Mike Dodrill, Charles Yackulic, Ted Kennedy

Grand Canyon Monitoring & Research Center

Drift-Foraging and Bioenergetics Growth Model 

for Rainbow Trout in the Lees Ferry Tailwater
Project Element H3: Development of a 

bioenergetics model for large rainbow 

trout

Trout 

Bioenergetics

Lees Ferry 

Trout 

Research

Lees Ferry 

Foodbase Temperature

Monitoring
 How does the prey size distribution influence 

growth?

 How does the proportion of Gammarus relative 

to other taxa influence growth?

 How does prey abundance influence growth?

 How do different temperature regimes influence 

growth?

Questions:
Foraging

Consumption

Energetic Costs

– Foraging

– Resting

Growth

Metabolism

Waste

Reproduction

Bioenergetics

Model
Biological

Invertebrate Drift

Physical 

Temperature

Daylight

Parameters

Length – Weight

Bioenergetics

Other...

Foraging

Consumption

Energetic Costs

– Foraging

– Resting

Growth

Metabolism

Waste

Reproduction

Bioenergetics

Input Model
Biological

Invertebrate Drift

Physical 

Temperature

Daylight

Parameters

Length – Weight

Bioenergetics

Other...

Foraging

Consumption

Energetic Costs – Foraging – Resting

Growth

Metabolism

Waste

Reproduction

Bioenergetics

Input Model Output
Model Validation

NO Data

April – June / July

 Compare predicted growth with observed
Model Validation

NO Data

April – June / July

Preliminary Data – Do Not Cite 
Model Validation

NO Data

April – June / July

Preliminary Data – Do Not Cite 
Model Validation

NO Data

April – June / July

June / July – Sept. / Oct.

Preliminary Data – Do Not Cite 
Model Validation

NO Data

April – June / July

June / July – Sept. / Oct.

Sept. / Oct. – Dec. / Jan.

Preliminary Data – Do Not Cite 
Model Validation

NO Data

April – June / July

June / July – Sept. / Oct.

Sept. / Oct. – Dec. / Jan.

Dec. / Jan – April 

Preliminary Data – Do Not Cite 
Invertebrate Drift – Size Distribution

Preliminary Data – Do Not Cite 
Invertebrate Drift – Size Distribution

Preliminary Data – Do Not Cite 
Coupled Foraging and Bioenergetics Model 

Lees Ferry

 Current 

Conditions

Preliminary Data – Do Not Cite 
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Current 

Conditions

 Larger Sized 

Prey

 20% increase in 

13mm prey
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Current 

Conditions

 Larger Sized 

Prey

 20% increase in 

16mm prey
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Current 

Conditions

 Gammarus

increased to 

make up 50% of 

prey biomass
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Current 

Conditions

 Gammarus

increased to 

make up 50% of 

prey biomass
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 
Coupled Foraging and Bioenergetics Model 

1992 – 1994 data from Ayers and McKinney 1996 Preliminary Data – Do Not Cite 
Invertebrate Drift

Preliminary Data – Do Not Cite 
Invertebrate Drift

Preliminary Data – Do Not Cite 
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Current 

Conditions

 Increased Prey

 2 fold increase
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 
Coupled Foraging and Bioenergetics Model 

Preliminary Data – Do Not Cite 

Lees Ferry

 Same prey 

availability

 2002 – cool

 2005 – warm

 Base – avg. 

2009 – 2013
 How does the prey size distribution influence 

growth?

 Larger prey = increased growth, even with no 

increase in prey biomass.

 How does the proportion of Gammarus relative 

to other taxa influence growth?

 Higher proportion Gammarus ≠ increased growth

Questions:
 How does prey abundance influence growth?

 Increased prey biomass = increased growth

 How do different temperature regimes influence 

growth?

 More growth under cooler water temperatures

Questions:
 Turbidity – Explore the effects of turbidity on 

trout foraging & growth

 Project Element 9.7 – Application of a 

bioenergetics model in a seasonally turbid river.

 Individual Based Model

Future Applications

Lees Ferry LCR