Uncertainty Regarding E

MLFF and Other ExperimActions on Fisheries Resin Grand Canyon

Lew

Coggins

Grand Canyon Monitoring and Research CenterJosh KormanEcometric Inc.
Recent Trends in Fishery R

Mainstem Electrofishing

Species C

2000-2001 O

bserved Species Composition i

n the Col

o

r

Elect

rofishing M

ethods

Ictal

u

0.1

Centr

a

r

chids

0.2%

Flann

S

u

2

Bluehead 

Sucker

0.2%

Sal

monids

90%
Recent Trends in Fishery R

Mainstem Netting (Tra

m

m

el and Hoop) Spec

2000-2001 O

bserved Species Composition i

n the Col

o

r

N

ettin

g M

eth

o

d

s

Sal

monids

46%

H

umpback 

Chub

19%

Speckled D

ace

2%

Cy

p

rinid

s

3%

Centr

a

r

chids

0.1%

Ictal

u

rids

0.9%
Recent Trends in Fishery R

 Lees Ferry

 Update by Bill Persons after lunch Overall Patterns

 Increase in abundance, particularly in m Increase in angler catch-rate, particular

1990’s

 Decrease in average size, and proportio Decrease in condition factor Cessation of stocking owing to adequat

reproduction
Recent Trends in Fishery R

Fence Fault Reach Trout Abu

R

ainbow Trout Ele

ctrofi

shing C

atch R

ate

Fench Fault R

e

a

ch (

R

M 2

5-3

5)

0

200400600800

10001200140016001800

1992

1993

1994

1995

1996

1997

1998

1999

2000

Ye

ar

CPUE (fish/10 hours)

Brown Trout Ele

ctrofi

shing C

atch R

ate

Fench Fault R

e

a

ch (

R

M 2

5-3

5)

02468

1012141618

1992

1993

1994

1995

1996

1997

1998

1999

2000

Ye

ar

CPUE (fish/10 hours)

FenceFence
Recent Trends in Fishery R

Little Colorado River Inflow Trout 

R

ainbow Trout Ele

ctrofishing C

atch R

ate

Little Colora

d

o Ri

v

er Re

a

c

h (

R

M 5

6 - 6

9)

0

10

0

20

0

30

0

40

0

50

0

60

0

70

0

80

0

90

0

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Ye

ar

CPUE (fish/10 hours)

Brown Trout Electrofi

shing C

atch R

ate

Little Colora

d

o Ri

v

er Re

a

c

h (

R

M 5

6 - 6

9)

05

101520253035

1990

1991

1992

1993

1994

1996

1995

1997

1998

1999

Ye

ar

CPUE (fish/10 hours)
Recent Trends in Fishery R

Little Colorado River Hoopnet

Species 

N

ati

v

e and N

o

n-n

ati

v

e S

p

e

cie

s C

o

m

posi

tio

n i

n Hoop

0%

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

100%

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 199

Humpback Chub Sp

eckl

e

d D

ace

Flannel

mouth S

u

c

ker

Blue
Recent Trends in Fishery R

Little Colorado River Hoopnet

Species 

No

n-n

ativ

e S

pecies Co

m

p

o

sitio

n in Hoop

n

e

t C

0%

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

100%

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 199

Minnow

s Catfishes

Plain

s Killifis

h Tr

o

uts
Recent Trends in Fishery R

Little Colorado River Humpback Chub 

0

5,000

10,00015,00020,000

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

19

Brood Y

e

a

r

Number of Recruits

0

2,0004,0006,0008,000

10,00012,00014,000

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

199

Ye

a

r

Adult Population Size 
Overall Trends during the ML

 Rainbow trout abundance increa

throughout the CRE

 Brown trout abundance increase

particularly in upstream (criticalLCR confluence and Fence Faul

 Humpback chub abundance and 

continued to decline

 LCR species composition remai

essentially static

 Items 1-3 are contrary to the exp

from the EIS

 Not a surprising result... reinforces 

active adaptive management.
Do We Know With Any Certainty W

These Patterns in Fishery Res

 Not really, can only speculate on  Why?

 Lack of experimental design Lack of contrast in Dam Operations

 Interim and Rod Flows for last 14 years 1996 BHBF and 2000 LSSF (and 2005 fa

insufficient duration to provide much of signal or to rule out a spurious trend cauncontrolled factor. Possible exception cohort in Lees Ferry, but spurious trend possibility.

 We would be in a much better positi

MLFF if there had been a 3-4 year blother operation (e.g., No Action, LSSponding

flows) mid-way through Ro

Implementation.
 Lees Ferry Speculations!!!

Became a selfsustaining fishery 

with multiple strong year classes increasing overall abundance.

Changes in annual 

volume likely had an overall affect on carrying capacity allowing fish to flourish in the midlate 1990’s and forcing an adjustment in early 2000’s.

Suggests 

management for a quality fishery should be tied to annual volumes.

R

eleases from Glen Ca

05

10152025

1965

1970

1975

1980

1985

Water Y

ear

Annual flow volume (million acre-ft)

Reservoir filling

Wet conditions;

 reservoir full

Dr
Speculations!!!

 Downstream Non-native Fish

 Salmonids demonstrating similar patt

Ferry with major period of expansion mid to late 1990’s

 If annual water volume affecting RBT 

locations, expect decreases in RBT a

 Brown trout? Increased water tempe

allow continued upstream expansion However, they could experience a declowered carrying capacity similar to r
Speculations!!!

 Humpback chub

 MLFF does not seem to have reverse

 However, we do not know if HBC would h

more, or the same under some other type suggests active adaptive management is 

 We do not know which of multiple fac

hypotheses) are drivers for HBC recrudynamics... see next talk

 From Korman et al. 2004

 “The interaction between habitat and ecosys

competition and predation remain highly uncquestions regarding the effects of dam operahumpback chub must be addressed by moniof critical population parameters to flow manconducted within a sound experimental desig