Update: Non-native Fish 

in the Glen Canyon 

Reach Below Glen 

Canyon Dam

Glen Canyon National Recreation Area,

National Park Service

Bud Fazio – Manager, Science and Resources

Jeff Arnold – Fisheries Biologist
Upper Slough, Lower Slough and Lee’s Ferry
Year

1980 1985 1990 1995 2000 2005 2

Number of Green Sunfish

0

10

20

30

40

River Mile

0 50 100 150 200

Frequency

0

5

10

15

20

25

30

Kanab Creek

250 300

010 2015

550F

730F
2022 Water Temperatures At Lower End of Slough (-12 mile) – Colorado River

15

17

19

21

23

25

27

29

31

33

35

Water Temperature (oC)

Date

Temp 1 Meter From Bottom Temp 0.10 Meter From Bottom

July 30-31 Aug 6-7 Aug 13-14 Aug 20-21 Aug 27-28

Weekends Values
Water Temperatures (oC) at Lower End of Slough (-12 mile) – Colorado River

Discharge (cfs) at Lees Ferry (0.0 mile) 2022

6000

8000

10000

12000

14000

16000

18000

15

17

19

21

23

25

27

29

31

33

35

Discharge (cfs)

Water Temperature (oC)

Date

Temp 1 Meter from Bottom Temp 0.10 Meter from Bottom Discharge Weekend Values

July 30-31 Aug 6-7 Aug 13-14 Aug 20-21 Aug 27-28
2022 Water Temperatures in Upper Slough (-12 mile) – Colorado River

15

17

19

21

23

25

27

29

31

33

35

Water Temperature (oC)

Date

Temperature 0.10 M from bottom

July 30-31 Aug 6-7 Aug 13-14 Aug 20-21 Aug 27-28
Timeline for Non-Native Fish Management

Upper and Lower SLOUGH (-12 Mile) in 2022

April 27

Slough Pump-out

April May July Aug June Sep Oct 

May 10

155 GSF Translocated to 

Lake Powell

May 31

Large Num. YOY Carp 

Discovered in Lower 

Slough

June 1 – NPS Implements a 

Netting Program – (Minifykes {3}) 

June 30 - SMB YOY 

Discovered in Lower 

Slough 

Aug 10 – Attempted to Install 

Turbidity to Prevent Fish

Movement

Sep 17 – Chemical Treatment

of Upper and Lower Slough

Sep 14 – Second Slough Pumpout

Oct 3

159 GSF Translocated to 

Lake Powell

Aug 17 – Block Net 

Installed at Mouth of 

Slough
YOY Small 

Mouth Bass 

confirmed in 

Lower Slough 

on June 30, 

2022
Slough YOY SMB 

available for otolith 

or genetic analysis

Lower Slough showing location of minifyke nets (red), large fyke nets (blue), and temperature loggers (yellow).
Changes in Carp and Green Sunfish Densities (Minifyke Nets)

June 1 – September 2, 2022

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1-Jun 8-Jun 15-

Jun

22-

Jun

29-

Jun

6-Jul 13-Jul 20-Jul 27-Jul 3-Aug 10-

Aug

17-

Aug

24-

Aug

31-

Aug

Number of Fish

Date

Carp

0

50

100

150

200

250

300

350

Numbers of Fish

Date

Green Sunfish
CHEMICAL TREATMENT
Summary of Fish Caught/Removed in Lower Slough in 2022

Before Treatment (Jun 1 – Sep 2)

• Common Carp – 84,045

• Green Sunfish – 1,397

• Bluegill – 57

• Black Crappie – 7

• Smallmouth Bass – 20

• Rainbow Trout – 5 (Released)

• Flannelmouth Sucker – 530 (Released)

After Treatment (Sep 18)

• Common Carp – 3,331

• Green Sunfish – 810

• Bluegill - 4

• Rainbow Trout - 4
Flow Through - Long Term Solution? 

Brown Trout - Incentivized Harvest Program

Lees Ferry vicinity

Glen Canyon National Recreation Area

Jeff Arnold – Fisheries Biologist, NPS
Brown Trout Incentivized Harvest Program Nov 2020 – August 2022 

Current Rewards

• $33/fish

• $50 every 3 fish

• $300 Every PIT Tag

Summary

• 1408 BNT Harvested

• 153 PIT Returned

• $109,443 Rewards Paid 

Future (2022-2023)

• Youth Tribal Involvement

• Increased Rewards (Bonanza) During Spawning Season (Dec 22 – Feb 23 ?)

Month Year

Monthly 

Payout

Top Angler 

Payout/Mont

h No. Anglers

Unknown 

Length

Fish Harvested 

6-12 inches

Fish Harvest 

12-18 inches

Fish Harvest 

18-24 inches

Fish Harvested 

> 24 inches

Total Number of Brown 

Trout Harvested

Total Number 

of PIT tags 

returned

November 2020 $1,025 $150 21 0 11 22 8 0 41 2

December 2020 $775 $275 19 0 12 16 3 0 31 0

January 2021 $1,150 $125 19 4 5 23 14 0 46 2

February 2021 $900 $175 15 0 6 25 5 0 36 0

March 2021 $1,452 $429 17 1 12 24 17 1 55 1

April 2021 $6,149 $1,163 37 1 24 66 12 0 103 10

May 2021 $1,650 $231 24 0 17 24 9 0 50 2

June 2021 $990 $396 12 0 1 13 15 1 30 3

July 2021 $1,254 $231 18 2 13 19 4 0 38 2

August 2021 $2,168 $960 9 0 6 32 8 0 46 2

September 2021 $4,200 $1,978 18 0 14 29 7 0 50 7

October 2021 $3,996 $449 35 1 21 31 8 1 62 4

November 2021 $793 $183 12 0 2 14 5 0 21 0

December 2021 $3,123 $864 12 0 3 20 7 1 31 1

January 2022 $7,504 $3,186 19 0 8 57 23 0 88 8

February 2022 $8,250 $2,543 22 0 20 63 17 0 100 12

March 2022 $6,510 $1,939 24 12 5 70 32 1 120 3

April 2022 $17,421 $7,182 38 2 22 114 47 2 187 29

May 2022 $16,529 $9,876 34 9 31 105 16 2 163 30

June 2022 $10,080 $4,792 28 1 28 57 22 2 110 17

July 2022 $8,408 $2,239 28 5 22

August 2022 $5,116 $2,994 12 0 13

TOTAL $109,443 $42,360 473 38 296

68 31 1 127 9

25 12 2 52 9

917 322 14 1408 153