Grand Canyon Monitoring and Research Center (GCMRC)

Fish Monitoring Program (FMP) – Protocol Evaluation Panel (PEP)

8–17 May 2009

A Draft Summary of Recommendations

Institutional

Recommendations

1. In most cases the monitoring programs are beyond the experimental stages and

considerable experience and data have been acquired. GCMRC should now be able to

develop a standardized framework for archiving data and reporting of monitoring results for

the key program elements.  This structure would allow data and results from individual

contract reports and to be synthesized and organized to report on the CMINs and

management objectives.  Maximum success of this approach depends on full participation

by all cooperators and researchers working in the system.  Currently there seem to be some

impediments (both real and perceived) to timely and complete data sharing among some

cooperators.  These impediments should be identified and steps taken to alleviate them.  

For example, the USGS critical review process overly jeopardizes partnerships and

cooperative relationships with other Department of Interior agencies and slows the

response time of GCMRC.  In some cases formal agreements such as Memoranda of

Understanding may be useful mechanisms to circumvent interagency policy conflicts (e.g.,

among sister agencies under the DOI).

2. Any effort to recover an endangered species must by necessity take a long‐term view.  

Numerous lines of evidence suggest that the Colorado River System will undergo substantial

changes over the next 50 years and beyond, both natural and anthropogenic, that will affect

key characteristics of the system, particularly water availability and temperature.  

Development of management strategies for system conditions that occur or can be created

currently, but that will no longer exist or be feasible several decades from now, will provide

little or no long‐term benefit.  We recommend that the AMWG and GCMRC convene a

group of experts to advise them on the likely future trends in conditions that will affect the

Colorado River system (e.g., changes in temperature and precipitation, water withdrawals

and diversions, reservoir levels, etc.) and use that information to identify the probable

bounds on management options that will be feasible in the future.  Even if (perhaps

especially if) those options are different than what seems optimal today, it would make

sense to begin testing management scenarios now that are suited to conditions in the long‐

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term in order to be prepared when those changes occur, rather than managing to avoid

risks now that are going to become highly likely in the future.   

3. Successful adaptive management requires that the magnitude and duration of management

manipulations be sufficient to generate an effect size in the variable(s) of interest that can

be detected by ongoing monitoring efforts and differentiated from natural variations.  

Despite the size and complexity of the Grand Canyon system and the extraordinary logistical

challenges to sampling, in many respects the rigor of the fish population monitoring

program in the Grand Canyon is unprecedented.  Coupled with this monitoring effort, the

initial 16‐year plan to manipulate predation pressure, temperature and flow in four‐year

blocks seemed likely to meet these criteria for success.  Even though drought‐induced

temperature increases occurred simultaneously with the predator removal treatment,

modifications to the long‐term plan could still impose treatments of sufficient magnitude

and duration to be informative in parsing the effects of these key variables on the system. It

is imperative that all partners act in consultation and cooperation with each other to

maintain an effective adaptive management strategy.  Otherwise, even the most accurate

and precise monitoring program will have little chance of identifying with confidence the

ultimate, or even proximate, mechanism(s) driving observed changes.  We recommend that

the AMWG members participate in a Bayesian Belief Network exercise, or similar effort, to

solidify their goals and reach consensus on how best to achieve them, in a way that takes

into account their disparate individual needs, concerns and responsibilities.  

Lee’s Ferry Trout Monitoring Program

Recommendations

1. Recast management objectives as angling catch rate, rather than absolute abundance, to

frame the management program more directly in relation to the current catch‐and‐release

angling fishery.  If the fishery develops into a trophy fishery (e.g. through flow regulation),

management objectives can be recast to better reflect a harvest‐based fishery (e.g. catch or

harvest of trophy‐sized trout).

2. Retain the creel survey to monitor annual fishery performance and angler satisfaction in

relation to the revised management objective.  Under the current catch‐and‐release fishery,

angling catch rate is the best metric for monitoring fishery performance.  If the nature of

the fishery changes, alternative angler‐based metrics may be required.  

3. Evaluate the effect of reducing electro‐fishing effort from 3–4 trips per year to 1‐2 trips per

year and eliminating the current fixed sites from the survey design to provide an index of

trout population density based on random sites only.  Effort to sample fixed sites can be

redirected to surveillance for non‐native fishes at likely locations (e.g., the ‘carp pond’,

location of previous smallmouth bass catches, etc.) and increasing the number of random

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sites within a trip. The power analysis suggests that reducing the sampling effort by one half

would have only small impact on precision. Metrics from this part of the survey provide a

frame of reference for trout in downstream reaches and a means by which to evaluate the

degree to which trout migrate downstream.  Growth rate can be estimated from ongoing

age estimation, rather than tag‐recapture data. More use of age information is

recommended to develop year‐class strength indicators.

4. Monitoring age‐0 trout habitat use and movement is not routinely needed because the

electro‐fishing survey provides a direct index of pre‐recruit trout density.  Similarly, redd

counts are not needed because the electro‐fishing survey provides a direct index of adult

trout density. This program’s strength is in evaluating the impacts of flow manipulations on

early life history, and could be reinstated to for specific flow tests.

LCR Native Fish Monitoring Program

RECOMMENDATIONS

1. There is now sufficient information and experience with the LCR HBC population to develop

an assessment framework. This framework would identify the information needs and

analysis required for managers to assess the state of the population relative to

management objectives. The framework would then provide guidance to the various

programs on the types of information needed from the annual reports, and would house all

of the key information in one annual report. Typically, assessment frameworks are peer‐

reviewed; however the annual updates are not, unless they deviate significantly from the

approved process.

2. In the context of the assessment framework evaluate the spring and fall hoop netting

programs to assess the necessity of conducting both surveys.  The objective of the fall

survey is to provide an index of sub‐adult abundance; however, it appears that spring hoop

netting also provides a relative index of sub‐adult abundance as the spring length frequency

data mimics the length frequency data from the previous fall.  The inclusion of the fixed PIT

tag array may alleviate the need for fall monitoring. Assessment of the hoop netting

program should consider how reducing sampling effort affects the number of newly tagged

fish, particularly in smaller size classes.   

3. Similarly, compare the spring random hoop net data to the fixed site 1200 meter hoop net

data.  Although the 1200 meter data is a valuable long‐term series, it may be redundant to

the ongoing spring hoop netting. These two programs should be evaluated by comparing

catches in the 1200 meter program to data from the lower sections of the FWS program.   

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4. Expand the fixed PIT tag antenna array to span the entire channel and consider deploying

antennas at two locations.  Spanning the entire channel assists in estimating capture

probability and having two antennas will allow determination of direction of movement.   

The PIT tag array may allow detection of movement pathways and the habitats used for

migration or movement.   The array may also inform the mark‐recapture estimates of the

spawning population by better describing the timing of the spawning migration.   

5. Reduce the frequency of ASMR updates from annual to every 3‐5 years, unless trends in

field data warrant a formal reassessment.  Under the aforementioned assessment

framework recruitment can be monitored with empirical catch per unit effort of fish less

than 150 mm TL.  The LCR adult abundance can be tracked using the mark‐recapture

estimate.  

6. ASMR estimates of recruitment do not match hoop net catch rates because of age

estimation error in the ASMR.  Body parts from the HBC being collected in the nearshore

ecology program should be used (e.g. anal fin rays, scales, and otoliths) for age verification.  

Hopefully, verification would allow future non‐lethal sampling for age estimation.  Age

estimates from fish tagged at small size (young “known” age) and recaptured over a wide

range of years at liberty should be compared for age validation. It may be possible to

increase the sensitivity of the ASMR recruitment index by using age information in

combination with the proposed tagging of smaller fish.

7. Management objectives for Chute Falls and other translocations should be specified in

measurable terms to guide monitoring and reporting.  The panel could not comment on

current monitoring activities with the information available.  

Mainstem Colorado River Monitoring Program

Recommendations

1. Monitoring trends in relatively abundant species throughout the mainstem, and also

detecting the occurrence of rare species, would be best served with a two‐pronged

approach.  The current stratified random electrofishing survey should be continued to

provide information on trends and distribution of relatively abundant native and non‐native

species.  However, effort could likely be reduced and still provide adequate information.  

This extensive approach needs to be complemented by a second strategy intended to

detect rare species, such as more intensive sampling using a variety of passive and active

gears at a smaller number of fixed surveillance locations where potentially detrimental non‐

native species are most likely to be found.  This sampling component can also include

locations where more detailed information on native species is warranted (e.g., known HBC

aggregations).  Taken together, these two sampling strategies address a range of monitoring

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goals, each to varying degrees (Table 1), and in combination address many of the questions

posed by the TWG.

2. Evaluate the impacts of reducing river‐wide electrofishing from 2 trips to 1 trip per year.

The primary goal of the stratified random electro‐fishing survey is to track general changes

in distribution and relative abundance of the trout populations and other species that are

captured by this gear. A single trip currently yields 350‐450 samples along 360 km of river,

which is a relatively high rate of sampling.  An annual CV (for trout at least) of 10% is

probably more precise than is really needed, especially for the longer‐lived species that are

unlikely to change in abundance significantly year to year. Existing data could be used to

evaluate what would be lost by a reduction in sampling intensity.  

3. Consider adding a targeted sampling program at likely locations for non‐native species

colonization (e.g. above Lake Mead, below Lake Powell, and stream mouths, springs, below

large rapids). This program would deploy a suite of additional sampling gears, such as

trammel nets, hoop nets, minnow traps, angling, set‐lining, seining, and back‐pack electro‐

fishing (these sites could also be sampled by boat electro‐fishing during the stratified

random electro‐fishing survey trip).  The primary objective is to detect colonization by non‐

native species and changes in their distribution in the mainstem that would not show up in

the stratified random electro‐fishing survey.  The proposed risk assessment for invasive

species could inform the locations, habitats and gear types that would be most effective. It

is unclear whether this effort needs to be conducted annually.

4. Designing a monitoring program for the non‐LCR HBC remains challenging. There may be

value in further refining the management objectives and CMINs to help clarify the

information needs. For example, if the focus is on the status of a few (2?) aggregations

outside of the LCR region, a focused sampling regime to assess abundance and recruitment

may be appropriate. This program could be tied (or alternated) with the targeted mainstem

sampling. Given the extensive experience with trammel and hoop net sampling from the

earlier surveys it should be possible to determine if the information that is generated by a

proposed sampling regime will satisfy the information needs.

5. Alternative means of sampling should continue to be pursued to identify the most efficient

means to detect new species and changes to the distribution and abundance of existing

species.
Table 1. Relative contribution of each mainstem sampling component to primary mainstem monitoring objecti

System‐wide trends in

established species(RBT, BRT, Carp, HBC,

FMS, BHS, others)

Detection of

rare/new species(non‐natives and

natives)

HBC juvenileabundance and size

at aggregations

HBC adult abundanceand size at

aggregations (andmovement)

Mainstem‐wide

stratified‐random EF

sampling

High Low Low or n/a?? Low or n/a?? (except

for possiblemovement)

Mainstem fixed‐site EF

sampling (HBCaggregations)

Low Med. High High 

Mainstem fixed‐site EF

sampling (potential non‐native sentinel

locations/hotspots)

Low High n/a n/a (except for

possible movement)

Mainstem‐wide multi‐gear fixed‐site sampling(HBC aggregations)

Low Med. High High 

Mainstem‐wide multi‐gear fixed‐site sampling(potential non‐native

sentinel hotspots)

Low High n/a n/a (except for

possible movement)

LCR confluence reachpredator‐removal EF

n/a (low?) Med. n/a n/a (except for

possible movement)

LCR confluence reachhoop netting

Low Low n/a n/a (except for

possible movement)

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