Factors Affecting Humpb

Chub Population DynamGrand Canyon

Lew

Coggins

Grand Canyon Monitoring and ResCenter
X

X

X

XX

Review of HBC Distrib
Humpback Chub Distribution in G

X

X

XX

X

X

X
Tag-Recapture Matrix (Pit Data 989-2000)

Aggregations other than the LCR likely supported by LCR population emigrants (strongly suspected)

Little Movement Among Agg

30

MI 

LC

R 

LC

RIN 

U

G

G 

B

A

C 

S

H

M 

S

H

MIN

S

T

E

P

H-C

M

G

G

K

A

N 

K

A

NIN

H

A

V 

H

A

VIN

BLO

HAV 

Tag Location Total Tagged 30

MI LC

R LC

RIN

U

G

G

B

A

C

S

H

M

S

H

MIN

S

T

E

P

H-C

O

N

Q

M

G

G

K

A

N

K

30

MI 3

4 16 1 0

0

0

0

0

0

0

0

LC

R 11779 1 1203

2

7

6

6

3

0

0

0

0

0 0 

LC

RIN 115

8

0 88

3

2

5

7

0

0

0

0 1 1 0 

U

G

G

4

3

0

2

0

2

0

0

0

0 1 0 

B

A

C

2

0

0 0 0

0

0

0

0 0 0 

S

H

M 18

0

0

0

0

0

2 1 0

0 0 

S

H

MIN

4

7

0

0

0

0

0

0 15

0 0 0 

S

T

E

P

H-C

O

N

Q

3

2

0

0 0 0

0

0

0

3 1 0 

M

G

G 181

0

0

0

0

0

0 1 1 75

0

K

A

N 1 0

0 0 0

0

0

0

0 0 0 

K

A

NIN

5

0

0 0 0

0

0

0

0 0 0 

HA

V

4

2

0 1 0

0

0

0

0

0 1 0

H

A

VIN

4

0

0 0 0

0

0

0

0 0 0 

BLO

H

A

V

8

0

0

0

0

0

0

0

0

0 0 

Total 13354 17 1291

9 102

3

5

0

2 17

5

7

9

0 

RE

D i

s Do

w

n

stre

a

m M

o

v

e

m

e

nt

Y

ELLO

W i

s U

p

stre

a

m M

o

v

e

m

ent

Gre

y i

s "no m

o

v

e

m

ent"

R

ecapture L

ocation
• Little Colorado River

– Perennial spring fed river throughout 

lower ~21km

– Baseflow ~250 cfs, 21° C at blue 

spring, high salinity

– Occasional intense flooding 

associated with runoff and monsoons 

– Few cold water non-natives.– Warm water non-natives.– Asian Tapeworm

• Colorado River

– Cold, hypolimnial releases from Glen 

Canyon Dam

– Water temperature too cold for 

successful reproduction of humpback chub.

– Few warm water non-natives– Cold water non-natives

Why are there still HBC in the 
Distribution and Life History Attribu

LCR HBC Population

 Distribution

 Lower 14.9 km in LCR RM 56 – 65.5 in Mainstem (8 km 

upstream and 11 km downstream from confluence).

 All life stages found in LCR. Predominantly HBC >200 mm 

found in mainstem.

 YOY and Juveniles found in 

mainstem following LCRfreshets (Spring & late Summer).
Distribution and Life History Attribu

LCR HBC Population

 Spawning Migration

 Adults stage near 

confluence FebruaryMarch

 Enter LCR March –

April

 Return to M

ainstem April –

July

 Unknown migration cues

 YOY initially captured in 

LCR

 May -

July
Stock Assessment Re

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 
Decline in adult HBC seems to be a result of 

 Assessment Uncertainty

 Recruitment estimates 

before 1989 based on observed size (age) structure observed in the late 1980s.

 Error in age assignment 

results in a “smeared” or running average characterization of recruitment strength, particularly prior to 1989.

 Patterns observed in 

recruitment time series subject of much speculation. Decline of 1992 year class temporally correlated with lots of changes. Bottom line... correlations and speculations not grounded in good science.

0

5,00

0

10,00015,00020,000

1975

1977

1979

1981

1983

Number of Recruits
What do we know or suspec

recruitment dynamics of this po

 Successful spawning occurs in the 

Colorado River (known)

 Most successful rearing occurs in 

Colorado River (suspect-known)

 Juvenile fish migrate to the mainst

associated with freshet events in t(known)

 Juvenile fish under some size (sus

100mm -200mm) have very poor sumainstem Colorado. Therefore, marecruitment is from fish that remaiuntil reaching some critical size
What do we know or suspec

recruitment dynamics of this po

 Factors inhibiting 

successful recruitment in the LCR include:

 Low productivity (known) Asian Tapeworm (known) 

Paper available: Cole et al 2004

 Competition/predation with 

native and non-native fish (Suspect)

 Flooding and displacement 

out of the LCR (known)

 Water Quality?

 Not monitored (unknown)

0

5,00

0

10,00015,00020,000

1975

1977

1979

1981

1983

Number of Recruits
What do we know or suspec

recruitment dynamics of this po

 Recruitment levels 

evident in the mid to late 1990’s may represent rearing capacity of the LCR (SUSPECTED)

 With no additional 

suitable rearing area (e.g. mainstemColorado), recruitment level may persist at or below late 1990’s average (SUSPECTED)

0

5,00

0

10,00015,00020,000

1975

1977

1979

1981

1983

Number of Recruits
Why do juvenile fish find the m

Colorado poor rearing hab

 Temperature

 Poor growth (known) Cold shock (suspectedknown)

 Food

 Likely better resources in 

the mainstem than in the LCR, adults seem to gain condition better in the mainstem. (unknown)

 Dam Operations

 (e.g. fluctuating flows) 

destabilizing near-shore habitat? No adequate test yet performed (unknown to suspected).

0

5,00

0

10,00015,00020,000

1975

1977

1979

1981

1983

Number of Recruits
Why do juvenile fish find the m

Colorado poor rearing hab

 Non-native fish 

 predation/competition 

(suspected)

 Lack of turbidity

 Increase in autotrophic 

production (known)

 Increase in efficiency of 

sight predators (known)

 Lack of quality nearshore

rearing habitat

 Do backwater habitats 

support a large fra

ction of 

successful mainstemrearing (unknown)

 Complex interactions 

among above factors

 E.g., cold temperature and 

slow growth, increased predation

0

5,00

0

10,00015,00020,000

1975

1977

1979

1981

1983

Number of Recruits
What other factors potentially a

population dynamics

 Capture and handling of fish for monitor

 Capture, handling, tagging of fish has been s

individual fitness in a variety of ways (growthKNOWN). 

 Investigation of these factors will do little to u

handling affects vital population rates (morta

 KEY QUESTION: How do current or proposed 

programs affect population vital rates? (UNK

 This is an extremely difficult research question Past research in this area usually utilizes capti

useful in providing insight into changes in fish handling, not vital rates. 

 Mortality is essentially impossible to fully add

it is certainly underestimated. 

 Recruitment is inferred through changes in fec Simple assessments of condition factor will on

we already know.
What other factors potentially a

population dynamics

 Capture and handling of fish for mo

research

 Ultimately, managers must grapple wi

unavoidable facts relative to estimatinabundance with mark-recapture studie

 Handling causes fish stress and can ultim

diminished health and death.

 High precision and low bias in mark-recap

abundance is directly related to proportion handled.

 Bottom line 1... Increases in accuracy and 

recapture based stock assessment prograwith an increased risk of depressing vital 

 Bottom line 2... Monitoring and research s

least invasive technologies available. E.gtrammel nets as possible, remote pit tag acamera
What other factors potentially a

population dynamics

 Recreation in the Lower Little Colo

 Difficult to believe that recreation acti

humpback chub population dynamics 

 However, no evidence to suggest that 

activities affect humpback chub popunegatively

 Limiting humpback chub emigratio

 Ponding

Hypothesis (untested and un

 Potentially beneficial if rearing capaci

 BHBF

 Evidence from 2004 suggests that BHBF 

caveats described in the March AMWG Madversely affect juvenile humpback chub Colorado at the time of the BHBF.
Where do we go 

here?
Nulls: Range, Population Dynamics, Healt

Recreation

Impacts

(LCR mouth)

Scientific Handling

Biotic 

Interactions

Flow and Geom

Water Temperature

Geochemi

Foodbase

Diseases /

parasites

Predation

Competition

Mainstream CR (Dam FX)

Lower Paria R.Other Tributaries

Other CR Instream Sites

Habitat Template: Existing and Potential Distribution

Restricted

Gene Flow

Fig. 3: Logical tree of hypothetical interactions that account for humpbac

status. Each box should be considered in relation to the various lif
Which factors can we test 

experimentation?

 LCR

 Low productivity (known)

 Likely not possible to manipulate

 Asian Tapeworm (known)

 Likely not possible to manipulate Advice from parasitologist suggests that a

captured fish will be ineffective given high subsequent infection. However, need to hAGFD research.

 Competition/predation with native and 

(Suspect)

 Attempts thus far suggest large scale mec

the LCR will be problematic (bycatch of HBeffective gear). However, further consider
Which factors can we test 

experimentation?

 LCR

 Displacement out of the LCR (known)

 Experimentation with various methods to keep 

LCR is reasonable to consider.

 Potential Problems:

 Inadvertently exceeding rearing capacity and ca

increases in mortality (more is not always b

ette

 Pos

sibly restricting migration opportunities for 

 Mainstem Colorado River

 Temperature

 Implementation of a TCD would allow experime Potential Problems:

 Irreversible changes in fish communi

t

y structur

 Establishment of new parasites or diseases Others that you have already heard about

 Recent bioenergetics modeling by Petersen an

suggests desirable changes in interactions betassuming adequate food resources 
Which factors can we test 

experimentation?

 Mainstem Colorado River

 Dam Operations

 Given the focus of this program on the op

makes sense to experiment with operation

 We should learn from the uncertainty we a

experiencing and plan experiments with oadequate duration and contrast to facilitat

 Non-native fish 

 Mechanical removal treatments should be 

context of well designed experiments

 Lack of turbidity

 Turbidity augmentation experiments shou

considered given the possibility to adverstrophic level productivity. A better undersproductivity is required through improved and monitoring.
Which factors can we test 

experimentation?

 Mainstem Colorado River

 Lack of quality nearshore

rearing hab

 Understanding the contribution of backwa

overall mainstem rearing and recruitment uncertainty in this program.

 It is not clear that we can affect the abund

distribution of backwaters through manag

 Complex interactions among above fa

 Only through well designed experiments c

account for interactions and environmentaresponse variables (e.g., HBC recruitment