U.S. Department of the Interior

U.S. Geological Survey

Biological Opinion Trigger Update: 

January 2015 

Scott VanderKooi

Southwest Biological Science Center

Grand Canyon Monitoring and Research Center

Adult and Sub-Adult Humpback Chub 

Abundance Estimates

(S. Martell, preliminary data, do not cite)

Abundance estimates 

for adults (age 4+)

Abundance estimates for 

sub-adults (age 2+)

ASMR abundance estimate: 

> 7,000 adult Humpback 

Chub. Uncertainty likely 

considerably underestimated.
Adult Humpback Chub Abundance Estimates: 

Multistate Population Model

(Yackulic et al. 2014)

Suggests adult Humpback 

Chub abundance stable from 

2009 – 2012. Confidence 

intervals provide reasonable 

estimates of uncertainty.
0

2000

4000

6000

8000

10000

12000

April 92

May 92

June 92

May 01

April/May 02April/May 03April/May 04April/May 05April/May 06April/May 07April/May 08April/May 09

May/June 10May/June 11

April/May 12April/May 13

April/May 2014

Abundance estimate

>=150 mm TL >=200 mm TL

Annual spring abundances of humpback chub ≥ 150 

mm and ≥ 200 mm in lower 13.6 km of LCR

2014 spring estimates 

indicate Humpback Chub 

abundance stable in the LCR

(Preliminary Data from VanHaverbeke et al. 2014, Do Not Cite)
(Preliminary Data from Yackulic 2014. Do Not Cite.)

Juvenile humpback chub 

survival increased over 2012-

2013 interval. 2013-2014 

estimate approximately equal to 

2012-2013 value.

Sampling Interval

Annual Survival of Humpback Chub (40-99 mm) 

in the Colorado River Study Site
2014 Water Temperatures: Colorado River near 

Little Colorado River Confluence

(UGSG gage 09383100: http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09383100)

12 °C threshold met or 

exceeded in each month from 

April through December
0

500

1000

1500

2000

2500

3000

3500

May 2001

April/May 2002April/May 2003April/May 2004April/May 2005April/May 2006April/May 2007April/May 2008April/May 2009

May/June 2010May/June 2011

April/May 2012April/May 2013April/May 2014

Abundance estimate

Year

Spring LCR 150-199 mm humpback 

chub abundance estimates 2014 spring abundance 

estimate of 150-199 mm 

HBC = 2175 

(95% CI: 1861-2489)

(Preliminary Data from VanHaverbeke et al. 2014, Do Not Cite)
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)

Rainbow Trout Abundance By Reach

I – Glen Canyon/Lees Ferry

II – House Rock

III – Buck Farm

IVa – Upstream of LCR

IVb – Downstream of LCR

(Preliminary Data from Korman and Yard 2015. Do Not Cite.)

Three of four 2014 abundance 

estimates exceed BiOp trigger 

level (presented as fish/km).
0

5

10

15

20

Apr 12 Jul 12 Sep 12 Jan 13 Apr 13 Jul 13 Sep 13 Jan 14 Apr 14 Jul 14 Sep 14

Total Catch

Brown Trout Catches:

Below the Little Colorado 

River Reach

Catches peaked in April 

2013, lower levels in 2014 

than in 2013

(Preliminary Data from Yard and Korman 2015, Do Not Cite)
2011 USFWS Biological Opinion

Non-native Fish Control Trigger

 Adult humpback chub <7000 fish?

 OR

 ALL THREE?

 3 of 5 years 150-199 mm humpback chub in the 

LCR drops below 910?

 Temperature <12° C for 2 consecutive years at 

LCR?

 Annual survival of 40-99 mm humpback chub in 

JCM drops 25% from preceding year?

No

No

No

No

No
2011 USFWS Biological Opinion

Non-native Fish Control Trigger

 AND

 Rainbow trout abundance over 760?

 AND

 Brown trout abundance over 50?

Open model estimates exceed threshold 

for three of four trips in 2014 

(Korman and Yard, preliminary data)

Yes

2014 catches lower than in 2013, only 5 total 

caught in Sept. 2014 – catches too low to 

generate abundance estimate

(Yard and Korman, preliminary data)

Unknown
Questions?