Predation Risks Posed by Introduced 

Warm-water Predators

Annual Reporting Meeting, Jan 2023

David Ward, Eric Frye, Laura Tennant, Clay Nelson

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

This information is preliminary and is subject to revision. It is being provided to meet the need for timely best science. The

information is provided on the condition that neither the U.S. Geological Survey nor the U.S. Government shall be held liable for 

any damages resulting from the authorized or unauthorized use of the information.
Requested Elements

1. Project Title:

Warm Water native and non-native fish research and monitoring

2. Project Elements

Project I.3 FY 21-23 workplan 

3. Project Objectives

Quantify the potential impacts of channel catfish and other non-native 

predatory fishes on native fish in the Little Colorado River

4. Funding amount and Source

FY 23 - $101,277 – GCDAMP

5. Cooperators

AZ Game and Fish, U.S. Fish and Wildlife Service, Navajo Nation

6. LTEMP Resource Goals addressed

Conserve and protect native fishes
It’s a Fish eat Fish World

What is eating what?

And how much?

At what life stage?

Common Carp Predation on Humpback Chub eggs

9 Replicates

Spring

2020

• 1 mL of

Fertilized

Eggs/tank

• Control =

No Carp

• Variable =

2 Carp for 

24 hours

• Compare 

Hatch in 

10 days
96 % average decrease in egg and larval survival

Common Carp predation on HBC eggs

Treatment

Carp No Carp

Number of surviving HBC larvae

0

100

200

300

400

Mean = 309

Range 152 - 452

Mean = 9.5

Range 0 - 24

*Provisional Data – do not cite
2021-2022 Scale up X 10

X 2

12 Replicates
Common Carp predation on HBC eggs

Treatment

Carp No Carp

Number of surviving HBC larvae

0

200

400

600

800

1000

Mean = 43

Mean = 751

94 % average decrease in egg and larval survival

Did I do 

That?

*Provisional Data – do not cite


Carp x 4 x 12 24 H

or
Juvenile Native Fish total length (mm)

20 30 40 50 60 70

Probability of Survival (%)

0

20

40

60

80

100

Chub

Razorback sucker

Predation on chub and suckers in clear water

*Provisional Data – do not cite
Juvenile Native Fish total length (mm)

40 60 80 100 120

Probability of Survival (%)

0

20

40

60

80

100

Razorback sucker

Humpback chub

Predation on chub and suckers in turbid water

*Provisional Data – do not cite

Small-bodied predators

Predator Total Length (mm)

30 40 50 60 70 80 90 100

Probability of Survival (%)

0

20

40

60

80

100

Plains Killifish

Red Shiner

Fathead Minnow

Green Sunfish

Survival of larval humpback chub (12 mm TL) as predator size increases for four species of small-bodied predatory fish commonly found in the Little 

Colorado River. Probability of survival calculated using JMP Prediction Profiler, based on 10 replicated 24-hr laboratory trials for each predator species 

(4 predators and 12 prey in each trial).

*Provisional Data – do not cite
Juvenile humpback chub total length (mm)

10 20 30 40 50 60

Percent survival of humpback chub in the presence 

of 80 mm Green Sunfish

0

20

40

60

80

100

Green Sunfish

*Provisional Data – do not cite

LCR Channel 

Catfish
2019

100 200 300

Frequency

0

2

4

6

8

10

Average Size 408 mm

N = 82

2021 Total 

Total Length (mm)

100 200 300 400 500 600 700

Frequency

0

2

4

6

8

10

Average Size 450 mm

N = 83

Length (mm) 2022

400 500 600 700

Total Length (mm)

100 200 300 400 500 600 700

0

2

4

6

8

10

Average Size 515 mm

N = 22

4X decrease

*Provisional Data – do not cite

Frequency
Channel Catfish in LCR 

14.5 % - 27.3 % of fish caught across years had fish 

remains in stomach (from gastric lavage)

600 Channel Catfish (very conservative, low estimate)

10% eat a native fish every 24 hours

60 fish eaten/day X

100 days of warm water (above 20 C) = 6,000 fish eaten/year 
Sucker vs chub survival with Channel Catfish

Total Length (TL)

60 80 100 120 140 160

Survival (%)

0

20

40

60

80

100

Sucker survival

Chub survival

Photo by Jan Boyer 

AZGFD

*Provisional Data – do not cite

Chub Total Length (mm)

45 50 55 60 65 70 75 80 85

Probability of Survival (%)

0

20

40

60

80

100

10 °C

15 °C

20 °C

Rainbow Trout

*Provisional Data – do not cite

Percent (%) probability that a juvenile chub will survive predation by a 285 mm rainbow trout as 

chub size increases from 45-85 mm TL at 10, 15 and 20 °C, with trout size held constant at 285 

mm TL. 

 

 

Chub Total Length (mm)

45 50 55 60 65 70 75 80 85

Probability of Survival (%)

0

10

20

30

40

50

10 °C

15 °C

20 °C

Brown Trout

9 X more piscivourous than a rainbow trout

*Provisional Data – do not cite

 

 

Percent (%) probability that a juvenile chub will survive predation by a 285 mm brown trout as 

chub size increases from 45-85 mm TL at 10, 15 and 20 °C, with trout size held constant at 285 

mm TL. Note that the y-axis on the brown trout is reduced by half.

Chub in Clear Water With Smallmouth Bass

30 % survival

70 mm chub = 10 mm body depth

140 mm Bass = 20 mm Max gape

*Provisional Data – do not cite
Chub in Turbid Water (300 – 500 NTU)

50 % survival

*Provisional Data – do not cite
We need a way to prioritize risk 

among these species
Comparison of Predators

Juvenile chub total length (mm)

45 50 55 60 65 70 75 80 85

Probability of Survival (%)

0

20

40

60

80

100

Rainbow Trout

Brown Trout

Smallmouth Bass

Humpback chub

Channel catfish

Common Carp

Comparison of Predators in clear water (285 mm TL)

*Provisional Data – do not cite
Predation vulnerability of HBC at 30% of predator size

Predator Species

Rainbow trout Brown trout Smallmouth bass Green sunfish Channel catfish Plains killifish Red shiner Fathead minnow

% Surivival

0

20

40

60

80

100

*Provisional Data – do not cite
Is the Sky Falling --- Yes!
Incompatibility of native and nonnative fishes

Marsh and Pacey 2005

Clarkson et al. 2005

Mueller 2005
Solutions

- Need to be community based

- Create/maintain areas or 

environments where some life 

stages are protected
Barriers to upstream fish movement in the Little Colorado River already exist

Maybe we just need to work with what is already there