Humpback Chub Population Dynamics 

throughout the Colorado River 

Ecosystem

David Van Haverbeke, Maria Dzul, Kirk 

Young, Charles Yackulic, Mike Dodrill, Dennis

Stone, Mike Pillow 

Provisional. Do not cite.
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 chub monitoring - West

 G.7. Chute Falls HBC translocations

 G.9. Backwater seining

 Funding Amount and Source: $1.47 million AMP

 Products: 6 published journal articles, 4 reports, 6 conference

presentations (see AMWG annual report)

Provisional. Do not cite.
G.1-3 HBC population monitoring in and around

the Little Colorado River 

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Provisional. Do not cite.
 Closed models:

 Assumptions: No

immigration/emigration

and Survival is 100%

 Requires short time

between mark and

recapture event

 Open models:

 Allows for survival and

movement

 Need at least 3

capture occasions

 More robust to some

model assumptions

 It is useful to fit both model types to see

whether they agree
Colorado River

Little Colorado 

River

resident

Adult 

abundance in 

LCR 

aggregation
Adult HBC abundance in LCR 

aggregation (open model)

Provisional. Do not cite.
Spring abundances of HBC ≥150 mm and ≥200 

mm in lower 13.6 km of LCR (closed model)

Provisional. Do not cite.
Adult HBC spawning rate

(i.e., movement between CR and LCR)

(open model)

Provisional. Do not cite.
Colorado River

Adult 

abundance in 

Little Colorado 

River

resident

LCR 

aggregation

Provisional. Do not cite.
Colorado River

July age-0 

abundance in 

LCR

Little Colorado 

River

resident

Provisional. Do not cite.
Age 0 HBC abundance in LCR in July

(closed model)

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Fall/spring age0-1 abundance

in LCR

Provisional. Do not cite.
Juvenile HBC abundances 

(closed model)

blue = age-0 fish in fall

red = age-1 fish in spring

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Juvenile 

abundance in 

JCM reach

Provisional. Do not cite.
Fall juvenile HBC abundance in JCM reach

(mostly closed model)

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Juvenile abundance

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Subadult abundance

Provisional. Do not cite.
Spring abundances of HBC (150-199 mm) in lower 

13.56 km of LCR with new 1,250 trigger (closed 

model)

Provisional. Do not cite.
Fall HBC subadult abundance in JCM reach 

(open model)

Provisional. Do not cite.
Colorado River

Little Colorado 

River

resident

Subadult abundance

Provisional. Do not cite.
G.4 Remote PIT tag array monitoring in the LCR:

Multiplexer (MUX)

Provisional. Do not cite.
Comparison of 

spring 2017 data 

show that 

USFWS and LCR 

MUX are 

detecting 

different 

components of 

the HBC 

population.

LCR MUX is 

probably better at 

detecting larger 

fish that might be 

trap shy.

Captured Detected on 

by USFWS LCR MUX

All HBC 2860 2622

HBC with previous 484 1651 capture >199mm TL

Provisional. Do not cite.
Slide Summary 

 Adult abundance is steady (possibly increasing), but

juvenile production has been low for three years.

 Autonomous PIT tag antennas (like the MUX) may

provide valuable detection information about fish that are

hard to sample with hoop nets.

Artwork by Kate Aitchison

Provisional. Do not cite.
G.7 Chute Falls Translocations
Date, numbers, and sizes of HBC collected from the LCR 

for translocations (2003-2018)

Date Chute Falls * Size (mm) SNARRC Shinumo Havasu Size (mm) Total

8/1/03 283 50-100 283

7/30/04 299 50-100 299

7/29/05 567 50-100 567

7/22/08 299 ~80-130 207 <80 506

10/13/08 300 100 <130 400

7/24/09 194 ~80-130 205 83 <80 482

10/10/09 238 <130 238

7/16/10 108 ~80-130 175 <80 283

11/5/10 300 300 <80 600

11/9/11 96 ~80-130 200 300 <80 596

7/12/12 212 ~80-130 202 200 300 <80 914

5/24/13 73 <30 73

7/11/13 99 <80 99

11/7/13 303 ~80-130 11 300 <130 614

5/1/14 660 <30 660

10/31/14 305 65-137 <130 305

5/28/15 315 <30 315

11/1/15 303 61-128 303

10/27/16 137 58-146 137

6/16/17 139 <40

10/26/17 315 66-120 315

10/29/18 49 63-115 49

Totals 3,470 1,082 1,311 2,175 8,038
Above Chute Falls - Number of juvenile HBC translocated 

(black) and adult abundances (red & grey) 

Provisional. Do not cite.
Below Chute Falls (Atomizer reach) - Adult HBC 

abundances (red & grey) 

Provisional. Do not cite.
Chute Falls translocation multistate model

 Multi-state model

 Three different habitats:

 Lower LCR

 Translocated LCR (includes upper Atomizer reach)

 Colorado River 

 Each habitat has different growth/survival

 Fish can move between habitats

Provisional. Do not cite.
Survival is higher for translocated HBC than for 

HBC that remain in lower LCR

Provisional. Do not cite.
Growth (probability of moving to next size class) of 

translocated HBC is similar or faster to that of fish 

in the lower LCR

Provisional. Do not cite.
Number of adults that result from a one-time 

translocation of 300 fish above Chute Falls

Translocate 300 fish in year 0 

(80-150mmTL) Provisional. Do not cite.
Comparison of HBC that have and have not been 

translocated above CF

Purple = translocated above CF

Red = not translocated 

Provisional. Do not cite.
Net benefit of one-time translocation

(difference between two groups in previous slide)

Provisional. Do not cite.
Net benefit of translocating 300 fish every year

amounts to 350 extra adults in LCR aggregation

ranslocate

300 fish 

very year Provisional. Do not cite.

T

e
Summary

 Higher growth rates and increased survival appear to be 

a result of translocating fish to above Chute Falls. 

 Downstream movement may be one factor ultimately 

precluding permanent colonization of HBC above Chute 

Falls.

 Translocations are relatively easy and inexpensive 

beneficial conservation action.

Provisional. Do not cite.
G.5 Monitoring Colorado River aggregations 

of Humpback Chub


Species catch by aggregation trip (2010-

2018) 
Species catch (nonnatives only) by 

aggregation trip (2010-2018) 
HBC CPUEs at 

aggregation and

non-aggregation

sites 

2018
HBC CPUEs at 

aggregation and 

non-aggregation 

sites 

Periods
CPUEs of adult HBC by year in 

western Grand Canyon
Length frequencies of HBC during agg 2010-2013 

trips vs 2014-2018 (western Grand Canyon)

 Reach 1 (Havasu-Lava) Reach 2 (Lava-Diamond) Reach 3 (below Diamond)
Seining CPUEs of HBC in western Grand 

Canyon
Closed population estimates of HBC and 

Flannelmouth Sucker (FMS) in the mainstem

 In 2017 we estimated closed abundances of 

HBC and FMS by size categories in the JCM 

East and JCM West reaches.

 Our strategy was to use the aggregation trip as a 

marking event, followed by the JCM monitoring 

as a recapture trip. 

 This was repeated in 2018, but at one additional 

site below Diamond Creek near Bridge City.
Closed population estimates and densities 

(fish/mile) of HBC by size class near Bridge City 

in fall 2018 (RM 236.7-238.7; 2 miles of river)

Length (mm) Marked Captured Recaptured N Lower Upper CV p1 p2 Adj. Density

100-149 10 67 3 140 94 186 0.17 0.04 0.30 63

150-199 81 149 27 385 280 490 0.14 0.18 0.33 174

200-249 28 95 18 199 139 260 0.15 0.19 0.64 90

250-299 41 143 13 324 234 415 0.14 0.09 0.32 147

>=300 20 100 7 214 150 279 0.15 0.07 0.35 97

1,263 571

95% CI
HBC and FMS density (fish/mile) in 

Bridge City reach fall 2018
Adult HBC densities (fish/mile) by size 

category in the mainstem at 3 select locations
Summary

 Native fish comprised 99.8% of hoop net catches in the 

mainstem aggregation trip in 2018.

 HBC and FMS hoop net CPUEs continue to be high in 

western Grand Canyon (although somewhat lower than 

2017).

 Since 2014, western Grand Canyon has been populated 

by HBC representing all size classes. 

 Thus far, successful closed mark-recapture efforts for 

HBC have occurred at JCM East (2017, 2018) and JCM 

West (2017), and at Bridge City (2018), with the most 

successful (sufficient recaptures within 50 mm size 

classes) being at Bridge City (2018). 
Thank you