Non-Native Mechanical R

Operations in the Colorado 

Update and a Proposed Mo

Lew Coggins and Mike Yard

Southwest Biological Science Ce

Grand Canyon Monitoring and Resear
Presentation Outlin

• Background• Field Operations• Preliminary Results• Proposed Modification and Justificati
Objectives – What do we want to A

• Effect of Adult RBT and BNT in the L

Effect of Adult RBT and BNT in the L

Reach on the Population Dynamics of 

Reach on the Population Dynamics of 

Population. Population.

– Will humpback chub recruitment inc

Will humpback chub recruitment inc

non

-native removal? native removal?

• Efficacy of Mechanical Removal of A

BNT from the LCR Inflow Reach.

– To what extent can we remove non-n

a ~10 mile stretch of the Colorado R

• Rainbow and Brown Trout Diet Analy

Predation.

– What are non-native fish eating? Ho
16 Year Experimental 

16 XXX???15 XXX???

14 XXX XXX???

13 XXX XXX???

12 XXX XXX???

11 XXX XXX???

10 XXX XXX XXX???

9 XXX XXX XXX???876 XXX5 XXX4 XXX3 XXX2 XXX XXX1 XXX XXX

Year Mechanical Removal Fluctuating Flows Temperatu
Mechanical Removal Tri

• 6 trips per year (Jan, 

Feb, Mar, Jul, Aug, Sep) for 4 years.

• This design will allow:

– Estimation of initial trip 

abundance for the entire LCR Inflow Reach and cumulative reduction of non-native fish overtime.

– Estimation of 

immigration rate into the removal reach between trips.
Control Reach Field Operations –

• Control Reach (RM 44-52)

– Purpose is to evaluate 

changes in trout abundance and size distribution that are a result of factors other than mechanical removal (e.g. fluctuating flows)

– Each trip, 24 500m 

sampling units are randomly selected and electrofished to estimate catch-rate. 

– All RBT and BNT >= 

200mm are fitted with a flow tag to assess movement and estimate abundance.
Mechanical Removal Field Operatio

• Camp within the removal 

reach for 11 days

• 5 pass depletion between 

RM 56.2 – 65.7

• Each depletion pass takes 

2 days

– Day 1: Kwagunt to above 

60 mile rapid and below LCR confluence to below Salt Mine

– Day 2: Above 60 mile to 

Science Beach and below Salt Mine to Lava Chuar
Field Operations - Hoopnet

• Hoopnetting 

provides relative abundance estimates for juvenile HBC and other natives.

• Sampling conducted 

at 30 sites ~ 2 miles downstream from the LCR Confluence.
Field Operations - Diet Ana

• All non-native fishes captured 

in the removal reach have there stomach removed and preserved for later analysis.

• Two types of diet analysis 

will be performed:

– Presence/absence of fish 

remains in stomachs.

– Detailed analysis of diet of 

a sub-sample of rainbow trout and brown trout.

• Analyses for winter trips 

will be completed by midsummer.
Field Operations - Fish Disp

• Fish Disposal and Use

– Carcasses are disposed 

of by grinding them into a paste and placing them in 15 gal plastic barrels.
Field Operations - Fish Disp

• Fish Disposal and Use

– At the takeout, the 

barrels are delivered to a representative of the Hualapai Nation for use as fertilizer.
Preliminary Results – Removal R

Trip

Bluehead 

Sucker

Brown 

Trout

Channel 

Catfish

Common 

Carp

Fathead 

Minnow

Flannelmouth 

Sucker

Humpback 

Chub

R

January 8 86 80 17 185 26 

February 18 24 33 21 156 26 

March 11 20 1 22 8 89 13 

Total 37 130 1 135 46 430 65 

SPECIES
Preliminary Results – Removal Reach HBC Len

Length Frequency Distribution of HBC Captured in the 

02468

101214

50

75

100

125

150

175

200

225

250

275

300

325

3

Total Length

Number of Fish
Preliminary Results – Removal Reach RBT Ab

January Rainbow Trout Depletion Results

0

0.10.20.30.40.50.60.7

0 1000 2000 3000 4000 5000 

Cumulative Catch

CPUE (Fish/Min)

Starting Abundance Estimate Number Removed Ending Abundance Estimate Removal Efficiency 

February Rainbow Trout Depletion Results

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 500 1000 1500 2000 2500 

Cumulative Catch

CPUE (Fish/Min)

Starting Abundance Estimate =2Number Removed =1Ending Abundance Estimate =1Removal Efficiency =6
Preliminary Results – Removal Reach RBT Ab

Rainbow Trout Depletion Results March

0

0.000010.000020.000030.000040.000050.000060.000070.00008

0 500 1000 1500 

Cummulative Catch

CPUE (Fish/Min)

Starting Abundance Number Removed Ending Abundance ERemoval Efficiency 

Ending abundance estimate in March is 12% oabundance estimate in January.
Preliminary Results – Removal Reach RBT Len

Length Frequency Distribution of RBT Captured in the LCR 

0

100200300400500600

40-49

50-59

60-69

70-79

80-89

90-99

100-109

110-119

120-129

130-139

140-149

150-159

160-169

170-179

180-189

190-199

200-209

210-219

220-229

230-239

240-249

250-259

260-269

270-279

280-289

290-299

300309

Total Length Category

Number of Fish
Preliminary Results – Movement of Floy Tagge

First fish was a rainbow trout 15 inches long and hflannelmouth sucker lodged in it’s mouth.

N=1,323

Tag Location Recap Location Tag Date Recap Date Distanc46 mile 61.5 mile 1/15/2003 1/25/2003 15.5 mi50 mile 57.5 mile 2/13/2003 2/16/2003 7.5 mile48.5 mile 65.7 mile 2/13/2003 2/23/2003 17.2 mi49 mile 56.2 mile 2/13/2003 2/16/2003 7.2 mile50 mile 56.2 mile 2/13/2003 3/5/2003 6.2 mile46.5 mile 58.5 mile 1/16/2003 3/12/2003 12 mile51.1 mile 59.5 mile 3/10/2003 3/18/2003 8.4 mile41 mile 59.5 mile 3/10/2003 3/18/2003 18.5 mi
Preliminary Results – Predation
Preliminary Results – Predation
Preliminary Results – Hoopnet Catch Be

0

102030405060

Catch

Rainbow Trout 11 3 Brown Trout 20Fathead Minnow 10Bluehead Sucker 02Flannelmouth Sucker 33Hum

pback Chub 17 22 

Jan Feb 
Preliminary Results – Summa

• Non-native removal efforts appear to be much m

anticipated (88% reduction after 3 trips).

– Previous abundance estimates of RBT in the LCR in

over-estimated abundance by an order of magnitude 

– Immigration rates to the removal reach appear to be q

between trip comparisons and AGFD spring monitor

July Trip).

• Diet analyses still ongoing but results thus far in

piscivory by RBT and high rate of piscivory by 

• Hoopnet catches of HBC may indicate a habitat

by HBC following non-native removal. 

• Suggest defining a target treatment level of 10% 

to serve as trigger to postpone robust mechanicoperations until next evaluation trip (i.e. Januar
Presentation Outlin

• Background• Field Operations• Preliminary Results• Proposed Modification and Justificati
Proposed Modificatio

• Prompted by the greater than expected efficacy removal, we suggest expanding the geographic sremoval area downstream an additional 7 miles.

•Allow for a greater treatment magnitude.•Potentially result in greater ability to detect population dynamics as a result of non-nativ•Additional HBC monitoring opportunities.
Proposed Modificatio

Original Proposed 
Proposed Modificatio
Proposed Modification – W

• The motivation to modify the 

study is to increase the magnitude of the treatment in order to have the best chance of obtaining an unambiguous experimental result.

• Why will this help?

– Will affect a larger portion of the 

area where HBC and non-natives are believed to interact (Greater treatment magnitude, increased survival of juveniles).

– Will potentially provide a greater 

likelihood that the HBC stock assessment program will detect a change. 

– Will allow a more robust (time 

and area) sampling program of relative abundance (hoopnetting).
We will affect a larger portion of the area wh

natives are believed to interact (increased surv

• Current paradigm of LCR 

HBC juvenile recruitment is:

– Larval HBC emerge in the late 

Spring-early Summer.

– Some proportion of the 

juveniles rear in the LCR, the rest move to the mainstem Colorado (YOY during monsoon, 1+ juveniles during spring runoff).

– Most if not all of the juvenile 

HBC transported to the mainstem do not survive. Majority of recruitment coming from LCR rearing.
Will affect a larger portion of the area wher

natives are believed to interact (increased surv

• Key supporting 

observations

– Juvenile HBC 

abundance declines with distance from the LCR Confluence and time since last LCR flood (Valdez and Ryel 1995).
LCR INFLOW SUB-RE

012345

Jun-98

Jul-98

Aug-98

Sep-98

Oct-98

Nov-98

Dec-98

Jan-99

Feb-99

Mar-99

Apr-99

Sample Da

HOOPNET/MINNOW TRAP CPUE

(Fish/100 hrs)

Hopi-SaltLava ChuarTanner

Will affect a larger portion of the area wher

natives are believed to interact (increased surv

• Key supporting 

observations

– USFWS 

hoopnetting efforts regularly detected juvenile HBC near Tanner Rapid, but in lower abundance than closer to the LCR confluence (Gorman et al 2000).
Will affect a larger portion of the area wher

natives are believed to interact (increased surv

• Why are there fewer HBC 

juveniles below Lava Chuar?

– Above Palisades Fault, slower, 

bigger eddy complexes, talus.

– Below the Palisades Fault, 

river is shallower, faster, cobbles.

– Below Palisades Fault, nonnative abundance increases.– Are juvenile HBC less 

abundant below Palisades Fault because of habitat or cumulative predation response?
Proposed Modification – W

• The motivation to modify the 

study is to increase the magnitude of the treatment in order to have the best chance of obtaining an unambiguous experimental result.

• Why will this help?

– Will affect a larger portion of the 

area where HBC and non-natives are believed to interact (Greater treatment magnitude, increased survival of juveniles).

– Will potentially provide a greater 

likelihood that the HBC stock assessment program will detect a change. 

– Will allow a more robust (time 

and area) sampling program of relative abundance (hoopnetting).
Will potentially allow HBC stock 

programs a bigger signal to 

Simulated Recruitment

Recruitment Spike = 100% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

200

Year

Age 2 Abundance
Will potentially allow HBC stock 

programs a bigger signal to 

True versus Estimated Recruitment

Recruitment Spike = 100% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year

Age 2 Abundance
Will potentially allow HBC stock 

programs a bigger signal to 

True versus Estimated Recruitment

Recruitment Spike = 100% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

Year

Age 2 Abundance
True versus Estimated Recruitment

Recruitment Spike = 50% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year

Age 2 Abundance

Will potentially allow HBC stock 

programs a bigger signal to 
Will potentially allow HBC stock 

programs a bigger signal to 

True versus Estimated Recruitment

Recruitment Spike = 25% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

Year

Age 2 Abundance
Will potentially allow HBC stock 

programs a bigger signal to 

True versus Estimated Recruitment

Recruitment Spike = 12.5% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year

Age 2 Abundance
Proposed Modificatio

Will provide about the same geographic extent of predator free habitat in the mainstem as is available in the LCR.If need 1⁄2 as much recruitment out of the mainstem as the LCR, need to make abundant rearing habitat in the mainstem.
Will potentially allow HBC stock 

programs a bigger signal to 

True versus Estimated Adult Abundance

Recruitment Spike = 100% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

Year

Age 4+ Abundance

True versus Estimated Adult Abundance

Recruitment Spike = 50% Increase

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

Year

Age 4+ Abundance

True versus Estimate

Recruitment Spike 

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Age 4+ Abundance

True versus Estimate

Recruitment Spike 

0

100020003000400050006000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Age 4+ Abundance
Proposed Modification – W

• The motivation to modify the 

study is to increase the magnitude of the treatment in order to have the best chance of obtaining an unambiguous experimental result.

• Why will this help?

– Will affect a larger portion of the 

area where HBC and non-natives are believed to interact (Greater treatment magnitude, increased survival of juveniles).

– Will potentially provide a greater 

likelihood that the HBC stock assessment program will detect a change. 

– Will allow a more robust (time Will allow a more robust (time 

and area) sampling program of and area) sampling program of relative abundance (hoopnetting). relative abundance (hoopnetting).
Will allow a more robust (time and a

program of relative abundance (ho

•Additional hoopnetting sites will be established wremoval reach (Lava Chuar to Tanner, Tanner to U•Hoopnetting to infer relative abundance will be conon-native removal trip within each reach.•This will provide information about survival and gjuveniles within the downstream sections of remov•Provide additional information to infer the outcomwithout putting additional trips on the water.•Alternately, if we scale back on trips, we will not information on these local trends.
When Would The Proposed Remo

•Removal within the proposed reach would begin only if July efforts suggested that we had reached the target treatment level within the current removal section•Assuming July confirms that the target level is met:

•Removal within the proposed reach would proceed during August and September.•If all goes well, following September we will have achieved the target in all sections.
What would be the activities in 2004

•January 2004 would be a reconnaissance trip to conduct a depletion within the entire reach.•Pending those results, we would decide where further winter trips should concentrate.•July 2004 would inform the decision for further summer trips.
Indirect Benefits

•By catch of HBC in proposed depletion area should be much less than in original depletion area.•Lower visitation in proposed removal reach than in original removal reach leading to fewer interactions with park visitors.•Less effort in area deemed sacred to many Native Americans.

Recent Trends in Salmonid A

Rainbow Trout Electrofishing Catch Rate

Little Colorado River Reach (RM 56 - 69)

0

100200300400500600700800900

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

Year

CPUE (fish/10 hours)

Brown Trout Electrofishing Catch Rate

Little Colorado River Reach (RM 56 - 69)

05

101520253035

1990

1991

1992

1993

1994

1996

1995

1997

1998

1999

2000

2001

2002

Year

CPUE (fish/10 hours)