Lee’s Ferry, Long-term Rainbow Trout Monitoring 

2006 Trip Report 

(Trip LF20060404) 

David Ward, and Scott Rogers 

Research Branch 

Arizona Game and Fish Department 

506 N. Grant Street, Suite L 

Flagstaff, AZ 86004 

Submitted to: 

Grand Canyon Monitoring and Research Center 

Flagstaff, AZ 86001 

Cooperative Agreement # 01WRAG0045 – Mod 5 

May 2006 
The Lee’s Ferry tailwater was sampled on April 4 – 6, 2006 as part of the 

cooperative agreement for Lee’s Ferry long-term monitoring between the Arizona Game 

and Fish Department (AGFD) and the Grand Canyon Monitoring and Research Center 

(GCMRC). We sampled 27 stratified random and 9 fixed electrofishing (EF) transects in 

an augmented, serially alternating sampling design (Urquhart et al. 1998). Sampling of 

stratified random sites gives more accurate estimates of fishery status, whereas sampling 

fixed sites provides continuity to existing trend data. New sites were randomly selected 

without replacement from all available habitat types and stratified by river mile into 

upper, middle, and lower reaches. Each site was sampled by single pass electrofishing 

with an Achilles inflatable raft equipped with Coffelt CPS output regulators. We applied 

approximately 300-400 volts and 13-17 amps to a 35 cm stainless steel anode, while 2 

crewmembers (per boat) netted stunned fish from the bow of each boat. The sampling 

crew consisted of Scott Rogers, Brian Clark, Clay Nelson, Teresa Hunt, and David ward 

from the Arizona Game and Fish Research Branch. Stewart Reeder and Peter Weiss, 

contractors from Humphrey Summit, Inc., operated the two EF boats. 

Water releases from Glen Canyon Dam ranged from about 7,000 cfs during the 

day and increased to about 12,000 cfs in the late evening. The average water temperature 

ranged between 8.1 oC and 9.1 oC. We measured captured fish to the nearest millimeter 

total length,(TL) and weighed them to the nearest gram (fish <100 mm were not 

weighed). We examined all rainbow trout for the absence of left pelvic fins (LP2, 

GCMRC Floy tags and adipose fins (ADP, AGFD trout monitoring). Trout missing an 

adipose fin were scanned for the presence of a PIT tag and released. At fixed sites, we 

implanted PIT tags into trout over 150 mm total length (TL) and clipped their adipose 
fins for future assessment of PIT tag loss. All previously unmarked native fishes 

received 134.2 kHz PIT tags. A total of 48 RBT were sacrificed at fixed sites for AGFD 

diet and age analysis. 

We caught a total of 293 RBT, 2 brown trout (Salmo trutta; BNT), and 2 

flannelmouth sucker (Catostomus latipinnis: FMS) (Table 1). Preliminary data indicate 

mean catch-per-effort (CPE; fish/min EF) of all RBT was 0.99 fish/min (Standard error = 

0.29) at fixed sites and 1.09 fish/min (Standard error = 0.30) at random sites. Relative 

condition (kn) for fixed sites was 84.76 for fixed sites (Standard error = 2.26), and 84.5 

for random sites (Standard Error = 1.3). We implanted 22 RBT with 400 KHz PIT tags. 

Rate of recapture for wild-spawned (PIT carrying) RBT was 2.73 % (N=8 recaps). 

Rainbow trout catch per unit effort (CPUE) in the Lee’s Ferry tailwater continues 

to decline. Historically the April Lee’s Ferry monitoring trip has the highest catch rates 

of the year; however, this year catch rate continues to be very low. Overall CPUE from 

April 2006 sampling is lower than has been reported since monitoring began in the early 

1990’s (Figure 1). The combination of warmer mainstem water temperatures, low 

dissolved oxygen levels in 2005, and reduced food base are likely responsible for reduced 

trout numbers. As catch rates have declined, the condition (kn) of the remaining fish 

appears to be increasing (Figure 2). Although catch rates are low, the size distribution of 

the catch is bimodal and indicates there are small fish in the population (Figure 3). 

Table 1. Number of each species captured during April 2006 Lee’s Ferry sampling 

Species Number captured

Rainbow trout 293 

Brown Trout 2 

Carp 0 

Flannelmouth sucker 2 
YEAR

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

CATCH PER MIN

0

1

2

3

4

5

6

7

Figure 1. Mean catch per minute (electroshocking) for rainbow trout (RBT) by year at 

fixed sites (Lee’s ferry 1991-2006, error bars = 2*SE). 

YEAR

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

kn Lee's Ferry

72

74

76

78

80

82

84

86

88

90

92

Figure 2. Mean condition factor (kn) for rainbow trout (RBT) by year at fixed sites (Lee’s 

ferry 1991-2006, error bars = 2*SE). 
Total Length

0 50 100 150 200 250 300 350 400 450 500

Frequency

0

10

20

30

Figure 3. Length-frequency histogram of all rainbow trout captured during April 2006 

Lee’s Ferry sampling. 

Reference 

Urquhart, N.S., S.G. Paulsen, and D.P. Larsen. 1998. Monitoring for policy-relevant 

 regional trends over time. Ecological Applications 8(2) 246-257.