ii
iii
iv
v
vi

Inch/Pound to SI

mile (mi) 1.609 kilometer (km)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

SI to Inch/Pound

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

kilogram (kg) 2.205 pound avoirdupois (lb)
1

On August 11, 2004 the AMWG passed the following motion: ―That GCMRC and TWG 

make a recommendation to AMWG in October 2004 on warm water species studies including a 

plan starting in January 2005‖. Subsequently on September 27, 2004 the TWG passed an additional 

motion: ―GCMRC will develop a process, a schedule, and a recommended budget for suppression 

and control of non-native fish (warm water species) to be presented to AMWG...‖. This document 

represents US Geological Survey (USGS) Grand Canyon Monitoring and Research Center‘s 

(GCMRC) effort to meet the intent of this motion. Here we present options for nonnative fish 

control and recommendations for monitoring and research following extensive reviews of literature 

and available data. This document is responsive to concerns brought forth during multiple reviews 

of this document from scientists, resource managers, the Tribes, and other stakeholders. These 

reviews modified the content of the document beyond the original AMWG motion and more 

towards an ecosystem approach to evaluating and addressing nonnative fish issues in Grand 

Canyon. GCMRC feels the progression and content of this document represents technically sound 

options for control of nonnative fish species and recommendations for addressing nonnative fish 

monitoring and research needs in Grand Canyon. Thus, this document provides the technical 

foundation for management agencies with statutory authority to initiate the development of a 

comprehensive management plan nonnative fishes for Grand Canyon. This document is not a 

management plan and is not intended to obligate management agencies or the AMP to implement 

any research or monitoring recommendations or control options presented herein. Implementation 

of control options presented in this document will be carried out in compliance with management 

agency policies, mandates, and tribal consultation requirements. This includes, but is not limited to, 

the requirements associated with the Endangered Species Act, National Environmental Policy Act, 

National Historic Preservation Act and Federal-Tribal Trust Responsibilities. Necessary 

compliance for the implementation of any nonnative fish control activity will be the responsibility 

of appropriate management agencies.

The Glen Canyon Dam Adaptive Management Program (GCDAMP) recommended that the 

U.S. Geological Survey‘s Grand Canyon Monitoring and Research Center develop a process, a 

 

1 U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Station, 

Flagstaff, Ariz.
2

schedule, and a recommended budget for suppression and control of non-native fish for the 

Colorado River in Grand Canyon. This document seeks to respond to that charge by describing a 

comprehensive approach for research, monitoring, and control actions related to nonnative fish 

species in the ecosystem. This document is consistent with GCDAMP goals to improve the status 

of native fish in Grand Canyon, especially the federally listed endangered humpback chub (Gila 

cypha), and to maintain a naturally reproducing population of rainbow trout (Oncorhynchus 

mykiss) above the Paria River to the extent practicable and consistent with the maintenance of 

viable populations of native fish.

The Colorado River and its tributaries in Grand Canyon are an interconnected system that 

includes a variety of fish habitats and species. As a result, the threats posed by nonnative fish to 

native species throughout the system are diverse and require a multifaceted management response.

To develop an appropriate response, this plandocument summarizes the history of nonnative fish 

management efforts in Grand Canyon, including an overview of recent efforts to protect native 

species through nonnative control projects. A review of current nonnative fish monitoring and 

sampling efforts and nonnative fish captures in Grand Canyon are also included. Existing 

information and data provide the basis for the research, management, and monitoring strategies 

presented in this plandocument. Developing a complete spectrum of nonnative fish monitoring and 

control methods and a risk assessment will take additional time.

An examination of recent and current fish sampling efforts reveals the need to improve 

nonnative fish monitoring, address information gaps, and facilitate the ability of managers to share 

information about and to rapidly respond to emerging and urgent threats caused by nonnative fish. 

Suggestions for making strides in these areas are included here. A review of exiting information 

also indicates that the long-term control of nonnative fish populations in Grand Canyon may 

require the control of nonnative species in the broader watershed. For example, source populations 

of nonnative fish that impact Grand Canyon native fish may originate outside of Grand Canyon and 

may not fall within the scope of the GCDAMP.

This plandocument outlines a comprehensive approach that prioritizes nonnative fish 

monitoring, removal, and research strategies for Grand Canyon. Monitoring recommendations 

proposed by this plandocument and presented in the order of their importance are as follows:

1. Expansion and diversification of current mainstem monitoring methods

2. Development of an early detection mechanism for alerting managers to nonnative fish 

invasions in Lees Ferry and the Colorado River from tributary sources 

3. Implementation of a long-term fish monitoring program for Grand Canyon tributary streams

Control options for nonnative fish proposed by this plandocument and presented in the 

order of their importance are as follows:

1. Maintenance of trout abundance in the Little Colorado River reach at 10 to 20 percent of 

January 2003 rainbow trout abundance (approximately 600 to 1,200 rainbow trout)

2. Continued removal of nonnative fish from tributaries including a) rainbow trout from

Shinumo Creek in association with humpback chub translocation efforts using backpack 

electrofishing in combination with other methods, b) trout species from Bright Angel Creek 

using a weir and backpack electrofishing.

3. Removal of channel catfish (Ictalurus punctatus) and bullhead species in and around the 

Little Colorado River

4. Chemical renovation and barrier construction in tributary streams identified as sources of 

nonnative fish into Grand Canyon
3

Control options for future consideration include stocking daughterless common carp 

(Cyprinun carpio) and the introduction of infectious agents.

Research recommendations proposed by this plandocument and presented in the order of 

their importance are as follows:

1. Development of a bioenergetics, or ecosystem modeling, approach to identify nonnative 

species posing the greatest risk to natives 

2. Identification of sources of juvenile and adult nonnative fish into the mainstem, including 

tributary inflows, dam passage, and stocking, and isotope and larval drift studies to identify 

spawning areas and natal origins of nonnative fish

3. Improvement of monitoring methods through use of a model or an alternative approach to 

track changes in abundance and distribution of nonnative fish

4. Implementation of small-bodied nonnative fish and young-of-year (YOY) capture and 

monitoring studies using slow-shocking techniques in the mainstem 

5. Continued development of remote PIT-tag detection technology for use on nonnative fish 

and in tributary streams

6. Use of large-mesh gill nets to target common carp in the Little Colorado River and its 

confluence with the mainstem Colorado River

7. Development of targeted flow and temperature manipulations to disadvantage nonnative 

fish, including continuing efforts to install and operate a temperature control device on Glen 

Canyon Dam

8. Use of pheromone and sensory attractants to increase nonnative fish captures

9. Implementation of sonic telemetry studies for native and nonnative fish to compare and 

identify spatial and temporal movement patterns, tributary use, and spawning areas

10. Use of experimental stream tests to investigate mechanisms by which nonnative fish 

negatively affect juvenile humpback chub

11. Modification of Williams‘ Carp Cage for application to common carp control in tributary 

streams 

Other activities that could improve the management of nonnative fish include the following 

measures, which are listed in the order of their importance:

1. Conduct an annual nonnative fish workshop with cooperators, managers, and other 

nonnative fish experts

2. Initiate a public outreach effort specifically dealing with nonnative fish management issues 

that emphasizes preventative measures such as deterring illegal stocking 

3. Develop a formalized reporting procedure for nonnative fish captured and observed by 

those professional entities sampling aquatic environments within Grand Canyon

This plandocument suggests evaluating the use of triggers tied to changes in nonnative 

species catch rates, distribution, community composition, and length frequency to initiate control 

efforts. Triggers would be reviewed annually by scientists and managers. 

The recommendations and options presented above attempt to balance the recommendations 

made for monitoring and research needs with the application of control options. However, research 

and monitoring improvement recommendations outnumber control options, a balance that 
4

accurately reflects the current state of knowledge regarding nonnative fish in Grand Canyon. 

Addressing expansion of nonnative fish species currently present or new to the system could be 

limited by the capture methods currently available for most species in Grand Canyon. This 

situation necessitates the use of sampling gears with moderate, poor, or unknown capture 

efficiencies while newer, more sustainable or effective methods are being evaluated. In the interim, 

combining several capture methods and focusing on problem areas with the gears that are most 

likely to capture target species offer the best opportunity to temporarily reduce nonnative species.

This document identifies the need for a contingency fund to support future pressing 

nonnative fish control needs and to avoid impacting ongoing monitoring and research activities. 

The costs of nonnative control efforts will vary depending on many factors, including target 

species, gear required, removal location, specific project goals, and other factors. Currently, based 

on the immigration rates observed from 2003 to 2006 and recent (2009) monitoring data, it is 

estimated that a minimum of two removal trips per year could be required (under a low 

immigration scenario of 50 fish per month) to maintain the population of 600 to 1,200 rainbow 

trout in the Little Colorado River reach (10 to 20 percent of the size of the January 2003 

population). The cost of a single trip is $150,000, meaning that two control trips would cost 

approximately $300,000. This plandocument suggests that the GCDAMP contribute $300,000 

annually to a nonnative fish control contingency fund, accumulating up to a maximum of $900,000 

over 3 years. This fund would be available for controlling any nonnative species in Grand Canyon 

determined to be pose a high risk to humpback chub.

Implementation of the recommendations and options presented by this document and others 

brought forth during future nonnative fish workshops must involve scientists, resource managers, 

tribal members and other stakeholders. Several of the monitoring and research recommendations 

contained within this document will be implemented as part of the GCMRC work plan for fiscal 

years (FY) 2010–11. This document is intended to provide the technical foundation for 

management agencies with statutory authority to initiate the development of a comprehensive 

nonnative fish management plan for Grand Canyon. This document is not intended to obligate 

management agencies to implement any control option presented herein. Management agencies 

working through the AMP will evaluate nonnative fish control implementation based on scientific, 

policy, legal and financial considerations. Implementation of control options presented in this 

document will be carried out in compliance with management agency policies, mandates, and tribal 

consultation requirements. Necessary compliance for the implementation of any nonnative fish 

control activity will be the responsibility of appropriate management agencies.

This document provides examples of project prioritization processes and anticipates 

implementing one of these processes during the 2010 GCDAMP Nonnative Fish Workshop. This 

will assist scientists and managers in prioritizing research, monitoring recommendations and 

control options presented by this document and others brought forth. The need for management 

agencies to define their roles and responsibilities in nonnative fish management, identify and 

address institutional concerns regarding nonnative fish control implementation, and clearly define 

desired future conditions is also presented. This document provides an example of a rapid response 

plan to assist management agencies in identifying issues that impede the ability to move forward 

with the development and implementation of multi-agency rapid responses to newly invading 

nonnative fish species and the development of a comprehensive nonnative fish management plan

for Grand Canyon.
5

Colorado River native fish evolved in extreme environmental conditions. Historically, 

native fish encountered annual water temperatures ranging from near freezing to more than 29°C 

(84°F) (Voichick and Wright, 2007), flows ranging from less than 85 cubic meters per second 

(m3/s) up to 8,500 m

3

/s (3,000 to 300,000 cubic feet per second), and turbidity ranging from clear 

water to flowing mud (Miller, 1961; Topping and others, 2003). Almost all physical and chemical 

conditions of the predam Colorado River fluctuated quickly and radically (Minckley, 1973). 

Colorado River Basin native ichthyofauna evolved under these harsh conditions into a relatively 

depauperate collection of only 36 species. Paleontological and archaeological records indicate only 

eight native fish species commonly occurred in the Colorado River through Grand Canyon, 

including the endangered humpback chub (Gila cypha) (Minckley and others, 1986; Minckley and 

Deacon, 1991). Most of the Grand Canyon native fishes are found nowhere else in the world.

Water development and nonnative species introductions have substantially changed natural 

ecosystem processes and are cited as primary factors contributing to the decline and even extinction 

of native fish (Miller, 1961; Minckley and Deacon, 1991; Lassuy, 1995; Tyus and Saunders, 2000; 

Mueller and Marsh, 2002), although, other factors have also contributed (Webb and others, 2004). 

Nonnative fish were introduced into the Colorado River before and after the completion of Glen 

Canyon Dam in 1963 (Woodbury, 1959; Valdez and Ryel, 1995). Between 1956 and 1996, 24 

nonnative fish species were reported in Grand Canyon, and of these 17 were present before the 

closure of Glen Canyon Dam (Valdez and Ryel, 1995; Wieringa and Morton, 1996). Since 1996, 

researchers have captured approximately 13 nonnative fish species in Grand Canyon (Valdez and 

Ryel, 1995; Rogers and others, 2008; and Ackerman, 2007) (see appendix A for descriptions of 

some nonnative fish species found in Grand Canyon).

Managers and scientists have expressed concern about the impacts of nonnative fish on 

native fish in Grand Canyon. For example, nonnative fish may prey on and compete for food and 

habitat with various life stages of humpback chub as well as cause habitat degradation. The control 

of warmwater nonnative fish in Grand Canyon has become a growing concern because these 

species might benefit from warmer water releases from Glen Canyon Dam resulting from the 

possible construction of a temperature control device or climatic effects (Seager and others, 2007). 

Warmer water temperatures could increase the potential threat to Colorado River native species 

from nonnative fish adapted to warm water (Eaton and Scheller, 1996; Mueller and others, 1999; 

Garrett and others, 2003; Gloss and Coggins, 2005; Chu and others, 2005; Rahel and Olden, 2008; 

Valdez and Speas, 2009). 

In light of growing concern, the U.S. Geological Survey‘s (USGS) Grand Canyon 

Monitoring and Research Center (GCMRC) was directed to develop a process, a schedule, and a 

recommended budget for suppression and control of non-native fish (warm water species) in Grand 

Canyon by the Glen Canyon Dam Adaptive Management Program (GCDAMP), a Federal initiative 

to maintain and protect resources downstream of Glen Canyon Dam. Development of a

comprehensive nonnative fish management plan by appropriate management agencies will take 

time while additional nonnative fish monitoring and control strategies suitable for Grand Canyon
6

are developed. This document is intended to articulate immediate needs and includes strategies for 

improving nonnative fish monitoring, preventing new nonnative fish species invasions, addressing 

information gaps, facilitating communication and rapid response to urgent nonnative fish issues, 

and defining near-term research needs.

Consistent with the strategic approach implemented by Tyus and Saunders (1996) in the 

upper basin of the Colorado River, participants in GCMRC nonnative fish workshops agreed that 

the primary goal of nonnative fish management efforts is to reduce negative impacts of nonnative 

fish on endangered humpback chub, especially juveniles in and around the confluence of the 

Colorado and Little Colorado Rivers. Efforts should be focused on the nonnative species that most 

threaten humpback chub and other natives in areas known to be of importance to native fish. 

Currently, nonnative rainbow trout (Oncorhynchus mykiss) are thought to pose the greatest risk to 

humpback chub (Yard and others, in prep.) and have been the primary, though not sole, target of 

nonnative control efforts to date. A risk assessment is needed to more rigorously test and confirm 

which nonnative fish species most threaten humpback chub and other natives. The GCMRC has 

made progress in this area and will continue to refine the risk assessment as part of its work plan 

for fiscal years (FY) 2010–11.

Clearly, once particular species are determined to pose a risk to humpback chub, greater 

control efforts can be directed at those species. The goal of implementing nonnative fish control is 

to apply an efficient removal technique in a localized area to target the particular species and life 

stages of nonnative fish found to be the greatest detriment to juvenile humpback chub. Other native 

fish currently found in Grand Canyon include speckled dace (Rhinichthys osculus), flannelmouth 

sucker (Catostomus latipinnis), and bluehead sucker (Catostomus discobolus). All native fish 

species are anticipated to benefit from nonnative fish control efforts, which would reduce predators 

and competitors.

This document begins with an overview of recent efforts to protect native fish through the 

control of nonnative fish species in Grand Canyon under the auspices of the GCDAMP. The 

document includes a review of nonnative fish captures in Grand Canyon, a review of ongoing and 

recent fish projects, and a discussion of a nonnative mechanical removal project conducted near the 

confluence of the Colorado and Little Colorado Rivers. Examination of recent and current fish 

sampling efforts reveals the need to improve monitoring of nonnative fish, close information gaps, 

and communicate and respond to urgent needs more rapidly. Based on these conclusions, this 

document presents (1) improvements in nonnative fish monitoring capabilities and methods for 

detecting the presence of new invasive species, (2) nonnative fish control options applicable to 

Grand Canyon, (3) research needs to advance the ability to control nonnative fish, (4) 

improvements in information sharing and communication among fisheries scientists and managers, 

(5) improvement of public outreach on the threats posed by nonnative species, (6) contingency 

planning needs, (7) examples of project prioritization processes, and (8) an example of a rapid 

response plan to assist management agencies in identifying issues that impede the ability to move 

forward with the development and implementation of multi-agency rapid responses to newly 

invading nonnative fish species and the development of a comprehensive nonnative fish 

management plan for Grand Canyon. An estimate of FY2010–11 costs associated with nonnative 

fish monitoring, research, and control activities are also presented 
7

The physical characteristics of the Colorado River in Grand Canyon are influenced by 

operation of Glen Canyon Dam. Growing public concern about dam-related impacts to the aquatic 

environment and other resources prompted Congress to pass and the President to sign into law the 

Grand Canyon Protection Act (GCPA) of 1992, which addresses the effects of dam operations on 

downstream resources in Glen Canyon National Recreation Area and Grand Canyon National Park

(GCNP). In accordance with the Endangered Species Act, the 1996 Record of Decision 

implemented a modified version of the preferred alternative presented in the Operation of Glen 

Canyon Dam Final Environmental Impact Statement that would permit recovery and long-term 

sustainability of downstream resources while allowing flexibility in hydropower production. The 

GCDAMP is a process whereby ―the effects of dam operations on downstream resources would be 

assessed and the results of those assessments would form the basis of future dam operations‖ (U.S. 

Department of the Interior, 1995, p. 34). The GCDAMP includes a Federal Advisory Committee, 

the Adaptive Management Work Group (AMWG), a Technical Work Group (TWG), independent 

scientific review panels, and the GCMRC, which has responsibility for scientific monitoring and 

research efforts for the program.

In 2001, members of the GCDAMP drafted a strategic plan outlining 12 goals and 

associated management objectives intended to guide downstream resource protection. One of those 

goals is to maintain or attain viable population of native fish (GCDAMP Goal 2), and this 

plandocument is a component of this broader goal. The GCDAMP recognized the negative impacts

of nonnative fish on native fish and developed a list of information needs related to nonnative fish 

(Fairley and others, 2005). Further, in 2009, the GCDAMP developed a draft Comprehensive Plan 

for the Management and Conservation of Humpback Chub in the Lower Colorado River Basin

(HBCCP) to provide a broad list of actions designed to better understand and ameliorate threats to

the recovery of the humpback chub. Control and removal of nonnative fish was one of the primary 

actions recommended by the HBCCP. However, the GCDAMP explicitly recognizes the 

importance of maintaining the Lees Ferry rainbow trout fishery (GCDAMP Goal 4), a nonnative 

species, to the extent practicable and consistent with the maintenance of viable populations of 

native fish. As a result, this document seeks not only to protect native species, but also to be 

consistent with the GCDAMP goal of maintaining the Lees Ferry trout fishery.

Core monitoring information needs (CMIN), research information needs (RIN), and effects

information needs (EIN) were developed by the GCDAMP to direct research and monitoring to 

specific resource protection issues. The GCMRC developed a crosswalk table showing how the 

approximately 250 information needs in the GCDAMP Strategic Science Plan related to the 

strategic science questions (SSQs) in the draft Monitoring and Research Plan (Grand Canyon 

Monitoring and Research Center, 2007a). The GCDAMP Science Advisors identified new SSQs 

relating to nonnative fish to be included in the monitoring and research plan. The GCDAMP goals, 

management objectives, strategic science questions, and information needs related to native fish 

conservation and nonnative fish control are presented below. 

Goal 2. Maintain or attain viable populations of existing native fish, remove jeopardy for 

humpback chub and razorback sucker, and prevent adverse modification to their critical 

habitats.
8

MO 2.4 Reduce native fish mortality due to nonnative fish predation/competition as a 

percentage of overall mortality in the Little Colorado River and mainstem to increase native 

fish recruitment.

New SSQ-A. What are the most effective strategies and control methods to limit nonnative 

fish predation on, and competition with, native fishes?

New SSQ-B. What life stage(s) of rainbow trout pose the greatest threat to humpback chub 

and other native fishes? Are the rainbow trout that threaten humpback chub resident fish 

produced in the Little Colorado River reach of the Colorado River, or are these rainbow 

trout immigrants that were spawned in the Lees Ferry reach?

SSQ 1-4. Can long-term decreases in abundance of rainbow trout in Marble and eastern 

Grand Canyons be sustained with a reduced level of effort of mechanical removal or will 

recolonization from tributaries and from downstream and upstream of the removal reach 

require that mechanical removal be an ongoing management action?

SSQ 1-7. Which tributary and mainstem habitats are most important to native fishes and 

how can these habitats best be made useable and maintained?

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?

CMIN 2.4.1 Determine and track the abundance and distribution of nonnative predatory 

fish species in the Colorado River ecosystem and their impacts on native fish.

RIN 2.4.1 What are the most effective strategies and control methods to limit nonnative fish 

predation and competition on native fish? 

RIN 2.4.2 Determine if suppression of nonnative predators and competitors increases native 

fish populations.

RIN 2.4.3 To what degree, which species, and where in the system are exotic fish a 

detriment to the existence of native fish through predation or competition?

RIN 2.4.4 What are the target population levels, body size, and age structure for nonnative 

fish in the Colorado River ecosystem that limit their levels to those commensurate with the 

viability of native fish populations?

RIN 2.4.5 What are the sources (natal stream) of nonnative predators and competitors?

RIN 2.4.6 What are the population dynamics of those nonnative fish that are the major 

predators and competitors of native fish?

EIN 2.4.1 How does the abundance and distribution of nonnative predatory fish species and 

their impacts on native fish species in the Colorado River ecosystem change in response to 

an experiment performed under the Record of Decision, unanticipated event, or other 

management action?
9

The mainstem of the Colorado River below Glen Canyon Dam is divided into fish sampling 

reaches (fig. 1 and table 1; Walters and Korman, 1999). From 2006 to 2008, the upper reaches of 

the river were dominated by coldwater nonnative species such as rainbow trout, and the lower 

reaches were dominated by warmwater species such as fathead minnow (Pimephales promelas), 

red shiner (Cyprinella lutrensis), common carp (Cyprinus carpio), and channel catfish (Ictalurus 

punctatus) (fig. 2). Brown trout (Salmo trutta) were captured in greatest numbers in reach 5 in 

proximity of Bright Angel Creek (Johnstone and Lauretta, 2007; Rogers and others, 2008). Red 

shiners, common carp, channel catfish, and striped bass (Morone saxatilis) were the dominant 

nonnative species in the mainstem below Diamond Creek downstream to the Lake Mead delta area 

(Ackerman, 2007; fig. 2). Other nonnative fish commonly captured in the mainstem of the 

Colorado River include bullhead species (Ameiurus spp.) near the Little Colorado River and plains 

killifish (Fundulus zebrinus) from the Little Colorado River downstream to Diamond Creek. Less 

commonly captured nonnative fish include threadfin shad (Dorosoma petenense), golden shiners 

(Notemigonus crysoleucas), Western mosquitofish (Gambusia affinis), green sunfish (Lepomis 

cyanellus), bluegill sunfish (Lepomis macrochirus), smallmouth bass (Micropterus dolomieu) and 

walleye (Sander vitreus; fig. 2).
10

 
11

 

Lees Ferry -16 - 0

1 0 – 30.9 30-Mile 29.8 – 31.3

2 31.0 – 56.9

3 57.0 – 69.9 Little Colorado River Inflow 57.0 – 65.4

4 70.0 – 79.9 Lava Chuar-Hance 65.7 – 76.3

5 80.0 – 109.9 Bright Angel Creek Inflow

Shinumo Creek Inflow

83.8 – 92.2

108.1 – 108.6

6 110.0 – 129.9 Stephen Aisle

Middle Granite Gorge

114.9 – 120.1

126.1 – 129.0

7 130.0 – 159.9 Havasu Creek Inflow 155.8 – 156.7

8 160.0 – 179.9

9 180.0 – 199.9

10 200.0 – 219.9 Pumpkin Spring 212.5 – 213.2

11 220.0 – 235.9

12 236.0 – 255.9

13 256.0 – 276.5

Native fish captures in Grand Canyon include humpback chub, speckled dace, bluehead 

sucker, and flannelmouth sucker. Aggregations of humpback chub have been found to exist 

throughout the mainstem Colorado River in Grand Canyon (Valdez and Ryel 1995; fig. 1 and table 

1). From 2006 to 2008, native species appeared to dominate the fish community in the mainstem in 

proximity of the Little Colorado River and from below Bright Angel Creek, river mile (RM) 109,

to the last rapid near Bridge Canyon (RM 236). Nonnative species dominate the fish community 

from Glen Canyon Dam to the Little Colorado River (RM 57), in proximity of Bright Angel Creek, 

and in the lower reaches of the Colorado River below Bridge Canyon (RM 236; fig. 2).
12

Fish Species Composition in the Colorado River in Grand Canyon, 2006-2008

0%

20%

40%

60%

80%

100%

BHS 1 43 226 2325 168 71 202 170 419 103 125 9 1 5

FMS 34 26 883 4209 173 173 811 506 1670 628 717 103 14 136

HBC 4 298 2283 40 13 39 14 17 3 5 1

SPD 225 422 734 31 60 236 629 2086 1756 1469 98 2 31

BBH 4 142 1 1 3

BGS 1

BNT 12 3 21 37 10 294 27 9 7 3 2 2

CCF 1 15 1 1 1 3 1 12 16 13 84 32

CRP 27 22 552 15 82 103 62 43 81 42 22 59 65

FHM 3 2988 229 25 417 331 1162 373 550 6 3 2

GSF 1 1 1 2 1 1 1

MOS 217

PKF 137 88 17 112 78 93 39 55 2 1

RBT 6272 1762 2606 1272 76 283 123 243 31 11 9 2

RSH 47 4 1 1 1 104 727

SMB 1 1 1

STB 1 16 43 46 32

WAL 5

Lees 

Ferry

RM 0-

30

RM 31-

56

RM 57-

69

RM 70-

79

RM 80-

109

RM 110-

129

RM 130-

159

RM 160-

179

RM 180-

199

RM 200-

219

RM 220-

236

RM 237-

256

RM 257-

276

 
13

Tributary streams have been identified as sources of native and nonnative fish entering the 

mainstem Colorado River (Stone and others, 2007). For example, relatively few warmwater 

nonnative species are captured in the mainstem upstream of its confluence with the Little Colorado 

River; however, nonnative fish such as young-of-year (YOY) common carp, red shiner, fathead 

minnow, channel catfish, bullhead spp., and plains killifish are captured in proximity to and 

downstream of the confluence of the Colorado and Little Colorado Rivers (Johnstone and Lauretta, 

2007; Rogers and others, 2008). These species are regularly captured in the Little Colorado River 

(VanHaverbeke, 2006). Similarly, brown trout catch rates in the mainstem increase in the proximity 

of Bright Angel Creek (Rogers and others, 2008; Johnstone and Lauretta, 2007). The increases in 

nonnative fish captures in the proximity of these tributaries are likely the result of downstream 

dispersal of fish from tributaries into the mainstem (Leibfried and others, 2003). Alternatively, the 

capture of nonnative fish near tributaries may also be caused by staging of fish near the tributary to 

carry out some aspect of their life history such as spawning. The possibility that adults are staging 

near tributaries to spawn is evidenced by the capture of adult brown trout, which were initially 

tagged in the mainstem, in Bright Angel Creek in spawning condition (Leibfried and others, 2003). 

Humpback chub, fathead minnow, bluehead sucker, and channel catfish spawn in the Little 

Colorado River (Kaeding and Zimmerman, 1983; Maddux and others, 1987). Flannelmouth sucker 

spawn in the Paria River (Weiss, 1993; Thieme and others, 2001; Maddux and others, 1987) and 

rainbow trout in Nankoweap, Clear, Bright Angel, Crystal, Tapeats, Deer, and Shinumo Creeks 

(Maddux and others, 1987). Observation of YOY and spawning adult fish in these Colorado River 

tributaries highlights their potential importance as spawning areas, however, the importance of 

these tributaries for recruitment and persistence of native and nonnative fish in tributaries and the 

mainstem is not known. 

Many of the tributary streams in Grand Canyon, with the exception of Tapeats Creek, 

contain a strong native and diverse nonnative fish community (fig. 3). Tapeats Creek is dominated 

by nonnative trout. Other nonnative fish species sporadically captured in tributaries of the Grand 

Canyon include common carp, red shiner, redside shiner (Richardsonius balteatus), fathead 

minnow, bullhead spp., channel catfish, brook trout (Salvelinus fontinalis), brown trout, rainbow 

trout, cutthroat trout (Oncorhynchus clarki), plains killifish, striped bass, green sunfish, and 

largemouth bass (Micropterus salmoides). The diversity of nonnative fish species captured in 

tributaries highlights the need to manage these potential sources of nonnative fish into the 

mainstem. This finding also suggests that tributaries must be managed to reduce the negative 

impacts of nonnative fish on native fish communities using tributary streams. The effectiveness of 

control techniques may be improved in tributary streams compared to the mainstem because of 

their smaller scale.
14

Fish Species Composition in Select Tributary Confluence Areas 

in Grand Canyon, 1974-2008 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

BHS 66 1475 1151 494 129 5

FMS 8 966 1657 287 2819 11

HBC 14 65 12 90

SPD 1858 1342 3639 4898 2677 7

BNT 35 2 3 88 6

CCF 2 1 13 1

CRP 6 107 2

FHM 9 23 1

GSF 22

GSH 5

PKF 3 107 1

RBT 298 118 84 487 31 867

RSH 3 1

RSS 22

STB 7 2

YBH 1 3

Bright Angel Havasu Kanab Shinumo Paria Tapeats

 
15

In 2002, the AMWG directed the TWG‘s Nonnative Fish Control Ad Hoc Committee to 

develop a plan for nonnative fish control in the Colorado River ecosystem for 2002 to 2006, with 

the expectation of improving conditions for the humpback chub and other native fish. The ad hoc 

committee developed the following eight recommendations (Persons and others, 2003):

Improve public information and education efforts concerning nonnative fish impacts on native 

fish

Evaluate methods to remove brown trout from Bright Angel Creek and consider the removal of 

rainbow trout after public input

Evaluate shocking and removal of rainbow trout near the mouth of the Little Colorado River

Evaluate common carp, channel catfish, and black bullhead removal using nets and other 

appropriate methods in the Little Colorado River

Evaluate managed flows to disadvantage trout and other nonnative fish

Evaluate the feasibility of a temperature control device to improve humpback chub and native 

fish recruitment

Consider sediment augmentation or redistribution to benefit native fish

Implement immediately any feasible control methods to address the urgent need to protect 

humpback chub

The HBCCP, dated February 2009, provides the following additional recommendations 

regarding nonnative fish:

Control nonnative fish in Colorado River tributaries 

Control nonnative fish near the mouth and/or in the Lower 15 km of the Little Colorado River

Develop a nonnative and invasive species control plan for Grand Canyon 

Develop procedures that govern when and where nonnative fish can be stocked in Grand 

Canyon

Since 2003, the majority of the recommendations made by the Nonnative Fish Control Ad 

Hoc Committee and the HBCCP have been implemented to one degree or another with funding 

from the GCDAMP, GCNP, and the Bureau of Reclamation. However, the continued development 

of methods to address nonnative fish species population expansion and to reduce negative effects 

on native fish owing to nonnative species is necessary to fully address the goals of the GCDAMP. 

The following is a list of planning activities and projects related to nonnative fish control 

conducted in Grand Canyon since 2002. Several of these methods are described in greater detail in 

the following section of this plandocument.

Mechanical removal of nonnative fish with emphasis on rainbow trout near the Little Colorado 

River and associated public outreach efforts (See Coggins and others, 2007; Coggins, 2008)
16

Trout removal in Bright Angel Creek and associated public outreach efforts (See Leibfried and 

others, 2003; SWCA Environmental Consultants, 2006; and Sponholtz and VanHaverbeke, 

2007)

Rainbow trout reduction and methods testing in Shinumo Creek associated with translocation of 

humpback chub (Grand Canyon National Park and SWCA Environmental Consultants, unpub. 

data.)

Preliminary common carp, channel catfish, and bullhead reduction methods testing in the Little 

Colorado River (W. Persons, Arizona Game and Fish Department, oral commun., 2007)

Flow management attempting to disadvantage rainbow trout recruitment in the Lees Ferry reach 

(Korman and others, 2005)

Development of an assessment evaluating the benefits of a temperature control device on

spawning, incubation and growth of native and nonnative fish (Valdez and Speas, 2009); the 

temperature control device was also evaluated by two review panels (Mueller and others,1999; 

Garrett and others, 2003)

Investigation of new capture and monitoring methods for channel catfish in the mainstem 

Colorado River (Arizona Game and Fish Department and U.S. Geological Survey, unpub. data, 

2007 and 2008)

Feasibility testing of fish-tracking technology (Arizona Game and Fish Department and U.S. 

Geological Survey, unpub. data, 2007)

Evaluation of the impact of a high flow event on rainbow trout movement in Lees Ferry 

(Hilwig and Makinster, in press)

Development of a nonnative fish control plan for Grand Canyon

Fish sampling methods currently used in the mainstem of the Colorado River in Grand 

Canyon have limitations in their ability to provide robust abundance measures for most warmwater 

nonnative fish. Table 2 summarizes recent fish sampling projects in the mainstem Colorado River. 

Each method is inherently biased for certain species, size classes, and habitat types, so multiple 

gears are used to monitor and sample fish in the mainstem. The following is a brief review of the 

applications and limitations of current fish sampling methods in developing nonnative fish planning 

approaches. A summary of these applications and limitations is given for both mainstem and 

tributary sampling.
17

Mainstem

electrofishing

Arizona Game and 

Fish Department 

(AZGFD)

Twice/yr Shoreline 

electrofishing

About 400 samples 

of about 300 

seconds each

Lees Ferry

monitoring

AZGFD Three 

times/yr; 

spring, 

summer, 

winter

Shoreline 

electrofishing 

Nine fixed sites,

27 random sites, 

300 seconds per 

sample

Lees Ferry 

juvenile trout 

research

Ecometric, Inc. to 

be incorporated 

into AZGFD Lees 

Ferry Monitoring 

in 2010

Nearmonthly 

sampling

(sampling 

reduced in 

2010)

Boat 

electrofishing, 

slow shocking, 

backpack 

shocking, 30 to 

50 m sites

Evaluation of 

experimental flows 

on rainbow trout 

production and 

survivorship

Mechanical 

removal

AZGFD Periodic; up 

to six 

times/yr

Boat 

electrofishing, 

hoop nets

Serial depletion 

electrofishing 

samples to remove 

trout in proximity of 

the Little Colorado 

River, hoop net 

samples to monitor 

native fish response

Nearshore 

ecology 

research

University of 

Florida

Four 

times/year, 

July–Oct.

Slow shocking, 

hoop nets, 

seines, minnow 

traps

Assessment of 

juvenile humpback 

chub shoreline 

habitat use 

associated with 

summer and fall 

flow fluctuations
18

BHS Bluehead sucker Catostomus discobolus

FMS Flannelmouth sucker Catostomus latipinnis

HBC Humpback chub Gila cypha

SPD Speckled dace Rhinichthys osculus

BBH Black bullhead Ameiurus melas

BGS Bluegill sunfish Lepomis macrochirus

BNT Brown trout Salmo trutta

CCF Channel catfish Ictalurus punctatus

CRP Common carp Cyprinus carpio

FHM Fathead minnow Pimephales promelas

GSF Green sunfish Lepomis cyanellus

GSH Golden shiner Notemigonus crysoleucas

MOS Western mosquitofish Gambusia affinis

PKF Plains killifish Fundulus zebrinus

RBT Rainbow trout Oncorhynchus mykiss

RSH Red shiner Cyprinella lutrensis

RSS Redside shiner Richardsonius balteatus

SMB Smallmouth bass Micropterus dolomieui

STB Striped bass Morone saxatilis

WAL Walleye Sander vitreus

YBH Yellow bullhead Ameiurus natalis

Two parameters can be used to evaluate the effectiveness of nonnative fish monitoring 

efforts and gears as removal methodologies: the coefficient of variation (CV) and the capture 

probability. The CV is used to measure the ability of monitoring protocols in Grand Canyon to 

detect change in relative abundance over time. A CV value of 0.10 indicates a 90 percent chance of 

detecting a 13 percent change in relative abundance per 1-year time step and a 53 percent change 

during 5 years based on a two-tailed significance test with a linear relationship (Gerrodette, 1987). 

A CV value greater than 0.10 indicates a reduced power to detect change in catch rates over time. 

Analysis of CV is specific to species and gear type and can assist in evaluating the level of 

uncertainty in monitoring data. Capture probability is an estimate of the proportion of a population 

captured for a particular species, gear, and method. In the context of this document, capture 

probability provides a measure of the potential effectiveness of a particular sampling gear in 

capturing a particular species of fish. 

The Arizona Game and Fish Department in cooperation with the GCMRC conducts

mainstem monitoring twice a year using boat-mounted electrofishing. A variable length of 

shoreline is shocked for 300 seconds with approximately 15 amperes and 350 volts with two people 

netting fish (This mainstem electrofishing monitoring protocol is different from the slow shocking 
19

technique described for Lees Ferry monitoring.). Electrofishing conducted in the mainstem from 

below Lees Ferry to Diamond Creek from 2000 to 2003 was sampled with the intensity believed to 

be necessary for long-term monitoring (800 samples) to detect changes in catch rates of rainbow 

trout, brown trout, common carp, and some natives in Grand Canyon (5 year time series; Rogers 

and Makinster, 2006). Coefficients of variation (800 samples) for rainbow trout, brown trout, and 

possibly common carp from 2000 to 2003 data were 0.09, 0.10, and 0.09, respectively. Detectable 

increases in catch-per-unit effort (CPUE) over 5 years based on 80 percent confidence intervals 

were estimated to be 23 percent for common carp and 23 percent for rainbow trout. Estimated 

detectable decreases in CPUE were 19 percent for common carp, 19 percent for rainbow trout, and 

21 percent for brown trout (Rogers and Makinster, 2006). However, the increased sampling that 

took place in reach 5 (Bright Angel Creek inflow reach; 197 samples) and reach 3 (Little Colorado 

River reach; 147 samples) in 2002 and 2003 highlight the effort necessary to detect localized 

annual trends (Rogers and Makinster, 2006). The current mainstem electrofishing monitoring 

protocol can detect large changes ( 21 percent) over a 5-year time scale or larger changes in catch 

rates (that is, 100 percent change) over an annual time scale. Electrofishing conducted during 

mainstem monitoring may also be adequate in detecting the presence of strong cohorts of juvenile 

salmonids (Rogers and others, 2003; Makinster and others, 2008; Makinster and others, 2009).

Electrofishing conducted as part of the long-term fish monitoring program is effective at 

monitoring trends in rainbow trout, brown trout, and potentially common carp, as well as some 

natives (Makinster and others, 2009). Other nonnative fish species such as channel catfish, 

bullheads, striped bass, and small-bodied fish are not effectively monitored using this protocol (for 

example, other species are not readily captured by this gear and so only very large changes in the 

abundance of these species will be detected over periods of one or a few years). Development of 

consistent monitoring protocols to assess the expansion in abundance or distribution of these 

nonnative fish species is necessary to determine threats, evaluate triggers for implementation of 

control programs, and provide a baseline to measure the effectiveness of control efforts once they 

are implemented.

Based on monitoring data, electrofishing can also be evaluated for use as a potential 

reduction method. Repeated sampling using methods with relatively high capture probabilities 

(approaching 15 to 20 percent) for a particular species are preferred for nonnative fish removal 

programs because they are more efficient in reducing target species in Grand Canyon (Coggins, 

2008). Estimated electrofishing capture probabilities, using the method discussed above in the 

mainstem, for rainbow trout and brown trout are 15 and 9 percent, respectively (Rogers and 

Makinster, 2006). Thus, one electrofishing sample could remove an estimated 15 percent of the 

rainbow trout and 9 percent of the brown trout population within the sample location. 

Electrofishing appears to be a viable reduction method for rainbow trout, at least over limited 

reaches for short time periods (Coggins, 2008), where removal of this species is desirable; 

however, the effectiveness of using electrofishing for reducing brown trout is less when compared 

to rainbow trout. Capture probability for common carp has not been determined for electrofishing 

but is assumed to be very low, thus, electrofishing is likely not a feasible technique to reduce 

common carp populations in Grand Canyon (R. Rogers, Arizona Game and Fish Department, pers. 

commun., 2008). The use of electrofishing should be carefully considered because it is only 

effective for certain species in specific conditions. 

Mainstem electrofishing has limitations in population monitoring and reduction applications 

for most nonnative fish. Capture probabilities using electrofishing for smallmouth bass and 

walleye, which likely occur in very low densities in the Colorado River, are not known in the 

mainstem and Lees Ferry. The mainstem electrofishing monitoring protocol is not effective for 

monitoring or population reduction efforts for channel catfish, bullhead species, and small-bodied 
20

or young fish; this method results in very few captures of these species in locations where they are 

captured in greater numbers with other gears (Ackerman, 2007; Rogers and Makinster, 2006). 

The Arizona Game and Fish Department, in cooperation with the GCMRC, conducts annual 

Lees Ferry monitoring using electrofishing. This effort targets rainbow trout using an electrofishing 

technique similar to the one used in the mainstem below Lees Ferry. This technique has also 

captured other species such as adult smallmouth bass and walleye (Makinster and others, 2007). 

Current mainstem and Lees Ferry electrofishing programs may be adequate for detecting the 

presence of adult smallmouth bass and walleye, however, the efficiency of electrofishing in 

capturing and removing these species, which occur in low densities, is not known. 

Ecometric, Inc., in cooperation with the GCMRC, has sampled Lees Ferry using the ―slow 

shocking‖ technique described by Korman and others (2006) that targets young rainbow trout as 

small as 30 mm. This sampling technique uses backpack shockers in short river sections in a 

variety of shallow habitats and shocking that is conducted with a boat electrofishing unit to sample 

areas where it is infeasible to sample with a backpack shocker. A 50 m length of shoreline is 

shocked for 500 seconds with 16–18 amperes and 200 volts. This method has captured several 

small nonnative fish on rare occasions in the Lees Ferry reach that may have otherwise been 

undetected, including YOY channel catfish, smallmouth bass, and green sunfish (Korman, unpub. 

data, 2007). This method will be incorporated into the Lees Ferry monitoring program in 2010.

Lees Ferry is an area where new nonnative species introductions are most likely to occur. 

Nonnative introductions result from unintentional or illegal stocking, movement of nonnative fish 

from Lake Powell through Glen Canyon Dam, dispersion from the large warm slough located near 

RM 12, and from the Paria River drainage into the mainstem. The introduction of new fish species 

into Lees Ferry is a concern because nonnative species that are introduced or become established in 

this reach can then disperse throughout the entire river system below Glen Canyon Dam. Although 

standard Lees Ferry monitoring protocols may be adequate for detecting adult smallmouth bass and 

walleye, there is not a rigorous monitoring protocol in place to detect invading nonnative fish in 

Lees Ferry or Grand Canyon.

At the direction of the GCDAMP, a nonnative fish control program was implemented near 

the confluence of the Colorado and Little Colorado Rivers in January 2003 as part of a joint 

Federal action. The objective of mechanical removal is to reduce the number of all nonnative 

predatory and competitive fish in habitat occupied by native fish. This action was initiated on an 

experimental basis because it was thought possible that rainbow trout could be effectively captured 

with available electrofishing techniques and presented low risk relative to other actions intended to 

benefit native fish such as a selective withdrawal structure or modifications to flow regimes. The 

Arizona Game and Fish Department, in cooperation with the GCMRC, conducted mainstem 

mechanical removal in proximity of the Little Colorado River from 2003 to 2006 and in 2009 to 

reduce the abundance of rainbow trout primarily. From 2003 to 2006, six trips of four passes each 

were conducted each year, except in 2006 when only five trips were conducted. One trip was 

conducted in 2009.

YOY and juvenile native fish, including humpback chub, enter the mainstem Colorado 

River primarily from the Little Colorado River during freshet events (Valdez and Ryel, 1995). It is 

generally agreed that these young fish encounter a number of challenges affecting their survival, 

including suboptimal water temperatures, predatory and competitive nonnative fish (Yard and 
21

others, in prep.), and unstable shoreline habitat (Petersen and Paukert, 2005; Stone and Gorman, 

2006; Paukert and Petersen, 2007). The primary removal reach (Little Colorado River removal 

reach) spanned river miles 56.2 to 65.7 of the Colorado River, which included the confluence with 

the Little Colorado River. In August 2003, an additional removal reach, Lava Chuar to Tanner, 

river miles 65.7 to 68.5, was also added. Nonnative fish were removed during 23 trips from January 

2003 to August 2006. Nonnative fish were removed using electrofishing during 2 to 6 serial 

depletion passes (typically 4) within both removal reaches. These data were subsequently used to 

infer species composition and abundance trends within the removal reaches (Coggins and others, 

2007; Coggins, 2008). 

Results of mechanical removal suggest that serial depletion using electrofishing is an 

effective capture method for rainbow trout. Observed capture probabilities for rainbow trout ranged 

between 2 percent and 35 percent per pass, depending on location and time of year, but generally 

were 10 percent. Over the course of the experiment, rainbow trout abundance gradually reduced 

to approximately 10 percent of the January 2003 estimate, however, this reduction may have also 

been a result of other confounding factors discussed below. Additionally, overall community 

composition (by mass), as indexed by fish captured, was reduced from 90 percent nonnative fish 

to 40 percent (Coggins and others, 2007; Coggins, 2008). The impact of mechanical removal on 

other nonnative fish species such as common carp, fathead minnow, channel catfish, and bullheads

is not clear.

It is possible that nonnative fish abundance, particularly of rainbow trout, was also reduced 

by factors other than mechanical removal. From 2003 to 2006, and particularly in 2005, water 

temperatures in the mainstem Colorado River were elevated by as much as 6 C relative to much of 

the postdam period (fig. 4). These temperatures possibly inhibited growth and survival of rainbow 

trout (Paukert and Petersen, 2007). Additionally, a downward trend in rainbow trout abundance 

was observed in both Lees Ferry and Marble Canyon beginning as early as 2002 (fig. 5). Finally, 

the immigration rate into the removal reaches generally decreased throughout the experiment, 

suggesting that the upstream source of rainbow trout may have declined in abundance. 

In 2009, mechanical removal was reinitiated following a protocol similar to the one 

described above. Results from this removal effort should assist scientists in further evaluating the 

effectiveness of the effort. As results become available, this information should be incorporated 

into nonnative fish control planning approaches. As requested by the GCDAMP, the GCMRC has 

included this project in the work plans for FY 2010 and 2011.
22
23

In 2009, University of Florida, Ecometric, and the State University of New York, in 

cooperation with GCMRC, initiated a 4-year research project to quantify abundance, survival, 

habitat use, growth, and natal source of juvenile humpback chub over three flow periods: (1) 

summer modified low fluctuating flows, (2) modified low fluctuating flow transition to fall steady 

Lees Ferry Rainbow Trout Catch Rate

Year

CPUE (Fish/Hour) 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

0 100 200 300 400

Marble Canyon Rainbow Trout Catch Rate

Year

CPUE (Fish/Hour) 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

0 50 100 150 200
24

experimental flows, and (3) fall steady experimental flows. Sampling trips were conducted in July, 

August, September, and October of 2009. This study will continue through 2011, and laboratory 

work and analysis will conclude in 2012. This effort employs the slow shocking technique in 

discrete mainstem habitat types around the confluence of the Little Colorado River to help 

understand the relative importance of these habitats and the impact various flow regimes have on 

their use by fish. This technique will allow for direct comparisons of backwater habitats with other 

nearshore areas such as talus slopes and cliff walls because the same sampling method will be used 

for all habitats. The nearshore ecology study targets humpback chub; however, based on the 2008 

pilot studies conducted by the GCMRC, information on fathead minnow abundance and habitat use 

in the study area may be periodically obtained (M. Yard, U.S. Geological Survey, oral commun., 

2009). This project may provide insight on (1) habitat overlap and potential competition juvenile 

humpback chub may incur from fathead minnows, (2) development of effective systemwide 

nonnative fish monitoring protocols, and (3) natal source studies that support the development of 

nonnative fish control methods. As results become available this information should be 

incorporated into nonnative fish planning approaches.

There are currently no fish monitoring programs in place for Colorado River tributaries in 

Grand Canyon, with the exception of the Little Colorado River. Nonnative fish have been captured 

in the majority of tributary streams in Grand Canyon, representing a potential source of nonnative 

fish into the Colorado River. Sampling in tributaries beyond the immediate Little Colorado River 

confluence area has been sporadic and conducted by multiple organizations with multiple gears and 

sampling protocols. Unlike mainstem fish collection data, data associated with these sampling 

events are not maintained in a centralized database. In the mid 1980s, Maddux and others (1987) 

sampled extensively in several tributary confluence areas, and in the early 1990s, graduate students 

from the University of Arizona sampled in select tributaries of the Grand Canyon (Allen, 1993; 

Weiss, 1993). Following the mid 1990s, nonnative fish sampling in Grand Canyon tributaries did 

not occur until 2004 and 2005 (National Park Service, unpub. data). No other extensive sampling in 

tributary streams has occurred since 2005, with the exception of sampling conducted in Shinumo 

Creek to prepare for the translocation of humpback chub in 2009 (National Park Service, unpub. 

data).

The U.S. Fish and Wildlife Service and the Arizona Game and Fish Department, in 

cooperation with the GCMRC, conduct annual fisheries monitoring in the Little Colorado River 

from river kilometer (rkm) 13.6 downstream to the confluence with the Colorado River. Table 3 

provides a summary of current monitoring activities in the Little Colorado River. The Little 

Colorado River is sampled with hoop nets primarily in the spring and fall. In addition, two 

monitoring trips are conducted above Chute Falls (rkm 18.1) periodically in the summer to evaluate 

humpback chub translocated above Chute Falls. 

Monitoring in the Little Colorado River targets humpback chub but also results in the 

capture of nonnative species, though, they represented only 6 percent of the fish captured in hoop 

nets in the lower reaches of the river in 2008 (Stone, 2008). Monitoring trends in nonnative fish 

abundance using relative abundance measures is problematic because of the small numbers of 

nonnatives captured. However, YOY and juvenile channel catfish and bullhead species captures in 

the hoopnet samples were higher in 2008 than in previous years, indicating a successful recruitment 

year for these species in the Little Colorado River (Stone, 2008). Adult channel catfish and 
25

common carp were captured using angling in close proximity to hoop net sets in the lower most 

reach of the Little Colorado River (W. Persons, Arizona Game and Fish Department, oral 

commun., 2007), however, adult fish are rarely captured in hoop nets (Clark, 2008). Because of the 

low number of captures of nonnative fish in hoopnets in the Little Colorado River, reliable capture 

probability estimates are not available.

Currently, there is not a protocol to monitor changes in nonnative fish abundance in the 

Little Colorado River. Hoop nets capture YOY and juvenile channel catfish and common carp, 

indicating their effectiveness in at least detecting this age group; however, the effectiveness of this 

technique in reducing nonnative fish abundance is not known. Angling, effective in capturing adult 

channel catfish and common carp, also captures humpback chub and poses a mortality risk. Hoop 

netting and angling data for nonnative fish captures may be applied to the development of an 

occupancy model (see Occupancy Modeling section below) to better understand changes in 

nonnative fish abundance and distribution.
26

Lower 1,200 m 

of Little 

Colorado River 

monitoring

Arizona Game 

and Fish 

Department

Once/yr for 30-

days in spring

1-m-diam, 5.0-

m-length, 6.3-

mm-mesh 

unbaited hoop 

nets with seven 

hoops and two 

throats

13 nets fished in 

standardized 

locations in the 

lower 1,200-m 

reach

Little Colorado 

River 

monitoring

U.S. Fish and 

Wildlife Service

Four times/yr for 

10 days; 

twice in spring,

twice in fall

0.6-m-diam, 1.0-

m length, 6-mmmesh unbaited 

hoop nets with 

three hoops and 

a single throat

About 540 hoop 

net nights, 

samples from 

rkm 13.57 to 

confluence

Chute Falls 

monitoring

U.S. Fish and 

Wildlife Service

Twice/yr for 5 

days; summer

0.6-m-diam, 1.0-

m-length, 6-mmmesh baited 

hoop nets with a 

single 0.1-m 

throat

About 150 hoop 

net nights, 

samples from 

18.1 rkm to 

13.57

By assessing the predicted suitability of various temperature scenarios for spawning, 

incubation, and growth of fish in Grand Canyon, Valdez and Speas (2009) evaluated the potential 

impact of a selective withdrawal structure. This assessment considered the temperature suitability 

of four regions of the Colorado River in Grand Canyon for fish using predicted temperatures from

the Bureau of Reclamation‘s GEMSS® model. Three temperature scenarios evaluated were (1) no 

action, which provided maximum predicted release temperature of approximately 16oC in 

November; (2) two units, which provided maximum predicted release temperature of 21oC in June; 

and (3) four units, which provided maximum predicted release temperature of 24oC in late July. 

Benefit is depicted as an increase in the number of river regions exhibiting suitable temperatures 

for a particular species to spawn, incubate, and grow based on an extensive review of such 

parameters by Valdez (2008). The results indicate that native fish gain the greatest benefit from a 

four unit structure in all river regions, however, seven of ten warmwater and four out of five 

coldwater nonnative species investigated also benefit from the warmer temperatures (See figs. 11 

and C-1 in Valdez and Speas, 2009). Native fish would benefit from a two unit structure in many

fewer regions of the river than with four units. Temperatures were predicted to be suitable for 

seven out of ten warmwater and five out of five coldwater nonnative fish with the two-unit 

scenario. When considering warmwater species alone, Valdez and Speas (2009) predict that 

warming mainstem temperatures could increase the temperature suitability of the mainstem for 

spawning, incubation, and growth of warmwater nonnative species. 
27

The work of Valdez and Speas (2009) could be misinterpreted as predicting distributional 

changes of fish species in the mainstem. For example, this analysis predicts that under the no action 

scenario (similar to 2005 temperatures), no region of the river has suitable temperatures for 

spawning or growth of channel catfish (See fig. 11 in Valdez and Speas, 2009), which could be 

interpreted as depicting predicted channel catfish distribution in the Grand Canyon. However, 

channel catfish currently occur in proximity to the Little Colorado River and below Lava Falls. 

This example emphasizes that Valdez and Speas (2009) predict the impact of temperature control 

on the temperature suitability for various species to spawn, incubate, and grow rather than 

predicting species distribution. The predictions made by Valdez and Speas (2009) regarding the 

impact of warmer water releases on warmwater species are very conservative because only 

mainstem effects are considered. The authors emphasize this concept by stating that warming

mainstem temperatures could allow for greater dispersal of species that are restricted to warmer 

tributary streams and other habitats by surrounding cold mainstem temperatures (Valdez and Speas, 

2009).

The GCMRC attempted to interpret the no action scenario in the Valdez and Speas (2009) 

assessment to evaluate risk of nonnative species in Grand Canyon. The no action alternative was 

not specifically parameterized to emulate water temperature conditions in 2005, however, this 

scenario best approximates mainstem conditions that are most likely to occur in the near future. 

The following excerpt from Valdez and Speas (2009) summarized model results of the suitability 

of mainstem temperatures to spawning, incubation, and growth of nonnative species under the no 

action scenario:

―... under No Action, the mainstem Colorado River through Grand Canyon was suitable 

only for rainbow trout and brown trout from the dam to the LCR. Downstream of the LCR, 

predicted temperatures remained cool and were suitable for rainbow trout, brown trout, 

walleye, redside shiner, and smallmouth bass.‖

From this one can infer that there is risk of these nonnative fish species encountering suitable 

conditions for spawning, incubation, growth, and persistence in the mainstem Colorado River 

through Grand Canyon. The risks for nonnative fish persistence in temperature conditions likely to 

occur in the near future are as follows: (1) brown and rainbow trout could persist throughout the 

river and (2) smallmouth bass, walleye, and redside shiner could persist downstream of the Little 

Colorado River to Lake Mead. To specifically evaluate the risks each of these species and others 

pose to juvenile humpback chub, information such as diet composition and habitat overlap should 

be incorporated into an ecosystem or bioenergetics model.

The GCMRC is in the initial phases of developing an ecosystem model to evaluate factors 

that may negatively impact juvenile humpback chub in Grand Canyon. Recruitment failure has 

been identified as a limiting factor in maintaining adult humpback chub populations in Grand 

Canyon. Scientists have identified juvenile humpback chub recruitment in proximity of the Little 

Colorado River as the primary response variable in the model construction. Factors included in 

modeling efforts affecting humpback chub recruitment include food limitation, predation or 

competition, and temperature effects. Once models are constructed that reasonably emulate past 

conditions and fish population responses in Grand Canyon, simulations using other variables such 

as nonnative fish invasions or temperature variation will be evaluated. GCMRC scientists have 

been constructing datasets and identifying information needs for the development of these models.
28

In the past, SWCA Environmental Consultants, in cooperation with the GCMRC, conducted 

the mainstem Colorado River netting program designed to monitor native fish in Grand Canyon. 

Nonnative fish were captured sporadically using hoop and trammel nets. In 2006, the number of 

individual nonnative species captured in 1,044 hoop net samples and 293 trammel net samples 

combined was 40 common carp, 1 red shiner, 164 fathead minnows, 5 bullhead species, and 6 

brown trout (Ackerman, 2007). Despite large fathead minnow captures relative to other species 

captured in hoop nets, the overall CV for this method and species approaches 0.70 (Johnstone and 

Lauretta, 2007). Capture probabilities for these gears have not been determined because of sporadic 

and sparse captures of nonnative fish. Hoop nets have provided valuable catch data for juvenile 

humpback chub but do not seem to be effective at monitoring or reducing populations of other 

species, although, other species may be rare in the reaches sampled. Because anecdotal 

observations suggested that trammel nets may cause unacceptable stress to native fish, especially 

humpback chub, the GCMRC suspended use of this gear in 2007 and supported a laboratory study 

of the impact of the gear on fish. Hunt (2008) found that in controlled settings fish captured in 

trammel nets had elevated levels of cortisol, especially at warmer water temperatures, suggesting 

that these fish had elevated stress levels compared to those not captured. This effect was less 

measureable at colder temperatures. Fish in these experiments experienced widespread mortality, 

but those fish subjected to warmest water expired most quickly. Because trammel nets have been 

effective for monitoring humpback chub in previous studies (for example, Valdez and Ryel, 2005), 

the 2009 Protocol Evaluation Panel for Grand Canyon Fishes recommended reinitiating use of this 

gear when water temperatures are less than 20°C. Hoop nets are periodically used to sample 

humpback chub aggregations, although, this technique has no demonstrated value in monitoring 

nonnative fish. These methods will be included in mainstem monitoring trips scheduled for 2010 

and 2011.

In the past, SWCA Environmental Consultants and the U.S. Fish and Wildlife Service, in 

cooperation with GCMRC, conducted annual mainstem backwater seining sampling. The use of 

seines to monitor small-bodied and YOY nonnative fish is limited to backwaters, which represent 

only a very small portion of nearshore fish habitats found in the Colorado River, particularly in 

Grand Canyon (M. Breedlove, Utah State University, oral commun., 2007). Seining allows 

scientists to detect the presence of various species in backwaters; however, it is not possible to 

determine the relative importance of backwater habitats to small-bodied fish because only very 

limited assessments of their use of habitats other than backwaters has been attempted in Grand 

Canyon (Converse and others, 1998). The availability of backwater habitats also changes over time 

because of the transitory nature of sandbars that control some of these habitats and because 

different flows through Glen Canyon Dam alter the river stage, often over the course of one day, 

changing the inundation of backwaters. 

Generally, when seining backwaters one seining pass is made through the backwater and 

captures of fish are recorded per area seined. Serial depletion samples have recently been added to 

the seining protocol to better track abundance and capture probability (Ackerman, 2007). Protocols 

have varied over the duration of the project. Nonnative species captured during seining include 

common carp, red shiner, fathead minnow, rainbow trout, plains killifish, and green sunfish. 

Seining CV for fathead minnow in backwater habitats is 0.14 and exceeds 0.25 for all other 

nonnative species (Ackerman, 2007). Capture probabilities using serial depletion seining samples 

in backwaters for fathead minnow ranged from approximately 65 to 90 percent and from 45 to 100 
29

percent for plains killifish. Factors such as application of varying protocols over time, differences 

in backwater size, proportion of backwater area seined, and unequal capture probabilities among 

seine hauls and years confounds interpretation of trends in catch rate (U.S. Geological Survey, 

unpub. data, 2007).

Though capture probabilities of depletion seining samples for some nonnative fish is very 

high, the effect of a removal program using seines to target backwaters is not clear. The 

effectiveness of seining is unknown because of several factors, including (1) the relative 

importance of backwaters to native and nonnative fish is unknown; (2) the method will result in 

only the removal of individual nonnative fish occupying backwaters, which represent only a small 

fraction of habitat in Grand Canyon; (3) monitoring the effect of removal will be problematic 

because of unknown immigration, emigration, recruitment, and survivorship rates of fish in both 

backwaters and other nearshore habitats. Seining may be better applied to detecting newly invading 

nonnative fish and tracking changes in nonnative fish species distribution (see Occupancy 

Modeling section below).

Channel catfish, which are present in Grand Canyon, prey on native fish, and are adapted to 

warmer waters (such as have been released from Glen Canyon Dam in recent years), are generally 

agreed to be one of the nonnative fish species posing risk to native fish in Grand Canyon. Capture 

of channel catfish, especially in large rivers, is challenging because of the habits and habitat 

preferences of this species (Ryden and others, 2005; Davis and Furr, 2008). Arizona Game and 

Fish Department, in cooperation with the GCMRC, launched a pilot project to investigate channel 

catfish capture methods below Diamond Creek in June 2007 and July 2008 (Arizona Game and 

Fish Department and U.S. Geological Survey, unpub. data, 2007 and 2008). Gears tested included 

angling, electrofishing, and baited hoop nets. Although capture probabilities for these methods 

have not been determined, preliminary results suggest that a combination of a different hoop net 

(―catfish net‖) and bait type (stink cheese) may result in greater numbers of channel catfish 

captures when compared to the standard hoop nets used for mainstem monitoring. Standard hoop 

nets baited with Aquamax pellets (216 samples) set below Diamond Creek in May 2006 captured 

two channel catfish; however, approximately 320 channel catfish were captured in catfish nets 

baited with stink cheese. Captures ranged from 0 to 25 channel catfish in one net (180 samples). 

Deploying catfish nets for 2 d without disturbing them also appeared to enhance channel catfish 

captures. Angling may be an adequate method for assessing trend information and is being 

implemented as part of the mainstem monitoring protocol for comparison with other methods. 

Electrofishing was not effective in capturing channel catfish in the Grand Canyon (Arizona Game 

and Fish Department and U.S. Geological Survey, unpub. data, 2007 and 2008).

In 2008, the pilot study focused on attempting to assess the capture probability of channel 

catfish hoopnets and stink cheese below Diamond Creek. Unfortunately, channel catfish captures 

were 75 percent less than those encountered the previous year, making estimation of a capture 

probability infeasible (R. Rogers, Arizona Game and Fish Department, pers. commun., 2008). 

Estimation of a capture probability for this method is important for determining the applicability of 

this method for targeted removal efforts and population monitoring of channel catfish. As results 

become available, this information should be incorporated into nonnative fish planning approaches.

Telemetry techniques have been applied in Grand Canyon to track fish movement with 

varying results. Radio tags were implanted in adult humpback chub in the proximity of the Little 
30

Colorado River, but once the tagged fish reached a depth greater than approximately 4.5 m (Valdez 

and Ryel, 1995), they could no longer be detected. Sonic tags have recently been tested in Grand 

Canyon and the results appear promising (Hilwig and Makinster, in press). Up to 85 percent of 

sonic tagged fish were detected by manual tracking. Locations of sonic tagged fish can be 

determined within a few meters using manual tracking, allowing the ability to assign generalized 

habitat characteristics to the sample point. Large-scale movement can also be observed using tag 

location information. Recent sonic telemetry studies in Grand Canyon used sonic tags to assess the 

capture probability of channel catfish hoopnets baited with stink cheese, to determine the impact of 

the 2008 high-flow experiment on rainbow trout movement in Lees Ferry, to investigate habitat use 

by flannelmouth sucker, and to assess the feasibility of a broad-scale sonic tagging project in the 

mainstem Colorado River. Sonic technology has been greatly improved and customized for Grand 

Canyon conditions as a result of these projects.

This technique can be used, with some limitation, to track and compare movement patterns 

and habitat associations of nonnative and native adult and juvenile fish larger than 160 mm (See 

Remote PIT Tag Detectors section for smaller fish movement). Determining movement patterns 

and habitat associations will help to identify areas important for spawning, determine spatial and 

temporal overlap of native and nonnative fish, and assist scientists in evaluating the nature of the 

negative impacts nonnative fish impose on native fish. This information will assist in the 

development of nonnative control prescriptions to benefit and minimize impacts on native fish.

Many of the fish in Grand Canyon are tagged with a passive integrated transponder (PIT) 

tag when they are captured during various sampling projects. These tags can be detected using a 

remote PIT-tag detector positioned on the riverbank, which logs tagged fish as they swim by and 

are detected by a submerged antenna. Arizona Game and Fish Department, in cooperation with the 

GCMRC, constructed three single-antenna remote PIT tag detectors. In 2008, two of the three 

antennas ran continuously from summer to early fall, with the exception of periodic technical 

issues. These remote PIT tag detectors recorded a total of 1,913 PIT-tags, 840 of which were

unique fish.

In 2009, USGS Columbia River Research Lab joined the project and assisted in the 

installation of a multiplexing remote PIT-tag detector with multiple antennas (MUX) that span a 

large portion of the width of the Little Colorado River. This design can allow for an estimation of 

tag detection probability vital to evaluate the efficiency of the MUX as well as humpback chub 

monitoring effectiveness. 

Currently, the installation and operation of this device is experimental and primarily 

focused on learning about humpback chub movement patterns in the Little Colorado River. 

However, this method has many applications to nonnative fish. Remote detection of PIT-tagged 

fish can assist scientists in comparing movement patterns of fish using the Little Colorado River. 

From this information, the timing and location of nonnative fish removal programs could be 

pinpointed to target nonnative fish vulnerabilities. As results become available, this information 

should be incorporated into nonnative fish planning approaches.

In 2002, Grand Canyon National Park initiated a trout removal project in Bright Angel 

Creek. Over the duration of this project, cooperators included SWCA Environmental Consultants 

and the U.S. Fish and Wildlife Service. This effort included the use of a weir near the mouth of the 

creek and serial depletion samples using backpack electrofishing units in proximity to the weir and 
31

around the confluence of Bright Angel Creek and Roaring Springs. This project was initiated 

because of increased captures of adult brown trout in the mainstem in the proximity of the Bright 

Angel Creek confluence relative to other areas of the mainstem (Leibfried and others, 2003; 

Leibfried and others, 2005) and concern for the impact brown trout may exert on native fish in the 

area. The high number of brown trout captured in the mainstem adjacent to the Bright Angel Creek 

confluence suggests that this tributary is important for brown trout spawning or is otherwise 

important for brown trout in the Grand Canyon (Leibfried and others, 2003; Leibfried and others, 

2005).

During operation of the weir, brown trout captures declined significantly between 2003 and 

2007. From November 2002 to January 2003, 423 brown trout and 188 rainbow trout were 

captured in the weir (Leibfried and others, 2003; Leibfried and others, 2005). From November 

2006 to January 2007, a decline was observed, with 54 brown trout and 36 rainbow trout captured. 

However, this is consistent with a notable decline of rainbow trout (fig. 5) and brown trout catch 

rates in the mainstem (Ackerman, 2007; Rogers and others, 2008). Disentangling which factor or 

factors mainstem mechanical removal of trout, removal of brown trout in Bright Angel Creek, or 

warm mainstem water temperatures—are the ultimate causes of trout reduction is not possible 

without additional information (Coggins, 2008). However, the weir proved to be effective in 

capturing the majority of brown and rainbow trout moving into Bright Angel Creek from the 

mainstem, including adult trout in spawning condition (Leibfried and others, 2003; Leibfried and 

others, 2005; Sponholtz and VanHaverbeke, 2007). 

As part of this project, Bright Angel Creek was surveyed in two locations: (1) from the weir 

to Phantom Creek (3.0 km) and (2) in a 1.7-km reach in the headwater area of the creek near 

Roaring Springs. The fish captured in the lower reaches of Bright Angel Creek include native 

speckled dace, native bluehead sucker, and nonnative brown and rainbow trout (Sponholtz and 

VanHaverbeke, 2007). In the upper reaches, fish captures consisted entirely of brown and rainbow 

trout, including possible rainbow-cutthroat trout hybrids (SWCA Environmental Consultants, 

2006). Serial depletion backpack shocking in Bright Angel Creek below Phantom Creek resulted in 

an estimated average removal efficiency of 85 percent for brown trout and 91 percent for rainbow 

trout in the sampling area during three electrofishing passes (Sponholtz and VanHaverbeke, 2007). 

Removal efficiencies in the headwater areas using backpack shocking were estimated to range from 

38 to 56 percent for each electrofishing pass (SWCA Environmental Consultants, 2006). In 2003, 

brown trout and rainbow trout composed 40 and 50 percent, respectively, of the trout captures 

using electrofishing (extrapolated from Leibfried and others, 2003) below Phantom Creek. In 2006, 

brown trout and rainbow trout composed approximately 25 and 75 percent, respectively, of the 

trout captures using electrofishing (Sponholtz and VanHaverbeke, 2007). This suggests that the 

brown trout composition may have been reduced by removal of brown trout during periodic 

operation of the weir in combination with backpack electrofishing.

In spite of disrupting upstream migration of brown and rainbow trout in spawning condition

as the result of the weir, small life-history stages of trout were captured in Bright Angel Creek

(Sponholtz and VanHaverbeke, 2007; SWCA Environmental Consultants, 2006), suggesting

continued juvenile recruitment from sources within the creek. The length frequency of rainbow 

trout captured with electrofishing has changed little, with a juvenile cohort (about 100 to 160 mm)

representing approximately 90 percent of rainbow trout captured in 2006 and an adult cohort (about 

240 to 300 mm) representing the remaining 10 percent. However, the length frequency of brown 

trout captured in the lower reaches of Bright Angel Creek during backpack shocking surveys 

shifted toward smaller individuals in 2007. In 2003, two cohorts were distinguishable for brown 

trout captures using backpack electrofishing. The juvenile cohort (about 70 to 130 mm) composed 

55 percent of brown trout captured. A second cohort (about 190 to 250 mm) composed 25 percent 
32

of brown trout captured, with the remaining 20 percent being greater than 250 mm (n = 124) 

(National Park Service, unpub. data). In a similar survey conducted in 2006, only one cohort is 

represented (about 100 to 175 mm), representing more than 95 percent of brown trout captured (n =

158) (Sponholtz and VanHaverbeke, 2007). Catch-rate information for trout was not available for 

relative abundance comparisons among years. The shift to a single juvenile cohort of brown trout in 

2006 indicates that spawning is still occurring in Bright Angel Creek despite the removal of large 

adults and suggests that juvenile brown trout growth rates may have increased because of assumed 

reduced density. 

Construction and operation of a weir could potentially be applied to capturing trout species 

in many of the tributaries in Grand Canyon. The operation of the weir in combination with 

backpack electrofishing to remove trout from Bright Angel Creek was beginning to show signs of 

potential effectiveness. Bright Angel Creek continues to represent a potential source of brown trout 

into the mainstem. Further analysis of available data is warranted to determine potential effects of 

this project on the abundance of brown trout in the confluence area. As results become available, 

this information should be incorporated into nonnative fish planning approaches.

Grand Canyon National Park, in cooperation with SWCA Environmental Consultants, 

initiated a native fish habitat restoration project in Shinumo Creek from 2004 to 2005. This project 

involved a rainbow trout reduction feasibility assessment in preparation for translocation of 

humpback chub into the creek. Valdez and others (2000) recommended implementation of 

nonnative fish management before attempting translocations of humpback chub into Grand Canyon 

tributaries. The feasibility assessment at Shinumo Creek suggested that backpack shocking would 

be most effective in capturing rainbow trout in the upper reaches of the creek (Leibfried and others, 

2004; More information on trout relative abundance, distribution, and backpack electrofishing 

removal efficiency is available from Grand Canyon National Park.).

Rainbow trout have been captured throughout Shinumo Creek (Allan, 1993) and in the 

mainstem in proximity to the confluence area (Rogers and others, 2008). Similar to the Little 

Colorado River humpback chub aggregation, rainbow trout are likely to negatively affect 

humpback chub in the Shinumo Creek inflow aggregation identified by Valdez and Ryel (1995). 

Studies that directly link rainbow trout originating from Shinumo Creek to the mainstem have not 

been conducted. However, it appears possible that rainbow trout could be displaced from the creek 

into the mainstem during flood events. For example, reconnaissance sampling conducted by Grand 

Canyon National Park, SWCA Environmental Consultants, and Grand Canyon Wildlands Council 

in Clear Creek resulted in no rainbow trout captures where rainbow trout had been common 

previously (Maddux and others, 1987). This indicates that trout had likely been displaced from the 

creek during the winter floods of 2005 (More results are available from Grand Canyon National 

Park.). Although the fate of displaced trout is unknown, this suggests a mechanism by which trout 

from tributary streams may contribute to mainstem populations. 

During 2009, GCNP led efforts to reduce rainbow trout using electrofishing in the lower 3 

km of Shinumo Creek in preparation for a humpback chub translocation project. A translocation of 

300 humpback chub was completed in June 2009. Further evaluation of the efficacy of backpack 

electrofishing to reduce rainbow trout abundance in Shinumo Creek is warranted as data become 

available and this information should be incorporated into nonnative fish planning approaches. 

However, further electrofishing in Shinumo Creek to test the effectiveness of mechanical removal 

of rainbow trout is subject to U.S. Fish and Wildlife Service permits. 
33

In 2006, the GCMRC, in cooperation with Loyola University, University of Wyoming, and 

Idaho State University, began a research project to estimate the relative importance of the various 

food resources to fish in the Grand Canyon ecosystem to establish the degree to which native fish

are limited by food resources (Rosi-Marshall and others, 2008). Investigators are measuring the

supply of basal food resources such as primary production by riverine algae, inputs from Lake 

Powell, and litterfall from riparian vegetation as well as the rates of secondary production of 

macroinvertebrates in the river system. To establish trophic relationships, measurements of 

macroinvertebrate gut contents and stable isotopes are taken to determine energy flow from basal 

food resources to macroinvertebrates. Ultimately, the combination of all the above measurements 

with fish production, diets, and isotope composition will provide an estimate of the energy flow to 

native fish such as humpback chub, flannelmouth sucker, and common nonnative species such as 

common carp, fathead minnow, and rainbow trout. 

These data will allow for estimates of the dominant food sources for these fish and 

estimates of potential food limitation and competition among native and nonnative species.

Measurements of food resource production and inputs, secondary production, and energy flow in 

the food web will provide a basis for developing hypotheses and a monitoring plan that can help 

guide adaptive management strategies focused on threatened native fish species (Rosi-Marshall and 

others, 2008). As results become available, this information should be incorporated into the 

development of the nonnative fish risk assessment.

The GCMRC, in cooperation with Loyola University Chicago, initiated a study to 

determine the potential impacts of water temperature and variable velocity on lower trophic levels 

of aquatic ecosystems. Cooperators are studying the response of algae and invertebrates in artificial 

streams to conditions that mimic (1) the daily changes in velocity from Glen Canyon Dam 

hydropeaking (constant-velocity with low and high daily fluctuations) and (2) predicted release 

temperatures below Glen Canyon Dam with a selective withdrawal structure (10 and 15oC). Algae 

and Gammarus lacustris (an amphipod crustacean) from Lees Ferry and a black fly species closely 

related to those in Lees Ferry were used in the experiments.

Preliminary results indicate that water temperature had a strong and positive effect on algal 

biomass, algal chlorophyll, net primary production, and individual growth rates for larval black 

flies (T. Kennedy, U.S. Geological Survey, oral commun., 2009). Collectively, preliminary results 

indicate that increases in the water temperature along the Colorado River could lead to a significant 

increase in the biomass and production of food items that are important to fish, particularly those 

species that are common along downstream reaches. Additionally, daily fluctuations in water 

velocity do not appear to have adverse impacts on algae or invertebrates (T. Kennedy, U.S.

Geological Survey, oral commun., 2009).

Integration of the results from the food base and flume studies will assist in determining 

factors such as food limitation and subsequent competition that may contribute to the negative 

impacts nonnative fish place on native fish. Identification of the conditions that cause predation or 

competition among species will assist scientists in developing nonnative fish control prescriptions 

that may minimize these negative interactions. As results become available, this information should 

be incorporated into the development of a nonnative fish risk assessment.
34

The ability to capture nonnative fish and detect changes in their abundance and distribution

is vital to developing management plans and prioritizing nonnative management efforts. If changes 

in the status of nonnative fish are not detected, then a rapid response to reduce nonnative species 

abundance is compromised. Review of the fish-sampling activities in Grand Canyon reveal several 

information needs as well as promising options for developing nonnative fish monitoring and 

control approaches.

Currently, effective mainstem nonnative fish monitoring programs are in place for rainbow 

and brown trout and possibly common carp. Effective monitoring in not ongoing for other 

prominent nonnative fish species in the mainstem Colorado River, including fathead minnow, red 

shiner, channel catfish, bullhead spp., green sunfish, smallmouth bass, and striped bass. This 

limitation is likely the result of widely varying and sometimes low frequency of the capture of 

these species, which is exacerbated by the low capture efficiency of gears currently used in Grand 

Canyon fish sampling activities. Lack of robust monitoring data results in an inability to (1) 

identify changes in nonnative fish populations that warrant control actions, (2) detect newly 

invading species, and (3) evaluate effectiveness of removal programs. The development of a 

mainstem nonnative fish monitoring protocol to detect changes in abundance and distribution of the 

nonnative fish listed above is a necessary step towards addressing nonnative fish control 

approaches. Monitoring activities should initially be conducted in proximity to humpback chub 

aggregations and tributary inflows.

With the exception of the Little Colorado River, there are currently no fish monitoring 

programs in place within the tributaries of Grand Canyon. Sampling in tributaries has been 

sporadic and extensive sampling in tributaries only occurred in the mid 1980s, early 1990s and in 

2004 and 2005. Tributary streams in Grand Canyon contain both native and nonnative fish; 

however, the diversity of nonnative fish found in tributaries warrants concern because tributaries 

are likely sources of nonnative fish to the mainstem Colorado River. Development of a tributary 

fish monitoring protocol to detect changes in the abundance and distribution of nonnative fish 

currently present in tributaries and to detect new invading fish species is necessary for addressing 

nonnative fish control in Grand Canyon. 

Lees Ferry is an area where new nonnative species introductions can be anticipated. The 

ability to detect new fish species in Lees Ferry is an issue because the invader can then disperse 

throughout the entire river system below Glen Canyon Dam. Currently, there are no monitoring 

programs in place dedicated to the detection newly invading nonnative fish in Lees Ferry or Grand 

Canyon, although, standard Lees Ferry monitoring protocols may be adequate for detecting adult 

smallmouth bass and walleye. Currently, the method developed to target YOY rainbow trout in 

Lees Ferry represents the only method available for detecting the presence of YOY nonnative fish 

such as channel catfish, smallmouth bass, and green sunfish in this reach. This method will be

incorporated into a monitoring protocol to detect new invading fish species or recruitment of 

existing nonnative fish in Lees Ferry in 2010. This method could also provide information for the 

development of river-wide nonnative fish monitoring protocols in the future.

Two techniques have been tested that show promise in evaluating movement patterns of 

native and nonnative fish: (1) acoustic telemetry to track individual fish movement and (2) remote 

PIT-tag detectors. Manual tracking of acoustic tags can be used to track fish (>160 mm) movement 

to specific locations. Remote PIT-tag detectors can be used to track fish (>100 mm) movement 

patterns within tributary streams. Comparing movement patterns will allow scientists to identify 

special and temporal conflicts among native and nonnative species. This will assist in the 
35

development of control prescriptions targeting vulnerabilities of nonnative fish while benefiting 

native fish.

Removal methods attempted in Grand Canyon showing promise for nonnative fish control 

applications include: (1) electrofishing to reduce mainstem trout abundance and potentially 

smallmouth bass and walleye; (2) catfish hoopnets baited with stink cheese to capture channel 

catfish; (3) weirs, angling, and backpack electrofishing to reduce trout abundance in tributary 

streams. Although these methods may not result in efficient removal of nonnative species in some 

cases, they are the only techniques currently available to attempt nonnative fish control. No other 

methods have been determined to be consistently feasible or more effective in capturing 

presumably rare nonnative fish in Grand Canyon. Many techniques have been attempted to capture 

rare nonnatives, including slat traps, fyke nets, bow-fishing, electrofishing settings specific for 

catfish, trot lines, standard and experimental gill nets, trammel nets of various mesh sizes, and bag 

seines, to name a few. To date, very few tools have been proven adequate for application to 

nonnative fish control in Grand Canyon. The GCMRC and its cooperators will continue to 

investigate and refine effective methods for monitoring and control of nonnative fish in Grand 

Canyon. 

Biologists conducting the nearshore ecology project are attempting to quantify abundance, 

survival, habitat use, growth, and natal source of juvenile humpback chub over three flow periods. 

Based on the 2008 pilot studies, information on fathead minnow abundance and habitat use in the 

study area may also be periodically obtained (M. Yard, U.S. Geological Survey, oral commun., 

2009). Techniques and insights developed by this project will help to (1) identify habitat overlap 

and potential competition juvenile humpback chub may experience from fathead minnows, (2) 

develop effective systemwide nonnative fish monitoring protocols, and (3) detect natal sources of 

nonnative fish.

In addition to fish sampling projects, food base studies are underway in Grand Canyon. 

Food base studies include the field measurement of food sources and trophic relationships. 

Additionally, scientists are using temperature and water level fluctuation simulations in an artificial 

stream to evaluate the impacts of these factors on lower trophic levels of the Grand Canyon food 

web. Integration of the results from the food base and experimental stream studies will assist in 

determining factors that may adversely affect natives such as food limitation and subsequent 

competition among native and nonnative fish. Additionally, the GCMRC is currently incorporating 

this information into an ecosystem model to identify limiting factors in humpback chub recruitment 

dynamics including food base and temperature limitation and predation or competition. Valdez and 

Speas (2009) evaluated the benefits of three temperature scenarios on potential fish spawning, 

incubation, and growth in Grand Canyon. They determined that warming release temperatures had 

the potential to benefit all native fish in Grand Canyon, however, these conditions were also 

suitable for seven out of ten warmwater nonnative species examined. Identification of the 

mechanisms that potentially limit humpback chub recruitment will assist scientists in developing 

nonnative fish control prescriptions that may minimize negative impacts on juvenile humpback 

chub. The GCMRC is currently developing and ecosystem model to assist in the identification of

these mechanisms. As results become available, this information should be incorporated into 

nonnative fish control planning and the development of a nonnative fish risk assessment.

The information presented above provided the basis for developing the recommendations 

and options for nonnative fish monitoring, research and control in Grand Canyon that follow. There 

is an immediate need to address known issues of native fish conservation in Grand Canyon while 
36

improved nonnative fish capture and control strategies are being developed. The objective of this 

plandocument is to review fish-related programs conducted in Grand Canyon and provide 

prioritized suggestions for (1) monitoring improvements, (2) nonnative control methods options 

available for use in Grand Canyon, (3) new research projects to address information needs, and (4) 

contingency planning and funding. These recommendationoptions draw upon the experiences of 

other nonnative fish control programs, including the Upper Colorado River Endangered Fish 

Recovery Program and other programs around the world. These recommendationoptions are 

consistent with GCDAMP management objectives and the HBCCP and address SSQs and INs 

related to nonnative fish in Grand Canyon. These recommendationoptions are based on the best 

available science, information, and professional judgment (Persons and others, 2003; Francis and 

others, 2007). This approach should be revisited as necessary to incorporate new information from 

nonnative fish studies conducted in Grand Canyon, the results of other nonnative fish control 

programs, and new research information. 

RecommendationOptions presentedmade here rely on nonnative species monitoring, 

research, and control methods that are readily available for implementation in the near future. 

RecommendationOptions presented here are prioritized based on discussions among fisheries 

scientists and cooperators participating in three nonnative fish workshops. Formulation of 

recommendations control options is hindered by the challenge of determining whether predation, 

competition, habitat alteration, or a combination of these mechanisms is most critical to consider. 

The GCMRC has made progress in developing an ecosystem model that will assist scientists in 

evaluating the nature of risks imposed to native fish by nonnative species and other factors. 

Identification of the nonnative species that pose the greatest threat to natives is vital for focused 

management plans that prioritize removal efforts. In the meantime, the criteria used to determine 

the nonnative species to be the focus of management efforts included (1) current occupancy in the 

mainstem Colorado River in Grand Canyon and proximity to the Little Colorado River, (2) 

perceived likelihood of population expansion, (3) known predators on fish, and (4) need for 

improved monitoring or removal methods.

Although it would be ideal to pursue all of the recommendationoptions below for 

development of a comprehensive nonnative fish control strategy, it is unlikely that the GCDAMP, 

operating under a funding cap, could afford to do so. Agency managers, especially the Arizona 

Game and Fish Department, U.S. Fish and Wildlife Service, and National Park Service, should 

consult with GCDAMP committees to determine the scope and a logical order of control projects to 

be implemented each year during an annual meeting. Prioritization criteria will include known 

threats to natives, logistical feasibility (including shared logistics with other efforts), probability of 

success, degree of risk to natives, funding considerations, and permit requirements for Federal, 

State and Tribal agencies. Implementation of these recommendationoptions will require agreement 

among management agencies as to their roles and responsibilities in managing nonnative fish and 

prioritization of control projects (See Implementation Strategies below).

Grand Canyon fish scientists and managers make the following assumptions regarding 

nonnative fish control planning (modified from Persons and others, 2003). These assumptions are 

reflected in more specific recommendationoptions that follow.

Nonnative fish negatively affect native fish through predation and competition and are a major 

threat to the persistence of native fish in Grand Canyon.

Removal or reduction of nonnative fish populations will be of some benefit to native fish.
37

To increase effectiveness and efficiency, nonnative fish control planning will consider sources 

of nonnatives such as tributaries, streams, and reservoirs within Grand Canyon and Colorado 

River watersheds. 

Control strategies will not eliminate nonnative fish from Grand Canyon and will require 

multiple and persistent control actions through time to be effective.

Nonnative fish are not the sole factor negatively impacting humpback chub in Grand Canyon,

although, nonnative fish control may result in benefits to native fish. 

The negative impacts of nonnative fish on native fish can be synergistic when interacting with 

other factors such as flow regimes, water quality, and pathogens that may also exert negative 

impacts.

The Colorado River ecosystem is a dynamic environment where continued change can be 

expected, meaning the threats from nonnative fish can be expected to change over time and, 

species that pose the greatest threats to native species may also change.

As management agencies begin to prioritize nonnative fish control efforts and define their 

roles in the overall effort, there are a number of issues, or threats, that need to be considered. Based 

on the data about fish captures in Grand Canyon presented above, a review of current monitoring 

protocols, and discussions with scientists and managers in this and other nonnative fish 

management programs around the world, a list of issues is presented below. The issues presented 

below identify nonnative species and geographic targets of concern and information and 

programmatic needs for nonnative fish control planning upon which recommendations and options 

presented below have been developed. This list provides the basis for strategic planning and, in the 

case of the mechanical removal project, implementation of nonnative fish research 

recommendations and control recommendationoptions. This list should be revised as new 

information is gained. The GCDAMP will likely address some, but not all, of these issues. 

Management agencies will need to work with the GCDAMP and each other to determine the level 

of risk from these threats they are willing to accept and how they may be able to accomplish 

control and management actions to address threats deemed important.

Address abundance of rainbow trout in proximity of the Little Colorado River that may impact 

young humpback chub in the mainstem

Address recent increase in captures of channel catfish and bullhead in the Little Colorado River 

area that may impact young humpback chub in the tributary and the mainstem

Address brown trout production in Bright Angel Creek that may impact native fish in tributaries 

and the mainstem

Address potential upstream movement of warmwater nonnative fish, including striped bass, 

from below RM 236 and Lake Mead that may impact native fish in the mainstem

Identify sources of nonnative fish into Grand Canyon, including spawning areas, reservoirs, 

dam passage, tributary inputs, and illegal stocking, which may impact native fish in tributaries 

and the mainstem

Prevent new nonnative fish species invading Grand Canyon from Lees Ferry and other sources
38

Identify the mechanisms and nonnative species posing the greatest negative impact on juvenile 

humpback chub

Improve nonnative fish monitoring methods, early detection protocols, and capture methods

Need for management agency involvement in the implementation of control programs

Consider scenario presented by Valdez and Speas (2009) regarding temperature suitability and 

species of concern (brown and rainbow trout, walleye, smallmouth bass, and redside shiner)

The implementation of the monitoring and research recommendations and control options 

presented in this plandocument will require coordination, consultation, or compliance with agency 

and tribal governments. Agencies include the National Park Service, Arizona Game and Fish 

Department, U.S. Fish and Wildlife Service, and Tribes with ties to the Grand Canyon. Research 

permits are required by GCNP to conduct work within the national park boundaries. The Arizona 

Game and Fish Department requires scientific collection permits for species under their 

jurisdiction, including nonnative fish and native fish that are not federally protected. The U.S. Fish 

and Wildlife Service requires permits when projects may result in the harm of endangered species. 

Tribal authorities require permits for scientists to conduct work and collect species within tribal 

boundaries. Implementation of monitoring and research recommendations and options within this 

document may also trigger consultation and compliance requirements associated with the 

Endangered Species Act, National Environmental Policy Act, National Historic Preservation Act

and Federal-Tribal Trust Responsibilities. Cultural values are recognized to conflict with options 

and recommendations presented in this document (See Tribal Concern section below). Necessary 

consultation and compliance will be the responsibility of appropriate management agencies. 

The current state of nonnative fish monitoring Grand Canyon limits the ability of scientists 

and managers to identify risks posed to native fish from changes in the abundance and distribution 

of several nonnative species or invasions of new species. This situation means threats may go 

undetected. Further, failure to promptly detect expansions of nonnative fish abundance and 

distribution may increase the costs and decrease the effectiveness and feasibility of control. This 

section focuses on improving monitoring and detection, the core components of implementing and 

evaluating removal strategies. These recommendations are presented in their order of importance. 

Mainstem monitoring using electrofishing is effective at monitoring trends in rainbow trout, 

brown trout, and potentially common carp, as well as some native fish. Other nonnative fish species 

such as channel catfish, bullheads, striped bass, and small-bodied fish are not effectively monitored 

using this protocol. Current mainstem monitoring protocols should be continued to monitor the 

suite of species for which the method is effective. However, application of other sampling methods 

should be considered. Information collected by expanding the current mainstem monitoring 

program to include a multitude of sampling gears would assist in the development of an occupancy 

model (see Research Recommendations below). Sampling methods may include slow shocking, 

trammel netting, seining, minnow traps, electric seines, fyke nets, angling, and large mesh gill nets. 

Each method should be evaluated for logistical feasibility and safety of deployment in Grand 

Canyon. Monitoring improvements should initially be attempted in proximity to humpback chub
39

aggregations and tributary inflows. While new nonnative fish-capture and monitoring protocols are 

being developed, mainstem electrofishing should continue as it provides the best nonnative fish 

monitoring information available at this time. Investigation of several maistem sampling methods 

near humpback chub aggregations and tributary inflow areas is planned for 2010 (See GCMRC 

FY2010–2011 budget and work plan). This recommendation addresses CMIN 2.4.1 and RINs 

2.4.1, 2.4.3, and 2.4.6 and HBCCP recommendations.

Lees Ferry is very likely to experience nonnative fish invasions or introduction resulting 

from dam passage, illegal stocking, distribution from the -12 mile slough, and even contributions 

from the Paria River. The slow shocking technique used to target early life-history stages of trout in 

the Lees Ferry reach has resulted in captures of small green sunfish and smallmouth bass. Lees 

Ferry trout monitoring using a standard electrofishing method is conducted three times per year and 

has resulted in captures of adult smallmouth bass and walleye. Continuing monitoring for early 

life-history stages and developing an invasive fish monitoring program for Lees Ferry (to include -

12 mile slough) will increase the likelihood of early detection and rapid response of newly invading 

or expanding nonnative fish populations in Lees Ferry. 

Incorporating the slow-shocking technique into the Lees Ferry monitoring program and 

developing an invasive fish monitoring program (to include -12 mile slough) is recommended. This 

activity is planned as part of Lees Ferry monitoring efforts in 2010 and 2011 (See GCMRC 

FY2010–2011 budget and work plan). These recommendations address CMIN 2.4.1 and RINs 

2.4.1, 2.4.3, and 2.4.6 and HBCCP recommendations.

With the exception of the Little Colorado River, there are currently no fish monitoring 

programs in place for Colorado River tributaries in the immediate vicinity of Grand Canyon. 

Tributaries known to contain nonnative fish, including the Paria River and Bright Angel, Shinumo, 

Tapeats, Kanab, and Havasu Creeks, should be included in a monitoring program. Developing 

monitoring protocols for these tributaries and confluence areas will not only assist in evaluating the 

condition of and changes in the fish communities found in these tributaries, but also will aid in the 

detection of new invaders into the Colorado River ecosystem. This information would assist 

scientists in assessing potential sources of nonnative fish into the mainstem and identifying areas 

that are potentially important for spawning and recruitment of native and nonnative fish. 

Identifying new invaders in tributaries before they reach the mainstem could provide opportunities 

to more efficiently control newly introduced species compared to attempting control in the 

mainstem. Data collected in tributary streams should be maintained in a centralized and accessible 

database similar to that of the data collected during most mainstem and Little Colorado River 

sampling efforts. 

Implementing a fish monitoring program in Grand Canyon tributary streams is 

recommended. This recommendation addresses SSQ 1-7, CMIN 2.4.1 and RINs 2.4.1, 2.4.3, 2.4.5 

and 2.4.6 and HBCCP recommendations.

The Grand Canyon presents a variety of logistical challenges to implementing nonnative 

fish control strategies. Here we make recommendationsdevelop options for nonnative fish control 

in Grand Canyon based on previous successes and experiments conducted in Grand Canyon and 
40

other national parks. These recommendationoptions represent techniques that have the greatest 

likelihood of reducing nonnative fish abundance in particular areas of Grand Canyon. Due to tribal 

concerns for culturally sensitive areas such as the Little Colorado River and the taking of life, 

development and implementation of nonnative fish removal control projects must be discussed 

among the management agencies and the tribes (See Regulatory Authority above and Tribal 

Concerns below). Removal recommendationoptions are listed in the order of priority.

In considering the continued use of mechanical removal of nonnative fish in the Little 

Colorado River reach several factors require consideration. First, the unplanned release of warmer 

water from Glen Canyon Dam is highly correlated with both a decrease in nonnative abundance 

(Coggins, 2008) and an increase in the Grand Canyon population of humpback chub (Coggins and 

Walters, 2009). However, in a hypothetical modeling scenario developed using trout diet 

information (Yard and others, in prep.) assessed the impact removed trout might have had on 

humpback chub had they not been removed. Assuming that trout captured during mechanical 

removal were not removed, and fish abundance and catchability conditions remained the same 

during the diet study period, the number of humpback chub that could have been consumed these 

trout had they not been removed would be approximately 12,169 over 1.76 year diet study period 

(2003-2004). Thus, it is still unclear that mechanical removal of nonnative fish is benefiting native 

fish.

As a result, continued large-scale experimentation will be required to understand what 

factors benefit native fish, although, modeling approaches may help answer these questions. 

Second, if managers decide to maintain depressed nonnative populations, an ongoing strategy of 

control must be developed. Given the essentially fixed cost of removal efforts and fixed capture 

probability, the per capita removal expense increases as nonnative abundance falls. This implies 

that complete removal of nonnative species, if even possible, would require a huge expense. 

With this in mind, it is logical to establish a non-zero target abundance of nonnative fish 

and periodically apply control efforts to achieve that level. Unfortunately, defining this target in a 

scientifically credible manner is daunting. Completion of this task presumes a level of 

understanding of the direct and indirect mortality sources on native fish from nonnative fish that 

may not be attainable. Although simple models such as those developed by Paukert and Petersen 

(2007) may provide some guidance on the strength of predatory and competitive interactions, it 

will still be necessary to define targets in some fashion. For instance, if the most important negative 

interaction between rainbow trout and humpback chub is presumed to be competition for food, the 

question becomes: how much more food do humpback chub need? Similar arguments can be made 

relative to predatory interactions between rainbow trout and humpback chub. To what degree 

should the predatory mortality rate be reduced? Although the GCMRC is constructing more 

elaborate models of ecosystem dynamics, these models will still need to be tested to confirm basic 

model assumptions.

While GCMRC constructs these models, scientists and managers should recognize that 

defining this target is predominantly an exercise in risk management rather than an implicit 

scientific question. It may be acceptable to arbitrarily define and maintain a low level of rainbow 

trout abundance (for example, 10 to 20 percent of January 2003 rainbow trout abundance) and 

continue monitoring to determine trends in native fish abundance and recruitment. The necessity of 

removing large portions of nonnative predators to benefit native species is generally supported in 

the literature. In a review of the impact of nonnative fish on native razorback sucker (Xyrauchen 

texanus) and bonytail chub (Gila elegans) conducted by Pacey and Marsh (1998), the authors 
41

suggest the complete eradication of nonnative fish from pond environments is necessary for 

survival of native species in these habitats. Weidel and others (2002) conducted smallmouth bass 

removal in an Adirondack lake and determined that removal of 43 to 88 percent of the smallmouth 

bass resulted in a positive response in other fish species. Harding and others (2001) modeled the 

impact of removing the nonnative red fox on the endangered California clapper rail (Rallus 

longirostris obsoletus). The authors found that reduction of the fox population by 50 to 70 percent 

correlated with population growth of the rails in the following year. Dudley and Matter (2000),

however, observed no increase in recruitment of Gila chub (Gila intermedia) when more than 90 

percent of the nonnative green sunfish population was removed in isolated pools in a small desert 

stream. The authors indicated no YOY Gila chub were observed in both the experimental (no green 

sunfish) and control pools (green sunfish present). However, they observed abundant Gila chub 

YOY in other areas of the stream occupied by green sunfish, indicating a potential issue with the 

experimental design. These studies generally support the need for large reduction targets to affect a 

positive response in desired species. Setting long-term targets for nonnative fish removal will likely 

require continued investigation and refinement of removal strategies, continued monitoring of 

native fish response in the removal reach, and consideration of logistical and budgetary limitations. 

If managers and scientists agree that the reduction target for rainbow trout in the Little 

Colorado reach is maintaining 10 to 20 percent of January 2003 rainbow trout abundance, a model 

developed by the GCMRC (L. Coggins, GCMRC, pers. commun., 2009) provides some guidance 

on the logistical requirements for achieving this goal. Reaching the 10 to 20 target in the Little 

Colorado River reach (approximately 600 to 1,200 rainbow trout) could be achieved with a 

minimum of two trips per year assuming a low immigration rate of rainbow trout into the Little 

Colorado River Reach (<50 fish/month; fig. 6). If immigration rates are higher (300 fish per 

month), then three or more trips per year will be required to maintain this abundance level (fig. 6).
42

 

Alternatively, managers may wish to commit to an annual level of spending on control 

efforts consistent with perceived risk and simultaneous attainment of other program objectives. 

These strategies are consistent with the general philosophy of adaptive management and recognize 

that mechanical removal actions are opportunities to increase knowledge while simultaneously 
43

maximizing benefit and minimizing risk to a focal resource. Consistent with the April 2007 

workshop recommendation to maintain lower levels of predators and competitors in critical reaches 

to support humpback chub conservation (Grand Canyon Monitoring and Research Center, 2008),

mechanical removal of trout in the proximity of the Little Colorado River confluence will be 

continued in 2010. 

Maintenance of the rainbow trout abundance at 10 to 20 percent of January 2003 level in 

the Little Colorado River reach is recommendedwarranted. Evaluation of the potential of 

mechanical removal above the Little Colorado River reach to reduce rainbow trout abundance

downstream in the Little Colorado River reach should also be considered. While mechanical 

removal efforts in the LCR inflow reach may have contributed to the reduction of rainbow trout 

and other nonnative fish abundance, there are long-standing concerns by Native American 

stakeholders about conducting removal efforts in culturally sensitive areas such as the LCR. 

Additionally, mechanical removal efforts in this portion of the river are both financially and 

logistically demanding. As such, other alternatives to mechanical control in the Little Colorado 

River reach should be evaluated. Possible alternatives to reducing rainbow trout abundance in the 

Little Colorado River reach include conducting mechanical removal immediately below the Paria 

River, using flow manipulations to limit recruitment of nonnative fish, increasing turbidity through 

augmentation, and other strategies (See Research Recommendations below). This 

recommendationoption addresses SSQs A, B, and 1-4; CMIN 2.4.1; and RINs 2.4.1, 2.4.2, and 

2.4.6; and EIN 2.4.1 and HBCCP recommendations.

Nonnative fish control is recommended in three Grand Canyon tributaries: Little Colorado 

River, Bright Angel Creek, and Shinumo Creek. Nonnative fish removal in these three tributaries is 

recommended based on the availability of recent sampling information, likelihood of effective 

nonnative fish control methods, and the presence of native fish. The Little Colorado River was 

selected because of its importance for humpback chub spawning (Kaeding and Zimmerman, 1983; 

Paukert and others, 2006) and its potential as a source of warmwater nonnative fish into Grand 

Canyon (Stone and others, 2007). Bright Angel Creeks was selected because data indicates that it is 

a source of nonnative trout species into the mainstem (Leibfried and others, 2003) and it contains

native fish communities. Shinumo Creek was selected because it is a humpback chub translocation 

site; Valdez and others (2000) recommended the implementation of nonnative fish management 

before attempting translocations of humpback chub. Tapeats Creek was not selected because of the 

lack of information identifying this tributary as a source of nonnative fish to the mainstem. 

Initiating nonnative fish control efforts in Little Colorado River, Bright Angel Creek, and Shinumo 

Creeks to benefit native fish residing within the tributary and reducing sources of nonnative fish 

into the Colorado River is recommended. This recommendationoption addresses SSQs A, B, and 1-

7; CMIN 2.4.1; and RINs 2.4.1, 2.4.2, and 2.4.3 and HBCCP recommendations.

Trout reduction in Shinumo Creek should be conducted with a combination of gears such as

weirs, backpack shockers, hoopnets, and angling to reduce local nonnative fish abundance before 

additional translocation of native fish. Backpack shocking could be used in the summer months to 

capture rainbow trout in the upper reaches (above White Creek confluence area) where water 

temperatures are cooler, trout densities were greater (Leibfried and others, 2004), and the presence 

of translocated humpback chub would not be as likely. These control efforts may also be applied to 

manage contributions of rainbow trout to the mainstem and the potential negative effects on the 
44

Shinumo inflow humpback chub aggregation. Reduction efforts should be focused on times when 

nonnative fish are most vulnerable to capture methods such as during low-flow conditions or 

spawning migrations. Temporary weirs placed throughout the creek could be used during the 

summer to target trout moving upstream to escape warming water temperatures in the lower 

reaches and could also target movement associated with spawning periods. For other nonnative fish 

removal recommendationoptions in tributary streams, see the Chemical Renovation and Barrier 

Construction section below. 

Investigation of continued nonnative fish removal in Shinumo Creek using backpack 

shocking, weir operations, and chemical renovation in combination with barrier construction is 

recommended. These recommendationoptions address SSQs A, 1-4, and 1-7; CMIN 2.4.1; and 

RINs 2.4.1, 2.4.2, 2.4.3, 2.4.5, and 2.4.6 and HBCCP recommendations.

Bright Angel Creek may be a major source of nonnative brown and rainbow trout into the 

mainstem. These fish likely negatively affect native fish through predation and competition both 

near the Bright Angel Creek confluence and possibly more distant locations through dispersal and 

migration. Operation of a weir at the mouth of Bright Angel Creek in combination with backpack 

electrofishing samples appeared to impact the population structure of brown trout in the creek. 

Continued operation of the weir in Bright Angel Creek in combination with backpack shocking 

above the weir is recommended to remove upstream migrating brown trout and rainbow trout. 

These actions could assist in maintaining reduced rainbow and brown trout catch rates currently 

observed in the mainstem, complement removal efforts conducted near the Little Colorado River, 

and reduce resident trout abundance to benefit native fish found in Bright Angel Creek. Reduction 

should focus on times when nonnative fish are most vulnerable to capture methods such as during 

spawning migrations. These control efforts may also be applied to manage contributions of trout to 

the mainstem and the potential negative effects on the Bright Angel inflow humpback chub 

aggregation. For other nonnative fish removal options in tributary streams, see the Chemical 

Renovation and Barrier Construction section below. 

Investigation of continued nonnative fish removal in Bright Angel Creek using backpack 

shocking, weir operation, and chemical renovation in combination with barrier construction is 

recommended. These options address SSQs A, 1-4, and 1-7; CMIN 2.4.1; and RINs 2.4.1, 2.4.2, 

2.4.3, 2.4.5, and 2.4.6 and HBCCP recommendations.

Several species of nonnative fish have been captured in the Little Colorado River since 

1988 (Stone and others, 2007). In the early 1990s, the dominant species shifted from channel 

catfish and bullhead species to species in the minnow family, most notably common carp and 

fathead minnow (Gloss and others, 2005). However, in 2008, captures of channel catfish and 

bullhead species in the Little Colorado River and the mainstem were greater than previous years, 

indicating a potential increase in the abundance of these species in that area. Small life-history 

stages of common carp and channel catfish have been captured in the Little Colorado River, 

indicating possible spawning of these species in the lower reaches of the tributary or invasion of 

these individuals from upstream sources within the watershed (Stone and others, 2007). Channel 

catfish is a species of concern in Grand Canyon because of its potential to expand with warming 
45

water temperatures and its presence in the Little Colorado River, which could negatively affect the 

humpback chub aggregation found there.

The results of a nonnative fish pilot project conducted in 2007 and 2008 suggest that a 

combination of a different hoop net (catfish net) and bait type (stink cheese) may result in greater 

numbers of channel catfish captures than the methods currently used for fish monitoring. Although 

this technique has not been fully evaluated, it appears to be effective in capturing channel catfish 

and may improve the ability to monitor changes in channel catfish abundance. Further pilot testing 

to evaluate the feasibility of using catfish nets and stink cheese to reduce and monitor channel 

catfish and bullhead species in the Little Colorado River and the confluence area is warranted. 

However, scientists have expressed concern that the mesh size of the catfish net (1 1⁄2‖) could result 

in gilling and mortality of subadult humpback chub or other native fish.

In 2003, the Arizona Game and Fish Department conducted preliminary testing of capture 

methods for common carp and channel catfish in the Little Colorado River (Arizona Game and 

Fish Department and U.S. Geological Survey, unpub. data, 2007). These methods included hoop 

nets, angling, slat traps, bow fishing, and spearfishing and were tested in approximately the lower 2 

km of the river. Further testing of these methods is recommended to determine capture efficiencies 

of the various gears and evaluate their applicability to monitoring and management of nonnative 

fish. Monitoring the effects of removal on channel catfish and bullhead population size structure is 

important. During a nonnative fish removal project conducted from 2002 to 2007 in the lower San 

Juan River using electrofishing, 11,581 channel catfish were removed, however, a significant 

decrease in the size structure of channel catfish also occurred (Elverud, 2008). Because the impacts 

that various life stages of nonnative fish have on native fish is poorly understood, monitoring native 

and nonnative population responses to removal efforts is important for minimizing unintentional 

impacts of removal.

Investigation is recommended of nonnative fish reduction and monitoring methods that do 

not impact humpback chub in the Little Colorado River and the confluence area. These 

recommendationoptions address SSQs A and 1-7; CMIN 2.4.1; and RINs 2.4.1, 2.4.3, and 2.4.6 

and HBCCP recommendations.

Chemical renovations of rivers and streams using piscicides to control nonnative fish have 

benefited many threatened and endangered species. To increase the likelihood of success, these 

projects must be combined with a physical barrier in the channel to prevent reinvasion of nonnative 

fish from downstream sources and renovations of upstream sources of nonnative fish such as ponds 

or perennial pockets of water within the watershed. Chemical renovation may also involve capture 

of native and endangered fish for restocking after piscicides are detoxified. A combination of these

nonnative fish control strategies and native fish conservation actions could be applied to Grand 

Canyon. Barrier placement should be carefully considered so as to minimize negative effects on 

native fish that may exhibit transient use of the tributaries. Barriers should be strategically 

positioned to minimize negative impacts and maximize benefit to native fish. For example, in the 

case of Bright Angel Creek, a barrier positioned above the campground could afford angling

opportunities in areas of concentrated visitor use while reclaiming the upper reaches of the creek 

for native fish conservation (P. Sponholtz, US Fish and Wildlife Service, pers. commun., 2010)

Piscicides have been used to eradicate or control nonnative fish and protect endangered 

species in several national parks. To benefit native brook trout, antimycin A was used successfully 

in Great Smoky Mountains National Park to control of nonnative rainbow trout in small streams 

where mechanical removal by electrofishing was ineffective (Hammonds and others, 2006). 
46

Renovations were conducted before translocation of brook trout. Researchers determined that the 

cost of chemical treatment was significantly less than previous unsuccessful removal attempts 

using backpack electrofishing in the same stream segment (Hammonds and others, 2006). 

Antimycin A is also being used in Yellowstone National Park to eradicate nonnative brook trout in 

tributary streams of Yellowstone Lake to protect native cutthroat trout (Oncorhynchus clarki 

bouvieri). The success of the renovations was attributed to proper piscicide application and 

detoxification, combined with natural barriers to upstream migration of nonnatives and 

translocation of native fish after renovation (Gresswell, 1991). Ten years of nonnative brook trout 

removal using piscicides and electrofishing in combination with barrier construction resulted in an 

almost threefold increase in abundance of native bull trout (Salvelinus confluentus) at Crater Lake 

National Park (Buktenica and others, 2001; Renner, 2005). In many of these cases, mechanical 

removal was determined to be ineffective in obtaining conservation goals. Mechanical removal also 

required greater long-term expenditures than chemical renovation and barrier construction.

Chemical renovation and barrier construction in tributary streams identified as sources of 

nonnatives, along with restocking and translocation of native species, are the preferred technical 

option for eliminating or reducing sources of nonnatives into the mainstem Colorado River. The 

risks of chemical renovation to native fish should be assessed before implementation. This 

recommendationoption addresses SSQs A, B, and 1-7; CMIN 2.4.1; and RINs 2.4.1, 2.4.2, and 

2.4.3 and HBCCP recommendations.

Research into the biology of nonnative Grand Canyon fish, possible target strategies, and 

future control options will be required to develop effective nonnative fish control strategies. The 

research recommendations that follow are drawn from or respond to information needs identified 

by the GCDAMP, literature reviews, annual nonnative fish workshops, and review of Grand 

Canyon fish monitoring and research information. Recommendations are listed in order of priority.

The formulation of nonnative fish control prescriptions is hindered by the challenge of

determining the specific risks nonnative fish pose to native species. For example, is predation, 

competition, or the combination of both the greatest threat? Many approaches to assess nonnative 

fish risks to native fish are available, including (1) scoring or ranking various aspects of the fish 

community, (2) using bioenergetic assessment to evaluate negative interactions, and (3) employing 

ecosystem approaches, including a variety of biotic and abiotic variables. For example, Johnson 

and others (2008) developed a bioenergetics model to evaluate the consumptive demand of three 

nonnative predatory fish on native species in the Yampa River. For this multiyear effort, the 

authors gathered abundance, growth, and diet composition information for channel catfish, northern 

pike (Esox lucius), and smallmouth bass and determined that channel catfish consumed far fewer 

native fish than smallmouth bass or northern pike. Valdez and Speas (2009) have evaluated the 

potential benefits to Grand Canyon fish of the installation of a temperature control device at Glen 

Canyon Dam. The authors develop a model using temperature degree days to help evaluate the 

benefits of a temperature control device on fish spawning, incubation, and growth in Grand 

Canyon. Valdez (2008) also conducted an extensive literature search of the temperature 

requirements for native and nonnative fish in Grand Canyon and the surrounding area.

Information from the efforts discussed above should be used to develop a bioenergetics or 

ecosystem modeling effort that evaluates (1) which nonnative fish currently in Grand Canyon has 

the greatest impact on juvenile humpback chub survivorship; (2) the impact of potential changes in 
47

mainstem temperatures associated with a temperature control device, climate change, and dam 

operations on the bioenergetics or ecosystem relationships of native and nonnative fish; and (3) the 

impact of temperature on nonnative fish invasion and expansion risk. The goals of this modeling 

effort will be to identify population expansion or invasion risks to allow managers to control 

sources of nonnative species and to identify and prescribe a localized control effort that would 

reduce the greatest nonnative fish related threat to native fish. Assessment of the relative risk posed 

to native fish by nonnative fish is an important, but complex, component of developing nonnative 

control strategies. Such an assessment is needed to focus limited resources on those species and 

areas that are posing the greatest threat as well as to identify where such efforts may be effective. 

With the completion of this plandocument reviewing the past and addressing the present, that 

GCMRC will continue development of a nonnative fish risk assessment.

Identification of the nonnative species that pose the greatest threat to natives and 

determining when and where negative interactions occur is vital for focused management plans that 

prioritize removal efforts. This recommendation addresses MO 2.4, SSQ A, B and 5-6; CMIN 

2.4.1; RINs 2.4.1, 2.4.3, 2.4.4 and 2.4.6; and EIN 2.4.1 and HBCCP recommendations.

A review of the literature and fish capture information shows that nonnative fish enter into 

Grand Canyon through tributary inflows; passage through the Glen Canyon Dam turbines or 

spillway; legal and illegal stocking at access points such as Lees Ferry and Diamond Creek; 

dispersal from Lake Mead or Lake Powell; and stocking in the lakes, ponds, streams, and reservoirs 

within the watersheds that feed Grand Canyon. These sources may augment populations of 

nonnative species already present in Grand Canyon or contribute new species that may have 

irreversible effects on native species. Evaluation of literature such as historic stocking records, 

State sport fish stocking plans, nonnative fish captures on tribal lands as well as peer-reviewed 

literature pertaining to the watershed will assist in identifying sources of nonnative fish into Grand 

Canyon. Once sources of nonnative fish are determined, management strategies should be

developed to minimize the contributions of these sources into Grand Canyon. Identifying the 

sources of nonnative species will support the long-term sustainability of the control program and 

even reduce long-term expenditures.

Anecdotal information suggests that fish of all life stages can pass through Glen Canyon 

Dam turbines and survive. Glen Canyon Dam uses Francis turbines to generate power. Survival of 

small fish for turbine types with large water passages such as Francis turbines is commonly 70 

percent or greater, and these turbines are often installed in  ̳fish friendly‘ applications (Cada, 2001). 

In April 1984, a threadfin shad was captured 10 miles below Glen Canyon Dam, and on March 7, 

2008, a fishing guide at Lees Ferry observed an injured adult channel catfish at the water surface 9 

miles below Glen Canyon Dam during the experimental high flow (Dave Foster, Marble Canyon 

Outfitters, oral commun., 2008). These occurrences indicate at least occasional passage and 

survival of adult and juvenile fish though Glen Canyon Dam turbines. In June 2006, an adult 

walleye was captured 1 mile below Glen Canyon Dam, and, in April 2003 and April 2004, an adult 

and a juvenile smallmouth bass, respectively, were captured within 5 miles of the base of the dam. 

The presence of these species is likely a result of illegal stocking at Lees Ferry or passage through 

the dam. 
48

Identification of continued and new sources of nonnative fish into Grand Canyon is 

recommended. Research should focus on assessing contributions of nonnative fish from dam 

passage, tributary and watershed inputs. Expanded random electrofishing in the Lees Ferry reach 

should be employed to better assess nonnative fish in that reach. This recommendation addresses 

SSQ A; CMIN 2.4.1; RINs 2.4.1, 2.4.3, and 2.4.5; and EIN 2.4 and HBCCP recommendations.

Isotopes have been used extensively to determine thermal history and natal origins (when 

and where young fish are produced) of many fish species (Thorrold and others, 2001; Dufour and 

others, 2003; Feyrer and others, 2007). Otoliths are collected for isotope analysis as well as age 

determination studies. Knowledge of spawn timing and location for all fish species in Grand 

Canyon will help to focus nonnative removal methods and to identify important areas for native 

fish conservation. Currently, isotope samples are being collected throughout the Grand Canyon as 

part of the nearshore ecology project.

Isotope information, coupled with larval drift samples, could identify ―hot spots‖ of 

nonnative fish reproduction and recruitment, thus focusing nonnative fish control strategies. 

Common carp have a short larval period where they are susceptible to being flushed from spawning 

habitats by high-flow events. Targeting these downstream drifting larvae using ichthyoplankton 

nets set during high-flow events could be a cost-effective means of assessing the point sources of 

carp larvae within river systems. For example, targeted larval sampling was undertaken in 

catchments within the Murray-Darling Basin for a period of three carp breeding seasons. Data from 

these collections indicate that carp reproduction does not occur uniformly throughout river systems 

and that a majority of carp larvae originate from a relatively small number of locations within 

catchments (Gilligan and others, 2008) Once identified, these localized areas (for example, 

tributary streams or spring inflows in the mainstem) can be targeted with control options. Larval 

drift samples can provide data on temporal variability and factors contributing to common carp or 

other nonnative species spawn timing and success. 

Identification of areas important to nonnative fish reproduction through isotope and otolith 

analysis in combination with larval drift samples is recommended. Information gained from isotope 

techniques conducted as part of the ongoing nearshore ecology project should be utilized to 

develop strategies for this approach. Drift sampling downstream of tributary streams should be 

included in mainstem sampling efforts. This recommendation addresses SSQs A and 1 7; CMIN 

2.4.1; and RINs 2.4.1, 2.4.3, and 2.4.5.

Current monitoring protocols are adequate for detecting changes in brown and rainbow 

trout relative abundance, and possibly common carp, in the mainstem Colorado River. However, 

inferring abundance from catch rate information is difficult, often requiring an estimation of 

capture probability that is not trivial (Tyre and others, 2001; MacKenzie and others, 2006). A 

model evaluating species presence, or occupancy, can be used as a surrogate to determine the 

abundance of rare species (MacKenzie and others, 2006; MacKenzie and others, 2004, 2005) and 

may help to assess abundance of nonnative species that are difficult to capture in Grand Canyon. 

Occupancy modeling of fish populations has been demonstrated to be important and informative 

and may be a powerful alternative to capture-intensive methods for analyzing changes in nonnative 

species relative abundance and distribution. Citing logistical constraints of sampling a site 

repeatedly, the 2009 Fish Monitoring Protocol Evaluation Panel recommended against developing 

an occupancy model. However, it is possible that the challenges posed by logistical constraints 
49

could be overcome, especially if the nonnative fish monitoring program could be improved. The 

GCMRC intends to proceed with analyzing the feasibility of developing an occupancy model 

capable of determining appropriate levels of change in nonnative fish populations in the mainstem 

Colorado River and the logistics required for implementation of the sampling protocol. 

Evaluation of long-term monitoring protocols to detect changes in nonnative fish abundance 

and distribution using the occupancy framework is recommended. If the sampling requirements 

associated with protocol are logistically impractical, then sampling tributary inflows and humpback 

chub aggregations using catch rate indices of multiple gear types should be employed (see Fish 

PEP Recommendations). This recommendation seeks to improve the ability of scientists to address 

the majority of GCDAMP nonnative fish related information needs. This recommendation 

addresses CMIN 2.4.1, RINs 2.4.2 and 2.4.6; and EIN 2.4.1 and HBCCP recommendations.

Many small-bodied nonnative fish enter the mainstem from the Little Colorado River 

(Stone and others, 2007). Several of these species, including YOY common carp, fathead minnows, 

channel catfish, bullhead species, plains killifish, and green sunfish are rarely found in the 

mainstem upstream of the confluence area, although they are not unknown from this reach. Cool 

mainstem temperatures are thought to deter upstream movement of these species (Valdez and Ryel, 

1995; Johnstone and Lauretta, 2007). Current mainstem sampling programs may not effectively 

capture small bodied fish. A program to monitor the abundance of small-bodied warmwater 

nonnative fish is important for identifying recruitment events and evaluating the effects of warming 

mainstem temperature, flow regimes and tributary flow events on these species. Use of the slow 

shocking technique to target small-bodied in the mainstem in proximity of the Little Colorado 

River and other tributary inflows is recommended. This recommendation is reflected in the 

nearshore ecology study initiated in 2009. Expansion of this technique to other areas of the Grand 

Canyon should be explored as well.

Investigating capture and monitoring methods for small-bodied nonnative fish and YOY 

using the slow-shocking techniques described by Korman and others (2006) is recommended. This 

recommendation addresses SSQs A and 5-6; CMIN 2.4.1; and RINs 2.4.1, 2.4.3, and 2.4.6 and 

HBCCP recommendations.

Remote detectors for PIT tags have been used in stream systems to determine stream use 

and large-scale migration patterns and timing for many species. Ibbotson and others (2004) 

developed a remote system to detect PIT-tagged fish passing a series of antennae. These remote 

detectors have been modified to determine the directionality of the passing PIT-tagged fish and tag 

detection probabilities (Connolly and others, 2008). Pinder and others (2007) documented the first 

evidence of autumn migration of Atlantic salmon (Salmo salar) in the United Kingdom using a 

cross-river PIT tag detector. The use of remote PIT-tag detectors to track migration or residency of 

nonnative fish in tributary streams of Grand Canyon could help scientists evaluate the effectiveness 

of the periodic operation of temporary weirs or other removal efforts, among other things. 

Recommendations for which nonnative fish species and size classes to PIT-tag should be 

developed through discussions with scientists and managers during annual nonnative fish 

workshops (See Other Recommendations and Options below). Information gained from tagging of 

both native and nonnative species would be useful for focusing nonnative fish removal efforts on 

activities that provide the greatest benefit to natives. For example, detecting PIT-tagged common 

carp entering the Little Colorado River from the mainstem at a particular time would allow 
50

scientists to identify a possible threat to spawning humpback chub and apply removal strategies to 

take advantage of the period of movement. The GCMRC, in cooperation with the USGS Columbia 

River Research Lab and Arizona Game and Fish Department, has been testing a remote multiplex 

PIT-tag detector in the Little Colorado River.

To evaluate nonnative fish movement patterns and identify areas potentially important for 

spawning, establishment of remote PIT-tag detectors in select tributary streams of Grand Canyon 

and increasing nonnative fish PIT tagging efforts is recommended. This recommendation addresses 

SSQs A, B, and 1-7; CMIN 2.4.1; and RINs 2.4.1, 2.4.2, and 2.4.3.

The Tasmanian Inland Fisheries Service developed a strategy to remove common carp from 

Lakes Crescent and Sorell, Tasmania, that resulted in the complete eradication of common carp 

from Lake Crescent in 2009, approximately 15 years after common carp first invaded Lake 

Crescent (Tasmanian Inland Fisheries Service, 2009). This strategy involved identification and 

blockage of tributary inflow areas important for spawning and recruitment, implanting radio tags in 

common carp to assist scientists in targeting aggregations of fish for mechanical removal, and 

employing mechanical removal techniques, including electrofishing and gill netting. Of the 

mechanical removal methods employed, gill nets with 6-inch (152 mm) mesh captured 70 percent

of the total common carp catch. The 6-inch mesh size was selected to reduce entanglement of 

smaller native fish.

In Grand Canyon, common carp are rarely captured using electrofishing monitoring 

protocols in the mainstem or with hoop nets in the Little Colorado River. Large-mesh gill nets may 

result in greater captures of common carp or other large fish in both the mainstem and in the Little 

Colorado River. Gill and trammel net mesh sizes historically used in Grand Canyon have generally 

been between 1 and 3 inches (25 and 76 mm). Large-mesh gill nets should be investigated for use 

as a monitoring and control method for common carp in the mainstem and the Little Colorado 

River. Negative impacts of this method on native fish should be carefully considered during testing. 

(For fish aggregation targeting recommendations, see Sonic Telemetry section below. For 

identification of spawning areas, see Source Identification section above.) These recommendations 

address SSQs A and 1-7; CMIN 2.4.1; and RINs 2.4.1, 2.4.3, and 2.4.6 and HBCCP 

recommendations.

Olden and Naiman (2009) argue that manipulating flows from dams to provide natural flow 

regimes (water quantity) only partly addresses maintaining the sustainability of riverine 

ecosystems. The authors cite water-quality factors, especially temperature, as important drivers for 

ecosystem processes such as stream productivity and reproductions, growth, distribution, and 

assemblage of organisms in the system. Cold water pollution is evidenced in Grand Canyon by the 

distribution of coldwater species closer to Glen Canyon Dam and warmwater species in 

downstream reaches. Manipulation of temperature may provide a means for benefiting native 

species and limiting the downstream distribution of rainbow trout to the upper reaches of the river, 

however, this also has the potential of expanding the distribution, abundance, and increasing the 

invasion risk of warmwater nonnative fish, some of which are major predators to native fish in the 

upper Colorado River (Bestgen and others, 2008). Valdez and Speas (2009) predict that warming 

mainstem temperatures could increase the temperature suitability of a greater area of the mainstem 
51

for spawning, incubation, and growth of native species as well as warmwater nonnative species. In 

April 2007, a scientific panel was convened to review Grand Canyon resource status and to make 

recommendations for additional experimentation in a long-term experimental plan (Grand Canyon 

Monitoring and Research Center, 2008). This panel was advised that implementation of a 

temperature control device on Glen Canyon Dam was being seriously considered. The panel, like 

review panels before it (Mueller and others, 1999; Garrett and others, 2003), recognized the 

potential risks of releasing only warmer water from Lake Powell. Therefore, the 2007 panel 

recommended the design, construction, and implementation of a temperature control device on 

Glen Canyon Dam that had the capacity to release both warm and cold water from Lake Powell. 

The ability to release both warm and cold water would likely increase the ability of scientists and 

managers to address risks posed by a variety of nonnative fish, and so would be considered a 

dramatic increase in the capacity for nonnative fish control to benefit native fish (Grand Canyon 

Monitoring and Research Center, 2008). Implementation of a broad range temperature control 

device is recommended and will require careful consideration of the potential benefits of warm 

water to both native and nonnative fish.

Manipulation of flow regimes from dams has been identified as a potentially powerful tool 

for managing native and nonnative fish species. Brown and Ford (2002) determined that flow 

regime was important to the reproductive success of both native and nonnative fish species in a 

regulated river in California. The authors determined that the flow patterns from the previous year 

differentially affected the reproductive success of native and nonnative species and, thus, the 

resulting community in the following winter and spring. Jennings and Philipp (1994) determined 

that during 2 years that were characterized by low, relatively stable flow, longear sunfish (Lepomis 

megalotis) nest failures were attributable to biotic interactions, whereas during a 2-year period with 

more variable flow, most brood losses occurred during floods. The authors concluded that flooding 

led to nest desertion and loss of offspring regardless of nest location. Lukas and Orth (1995)

examined the influences of habitat, temperature, stream discharge, and timing of spawning on the 

nesting success of smallmouth bass in a Virginia stream. High flow ( 10 m3/s) disrupted spawning 

on five occasions and was responsible for most nest failures (85 percent). The authors noted 

increased water velocity at nest sites with increased stream discharge as the most likely cause of 

nest failures. The temporal pattern of stream flow fluctuation appeared to be the most important 

abiotic factor in determining nesting success or failure for smallmouth bass. Simonson and 

Swenson (1990) determined that young smallmouth bass that had recently emerged from nest 

gravel (7 to 9 mm) were displaced both from field nest sites and laboratory flume nest sites at 

velocities of 8 mm/s. Smallmouth bass nests in areas of higher velocities (15 mm/s) failed to 

produce young. However, caution is warranted because these studies did not directly measure the 

fate of displaced young fish. In the Green River, Bestgen and others (2007) linked recruitment 

failure of smallmouth bass in 2004 with captures of newly hatched individuals in drift samples 

during conditions of increased turbidity and flow. In a 10-year study of a California stream, Strange 

and others (1993) determined that fish community structure changed under the influence of storminduced high-flow events that negatively affected fish recruitment. Relative abundance was altered 

as a result of pre-recruitment stream discharges, differentially influencing year-class strength 

among species with contrasting life histories. In all of these studies, knowledge of the specific life 

history associated with spawning of each species was necessary to develop studies to identify the 

effects of flow regimes on recruitment.
52

Modification of the fish community in Grand Canyon has been attempted using flow 

manipulation with varying goals and responses. Authors of the HBCCP summarize the results and 

potential use of floods in Grand Canyon as follows:

Floods have, for some time, been identified as a potential means to disadvantage nonnative 

fishes and thereby advantage native fishes (Meffe 1984). Likewise dam operations could be 

utilized to disadvantage nonnative fishes via artificial floods or other flows from 

displacement due to flooding, stranding, or altering spawning and rearing habitats. And yet,

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. 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-ofyear 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-ofyear rainbow trout recruitment could be very effective.

Full development of targeted flow and temperature manipulations for Grand Canyon will 

require a comprehensive review of native and nonnative life history. Prescribing a flow and 

temperature treatment to disadvantage nonnative fish recruitment to benefit native fish is 

recommended. A temperature control device is recommended to support development of a broad 

range of treatments to benefit native fish. It will be particularly important to continue monitoring 

native and nonnative fish along with implementation of any flow and temperature manipulations to 

document and respond to any species responses to experimental flows. This recommendation 

addresses SSQs A and RINs 2.4.1, 2.4.2, and EIN 2.4.1 and HBCCP recommendations.

In a review of the potential use of pheromones, Sorensen and Stacy (2004) concluded that 

use of pheromone baits to increase trapping efficiency would be an important tool to suppress 

reproductive potential of adult common carp. Sorensen, from the University of Minnesota, is 

developing pheromone attractants specifically for common carp to assist in control efforts. 

Sorensen‘s research represents a collaborative effort with the New South Wales Department of 

Primary Industries, the South Australian Research and Development Institute (SARDI), and the 

Invasive Animals Cooperative Research Centre in Australia. Sorensen presented the results of his 

study at an Annual Invasive Animals Cooperative Research Centre breakthrough lecture series for 

which the University of Canberra issued a press release in June 2007 (Curtis, 2007).

According to the press release, Sorensen‘s research has identified a male-derived 

pheromone that may have ―multiple uses in attracting, diverting, and removing common carp by 

controlling the responses the female common carp has towards males.‖ Sorensen presented the 
53

concept of ―hotspots,‖ locations where common carp spawning occurs en masse, which are 

common to most systems. These hotspots are thought to result from environmental and pheromonal 

cues. This research suggests environmental and pheromonal cues could stimulate common carp to 

migrate and concentrate in a particular area where they could then be physically removed. 

Sorensen expected to have a product available in the near future, and the Invasive Animals 

Cooperative Research Centre could not comment on a product availability timeline (W. Fulton, 

Invasive Animals Cooperative Research Centre, written commun., 2007). Pending authorization for 

widespread use, this product could be used in the future to increase common carp captures in 

localized areas within Grand Canyon. Identification of hot spots and development of capture 

methods to target these areas will be required.

Pheromone attractants have also been documented to attract channel catfish (Timms and 

Kleerkoper, 1972). The authors demonstrate that sexually mature male channel catfish are attracted 

by a pheromone released by ripe females. This was measured by the tendency of male channel 

catfish to move toward and remain within close proximity to a point source release of the female 

pheromone. A female pheromone has also been identified as an attractant to black bullhead 

(Ameiurus melas) (Wallace, 1970 and Kendle, 1970). 

Young and others (2003) observed increases in brook trout captures in hoop nets seeded 

with male brook trout in reproductive condition. Hoop nets were seeded with ripe male and female 

brook trout. Those nets seeded with ripe males resulted in disproportionately higher catch rates of 

ripe male. Nets seeded with ripe female brook trout did not result in catch rate differences. Seeding 

hoopnets with ripe trout may result in increased catch rates of fish in reproductive condition and 

could be applied to mainstem or tributary trout removal in Grand Canyon.

Use of pheromone attractant methods such as placing ripe female fish or ovaries in catfish 

nets could potentially increase capture rates of bullhead species and channel catfish. This method 

should be combined with other bait types on an experimental basis to test the relative effectiveness 

of each bait type or combinations of bait types. This experiment should be conducted in the Little 

Colorado River and the confluence area where channel catfish and bullhead species captures are 

more common. This recommendation addresses SSQs A and 1-7; CMIN 2.4.1; and RINs 2.4.1, 

2.4.3, and 2.4.6 and HBCCP recommendations. (See Channel Catfish and Bullhead Species 

Removal in the Little Colorado River and Confluence Area below).

Telemetry has been used in many aquatic systems to identify spawning areas, feeding areas, 

migration patterns, site fidelity, and environmental factors affecting fish movement (Clements and 

others, 2005; Childs and others, 2008; Humston and others, 2005; Mallen-Cooper and others, 1995; 

Tasmanian Inland Fisheries Service, 2009). In Australia, ―Judas‖ fish, or radio-tagged fish that 

reveal the locations of fish groups by gravitating toward their own species aggregations, are used to 

help understand fish habitat preference and behavior and increase the effectiveness of mechanical 

and chemical control (Lintermans and Raadik, 2003, Diggle and others, 2004; Tasmanian Inland 

Fisheries Service, 2009). Telemetry can also be used to compare and evaluate native and nonnative 

species spatial and temporal overlap (Jackson and others, 2001). 

A sonic-tag study was implemented in Grand Canyon during the 2008 high-flow 

experiment (HFE) to determine the effects of the HFE on rainbow trout movement (Hilwig and 

Makinster, in press). Concern was raised that rainbow trout could displace from Lees Ferry into 

areas unavailable to anglers and important for humpback chub. Ninety-four rainbow trout ranging 

in size from 157 to 409 mm total length (TL) were tagged during the study. Average movement of 

located, tagged rainbow trout was similar for all size classes and both sexes before or after the 
54

HFE. A total of 3 of 94 acoustic tags (3 percent) were detected by a remote receiver located 6 miles 

downstream of Lees Ferry. The greatest documented movement of a tagged trout was more than 

18.1 miles downstream, which occurred before the HFE. The greatest upstream movement of a 

tagged trout was 6.4 miles, which also occurred before the HFE. Individual fish movement was 

highly variable and did not correlate to the occurrence of the HFE, length, or sex. The average 

movement of tagged rainbow trout, which was 305 to 405 mm, tended to be less variable after the 

HFE. The 2008 HFE did not appear to cause displacement below Lees Ferry of the majority of 

tagged rainbow trout. Specific location of individual fish could be accomplished, if the density of 

tags at large was reduced or tagged fish were subsampled. Sonic tags allowed for the determination 

of movement patterns and individual fish locations (habitat identification) of fish larger than 157 

mm in Grand Canyon.

Sonic telemetry should be used in Grand Canyon to identify areas of importance to native 

and nonnative fish, so that efficient control strategies can be developed. Sonic-tagged fish can 

provide information about migration cues, impacts of dam releases or water-quality conditions on 

fish distribution, species overlap, and tributary and other habitat usage. For example, sonic tagging 

common carp in the Little Colorado River may allow scientists to identify aggregations of common 

carp, determine conditions in which aggregations occur, and gain insight into common carp 

behavior. This information would assist scientists in identifying potential impacts of common carp 

on humpback chub and formulating removal strategies. Studies of surgical implantation methods 

and long-term survivorship should be conducted to assist in the evaluation of the results. Surgical 

implantation of sonic tags into adult nonnative fish such as walleye and smallmouth bass captured 

in the Lees Ferry Reach is also recommended. These fish could be tracked to determine the fate of 

nonnative fish and potential spawning locations and activity.

Use of sonic telemetry to identify areas of importance to native and nonnative fish, evaluate 

spatial and temporal movement patterns and track Judas fish is recommended. This 

recommendation addresses SSQs A, 1-7, and 5-6; CMIN 2.4.1; RINs 2.4.1, 2.4.3, and 2.4.5; and 

EIN 2.4.1.

Determining the interactive mechanisms by which nonnative fish affect native fish is 

difficult in a field setting. Laboratory tests are often used to evaluate hypotheses in controlled 

situations. Although laboratory settings do not exactly emulate field conditions, test results can be 

useful in evaluating these mechanisms and devising management strategies to limit potentially 

negative interactions. The GCMRC recommends study of the impact of nonnative fish on juvenile 

humpback chub in an experimental stream. Growth, condition, and mortality of juvenile humpback 

chub can be easily measured in an experimental stream setting. Several nonnative fish species and 

size classes can be tested in combination with various water temperatures to evaluate the conditions 

that pose the greatest risk to juvenile humpback chub. This study should provide insight into how 

juvenile humpback chub survivorship is affected by nonnative fish and temperature in Grand 

Canyon.

Investigation of negative interactions among native and nonnative fish in an experimental 

stream setting is recommended. This recommendation addresses SSQs A, B, and 5-6; CMIN 2.4.1; 

and RINs 2.4.1, 2.4.3, and 2.4.4 and HBCCP recommendations.

The Williams‘ Carp Cage was developed by researchers from the Arthur Rylah Institute for 

Environmental Research and Goulburn Murray Water weir keepers for use in the Murray-Darling 
55

Basin, Australia. Stewart and others (2006), the developers of the trap, describe it as a key tool 

within broader common carp control initiatives and river rehabilitation actions, providing a solid 

low-cost technique for mechanical control efforts. The trap prevents nonnative fish from using 

fishways designed to facilitate native fish passage through weir structures. Researchers observed 

that common carp tended to jump upstream when they were captured in the standard fishway 

monitoring traps. The traps were modified to separate jumping common carp from non-jumping 

native fish. The fishway is a cement-walled vertical canal, approximately 200 m long and 2 m 

wide, and usually operates at 1 m water depth. During the testing, the majority (88 percent; 370 

individuals) of adult (244 to 710 mm) common carp that entered the fishway jumped into the 

confinement area. Since the fishway became operational in 1991, several thousand common carp 

have been trapped and manually removed each year (Mallen-Cooper, 1999). Since 2001, however, 

less than 500 common carp are now removed annually, which corresponds to a more general trend 

of population decline of the species in the mid-Murray River (Nicol and others, 2004). Researchers 

are currently testing a modified version of the trap in wetland areas and free-standing applications 

with mixed results (W. Fulton, Invasive Animals Cooperative Research Centre, written commun., 

2007). 

Application of Williams‘ Carp Cage concept in the Little Colorado River may be possible 

but limited to areas where the river narrows or in areas where common carp are observed in large 

schools. Creative thought and prototype testing will assist in evaluating feasible application and 

value of this method.

In 2003, a collaborative project between the Australian Murray-Darling Basin Commission, 

the Commonwealth Scientific and Industrial Research Organisation‘s Marine Research, and the 

Pest Animal Control Cooperative Research Centre was launched to develop genetic methods for 

common carp control. Researchers have targeted a gene that allows embryos to develop into 

normal female fish. Fish that no longer express this gene, termed the daughterless gene, can only 

produce male offspring. Researchers have successfully produced neomales, or genetic females that 

are functional males, and are now spawning the neomales to determine whether the daughterless 

gene will be inherited. Skewing sex ratios to favor males in conjunction with other management 

practices may allow for widespread common carp reduction. However, this would require 

swamping existing common carp populations with genetically modified daughterless common carp. 

Researchers estimate that a successful daughterless carp approach would require 40 to 50 yr to 

implement because of the long lifespan of common carp and should be used in conjunction with 

other short-term control techniques. Authorization for the widespread release of the carriers is 

currently being perused (Invasive Animals Cooperative Research Centre, 2006).

Koi herpes virus (KHV) is a viral disease that is highly contagious to common carp, causing 

significant morbidity (sickness or disease) and mortality (Hedrick and others, 2000). The virus, 

which attacks gills and other vital organs and often initiates secondary infections, eventually kills

its host. The Washington Animal Disease Diagnostic Laboratory at Washington State University 

determined that KHV was the cause of death for thousands of common carp in Lakes Mohave and 

Havasu in the spring and summer of 2009. Researchers at the Commonwealth Scientific and 

Industrial Research Organisation‘s Livestock Industries‘ Australian Animal Health Laboratory, 
56

along with the Department of Primary Industries Victoria, are investigating KHV as a means of 

controlling common carp. Ongoing research suggests that KHV has a very limited host range, 

infecting only common carp (Commonwealth Scientific and Industrial Research Organisation, 

2006). Because of this host specificity, KHV is being developed as a biological control agent as 

part of a larger pest-fish control program under the Invasive Animals Cooperative Research Centre 

and the Murray-Darling Basin Commission. 

This plandocument advocates hosting an annual workshop for managers, scientists, and 

stakeholders to discuss nonnative fish collections in Grand Canyon, new capture techniques, pilot 

project results, management issues, long-term planning, and priorities. The Upper Colorado River 

Endangered Fish Recovery Program Convening has successfully used annual workshops to share 

information and improve planning activities. Recent nonnative fish workshops were conducted by 

the GCMRC in December 2005, October 2007, and December 2008. Workshop participants should 

include cooperators, agency managers, GCDAMP stakeholders, and topic experts. Information 

reviewed should include annual monitoring results and limitations and changes in distribution and

length frequency (figs. 7 and 8 for examples of historical data and Response Triggers section 

below). Data in figures 7 and 8 represent common carp catches during a variety of projects, 

sampling procedures, and sampling gears and should be interpreted carefully. It is recommended 

emphasized that this gathering should take place annually and serve as the venue for prioritizing 

the recommendations and options presented in this plandocument. Changes in control activities 

should be carefully evaluated with close attention to data from annual monitoring and research 

programs. Changes in priorities will be evaluated before implementation and will be reviewed with 

scientists and managers during annual nonnative fish workshops. The GCDAMP would also review

proposed changes. With repeated implementation, it is anticipated that this annual meeting will 

contribute to the continued evaluation of processes for implementing priority tasks. It is anticipated 

that the Grand Canyon nonnative fish community will always be changing. The species present 

their population sizes, distributions, and spawning effectiveness, among other factors, are most 

likely variable from year to year. An annual nonnative meeting will help scientists and managers 

track these variables, amend work plans accordingly, and respond appropriately.
57
58

Currently, nonnative species detected in Grand Canyon represent only a fraction of the 

community that could establish itself in the Colorado River. Many nonnative species not yet 

established in Grand Canyon have caused population declines and even extinctions in the upper 

Colorado River Basin and other systems (Minckley and Deacon, 1991). The nonnative fish 
59

community established in Grand Canyon does not represent the full potential assemblage of 

nonnative fish that have established and have had major impact on native fish in other areas of the 

Colorado River Basin, including gizzard shad (Dorosoma cepedianum), white sucker (Catostomus 

commersoni), northern pike (Esox lucius), smallmouth bass, and blue tilapia (Oreochromis aurea). 

Preventing new invasions of nonnative species is the least expensive and most effective 

way to control the negative effects of nonnative species when compared to the cost of control 

projects after invasions occur (Leung and others, 2002). Increased public outreach activities, as 

recommended by the Nonnative Fish Control Ad Hoc Committee in 2002, are important to 

successful management of nonnative fish in Grand Canyon (management objective 2.4). Public 

outreach can increase public understanding of the effects of nonnative fish on native fish and the 

justification for nonnative fish control efforts. Public outreach also provides an opportunity to 

inform people about the effects of actions such as illegal stocking and potentially deter such 

practices.

Two nonnative fish projects conducted in Grand Canyon have incorporated public outreach. 

First, informational pamphlets were distributed locally and posted at Lees Ferry as part of the 

mechanical removal project near the Little Colorado River. Project personnel also visited river 

camps in the study area to address concerns and answer questions. During the trout removal project 

in Bright Angel Creek undertaken by GCNP, a wide range of outreach activities were undertaken, 

including (1) posting and distributing informational posters, (2) informing park rangers of project 

details so that they could answer visitor questions, (3) including informational inserts with

backcountry permit packets, (4) participating in the ―Talk to a Ranger‖ program at Phantom Ranch, 

and (5) encouraging visitors to provide volunteer support to weir operation (for example, recording 

data, carrying buckets). Finally, project staff conducted a brown bag lunch program for Grand 

Canyon National Park employees describing the project and initial results. Results have also been 

presented at professional society meetings and submitted to ―Nature Notes,‖ a Grand Canyon 

National Park publication. The U.S. Fish and Wildlife Service also worked with GCNP outreach 

staff to develop Web site materials and updates for interested parties. The outreach effort related to 

trout removal from Bright Angel Creek not only provides a foundation for future efforts to describe

nonnative fish issues in Grand Canyon, but also served to reduce potential negative public 

perceptions of the project. An example of public outreach material associated with the Bright 

Angel Creek weir is provided in appendix B. Development and production of the public outreach 

methods and materials should be coordinated among the GCDAMP Public Outreach Ad Hoc 

Group and professional outreach staff of the National Park Service, Bureau of Reclamation, and 

U.S. Geologic Survey.

Topics recommended for public outreach:

Importance of native fish conservation in Grand Canyon

Negative effects of nonnative species on conservation efforts for native fish

Purpose and description of nonnative fish removal programs

Effects of illegal stocking of nonnative fish, associated fines, and witness reporting information

Several entities conduct scientific fish sampling in Colorado River Ecosystem and its 

watersheds, including National Park Service, Arizona Game and Fish, Utah Division of Wildlife 

Resources, Colorado Division of Wildlife, U.S. Geological Survey, U.S. Fish and Wildlife Service, 

Tribal entities, and other scientists and managers. Often there is little or no immediate exchange of 
60

information among these entities and extended delay before data are error checked and entered into 

a common database. The ability to detect nonnative fish occurrences in a timely manner is 

important to formulating rapid management responses. A formalized reporting system to document 

nonnative species captures or observations is recommended for distribution to all professional 

entities sampling fish in Grand Canyon. This information will be used to augment annual tracking 

of changes in nonnative species abundance and distribution. The existing GCMRC fish database 

will be expanded to accommodate these additional capture data.

Development of a formal nonnative fish capture reporting system is recommended. This 

recommendation addresses CMIN 2.4.1.

Ideally, invasions of new nonnative species in Grand Canyon or increases in abundance and 

distribution of species already present would be detected in a timely manner, so localized reduction 

efforts could be applied to a problem species and area before extensive population growth occurs. 

For example, ideal control efforts would involve detecting the presence of adult nonnative fish 

before they reproduce and targeting adult fish for removal with a capture method that has proven 

effective. This scenario requires frequent monitoring and implementing effective capture methods 

that are immediately available. Because of the limits of current monitoring methods, expansions 

and invasions can go undetected until a nonnative species reach a relatively high abundance, at 

which point removal efforts to offset recruitment and immigration of the nonnative species would 

require additional effort and are likely to be less effective. A monitoring program that could detect 

the presence of all the species and life-history stages that may expand within or invade Grand 

Canyon is infeasible. The success of nonnative species control is closely tied to early detection 

techniques and effective capture methods, neither of which is optimally available at present.

Determining which nonnative fish poses the greatest risk to native fish is complicated by 

the uncertainty about the possible expansion of existing nonnative populations into areas important 

for natives, what nonnative fish species may invade Grand Canyon in the future, and how future 

environmental conditions (for example, drought-induced warming and tributary flooding) may 

benefit nonnative species. The nonnative fish species targeted for removal on an annual basis may 

change in a very short time frame as new sampling information is gathered and threats identified. 

The following recommendationsapproaches were developed to identify and address emerging 

threats and assist scientists in defining triggers to initiate immediate nonnative fish control 

campaigns and strategies to gain insight into efficient removal strategies when none may have been 

proven in Grand Canyon. 

Invasive species populations can expand at exponential upon entry into new systems. 

Exponential expansion can occur after the initial introduction of a few individuals and during range 

expansion of an established invasive species (Kolar and Lodge, 2002). Successful invasion is 

usually characterized by the movement of adult individuals into new areas, followed by a strong 

pulse of recruitment. This pattern shows that detection of both young and adult nonnative species is 

important when evaluating triggers to initiate reduction programs. It is difficult to use catch-rate 

changes associated with long-term monitoring data to define triggers because catch rates can be 

influenced by different factors and it is difficult to extrapolate abundance from them. Information 

to make scientifically credible determinations is limited and, thus, requires the best professional 

judgment to formulate recommendations based on current conditions. Evaluation of multiple 

parameters will be required to assess potential nonnative fish expansion and the need for action on 
61

an individual species basis. Annual nonnative fish management workshops should be the venue for 

evaluating triggers that would initiate nonnative fish control, because during the annual workshop 

scientists will present their most recent findings related to nonnative fish monitoring and research. 

Up-to-date monitoring and research findings should form the basis of discussions regarding 

whether or not to initiate nonnative fish control actions. The following indices are recommended 

for evaluating response triggers, which are keys to effective contingency planning. 

Long-term monitoring protocols are likely adequate to detect large annual changes (that is, 

100 percent) in catch rates of rainbow trout, brown trout, and potentially common carp. 

Furthermore, continued evaluation of multiyear catch rate data associated with all nonnative fish in 

each reach can help to identify and track potential problems. Application of a standardized trigger 

for a focused removal program is difficult because of different relative species abundance in 

reaches. Thus, a proportional criterion for applying a trigger (for example, a 20 percent increase in 

catch rate of a rare species) may capture a nonnative species expansion issue; however, application 

of this same trigger to a locally abundant nonnative species may be misinterpreted (for example, 

when a 20 percent increase is contained within the variance of the catch rate). Thus, close tracking 

of catch rate information from multiple gear types, multiyear samples, and other factors mentioned 

below will be used to evaluate potential nonnative fish expansions on a species-by-species basis.

Investigation of species distribution is a useful tool for evaluating species range expansions, 

especially in relation to warming river temperatures. Monitoring data will provide the baseline 

from which changes in distribution will be evaluated. The degree of overlap with areas important to 

native fish will also be evaluated. Monitoring information should be augmented with catch 

information from other fish-sampling projects. 

Changes in the relative abundance of nonnative fish species will be used to evaluate 

potential expansions of nonnative fish species in each reach. Again, it is difficult to apply a single 

threshold, such as a 20 percent increase in proportion of a species captured, given differences in 

catch rates and abundance. Changes in composition for each species will be evaluated using the 

same spatial designations used to evaluate changes in distribution.

Analysis of changes in length composition over time will provide insight into changes in

population structure in each reach, such as increased juvenile or adult abundance. Changes in 

length composition for each species will be evaluated using the same spatial designations used to 

evaluate changes in distribution. For example, if the electrofishing catch rate of a large-bodied 

nonnative species increases in reach 2, young fish are observed for the first time in this reach, and 

the number of young fish substantially increases in proportion to the total species capture in seining 

samples, a population expansion would be indicated by the data.

Reducing nonnative fish abundance in large river systems can be expensive. The GCMRC 

recommends establishing a nonnative fish control contingency fund dedicated to nonnative fish 
62

control in the event that a new species invades the system or existing populations expand into areas 

important for native fish conservation. This fund should be developed so that ongoing fish 

monitoring and research activities in Grand Canyon are maintained because these activities provide

the basis for evaluating the native and nonnative fish community in Grand Canyon. Therefore, it is 

critical to maintain these functions so that the collected data can be used to determine whether 

nonnative control is needed. 

The costs of nonnative control efforts will vary depending on many factors, including 

species targeted and gear required, the location of the removal, the goals of a specific project, and 

other factors. The rate of immigration into a removal reach and any local reproduction will also 

affect the level of control required. For comparison, the 4-year long effort to reduce rainbow trout 

and other nonnative fish in the Little Colorado River reach of the Colorado River cost 

approximately $2 million. The techniques from that project were re-applied in 2009 at a cost of 

approximately $150,000 for a single, six-pass trip. Current estimates suggest that if rainbow trout 

immigration into the removal reach continues as it did in 2003–06, and population estimates are 

accurate, then two annual removal trips to this reach would be required to maintain the population 

of rainbow trout at 10 to 20 percent of the January 2003 levels. In order to conduct two trips 

comparable to the 2009 effort in any year where nonnative species control is required, it is 

recommended that a nonnative control contingency fund be established with GCDAMP 

contributions of $300,000 annually, with the total not to exceed $900,000 over 3 years. This 

contingency fund should be used as the funding source for controlling any nonnative species in 

Grand Canyon determined to be posing a high risk to humpback chub.

In the event that nonnative fish reduction triggers—to be reviewed annually by the 

scientists and managers participating in the annual nonnative fish workshop proposed by this 

plandocument—are met, immediate reduction efforts should be initiated. However, proven 

reduction methods are not available for many nonnative species in Grand Canyon, which 

necessitates the use of gears with moderate, poor, or unknown capture efficiencies while new 

methods are being evaluated. Combining several capture methods with sonic tracking and targeting 

problem areas with the gears that are most likely to capture target species offers the greatest chance 

for temporary reduction of nonnative species while new, more sustainable methods are being

developed for this program and others around the world.

The following contingency statements address nonnative fish issues that may arise in 

Grand Canyon in the near future and recommended responses to these threats:

If smallmouth bass, green sunfish, or walleye captures in the Lees Ferry area demonstrate a 

population expansion, then an intensive electrofishing, angling, and netting campaign to capture 

and remove these species should be initiated immediately. 

If smallmouth bass, green sunfish, or walleye captures in the Lees Ferry area demonstrate a 

population expansion, then implantation of sonic tags in suitable individuals should be initiated 

immediately, concurrent with the removal efforts cited above, to determine extent of the 

expansion and potential removal strategies.

If smallmouth bass or green sunfish in the Lees Ferry area demonstrate a population expansion, 

then development and implementation of flow manipulations to disadvantage these species 

should be initiated immediately, concurrent with the removal efforts cited above.

If channel catfish or black bullhead captures in the Little Colorado River, and/or the mainstem 

Colorado River near the mouth of the Little Colorado River, demonstrate a population 
63

expansion, then an intensive netting and angling campaign to capture and remove these species 

should be initiated immediately. This effort should be weighed carefully, along with the benefit 

and risk of releasing PIT- or sonic-tagged individuals.

If channel catfish or black bullhead captures in the Little Colorado River or the mainstem 

continue to increase, then efforts to implant sonic tags in suitable individuals should be initiated 

immediately to determine extent of the expansion and potential removal strategies, concurrent 

with the removal efforts cited above.

If rainbow trout attain abundances greater than 20 percent of January 2003 abundance 

estimates, then mechanical removal should be reinitiated to reduce the population size to 

approximately 10% of the estimated January 2003 abundance.

The following recommendations and options are listed in priority order by category.

Expand current mainstem monitoring, focusing initially on areas in proximity to humpback 

chub aggregations and tributary inflows

Implement an early detection protocol and nonnative fish monitoring in Lees Ferry 

Implement long-term monitoring program in tributaries and confluence areas of the Grand 

Canyon

Maintain trout abundance in the Little Colorado River reach at approximately 10 to 20 percent 

of January 2003 rainbow trout abundance (approximately 600 to 1,200 rainbow trout)

Continue to remove trout in Shinumo Creek using backpack electrofishing in combination with 

other methods such as weirs and angling to support translocation efforts

Continue to remove trout in Bright Angel Creek using a weir, backpack electrofishing and other 

methods

Pilot test catfish nets and stink cheese to remove and monitor channel catfish and bullhead 

species in the Little Colorado River and the confluence area

Undertake chemical renovation and barrier construction in tributary streams identified as 

sources of nonnative fish into Grand Canyon

Develop a model to identify the nonnative species posing the greatest risk to humpback chub

Identify sources of juvenile and adult nonnative fish into the mainstem such as recruitment 

locations, tributary inflows, dam passage, and illegal stocking

Develop occupancy model for improvement of long-term nonnative fish monitoring, evaluation 

of nonnative fish population expansion or contraction, and development of early detection 

protocols
64

Undertake a small-bodied nonnative fish and YOY capture and monitoring study using slowshocking techniques (nearshore ecology) throughout the mainstem

Continue efforts to develop remote PIT tag detection technology for application to nonnative 

fish and tributary streams

Use large mesh gill nets to target common carp in the Little Colorado River and the confluence 

area

Develop flow manipulations of both water quantity (experimental flows) and temperature (a 

temperature control device) to disadvantage nonnative species while benefiting natives

Use pheromone and sensory attractants to increase capture efficiencies for channel catfish and 

bullhead species

Initiate sonic telemetry studies for native and nonnative fish to compare and identify spatial and 

temporal movement patterns, tributary use, and spawning areas

Undertake experimental stream tests to investigate mechanisms by which nonnative fish 

negatively affect juvenile humpback chub

Modify the Williams‘ Carp Cage to capture common carp in tributaries

Consider stocking daughterless carp and introducing infectious agents that target nonnative fish 

species in the future for long-term nonnative fish control

Conduct an annual nonnative fish workshop with cooperators and other nonnative fish experts 

to review current information and to help prioritize efforts

Undertake public outreach activities specifically for nonnative fish management issues with 

attention to preventative measures such as deterring illegal stocking

Develop a formalized reporting procedure for nonnative fish captured and observed by 

professional entities performing sampling within Grand Canyon

Define agency roles and develop rapid response plans to address nonnative fish expansions or 

new invasions

Evaluate response triggers to initiate control measures of nonnative fish abundance from 

changes in catch rate, distribution, species composition, and length frequencies (reviewed at 

annual nonnative meeting)

Apply current capture methods used in Grand Canyon while more effective methods are being 

developed

Implant sonic tags in nonnative fish to help evaluate dispersal, potential spawning activities, 

and other factors

Establish a nonnative fish contingency fund for ongoing monitoring and research activities
65

Based on the guidance provided by the GCDAMP, the overarching intention of nonnative 

fish management planning is to reduce the threats posed to native fishes by nonnative fish species. 

A multifaceted plan is required to effectively reduce the varied and multiple threats posed to Grand 

Canyon native fish by the nonnative fish. Table 4 identifies a strategic approach to address 

nonnative fish issues in Grand Canyon and the recommendations and options presented by this 

document for pursuing these strategies.
66

Develop a risk assessment to identify the nonnative fish 

species that poses the greatest risk to native species. This 

includes identification of particular size classes of 

nonnative fish that pose the greatest threat to native fish 

populations. Ideally, this threat assessment would identify 

the nonnative fish posing the greatest risk in space and time 

to native fish. 

1. Develop risk assessment

2. Continue testing of remote PIT-tag reader

3. Implement sonic telemetry

4. Improve monitoring

5. Continue experimental stream study

Identify sources of nonnative fish into Grand Canyon, their 

movement patterns, and areas important for their spawning 

and recruitment. These areas could then be targets for 

removal efforts.

1. Improve monitoring

2. Initiate tributary monitoring

3. Research sources of nonnative fish

4. Continue testing remote PIT-tag reader

5. Implement sonic telemetry

Prevent new nonnative fish invasions into Grand Canyon 

from illegal stocking or sources such as tributaries and 

Lakes Mead or Powell.

See related recommendationoptions above and:

1. Prevent nonnative fish invasions

2. Improve public education and outreach

3. Conduct annual workshop

4. Develop standard reporting procedures

Apply localized control strategies in areas important for 

native fish that would likely be most feasible and efficient

for nonnative fish control. This would require the 

development of effective capture methods that would 

reduce target nonnative fish populations in localized 

applications. Other control could include systemwide 

manipulations through dam operations.

1. Continue mechanical removal

2. Initiate removal in tributaries

3. Initiate catfish and bullhead removal in 

Little Colorado River

4. Undertake chemical renovation and 

barrier construction

5. Investigate carp netting

6. Develop dam release strategy to 

disadvantage nonnative fish

7. Explore daughterless technology for 

future use

8. Investigate future use of infectious agents

Improve monitoring programs to identify changes in native 

and nonnative fish populations of concern and multiple life 

history stages within those populations. Monitoring data 

should allow scientists adequate detection of changes in 

abundance and distribution of a species. This change can 

then be related to the impacts of management activities or 

other factors that may contribute to population change.

1. Improve monitoring

2. Develop occupancy models

3. Continue testing of remote PIT-tag 

detectors

4. Investigate carp netting

5. Implement sonic telemetry

6. Conduct annual workshop

7. Develop contingency plans

Develop effective detection programs to identify new 

invading nonnative fish. Ideally, detection of new invaders 

would be timely to allow for an effective response from 

managers and cooperating agencies before the invading 

population reproduces in or invades the mainstem Colorado 

river where control efforts may be less effective.

1. Improve monitoring

2. Initiate tributary monitoring

3. Research sources of nonnative fish 

4. Develop occupancy models

5. Develop contingency plans

Use best professional judgment and consensus in the 

absence of definitive answers to determine nonnative fish 

control implementation strategies. 

1. Improve monitoring

2. Develop risk assessment 

3. Conduct annual workshop

Develop Grand Canyon contingency and response plans for 

management agencies to implement cooperative efforts in 

addressing urgent nonnative fish expansions or invasions to 

protect native fish. 

1. Develop contingency plans

2. Improve monitoring
67

Develop contingency fund for emergency control 

responses to nonnative fish issues while protecting funding 

for monitoring programs. Monitoring is important for 

evaluating the effects of emergency control responses.

1. Develop contingency plans

2. Improve monitoring

The range of strategies and actions presented above will take time to implement. An 

assessment of available data related to nonnative fish in Grand Canyon and subsequent 

identification of information gaps will assist in the development of planning and research 

strategies. Filling data gaps that are identified will also take time, which forces scientists and 

managers to make decisions in the absence of all possible information. The approach described 

above attempts to balance the recommendations made for research needs with the application of 

control options and the improvement of monitoring programs. However, research and monitoring 

improvement recommendations outnumber control recommendationoptions, a balance that 

accurately reflects the current state of knowledge regarding nonnative fish in Grand Canyon. This 

situation may force managers to make decisions based on the best available information, which 

may not resolve critical nonnative fish management questions. RecommendationOptions for 

nonnative fish management approaches and priorities prioritization of options may will change

over time as new information is evaluated from annual nonnative fish workshops, literature 

reviews, continued evaluation of monitoring needs and results, and development of new capture 

methods. This approach is consistent with the general philosophy of adaptive management of 

increasing knowledge while simultaneously attempting to minimize risk to native fish.

Nonnative fish management in Grand Canyon is complex and falls under the jurisdiction of 

many State, Tribal, and Federal agencies (See Regulatory Authority Section above). Land 

ownership within the Grand Canyon watershed is also varied, including lands managed by State, 

Tribal, and Federal entities as well as private landowners, demonstrating the complexity of 

managing sources of nonnative fish into Grand Canyon (fig. 7). Because of this complexity, 

management of nonnative fish and their sources in Grand Canyon and the watershed will require 

coordination and cooperation of resource and land management agencies, the Tribes and scientists.
68

There are long-standing concerns by Native American stakeholders about conducting 

nonnative fish control in culturally sensitive areas of the Grand Canyon. The Tribes advocate for 

collaboration with management agencies and scientists and request the involvement of tribal people 

early in the stages of nonnative fish control planning so they are actively involved in forming 

management questions and plans. The Tribes request that genuine consideration of cultural values 

and interests be incorporated into designing and carrying out research and management activities of 

the GCDAMP. The Tribes believe true collaboration should occur throughout project planning, 

execution, analysis, and dissemination of results and should actively involve tribal members such 

as students, elders, and others interested to consider culturally-sensitive perspectives of the Tribal 

members. This Tribes believe this communication would broaden the perspective of the Grand 

Canyon ecosystem beyond that of Western science (K. Dongoske, Pueblo of Zuni, pers. commun., 

2010). 

Communication with Tribal should occur in accordance with Secretarial Order 3206 (05 

June 1997), entitled ―American Indian Tribal Rights, Federal-Tribal Trust Responsibilities, the 

Endangered Species Act, and Section 106 of the National Historic Preservation Act. Specifically, 

Principles 1 and 4 of SO 3206 direct the Department of Interior to work directly with Indian Tribes 
69

on a government-to-government basis to promote healthy ecosystems and to be sensitive to Indian 

culture, religion, and spirituality. Additionally, Executive Order 13007 states that federal agencies 

shall accommodate access to and ceremonial use of Indian sacred sites by Indian religious 

practitioners and that the federal agency shall avoid adversely affecting the physical integrity of 

such sacred sites (Pueblo of Zuni, 2009).

The recommendations and options contained within this document bridge the roles of both 

science and management. Recommendations relating to science generally include the development 

of nonnative fish monitoring programs to track progress in achieving GCDAMP goals, researching 

information needs to develop nonnative fish control strategies and risk assessments, and testing 

nonnative fish capture techniques. Management related recommendationoptions include tributary 

renovations and barrier construction, development of public outreach products, consensus 

regarding agency roles in the development of contingency and response plans, and long-term 

management and removal of nonnative fish using prescriptions developed and tested through the 

scientific process. Each component of this plandocument, both science and management related, 

are vital for the successful development and implementation of nonnative fish control strategies in 

Grand Canyon. 

Better integration of the nonnative fish research and monitoring components with the 

implementation and prioritization of nonnative fish control projects by the management agencies is 

necessary. The GCMRC recommends that a nonnative fish workshop be conducted annually with 

scientists, managers, and other outside experts, including scientists from the upper Colorado River 

Basin to discuss implementation of nonnative fish management planning. An annual workshop 

would allow scientists to discuss their most recent monitoring and research results, continue to 

identify information gaps, and develop and prioritize recommendations and options for nonnative 

fish control needsin Grand Canyon. With this information, managers could then prioritize control 

projects and develop implementation strategies to satisfy GCDAMP and management agency 

missions, goals, and objectives for nonnative fish management in Grand Canyon. 

The recommendationoptions presented by this plandocument exceed the budgetary limits of 

the GCDAMP. Therefore, scientists and managers must prioritize recommendationoptions for 

nonnative fish control planning. Information gaps exist in the knowledge of nonnative fish 

parameters in Grand Canyon that make prioritizing recommendationoptions difficult. The 

prioritization of recommendationoptions presented here and during previous nonnative fish 

workshops has been criticized because of a lack of objective prioritization criteria. Prioritization 

methods described below, however, contain evaluation and prioritization criteria that are based on 

subjective opinions of experts. In the absence of definitive answers to basic questions regarding the 

impact of nonnative fish on native fish that would directly impact prioritization criteria, scientists 

and managers are forced to use their best professional judgment in deciding how best to prioritize 

nonnative fish control planning activities. 

Prioritizing options and recommendationspotential solutions formulated among a diverse 

group of stakeholders in a data-poor situation had been approached using various methods. One 

example of developing consensus is called the Delphi method (Dalkey and Helmer 1963). This 

method employs an iterative process where criteria are ranked or unknown biological parameters 

are estimated by polling experts who remain anonymous to each other. This method allows 

respondents to research their answers, consider the responses of other anonymous participants, and 
70

revise their opinions. This method assists in reducing the spontaneity of responses in face-to-face 

discussions and allows for controlled feedback, thereby generating more accurate responses 

(Dalkey 1969; Clark and others 2006). Hess and King (2002) used the Delphi method to identify 

focal species that were used to develop open space management plans to benefit wildlife. Barrett 

(2009) used the Delphi method to query experts on life-history ratios for the Devil‘s Hole pupfish 

(Cyprinodon diabolis) where such values were not available. Average parameter values developed 

by respondents were then incorporated into a population viability model. The author stresses the 

notion that the survey results assist in decisionmaking in the absence of empirical information, 

however, the pursuit of information must continue. The criteria used in each survey should be 

carefully selected to address the required decisions. Another example is the Upper Colorado River

Endangered Fish Recovery Program Nonnative Fish Sub-Committee use of a ranking method for 

prioritizing nonnative fish related tasks (See appendix C, included with permission of T. Chart, 

U.S. Fish and Wildlife Service). This method closely patterns that of the Yampa River Strategy 

(Chart and others, 2008) by using numerical ranking (0 to 5) of criteria based on subjective opinion 

of scientists and managers involved in the program. The first step was to consolidate a list of all 

the recommendations program participants developed related to nonnative fish management. The 

recommendations were grouped into categories of (1) prevention, (2) research, (3) mechanical 

removal, and (4) policy. The list within each category was then ranked based on (1) technical 

feasibility, (2) time to implement, (3) cost, and (4) effectiveness. Project ranks were placed in a 

bivariate chart based on cost effectiveness and ease of implementation where projects fell into four 

categories: (1) difficult but big pay off = medium priority, (2) easy and cost effective = high 

priority, (3) easy but questionable outcome = medium priority, and (4) difficult and questionable 

outcome = low priority. Methods similar to these examples could be used by the GCDAMP to 

define priority tasks and assist in the development of nonnative fish management and research 

implementation strategies. Adoption of a particular prioritization process should be discussed 

among scientists and managers during the annual nonnative fish workshop.

The formulation of desired future outcomes by the GCDAMP could assist scientists and 

managers in developing and prioritizing nonnative fish control in Grand Canyon. Development of 

well-defined conditions that are agreed upon by the GCDAMP stakeholders, including 

management agencies, will then assist with developing goals for nonnative fish control. This 

clarification will assist in the identification of information needs and the development of specific 

management approaches for managers and scientists to work together toward achieving desired 

future conditions.

Developing a risk assessment and improving nonnative fish monitoring information in 

Grand Canyon are two of the top priorities that emerged as the result of discussions among 

nonnative fish workshop participants and reviewers of this document. As the science provider to 

GCDAMP, the GCMRC and cooperators will implement several monitoring and research 

recommendations presented by this document to address these priorities as well as others in FY 

2010 and 2011. Implementation of these projects is consistent with the FY2010–11 budget and 

work plan approved by AMWG in August 13, 2009 (table 5), and subsequently approved by 

Secretary of the Interior Salazar in November 2009. Monitoring projects to be conducted in FY 

2010 and 2011 include (1) monitoring nonnative fish near humpback chub aggregations and 

tributary inflow areas and (2) developing early detection protocols for nonnative fish in the Lees 
71

Ferry reach. Nonnative fish research projects to be conducted in 2010 and 2011 include (1) 

developing a nonnative fish risk assessment, (2) researching sources of nonnatives into the Grand 

Canyon and potential control options, (3) evaluating the utility of an occupancy model for 

monitoring rare nonnative fish species, (4) evaluating small-bodied fish monitoring techniques 

using slow shocking, (5) investigating the feasibility of using sonic tags to evaluate native and 

nonnative fish habitat overlap, and (6) continuing evaluation of remote PIT-tag detectors for use in 

determining native and nonnative fish movement patterns in the Little Colorado River. 

With finding form the GCDAMP, the GCMRC and Arizona Game and Fish Department are 

currently scheduled to continue the mechanical trout removal project near the Little Colorado River 

confluence area in FY 2010 and 2011 (table 5). The techniques used to remove trout have been 

researched and developed through the scientific process. As part of this project, abundance of 

native and nonnative fish is closely monitored to evaluate the impacts of removal or other factors 

on fish abundance. Evaluating the effect of removing trout on local trout abundance has been 

complicated by other factors such as warm water temperatures and food base effects. However, 

scientists believe an efficient method to capture trout has been developed for agencies to apply to 

trout management in Grand Canyon. 

Implementation of other control recommendationoptions will require agreement among 

management agencies regarding their roles and responsibilities in achieving the goals of the 

GCDAMP as well as the resource management goals of each agency. Goals for nonnative fish 

management will require coordination of management agencies and integration of their respective 

management objectives. Also, agreement among stakeholders regarding the terms ―management 

action‖ and ―experiment‖ will be required for effective planning for nonnative fish control actions. 

For example, the mechanical trout removal project is still considered to be experimental under the 

auspices of the GCDAMP, however, there is disagreement among stakeholders as to a 

programmatic definition of an experimental project versus a management action. Defining 

experimental projects and management actions will further assist management agencies in 

clarifying their roles and responsibilities for nonnative species management in Grand Canyon. This 

will assist GCDAMP stakeholders in implementing present and future nonnative fish control needs. 

(See Aug 13, 2009 AMWG motion for Science Advisors to survey other adaptive management 

programs to define research versus management actions.)

In order to respond rapidly and effectively to an invasion of nonnative species, actions 

should be anticipated and consensus reached on as many response details as possible before the

discovery of the invasion or population expansion. When a response is needed, consensus 

regarding actions, funding sources, and agency responsibilities will result in a rapid and more 

effective response. Currently, the GCDAMP does not have a rapid response plan in place for 

invasions or expansion of nonnative aquatic species. Development of a rapid response plan by the 

GCDAMP (See appendix D) may assist in managing the complexity of nonnative fish control and 

planning in Grand Canyon.

The Washington State Aquatic Nuisance Species Committee (2005, See appendix D) 

drafted an early detection and rapid response plan for aquatic invaders in the Columbia River Basin 

involving fourteen Federal, State, Tribal, and private entities. The plan for the Columbia River 

basin provides many pre-determined management agency responses and establishes a decision

making infrastructure designed to facilitate rapid resolution of issues. The response plan contains a 
72

number of objectives and related tasks and identifies remaining institutional and legislative gaps 

that need to be addressed. Objectives in this plan include (1) ensure early reporting of new 

invasions, (2) ensure new species identification and risk assessments, (3) define decisionmaking 

responsibility and response protocols, (4) establish and maintain capacity to act, and (5) incorporate 

adaptive management in plan implementation. The goal of maintaining the capacity to act includes 

(1) development of a response fund; (2) identification and elimination of barriers to response such 

as indecision, funding, and logistical issues; and (3) develop and conduct training for rapid 

responders. Also included in this document is an appendix summarizing Federal, State, and Tribal 

policy and laws pertaining to invasive species. The approach taken by the Washington committee 

has been used as a template for the development of many other rapid response plans in other 

programs and also provided guidance for this document. 

Development of a rapid response plan for nonnative aquatic species by members of the 

GCDAMP would assist in defining agency roles and responsibilities and increase the likelihood of 

successful control of the expansion or invasion of nonnative species in Grand Canyon. 

Estimating project costs is difficult because it is not possible to determine which nonnative 

species may impose the greatest risk to natives, when and where these effects will occur, and how 

to reduce them. Prioritization of projects given limited funding is also difficult because of the 

unknown conditions indicated above. The GCMRC will implement the monitoring and research 

components of this plandocument in FY 2010 and 2011. Cost estimates for these components have 

been included in the table 5. Costs for control projects will be more accurately developed as agency 

roles and responsibilities are defined and control projects are prioritized in the near future. The 

features of a contingency plan and the associated costs will be determined by the effectiveness of 

available reduction methods and the extent of the area to be treated. Cost estimates for higher 

priority projects are more certain than lower priority.

In 2009, the cost of one trip to mechanically remove rainbow trout and other nonnative fish 

from the mainstem Colorado River in the vicinity of the mouth of the Little Colorado River is 

approximately $150,000. This amount includes two nights of sampling in a control reach upstream

of the removal reach to estimate the nonnative fish population. Following the control reach 

sampling, six passes of the removal reach are conducted using boat-mounted electrofishing. Other 

control efforts may differ as the result of many factors, including target species, gear types, 

location, time required, other equipment required, and other factors. Therefore, the 2009 

mechanical removal project cost may not accurately represent the costs of all possible control 

efforts, but it does provide a known starting point for estimating possible future efforts.
73

Expanding current mainstem 

nonnative fish monitoring 

protocols

BIO 2.M4.10-11. Monitoring 

Mainstem Fishes $632,461 $798,930

Implementing early detection 

protocol and nonnative fish 

monitoring in Lees Ferry

BIO 4.M2.10-11. Monitoring 

Lees Ferry Fishes $175,737 $182,819

Developing a model to identify 

the nonnative species posing 

the greatest risk to humpback 

chub

BIO 2.R17.10-11. Nonnative 

Control Plan Science Support

$78,057 $138,599

Identifying sources of juvenile 

and adult nonnative fish into 

the mainstem such as 

recruitment locations, tributary 

inflows, dam passage, and 

illegal stocking

Developing occupancy 

modeling for improvement of 

long-term nonnative fish 

monitoring, evaluation of 

nonnative fish population 

expansion or contraction, and 

development of early detection 

protocols

Testing carp capture methods 

using large mesh nets

Developing risk assessment and 

evaluation of occupancy model

Some modeling also conducted 

in: Plan 12.P1.10-11. Identify 

Critical Ecosystem Interactions 

and Data Gaps

$239,986 $148,945

Conducting a small-bodied 

nonnative fish and YOY 

capture and monitoring study 

using slow-shocking techniques 

(nearshore ecology) throughout 

the mainstem BIO 2.R15.10-11. Nearshore 

Ecology/Fall Steady Flows

$552,825 $556,911
74

Conducting sonic telemetry 

studies for native and nonnative 

fish to compare and identify 

spatial and temporal movement 

patterns, tributary use, and 

spawning areas

Maintaining trout abundance in 

the Little Colorado River 

confluence area at 

approximately 20 percent of 

January 2003 rainbow trout 

abundance

BIO 2.R16.10-11. Mainstem 

Nonnative Fish Control $246,966

$ 68,842

$309,251

Continuing removal of trout in 

Shinumo Creek using backpack 

electrofishing in combination 

with other methods such as 

weirs and angling to support 

translocation efforts

Not in GCMRC work plan, but 

has been conducted by NPS, 

AZGFD, GCWC in conjunction 

with HBC translocation to 

Shinumo

NA NA

Conducting an annual 

nonnative fish workshop with 

cooperators and other nonnative 

fish experts to review current 

information and to help 

prioritize efforts BIO 2.R17.10-11. Nonnative 

Control Plan Science Support

$78,057 $138,599

Developing a formalized 

reporting procedure for 

nonnative fish captured and 

observed by professional 

entities performing sampling 

within Grand Canyon

Defining agency roles and 

developing rapid response plans 

to nonnative fish expansions or 

new invasions BIO 2.R17.10-11. Nonnative 

Control Plan Science Support 

(discussed at annual nonnative 

meeting)

Evaluating response triggers to $78,057 $138,599

initiate control measures of 

nonnative fish abundance from 

changes in catch rate, 

distribution, species 

composition, and length 

frequencies (reviewed at annual 

nonnative meeting)

Applying current capture 

methods used in Grand Canyon 

while more effective methods 

are being developed

BIO 2.R16.10-11. Mainstem 

Nonnative Fish Control $246,966

$ 68,842

$309,251

Implanting sonic tags in 

nonnative fish to help evaluate 

dispersal, potential spawning 

activities, and other factors

BIO 2.R15.10-11. Nearshore 

Ecology/Fall Steady Flows 

(further investigating sonic 

tags)

$552,825 $556,911
75

Establishing a nonnative fish 

contingency fund for ongoing 

monitoring and research 

activities

Described in Plan and being 

discussed with AMP 

committees

NA NA

Ackerman, M.W., 2007, 2006 Native fish monitoring activities in the Colorado River, Grand 

Canyon, Cooperative Agreement 04WRAG0011: report to Grand Canyon Monitoring and 

Research Center, Flagstaff, Ariz., 79 p.

Allan, N.L., 1993, Distribution and abundance of fishes in Shinumo Creek in the Grand Canyon: 

Tucson, Ariz., University of Arizona, M.S. Thesis.

Barrett, P.J., 2009, Estimating Devils Hole pupfish lifestage ratios using the Delphi method: 

Fisheries, v. 34, p. 73–79.

Bestgen, K.R., Zelasko, K.A. and Wilcox, C.T., 2007, Non-native fish removal in the Green River, 

Lodore and Whirlpool canyons, 2002-2006, and fish community response to altered flow and 

temperature regimes, and non-native fish expansion. Final Report to Colorado River Recovery 

Implementation Program, Project Number 115, Larval Fish Laboratory Contribution 149, March 

2007.

Bestgen, K.R., Zelasko, K.A., Wilcox, C.T., Chart, T.C. and Compton, R.I., 2008, Natural flows, 

invasive fishes, and native fish conservation in the Green River downstream of Flaming Gorge 

Dam, 1962 to present. Abstract in Colorado River Basin Science and Resource Management 

Symposium, Scottsdale, AZ, November 18-20, 2008. 

Brown, L.R., and Ford, T., 2002, Effects of flow on the fish communities of a regulated California 

river: implications for managing native fishes: River Research Applications, v. 18, no. 4, p. 

331 342.

Buktenica, M.W., Mahoney, B.D., Girdner, S.F., and Larson, G.L., 2001, Response of a resident 

bull trout population to nine years of brook trout removal, Crater Lake National Park, OR: in D. 

Schill, S. Moore, P. Byorth, and B. Hamre, eds., Wild Trout VII Symposium: Washington, DC, 

Trout Unlimited, p. 127 132. 

Cada, G.F., 2001, The development of advanced hydroelectric turbines to improve fish passage 

survival: Fisheries, v. 26, no. 9, p. 14 23.

Chart, T., Nesler, T., Speas, D., Trammell, M., and Valdez, R., 2008, Yampa River Nonnative Fish 

Control Strategy: Report to Upper Colorado River Endangered Fish Recovery Program, June 30, 

2008.

Chu, C., Mandrak, N.E., and Minns, C.K., 2005, Potential impacts of climate change on the 

distributions of several common and rare freshwater fishes in Canada, Diversity and 

Distributions, 11, 299-310.

Clark, B.C., 2008, 2008 Little Colorado River, Lower 1200 meter Fish Monitoring Trip Report 

(LC20080411) April 11 – May 5, 2008: Cooperative Agreement 07WRAG0010, report to Grand 

Canyon Monitoring and Research Center, September 2008.

Clark, K.E., Applegate, J.E., Niles, L.J. and Dobkin, D.S., 2006, An objective means of species 

status assessment: adapting the Delphi approach: Wildlife Society Bulletin, v. 34, p. 419-425.
76

Clements, S., Jepsena, D., Karnowskia, M., and Schreck, C.B., 2005, Optimization of an acoustic 

telemetry array for detecting transmitter-implanted fish: North American Journal of Fisheries 

Management, v. 25, no. 2, p. 429 436.

Childs, A.R., Cowley, P.D., Næsje, T.F., Bootha, A.J., Potts, W.M., Thorstad, E.B., and Økland, F., 

2008, Do environmental factors influence the movement of estuarine fish? A case study using 

acoustic telemetry: Estuarine, Coastal and Shelf Science, v. 78, no. 1, p. 227 236. 

Coggins, L.G., Jr., 2008, Active adaptive management for native fish conservation in the Grand 

Canyon—implementation and evaluation: Gainesville, University of Florida, Ph.D. dissertation.

Coggins, L.G., Pine, W.E., III, Walters, C.J., and Martell, S.J.D., 2006, Age-structured markrecapture analysis: a virtual-population-analysis-based model for analyzing age-structured 

capture-recapture data: North American Journal of Fisheries Management, v. 26, p. 201 205.

Coggins, L.G., Jr., Yard, M.D., Gwinn, D., and Nelson, C., 2007, Mechanical removal of nonnative 

fishes from the Colorado River within Grand Canyon: Presentation at the 137th annual meeting 

of the American Fisheries Society, San Francisco, Calif.

Coggins, L.G., Jr., and Walters, C.J., 2009, Abundance trends and status of the Little Colorado 

River population of humpback chub; an update considering data from 1989-2008: U.S. 

Geological Survey Open-File Report 2009-1075, 18 p.

Connolly, P.C., Jesorek, I.G., and Martens, K.D., 2008, Measuring the performance of two 

stationary interrogation systems for detecting downstream and upstream movement of PIT-tagged 

salmonids: North American Journal of Fisheries Management, v. 28, p. 402 417.

Converse, Y.K., Hawkins, C.P., and Valdez, R.A., 1998, Habitat relationships of subadult 

humpback chub in the Colorado River through Grand Canyon: spatial variability and 

implications of flow regulation: Regulated Rivers, v. 14, no. 3, p. 267 284.

Commonwealth Scientific and Industrial Research Organisation, 2006, Researchers identify a 

likely carp control: in ECOS Magazine, Towards a Sustainable Future, Issue 132, Aug. Sept. 

2006, Commonwealth Scientific and Industrial Research Organisation, Victoria, Australia.

Curtis, J., 2007, Carp control breakthrough under scientists‘ noses: Canberra, Australia University 

of Canberra press release, June 2007, 

http://www.canberra.edu.au/monitor/articles/new/20070619_carp, accessed August 4, 2008.

Dalkey, N., 1969, An experimental study of group opinion: Futures, v. I, p. 406-426.

Dalkey, N., and Helmer, O., 1963, An experimental application of the Delphi method to the use of 

experts: Management Science, v. 9, p. 458-467.

Davis, J. E. and Furr, D.W., 2008, Nonnative species monitoring and control in the Upper San Juan 

River, New Mexico in 2007. Final Report submitted to the San Juan River Recovery 

Implementation Program Biological Committee, June 5, 2008.

Diggle, J., Day, J., and Bax, N., 2004, Eradicating European carp from Tasmania and implications 

for national European carp eradication: Inland Fisheries Service, Hobart, TAS, Australia, project 

no. 2000/182.

Dudley, R.K., and Matter,W.J., 2000, Effects of small green sunfish (Lepomis cyanellus) on 

recruitment of Gila chub (Gila intermedia) in Sabino Creek, Arizona: Southwestern Naturalist, 

v. 45, p. 24-29.
77

Dufour, E., Patterson, W.P., Hook, T.O., and Rutherford, E.S., 2003, Application of stable isotope 

geochemistry for reconstructing thermal history and natal origins of Lake Michigan alewife: 

2003 Geological Society of America Annual Meeting, Seattle, Wash., November 2–5, 2003.

Eaton, J.G. and Scheller, R.M., 1996, Effects of climate warming on fish thermal habitat in streams 

of the United States, Limnology and Oceanography, Vol. 41, No. 5, Freshwater Ecosystems and 

Climate Change in North America, pp. 1109-1115.Elverud, D.S., 2008, Nonnative Control in the 

Lower San Juan River 2007, Interim Progress Report for the San Juan River Recovery 

Implementation Program. Final Report, June 1, 2008.

Fairley, H., ed., 2005, Core monitoring plan for the Glen Canyon Dam Adaptive Management

Program, Draft 4, Grand Canyon Monitoring and Research Center in collaboration with the core 

monitoring team ad hoc group of the Technical Work Group, April 2005.

Feyrer, F., Hobbs, J., Baerwald, M., Sommer, T., Yin, Q., Clark, K., May, B., and Bennett W., 

2007, Otolith microchemistry provides information complementary to microsatellite DNA for a 

migratory fish: Transactions of the American Fisheries Society, v. 136, p. 469 476.

Francis, R.C., Hixon, M.A., Clarke, M.E., Murawski, S.A., and Ralston, S., 2007, Fisheries 

management: ten commandments for ecosystem-based fisheries scientists: Fisheries, v. 32, no. 5, 

p. 217 233.

Garrett, L.D., Baron, J., Dale, V., Gunderson, L.H., Howard, A., Hulse, D., Kitchell, J., Loomis, J., 

Palmer, M., Parker, R., Robertson, D., Schwartz, D., and Watkins, J., 2003, Evaluating a Glen 

Canyon Dam temperature control device to enhance native fish habitat in the Colorado River: a 

risk assessment by Adaptive Management Program science advisors: prepared for the Glen 

Canyon Dam Adaptive Management Program and the Grand Canyon Monitoring and Research 

Center, Flagstaff, Ariz.

Gerrodette, T., 1987, A power analysis for detecting trends: Ecology, v. 68, p. 1364 1372.

Gilligan, D., Hartwell, D., and McGregor, C., 2008, Identification of  ̳hot-spots‘ of carp 

reproduction in the Murray-Darling Basin in Saunders, G and Lane, C (eds), Proceedings of the 

14th Australasian Vertebrate Pest Conference. Darwin, Northern Territory Australia, June. 

Gloss, S.P. and Coggins, L.G., Jr., 2005, Fishes of Grand Canyon, in Gloss, S.P., Lovich, J.E., and 

Melis, T.S., eds., The state of the Colorado River ecosystem in Grand Canyon: U.S. Geological 

Survey Circular 1282, p. 33-56.

Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., 2005, The state of the Colorado River ecosystem in 

Grand Canyon: U.S. Geological Survey Circular 1282, 220 p.

Grand Canyon Monitoring and Research Center, 2007a, draft report, MRP revisions to address the 

TWG minority report: Flagstaff, Ariz., June 12, 2007.

Grand Canyon Monitoring and Research Center, 2007b, Science plan for potential 2007 

beach/habitat-building flows experiment: draft report dated February 2, 2007. 

Grand Canyon Monitoring and Research Center, 2008, USGS workshop on scientific aspects of a 

long-term experimental plan for Glen Canyon Dam: April 10 11, 2007, Flagstaff, Ariz., U.S. 

Geological Survey Open-File Report 2008-1153, 79 p.

Gresswell, R.E., 1991, Use of antimycin for removal of brook trout from a tributary of Yellowstone 

Lake: North American Journal of Fisheries Management, v. 11, no. 1, p. 83 90.
78

Hammonds, J., Kulp, M.A., Moore, S.E., Rosenlund, B., 2006, Restoration of Sams Creek and an 

assessment of brook trout restoration methods: Great Smoky Mountains National Park, Georgia 

Tech Library and Information Center, Government Funded Technical Reports, 

http://ntis.library.gatech.edu/handle/123456789/2601, accessed August 4, 2008.

Harding, E. K., Doak, D.F., and Albertson, J.D., 2001, Evaluating the effectiveness of predator 

control: the non-native red fox as a case study: Conservation Biology, v. 15(4), p. 1114-1122.

Hedrick, R.P., Gilad, O., Yun, S., Spangenberg, J.V., Marty, G.D., Nordhausen, R.W., Kebus, M.J., 

Bercovier, H., and Eldar, A., 2000, A herpesvirus associated with mass mortality of juvenile and 

adult koi, a strain of common carp: Journal of Aquatic Animal Health, v. 12, no. 2000, p. 44 57.

Hess, G.R., and King, T.J., 2002, Planning open spaces for wildlife. I. Selecting focal species using 

a Delphi survey approach: Landscape and Urban Planning, v. 58, p. 25-40.

Hilwig, K.D. and Makinster, A.S., in press, Evaluating effects of a High Flow Event on Rainbow 

Trout Movement in Glen and Marble Canyons, Arizona by using acoustic telemetry and relative 

abundance measures. Submitted to Proceedings of the Colorado River Basin Science and 

Resource Management Symposium, Scottsdale, Ariz., November 18–20, 2008.

Hoffnagle, T.L., Valdez, R.A, and Speas, D.W., 1999, Fish abundance, distribution, and habitat 

use. Pages 273-287 in Webb, R.H., J.C. Schmidt, G.R. Marzolf, and R.A. Valdez, eds., The 

Controlled Flood in Grand Canyon. American Geophysical Union monograph 110.

Humston, R., Ault, J.S., Larkin, M.F., and Luo, J., 2005, Movements and site fidelity of the 

bonefish Albula vulpes in the northern Florida Keys determined by acoustic telemetry: Marine 

Ecology Progress Series, v. 291, p. 237 248.

Hunt, T.A., 2008, The effects of capture by trammel nets on native Arizona fishes: Master‘s Thesis

submitted to Northern Arizona University, Flagstaff, AZ, December 2008, 46 p.Invasive Animals 

Cooperative Research Center, 2006, The Feral Flyer, a monthly newsletter of the Invasive 

Animals Cooperative Research Center, Australia, v. 64.

Ibbotson, A.T., Beaumont, W.R.C., Collinson, D., Wilkinson, A., and Pinder, A.C., 2004, A crossriver antenna array for the detection of miniature passive integrated transponder tags in deep, fast 

flowing rivers: Journal of Fish Biology, v. 65, no. 5, p. 1441 1443.

Jackson, D.A., Peres-Neto, P.R., and Olden, J.D., 2001, What controls who is where in freshwater 

fish communities the roles of biotic, abiotic, and spatial factors: Canadian Journal of Fisheries 

and Aquatic Sciences, v. 58, p. 157 170.

Jennings, M.J., and Philipp, D.P., 1994, Biotic and abiotic factors affecting survival of early life 

history intervals of a stream-dwelling sunfish: Journal Environmental Biology of Fishes, v. 39, 

no. 2, p. 153 159.

Johnstone, H.C., and Lauretta, M.V., 2007, Native fish monitoring activities in the Colorado River 

during 2004 annual report: Cooperative agreement 04WRAG0011, report to Grand Canyon 

Monitoring and Research Center, February 2007, 85 p.

Kaeding, L.R., and Zimmerman, M.A., 1983, Life history and ecology of the humpback chub in the 

Little Colorado River and Colorado Rivers of the Grand Canyon: Transactions of the American 

Fisheries Society, v. 112, no. 5, p. 577 594.
79

Kendle, E.R., 1970, Sexual discrimination by olfaction in the black bullhead, Ictalurus melas. State 

of Nebraska Game and Parks Commission Job Progress Reports, March 1, 1969-February 28, 

1970: 21-31.

Kolar, C.S., and Lodge, D.M., 2002, Ecological predictions and risk assessment for alien fishes in 

North America: Science, v. 298, no. 5596, p. 1233 1236

Korman, J., Kaplinski, M., and Buszowski, J., 2006, Effects of air and mainstem water 

temperatures, hydraulic isolation, and fluctuating flows from Glen Canyon Dam on water 

temperatures in shoreline environments of the Colorado River in Grand Canyon final report: 

Cooperative Agreement 04WRAG00006, report to Grand Canyon Monitoring and Research 

Center, October 2006.

Korman, J., Kaplinski, M., Hazel, J., and Melis, T., 2005, Effects of the experimental fluctuating 

flows from Glen Canyon Dam in 2003 and 2004 on the early life history stages of rainbow trout 

in the Colorado River final report: Cooperative Agreement 04WRAG0006, report to Grand 

Canyon Monitoring and Research Center, June 2005.

Lassuy, D.R, 1995, Introduced species as a factor in extinction and endangerment of native fish 

species: America Fisheries Society Symposium, v. 15, p. 391–396.

Leibfried, W., Johnstone, H., and Cross, J., 2003, Trout removal in Bright Angel Creek, Grand 

Canyon National Park: A potential recovery effort for native fishes. Proceedings from the 

Colorado River Science Symposium, Flagstaff, Ariz., October 28 30, 2003,

www.gcmrc.gov/news_info/outreach/symposiums/2003/cd/pdfs/leibfried_symp03.pdf, accessed 

August 4, 2008.

Leibfried, W., Johnstone, L., Rhodes, S., Lauretta, M., 2005, Feasibility study to determine the 

efficacy of using a weir in Bright Angel Creek to capture brown trout: Final report prepared for 

Grand Canyon National Park, SWCA Project # 6462-091, November 2005.

Leibfried, W., Hilwig, K., Lauretta, M., 2004, Restoring Native Fish Habitat in Selected Tributaries 

of Grand Canyon National Park: Trip report prepared for Grand Canyon National Park, SWCA, 

March 2004.

Leung, B., Lodge, D.M., Finnoff, D., Shogren, J.F., Lewis, M.A. and Lamberti, G., 2002, An ounce 

of prevention or a pound of cure: bioeconomic risk analysis of invasive species: Proceedings of 

the Royal Society of London, v. 269, p. 2407 2413.

Lintermans, M., and Raadik, T., 2003, Local eradication of trout from streams using rotenone: The 

Australian experience, in Managing invasive freshwater fish in New Zealand: Proceedings of a 

workshop hosted by the Department of Conservation, May 10 12, 2001, Hamilton, New 

Zealand, p. 95 111.

Lukas, J.A., and Orth, D.J., 1995, Factors affecting nesting success of smallmouth bass in a 

regulated Virginia stream: Transactions of the American Fisheries Society, v. 124, no. 5, p. 

726 735.

MacKenzie, D.I., Nichols, J.D., Royle, J.A., Pollock, K.H., Hines, J.E., and Bailey, L.L., 2006, 

Occupancy estimation and modeling: inferring patterns and dynamics of species occurrence: San 

Diego, Calif., Elsevier, 324 p.
80

MacKenzie, D.I., Nichols, J.D., Sutton, N., Kawanishi, K., and Bailey, L.L., 2005, Improving 

inferences in population studies of rare species that are detected imperfectly: Ecology, v. 86, p. 

1101 1113.

MacKenzie, D.I., Royle, J.A., Brown, J.A., and Nichols, J.D., 2004, Occupancy estimation and 

modeling for rare and elusive populations, in Thompson, W.L., ed., Sampling rare or elusive 

species: Washington, D.C., Island Press, p.149 172.

Makinster, A.S., Rogers, R.S., and Persons, W., 2007, Status of the Lees Ferry trout fishery 2006 

annual report: Cooperative Agreement 05WRAG0050, report to Grand Canyon Monitoring and 

Research Center, April 2007.

Makinster, A.S., Hangsleben, M., and Persons, W.R., 2008, Lees Ferry long-term rainbow trout 

monitoring, 2008 Trip Report: Cooperative Agreement 05WRAG0050-Mod-5), report to Grand 

Canyon Monitoring and Research Center, December 2008.

Makinster, A.S., Rogers, R.S. Hangsleben, M., Avery, L.A., and Persons, W., 2009 , Grand 

Canyon long-term non-native fish monitoring, 2008 Annual Report: Cooperative Agreement # 

G09AC00036, report to Grand Canyon Monitoring and Research Center, September 2009.

Mallen-Cooper, M., 1999, Developing fishways for non-salmonid fishes; a case study from the 

Murray River in Australia, in Odeh, M., ed., Innovations in Fish Passage Technology: Bethseda, 

Maryland, American Fisheries Society, p. 173 195.

Mallen-Cooper, M., Stuart, I.G., Hides-Pearson, F., and Harris, J.H., 1995, Fish migration in the 

Murray River and assessment of the Torrumbarry fishway: final report to the Murray-Darling 

Basin Commission. NMRC Project N002.

Meffe, G.K., 1984, Effects of abiotic disturbance on predator-prey fish species. Ecology v. 65, p. 

1525-1534.

Miller, R.R, 1961, Man and the changing fish fauna of the American Southwest: Papers of the 

Michigan Academy of Science, Arts, and Literature, v. 46, p. 365 404.

Minckley, W.L, 1973, Fishes of Arizona: Phoenix, Ariz., Arizona Game and Fish Department, 293 

p.

Minckley, W.L., Hendrickson, D.A., and Bond, C.E., 1986, Geography of western North American 

freshwater fishes: Description and relationships to intracontinental tectonism, in Hocutt, C.H., 

and Wiley, E.O., eds., The zoogeography of North American freshwater fishes: New York, NY, 

John Wiley and Sons, p. 519-613.

Minckley, W.L., and Deacon, J.E., 1991, Battle against extinction: native fish management in the 

American West: Tucson, Ariz., University of Arizona Press.

Mueller, G., Walters, C., Holden, P.B., Walker, P.G., Landye, J., Johnson, B., 1999, Scientific 

review of the Glen Canyon Dam modifications to control downstream temperatures plan and 

draft environmental assessment, January, 1999, and supporting documentation: prepared for the 

Bureau of Reclamation, Upper Colorado Region, Salt Lake City, Utah.

Mueller, G.A., and Marsh, P.C., 2002, Lost, a desert river and its native fishes: A historical 

perspective of the Lower Colorado River: Denver, Colorado, Information and Technology Report 

USGS/BRD/ITR - 2002 - 0010, U.S. Government Printing Office, 69 p.
81

Nicol, S.J., Lieschke, J.A., Lyon, J.P., and Koehn, J.D., 2004, Observations on the distribution and 

abundance of common carp and native fish, and their response to a habitat restoration trial in the 

Murray River, Australia. New Zealand: Journal of Marine and Freshwater Research, v. 38, p. 

541 552.

Pacey, C.A., and P.C. Marsh. 1998. Resources used by native and non-native fishes of the lower 

Colorado River: Literature review, summary, and assessment of relative roles of biotic and 

abiotic factors in management of imperiled indigenous ichthyofauna. Submitted to BOR, 

Boulder City, NV, Agreement Number 7-MT-30-R0012 by Arizona State University, Tempe. 

Paukert, C.P., Coggins, L.G., and Flaccus, C.E., 2006, Distribution and movement of humpback 

chub in the Colorado River, Grand Canyon, based on recaptures: Transactions of the American 

Fisheries Society, v. 135, no. 1, p. 539 544. 

Paukert, C.P., and Petersen, J.H., 2007, Comparative growth and consumption potential of rainbow 

trout and humpback chub in the Colorado River, Grand Canyon, Arizona, under different 

temperature scenarios: The Southwestern Naturalist, v. 52, p. 234 242.

Persons, W.L., Davis, B., Burton, G., and Kubly, D., 2003, Plan for non-native fish control in the 

Colorado River Ecosystem 2002 2006. Report from the nonnative control ad hoc committee to 

Glen Canyon Dam Adaptive Management Program Technical Work Group, January 2003. 

Petersen, J.H. and Paukert, C.P., 2005, Development of a bioenergetics model for humpback chub 

and evaluation of water temperature changes in the Grand Canyon, Colorado River: Transactions 

of the American Fisheries Society, v. 134, p. 960 974.

Pinder, A.C., Riley, W.D., Ibbotson, A.T. and Beaumont, W.R.C., 2007, Evidence for an autumn 

downstream migration and the subsequent estuarine residence of 0+ year juvenile Atlantic 

salmon Salmo salar L., in England: Journal of Fish Biology, v. 71, p. 260 264.

Pine, W.E., III, Martell, S.J.D., Walters, C.J., and Kitchell, J.F., 2009, Counterintuitive responses 

of fish populations to management actions: Some common causes and implications for 

predictions based on ecosystem modeling: Fisheries, v. 34, no., 4, p. 165-180.

Rahel, F.J., and Olden, J.D., 2008, Assessing the effects of climate change on aquatic invasive 

species, Conservation Biology 22(3), 521-533.

Renner, D., 2005, Distribution and habitat use of bull trout following the removal of nonnative 

brook trout: Master‘s thesis. Oregon State University, Corvallis.

Rogers, S., Ward, D., Clark, B. and Makinster, A., 2008, History and development of long-term 

fish monitoring with electrofishing in Grand Canyon, 2000-2007: report submitted to Grand 

Canyon Monitoring and Research Center Cooperative Agreement 04WRAG0016, April 2008.

Rogers, R.S., Speas, D.W., Ward, D.L., and Makinster, A.S., 2003, Grand Canyon long-term nonnative fish monitoring 2002 annual report: report submitted to Grand Canyon Monitoring and 

Research Center Cooperative Agreement 02WRAG0030, October 2003.

Rosi-Marshall, E.J., Kennedy, T.A., Hall, R.O., Baxter, C.V., Cross, W.F., Yard, M.D., Behn, K., 

Gaul, A., Ulseth, A., Wellard, H., and Zahn, S., 2008, Linking whole-system organic matter 

cycling to quantitative food webs in the Colorado River, Annual Report 2008 to Grand Canyon 

Monitoring and Research Center. 38pp.

Ryden, D., Davis, J. and Jackson, J., 2005, An overview of channel catfish removal efforts in the 

San Juan River: 1996-2004. Abstract in Upper Colorado River Endangered Fish Recovery 
82

Program, Upper Colorado River and San Juan River Basins, 26th Annual Recovery Program 

Researchers‘ Meeting, January 19-20, Grand Junction, Colorado.

Seager, R., Ting, M., Held, I., Kushnir, Y., Lu, J., Vecchi, G., Huang, H.-P., Harnik, N., Leetmaa,

A., Lau, N.-C., Li, C., Velez, J., and Naik, N., 2007, Model projections of an imminent transition 

to a more arid climate in southwestern North America: Science, v. 316, p. 1181–1184.

Simonson, T.D., and Swenson, W.A., 1990, Critical stream velocities for young-of-year 

smallmouth bass in relation to habitat use: Transactions of the American Fisheries Society, v. 

119, no. 5, p. 902 909.

Sorensen, P.W., and Stacey, N.E., 2004, Brief review of fish pheromones and discussion of their 

possible uses in the control of non-indigenous teleost fishes: New Zealand Journal of Marine and 

Freshwater Research, v. 38, p. 399 417.

Sponholtz, P.J., and VanHaverbeke, D.R., 2007, Bright Angel Creek trout reduction project: 

summary report of fall 2006 weir and electrofishing efforts: Submitted to the National Park 

Service, Grand Canyon National Park under Interagency Agreement R8219070736, May 2007, 

19 p.

Stewart, I., McKenzie, J., Williams, A., and Holt, T., 2006, Managing a migratory pest species: a 

selective trap for common carp: North American Journal of Fisheries Management, v. 26, no. 4, 

p. 888 893.

Stone, D.M., and Gorman, O.T., 2006, Ontogenesis of the endangered humpback chub (Gila 

cypha) in the Little Colorado River, Arizona: American Midland Naturalist, v. 155, p. 123 135.

Stone, D.M., VanHaverbeke, D.R., Ward, D.L., and Hunt, T.A., 2007, Dispersal of nonnative 

fishes and parasites in the intermittent Little Colorado River, Arizona: The Southwestern 

Naturalist, v. 52, no. 1, p.130 137. 

Stone, D. 2008. Fall 2008 Monitoring of Humpback Chub (Gila cypha) and other Fishes in the 

Lower 13.57 km of the Little Colorado River, Arizona: trip report to Grand Canyon Monitoring 

and Research Center Interagency Acquisition No. 01-3022-R1009, November 2008.

Strange, E.M., Moyle, P.B., and Foin, T.C., 1993, Interactions between stochastic and deterministic 

processes in stream fish community assembly: Environmental Biology of Fishes, v. 36, no. 1, p. 

1 15.

SWCA Environmental Consultants, 2006, Bright Angel Creek and Roaring Springs Creek predator 

load survey and nonnative fish removal study: report to Grand Canyon National Park, May 2006.

Tasmanian Inland Fisheries Service, 2009, Carp management program Annual Report 2008-2009: 

report to Tasmanian Inland Fisheries Service Lakes Sorell and Crescent Carp Management 

Program, July 2009.

Thieme, M.L., McIvor, C.C., Brouder, M.J., and Hoffnagle, T.L., 2001, Effects of pool formation 

and flash flooding on relative abundance of young-of year flannelmouth suckers in the Paria 

River, Arizona: Regulated Rivers: Research and Management, v. 17, p. 145 156.

Timms, A.M. and Kleerekoper, H., 1972, The locomotor responses of male Ictalurus punctatus, the 

channel catfish, to a pheromone released by the ripe female of the species. Transactions of the 

Americam Fisheries Society, no. 2, p. 302-310.
83

Thorrold, S.R., Latkoczy, C., Swart, P.S., and Jones, C.M., 2001, Natal homing in a marine fish 

metapopulation: Science, v. 291, no. 5502, p. 297–299.

Topping, D.J., Schmidt, J.C., and Vierra, L.E.. Jr., 2003, Computation and analysis of the 

instantaneous discharge record for the Colorado River at Lees Ferry, Arizona May 8, 1921, 

through September 30, 2000: U.S. Geological Survey Professional Paper 1677, 118 p.

Tyre, A.J., Possingham, H.P., and Lindenmayer, D.B., 2001, Inferring process from pattern: can 

territory occupancy provide information about life history parameters?: Ecological Applications, 

v. 11, p. 1722 1737.

Tyus, H.M., and Saunders, J.F., III, 2000, Nonnative fish control and endangered fish recovery: 

Lessons from the Colorado River: Fisheries, v. 25, no. 9, p. 17-23.

Tyus, H.M., and Saunders, J.F., III, 1996, Nonnative fishes in natural ecosystems and a strategic 

plan for control of nonnatives in the Upper Colorado River Basin : draft report for the Recovery 

implementation program for endangered fish species in the upper Colorado River basin, 110 p.

U.S. Department of the Interior, 1995, Operation of Glen Canyon Dam Final Environmental Impact 

Statement, Colorado River Storage Project, Coconino County, Arizona: Salt Lake City, Utah, 

Bureau of Reclamation, Upper Colorado Regional Office, 337 p.

Valdez, R.A., 2008, Life history and ecology of fish in the Grand Canyon area of the Colorado 

River, wth emphasis on temperature requirements to evaluate a selective withdrawal structure 

for Glen Canyon Dam: report to Bureau of Reclamation, Salt Lake City, January, 2008.

Valdez, R.A., Carothers, S.W., Douglas, M.E., Douglas, M., Ryel, R.J., Bestgen, K.R., and 

Wegner, D.L., 2000, Research and implementation plan for establishing a second population of 

humpback chub in Grand Canyon: report to Grand Canyon Monitoring and Research Center, 

December 2000.

Valdez, R.A., and Masslich, W.J., 1999, Evidence of reproduction by humpback chub in a warm 

spring of the Colorado River in Grand Canyon, Arizona: Southwestern Naturalist v. 44, p. 384-

387.

Valdez, R.A., and Ryel, R.J., 1995, Life history and ecology of the humpback chub (Gila cypha) in 

the Colorado River, Arizona. Report to Bureau of Reclamation, September 1995.

Valdez, R.A., and Speas, D.W., 2009, An assessment of risks and benefits to fish from a selective 

withdrawal structure on Glen Canyon Dam: report to Bureau of Reclamation, Salt Lake City, 

January, 2009.

Voichick, N., and Wright, S.A., 2007, Water-temperature data for the Colorado River and 

tributaries between Glen Canyon Dam and Spencer Canyon, northern Arizona, 1988 2005: U.S. 

Geological Survey Data Series 251, 24 p.

Washington State Aquatic Nuisance Species Committee, 2005, Early detection and rapid response 

plan for aquatic invasive species in Washington State. Draft document October 3, 2005. 

http://www.psparchives.com/publications/our_work/protect_habitat/ans/main_ans/EDRR.pdfWal

lace, C.R., 1970. The use of pheromones and sound during reproduction by the black bullhead 

Ictalurus melas. State of Nebraska Game and Parks Commission J ob Progress Reports, March 1, 

1969-February 28, 1970: 33-38.
84

Walters, C.J., and Korman, J., 1999, Linking recruitment to trophic factors: revisiting the BevertonHolt recruitment model from a life history and multispecies perspective: Reviews in Fish Biology 

and Fisheries, v. 9, p. 1 16.

Webb, R.H., McCabe, G.J., Hereford, R., and Wilkowske, C., 2004, Climate fluctuations, drought, 

and flow of the Colorado River: U.S. Geologic Survey Fact Sheet 2004 3062, 4 p.

Weidel, B.C., D.C. Josephson, and C.E. Kraft. 2002. Fish community response to removal of 

introduced smallmouth bass in an oligotrophic Adirondack lake. Department of Natural 

Resources, Cornell University, Ithaca. N.Y. 

www.dnr.cornell.edu/facstf/kraft/publications/weidel_et_al_CJFAS.pdf. Weiss, S.J., 1993, 

Spawning, movement and population structure of flannelmouth sucker in the Paria River: 

Tucson, Ariz., University of Arizona, Master‘s thesis.

Wieringa, M.J., and Morton, A.G., 1996, Hydropower, adaptive management, and biodiversity: 

Environmental Management, v. 20, no. 6, p. 831 840.

Woodbury, A.M., 1959, An ecological study of the Colorado River in Glen Canyon, in Dibble, 

C.E., ed., Ecological studies of the flora and fauna in Glen Canyon: Salt Lake City, 

Anthropological Papers, no. 40 (Glen Canyon Studies Number 7), University of Utah 

Department of Anthropology, University of Utah Press, p. 149-176

Young, M.K., Micek, B.K. and Rathbun, M., 2003, Probable pheromonal attraction of sexually 

mature brook trout to mature male conspecifics: North American Journal of Fisheries 

Management, v. 23, p. 276–282.
85

The following descriptions of known Grand Canyon nonnative fish species of concern are 

adapted from Scott and Crossman (1973), Lee and others (1980), Ross and Brennenman (2002), 

Fuller (2008a, b, c, d, and e), Nico and Fuller (2008), and Nico and others (2008). 

The common carp is one of the most popular sport fish in Europe and its popularity is growing in 

the United States.

The native range of this species is in Europe and Asia. It has been widely introduced throughout the 

North America and other continents. Common carp generally inhabit lakes, ponds, and the lower 

sections of rivers and can be found in brackish-water estuaries, backwaters, and bays; they are less 

abundant in clear waters or streams with a high gradient (Pflieger, 1975; Trautman, 1981; Ross,

2001; Boschung and Mayden, 2004).

Carp are found throughout the mainstem of the Colorado River but are more commonly captured 

downstream of the Little Colorado River confluence area. Carp captures generally increase with 

downstream distance.

Larval carp feed primarily on zooplankton. Juveniles and adults feed on benthic organisms (for 

example, chironomids, gastropods and other larval insects), vegetation, detritus, and plankton (for 

example, cladocerans, copepods, amphipods, mysids; Summerfelt and others, 1971; Eder and 

Carlson, 1977; Panek, 1987).
86

Carp spawn in aggregations from early spring into late fall, often migrating to suitable areas. Adult 

females can spawn up to three times in a season (Smith and Walker, 2004). Carp have a fecundity 

of 163,000 eggs per kilogram whole female weight (Sivakumaran and others, 2003). Spawning 

may occur in rivers, lakes, and shallow streams.

Common carp may prey upon the eggs of other fish species (Moyle, 1976; Taylor and others, 1984; 

Miller and Beckman, 1996). Silt resuspension and uprooting of aquatic plants caused by feeding 

activities can disturb spawning and nursery areas of native fishes (Ross, 2001). Common carp are 

currently found in Grand Canyon, have expansion potential in warming water, and also co-occur 

with humpback chub in the Little Colorado River.

Piscicides such as antimycin and rotenone are effective toxicants for common carp. Carp selective 

traps have been developed based on behavioral characteristics of carp during spawning migrations. 

Baiting stations have been developed to deliver poison bait and other piscicides specifically to carp. 

Attractants, genetic manipulation, and disease vectors are currently being investigated. 

Identification of carp ―hot spots,‖ areas of high carp densities where spawning or migration 

concentrate carp, is a technique currently used in many carp control programs. Identification of 

these hot spots is done through telemetry, isotope analysis, and larval drift samples. These areas are 

then targeted with mechanical and chemical removal programs.
87

The fathead minnow is a popular bait and forage fish in many areas of the Colorado River Basin.

This species is native to much of North America from Quebec to the Northern Territories, south to 

Alabama, Texas, and New Mexico, and the Mississippi and Rio Grande River Basins (Page and 

Burr, 1991). It inhabits streams, rivers, ponds and lakes.

Fathead minnows are captured most frequently in backwaters throughout the Colorado River below 

the Little Colorado River Confluence (Ackerman, 2007). 

Fathead minnows are schooling fish, feeding primarily on plant material and small invertebrates. 

This species is able to tolerate a wide range of environmental conditions, including high 

temperatures, low oxygen levels, and high turbidities. Fathead minnows tend to disperse 

downstream (Schlosser, 1995).

Spawning is prolonged from late spring through midsummer. Eggs are deposited over submerged 

objects. Fathead minnows are one of the only cyprinids in which the males nest guard. Nests may 

contain as many as 12,000 eggs, and females may spawn as many as 12 times in a single summer. 

Annual fecundity ranges from 7,000 to 11,000 eggs per female. Some individuals may mature and 

spawn during their first summer of life, but spawning is usually delayed until the second summer

(Gale and Buynak, 1982).
88

Fathead minnows have been implicated as a threat to young of the Colorado pikeminnow 

(Ptychocheilus lucius) in the upper Colorado River Basin (Karp and Tyus, 1990). Fathead minnow 

colonization was determined to cause food web changes (Zimmer and others, 2001) and increases 

in turbidity (Ross, 2002). 

Piscicides such as antimycin and rotenone are effective toxicants for the fathead minnow. Fish can 

be captured using seines; however, the effect of capture on the total population numbers is not 

known.

Increasing flows and reducing water temperature may temporarily reduce fathead minnow 

abundance (Lentsch and others 1996; Valdez and Ryel 1995).
89

The brown trout is a popular sport fish in many areas of the Colorado River Basin. 

This species is native to lakes and streams in Europe, northern Africa, and western Asia (Page and 

Burr, 1991). It generally inhabits cool water streams, rivers, and lakes with gravel and cobble 

substrates (Scott and Crossman, 1973).

Brown trout were introduced in Grand Canyon and its tributaries in the early 1900s. They are 

captured in greatest abundance in proximity to the confluence of Bright Angel Creek (Rogers and 

Makinster, 2006). Brown trout are also captured in several Grand Canyon tributary streams 

including Bright Angel, Tapeats, and Kanab Creeks (Leibfried and others, 2003).

Brown trout prefer water temperatures less than 16°C. They feed on benthic invertebrates, insect 

larvae, terrestrial insects, and mollusks. In addition, adults consume fish, small mammals, young 

water fowl, and frogs (Kelly-Quin and Bracken, 2008).

Spawning generally occurs in the fall in clean gravel and small cobble substrates (Behnke, 2002). 

Fertilization is external, with the female trout excavating a redd in streambed gravels. Fecundity 

ranges from 200 to 2,400 eggs per female, and once eggs are fertilized, the female covers the redd 

with gravel (Taube, 1976). Larval brown trout become free-swimming fry 3 7 d after hatching 

(Behnke, 2002). Small juveniles are benthopelagic, remaining in the substrates, while larger 

juveniles are pelagic, venturing into the water column (Morrow, 1980).

Native fish are preyed upon by brown trout in Grand Canyon (Valdez and Ryel 1995; Marsh and 

Douglas 1997). Brown trout were introduced into Flaming Gorge Reservoir to reduce populations 

of the Utah chub (Gila atraria; Teuscher and Luecke, 1996). 
90

Piscicides such as antimycin and rotenone are effective toxicants for brown trout. Extended 

desiccation of redds can cause mortality of trout eggs and sac fry (Korman and others, 2005). 

Electrofishing could also reduce brown trout abundance (Coggins, 2008). Mechanical removal 

using a weir or electrofishing during spawning migrations of brown trout into Bright Angel Creek

may reduce abundance and reproductive success (Sponholtz and VanHaverbeke, 2007).
91

The rainbow trout is a popular sport fish in many areas of the Colorado River Basin. 

This species is native to the Pacific Slope from Alberta, British Columbia, and Alaska, and south to 

Baja, California (Page and Burr, 1991). It generally inhabits cold water streams, rivers, and lakes

with gravel and cobble substrates (Scott and Crossman, 1973).

Rainbow trout were introduced in Grand Canyon and its tributaries in the early 1900s. They are 

captured in greatest abundance from Glen Canyon Dam to Bright Angel Creek (Rogers and others, 

2008). Rainbow trout are also captured in several Grand Canyon tributary streams, including the 

Little Colorado River, Bright Angel, Shinumo, Kanab, and Tapeats Creeks (Leibfried and others, 

2003).

Most rainbow trout are capable of migrating, or at least adapting to sea water. Rainbow trout prefer 

water temperatures of less than 12 C. Adults feed on aquatic and terrestrial insects, mollusks, 

crustaceans, fish eggs, minnows, and other small fish, including small trout; young feed 

predominantly on zooplankton (Behnke, 2002)

Spawning generally occurs in the spring in clean gravel and small cobble substrates (Behnke, 

2002). Fertilization is external, with the female trout excavating a redd in streambed gravels. 

Fecundity ranges from 700 and 4,000 eggs per female, and once eggs are fertilized, the female

covers the redd with gravel (McDowall, 1990). Larval rainbow trout become free swimming fry 

3 7 d after hatching (Behnke, 2002). Small juveniles are benthopelagic, remaining in the 

substrates. while larger juveniles are pelagic, venturing into the water column (Morrow, 1980).

Rainbow trout have been shown to consume humpback chub in the Little Colorado River (Marsh 

and Douglas, 1997). Rainbow trout may exert other negative impacts on native fish through 

competition. 
92

Piscicides such as antimycin and rotenone are effective toxicants for rainbow trout. Extended 

desiccation of redds can cause mortality of eggs and sac fry (newly hatched trout with attached egg 

yolks; Korman and others, 2005). Gill netting was effective in reducing rainbow trout abundance in 

alpine lakes (Knapp and Matthews, 1998). Electrofishing can also be used to reduce rainbow trout 

abundance (Coggins, 2008).
93

The bullhead is considered a rough fish and is not commonly eaten, although it is edible.

The native range of the black bullhead (Ameiurus melas) included the central plains west of the 

Appalachians and east of the Rockies, extending north into Saskatchewan and Manitoba, and south 

into south Texas and New Mexico. The native range of the brown bullhead (Ameiurus nebulosus) is 

from the Atlantic and Gulf Slope drainages from Nova Scotia and the St. Lawrence River, Great 

Lakes, Hudson Bay, and Mississippi River Basins in southeastern Saskatchewan, and south to 

Louisiana (Page and Burr, 1991). Both species inhabit ponds, lakes, and slow-flowing streams and 

rivers, preferring soft bottom substrates (Mayhew, 1987).

Bullheads are almost exclusively captured in the Little Colorado River and in the immediate 

proximity of the Colorado River confluence (Ackerman, 2007; U.S. Geological Survey, unpub. 

data, 2008). 

More tolerant than other catfish of muddy, brackish water, low oxygen, and pollution, bullheads are 

omnivorous, feeding primarily from the bottom on a wide range of plant and animal material, both 

live and dead. Bullheads feed extensively on aquatic insects, small crayfish, worms, small 

mollusks, crustaceans; they have been known to eat the eggs of other fish, as well as feeding 

extensively on minnows. Fathead minnows are of particular importance in their diet in the Iowa 

Lakes (Mayhew, 1987). Bullheads are more active at night, especially at dusk, when they move

from deep to shallow water (Dedual, 2004).

During late spring or early summer when water temperatures reach 70 F, bullheads excavate nests 

in mud bottoms under cover in about 0.6 to 1.2 m of water. The female lays 2,000 to 6,000 eggs.

Nests are guarded by both parents and eggs hatch in 4 to 6 d. Fry begin to school in compact balls,

which are guarded by adults until fry reach about 25 mm in length (Mayhew, 1987).
94

Black bullheads have been shown to consume humpback chub in the Little Colorado River and 

may exert a major negative effect on the population there (Marsh and Douglas, 1997). Minckley 

(1973) reported that this species is generally considered a pest in Arizona because it forms large 

stunted populations that compete with more desirable fish for space and food.

Piscicides such as antimycin and rotenone are effective toxicants for the bullhead. Fish can be 

captured using angling and baited hoop nets; however, the effect of capture on the total population 

numbers is not known.
95

The channel catfish is North America's most numerous catfish species and is an important sport 

fish to the angling community across the United States.

The channel catfish‘s native range is the central drainages of the United States. It is now found 

throughout big rivers and streams across the United States preferring deep lotic environments with 

sand, gravel, or rubble bottoms. Channel catfish also inhabit lakes, reservoirs and ponds.

Channel catfish were stocked into the Colorado River in the early 1900s and were commonly 

captured in Grand Canyon before the construction of Glen Canyon Dam (Woodbury, 1959).

Channel catfish are currently found throughout the mainstem Colorado River and its tributaries in 

Grand Canyon. Captures of channel catfish are most common in the Little Colorado River and 

below Lava Falls Rapid to Lake Mead.

Channel catfish feed primarily at night and on the bottom of streams or pond. Major foods are 

aquatic insects, crayfish, mollusks, crustaceans, and fish. Young channel catfish consume 

invertebrates, but larger ones may eat fish.

Channel catfish usually become sexually mature at 3 yr of age with spawning occurring mostly in 

rivers and streams in the spring and early summer when waters warm to 21°C to 29°C. Wild

populations of channel catfish may spawn as early as late February or as late as August, depending 

on the location. Water temperatures below 18 C and above 30 C will reduce hatching success.

Male channel catfish select secluded nest sites under banks or logs. Females spawn only once a 

year and produce about 6,600 to 8,800 eggs per kilogram of body weight. Eggs hatch in 6 to 10 d,

depending on water temperature. The male guards the eggs and young until approximately 7 d after 

hatching. 
96

Channel catfish may exert negative impacts on native fish through predation and competition 

during all life-history stages. Channel catfish are currently found in Grand Canyon and have 

expansion potential in warming water. Channel catfish also co-occur with humpback chub in the 

Little Colorado River. They were believed to be the greatest threat to endangered fish in the Upper 

Basin in 1991 (Hawkins and Nesler, 1991).

Piscicides such as antimycin and rotenone are effective toxicants for channel catfish. Hoop nets and 

slat traps baited with cheese bait or dog food and angling are effective methods to capture channel 

catfish. The efficacy of mechanical techniques in reducing channel catfish abundance is not certain.
97

The smallmouth bass is a popular sport fish in many areas of the Colorado River Basin. 

This species is native to the St. Lawrence-Great Lakes system, Hudson Bay, and Mississippi River 

Basins. This species generally inhabits shallow rocky areas of lakes, clear and gravel-bottom runs,

and flowing pools of rivers and shallow streams (Scott and Crossman, 1973)

Smallmouth bass were first discovered in Grand Canyon with the capture of a 348-mm adult fish in 

April 2003 2 mi downstream of Glen Canyon Dam. Subsequently, in April 2004, a 70-mm juvenile 

fish was captured 5 mi downstream of the dam.

Young smallmouth bass feed on plankton and immature aquatic insects, and adults prey upon 

crayfish, fish, and aquatic and terrestrial insects, and can be cannibalistic (Scott and Crossman, 

1973; Etiner and Starnes, 1993).

Smallmouth bass generally spawn in the late spring when the water temperature is from 15°C to 

18°C. The male builds a shallow plate-like depression in 0.7 3.0 m of water. Nests are constructed 

in shallow waters of lakes and rivers, on sand, gravel, or rocky bottoms. Eggs are deposited in the 

nest and fertilized by the male and typically hatch in 10 d. Males guard the nests and young.

Smallmouth bass have been implicated in the decline of bonytail chub(Gila elegans), humpback 

chub, and roundtail chub (Gila robusta), as well as other native species in the Colorado River 

Basin. Smallmouth bass have demonstrated invasion and rapid expansion potential in the upper 

Colorado River Basin (Fuller, 2007).
98

Piscicides such as antimycin and rotenone are effective toxicants for smallmouth bass. Desiccation 

of smallmouth bass nests can cause 100-percent egg mortality with only 24 h of exposure to air 

(Benson, 1976). Disturbance of nests with high dam releases of cool water negatively impacted 

hatching success (Montgomery and others, 1980); however, Benson (1976) reported that high 

steady flows positively impacted hatching success. Electrofishing may reduce smallmouth bass 

abundance (Fuller, 2007).

Ackerman, M.W., 2007, 2006 Native fish monitoring activities in the Colorado River, Grand 

Canyon: Report to Grand Canyon Monitoring and Research Center cooperative agreement 

04WRAG0011, 79 p.

Behnke, R.J., 2002, Trout and salmon of North America, The Free Press, N.Y.

Benson, N.G., 1976, Water management and fish production in Missouri River mainstem

reservoirs, in Osborn, J.F., and Alman, C.H., eds., Instream flow needs, v. 2: Bethesda, Md.,

American Fisheries Society, p. 141 147.

Boschung, H.T., Jr., and Mayden, R.L., 2004, Fishes of Alabama: Washington, D.C., Smithsonian 

Institution Press.

Dedual, M., 2004, Diet, vertical distribution, and movements of brown bullhead catfish (Ameiurus 

nebulosus) in southern Lake Taupo, New Zealand: New Zealand Journal of Marine and 

Freshwater Research, v. 38, p. 561 567.

Eder, S., and Carlson, C.A., 1977, Food habits of carp and white suckers in the South Platte and St. 

Vrain Rivers and Goosequill Pond, Weld County, Colorado: Transactions of the American 

Fisheries Society, v. 106, p. 339 349.

Etnier, D.A., and Starnes, W.C., 1993, The fishes of Tennessee: Knoxville, Tennessee, The 

University of Tennessee Press, USACA.

Fuller, P., 2008a, Ameiurus melas: USGS Nonindigenous Aquatic Species Database, Gainesville, 

FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=730, last accessed August 6, 2008].

Fuller, P., 2008b, Ictalurus punctatus: USGS Nonindigenous Aquatic Species Database, 

Gainesville, FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=2341, last accessed 

August 6, 2008].

Fuller, P., 2008c, Micropterus dolomieu : USGS Nonindigenous Aquatic Species Database, 

Gainesville, FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=396, last accessed 

August 6, 2008].

Fuller, P., 2008d, Oncorhynchus mykiss: USGS Nonindigenous Aquatic Species Database, 

Gainesville, FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=910, last accessed 

August 6, 2008].

Fuller, P., 2008e, Salmo trutta: USGS Nonindigenous Aquatic Species Database, Gainesville, FL, 

[http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=931, last accessed August 6, 2008].
99

Fuller, M., 2007, Development of a smallmouth bass and channel catfish control program in the 

lower Yampa River: FY 2007 annual report submitted to Colorado River Recovery Program, 

project no. 110, Salt Lake City, Utah.

Gale, W.F., and Buynak, G.L., 1982, Fecundity and spawning frequency of the fathead minnow a 

fractional spawner: Transactions of the American Fisheries Society, v. 111, no. 1, p. 35 40.

Hawkins, J.A., and Nesler, T.P., 1991, Nonnative fishes in the upper Colorado River Basin: an 

issue paper: final report, Colorado State University Larval Fish Laboratory and Colorado 

Division of Wildlife, Fort Collins, Colo.

Karp, C.A., and Tyus, H.M., 1990, Humpback chub, Gila cypha, in the Yampa and Green Rivers, 

Dinosaur National Monument, with observations on roundtail chub, Gila robusta, and other 

sympatric fishes: Great Basin Naturalist, v. 50, p. 257 264.

Kelly-Quinn, M., and Bracken, J.J., 2008, A seasonal analysis of the diet and feeding dynamics of 

brown trout, Salmo trutta L., in a small nursery stream: Aquaculture Research, v. 21, no. 1, p. 

107 124.

Knapp, R.A., and Matthews, K.R., 1998, Eradication of non-native fish by gill-netting from a small 

mountain lake in California. Restoration Ecology, v. 6, p. 207 213.

Korman, J.M., Kaplinski, M., Hazel, J.E., III, and Melis, T.S., 2005, Effects of the experimental 

fluctuating flows from Glen Canyon Dam in 2003 and 2004 on the early life history stage of 

rainbow trout in the Colorado River: final report, submitted to the Grand Canyon Monitoring and 

Research Center, Flagstaff, Ariz.

Lee, D.S., Gilbert, C.R., Hocutt, C.H., Jenkins, R.E., McAllister, D.E., and Stauffer, J.R., Jr., 1980, 

The atlas of North American freshwater fishes: North Carolina Biological Survey, North 

Carolina State Museum of Natural History, no. 1980-12, 867 p.

Leibfried, W., Johnstone, H., and Cross, J., 2003, Trout removal in Bright Angel Creek, Grand 

Canyon National Park: A potential recovery effort for native fishes, in Proceedings from the 

Colorado River Science Symposium, Flagstaff, Ariz.,

[www.gcmrc.gov/news_info/outreach/symposiums/2003/cd/pdfs/leibfried_symp03.pdf, last 

accessed August 5, 2008].

Lentsch, L.D., Muth, R.T., Thompson, P.D., Hoskins, B.G., and Crowl, T.A., 1996, Options for

selective control of nonnative fishes in the upper Colorado River Basin: final report to the

Recovery Program for the Endangered Fishes of the Upper Colorado River, publication 96-14, 

Utah Division of Wildlife Resources, Salt Lake City, Utah.

Marsh, P.C., and Douglas, M.E., 1997, Predation by introduced fishes on endangered humpback 

chub and other native species in the Little Colorado River, Arizona: Transactions of the 

American Fisheries Society, v. 126, p. 343 346. 

Mayhew, J., ed., 1987, Iowa Fish and Fishing: Des Moines, Iowa, Iowa Department of Natural 

Resources, 323 p.

Miller, A.I., and Beckman, L.G., 1996, First record of predation on white sturgeon eggs by 

sympatric fishes: Transactions of the American Fisheries Society, v. 125, p. 338 340.

Minckley, W.L., 1973, Fishes of Arizona: Phoenix, Ariz., Arizona Fish and Game Department, 

Sims Printing Company, Inc.
100

Montgomery, J.C., Fickeisen, D.H., and Becker, C.D., 1980, Factors influencing smallmouth bass 

production in the Hanford Area, Columbia River: Northwest Journal of Science, v. 54, no. 4, p.

296 305.

Morrow, J.E., 1980, The freshwater fishes of Alaska: University of British Columbia, Animal 

Resources Ecology Library, 248 p.

Moyle, P.B., 1976, Inland fishes of California: Berkeley, Calif., University of California Press, 405 

p.

Nico, L. and Fuller, P., 2008, Pimephales promelas: USGS Nonindigenous Aquatic Species 

Database, Gainesville, FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=621, last 

accessed August 6, 2008].

Nico, L., Maynard, E., and Schofield, P.J., 2008, Cyprinus carpio: USGS Nonindigenous Aquatic 

Species Database, Gainesville, FL, [http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=4, 

last accessed August 6, 2008].

Page, L.M., and Burr, B.M., 1991, A field guide to freshwater fishes of North America north of 

Mexico: Boston, Mass., The Peterson Field Guide Series, v. 42, Houghton Mifflin Company. 

Panek, F.M., 1987, Biology and ecology of carp, in Cooper, E.L., ed., Carp in North America:

Bethesda, Md., American Fisheries Society, p. 1 15.

Pflieger, W.L., 1975, The fishes of Missouri: Jefferson City, Mo., Missouri Department of 

Conservation, 343 p.

Rogers, R.S., and Makinster, A.S., 2006, Grand Canyon long-term non-native fish monitoring, 

2003 annual report, submitted to Grand Canyon Monitoring and Research Center, cooperative 

agreement 02WRAG0030.

Ross, S.T., Brennenman, W.M., and Slack, W.T., 2002, The inland fishes of Mississippi: Jackson, 

Miss., University Press of Mississippi (April 2002), 624 p.

Schlosser, I.J., 1995, Dispersal, boundary processes, and trophic-level interactions in streams 

adjacent to beaver ponds: Ecology, v. 76, p. 908 925.

Scott, W.B., and Crossman, E.J., 1973, Freshwater fishes of Canada: Fisheries Research Board of 

Canada Bulletin, v. 184, 866 p.

Sivakumaran, K.P., Brown, P., Stoessel, D., and Gile, A., 2003, Maturation and reproductive 

biology of female wild carp, Cyprinus carpio, in Victoria, Australia: Environmental Biology of 

Fishes, v. 68, no. 3, p. 321 332.

Smith, B.B., and Walker, K.F., 2004, Spawning dynamics of common carp in the River Murray, 

South Australia, shown by macroscopic and histological staging of gonads: Journal of Fish 

Biology, v. 64, no. 22, p. 336 354.

Sponholtz, P.J., and VanHaverbeke, D.R., 2007, Bright Angel Creek trout reduction project: 

summary report of fall 2006 weir and electrofishing efforts: submitted to the Grand Canyon 

National Park Service, Grand Canyon National Park, under interagency agreement 

R8219070736, 19 p.

Summerfelt, R.C., Mauck, P.E., and Mensinger, G., 1971, Food habits of the carp, Cyprinus carpio

L., in five Oklahoma reservoirs: Proceedings of the Southeastern Association of Game and Fish 

Commissions, v. 24, p. 352 377.
101

Taube, C.M., 1976, Sexual maturity and fecundity in brown trout of the Platte River, Michigan: 

Transactions of the American Fisheries Society, v. 105, no. 4, p. 529 533

Taylor, J.N., Courtenay, W.R., Jr., and McCann, J.A., 1984, Known impact of exotic fishes in the 

continental United States, in Courtenay, W.R., Jr., and Stauffer, J.R., eds., Distribution, biology, 

and management of exotic fish: Baltimore, Md., Johns Hopkins Press, p. 322 373.

Teuscher, D., and Luecke, C., 1996, Competition between kokanees and Utah chub in Flaming 

Gorge Reservoir, Utah-Wyoming: Transactions of the American Fisheries Society, v. 125, no. 4, 

p. 505 511.

Trautman, M.B., 1981, The fishes of Ohio: Columbus, Ohio, Ohio State University Press. 

Valdez, R.A., and Ryel, R.J., 1995, Life history and ecology of the humpback chub (Gila cypha) in 

the Colorado River, Arizona: report to Bureau of Reclamation, September 1995.

Woodbury, A.M., 1959, Ecological studies of flora and fauna in Glen Canyon: Salt Lake City, 

Utah, University of Utah Press, report no. 40.
102

Public information fact sheet produced by Grand Canyon National Park and SWCA Environmental Consulting about 

operation of the Bright Angel Creek weir.

 

HUMPBACK CHUB

FLANNELMOUTH SUCKER

Bright Angel Creek Temporary Fish Weir

Purpose and Need: The National Park Service is charged with preserving and protecting the natural resources within 

Grand Canyon. Active hands-on management of resources is at times required to achieve this goal. In Bright Angel 

Creek, the fish community has been altered in favor of nonnative salmonids, to the detriment of its native fishes. 

Construction and operation of a temporary weir in Bright Angel Creek will help to determine whether removal of 

brown trout will promote native fish survival.

FAQs

What is a weir? Answer: A weir is a barrier to fish movement with an attached cage to capture and hold live fish.

Why are the trout being removed? Answer: Fish surveys have shown declines in native fishes concurrent with increases 

in brown trout. Brown trout are predators on the young and small native fish. Removal may increase the survival and 

numbers of native fish in Bright Angel Creek and help to restore the fish community.

What happens to the fish? Answer: The trout are taken from the cage and euthanized. They are measured and weighed, 

and examined for tags or marks. They are disposed of outside the park.

What about the rainbow trout? Answer: Rainbow trout will not be removed for this study.

Which are native fishes? Answer: The native fishes include the flannelmouth sucker, bluehead sucker, and speckled 

dace. The endangered humpback chub may once have lived in Bright Angel Creek; they still are occasionally found in 

the Colorado River nearby.

Who is responsible for this project? Answer: The National Park Service is funding this project. The contract to conduct 

the work and analyze the results was awarded to SWCA, an environmental consulting firm based in Flagstaff, Ariz.

Contacts:

SWCA, Inc., Environmental Consultants

Flagstaff, AZ 86001

928 774 5500

Grand Canyon National Park

Jeffrey Cross

Director, Grand Canyon Science Center

928 638 7759
103
104
105
106