U.S. Department of the Interior

U.S. Geological Survey

Josh Korman, Ecometric Research, Vancouver, BC

Michael D. Yard, GCMRC, Flagstaff, AZ

January 21, 2015

Natal Origins of Rainbow Trout:

Glen Canyon and Marble Canyon
Natal Origin - Study Objectives

1. Quantify extent of rainbow trout movement from Lees Ferry into Marble 

Canyon and LCR inflow

2. Determine factors that drive trout movement (density, food, growth, 

turbidity, HFEs, etc.)

3. Quantify extent of local reproduction below Lees Ferry.

4. Estimate abundance of rainbow trout in LCR inflow reach for FWS 

Biological Opinion and ‘Trigger’

5. Continue monitoring juvenile humpback chub abundance, growth, and 

survival in the LCR inflow reach (BioOp/trigger)

6. Relate chub survival and growth to trout abundance and temperature 

(critical uncertainty)
GCD to Lees Ferry marking and 

tag recovery

o Tag trout >75 mm

o ~ 10,000 marked/yr

o 2 trips per year

o Nov. ‘11, Oct & Dec ‘12, ’13, ‘14

 Quarterly trips for marking and 

tag recovery by reach

o Apr, Jul, Sep, Jan

o LEES FERRY (I, -5.5 to -2.1 RM)

o HOUSE ROCK (II, 17.2-20.6 RM)

o BUCK FARM (III, 38.2 to 41.6 RM)

o ABOVE LCR (IVa, 60.2 to 61.2 RM)

o BELOW LCR (IVb, 63.4 to 64.9 RM)

Sampling Design
Summary of RBT Catch and PIT Releases

Total Catch

Name: All Reaches GLC GLC UMC MMC LMC DSCLR

Reach: GLC-IVb excl. RD I RD I RD II RD III IVa IVb

Nov-11 16,440 10556 929

Apr-12 11,775 529 552 549 317 119

Jul-12 11,641 675 795 848 339 197

Sep-12 17,897 536 788 842 305 229

Oct-12 22,381 4783 305

Dec-12 12,490 3976 278

Jan-13 12,167 625 776 987 347 336

Apr-13 9,765 716 1,010 879 367 135

Jul-13 8,437 734 828 882 428 279

Sep-13 13,787 994 1,068 741 478 351

Oct-13 12,512 5576 262

Dec-13 8,175 5226 310

Jan-14 8,742 437 1,209 1,198 554 398

Apr-14 7,109 615 1,147 1,155 387 195

Jul-14 6,585 760 1,162 933 428 390

Sep-14 13,156 1047 1,395 1,155 681 456

Oct-14 17,530 6,670 685

Dec-14 12,739 6,765 629

Total 223,328 43,552 11,066 10,730 10,169 4,631 3,085

Total Tags 83,233 Total Tags in Lees Ferrry 54,618

PIT Tag Releases

Preliminary data, do not cite
Summary of PIT Recaptures

Name: GLC GLC UMC MMC LMC DSCLR

Reach: excl. RD I RD I RD II RD III IVa IVb

Nov-11 262 52

Apr-12 91 145 206 149 42

Jul-12 117 220 315 137 60

Sep-12 72 196 213 124 60

Oct-12 334 41

Dec-12 167 52

Jan-13 110 204 202 132 66

Apr-13 103 256 229 133 43

Jul-13 132 201 234 135 59

Sep-13 112 179 128 126 41

Oct-13 538 32

Dec-13 287 46

Jan-14 56 245 216 120 94

Apr-14 52 188 215 125 48

Jul-14 79 222 160 93 52

Sep-14 96 1

Oct-14 333 35

Dec-14

Total 1,921 1,278 2,057 2,118 1,274 565

Total Recaptures 9,213 Percent of Tags Recaptured 11.1%
Proportion of Population that is Marked

Reach I

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Reach II

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.00

0.05

0.10

0.15

Reach III

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.00

0.05

0.10

0.15

0.20

Reach IVa

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Reach IVb

Apr12

Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.0

0.1

0.2

0.3

Trip

Proportion of Population that is Marke
Abundance By Reach

Reach I

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

10

15

20

25

30

Reach II

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

4

6

8

10

12

Reach III

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

2.0

2.5

3.0

3.5

4.0

Reach IVa

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.5

1.0

1.5

2.0

Reach IVb

Apr12Jul12Sep12Jan13Apr13Jul13Sep13Jan14Apr14Jul14Sep14

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Trip

Abundance ('000s per km)
Movement

Upstream 

movement

Downstream 

movement
Movement from Lees Ferry

• 54,618 trout PIT-tagged in Lees Ferry.

• Of 2,239 recaptures of trout released in Lees Ferry (up to and 

including Sep14), only 11 have been recaptured in downstream 

reaches.

• 8 of 11 (73%) recaptures were from Nov. 2011 cohort, which 

represents only 21% of trout PIT-tagged in Lees Ferry.

• Thus a higher proportion of 2011 cohort that was marked 

moved downstream compared to cohorts marked in later years.

• The proportion of trout emigrating from Lees Ferry is variable 

and may be higher for very abundant cohorts.
Longer Distance Movement Among Reaches

GC II III IVa IVb # of Recaps % of Recaps

GC 2228 8 1 0 2 11 0.5%

II 13 1999 12 8 6 39 1.9%

III 1 8 2087 10 7 26 1.2%

IVa 0 0 2 1153 67 69 5.6%

IVb 1 0 1 11 541 13 2.3%

Outside of Release Reach

Release 

Reach

Recapture Reach

Recaptures from Sep 2014 Trip

# of Recaps % of Recaps

Outside of in Sep2014

GC II III IVa IVb Release Reach to Total

GC 214 2 1 0 1 4 36.4%

II 5 590 8 4 4 21 53.8%

III 0 3 365 4 3 10 38.5%

IVa 0 0 0 201 15 15 21.7%

IVb 0 0 0 4 71 4 30.8%

Recapture Reach

Release 

Reach
Reach I

0.8 0.9 1.0 1.1 1.2

Reach II

0.8 0.9 1.0 1.1 1.2

Reach III

0.8 0.9 1.0 1.1 1.2

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

Reach IVa

0.8 0.9 1.0 1.1 1.2

Reach IVb

0.8 0.9 1.0 1.1 1.2

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

Relative Condition Factor
IVa IVb

I 0.01 0.02

II 0.14 0.05

III 0.20 0.18

Destination Reach

Source 

Reach

Estimated Percentage Movement from Lees 

Ferry and Marble Canyon Reaches to LCR 

Reaches

%
Distance from Glen Canyon Dam (km)

Abundance ('000s per km)

0 20 40 60 80 100 120 140

0

5

10

15

20

I II III IVa

a )

Interpolated Abundance GCD-IVb
Movement Distributions from Source Reaches

-15 -10 -5 0 5 10 15

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Movement Distance (km)

Probability

I

II

III

IVa

b )
U W U W U W

0-25 (I)

25-72 (II)

72-122 (III)

122-124 (IVa)

Immigration ('000s)

0

5

10

15

20

 

d )

Pred Est Pred Est Pred Est

 IVa IVb IVa+IVb

Predicted Immigration to LCR Reaches

Source Location
Reach IVa

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

0

100

200

300

400

Year

Fork length (mm)

Local Recruitment
Reach I

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

0

100

200

300

400

Reach II

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013

Sep2013Jan2014Apr2014Jul2014Sep2014

0

100

200

300

400

Reach III

Apr2012Jul2012Sep2012Jan2013Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

0

100

200

300

400

Reach IVa

Apr2012Jul2012Sep2012Jan2013

Apr2013Jul2013Sep2013Jan2014Apr2014Jul2014Sep2014

0

100

200

300

400

Year

Fork length (mm)
Reach I

0.00

0.05

0.10

0.15

0.20

0.25

455565758595105115125135145155165175185195

Observed Nov11 Reach I

Observed Apr12

Predicted Apr12 (Apr12-Jul12 v1)

Predicted Apr12 (Nov11-Apr12)

Reach II

0.00

0.05

0.10

0.15

0.20

0.25

455565758595105115125135145155165175185195

Predicted Apr12 (Apr12-Jul12 v1)

Predicted Apr12 (Apr12-Jul12 v2)

Reach III

0.00

0.05

0.10

0.15

0.20

0.25

455565758595105115125135145155

165175

185195

Fork length (mm)

Frequency

Origin of 125-200 mm Trout in Upper and 

Middle Marble Canyon on Apr12 Trip
Conclusions

1. Abundance

a) High abundance in Lees Ferry and Upper Marble Canyon

b) Much lower abundance near LCR

c) Declining abundance in upstream reaches and increasing 

abundance at LCR reaches

2. Movement

a) Very limited movement for the vast majority of tagged fish

b) The small fraction of fish from upstream reaches that move 

downstream are sufficient to explain the increasing trend in 

abundance at the LCR
Conclusions

2. Movement (con’t)

c) Movement of trout from Lees Ferry to Marble Canyon can be episodic, 

and most fish had probably emigrated before our study began.

d) Recaptures show that both small (age-0) and large (older) trout can 

move from Lees Ferry to Marble Canyon

e) Recent increased downstream movement may be driven by poor 

condition of fish

f) There is local reproduction in middle and lower Marble Canyon that is 

variable across years. May sustain periods of high abundance after 

immigration rates from upstream sources decline.
Conclusions

3. Management

a) Reducing magnitude and frequency of large annual cohorts in Lees Ferry 

may be best way to reduce emigration to Marble Canyon. This may also 

help maintain quality of fishery and avoid cyclical patterns in abundance 

and condition

b) Recruitment to LCR depends on upstream abundance and movement. Thus 

reducing upstream abundance will reduce immigration.

c) There is local reproduction in Marble Canyon that is variable across years. 

Uncertain whether it is an important component of recruitment near LCR. 

Keeping abundance in MC low will likely lower probability of significant 

local recruitment. 

d) Pro’s and con’s of improving trout conditions in Marble Canyon via regular 

floods (may increase condition and reduce movement).