Mechanical Removal of N

Fishes from the Colorad

within Grand Cany

Lew Coggins, Michael Ya

Lew Coggins, Michael Ya

Daniel Gwinn, and Clay Nel

Daniel Gwinn, and Clay Nel

USGS, Grand Canyon Monitoring and Re

USGS, Grand Canyon Monitoring and Re

1Arizona Game and Fish Depart

Arizona Game and Fish Depart
Preliminary Resu

Preliminary Resu

Subject to Peer Revi

Subject to Peer Rev

Revision Revision
Background and Mot

Background and Mot

Adult Humpback Ch

Adult Abundance (Age 4+)

1989

1990

1991

1992

1993

1994

1995

1996

0

2000400060008000

1000012000

In 2002, concern for the In 2002, concern for the 

downward trend in downward trend in humpback chub humpback chub abundance prompted abundance prompted experimental adaptive experimental adaptive management actions management actions including removal of non including removal of non

-

native fish native fish
Background and Moti

Background and Moti

 Jan 2002, AMWG directed GCMRC to de

Jan 2002, AMWG directed GCMRC to de

experimental flows: experimental flows: 



“In concert with RPA flows In concert with RPA flows for native fish durin

for native fish durin

that the GCMRC, in consultation with the TWG

that the GCMRC, in consultation with the TWG

experimental flows sequence that experimental flows sequence that tests hypoth

tests hypoth

of sediment. Report to AMWG in of sediment. Report to AMWG in April 2002 on 

April 2002 on 

sequence. sequence.

”

 Chief of GCMRC directs staff to design an 

Chief of GCMRC directs staff to design an 

address questions related to providing be

address questions related to providing be

of Sediment of Sediment AND Native Fish. Native Fish.

 What are the factors potentially influencin

What are the factors potentially influencin

population dynamics? population dynamics?

 Dam Operations Dam Operations Water temperature Water temperature Parasites Parasites Non

-native Fish (LCR and Mainstem) native Fish (LCR and Mainstem)

 Backwaters Backwaters
Background and Moti

Background and Moti

 What are the factors What are the factors likely influen

influe

fish population dynamics fish population dynamics that we 

that we 

ability to test ability to test 

?

 Dam Operations Dam OperationsWater temperature Water temperature Non

-native Fish (Mainstem) native Fish (Mainstem)
Background and Moti

Background and Moti

 February 2002, GCMRC proposes a 16 February 2002, GCMRC proposes a 16 year stud

year stud

related to providing better management of Sedime

related to providing better management of Sedime

Year Mechanical Removal Mechanical Removal Fluctuating Flows Fluctuating Flows Temperatu

Temperatu

1 XXX XXX

2 XXX XXX

3 XXX

4 XXX5 XXX

6 XXX

789 XXX XXX XXX???

10 XXX XXX XXX???

11 XXX XXX???

12 XXX XXX???

13 XXX XXX???

14 XXX XXX???

15 XXX???

16 XXX???
Objectives Objectives

 Evaluate Efficacy of Removing Non

Evaluate Efficacy of Removing Non

 To what extent can we remove n

To what extent can we remove n

from a large reach (17 km) of the 

from a large reach (17 km) of the 

River?

 Evaluate Effect of Nonnative Fish R

Evaluate Effect of Nonnative Fish R

Population Dynamics of Native Fish

Population Dynamics of Native Fish

 Will humpback chub recruitment 

Will humpback chub recruitment 

result of non result of non-native removal? native removal?
Methods Methods

-Study S

Study S
Methods Methods - Remov

Remov

 2003 to 2006 2003 to 2006 - 6 trips/year 6 trips/year

 Jan, Feb, Mar (Winter) Jan, Feb, Mar (Winter) Jul, Aug, Sep (Summer) Jul, Aug, Sep (Summer)

 Electrofishing Electrofishing

 4-5 depletion passes 5 depletion passes 

within each 500m site within each 500m site

 Euthanized all non Euthanized all nonnative fish native fish Live release of all Live release of all 

native fish, pit tagged native fish, pit tagged if TL>150mm if TL>150mm
Methods Methods – Removal Data 

Removal Data 

 Constructed abundance estimates fo

Constructed abundance estimates fo

using a Hierarchical using a Hierarchical Bayes Removal 

Removal 

et al. 2005). et al. 2005).

 Assumed that Assumed that site-specific captu

specific captu

is drawn from a common Beta dist

is drawn from a common Beta dist

 Prior on capture probability. Prior on capture probability.

 Assumed that Assumed that site-specific abund

specific abund

from a common Poisson distributio

from a common Poisson distributio

 Prior on abundance. Prior on abundance.

 Model based aggregation of between 

Model based aggregation of between 

 Allows sites with high measuremen

Allows sites with high measuremen

informed or informed or “shrunk” towards the c

towards the c
0.0 0.1 0.2 0.3 0.4 0.5

A-01

A-02

A-03

A-04

A-05

A-06

A-07

A-08

A-09

A-10

A-11

A-12

A-13

A-14

A-15

A-16

A-17

A-18

A-19

B-01

B-02

B-03

B-04

B-05

B-06

B-07

B-08

B-09

B-10

B-11

B-12

B-13

B-14

B-15

B-16

B-17

B-18

B-19

C-01

E-01

E-02

E-03

E-04

E-05

E-06

E-07

E-08

Depletion Site

Capture Probability

Upstream Downstream 

Methods Methods – Hierarchical S

Hierarchical S
Methods Methods - Hoopnett

Hoopnett

 Hoopnet Hoopnet sampling sampling

 30 sites 30 sites-3 sets/trip 3 sets/trip Primarily used as a Primarily used as a 

measure of juvenile measure of juvenile humpback chub humpback chub relative abundance relative abundance
Results: Results:

Efficacy of Removal 

Efficacy of Removal 

for Non for Non-native F

native F
Results Results 

- Catch by N

Catch by N

Electrofishing Species Composition in the LCR Removal Reac

0

102030405060708090

100

Percent Composition by Number

Jan-03

Feb-03

Mar-03

Jul-03

Aug-03

Sep-03

Jan-04

Feb-04

Mar-04

Jul-04

Aug-04

Sep-04

Jan-05

Feb-05

Mar-05

Jul-05

Aug-05

Sep-05

Jan-06

Feb-06

Electrofishing Catch by Species in the LCR Removal Reach

0

500

10001500200025003000350040004500

Total Catch (# of Fish)
Results Results - Catch by 

Catch by 

Electrofishing Species Composition in the LCR Removal Reac

0

102030405060708090

100

Percent Composition by Mass

Jan-03

Feb-03

Mar-03

Jul-03

Aug-03

Sep-03

Jan-04

Feb-04

Mar-04

Jul-04

Aug-04

Sep-04

Jan-05

Feb-05

Mar-05

Jul-05

Aug-05

Sep-05

Jan-06

Feb-06

Electrofishing Catch by Species in the LCR Removal Reach

0

500

10001500

Total Catch (Kg)
Rainbow Trout Capture Probability in the Little Colorado River Removal 

0.0 0.1 0.2 0.3 0.4

Jan-03

Feb-03

Mar-03

Jul-03

Aug-03

Sep-03

Jan-04

Feb-04

Mar-04

Jul-04

Aug-04

Sep-04

Jan-05

Feb-05

Mar-05

Jul-05

Trip Date

Capture Probability

2003 2004 2005 

Results Results 

- Rainbow Trout Captur

Rainbow Trout Captur
Rainbow Trout Abundance in the Little Colorado River Removal Rea

0 2000 4000 6000 8000

Jan-03

Feb-03

Mar-03

Jul-03

Aug-03

Sep-03

Jan-04

Feb-04

Mar-04

Jul-04

Aug-04

Sep-04

Jan-05

Feb-05

Mar-05

Jul-05

Trip Date

Rainbow Trout Abundance

2003 2004 2005 

Results Results 

- Rainbow Trout A

Rainbow Trout A
Results Results- RBT Densit

RBT Densit

Rainbow Trout Density in the Little Colorado River 

0 50 100 150

Jan-03

Feb-03

Mar-03

Jul-03

Aug-03

Sep-03

Jan-04

Feb-04

Mar-04

Jul-04

Aug-04

Sep-04

Jan-05

Feb-05

Mar-05

Jul-05

Trip Date

Rainbow Trout Density (fish/500m/side)

2003 2004 2005 
Results Results- Immigration R

Immigration R

Net Immigration Rate to the Upstream Portion of t

-100

-50

0

50

100150200

Jan-Feb

Feb-Mar

Mar-July

July-Aug

Aug-Sep

Sep-Jan

Jan-Feb

Feb-Mar

Mar-July

July-Aug

Aug-Sep

Sep-Jan

Jan-Feb

Feb-Mar

Mar-July

JulyAug

Time Interval

Net Immigration Rate (fish/day)

2003 2004 2005 
Results: Results:

Indicators of Poss

Indicators of Pos

Native Fish Popul

Native Fish Popul

Response Response
Hoop Net Catch Rate of Humpback Chub Below the LCR Confluence (

01/01/98

04/01/98

07/01/98

10/01/98

01/01/99

04/01/99

07/01/99

10/01/99

01/01/00

04/01/00

07/01/00

10/01/00

01/01/01

04/01/01

07/01/01

10/01/01

01/01/02

04/01/02

07/01/02

10/01/02

01/01/03

04/01/03

07/01/03

10/01/03

01/01/04

04/01/04

0.00 0.05 0.10 0.15 0.20

CPUE (Fish/Hour)

Start Removal Project

Results Results 

- Humpback Chub Relativ

Humpback Chub Relativ
Length Distribution of Hoopnet Caught Humpbac

0.000 0.005 0.010 0.015 0.020 0.025

0 50 100 150 200 

Total Length (mm)

Density

Results Results 

- Humpback Chub Length 

Humpback Chub Length 
Length Distribution of Hoopnet Caught Humpbac

0.000 0.005 0.010 0.015 0.020 0.025

0 50 100 150 200 

Total Length (mm)

Density

Results Results 

- Humpback Chub Length 

Humpback Chub Length 
Length Distribution of Hoopnet Caught Humpbac

0.000 0.005 0.010 0.015 0.020 0.025

0 50 100 150 200 

Total Length (mm)

Density

Results Results 

- Humpback Chub Length 

Humpback Chub Length 
Length Distribution of Hoopnet Caught Humpbac

0.000 0.005 0.010 0.015 0.020 0.025

0 50 100 150 200 

Total Length (mm)

Density

Results Results 

- Humpback Chub Length 

Humpback Chub Length 
Length Distribution of Hoopnet Caught Humpbac

0.000 0.005 0.010 0.015 0.020 0.025

0 50 100 150 200 

Total Length (mm)

Density

Results Results 

- Humpback Chub Length 

Humpback Chub Length 
Electrofishing Catch Rate of Humpback Chub in the LCR Removal Reac

01/01/03

04/01/03

07/01/03

10/01/03

01/01/04

04/01/04

07/01/04

10/01/04

01/01/05

04/01/05

07/01/05

02468

CPUE (Fish/Hour)

Trip Date

Results Results 

- Humpback Chub Relativ

Humpback Chub Relativ
Results Results 

– HBC Length Dist

HBC Length Dist

-100

0 100 200 300 

0.000 0.005 0.010 0.015 0.020

Length Distribution of LCR Removal Reach Humpb

Total Length (mm)

Density
Results Results – HBC Length Dist

HBC Length Dist

-100 0 100 200 300 

0.000 0.005 0.010 0.015 0.020

Length Distribution of LCR Removal Reach Humpb

Total Length (mm)

Density
Results Results 

– HBC Length Dist

HBC Length Dist

-100

0 100 200 300 

0.000 0.005 0.010 0.015 0.020

Length Distribution of LCR Removal Reach Humpb

Total Length (mm)

Density
Results Results 

– HBC Length Dist

HBC Length Dist

-100

0 100 200 300 

0.000 0.005 0.010 0.015 0.020

Length Distribution of LCR Removal Reach Humpb

Total Length (mm)

Density
Electrofishing Catch Rate of Flannelmouth and Bluehead Sucker (95% 

01/01/03

04/01/03

07/01/03

10/01/03

01/01/04

04/01/04

07/01/04

10/01/04

01/01/05

04/01/05

07/01/05

10/01/05

0 5 10 15

CPUE (Fish/Hour)

Trip Date

Results Results 

- Sucker Relative Ab

Sucker Relative Ab
Results Results 

– FMS Length Dist

FMS Length Dist

0 200 400 

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Length Distribution of LCR Removal Reach Flannelm

Total Length (mm)

Density
Results Results 

– FMS Length Dist

FMS Length Dist

0 200 400 

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Length Distribution of LCR Removal Reach Flannelm

Total Length (mm)

Density
Results Results 

– FMS Length Dist

FMS Length Dist

0 200 400 

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Length Distribution of LCR Removal Reach Flannelm

Total Length (mm)

Density
Results Results 

– FMS Length Dist

FMS Length Dist

0 200 400 

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Length Distribution of LCR Removal Reach Flannelm

Total Length (mm)

Density
One Big Confounding Fac

One Big Confounding Fac

 Water temperature Water temperature

 Cold water temperature follo

Cold water temperature foll

installation of Glen Canyon 

installation of Glen Canyon 

known to inhibit vital rates fo

known to inhibit vital rates f

fishes. fishes.

Growth (Clarkson and Childs 

Growth (Clarkson and Childs 

Robinson and Childs 2001) Robinson and Childs 2001)

 Reproduction ( Reproduction (Hamman 1982 Swimming ability (Ward et al

Swimming ability (Ward et al

 Predation Risk (Ward and Bo

Predation Risk (Ward and Bo
One Big Confounding Fac

One Big Confounding Fac

 Water temperature Water temperature

 Cold water temperature in t

Cold water temperature in t

Glen Canyon Dam is known 

Glen Canyon Dam is known 

vital rates for native fishes vital rates for native fishes

Growth (Clarkson and Childs 

Growth (Clarkson and Childs 

Robinson and Childs 2001) Robinson and Childs 2001)

 Reproduction (Valdez and Ry

Reproduction (Valdez and Ry

 Swimming ability (Ward et al

Swimming ability (Ward et al

 Predation Risk (Ward and Bo

Predation Risk (Ward and Bo

Water Temperature near LCR Confluence
What Really Happe

What Really Happe

Year Mechanical Removal Mechanical Removal Fluctuating Fluctuating 

Flows

Temperature Co

Temperature Co

1 (2003) 1 (2003) XXX XXX “Naturally Eleva

Naturally Eleva

2 (2004) 2 (2004) XXX XXX “More Naturally 

More Naturally 

3 (2005) 3 (2005) XXX XXX “Even More Nat

Even More Nat

4 (2006) 4 (2006) XXX “Naturally Eleva

Naturally Eleva

5 (2007) (Non-natives in low abundance) natives in low abundance) “Reduced Temp

Reduced Temp

6 ???????? ???????? ???????? ???????? ???????? ????????

7 ???????? ???????? ???????? ???????? ???????? ????????

8 ???????? ???????? ???????? ???????? ???????? ????????

9 ???????? ???????? ???????? ???????? ???????? ????????

10 ???????? ???????? ???????? ???????? ???????? ????????

11 ???????? ???????? ???????? ???????? ???????? ????????

12 ???????? ???????? ???????? ???????? ???????? ????????

13 ???????? ???????? ???????? ???????? ???????? ????????

14 ???????? ???????? ???????? ???????? ???????? ????????

15 ???????? ???????? ???????? ???????? ???????? ????????

16 ???????? ???????? ???????? ???????? ???????? ????????
Conclusions Conclusions

 Non

-native Removal Efficacy native Removal Efficacy

 Mechanical Removal appears to Mechanical Removal appears to be an effective w

be an effective w

in the mainstem Colorado River. in the mainstem Colorado River. 

 Rainbow trout abundance reduced to near target le

Rainbow trout abundance reduced to near target le

abundance) in 2005 and 2006. abundance) in 2005 and 2006.

 Catch composition (by mass) of non Catch composition (by mass) of non-native fish red

native fish red

 Capture Probability ~10 Capture Probability ~10-20% / pass 20% / pass Low apparent immigration rate in 2005 Low apparent immigration rate in 2005-2006.

 Native Fish Trends Native Fish Trends

 Relative abundance assessments (catch Relative abundance assessments (catch

-rate) no 

rate) no 

recapture based stock assessments to determine 

recapture based stock assessments to determine 

 Assessment of 2003 cohort will require 2007 and 20

Assessment of 2003 cohort will require 2007 and 2

 However, there have been large increases in juve

er, there have been large increases in juve

relative abundance. Additionally, relative abundance. Additionally, flannelmouth flannelmouth andisplaying overall positive displaying overall positive trends in relative abund

trends in relative abund

 Relative influence of non Relative influence of non

-native fish versus tempe

native fish versus tempe
Predictions Predictions

 Rainbow Trout trends Rainbow Trout trends

 Very preliminary indications of rainb

Very preliminary indications of rainb

recovery both in Glen and Marble C

recovery both in Glen and Marble C

 Water Temperature? Water Temperature?

 Seager, R., Ting, M., Held, I., Kushn

Vecchi, G., Huang, H.-P., Harnik, NLau, N.-C., Li, C., Velez, J., and NaModel projections of an imminent trmore arid climate in southwestern NScience 316: 1181-1184.

 Other nonnative species Other nonnative species

 Smallmouth Bass, Crayfish, Others

Smallmouth Bass, Crayfish, Others