Monitoring Humpback Chub in the Little 

Colorado River and Colorado River, Grand 

Canyon

David Van Haverbeke1, Maria Dzul2, Charles B. 

Yackulic2, Kirk Young1, Mike Pillow1, Pilar Wolters1

1 US Fish and Wildlife Service, Arizona Fish and Wildlife Conservation Office, Flagstaff, AZ

2 US Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and 

Research Center, Flagstaff, AZ
Project G: Humpback Chub (HBC) Population Dynamics 

throughout the Colorado River Ecosystem

 Project elements and objectives:

 G.1: HBC population modeling

 G.2 Annual spring/fall HBC abundance estimates in the lower 13.6 km of 

the Little Colorado River (LCR)

 G.3. Juvenile HBC monitoring near the LCR confluence

 G.4 Remote PIT tag array monitoring in the LCR

 G.5. Monitoring HBC aggregation relative abundance and distribution

 G.6. Juvenile Humpback Chub Monitoring - West

 G.7. Chute Falls HBC translocations

 Funding Amount and Source: $989,670, AMP ($945,786 spent)

 Cooperators: USGS, USFWS

 Resource Goals: Humpback Chub, Natural Processes, Other Native Fish
Presentation outline

(Project G)

 LCR aggregation

 Abundances 

 Chute Falls translocations

 Western Grand Canyon

Note: not all abundances are available for 2021

(coming soon!)
Life history of humpback chub in LCR aggregation

Colorado River

Little Colorado 

River

resident
Large subadults

(150-199mm TL)

Low small subadult N in 

the JCM reach 2017-2020

Small subadults

(100-149mm TL)

Some background from 2020...

Very low numbers of age-0 HBC in 

the LCR from 2016-2018

Low large subadult N in 

the JCM reach 2019-2020

(hit the trigger)

Take-home: Lack of age-0 production has 

lagged effects on larger size classes and will 

eventually lead to decline in adults.
Provisional data. Do not cite.

Age-0 abundances in the LCR

Abundance

*

Low age-0 

period

Moderate

age-0

period 2021 

was also 

low!

* Abundance estimate from 2020 is based on expanding from a small proportion of the spatial area (near 

the confluence) and may not be fully representative
Age-0 abundances in the LCR

Abundance

*

2021 

was also 

low!

Provisional data. Do not cite.

* Abundance estimate from 2020 is based on expanding from a small proportion of the spatial area (near 

the confluence) and may not be fully representative
Why low age-0 abundance in the LCR in 2021?

LCR did not flood from April 2020 to July 2021

Figure by Mike Pillow, USFWS

Provisional data. Do not cite.
Why low age-0 abundance in the LCR in 2021?
Lack of winter floods lead to low age-0 recruitment but 

even small floods can produce high numbers of age-0 

HBC

Even small 

winter floods 

can lead to 

high age-0 

production!

Provisional data. Do not cite.
Age-0 abundances in the LCR

Abundance

*

Moderate

age-0

period

Provisional data. Do not cite.

* Abundance estimate from 2020 is based on expanding from a small proportion of the spatial area (near 

the confluence) and may not be fully representative
Annual fall HBC age-0 abundance (blue) and the 

following spring age-1 abundance (red)

Provisional data: do not cite
Annual spring abundances of large sub-adult HBC 

(150-199 mm) in lower 13.6 km of LCR 

No sampling spring 2020

Provisional data. Do not cite.
For age-0 HBC cohorts tagged in fall in LCR, 

what is their fate the following May, July and 

next October?

size location

red <100 LCR

yellow 100-149 LCR

green 150-199 LCR

light blue <100 CR

dark blue 100-149 CR

purple 150-199 CR

black dead dead

Provisional data. Do not cite.
Juvenile abundance in the JCM East (<100mm TL)

Provisional data. Do not cite.
Very high growth for subadults in JCM East during 

summer 2021

Jul-Oct 

2021

Provisional data. Do not cite.
What happened to the large 2019 and 2020 age0 cohorts if they did not show up in the LCR?

 Some outmigration to the CR, but also low survival

 Increases in CR juveniles and subadults are modest 

compared to other big years (e.g., 2011 & 2012) 

 Fast growth of outmigrants from 2019 & 2020 cohorts in 

summer 2021 (warm temps)
Annual spring abundances of adult HBC (≥200 mm) in 

lower 13.6 km of LCR

Provisional data. Do not cite.
Annual fall abundances of adult HBC (≥200 mm) in 

lower 13.6 km of LCR

Provisional data. Do not cite.
Take-home points

LCR & JCM East

 In recent years, low age-0 production

 Especially 2016-2018 & 2021

 2019 & 2020 cohorts 

 Initially high

 Seem to have disappeared from LCR

 Some outmigration, some mortality

 Ensuing declines in adult abundances are likely

 In 2022, we will likely hit the sub-adult trigger in LCR and 

in JCM East
Presentation outline

(Project G)

 LCR aggregation

 Update on abundance 

 Chute Falls translocations

 Western Grand Canyon
Translocations and Chute Falls 

Monitoring
Number of HBC translocated annually (black 

bars) and annual abundances of adult HBC 

above Chute Falls (red and grey bars) 

Provisional data. Do not cite.
Summary: Chute Falls 

Translocations

 To address reaching the “trigger” in the mainstem 

in 2020, we increased the number of HBC 

translocated to above Chute Falls to 535 in 2021. 

 Other options may need to be considered (e.g., 

continue translocating higher #’s above Chute 

Falls, transporting juvenile HBC from western 

Grand Canyon?).
Presentation outline

(Project G)

 LCR aggregation

 Update on abundance 

 Chute Falls translocations

 Western Grand Canyon
Hoop netting sample sites on 2021 agg trip
Annual CPUEs of Humpback Chub and 

Flannelmouth Sucker on aggregation trips 

since 2000 

-2

0

2

4

6

8

10

12

14

16

18

20

22

0

100

200

300

400

500

600

700

800

Mean CPUE (captures/set)

Hoop Nets (n)

Aggregation trip by year

Hoop nets

Humpback Chub

Flannelmouth Sucker

Provisional data. Do not cite.
Annual CPUEs of Humpback Chub above 

Havasu 2010-2021

Provisional data. Do not cite.
Annual CPUEs of Humpback Chub below 

Havasu 2010-2021

Provisional data. Do not cite.
2021 CPUEs of Humpback Chub and Flannelmouth Sucker 

≥200 mm between 30-Mile and Columbine (~276 mile)

Provisional data. Do not cite.
Seining
Humpback Chub catches via seining by river 

mile

Provisional data. Do not cite.
Length frequencies of Humpback Chub 

captured via seining

Provisional data. Do not cite.
Catch comparison: 

Seining vs. Hoop netting

Seining Hoop netting

Bluehead sucker 1 9

Carp 2 10

Fathead Minnow 216 3

Flannelmouth Sucker 1393 8200

Green Sunfish 5 0

Humpback Chub 459 1453

Mosquito Fish 10 0

Plains Killfish 588 43

Rainbow Trout 14 1

Red Shiner 2 0

Speckled Dace 827 616

% nonnatives 23.8% 0.6%

Provisional data. Do not cite.
Summary

 Since ~2017, western Grand Canyon has been 

populated by Humpback Chub representing all size 

classes. 

 We have conducted mark-recapture studies to gain 

capture probability data.

 We have applied capture probability data to catch 

data to estimate abundances and densities of adult 

Humpback Chub.

 We are refining these estimates by accounting for 

habitat variability, effects of turbidity, temp, etc. 
Thank You