U.S. Department of the Interior

U.S. Geological Survey

Predictions, populations, and 

energetic constraints

Project elements: Projects E – I data

E.2 Ecosystem modelling ($50K)

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

(G.1 HBC population modelling)

(J.2 Decision science)

Resource Goals: Humpback Chub, Natural 

Processes, Other Native Fish, Rainbow trout, 

Nonnative Invasive Species

Annual Reporting

January 13, 2020

Wurtsbaugh et al. 2014
Action

System 

State

time

System 

State

Action

System 

State

Action
Prediction, models and management

"An approximate answer to the right question is 

worth a great deal more than a precise answer to 

the wrong question.“ - Tukey

Adult BNT Abundance 

Adult BNT CPE 

Preliminary data, do not cite
Prediction, models and management, 

cont.

 Very few ecological questions are definitely 

answered with single studies.

 Biomedical studies –75-90% of published, 

preclinical results can be reproduced

 Even worse when a single study with replication 

equal to 1 or 2

 But statistical significance shouldn’t be basis 

for management decisions (Trends)
A working example of Adaptive 

management: Mid-Continent Mallard 

Harvest

 Initiated 1995

 4 distinct hypotheses

 Abundance estimated by aerial survey

 Model weights updated: comparison of 

estimate with predictions
Mid-Continental Mallard Harvest has been informed by 

4 models for over 20 years with model weights updated 

over time to reflect learning from data

Nichols et al., 2019
Harvest policy has been updated adaptively 

with differences in model weights

Nichols et al., 2019
We have been working to develop similar approaches 

for updating decision rules with monitoring results

Adapted from Donovan et al., 2019; Yackulic et al., 2019
Outline

 Brown trout update

 Energetic constraints

 Rainbow trout recruitment models

 Native fish near Little Colorado River

 Energetics/recruitment of Flannelmouth sucker in 

western Grand Canyon
BNT integrated model

 Uses mark-recap data from USGS and catch 

from AZGF

 Expected lambda had ~50% probability of 

being greater than 1 (Runge et al., 2018)

 Last year showed N for adults sensitive to 

priors because of lack of mark-recap data

 Allowed to collect mark-recap data in 2019
With a little 

more markrecap, 

models with 

different 

priors are 

starting to 

estimate 

similar 

abundances.

Preliminary data, do not cite
Abundance estimates for larger size classes are more 

similar now between models with different priors (red 

and blue represent different priors on survival)

Preliminary data, do not cite
But models still disagree a little regarding 

magnitude and timing of reproduction

Preliminary data, do not cite
There is no doubt population growth 

will continue if things don’t change

Preliminary data, do not cite
Outline, cont.

 Brown trout update

 Energetic constraints

 Flannelmouth sucker in western Grand Canyon

 Rainbow trout recruitment models

 Humpback chub condition
Primary production and the transfer of energy through 

food webs constrain fish production. 

Ruegg et al., in review; Preliminary data, do not cite
Conceptual model
How changes in energetic constraints will effect vital rates 

will depend on life history / metabolism, but should be most 

clear in species that dominate consumption in a local 

community. Sub

-adult cpe

GPP (g O2 m-2 d-1)

Preliminary data, do not cite
Unclear what drives GPP in western 

Grand Canyon, but we previously (a 

priori) hypothesized that 

phosphorous in Dam releases may 

be limiting energy (and thus fish) in 

Lees Ferry and near the Little 

Colorado River.
Rainbow trout recruitment models fit 

for 2017 annual reporting meeting

Model using SRP and existing rainbow trout population size as covariates 

previously outperformed model used in LTEMP EIS.

Out of sample R2: 0.85 Out of sample R2: -0.33

Preliminary data, do not cite
Near the LCR, the picture is less definitive.

Preliminary data, do not cite
Correlation between SRP and chub condition 

has not been as close in recent years, but SRP 

measured far upstream.

Preliminary data, do not cite
Take homes

 Predicting the actual quantity of interest (not a proxy) 

with uncertainty should be the goal of applied 

science.

 Brown trout are likely to continue to increase in the 

short term.

 Energetic constraints exist for fish populations in all 

parts of the canyon, and phosphorous is strongly 

linked to rainbow trout and more weakly linked to 

humpback chub. 
Thank you for your attention!