AMWG Desired Future Condition

A high quality,self-sustaining, trout fishery in GCNRA, as further described in 

the Recreation DFC that does not adversely affect the native aquatic community 

in GCNP
Shared Fishery Goals for the lower 

Colorado River – NPS/AGFD

1. Maintaining a quality recreational Rainbow Trout fishery in Lees Ferry

2. Maintaining healthy populations of all native fish (including Humpback 

Chub and Razorback Sucker) populations in the lower Colorado River
History of Trout in Lees Ferry

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

AZGFD TROUT STOCKING

Rainbow Trout Stocking Cutthroat Trout Brook Trout Coho Salmon

Rainbow Trout = 2,122,442

Cutthroat Trout = 60,857

Brook Trout = 391,562

Coho Salmon = 20,000
History of Trout in Grand Canyon

0

50000

100000

150000

200000

250000

NPS/USFWS TROUT STOCKING

Rainbow Trout Brown Trout Brook Trout

Rainbow Trout = 427,007

Brown Trout = 249,000

Brook Trout = 108,000
Rainbow Trout Population 

Trends in Lees Ferry

Year

1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017

Rainbow trout CPUE (fish/min)

0

2

4

6

8

10

4 fold decline in CPUE 

from 2012 - 2016
Catch rates < 1 fish per hour – 2014 -

2017

Year

1975 1980 1985 1990 1995 2000 2005 2010 2015

Angler CPUE (fish/hour)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

Boat angler CPUE 

Walk-in angler CPUE 
Angler catch rates mirror 

electrofishing trends

Year

1992 1995 1998 2001 2004 2007 2010 2013 2016

Rainbow trout CPUE (fish/minute)

 standard electrofishing

0

2

4

6

8

10

Rainbow trout CPUE (fish/hour) for boat anglers

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Electrofishing 

Boat anglers 

Walk-in anglers 
11.2 

11.0 

~ 

c 0.8 

:2 

·:E 

:!= 

:~ 0.6 •C 

QI 

"Cl 

•C 

::::, 

~ OA 

0.2 

0.0 

2012 

High reuuitment in 2011 due 

to higll & steady flows over 

spri ng-sum mer 

Limited recru itment 

Higher mortality for larger s1 ze 

classes (die-off) 

I I 

2013 2014 2015 2016 

S ize Cllass (rnm} 

• ::,,: 275 

• 225-274 

D H5-224 

D 125-174 

• 75-1124 

Recru itme 11t 

increases 

2017 
<152 mm TL

1990 1995 2000 2005 2010 2015

CPUE (fish/min)

0

3

6

152-305 mm TL

1990 1995 2000 2005 2010 2015

0

3

6

306-405 mm TL

Year

1990 1995 2000 2005 2010 2015

CPUE (fish/min)

0

1

2

>405 mm TL

Year

1990 1995 2000 2005 2010 2015

0

1

A

C D

B

“Catchable” population of Rainbow Trout is 

still depressed
Poor catch rates = less angler use (>35% 

decline)

Year

1980 1984 1988 1992 1996 2000 2004 2008 2012 2016 2020

Yearly relative angler use

0

2500

5000

7500

10000

12500

15000

17500

20000

boat anglers 

walk-in anglers
2015 Lees Ferry Management Plan

OBJECTIVE – Provide a quality trout fishing experience with catch

frequency commensurate with the Blue Ribbon status of the fishery.

Angler Catch

Rate

Angler catch rate ≥ 1 Rainbow

Trout per hour

• Stocking

• HFEs

• Change in regulations
AGFD plans to stock 16,000 triploid Rainbow 

Trout with focus timeframe between April 

1st and October 15th 
AZGFD/USFWS Approach

2018/2019 – Two year 

research project to evaluate 

project

2019 – 2038 – Nonnative 

stocking procedures manual, 

consistent with Upper Basin 

Program
4 Lenses to evaluate “Take” using Grand 

Canyon and Western U.S. big river 

Published Literature 

1. What is the estimated survival rate of triploid Rainbow 

Trout stocked into Lees Ferry? 

2. How many stocked triploid Rainbow Trout are expected 

to out-migrate downstream to habitats occupied by 

Humpback Chub? 

3. How many Humpback Chub would be ingested by the 

out-migrating stocked triploid Rainbow Trout? 

4. What will be the effect of this stocking on the Humpback 

Chub population?
1) What is the estimated survival rate of 

triploid Rainbow Trout stocked into Lees 

Ferry? 

• Studies have shown stocked 

catchable trout in rivers and 

streams experience greater 

than 95% mortality rate, 

and persist less than three 

months post-stocking (Miller 

1952, Walters et al. 1997; 

Bettinger and Bettoli 2002, 

High and Meyer 2009, 

Quinn and Kwak 2011). 

Assumption made: 

95% mortality over 

90 days
2) How many stocked triploid Rainbow 

Trout are expected to out-migrate 

downstream to habitats occupied by 

Humpback Chub? 

Assumption made: 0.11% out-migration to reaches II-III and 

0.02% out-migration to reaches IVa and IVb over a 90 day period

Korman et. al. 2016
3) How many Humpback Chub would be 

ingested by the out-migrating stocked 

triploid Rainbow Trout? 

Yard et al. 2011, estimated a 

piscivory rate for Rainbow Trout 

upstream and downstream of the 

LCR of 4 fish and 10 fish ingested 

per year respectively. Of those fish, 

27.3% were documented to be 

Humpback Chub.

David Ward, USGS study results 

indicate between a 47% and 22% 

reduction in predation by hatchery 

raised triploid Rainbow Trout 

versus wild diploid Rainbow Trout.

Assumption Made: A 

correction factor of 22% was 

used resulting in an annual 

estimated annual piscivory of 

3.12 and 7.8 fish ingested per 

Rainbow Trout upstream and 

downstream of the LCR 

respectively. Of those fish, 

27.3% are assumed to be 

Humpback Chub.
4) What will be the effect of this stocking 

on the Humpback Chub population?
Humpback Chub abundance exceeds 

10,000 adults!
Requisite Level of Impact

District Court (E.D. Cal, 

2010) says that 9th Circuit 

cases say that harm by 

habitat modification requires 

proof of a population-level 

impact to listed species
Over 1 million diploid Rainbow Trout 

Korman et. al. 2016
Adding 16,000 triploid Rainbow Trout to the 

existing diploid Rainbow Trout population 

does not constitute a habitat modification to 

the environmental baseline or population 

level effect 
Conservation Measures

1. AGFD will host annual reporting meeting

2. AGFD will not stock more than 5,000 Rainbow Trout per month

3. All stocked trout will be left pelvic fin clipped

 If funding and compliance is available PIT tags will be used and a PIT tag array will 

be placed in the Grand Canyon

4. The Department will assist the Service in monitoring 30 mile spring for 

Humpback Chub

5. Off ramp stockings at between 8000-9500 individuals (rates still TBD)

6. Monitor Lees Ferry Rainbow Trout Objectives via creel and electrofishing 

trend survey

7. Monitor downstream under existing planned surveys – any suspected 

stocked trout will be evaluated for triploidy or PIT tags
Implementation Approach

1. Finalize Biological Opinion with USFWS for 2018

2. Section 106 if federal funding used

3. Public Meeting March 5th in Marble Canyon

4. Stocking for 2018 to begin Spring

5. Begin nonnative stocking procedures manual for the State of Arizona

6. Initiate EA and Section 7 on Arizona specific nonnative stocking 

procedures manual
It’s all about 

balance!

Questions?