1

Lees Ferry Management Objectives and Monitoring Metrics

Presented to Glen Canyon Dam Adaptive Management Program Technical Work Group

June 30, 2004

Bill PersonsArizona Game and Fish Department

Reviewed by Barbara Ralston and Lew CogginsGrand Canyon Monitoring and Research Center

Presentation:

• Goal 4 and Management Objectives (MOs)• Brief history of fishery and MOs• Description of attributes for MOs• Description of metrics• Are we monitoring MOs and meeting MOs ? • Report card (SCORE?)• Other concerns• Take Home

Goal 4

• Maintain a wild reproducing population of rainbow trout above the Paria River, to the extent practicable and consistent with the maintenance of viable populations of native fish.

Management Objective 4.1

• Maintain or attain RBT abundance, proportional stock density, length at age, condition, spawning habitat, natural recruitment, and prevent or control whirling disease and other parasitic infections.

Management Objective 4.2

• Limit Lee’s Ferry RBT distribution in the Colorado River below the Paria River.

History of Fishery

• 1964 – 1971: Put-and-take Era• 1972 – 1978: Trophy Fishing Era• 1978 – 1984: Quality Fishing Era• 1985 – Present: Something Less Than 

Quality but Not Put-and-take.

LF Length Frequencies 1990, 1998

1990

1998

• Blue Ribbon Fishery (AZGFD)•Self sustaining

•Larger fish

•Higher catch rate

•Meet the desires of the angler

• Adaptive Management Program 2001 Strategic Plan

•Natural Reproduction

•Population of 100,000 age II+ trout

•Relative condition > 0.9

•18 inches by age III

LF Management Concepts 2001 Strategic Plan

2

Attributes/ Measures

• Abundance (100,000 Age II+)• Growth & Size Structure:

– PSD (not specified) – Length at age (18 “ by Age III)– Condition (Wr/ Kn = 0.90)

• Natural recruitment (yes)– Spawning habitat (available)

• Whirling disease (free)

SA Model & Angler Catch Rates

ANGLER CATCH RATE

0

0.5

1

1.5

2

2.5

3

1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020

cpueObs. cpue

ABUNDANCE Model, M/R, and snorkel estimates

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025

Vulnerable Population Pop Estimates

Mark/Recapture

Snorkel

ABUNDANCEElectrofishing Catch Rates

ES CPUE fixed sites

0.0

1.0

2.0

3.0

4.0

5.0

6.0

1990

1992

1994

1996

1998

2000

2002

2004

Year

Cat

ch/M

inut

e

Electrofishing (ES) and Angler CPUE Power

• ES CPUE fixed sites only:– Can detect 23% positive and 19% negative linear 

change in CPUE over 5 years.• ES CPUE fixed and random sites:

– Can detect 6 – 10% change in CPUE over 5 years.• Angler CPUE 

– Can detect 10-20% change in CPUE over 5 years, however number of samples is decreasing ($), power may decline slightly.  

Size Structure

• Proportional stock density (PSD)• Growth• Condition

PSD Value

• PSD values within the target range indicate a balanced population. Values less than the target range indicate a population dominated by small fish and values greater than the target range indicate a population comprised mainly of large fish.

Common PSD Targets:

O largemouth bass – 40-70O bluegill – 20-40O yellow perch – 30-50O walleye – 30-60

PSD

SET_YR

20032002

20012000

19991998

19971996

19951994

19931992

1991

95%

 CI P

SD

70

60

50

40

30

20

10

0

3

Growth (18 inches by age III)

• May not be realistic objective at high density.– 16 inches by age III may be attainable at density of 

100,000 fish.• Difficult to measure without marked fish.

– PIT tags may be more useful in future as more tags are implanted.

• Otoliths may be useful for determining ages, methods still being refined and validated

Estimated Growth (Otoliths)

VonB length at age from otoliths 

0

50

100

150

200

250

300

350

400

450

0 1 2 3 4 5 6

Age

mm

0

2

4

6

8

10

12

14

16

18

Inch

es

Growth Comparisons(LF and Carlander)

RBT Growth Lees Ferry and Western Waters (Carlander)

0255176

102127152178203229254279305330356381406432

0 1 2 3 4 5 6

Age

Leng

th (m

m)

0

100

200

300

400

500

600

LF 2004 Western Lakes Western Streams LF Creel length freqs 77-84

Condition Factor

Year

20032002

20012000

19991998

19971996

19951994

19931992

1991

95%

 CI C

ondi

tion 

Fact

or (K

n - W

r)

90

88

86

84

82

80

78

76

74

72

Size Structure Power

• PSD Unknown power

• Growth Low power, high variability

• Condition High power (many lengths and weights)

Natural Recruitment:

• Spawning habitat

• Natural recruitment

• Undetermined metric.  “Available and sufficient”

• ~100 % (no stocking)

Natural Recruitment PARASITES/DISEASE

• External parasites (Learnea)– Cursory evaluation as part of monitoring 

• (no EXTERNAL parasites present)– Detailed Health Assessment Index during mid 90’s 

showed no external parasites, no significant internal concerns other than nematodes; more time and effort to collect data than value added at that time.

• Internal parasites – (nematodes)

• Evaluated as part of diet analysis 

• Whirling Disease– Annual evaluation

Are We Meeting MO 4.1?

B CPUE indices and model seem to accurately reflect abundance.Improvements in sampling design and abundance estimates are ongoing.

~100,000 Age II

>100,000 Age II

Abundance

GradePresentTargetAttribute

4

Are We Meeting MO 4.1?

D Need to establish target and value of attribute.

<10%To Be Determined    

30-60%

PSD

C-/D+ Target may be unrealistic at present density.  Suggest target be evaluated over time.

14 inches by Age III

18 inches by Age III

GROWTH

B0.850.90Condition

GradePresentTargetAttribute

Are We Meeting MO 4.1?

IncompleteThis is not being measured on a regular basis.

Sufficient for natural recruitment

SufficientSpawning habitat

A Monitored annually by AGFD fish health lab.

Free of WDFree of WDWhirling Disease 

A100%100%Natural recruitment

ScorePresentTargetAttribute

Attributes/ Measures

• Abundance (100,000 age II+)• Growth & size structure:

– PSD (not specified – 40-60%)– Length at age (18 “ by age III)– Condition (Wr/ Kn = 0.90)

• Natural recruitment (yes)– Spawning habitat (available)

• Whirling disease (free)

Concerns:• Linkage between fish and foodbase is not being 

investigated.• Recreational use (visitation) is not being evaluated by 

AMP. Should it be reported as part of this effort?• Brown trout seem to be increasing in the LF reach.• Need monitoring program for “other” (non RBT) species 

in the reach, especially with warming water.• Abundance estimates and SA model need to be 

continuously improved.• Mo 4.2 (downstream movement of LF fish) is not being 

addressed ($$$).