Effects of HFEs on Growth and Population Dynamics of 

Rainbow Trout in Glen Canyon and Marble Canyon

Natal Origins mark-recapture project (2012-2017)

Josh Korman, Ecometric Research, 

Vancouver, BC

Michael D. Yard, USGS, 

GCMRC, Flagstaff, AZ

AMWG Reporting Meeting, March 2018

Scott A. Wright, USGS, 

California Water Science 

Center, Sacramento, CA

Trout

Recruitment

Growth

Dynamics

(2018-2020

Glen Canyon

Only)
Acknowledgements

 Administrative and logistical support: Ted Melis, Scott Vanderkooi, Carol 

Fritzinger, Seth Felder, and Dave Foster

 Sampling design and modelling: Charles Yackulic and Carl Walters

 Supporting data: Ted Kennedy et al., Dave Topping et al., Bridget Deemer

 Field work: Thanks to the boatmen, biologists, and technicians!
Primary Publications from Natal Origins MarkRecapture Project or Data (2012-2017)

Rainbow Trout Growth and Population Dynamics (6) – Natal Origins Sampling Trips

 Korman, J., M.D. Yard, and T.A. Kennedy. 2017. Trends in rainbow trout recruitment, abundance, survival, and growth during a boom-and-bust cycle in a tailwater

fishery. Trans. Am. Fish. Soc. 146:1043-1057.

 Korman, J., and M.D. Yard. 2017. Effects of environmental covariates and density on the catchability of fish populations and the interpretation of catch per unit 

effort trends. Fish. Res. 189:18-34.

 Dzul, M.C., Yackulic, C.B., and J. Korman. 2017. Estimating disperser abundance using open population models that incorporate data from continuous detection 

PIT arrays. Can. J. Fish. Aquat. Sci. e-first article.

 Yard, M.D., Korman, J., Walters, C.J., and T.A. Kennedy. 2016. Seasonal and spatial patters of growth of rainbow trout in the Colorado River in Grand Canyon 

Arizona. Can. J. Fish. Aquat. Sci. 73:125-139.

 Korman, J, Yard, M.D., and C.B. Yackulic. 2016. Factors controlling the abundance of rainbow trout in the Colorado River in Grand Canyon in a reach utilized by 

endangered humpback chub. Can. J. Fish. Aquat. Sci. 73:105-124.

 Dodrill, M.D., Yackulic, C.B., Yard, M.D. and J.W. Hayes. 2016. Prey size and availability limits maximum size of rainbow trout in a large tailwater: insights from a 

drift-foraging bioenergetics model. Can. J. Fish. Aquat. Sci. 73: 759-772.

Humpback Chub (4) – Juvenile Chub Monitoring conducted during Natal Origins Sampling Trips

 Yackulic, C.B, Yard, M.D., Korman, J. and D.R. Haverbeke. 2014. A quantitative life history of endangerd humpback chub that spawn in the Little Colorado River: 

variation in movement, growth, and survival. Ecol. Evol. 4: 1006-100.

 Yackulic, C.B., Korman, J., Yard, M.D., and J. Dzul.. 2018. Inferring species interactions through joint mark-recapture analysis. Ecology. Early view article.

 Dzul, M.C., Yackulic, C.B., Korman, J., Yard, M.D., and J.D. Muehlbauer. 2016. Incorporating temporal heterogeneity in environmental conditions into a somatic 

growth model. Can. J. Fish. Aquat. Sci. 74:316-326.

 Finch, C., W. E. Pine, C. B. Yackulic, M. J. Dodrill, M. Yard, B. S. Gerig, L. G. Coggins, and J. Korman. 2016. Assessing Juvenile Native Fish Demographic 

Responses to a Steady Flow Experiment in a Large Regulated River. River Research and Applications 32:763-775
Outline

1. Conceptual model describing factors that control 

rainbow trout growth and abundance.

2. Effect of HFEs on rainbow trout growth in Glen Canyon

3. Effects of HFEs on rainbow trout growth and abundance 

in Marble Canyon
Conceptual Model for Rainbow Trout in 

Glen Canyon and Marble Canyon

Growth

Food (drift)

Reservoir Inflow

Flow Regime

from Dam

Survival of Recruitment

Adults

Sexual Maturation

& # of eggs/female

Current and Future Abundance

Long-Term 

Patterns in 

Climate

Nutrients

[P]

Top-Down

Competition

Effects

Reservoir Elevation

Operating Rules

turbidity Paria

Korman, J., M.D. Yard, and T.A. 

Kennedy. 2017. Trends in rainbow 

trout recruitment, abundance, 

survival, and growth during a 

boom-and-bust cycle in a tailwater

fishery. Trans. Am. Fish. Soc. 

146:1043-1057.
Trends in Growth and Condition (200 mm trout)

2012 2013 2014

Fat

Skinny

HFE HFE

Good

Poor

Before After Before After

Preliminary data 

subject to review, 

do not cite
Trends in Growth and Condition (200 mm trout)

2012 2013 2014 2015 2016 2017

Fat

Skinny

HFE HFE HFE no HFE HFE no HFE

Good

Poor

B A B A

B A

B A

Preliminary data 

subject to review, 

do not cite
Effect of Nutrients and Biomass on 

2012 2013 2014 2015 2016 

HFE HFE HFE no HFE HFE 

B A B A

B A

B A

do not cite

subject to review, 

Preliminary data 

Apr1

2-Jul 12 

Jul1

2-Sep1 2 

Se p1

2-0ct1 2 

Oct1

2-Dec 12 

Dec 12-Jan 13 

J an 13-Apr1 3 

Apr13-Jul 13 

J ul1

3-Sep1 3 

Sep 13-0ct1 3 

Oct1

3-Dec 13 

Dec 13-J an 14 

J an 14-Apr1 4 

Apr1

4-Jul 14 

Jul1

4-Sep1 4 

Sep 14-0ct1 4 

Oct1

4-Dec 14 

Dec 14-J an 15 

J an 15-Apr1 5 

Apr1

5-Jul 15 

Jul1

5-Sep1 5 

Se p1

5-0ct1 5 

Oct15-Dec 15 

Dec 15-Jan 16 

J an 16-Apr1 6 

Apr16-Jul 16 

J ul1

6-Sep1 6 

Sep 16-0ct1 6 

Oct16-Jan 17 

J an1

7-Apr1 7 

Mean Monthly Growth Rate (g) 

0 C,11 

.....__, 

-1111 

t-, 

I + 

..... 

0 

..... 

C,11 

• • • D 

Q.) :§: Tl (/) (/) :, - · Q.) "O G) :, - 3 ::::::! • .;., 1n :;:i a 

.... (D (O :[ 

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i'\.) 

0 

0 (1) ~ 

::::::! , :::0 0 

= ""O 

,-----~ 

S' OJ 

;. 

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-
Summary of HFE Effects on 

Rainbow Trout Growth in Glen Canyon

Fall-Winter 

Growth

HFE Years Non-HFE 

Years

Poor ’12 ’13 ‘14

Good ‘16 ’15

% Good Years 1 of 4 = 25% 1 of 1 = 100%

• Fall HFEs appear to reduce trout growth in fall and winter in Glen Canyon when assessed 

based on differences among years.

• BUT many limitations to this annual assessment:

• Only 1 non-HFE year (no replication)

• Poor growth immediately before HFEs occurred in 2 of 3 poor growth years (‘13, ‘14)

• Confounding of HFE effect with nutrients and competition

• Nutrients released from GCD and trout competition appear to have a bigger effect on growth 

than fall HFEs

• More years of mark-recapture data will allow us to quantify the likely modest effect of HFEs 

on trout growth. 

• Effects of HFEs on expanding macrophyte community in Glen Canyon and subsequent effect 

on food base and trout growth requires a much longer time period to evaluate.
Modelling Rainbow Trout Growth and Effects of 

HFEs in Marble Canyon

• Predict growth as a function of daminfluenced covariates based on a 

linear regression model fit to more 

than 10,000 growth observations

• Data available from 18 trip intervals 

(Apr ’12 - Sep ’16) in 5 reaches

• Covariates:

• Discharge

• Water temperature (metabolism)

• Turbidity – Feeding efficiency

• Light

• Competition (trout abundance)

• Drift (food)

• Most covariates influenced by GCD 

operations directly or through 

secondary effects
Very Modest Increases in Turbidity 

Substantially Reduce Trout Feeding Efficiency

Good

Poor Feeding Efficiency

Rosenfeld and Taylor, 2003 
0 100 200 300 400

-30

-20

-10

0

10

20

30

40

% Reactive Distance = 73

% Reactive Distance = 31

Apr-Jul 2013 (clear)

Jul-Sep 2013 (turbid)

Size-at-Release (g)

Growth (g/30 days)

Effect of Turbidity-Feeding Efficiency on Growth

(1% of available data used to fit model)

clear

turbid

Preliminary data 

subject to review, 

do not cite
Turbidity-Feeding Efficiency on Growth Observed in 

all Reaches Downstream of Paria in all Years

0 100 300

-30

-20

-10

0

10

20

30

40

II-2012

78

33

0 100 300

-30

-20

-10

0

10

20

30

40

II-2013

73

31

0 100 300

-30

-20

-10

0

10

20

30

40

II-2014

74

42

0 100 300

-30

-20

-10

0

10

20

30

40

II-2015

55

33

0 100 300

-30

-20

-10

0

10

20

30

40

II-2016

66

29

Size-at-Release (g)

Growth (g/30 days)

0 100 300

-30

-20

-10

0

10

20

30

40

III-2012

78

33

0 100 300

-30

-20

-10

0

10

20

30

40

III-2013

73

31

0 100 300

-30

-20

-10

0

10

20

30

40

III-2014

74

42

0 100 300

-30

-20

-10

0

10

20

30

40

III-2015

55

33

0 100 300

-30

-20

-10

0

10

20

30

40

III-2016

66

29

Size-at-Release (g)

Growth (g/30 days)

0 100 300

-30

-20

-10

0

10

20

30

40

IVa-2012

76

31

0 100 300

-30

-20

-10

0

10

20

30

40

IVa-2013

71

28

0 100 300

-30

-20

-10

0

10

20

30

40

IVa-2014

68

40

0 100 300

-30

-20

-10

0

10

20

30

40

IVa-2015

56

32

0 100 300

-30

-20

-10

0

10

20

30

40

IVa-2016

48

31

Size-at-Release (g)

Growth (g/30 days)

0 100 300

-30

-20

-10

0

10

20

30

40

IVb-2012

69

11

0 100 300

-30

-20

-10

0

10

20

30

40

IVb-2013

58

14

0 100 300

-30

-20

-10

0

10

20

30

40

IVb-2014

68

16

0 100 300

-30

-20

-10

0

10

20

30

40

IVb-2015

48

13

0 100 300

-30

-20

-10

0

10

20

30

40

IVb-2016

55

18

Size-at-Release (g)

Growth (g/30 days)

Preliminary data 

subject to review, 

do not cite
Intercept

-10

-5

0

5

10

15

QWtempTurbPMRLightSSL2Dtot

Covariate

Covariate Effect Size

Water

Temperature

Light Competition

(trout density)

Drift

(trout food)

Predictors of Growth in Weight

+'ve effect

No effect

‘-ve effect

Discharge Reactive Distance 

(feeding efficiency)

Growth 

Preliminary data 

subject to review, 

do not cite
Limiting Rainbow Trout Growth in Marble Canyon in

Winter and Spring will Reduce Condition and Abundance

200 mm

Preliminary data 

subject to review, 

do not cite

Poor winter-spring growth (low P)

High turbidity

Warm water 
Trout Population Collapsed Due to Very Low 

Condition Factor in Fall 2014

High abundance

System-wide collapse

due to poor condition

Preliminary data 

subject to review, 

do not cite

immigration

Local recruitment due to good condition in ‘12 and ‘13
Rapid Reduction in Rainbow and Brown Trout 

Abundance in Marble Canyon due to elevated Turbidity 

and Temperature and Low Phosphorous

2003-2006 mechanical removal study

Coggins et al. 2011. Nonnative Fish 

Control in the Colorado River in Grand 

Canyon, Arizona: An Effective Program 

or Serendipitous Timing?
Simulation of Turbidity Before and After 2013 HFE

2013

HFE

Preliminary data subject to review, do not cite

Paria

input

December 

volume

January 

volume

Paria

input
HFEs Reduce Turbidity after the High Flow

2013

HFE

Preliminary data subject to review, do not cite

Paria

input

December 

volume

January 

volume

Paria

input
HFEs Improve Trout Feeding Efficiency After 

2013 the High Flow

HFE

Preliminary data subject to review, do not cite

Paria

input

December 

volume

January 

volume

Paria

input
0 100 200 300 400

-30

-20

-10

0

10

20

30

40

% Reactive Distance = 73

% Reactive Distance = 31

Apr-Jul 2013 (clear)

Jul-Sep 2013 (turbid)

Size-at-Release (g)

Growth (g/30 days)

clear

turbid

Magnitude of Feeding Efficiency Change with and without 

HFEs similar to Pre- and Post-Monsoon Differences

Preliminary data 

subject to review, 

do not cite
Period of Clear Water after HFE De

Flow and Size of P

HFE

2012

Preliminary data s

volume

December 

volume

January 

input

Paria

Mean Daily Turbidity (FNUs) 

N W m 00 

0 0 0 0 0 0 0 0 0 0 

N ov-2012 -+---+---~ ;::::----+----+---+---+----+---+----+--Nov-2012 Nov-2012 

Dec-2012 Dec-2012 

Jan-2013 1u. 

Jan-2013 1 «..._ 

Feb-2013 1 J 

' - Feb-2013 

II 

__ll 

:' ' ~ ' ' 

' ' ' ' ' 

...:::::-

:..) 

' ' ' ' ' ' ' 

I 

2 

0 

:c 

'Tl 

m 

II) 

I 

; :E: 

' ' -· .... ' ' ' ' 

::J"' 

:c 

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II) 

I 

SJ. 

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n 
Predicted Effect of HFEs on 

Trout Growth in Marble Canyon

Very low condition attained

~1 yr. earlier under the 

‘without HFEs’ scenario

Preliminary data 

subject to review, 

do not cite

Large Paria sediment

Smaller Paria input in 2013

sediment

input in 2012
Estimated Change in Trout Abundance in Marble Canyon 

& below LCR without HFEs in ‘12 and ‘13

Estimated period of reduced 

trout abundance without ‘12/’13 HFE
With fewer HFEs

HFEs or TEFs (Tailwater Extension Flows)?

Paria Sediment. Use it for Beaches or Trout Control?

With frequent HFEs

tailwater location bigger tailwater = 

more trout at LCR
 Frequent HFEs clean the bed in Marble Canyon reduce turbidity 

 promote trout growth  help sustain high levels of trout 

abundance.

 The idea that turbidity has a strong influence on trout distribution in 

Grand Canyon, and that it can be used for trout control, is not new!

 Valdez and Ryel 1995; Melis et al. 2015; Yard et al. 2016; Korman et al. 2016.

 Turbidity curtain identified as best option for trout control in non-native EA 

(Runge et al. 2011)

 This study provides two new pieces of information (>10,000 growth 

observations and updated sediment model) that allows us to predict 

how GCD flow effect turbidity and trout in Marble Canyon.

Conclusions
HISTORY OF GCDAMP’s ASSESSMENT OF “CRe

TURBIDITY MANAGEMENT” TO CONSERVE NATIVE FISH

 Spring 2002 – HBC “911” Emergency Response – fish biologists report declining trend in adult HBC, the 

finding results in AMWG’s humpback chub ad hoc committee and consideration of a dozen experimental 

“management strategies” intended to arrest the decline and conserve humpback chub - one of which is to 

determine feasibility of importing “fine-sediment” from Lake Powell source areas to the CRe, near the Paria

River confluence w/ the Colorado River = turbidity cover for native fish when Paria does not contribute 

enough fines to meet a “200 FNU” condition in the main channel of Marble / Eastern Grand Canyons.

 2004-5 – Mechanical Removal project reports abrupt decline in rainbow trout throughout Marble and Grand 

Canyons at start of Year-3 MR treatment, and this step-change (shown in Coggins et al, 2011, Fig 7, p. 468) 

coincides with long string of Paria and 

 LCR floods / sediment inputs that occurred from mid-September 2004 through January 2005; including the 

largest winter Paria River flood in January 2005, since December 1966.

 2007 – Sediment Augmentation - Randle et al. (2007) deliver final technical feasibility report to AMWG, which 

declares that sources of fine sediment from the delta of Navajo Creek within Lake Powell could, in fact, be 

transported around Glen Canyon Dam & delivered to the CRe to manage turbidity of Marble and eastern 

Grand Canyons, but at a cost ranging from $150 (silt/clay only) – 400 (silt/clay/sand) million w/ annual 

maintenance of ~$9 million if an extra 1 Tg of sand were also to be augmented for sandbars as well. 

(estimated costs provide a means to value Paria River sediment provided as “ecosystem service” 

compliments of Mother Nature.

 Fall 2010 – Non-Native Trout Control EA / SDM Workshop – fish experts identify 19 options for controlling 

trout below Lees Ferry, with concept of “turbidity curtain” being rated the most effective long-term strategy 

(see Runge et al., 2011, p. 29, Table 3, hybrid option E [Sediment curtain (single strategies: 3b, 5e, 6, 13): #13 

is long-term strategy to emigration; #5 is the short-term strategy to emigration while infrastructure is being 

built; #3 is needed in short-term to reduce extant RBT population. Assumptions: RBT and BNT limit HBC 

recovery, Lees Ferry is the source of RBT, removal @ PBR or sediment curtain])
 Triggering criteria for a fall HFE could include trout abundance 

in Marble Canyon. If abundance is high and Paria sediment input 

is large, not conducting an HFE has the following benefits:

 Result in a system-wide (Paria-LCR and probably beyond) reduction in trout by 

partially restoring natural turbidity regime.

 Reduce hydropower losses.

 Reduce reliance on mechanical removal and other lethal approaches to trout 

control like Trout Management Flows (+ for tribes, fisherman, cost).

 Increase probability for spring-timed HFEs

 modify sediment accounting period.

 May be beneficial for trout and food base in Glen Canyon

 Create beaches just prior to main boating season.

 We have already implemented such a “Do No Harm” approach for 

fall HFEs (green sunfish in 2015).

Implications for Management
 Improve calibration of shifting rating curve sediment 

transport model (Wright).

 Quantify effect of turbidity on drift in Marble Canyon.

 Current estimate of trout growth reduction without HFEs is likely too 

low because it assumes higher turbidity does not reduce invertebrate 

biomass (Yackulic/Deemer/Kennedy).

 Model net effect of reduced trout abundance and higher 

turbidity on Humpback Chub at the LCR (Dzul/Yackulic).

 Need to improve trout monitoring in Marble Canyon if 

managers decide to use trout abundance as one of the HFE 

triggers

Future Work