyon Dam. 

Glen Canyon Dam resulted in humpback chub being more vulnerable to stressors 

that would not normally have threatened its historic population via three 

catastrophic components: habitat destruction, fragmentation, speed of changes (too 

fast for natural selection to compensate). 

The Ad Hoc interpreted its charge as comprehensive, not limited to an examination of the 

threats directly attributable to Glen Canyon Dam. The Ad Hoc revised the discussion of 

threats in the Plan and added a discussion of the interaction of threats that should serve to 

address this comment. 

24. Define the threats identified for immediate attention. Suggest highlighting these 

after they have been identified in the preceding section. Add to “Cold water 

releases” an increase in predation risk in HBC. “Flow regimes from dam releases” 

is inadequate – more is known. Expand on “Threat interactions” (i.e. reduced 

population size and restricted range of HBC induces vulnerability to multiple 

threats). 

The Ad Hoc revised the threat discussion to better discuss the baseline conditions for 

humpback chub and the suite of threats to the species including how these threats can 

interact. 

25. Revise this section to address how each threat will be reduced by changing Glen 

Canyon Dam operations or by further study to find out how it could be changed. 

 The Ad Hoc found that dam operation is not the sole management action available to 

address the threats to humpback chub. The Ad Hoc has revised Section 4 to better 

explain how management actions can address threats, including dam operations. 

26. Provide contingency planning for identified threats, and recommendations only 

to avoid jeopardy from Glen Canyon Dam operation, not for assisting in achieving 

recovery goals in the Grand Canyon (although removing jeopardy assists recovery). 

Or restate purpose to assist with recovery of the fish throughout its range, or that 

goal is to avoid jeopardy which also will assist in attaining recovery goals. 

The Ad Hoc has attempted to revise the document to both better explain the relationship 

of the AMP to the recovery process for humpback chub and define how contingency 

planning for threats has been addressed. Contingency planning is met both with off site 

actions (creation of refuges) and within the wild with plans to prevent spills, for example, 

and overall through the improvement of habitat in the wild. 
7 

27. Consider deleting Section 4.0, or combine with Section 3.0 as to how to avoid 

threats as stated above. 

We have revised section 4.0, but, the Ad Hoc lacks the capability to develop a plan that 

fully responds to the comment. As stated above, the Ad Hoc feels that the plan is 

responsive to the AMWG charge, but cannot provide a complete analysis of how threats 

will be addressed because this is not an appropriate for the Ad Hoc and is the function of 

a recovery team and planning process. 

28. Section 5.0 is not a strategic approach for implementing actions to reduce the 

threat of jeopardy from operation of Glen Canyon Dam. The value of projects in 

addressing strategic needs is not presented. Why is Glen Canyon Dam Operations 

not ranked high, it was ranked at the bottom (i.e., 13 out of 14 projects; Appendix 

C). Plan should identify threats, prioritize threats, and indicate which projects 

address them (relative to jeopardy). Why rank projects if threats are not ranked. 

As explained above, the Ad Hoc is not the appropriate entity to fully address threats to 

the species, this is the purview of a recovery program. The Ad Hoc provided some 

additional discussion on the ranking of projects, and some additional discussion on the 

strategic elements that the projects are meant to address. 

29. Section 5.4 Implications of Implementation does not contribute to the document. 

Consider developing a general risk differential assessment for cost/benefit to 

prioritize budgets. 

The Ad Hoc felt that Section 5.4 was necessary to identify how implementation of the 

Plan could affect other AMP resources. Development of a general risk differential 

assessment is more appropriately addressed by a recovery program, or by the AMWG 

with regard to the overall AMP budget. 

30. Add a conclusions section to indicate direction of the program and summarize 

progress in avoiding jeopardy. 

The Ad Hoc added a conclusions section. 

31. Appendix B could be improved by documenting information that reviewers 

could use in evaluating the collection of projects as a “program.” Provide schematic 

or figure for the overall design as to how the projects are linked and a table 

outlining critical elements of each study. Consider these elements to describe 

projects and project linkages. 

• Project title and area of contribution; i.e., predation, food base, etc. 

• Objectives 

• General procedures 

• Linkage to other projects or management 

• Science understanding sought 

 
8 

The Ad Hoc revised Appendix B and added tables and a figure to address this comment. 

32. Appendix C Project Ranking is not useful, and likely to be misused – delete. 

The Ad Hoc has provided additional information about the project ranking process, as 

well as information on threat ranking methodology. The Ad Hoc determined that detailed 

threat ranking procedures are more appropriately carried out by a recovery program. The 

section was retained, with additional discussion on the limitations of the project ranking 

process.