U.S. Department of the Interior

U.S. Geological Survey

What do we know after two years of the 

brown trout incentivized harvest program?

Brenna Deerberg1, Josh Abbott1, and Lucas Bair2

1Arizona State University

2U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center 

Glen Canyon Dam Adaptive Management Program 

Annual Reporting Meeting, January 24-25, 2023

This information is preliminary and is subject to revision. It is being provided to meet the need for timely best science. The information is provided on the condition that 

neither the U.S. Geological Survey nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

U. S. Department of Interior

U.S. Geological Survey
Project Background

• Project J. Socioeconomic research in the Colorado River Ecosystem

– J.2. Brown trout incentivized harvest

• Cooperators: Arizona State University, Northern Arizona University

• LTEMP Resource goals: Humpback Chub. Meet humpback chub 

recovery goals, including maintaining a self-sustaining population, 

spawning habitat, and aggregations in the Colorado River and its 

tributaries below the Glen Canyon Dam.

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Brown trout incentivized harvest

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Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Incentive structure

Date Item Award amount

Nov. 2020 Implementation $25/fish

March 2021 Increase in base $33/fish

$33/fish, $50 for 3rd fish, $50 PIT tagged fish, April 2021 Bonanza $300/sonic tagged fish, $500/most, $250/best video

May 2021 Base $33/fish 

Augusts 2021 Increase in base $33/fish and $50 for 3rd fish

September 2021 Increase in base $33/fish, $50 for 3rd fish, $300 for PIT tagged fish

$33/fish, $50 for 3rd fish, $300 for PIT/sonic tagged Dec 2021- Jan 2022 Bonanza fish, $500 for most, $500 for largest 

February 2022 Base $33/fish, $50 for 3rd fish, $300 for PIT tagged fish

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Preliminary Information-Subject to Revision. Not for Citation or Distribution.
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GCNRA angling videos

Preliminary Information-Subject to Revision. Not for Citation or Distribution.
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Preliminary Information-Subject to Revision. Not for Citation or Distribution.

Fall 2020 Spring 2021 Fall 2021 Spring 2022 Fall 2022

Total monthly harvest
Total brown trout harvest

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harvest incentive

trips catch per 

trip

retention 

rate

brown trout 

harvested

Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Margin 1: Total trips

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We fail to reject the hypothesis that the introduction of 

the harvest incentive and any of its associated price 

levers had no effect on daily trip-taking to Lees Ferry.

Preliminary Information-Subject to Revision. Not for Citation or Distribution.

Monthly raw distributions of daily Lees Ferry fishing trips by unguided 

anglers. The red vertical line marks the March 2021 treatment date.
Margin 2: Catch-per-trip

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We reject the hypothesis that the program had no effect 

on brown trout catch and suggest that the overall 

program effect on this margin was negative.

Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Margin 3: Retention rate

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The proportion of unguided anglers who retained none, some, or all their caught brown trout by 

month. The break in the graph indicates the program kickoff with the potentially treated month 

November 2020 - February 2021 removed.

We fail to reject that the program kick-off and bonanza events had no 

effect on the percent of caught brown trout that unguided boat anglers 

retained, it appears that the adoption of the $50 bonus for every third 

fish in August 2021 increased brown trout retention rates.

Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Conclusion

• Our models predict an annual harvest of 284 brown trout in the 

first year and that 196 of those would have been harvested 

without the program. 

• Additional survey research may identify how program design may 

drive the ‘one angler’ effect and what that means for program 

efficacy and cost-effectiveness.

• The Program did not have a negative impact on the fishery’s 

rainbow trout stock, as catch and retention rates of rainbow trout 

were unaffected.

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Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Mail survey data collection

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Incentive structure

Date Item Award amount

Nov. 2020 Implementation $25/fish

March 2021 Increase in base $33/fish

April 2021 Bonanza $33/fish, $50 for 3rd fish, $50 PIT tagged fish, 

tagged fish, $500/most, $250/best video

$300/sonic 

May 2021 Base $33/fish 

Augusts 2021 Increase in base $33/fish and $50 for 3rd fish

September 2021 Increase in base $33/fish, $50 for 3rd fish, $300 for PIT tagged fish

Dec 2021- Jan 2022 Bonanza $33/fish, 

$500 for 

$50 for 3rd fish, $300 for PIT/sonic tagged fish, 

most, $500 for largest 

February 2022 Base $33/fish, $50 for 3rd fish, $300 for PIT tagged fish

February 2023 Proposed Base $33/fish, $50 for 3rd fish, $15 for PIT tagged fish, 

fish greater than 20 inches

$300 for 

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Preliminary Information-Subject to Revision. Not for Citation or Distribution.
Questions? 

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