Stranding of Rainbo

during Experime

Fluctuating Release

Glen Canyon Dam 

Colorado Rive
Objective

 Examine the spatial and temporal e

rainbow trout (RBT) stranding in thFerry reach of the Colorado River.
Experimental Flow R

 Experimental flow regime comm

1, 2003 and continued through M2003.

 A daily high fluctuating flow elem

a minimum of 5,000 cubic feet pe

beginning at 0100

a maximum of 20,000 cfs beginnin
Various flow regime char

during the last 15 years

2003 5,000 20,000 15,000Experimental Flows 

5,000; 6,000; or 8,000

8,000 day 25,0005,000 night

Interim Flows/ROD Flows

30,500 Labor Day to Easter28,500 Easter to Labor Day

1,000 Labor Day 31,500to Easter3,000 Easter to Labor Day

No Action Alternative/ Pre-EIS (normal flows)

Allowable daily fluctuations (cfs)

Maximum releases (cfs)

Minimum releases (cfs)

Flow regime

(cfs = cubic feet per second)
Glen Canyon Dam 

Experimental Releases

0

5,000

10,000

15,000

20,000

25,000

0:00

2:40

5:20

8:00

10:40

13:20

16:00

18:40

21:20

0:00

2:40

5:20

8:00

10

Hour

Discharge (cfs)
Expected Results of Flow 

Fluctuations

 Benefit native fish Improve quality of Lee’s Ferry rain

fishery by reducing numbers of troin the Lee’s Ferry reach, resulting i

 Unintended stranding of adult trout 
Previous Study

 Glen Canyon Dam and the Colorad

Responses of the Aquatic Biota to Operations, T.R. Angradi, R.W. ClD.A. Kinsolving, D.M. Kubly, and Morgensen. 1992
Differences between 1990 

Studies

 Length of the study period (3 m

months) 

 Frequency (number) of survey Flow conditions and ramping r
Differences between 1990 

Studies

 Water temperatures in stranding po

During the Angradi et al. 1992 stu

temperatures (up to 29 degrees Celhave led to poor water quality and mortality than seen in the 2003 exp
Stranding Sites

 previous findings (Angradi et al. 19 quality and quantity of spawning gr recent observations of spawning ac

relative to the site,

 extent of stranding conditions, andlikelihood of stranding (e.g., morph

the site, seepage rates, etc.).

 Several aspects were taken into con

to determine if the site should be cpotential stranding area:

Stranded Fish

 A total of 503 adult fish were found stra

this 3 month study.

 7% (36 fish) of stranded fish were dead 

0

20406080

100

01/08

01/14-01/15

01/21-01/22

01/28-01/29

02/04-02/05

02/11-02/12

02/18-02/19

02/25-02/26

03/04-03/05

03/11

Date

Frequency

RBT # likely to live (n=467) RBT # likely to d
Stranded Fish cont.

1990 The mean TL of 

RBT (Angradi et al.) was 437 mm (SD = 53, n = 496).

 The mean TL of 

RBT (AGFD) in 1991 was 352 mm (SD = 117, n = 228).

2003

 Stranded 

ranged fr455 mm mean of 63, n = 3g to 1,20

 The mea

(AGFD) (SD = 88
Predation on Stranded Fi

 28% of the stranded fish, both aliv

showed indications of predation.

Fish that were still alive had talon 

their flanks, while dead fish had wvaried from talon marks along the missing portions of their anatomy.
Predation on Stranded Fi

 Stranded fish with talon 

marks present. 

 Stranded fish that exhibits 

signs of predation. 
Stranded Fish by Site

Site 10

2 1 1 4 

Site 9

0

0 1 1 

Site 8

0

0

0

0

Site 7 1 0 1 2 

Site 6

0

0

0

0

Site 5 386

0

2 388 

Site 4 30

0

2 32

Site 3 27

0

7 34 

Site 2

2

0

0

2

Site 1 19

2 19 40 

RBT Total

dead

RBT likely RBT likely 

to die

RBT 

likely to likely to 

live

Site
Stranded Fish by Site con

Site 1

 40 fish were observed 

 19 (48 %) of those fish were dead  10 of the 19 (53 %) were found at 

stranding area

 High potential of stranding and mo
Stranded Fish by Site con

Site 1

5,000 cfs

20
Stranded Fish by Site con

Site 5

 388 stranded fish observed  2 were dead 

The difference between this site an

the gravel sloped towards a 1.4 m which enabled stranded RBT to sthe water rose to a sufficient levecould migrate out to the river. 
5,000 cfs

20

Stranded Fish by Site con

Site 5
Conclusions

 Fish were stranded in select sites (n A lower percentage of stranded f

dead in this survey compared to the 

 Cool winter temperatures may 

further loss of stranded fish in pool

 Predation on stranded fish appeare A low down ramp rate appears to b

factor in preventing stranding of fi
Conclusions cont.

 Stranded fish apparently were subs

in size than the population norm.

 Male and female trout were equally 

stranding.

02468

10121416

Green Ripe and Running 

Spawning Con

Frequency
Conclusions cont.

 Concerns of the angling public 

regarding stranding in 2003 wprevalent as anticipated.

 Antecedent conditions may play a 

degree of vulnerability of trout to s
Acknowledgements

 Steve Gloss and other staff at Gran

Monitoring and Research Center 

 Terry Gunn, Jeff English, and othe

Lees Ferry Anglers