Fish Community Compositio

0%

10%20%30%40%50%60%70%80%90%

100%

1958

1964-68

1968-1972

1985

Time Period

Proportion

Trout Native Fish Ch

Leibfried and Zimmerman 1994
The Present Fish Community in Gr

2000-2001 Observed Species Composition in the Color

Electrofishing and Netting Methods

Salmonids

80%

Bluehead

Sucker

1%

Flan

S

Centrarchids 

0.1%

Ictal

0.3
Recent Trends in Salmonid Ab

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
Recent Recruitment Trends in 

Colorado River Population of Hum

Abundance of Age-1 Humpback Chub b

0

10,00020,00030,00040,00050,00060,00070,00080,000

1989 1990 1991 1992 1993 1994 1995 

Brood Year

Abundance 
Recent Recruitment Trends in 

Colorado River Population of Hum

Tagage Estimates of Age-2 HBC Recruitment by Bro

0

5,000

10,00015,00020,00025,000

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

Brood Year

Abundance 
The Future Grand Canyon Fish 

•Humpback Chub???•What is driving the apparent long-term downturChub recruitment?

•Interaction with Non-Native Fishes

• Lassuy 1995, Marsh and Douglas 1997, Tyus an

•Asian Tapeworm•Little Colorado and Colorado River Hydrolo•Other Factors?

?
The Future Grand Canyon Fish 

Projected Abundance of Humpback 

Assuming 1998 Recruitment Persi

0

100020003000400050006000700080009000

1993

1995

1997

1999

2001

2003

2005

2007

Year

Abundance

>15Age Age 
Scenario 1. GCMRC Recommended Water Year 2002-03 

0

5,000

10,00015,00020,00025,00030,00035,00040,00045,00050,000

Aug-02

Sep-02

Oct-02

Nov-02

Dec-02

Jan-03

Feb-03

Mar-03

Apr-03

May-03

Date

Discharge

ROD 

Flows

Tributary Sediment Input

Low Steady Flows to Retain Sediment. Could be low level ROD FlowsBHBF - 45,000 cfs. or higher Fluctuating Flows for 

Sediment Re-working and Disadvantaging Nonnative Fish Combined with Removal of Nonnative Salmonids in the LCR Reach

ROD Ope
Proposed Experimental Treat

?

•Manipulate (lower) the abundancerainbow and brown trout in theColorado River.

• Large Winter/Spring FlowFluctuations to limit rainbowtrout recruitment.•Mechanical removal of rainbowand brown trout in the LittleColorado River reach of theColorado River (RM 56-66)
Proposed Experimental Treat

•Mechanical Removal (electrofishing)of rainbow and brown trout in theLittle Colorado River reach of theColorado River (RM 56-66).

•6 trips/year during 2003-2005

•Mechanical Removal Objectives:

1.Can we reduce the abundance of

rainbow and brown trout in a 10mile reach of river (depletionabundance estimates, changes insize distribution).
Proposed Experimental Treat

•Mechanical Removal Objectives:

2. Evaluate piscivory as a

function of: predator species,predator size, prey size, preyabundance, predatorabundance.

3. Overtime, evaluate the

relationship between rainbowand brown trout abundance andhumpback chub recruitmentand survival.
Recent Trends in Salmonid A

Rainbow Trout Electrofishing Catch Rate

Fench Fault Reach (RM 25-35)

0

200400600800

10001200140016001800

1992

1993

1994

1995

1996

1997

1998

1999

2000

Year

CPUE (fish/10 hours

Brown Trout Electrofishing Catch Rate

Fench Fault Reach (RM 25-35)

02468

1012141618

1992

1993

1994

1995

1996

1997

1998

1999

2000

Year

CPUE (fish/10 hours
The Present Fish Community in Gr

2000-2001 Observed Species Composition in the Color

Electrofishing Methods

Ictalu

0.1

Centrarchids

0.2%

Flann

Su

Bluehead

Sucker

0.2%

Salmonids

90%
The Present Fish Community in Gr

2000-2001 Observed Species Composition in the Color

Netting Methods

Salmonids

46%

Humpback

Chub

19%

Speckled Dace

2%

Cyprinids

3%

Centrarchids

0.1%

Ictalurids

0.9%
Core Fish Monitoring Projects-

Ferry Trout• 4 annual monitoring trips to es

electrofishing CPUE, abundandistribution, and PSD.
Downstream Non-native Fish Mo

(primarily Salmonids and Carp)• 2 annual monitoring trips to es

electrofishing CPUE, abundandistribution, and condition. Depresence and distribution of alnative species.
LCR Humpback Chub mon

• 4 annual trips to estimate sprin

abundance, spring spawning afall recruitment form previous open population model to estimrecruitment and abundance uspresent PIT tag database
Downstream Native Fis

Monitoring

• 2 annual trips to estimate relative 

abundance (CPUE), size distribucondition (HBC, FMS, BHS). LoHBC recruitment (changes in sizdistribution and mark rate).
Approximate Catch of HBC per trip based on 4 boats fis

Analysis based on Catch rates observed from October 1Catch rates would likely be even lower if I had data sumthat we will be fishing (I.e. ~56 - 65).

Effort/trip (hours)HBC<200 HBC>=200 

Mean 320 11.94 0Median 320 5.16 0Minimum 320 0.00 0Maximum 320 89.15 5

CPUE/10 hour