Boom-and-Bust Cycles in the 

Population of Rainbow Trout in Glen Ca

and Effects of Fall High Flow Experim

Josh Korman, Ecometric Michael D. Yard, GCM

Research, Vancouver, BC Flagstaff, AZ 

January, 2016 
Objectives of Natal Origins (NO) Pro

 Determine origin of rainbow trout near Little Colorado River (L

 Are trout at LCR coming from Glen Canyon? 

 Do actions that benefit tailwater fishery increase trout export with potenti

impacts on humpback chub near the LCR? 

 To address this question many trout were tagged in Glen Canyon 

 NO sampling in Glen Canyon has provided many insights abo

rainbow trout population and fishery 

 Dynamics and cause of boom-and-bust population cycles 

 Effect of Fall HFE’s on growth  Movement (Yard, next talk) 
-

Catch per Unit Effort (#/m)

0.05

1985

1986

1987

1988

1989Elevation

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

Boom-and-Bust Cycles in Abund

of Rainbow Trout in Glen Cany

2011 equalization N

0.25 O

O

0.20 2000 LSSF 2000 LSSF 0.15 

Reduced hourly variation 

0.10 

In flow 

1997-

equalizatio 1997 1998 

equalization 

2008 spring HFE 

CPE 1996 BH 1996 BHBF 

Å boom Æ Åbust Æ ÅboomÆ Åbu

AGF survey data 
Natal Origins Sampling Design in Glen C

Summer | Fall 

| 

Winter 

| Sp

Sep Oct Dec Jan Apr 

GCD 

Lees Ferry 

HFE 

Tags 1,000 5,000 5,000 1,000 1,000 Out 
Summary of Catch and Tagging Data 

Glen Canyon

Number Unmarked # of Trout 

Year of Trips Catch Tagged 

2011

1 12,241 11,429

2012

5 29,290 10,845

2013

6 27,092 13,644

2014

6 33,822 17,081

2015

6 26,108 17,682

2016

5 19,718 11,224

Total 29 148,271 81,905

Preliminary data, do not cite

# of T

Recap

49

1,11,822,11,72

7,29
Anatomy of a Boom-and-Bust C

Abundance (millions) 

High recruitment in 2011 due to equalization flows

Nt+1 = Nt 

·St + Rt 

0.6 0.4 0.2 0.0 

Size C

>=275225-274175- 224

1.2 1.0 

125-17475-124

0.8 

Apr12

Jul12

Sep12

Oct12

Dec12

Jan13

Apr13

Jul13

Sep13

Oct13

Dec13

Jan14

Apr14

Jul14

Sep14

Oct14

Dec14

Jan15

Apr15

Jul15

Sep15

Oct15

Dec15

Jan16

Apr16

Jul16

S

Higher mortality for larger size classes Initi

Rec

Preliminary data, do not cite
20 

Apr12-Jul12

Jul12-Sep12

Sep12-Oct12

Oct12-Dec12

Dec12-Jan13

Jan13-Apr13

Apr13-Jul13

Jul13-Sep13

Sep13-Oct13

Oct13-Dec13

Dec13-Jan14

Jan14-Apr14

Apr14-Jul14

Jul14-Sep14

Sep14-Oct14

Oct14-Dec14

Dec14-Jan15

Jan15-Apr15

Apr15-Jul15

Jul15-Sep15

Sep15-Oct15

Oct15-Dec15

Dec15-Jan16

Jan16-Apr16

Apr16-Jul16

Jul16-Sep16

Sep16Oct16Sprin

SummFall Winte

Annual and Season Variation in Trout G

2012 2013 2014 2015 2016 Preliminary data, do not cite 

15 10 5 0 -5 -10 

Growth (g/30 days)
 
Bottom-Up Vs. Top-Down Contro

of Trout Growth

Trout Biomass Consumption of drift 

- Top-Down 

Trout Growth = Intake (drift) - Loss

+ Bottom-Up 

Benthic Invertebrate Production 

Diel Flow H

Algae Variation 

Powell Nutrients Light 
Trout Growth Controlled by Bottom-

Growth (g/30 days) 

-10 -5 0 5 10 15 20 

Apr12-Jul12

Jul12-Sep12

Sep12-Oct12

Oct12-Dec12

Dec12-Jan13

Jan13-Apr13

Apr13-Jul13

Jul13-Sep13

Sep13-Oct13

Oct13-Dec13

Dec13-Jan14

Jan14-Apr14

Apr14-Jul14

Jul14-Sep14

Sep14-Oct14

Oct14-Dec14

Dec14-Jan15

Jan15-Apr15

Apr15-Jul15

Jul15-Sep15

Sep15-Oct15

Oct15-Dec15

Dec15-Jan16

Jan16-Apr16

Apr16-Jul16

Jul16-Sep16

Sep16-Oct16 Spring Summer Fall Winter Biomas

Variation in Prey Availability 

2012 2013 2014 2015 2016 

Preliminary data, do not cite 
Growth (g/30 days)
 

Effect of Fall HFEs on Growth (8” tr

Preliminary data, do not cite 

20

2012 2013 2014 2015 2016

15 HFE HFE HFE 

No HFE 10

50 

Sep12-Oct12Sprin

SumFall Wint

Apr16-Jul16

Jul16-Sep16

-5

Apr12-Jul12

Jul12-Sep12

Oct12-Dec12

Dec12-Jan13

Jan13-Apr13

Apr13-Jul13

Jul13-Sep13

Sep13-Oct13

Oct13-Dec13

Dec13-Jan14

Jan14-Apr14

Apr14-Jul14

Jul14-Sep14

Sep14-Oct14

Oct14-Dec14

Dec14-Jan15

Jan15-Apr15

Apr15-Jul15

Jul15-Sep15

Sep15-Oct15

Oct15-Dec15

Dec15-Jan16

Jan16-Apr16 -10
Effect of Fall HFEs on Condition (8” t

Growth (g/30 days) 

-10 -5 0 5 10 15 20 

Apr12-Jul12

Jul12-Sep12

Sep12-Oct12

Oct12-Dec12

Dec12-Jan13

Jan13-Apr13

Apr13-Jul13

Jul13-Sep13

Sep13-Oct13

Oct13-Dec13

Dec13-Jan14

Jan14-Apr14

Apr14-Jul14

Jul14-Sep14

Sep14-Oct14

Oct14-Dec14

Dec14-Jan15

Jan15-Apr15

Apr15-Jul15

Jul15-Sep15

Sep15-Oct15

Oct15-Dec15

Dec15-Jan16

Jan16-Apr16

Apr16-Jul16

Jul16-Sep16

Sep16-Oct16 

Spring Summer Fall Winter Condition (200 mm

HFE HFE No HFE HFE HFE 

2012 2013 2014 2015 2016 

Poor growth in spring & summer due to lower nutriGCD discharge combined with poor growth during due to HFE resulted in very poor condition by winte

Preliminary data, do not cite 
Jan14

Apr14

4-Jul14

Sep14

Oct14

Effect of Fall HFEs on Condition (12” 

Preliminary data, do not cite

2012 2013 2014 2015 2016

HFE HFE HFE No HF

20

Growth (g/30 days)
 

-30 -20 -10 0 10 

Apr12-Jul12

Jul12-Sep12

Sep12-Oct12

Oct12-Dec12

Dec12-Jan13

Jan13-Apr13

Apr13-Jul13

Jul13-Sep13

Sep13-Oct13

Oct13-Dec13

Dec13-

Jan14-

Apr1

Jul14-

Sep14-

Oct14-Dec14

Dec14-Jan15

Jan15-Apr15

Apr15-Jul15

Jul15-Sep15

Sep15-Oct15

Oct15-Dec15

Dec15-Jan16

Jan16-Apr16

Apr16-Jul16

Jul16-Sep16

Sep16Oct16 

Spring Summer Fall Winter Condition (300 m

HFE 
Effect of Growth on Surviv

Preliminary data, do not cite 
Effect of Survival on Abundance

Preliminary data, do not cite 

1.2 Survival x Yr 

2012 Survival 2013 Survival 

Apr12

Jul12

Sep12

Oct12

Dec12

Jan13

Apr13

Jul13

Sep13

Oct13

Dec13

Jan14

Apr14

Jul14

Sep14

Oct14

Dec14

Jan15

Apr15

Jul15

Sep15

Oct15

Dec15

Jan16

Apr16

Jul16

Sep16

Oct16 

Jul-Sep Abundance (millions) 

2011 

1.0 0.8 0.6 0.4 0.2 0.0 

Trip 

Large Very limited < 75 mm export <75 mm 

Very few trout >75 mm move downstream 

export
Effects of Growth on Maturation 

CF= 1.0 1.0 

0.9 

Preliminary data, do not cite 
Effect of Growing Conditions on Recru

Preliminary data, do not cite

50 100 150 200 

Recruitment ('000s) '12 

'13 

'14 

'15 

'16 

0 5 10 15

0 

Spring Growth (mm/30 days for 200 mm fis 

Availability of Prey (food)
Bottom-Up Control Driving Population 

Fish 

Population 

monitoring 

Top-Down

Control

Food Base

monitoring

Quality of 

Water

monitoring

Growth 

Benthic Invertebrate Production 

Reservoir Conditions 

GCD 

Survival of Recruitment 

Adults 

Sexual Maturation & Fecundity 

Current and Future Abundance 

Boom-and-bust cycles caused by occasional strong recruitments (due tfollowed by periods of reduced growth, survival, and recruitment driven availability (due low reservoir inflow and elevation) 

mark-recapture program 

Bottom-Up 

Control 
Introducing the RBT-100 Food Intake 

Trout Growth = Intake (drift) - Loss

Intake = Trout Growth + Losses 

Operating Instructions for RBT-100 

1. Catch trout, measure, weigh, tag and record information 2. Deploy RBT-100 instrument into environment (or -101 o3. Return to office and go about your daily business, allow

to sample over desired interval (integrated food availab

4. Retrieve RBT-100. Scan, measure, weigh, record and r5. >16,000 RBT-xxx’s recovered to date. Also see HBC-10

Caution. Some work at night may be required 
Potential Policy Implications

 Avoid boom-and-bust cycles to reduce trout export to LC

consistent catch rates and larger trout in the fishery: 

 Enhance food supply via ‘bug flows’ or fertilization (add liquid nitroge

as a mitigation for fluctuating flows and low reservoir elevation 

 Limit recruitment via Trout Management Flows (TMFs)  Do not implement fall HFEs in years when trout are in poor condition  Fertilize prior to conducting an HFE to mitigate negative effects 

 Critical uncertainties 

 Will TMFs be implemented & work? What years to implement (e.g.,  Will bug flows or fertilization increase food supply?  Does enhanced food supply increase or decrease extent of trout exp
Future Monitoring in Glen Canyon

 STAY ON THE ROAD TO LEARNING: Estimate growth, survival, recruitmen

by mark-recapture at time- scale that is fine enough to address GCD AMP qu

 Response of recruitment to a particular flow in one year (e.g. spring HFE, 2011 equ Seasonal effects of fall HFEs on growth  “Identify approaches to determine the root cause(s) of the unstable trout population 

question) 

 Measure export of trout from Glen Canyon to upper Marble Canyon (tagging not ne

 The current Catch-Per-Effort survey provides imprecise indices of recruitmen

 Useful for assessing trends in population over longer blocks of time (e.g. 5 yrs), but 

annual changes needed to address management questions 

 Growth is not estimated from CPE surveys but is needed to understand why recrui

are changing, and effects of fall HFEs. 

 Two choices for TWG: 

A. Keep asking current management questions and therefore continue with mark-reca

can address these questions. 

B. Ask much simpler questions restricted to long-term trends in status which can be a

CPE program. 
What Catch-per-Effort Surveys (CpE) Te

N = CpE/q (q=proportion of population 

Total Abundance in Glen Canyon (millions population status 

0.8 0.6 0.4 0.2 0.0 

low high low high

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014 

Year 

Preliminary data, do not cite 
Acknowledgements 

 Administrative support: Scott Vanderkooi, Ted Melis  GCMRC logistics: Carol Fritzinger, Seth Felder, and Dave Foste Sampling design and modelling: Charles Yackulic and Car Many boatmen, biologists, and technicians that assist

field work!