U.S. Department of the Interior

U.S. Geological Survey

Humpback chub (Gila cypha) 

that spawn in the Little Colorado 

River: status and potential 

drivers

Annual Reporting for FY15

January 27, 2016

Charles B. Yackulic (US Geological Survey –

GCMRC), Presenter – email: cyackulic@usgs.gov

Maria Dzul (US Geological Survey – GCMRC) 
Quick review of Chub Life History Basics
3

• Majority of chubs recruitment in the 

Little Colorado River .

• Some proportion of juvenile chub 

leave Little Colorado River, and most 

of this outmigration occurs during July 

– Sept. of their first year.

• Juvenile chub 

growth thought to 

be driven primarily 

by temperature. 

Juvenile chub 

survival thought to 

be affected by 

trout.

• Most adults live in Colorado River and migrate back to Little Colorado River to 

spawn, small proportion of adults appear to live year-round in Little Colorado River.

Basics of Chub Life History around the Little Colorado River (LCR)
Little Colorado River 10

8

6

4

2

0

Fish Length (mm)

6

5

4

3

2

1

0

Colorado River 

Chub that grow up in the Colorado River take much longer to reach maturity (cold water).

preliminary data. Do not cite.
Outline

 Recruitment in Little Colorado River

 Juvenile survival and growth in the Colorado 

River

 Subadult growth in Little Colorado River & 

Colorado River

 Adult Chub
2 4 6 8 10 12 14

0

1000

2000

3000

4000

Subreach

Abundance HBC - 

2013

2014

2015

2.5% quantile 50% quantile 97.5% quantile

2013 12108 15380 20732

2014 9635 12118 15321

2015 16823 21470 27512

preliminary data. Do not cite.
Outline

 Recruitment in Little Colorado River

 Juvenile survival and growth in Colorado 

River

 Subadult growth in Little Colorado River & 

Colorado River

 Adult Chub
HBC juvenile 

abundance in 

Colorado study 

site

*

*

*

preliminary data. Do not cite.
Annual juvenile chub (40-99 mm) survival in 

Colorado River, much of the variation in survival 

can be attributed to changes in the size 

structure within this range.

preliminary data. Do not cite.
Mini-multistate

 Small (40 – 59 mm), medium (60 – 79 mm), 

large (80-99 mm) juveniles.

 Survival increases with size, growth declines

 Correlates of survival: 

 Trout (-)

 # of days with Turbidity greater than 50 FNU (-)

 Correlates of growth: 

 T>12 °C (+)

 # of days with Turbidity greater than 50 FNU (+)
(A year with less days turbidity 

over 50 FNU at the gauge at 

Phantom Ranch)

(A year with more days of 

turbidity over 50 FNU at 

the gauge at Phantom 

Ranch)

preliminary data. Do not cite.

Annual Chub Survival for different sizes of chubs, under different environmental conditions 

Rainbow Trout Abundance
Temperature seems to act like a threshold.

When it gets dirty, chub start growing 

(but they also start getting eaten)

preliminary data. Do not cite.

12°C
Outline

 Recruitment in Little Colorado River

 Juvenile survival and growth in Colorado 

River

 Subadult growth in Little Colorado River & 

Colorado River

 Adult Chub
Smaller subadults (100-149 mm)

Larger subadults (150-199 mm)

Subadult Abundance chub in Colorado River study site

preliminary data. Do not cite.

Abundance of subadult chub in the Colorado River Study Site (x1000)

Year 
preliminary data. Do not cite.

Juvenile (40-99mm) Abundance of chub in the Colorado 

River study site
Smaller subadults (100-149 mm)

Larger subadults (150-199 mm)

Subadult Abundance chub in Colorado River study site

preliminary data. Do not cite.

Abundance of subadult chub in the Colorado River Study Site (x1000)

Year 
0

10

20

30

40

50

Growth of 130mm f 

| | | | | | | | | | | | | | | |

Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan

2009 2010 2011 2012 20

LCR

CR

Best Colorado River model: temperature and turbidity duration

Best Little Colorado River model: temperature and food availability

preliminary data. Do not cite.

Growth of 130 mm humpback chub (mm/month)

Year and Month
Outline

 Recruitment in Little Colorado River

 Juvenile survival and growth in Colorado 

River

 Subadult growth in Little Colorado River & 

Colorado River

 Adult Chub
preliminary data. Do not cite.
Smaller subadults (100-149 mm)

Larger subadults (150-199 mm)

Subadult Abundance chub in Colorado River study site

preliminary data. Do not cite.

Abundance of subadult chub in the Colorado River Study Site (x1000)

Year 
preliminary data. Do not cite.

Year 
So what happened this spring in the Little 

Colorado River?
Little Colorado River – Annual Survival

preliminary data. Do not cite.

Annual Interval (Sept. to Sept.)
Colorado River – Annual Survival

preliminary data. Do not cite.

Annual Interval (Sept. to Sept.)
Proportion of Colorado River fish moving into 

Little Colorado River during spring

preliminary data. Do not cite.

Annual Interval (Sept. to Sept.)

Proportion of Colorado River fish 

moving into Little Colorado River 

during spring
Condition Factor

 Determined by comparing the ratio of 

observed weights of individuals fish to the 

predicted weight based on their total length. 

Predictions are based on a regression of the 

log of weight as a function of the log of 

length. Values over 1 indicate fish that are 

fatter than predicted, values under 1 indicate 

fish that are skinnier.
Adult chub condition – fat or skinny?

preliminary data. Do not cite.

Year and Month
Adult chub condition – fat or skinny? 

preliminary data. Do not cite.

Year
preliminary data. Do not cite.

Drift Biomass (mg/m3)

Year - month
Summary

 Highly variable juvenile recruitment in the Little 

Colorado River

 this can override variation in survival over short time scales

 Temps over 12 °C with turbidity lead to juvenile 

growth in Colorado River.

 Turbidity and trout lower juvenile survival in the 

Colorado River.

 Adult chub appear stable, but skinny and may not 

spawn in great numbers in 2016.
Acknowledgements

 Mike Yard , Josh Korman, Ted 

Kennedy, Mike Dodrill, David Ward, 

Luke Avery, Scott Vanderkooi

 US Fish and Wildlife Service 

 Near Shore Ecology Group

 David Ward, Luke Avery, Michael 

Dodrill and others involved with July 

Little Colorado River

 Glen Canyon Adaptive Management 

Group

 Bureau of Reclamation

 Navajo Nation Department of Fish 

and Wildlife