GRAND CANYON MONITORING AND RESEARCH CENTER

Protocols Evaluation Program

Aquatic Food Base Research and Monitoring

Final Report 

of the

Aquatic Food Base Study and Protocol Evaluation Panel

January 27, 2012

Panel:

Daren Carlisle (chair)a

Steve Gutreuterb

G. Chris Holdrenc

Brian Robertsd

Christopher T. Robinsone

a Ecologist, US Geological Survey, Reston, VA

b Research Statistician, US Geologial Survey, LaCrosse, WI

c Supervisory Biological Scientist, US Bureau of Reclamation, Denver, CO

d Assistant Professor, Louisiana Universities Marine Consortium, Chauvin, LA

e Senior Research Scientist, Swiss Federal Institute of Aquatic Science and 

Technology (Eawag/ETHZ), Duebendorf, Switzerland
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Executive Summary

Maintenance of key native and non-native fish species is a strategic goal of 

the Glen Canyon Dam Adaptive Management Program, and has been translated into 

specific policies as part of the strategic plan. Goal 1 of this policy is to “Protect or 

improve the aquatic food base so that it will support viable populations of desired 

species at higher trophic levels,” which explicitly recognizes the importance of the 

aquatic food web to the viability of desired fish populations. 

The Grand Canyon Monitoring and Research Center initiated research to 

understand the food-base resources of desired native and non-native fishes. This 

research quantified, for the first time, aquatic food webs of the Colorado River in 

Glen and Grand Canyons. Subsequently, the Grand Canyon Monitoring and Research 

Center proposed long-term monitoring of various food web components in the 

Colorado River. This review panel was convened as part of the Protocol Evaluation 

Program and charged with evaluating the validity of the findings from the Aquatic 

Food Base Study, as well as the adequacy of the proposed long-term monitoring 

plan. Our comments and recommendations follow.

The Aquatic Food Base Study was highly successful in at least three ways. 

First, it identified the invertebrate food resources that support Colorado River fishes 

and provided strong evidence that production of humpback chub and rainbow trout 

are limited by their food. Second, it clearly showed how management actions, like 

the 2008 High Flow Experiment, can influence desired fish populations via the 

aquatic food web. This information is critical to Glen Canyon Dam Adaptive 

Management Program Strategic Goal 1. Finally, the Aquatic Food Base Study was 

remarkably cost effective because it employed a great deal of resource leveraging 

by, and synergism among, the principal investigators. The panel commends the 

principal investigators, science support staff, the Grand Canyon Monitoring and 

Research Center and other supporting institutions for this excellent body of work.

In general, we found adequate evidence to support the primary conclusions 

drawn from the Aquatic Food Base Study (Appendix A). Our major recommendation 

is to continue to develop clear management-relevant conclusions from the Study 

that can subsequently be synthesized into a publication that is intended for 

managers, stakeholders, and the public. We also identify several major information 

gaps that were revealed by the Study, and urge the Grand Canyon Monitoring and 

Research Center to make filling these gaps a priority for future research efforts.

After review of the Aquatic Food Base Study and the proposed long-term 

monitoring plan, the panel has several findings and recommendations. The panel 

firmly believes that the proposed monitoring will be successful in meeting 

information needs of Glen Canyon Dam Adaptive Management Program Strategic 

Goal 1 only if it is accompanied by a flexible research program that is capable of 
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exploiting both planned and unforeseen events. Indeed, a primary goal of the longterm monitoring and research program must be more than just characterization of 

current ecological conditions; it must also build the knowledge base required to 

predict ecological responses to anticipated changes in water management. The 

research and monitoring program must therefore be coordinated and adaptive as 

more information becomes available and new questions arise. The review panel 

offers three general recommendations that will strengthen the monitoring and 

research efforts of the Grand Canyon Monitoring and Research Center:

1) Develop a monitoring and research program that is flexible enough to 

exploit learning opportunities from both planned and unforeseen events. 

Such event-driven ecological response monitoring and research will build 

the knowledge base required to predict the effects of water management 

on key fish species.

2) Expand monitoring and research beyond the Colorado River mainstem

within Glen and Grand Canyons; information from key tributaries and 

mainstem locations above Lake Powell is critical to understanding the 

aquatic food webs of the Colorado River and what potential exists for 

successful alterations to the system.

3) The Grand Canyon Monitoring and Research Center should strive for 

improved integration of research across disciplines internally, and also 

with the Southwest Biological Center and Arizona Water Science Center.
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Background and Scope of Review

Maintenance of key native and non-native fish species is a strategic goal of 

the Glen Canyon Dam Adaptive Management Program. This goal has been 

translated into specific policies as part of the Glen Canyon Dam Adaptive 

Management Program strategic plan. Goal 1 of this policy is to “Protect or improve 

the aquatic food base so that it will support viable populations of desired species at 

higher trophic levels.” (hereafter “Goal 1”). Goal 1 explicitly recognizes the 

importance of the aquatic food web to the viability of desired fish populations. 

Understanding food webs is critical to managing ecosystems, yet the aquatic 

food web of the Colorado River within Glen and Grand Canyons had never been fully 

described. The Grand Canyon Research and Monitoring Center therefore initiated 

the Aquatic Food Base Study intending to fill this information gap. Specifically, the 

Study focused on describing key feeding linkages connecting basal resources to fish.

The field component of the Aquatic Food Base Study was completed in 2009, from 

which the Grand Canyon Research and Monitoring Center developed a long-term 

monitoring plan to address key information needs for Goal 1. This panel was 

convened to review the food-base research and proposed monitoring plan.

Panelists convened January 9-13 at the Grand Canyon Monitoring and 

Research Center in Flagstaff, AZ and Lees Ferry, AZ. The panel (and several 

stakeholders) was given a series of presentations from the Principal Investigators of 

the Aquatic Food Base Study and then visited the Glen Canyon section of the 

Colorado River. This was followed by a series of presentations and subsequent 

discussions in Flagstaff, AZ between Grand Canyon Monitoring and Research Center 

staff, the Principal Investigators, and the panel. Grand Canyon Research and 

Monitoring Center staff and the Principal Investigators of the Aquatic Food Base 

Study provided a written summary of the research and proposed monitoring 

(Kennedy et al., 2012), which was the primary information source provided to the 

review panel. The panel was also provided with original reports during the review 

session. The panel was given three primary charges:

1) Comment on the validity of the research findings and conclusions of the 

Aquatic Food Base Study,

2) Comment on whether the proposed monitoring protocols described in 

Kennedy et al. (2012) are a logical next step given the overall research 

findings, and
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3) Comment on whether the proposed monitoring protocols will be successful 

in meeting the information needs for the Glen Canyon Dam Adaptive 

Management Program Goal 1.

This report summarizes the panel’s findings and recommendations. We first 

provide general recommendations relevant to both the research and long-term 

monitoring. We then address each of the charges listed above.

General Recommendations

1. Successful adaptive management requires a monitoring and research 

program that is flexible enough to exploit learning opportunities from both 

planned and unforeseen events. Such event-driven ecological response 

monitoring and research will build the knowledge base required to predict the

effects of water management on key fish species; this ability is critical for Glen 

Canyon Dam Adaptive Management Program Strategic Goal 1. We agree that 

routine monitoring of carefully selected indicators of the food base and fish 

production will inform the Glen Canyon Dam Adaptive Management Program, but 

this alone will be insufficient to meet the information needs of Strategic Goal 1. The 

Aquatic Food Base Study and associated monitoring successfully identified the 

effects of a single High Flow Experiment in 2008 on the rainbow trout fishery. 

However, it is important to recognize that this study represents a sample size of one, 

limited to a single type of flow event, magnitude, and duration at a specific time of 

year. The ability to predict how future flow management affects the food base of 

key fish populations will require continued research associated with natural and 

human-caused flow events. 

Episodic discharge events are a prominent feature of the Colorado River 

system. It is likely that the ecological effects of other types of high flow events will 

differ from those observed in the Aquatic Food Base Study. For example, large 

monsoon events supply sediment-rich water from tributaries, but may have no 

effect on flow, turbidity, and primary production in the Glen Canyon Reach. Highflow events that differ in origin and magnitude also likely affect the food supply of 

humpback chub and rainbow trout, and therefore provide valuable opportunities to 

develop the information needed to predict effects of flow on these fishes. Sustained 

high flows, such as occurred during 2011 when more water was released from Glen 

Canyon Dam than at any time during the last decade, provide even greater nutrient 

loadings to the system than episodic releases or monsoons. While sustained high 

releases are not expected to have as much impact on habitat as high-flow events, 

their impact on the food web and fish populations may be more important and 

should be investigated.
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The review panel strongly encourages the Grand Canyon Monitoring and Research 

Center to initiate an adaptive monitoring and research program as soon as possible. 

Over two years have passed since the Aquatic Food Base Study team completed the 

field component of their project and the delay in having a plan in place has already 

resulted in missing major opportunities to learn more about the system. Specifically, 

having a monitoring and research program in place prior to 2011, would have allowed 

the Grand Canyon Monitoring and Research Center to directly study the impacts of the 

sustained high flows throughout the past year. Additionally, it is already known that 

there will be numerous manipulated flow events and other management actions, such 

as non-native fish removal, in the future and it is important to have an adaptive plan 

in place to study the impacts of these events. 

An ecological response monitoring and research program would minimally 

comprise the following six features: 

1. A funding mechanism analogous to the USGS Capital Equipment Fund 

is needed to support irregular multi-year episodes of investigation 

bracketing extreme-flow events that cannot be anticipated within the 

annual budgeting process. 

2. Decisions to engage in opportunistic ecological response monitoring 

and research must be made based on accumulated scientific 

knowledge and information about changes in runoff and water 

management within the Colorado River basin. 

3. General anticipatory research and monitoring protocols should be 

developed for major types of extreme flow events (e.g., large 

monsoons, stranding flows, unusually large winter snowpack 

conditions, major planned changes in water management). 

4. Accrued dedicated financial resources should be sufficient to repeat 

major aspects of the Aquatic Food Base Study and to address new 

hypotheses about effects of flows on the food supply to humpback 

chub and rainbow trout. 

5. Because management of rainbow trout and recovery of humpback 

chub depends on knowledge about effects of different types of flow 

events and hydrological conditions, the program should exploit 

opportunities provided by extreme flow events (both extreme high 

and low flows) in regulated and unregulated tributaries of the 

Colorado River. This feature is critical because it will reveal the 

practical limits and constraints on populations of humpback chub and 

rainbow trout. 

6. The program should accommodate new research that addresses 

critical information gaps. 

2. Understanding the Colorado River mainstem within Glen and Grand Canyons

requires a watershed approach; monitoring and research confined to the 

Colorado River mainstem downstream of Glen Canyon Dam will be inadequate 

in providing the information needs of Strategic Goal 1. Just as the major storage 
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reservoirs in the Colorado River Basin are managed as a synchronized network, 

ecological monitoring and research must also take a system-wide approach. This 

need is clearly underscored by the Aquatic Food Base Study, which found that the 

supply of fish food resources within the mainstem Colorado was influenced by 

tributaries. However, because the study was limited to the mainstem and to periods 

of relatively low releases from Glen Canyon Dam, it is still unknown how the 

hydrology, geology, and food webs of the tributaries influence the food webs and, 

ultimately, the populations of desired fish species within the Colorado mainstem. 

Similarly, comparisons of the aquatic food web in Grand Canyon with those of 

relatively free-flowing sections of the Colorado River (e.g., Cataract Canyon) would 

provide valuable insights to the ways in which flow dynamics, turbidity, 

temperature, and non-native fishes influence the food resources and populations of 

native fishes. It is obvious to the review panel that the geographic scope of future 

monitoring and research must be determined solely by the scientific questions; 

institutional constraints on geographic scope will undermine the ability of the Grand 

Canyon Monitoring and Research Center to address key information needs.

3. The Grand Canyon Monitoring and Research Center should strive for 

improved integration of research across disciplines internally, and also with the 

Southwest Biological Center and Arizona Water Science Center. The Grand 

Canyon Monitoring and Research Center has a rich history of high quality research. 

It was clear to the review panel, however, that more collaboration would improve 

the synergy and efficiency of monitoring and research efforts. Monitoring fish 

populations and their food resources have been linked to separate goals of the Glen 

Canyon Dam Adaptive Management Program and typically assigned to groups of 

scientists working separately. Yet, the Aquatic Food Base Study clearly shows that 

learning is enhanced when they are linked. This integration was driven by necessity, in 

order to construct quantitative food webs for the Colorado River. There are other 

examples where more interdisciplinary efforts may be fruitful, including the possibility of 

improved linkages between water quality and biology programs. Internally, there needs 

to be better integration of information between efforts supporting Strategic Goal 1, 

and ongoing monitoring and research of fish populations by Grand Canyon 

Monitoring and Research Center staff and external partners (e.g., Arizona Game and 

Fish). 

Increased collaboration will also help the Grand Canyon Monitoring and 

Research Center more efficiently collect and interpret a growing stream of data. The 

Aquatic Food Base Study produced a wealth of data. Routine monitoring and eventdriven ecological response monitoring and research will produce additional data 

needed to inform adaptive management of the Colorado River in Glen and Grand 

Canyon. There also exists a large body of data and knowledge from tributaries and 

other systems that contain information relevant to prediction of how the Colorado 

River food web and fishes will respond to other types of hydrological events, 

including water-management strategies and long-term regional trends in 

precipitation. However, it is important to recognize that data are not knowledge. 
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Knowledge is created by the analysis of data and integration of the resulting new 

information with existing relevant information. The current scientific assets of the 

Grand Canyon Monitoring Research Center are excellent in quality, but currently too 

meager in quantity to analyze monitoring data and integrate that information with 

other relevant information to ultimately build robust predictive capability and 

continually update and publish syntheses for both lay and scientific audiences. The 

review panel recommends the acquisition of at least one additional Research Grade 

scientist to assist the Grand Canyon Research and Monitoring Center with this growing 

need for expertise. 

Food Base Study: Review of Key Conclusions

The Aquatic Food Base Study was remarkably successful in at least three 

ways. First, it identified the invertebrate and algal food resources that support 

Colorado River fishes and provided strong evidence consistent with the hypothesis 

that production of humpback chub and rainbow trout are limited by production of 

their food. Second, it clearly showed how management actions, like the 2008 High 

Flow Experiment, influence desired fish populations via the aquatic food web. 

Finally, this panel believes the Aquatic Food Base Study was remarkable in the way 

it was executed; there was a great deal of resource leveraging by and synergism 

among the Principal Investigators. 

This Panel reviewed the primary conclusions of the Aquatic Food Base Study

that were articulated in Kennedy et al. (2012). These conclusions were drawn from 

the body of work primarily because they were deemed most relevant to managers 

and stakeholders, and particularly to Glen Canyon Dam Adaptive Management 

Program Strategic Goal 1. It should be noted that the Principal Investigators are still 

in the early stages of synthesizing the results from their data-rich project and it is 

likely additional conclusions will arise from this effort that should be incorporated 

into the adaptive monitoring and research plan. In this section, we systematically 

evaluate the evidence for each of the conclusions and offer suggestions for 

improvement. After discussing these comments and recommendations with the 

Principal Investigators during the review session, the Principal Investigators

subsequently revised the conclusions (Appendix A).

In general, we find adequate evidence within the body of work for most of 

the major conclusions. In some cases, this evidence was unclear or absent from 

Kennedy et al. (2012), but was made available to the panel by the Principal 

Investigators throughout the course of the review session. In other cases, we 

suggest relatively minor changes to the wording or reorganization of conclusions, 

including qualifying some statements or more clearly explaining the evidence. Of 
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greatest importance, the review panel strongly urged the Principal Investigators to 

clearly and succinctly explain the management implications for each conclusion for 

inclusion in subsequent revisions of Kennedy et al. (2012) and/or other synthesis 

product(s). Each of the conclusions is discussed below in more detail.

Conclusion 1: A combination of autochthonous and allochthonous organic matter 

serves as the base of the aquatic food web in Grand Canyon, but high quality algal 

matter plays a role disproportionate to its availability.

The panel finds that evidence is sufficient to support this conclusion. We also 

suggest the Principal Investigators include findings from Glen Canyon, which show 

very high contributions from autochthonous sources to the aquatic food web.

Conclusion 2: Flow operations and turbidity are strong controls on autochthonous 

production 

The panel finds that evidence is sufficient to support this conclusion.

Conclusion 3: Artificial floods can exert a strong control on invertebrate secondary 

production in the tailwater reach 

The panel finds that evidence is sufficient to support this conclusion, and suggest

rewording to “high-flow events.”

Conclusion 4: Invertebrates in downstream reaches of Grand Canyon may be limited 

by the availability of high quality algal resources 

Evidence was not made available to the review panel for this conclusion. 

Discussions with the Principal Investigators indicated that analyses supporting this 

conclusion are ongoing. We also suggested specifying invertebrate “growth” or 

“production” or “populations.” We also suggest using more informative language. 

Conclusion 5: The production of native and non-native fishes throughout Glen and 

Grand Canyon is fueled by key aquatic insects (i.e., Chironomidae and Simuliidae) that 

are in limited supply.

Evidence was sufficient to support this conclusion. We suggested greater clarity 

would be attained by limiting this conclusion to the first clause. 
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Conclusion 6: At certain locations and times, grazing pressure by fish populations may 

be a significant control on invertebrate biomass and production 

Conclusion 7: At certain locations and times, fish populations are limited by the 

availability of high-quality prey, competition for these food resources is important, and 

flow management (e.g., artificial flooding) that affects these invertebrates will act as a 

lever to change fish populations 

Evidence presented is consistent with competition, but does not alone demonstrate 

its existence. Actual demonstration of competition is extremely difficult—especially 

with observational data—and rarely done. Evidence is also unclear whether 

dynamics are top down (as suggestion in #6) or bottom up (#7). We suggested the 

authors tone down both conclusions and consider combining them. 

Priority Information Gaps Identified by the Food Base Study

The Aquatic Food Base Study provided a great deal of critical information 

needed for Glen Canyon Dam Adaptive Management Program Strategic Goal 1, but 

also identified several key information gaps. These gaps were identified and 

prioritized by both the review panel and the Principal Investigators. The top five

are listed in this section, and the remaining topics are listed in Appendix B.

 What were the food web and ecosystem characteristics of the pre-dam 

Colorado River? 

 What is the importance of tributaries in influencing or augmenting the food 

base for fishes in the Colorado River mainstem?

 To what degree do desired fish species limit their food base, and does this 

limitation directly influence the reproduction and recruitment of desired 

fishes—particularly humpback chub?

 How do flow manipulations affect aquatic food webs and food resources for 

desired fish species in Glen and Grand Canyons? Will future planned springtimed High Flow Events elicit a similar food web and ecosystem response as 

observed in 2008? 

 How might aquatic food webs and food resources for desired fish species be 

affected by changes to Glen Canyon Dam releases anticipated to result from 

long-term changes in climate, runoff, and water management? In particular, 
11

future dam releases may include wider swings in water temperature and 

quality.

Proposed Long-Term Monitoring: Review Comments

Grand Canyon Monitoring and Research Center staff and the Principal 

Investigators of the Aquatic Food Base Study provided the review panel with a 

description of proposed long-term monitoring activities (part 3 of Kennedy et al. 

2012). The review panel’s charge was to evaluate whether the proposed monitoring

1) is a logical extension of the food base study and appropriate based on our current 

understanding, and 2) will be successful in meeting the information needs for the 

Glen Canyon Dam Adaptive Management Program Goal 1.

As we previously explained in the General Comments, the review panel 

firmly believes that the proposed monitoring will be successful in meeting the 

information needs of Objective 1 only if it is accompanied by an flexible research 

and monitoring program that is capable of exploiting both planned and unforeseen 

events. Again, the panel emphasizes that monitoring programs need to be adaptive 

as more information becomes available and new questions arise. It is likely that 

additional monitoring adjustments will be necessary as new information arises. 

The proposed long-term monitoring plan is focused on collecting data to 

determine ecosystem metabolism rates (primarily gross primary production but 

potentially ecosystem respiration in the Glen Canyon tailwaters), water column 

organic matter (dissolved, fine particulate and coarse particle fractions) 

concentrations, invertebrate drift composition, emergent insect production, and 

benthic algae/ invertebrate biomass (also includes benthic organic matter). They 

propose sampling at time scales ranging from daily (metabolism rates) to yearly 

(benthic sampling) with other sampling occurring 10 times per year. Sampling is 

proposed to occur at between 5 and 8 locations depending on the metric. This 

proposed plan is summarized in Table 4 of Kennedy et al. (2012).

Below, we provide comments and recommendations for several specific elements of 

the proposed monitoring plan.

Sampling frequency: The Grand Canyon Monitoring and Research Center should 

consider whether the information gained by sampling 10X/year (particularly at the 

less accessible sites) is greater than the effort required beyond the already

scheduled trips to the sampling sites, which appears to be 4-6X/year. 
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Ecosystem Metabolism: It should be made clear that this largely refers to quantifying 

rates of gross primary production since currently it is not possible to accurately 

quantify rates of ecosystem respiration in the Grand Canyon. There is a large need 

for routine data processing and interpretation of these data. Is the expertise and 

resources available at Grand Canyon Monitoring and Research Center? It is not 

clear why gross primary productivity (GPP) monitoring is needed at all of the 

proposed sites, especially given the large need for data processing.

Organic Matter: When practical, organic inputs from tributaries and episodic events 

should be characterized.

Invertebrate Drift: It appears that pilot work is needed. Specifically, do samples 

from the margin (remote sites) compare to samples from the thalweg? Also, what is 

the needed sampling duration at remote sites? 

Emergent Insect Production: The review panel does not feel that the proposed 

emergence monitoring is feasible, but encourages pilot efforts to evaluate the 

feasibility of sticky traps in this unique environment—especially given the need to 

deploy over several week time periods. We suggest that these pilot efforts be 

attempted at Lees Ferry and Diamond Creek—which represent contrasting river 

conditions.

Benthic Algae & Invertebrates: Consider the use of basket or Hester-Dendy sampling 

to characterize drift/colonization of blackflies and other drifting insects, and to 

track patterns in biological diversity.

Literature Cited

Cross, W.F., C.V. Baxter, K.C. Donner, E.J. Rosi-Marshall, T.A. Kennedy, R.O. Hall, Jr., 

H.A. Wellard Kelly and R.S. Rogers. 2011. Ecosystem ecology meets adaptive 

management: food web response to a controlled flood on the Colorado River, 

Glen Canyon. Ecological Applications 21:2016−2033

Donner, K. C. 2011. Trophic basis of production of fishes in the Colorado River, 

Grand Canyon: An assessment of potential competition for food. M.S. Thesi, 

Department of Biological Sciences, Idaho State University, Pocatello, ID.

Kennedy, T., C. Baxter, R. Hall, E. Rosi-Marshall and W. Cross. 2012. A Summary of 

Research Conducted in Support of the Glen Canyon Dam Adaptive Management 

Program’s Goal 1—Aquatic Foodbase—Including Draft Monitoring Protocols. 

Unpublished.

Rosi-Marshall, E.J., Kennedy, T.A., Kincaid, D.W., Cross, W.F., Kelly, H.A.W., Behn. K.A.,

White, T., Hall, R.O., Jr., and Baxter, C.V., 2010, Short-term effects of the 2008 
13

high-flow experiment on macroinvertebrates in the Colorado River below Glen 

Canyon Dam, Arizona: U.S. Geological Survey Open-File Report 2010-1031, 28 

p.

Wellard Kelly, H.A., E.J. Rosi-Marshall, T.A. Kennedy, R.O. Hall, Jr., W.F. Cross and C.V. 

Baxter. In review. Macroinvertebrate diets reflect longitudinal and seasonal 

changes in food availability downstream of a large dam.
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APPENDIX A—Revised Conclusions from Food Base Study

1) Autochthonous organic matter, specifically diatoms, is the base of the aquatic 

food web in Glen Canyon. Evidence for this conclusion comes from diet and 

stable isotope analyses, and trophic basis of production calculations for 

invertebrates and rainbow trout (see Objective 3 and figure 8 in Kennedy et al. 

2012; Cross et al. 2011, Donner 2011, Kelly et al. in review). 

2) A combination of autochthonous and allochthonous organic matter is the 

base of the aquatic food web in Grand Canyon, but high quality algal matter 

supports the food web to an extent disproportionate to its availability. 

Evidence for this conclusion comes from organic matter budgets, diet and stable 

isotope analyses, and trophic basis of production calculations for invertebrates 

and rainbow trout (see Objective 1, 3 and figure 10 in Kennedy et al. 2012; Cross 

et al. 2011, Donner 2011, Kelly et al. in review). 

3) Flow operations and turbidity strongly control autochthonous production. 

Daily estimates of metabolism for the Colorado River near Diamond Creek across 

a range of flows and turbidity support this conclusion (see Objective 1 and figures 

3 and 4 in Kennedy et al. 2012).

4) Invertebrate production exhibits stepped declines below the Paria and Little 

Colorado Rivers, and production at sites below the Little Colorado River is 

extremely low relative to other streams and rivers. Evidence for this 

conclusion comes from three years of benthic invertebrate sampling and 

secondary production calculations at six sites (see Objective 2 and figure 5 in 

Kennedy et al. 2012; Cross et al. 2011). 

5) High flow events can exert a strong control on invertebrate assemblages and 

secondary production in the tailwater reach. Evidence for this conclusion 

comes from intensive sampling of benthic and drifting invertebrates before and 

after the March 2008 artificial flood (see Objective 2 and figures 5 and 8 in 

Kennedy et al. 2012; Rosi-Marshall et al. 2010, Cross et al. 2011). 

6) Fish production was dominated by rainbow trout at upstream sites (i.e., 

RKM 0 and 48) and flannelmouth sucker at downstream sites (i.e., RKM 204, 

266, and 362), and production was comparable among sites. Evidence for this 

conclusion comes from fish production calculations for two years and six sites 

(see Objective 2 and figure 6 in Kennedy et al. 2012; Donner 2011). 

7) The production of native and non-native fishes throughout Glen and Grand 

Canyon is principally fueled by two aquatic insect taxa—Chironomidae and 

Simuliidae. Evidence for this conclusion comes from diet and trophic basis of 
15

production calculations for the entire assemblage of fishes (see Objective 3 and 

figures 8 and 12 in Kennedy et al. 2012; Cross et al. 2011, Donner 2011). 

8) Fish production throughout Glen and Grand Canyon appears limited by the 

availability of high quality prey, particularly Chironomidae and Simuliidae, 

and fish may exert top-down control on these prey. This conclusion derives 

from calculations of the trophic basis of fish production and interaction strengths 

between fishes and their invertebrate prey (see Objective 3 and figure 12 in 

Kennedy et al. 2012; Donner 2011). 

9) Dam operations (e.g., artificial flooding) that affect these invertebrates can 

change fish production, and fish movements downstream may change those 

food webs. Evidence for this conclusion comes from detailed descriptions of 

food webs in Glen and Grand Canyons before and after the 2008 artificial flood 

(see Objective 2 and 3 and figures 5 and 6 in Kennedy et al. 2012; Cross et al. 

2011 and Donner 2011). 

10) The trophic basis of production of fishes overlaps and because these 

resources may be in limited supply there is strong potential for competition 

among native and non-native species. This conclusion stems from detailed 

analysis of fish diets, and calculations of trophic basis of fish production, and 

interaction strengths between fishes and their invertebrate prey (see Objective 3 

and figure 12 in Kennedy et al. 2012; Donner 2011).
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APPENDIX B—Other Important Information Gaps Identified by the Food Base 

Study

 There is a need for linking food-base resources to long-term expectations for 

water availability and climate change.

 There is a need for studying heterotrophs/microbes, especially given the 

need to follow dissolved organic carbon into the food web. This is needed to 

understand the bioavailability of this carbon and particulate carbon in the 

system

 What prevents tributary or regional native invertebrates from persisting in 

the Colorado River in Glen and Grand canyons?

 How have increases in the rainbow trout population near the Little Colorado 

River confluence altered the food web and potential competition for food? 
 A Review of GCMRC’s Aquatic 

Food Base Study & Proposed 

Monitoring Plan
The Review Panel

• S. Gutreuter, Research Statistician, USGS

• G. Holdren, Biologist, USBoR

• B. Roberts, Assistant Professor, LUMC

• C. Robinson, Research Scientist, EAWAG

• D. Carlisle, Ecologist, USGS (chair)
Our Charge
Our Charge

• Technical review of 

aquatic food base 

study
Our Charge

• Technical review of 

aquatic food base 

study

• Appropriateness 

and effectiveness 

of proposed 

monitoring plan
“Protect or improve the aquatic food base so that it 

will support viable populations of desired species at 

higher trophic levels.”

GCDAMP Strategic Goal:
General Recommendations

• Agile research & monitoring program

• River network perspective

• Integrated research

Need More:
Agility in Monitoring and 

Research 
Agility in Monitoring and 

Research 

• Potential to learn is highest when ecosystem 

components are “manipulated” by nature or 

humans
Agility in Monitoring and 

Research 

• Potential to learn is highest when ecosystem 

components are “manipulated” by nature or 

humans

• Develop anticipatory research & monitoring 

protocols for alternative scenarios, e.g., extreme 

monsoon event
Agility in Monitoring and 

Research 

• Potential to learn is highest when ecosystem 

components are “manipulated” by nature or 

humans

• Develop anticipatory research & monitoring 

protocols for alternative scenarios, e.g., extreme 

monsoon event

• Make resources available
Agility in Monitoring and 

Research 

• Potential to learn is highest when ecosystem 

components are “manipulated” by nature or 

humans

• Develop anticipatory research & monitoring 

protocols for alternative scenarios, e.g., extreme 

monsoon event

• Make resources available

• A single, fixed approach probably insufficient
River Network Perspective
River Network Perspective

• Tributaries crucial to 

mainstem food web
River Network Perspective

• Tributaries crucial to 

mainstem food web

• Need to know 

“ecological 

potential”--may be 

above Lake Powell
Information Integration
Information Integration

• Multiple USGS, other federal, & state entities 

collect data
Information Integration

• Multiple USGS, other federal, & state entities 

collect data

• Priorities on different components of food web
Information Integration

• Multiple USGS, other federal, & state entities 

collect data

• Priorities on different components of food web

• native fish population recruitment
Information Integration

• Multiple USGS, other federal, & state entities 

collect data

• Priorities on different components of food web

• native fish population recruitment

• water quality
Information Integration

• Multiple USGS, other federal, & state entities 

collect data

• Priorities on different components of food web

• native fish population recruitment

• water quality

• ecosystem processes
Information Integration

• Multiple USGS, other federal, & state entities 

collect data

• Priorities on different components of food web

• native fish population recruitment

• water quality

• ecosystem processes

• Integration of research vs. information
Food Base (web) Study

What went right:
Food Base (web) Study

• Revealed energetic pathways and constraints 

What went right:
Food Base (web) Study

• Revealed energetic pathways and constraints 

• Revealed effects of management actions & 

mechanisms

What went right:
Food Base (web) Study

• Revealed energetic pathways and constraints 

• Revealed effects of management actions & 

mechanisms

• Leveraged resources & synergistic efforts

What went right:
Food Base (web) Study

Where it lacks:
Food Base (web) Study

• Connection of food web energetics to population 

dynamics (e.g., recruitment) of key fish species

Where it lacks:
Food Base (web) Study

• Connection of food web energetics to population 

dynamics (e.g., recruitment) of key fish species

• Limited to Colorado River mainstem

Where it lacks:
Food Base (web) Study

• Connection of food web energetics to population 

dynamics (e.g., recruitment) of key fish species

• Limited to Colorado River mainstem

• One-time (3 yrs) study

Where it lacks:

Dam operations
Dam operations
River Food Web

Dam operations
River Food Web

Natural Dam operations

phenomena
River Food Web

Natural Dam operations

phenomena
River Food Web

Natural Dam operations

phenomena
Extreme Sampling Challenges!
Long-term Monitoring Plan

• Sampling frequency

• Ecosystem metabolism

• Organic matter

• Invertebrate drift

• Emergent insect production

• Benthic communities
Long-term Monitoring Plan--

Sampling Frequency

Proposal: 10X / year for most components
Long-term Monitoring Plan--

Sampling Frequency

• For many ecosystem components, rationale for 

sampling frequency appears to be convenience. 

Proposal: 10X / year for most components
Long-term Monitoring Plan--

Sampling Frequency

• For many ecosystem components, rationale for 

sampling frequency appears to be convenience. 

• What frequency is most synchronous with system 

dynamics & management activities?

Proposal: 10X / year for most components
Long-term Monitoring Plan--

Metabolism & Organic Matter

Proposal: Metabolism (daily), organic matter (10X / yr) 
Long-term Monitoring Plan--

Metabolism & Organic Matter

• How will monitoring data for organic matter 

concentrations & primary production be used & 

interpreted?

Proposal: Metabolism (daily), organic matter (10X / yr) 
Long-term Monitoring Plan--

Metabolism & Organic Matter

• How will monitoring data for organic matter 

concentrations & primary production be used & 

interpreted?

• How will basal resource dynamics/trends be linked 

to upper trophic levels?

Proposal: Metabolism (daily), organic matter (10X / yr) 
Long-term Monitoring Plan--

Invertebrate Drift

Proposal: 5 min samples from margin & thalweg
Long-term Monitoring Plan--

Invertebrate Drift

• Still unknowns about methods, e.g., sampling duration 

(hrs vs mins) & location (margin vs. thalweg)

Proposal: 5 min samples from margin & thalweg
Long-term Monitoring Plan--

Emergent Insects

Proposal: Sticky traps deployed continuously 
Long-term Monitoring Plan--

Emergent Insects

• Question whether proposed approach is feasible

Proposal: Sticky traps deployed continuously 
Long-term Monitoring Plan--

Emergent Insects

• Question whether proposed approach is feasible

• Recommend pilot efforts at accessible sites

Proposal: Sticky traps deployed continuously 
Long-term Monitoring Plan--

Benthic Communities

Proposal: Annual sampling in select (<20% of) habitats
Long-term Monitoring Plan--

Benthic Communities

• Consider basket or Hester-Dendy type sampling for 

aquatic insects

Proposal: Annual sampling in select (<20% of) habitats
Long-term Monitoring Plan--

Benthic Communities

• Consider basket or Hester-Dendy type sampling for 

aquatic insects

• How will periodic benthic community data be linked 

to process measurements? Fish populations?

Proposal: Annual sampling in select (<20% of) habitats
Conclusions
Conclusions

• Food web study was well executed, cost effective, 

and provided groundbreaking new and 

management-relevant information
Conclusions

• Food web study was well executed, cost effective, 

and provided groundbreaking new and 

management-relevant information

• Proposed monitoring plan is understandably 

complex, and requires additional analysis of existing 

data and pilot efforts
QUESTIONS? Questions?