U.S. Department of the Interior

U.S. Geological Survey

Fish populations and aquatic ecosystems 

in Lees Ferry through the Little Colorado 

River

Project elements: Projects A & E – I data

E.2 Ecosystem modelling ($50K)

H.2 RBT recruitment and BNT modelling ($7K)

G.1 HBC population modelling ($110K)

(J.2 Decision science)

Resource Goals: Humpback Chub, Rainbow trout, Invasive Species, 

Natural Processes, 

Annual Reporting

January 20, 2021
What was done?
Broad overview of 

coupled ltemp models

• Rainbow trout dynamic in Lees Ferry and 

outmigration driven by flows.

• Movement to LCR and mechanical 

removal.

• Chub dynamics driven by water temp, 

rainbow trout, and other drivers.
Bug flows Rainbow Trout

TMF

Annual 

Volume

Load following 

(hydropeaking) 

index

Spring HFE 

(max flow)

Fall HFE

Recruitment

RBT Population Size Angler CPE

Growth RBT Abundance 

(>16 inches)

RBT Outmigration

RBT 

downstream

Removal

# mechanical 

removal

Life taken

Adult HBC N

(Korman et al. 2012)
Humpback chub

Colorado River

Water 

temperature

RBT near LCR

CR juveniles

CR adults

Adult HBC 

Abundance 

(min, mean)

Little Colorado River

No flooding

Other stuff

Recruitment

LCR juveniles

LCR adults

(Yackulic et al. 2014)
Recent changes
(Runge et 

al. 2018)
Bug flows Rainbow Trout, cont.

TMF

Annual 

Volume

Load following 

(hydropeaking) 

index

Spring HFE 

(max flow)

Fall HFE

Recruitment

RBT Outmigration

RBT Population Size Angler CPE

Growth RBT Abundance 

(>16 inches)

RBT 

downstream

# mechanical 

removal

Removal Adult HBC N

Life taken
(Korman et al. 2020)

?

?

Spring HFE

+?

+

-
(Preliminary, do not cite)
Rainbow Trout, cont. 2

RBT Outmigration

RBT 

downstream

Removal

# mechanical 

removal

Life taken

Turbidity

Adult HBC N

(Korman et 

al. 2016; 

2020)

(Bair et al., 2018; 

Pierce et al., 2019)

RBT Population Size Angler CPE

Recruitment

Growth RBT Abundance 

(>16 inches)

Bug flows

TMF

Annual 

Volume

Load following 

(hydropeaking) 

index

Fall HFE

Spring HFE 

(max flow)
Humpback chub, cont.

Colorado River

RBT near LCR

Water 

temperature Removals

Turbidity

CR juveniles

CR adults

Little Colorado River

No flooding

Other stuff

Recruitment

LCR juveniles

LCR adults

CF translocated 

juveniles

CF adults

Adult HBC 

Abundance 

(min, mean)

(Yackulic et al., 2018; 2020; 

In Review; Dzul et al., In 

Review, & In prep.)
How does research and monitoring 

inform these models?
Ties to monitoring and research

 Annually we report on most of the quantities of concern based 

on data collected through monitoring and research.

 At the same time, we are updating parameter estimates for 

models.

 In theory, we could update predictions, but lack capacity to 

develop such a framework.

 Monitoring and research projects are not equally informative.
Budgetary issues: failure to prioritize

 Value of monitoring and research projects to predictive 

fisheries models is rarely considered during budget 

process.

 Never make decision to cut fish-related modelling 

elements – instead decrease budgets substantially 

without changing expectations.

 Emerging fish modelling issues are not funded –

exacerbates issue #2. 
What’s on the horizon?

Turning conceptual ecosystem 

models into quantitative models

Flow
Questions

cyackulic@usgs.gov