Long-Term Experimental & Management Plan 

(LTEMP) Biological Opinion Conservation 

Measures Update

Technical Work Group Meeting , January 26, 2023

Kerri Pedersen, Bureau of Reclamation, Upper Colorado Basin 
Incidental Take Parameters – Tier 1 Action Initiation Triggers

Tier 1 – Early Intervention Trigger 2020 2021 2022 3-year average

1. Combined adult (>200 mm) humpback

chub (HBC) in the Colorado River mainstem 

aggregation (≥2,000) and in the Little 

Colorado River (≥7,000)

≤ 9,000 15,000 12,000 15,000

Not applicable. Trigger for 

adults based on annual

population estimate

OR

2. Recruitment of sub-adult HBC (150-199

mm) does not equal or exceed estimated 

adult mortality

a) Sub-adult population estimate in LCR in 

spring

≤ 1,250 for 3 

years

993 696 2,056 1,248

OR

b) Sub-adult population estimates in 

mainstem in Juvenile Chub Monitoring (JCM) 

Reach** in fall

≤ 810 for 3 

years

200 700 100 333

Model estimates for adults are rounded to the nearest 1,000 and to the nearest 100 for sub-adults.

*No estimate was obtained for sub-adults in LCR in spring 2020 due to COVID-19 restrictions. The 2020 number was estimated 

by using data collected and abundance estimated from fall 2019.

**JCM Reach is RM 63.45-65.2 of mainstem
Incidental Take Parameters – Tier 2 Action Triggers

Tier 2 – Action Triggers TRIGGER 2020 2021 2022

Mechanical Removal implemented

If adult HBC (≥200 mm) as estimated by the HBC 

population model <7,000 N/A N/A N/A

Terminate Mechanical Removal 

If predator index is <60 rainbow trout/km in JCM 

reach - - -

and immigration rate is Low (to be determined) - - -

OR

HBC population estimates > 7,500 - - -

and survival rates of sub-adult chub exceeds adult mortality for at 

least 2 years - - -
Two-Tier Approach

 Tier 1 – emphasize conservation 

actions that take place during adult 

or sub-adult population declines.

 Tier 2 – predator removal if 

conservation actions are 

unsuccessful.
Humpback Chub – Tier 1 Action Triggers

• If the # of adult HBC (≥200 mm) in the LCR aggregation (includes the 

Colorado river mainstem and the LCR population) is < 9,000 

OR

• If recruitment of sub-adult HBC (150-199mm) ≤ estimated adult mortality 

such that:

• a) Sub-adult abundance <1,250 fish (3-yr average) in the spring LCR 

population estimates.

OR

• b) Sub-adult abundance <810 fish (3-yr average) in the fall mainstem Juvenile 

Chub Monitoring reach.
Hypotheses for Decline in Sub-Adults

• Poor recruitment

• Absence of winter floods

• Lack of food/poor habitat 

quality in the Little Colorado 

River

• Possible predation by catfish & 

other species
Trigger Response

Close coordination with USFWS

• Submitted Trigger Response Report for 2021-2022

• No fish available in spring 2022 to transfer, moved 

196 fish above Chute Falls in fall

• No larval fish collected in spring 2022

• 2023- action will be determined after larval 

production assessed
Conservation Measures as described in the 2016 

LTEMP ROD & Biological Opinion

Resource Conservation Measures

Humpback chub

Translocations

Monitoring

Non-native fish removal

Refuge support

Disease & parasite monitoring

Razorback sucker Monitoring

Determine hybridization extent

All native aquatic species

Non-native fish management

Evaluate temperature control

Evaluate fish passage

Alter -12 mile backwater slough 

Southwestern willow flycatcher Monitor every 2 years

Yuma Ridgway’s rail Monitor every 3 years
Humpback Chub

Conservation 

Measures

2022 Updates

Translocations 196 sub-adults translocated above Chute Falls (October 2022)

Monitoring 1 trip to Shinumo Inflow reach (Late August/Early September 2022)

1 trip (June 2022) to CO river inflow around Bright Angel, Shinumo & Havasu Creeks (93 

humpback chub)

1 trip in June 2022 to Bright Angel Creek (21 humpback chub – including 14 during electrofishing 

season)

2 trips (October 2021 & May 2022) to Havasu Creek (272 humpback chub)

Non-native fish 

removal

4,274 brown trout & 4,216 rainbow trout (electrofishing)

No trout removed via weir due to monsoonal flooding

Refuge Support No larval fish available for collection in spring 2022

Disease & parasite 

monitoring

32 humpback chub sampled at LCR – 4 tapeworms detected in 3 fish.

47 humpback chub sampled in Western Grand Canyon (RM 273) – 2 tapeworms detected in 2 fish

USFWS & AZGFD examined all fish caught during routine monitoring for external parasites (Lernea

& others)
Razorback Sucker

Conservation Measure 2022 Update

Monitoring • Monitoring trips in March (larval only), April, May, June, July, August, September 

(small-bodied only)

• 0 small-bodied razorback suckers

• 0 larval razorback suckers

Other Species Identified on Monitoring Trips

Non-native Species # of Juveniles # of Larvae

Brown trout 0 0

Channel catfish 0 0

Common carp 54 54

Fathead minnow 293 185

Green sunfish 1 0

Plains killifish 276 53

Rainbow trout 132 2

Red shiner 71 1

Striped bass 1 6

Walleye 1 0

Western mosquitofish 14 5

Native Species # of Juveniles # of Larvae

Bluehead suckers 239 7,812

Flannelmouth suckers 9,066 10,566

Humpback chub 1,168 444

Speckled dace 6,450 4,121

Unidentified Cyprinid 11 0

Unidentified Sucker 1,964 15
Razorback Sucker Hybridization

Conservation Measure Updates

Determine extent of hybridization of 

razorback suckers

• 2022-Reclamation initiated project with SNARRC

• Expansion of study conducted by Pilar Rinker

• Cross non-hybrid razorback suckers with flannel 

mouth suckers

• Examine genetic & morphological outcomes

• Rates of survival & growth
Avian Surveys

Conservation Measure 2022 Updates

Partially assist with funding monitoring 

of Southwestern Willow Flycatcher 

(SWFL) every 2 years.

No surveys planned or conducted – next 

survey planned for 2023.

Partially assist with funding monitoring 

of Yuma Ridgway’s Rail (YRRA) every 3 

years.

No YRRAs detected during two surveys 

conducted in March and April.
 

 

 

 

All Native Aquatic Species – Temperature Control 

Conservation Measure Updates 

Explore efficacy of temperature 

control device 

Temperature Control Device Update Provided in 2018: 

https://www.usbr.gov/uc/progact/amp/twg/2018-10-10-twgmeeting/Attach_01.pdf

Technical Services Center completed report in 2020 that reviewed 

options & identify unapplied technologies 

(https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/PAP/

PAP-1184.pdf) 

Technology search conducted by Yet2 with various ideas reviewed 

during April 2021 TWG

Temperature Control Update Provided in June 2021 

Includes history of progress on TCD since 1978

Power office looking at appraisal level study to examine bypass 

generation at river outlets 
All Native Aquatic Species – Fish Passage

Conservation Measure Recent Progress

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•

•

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Evaluate means to prevent fish passage 

through the dam

2021 Reclamation initiated 3-part project 

to update 2007-2009 Glen Canyon Dam 

orebay fish survey

Utah State University is sampling the 

forebay to characterize the fish 

community

Reclamation’s Technical Services Center 

(TSC) is sampling forebay using 

hydroacoustics

2022 – Reclamation TSC completed a report 

on Fish Exclusion Options for Glen Canyon 

Dam

2022 – Reclamation initiated a SME panel 

o identify an option for GCD for target

mplementation in Summer 2024.
All Native Aquatic Species –Backwater slough

Conservation Measure Updates

Complete planning and compliance of a 

plan to alter the backwater slough to 

make it unsuitable or inaccessible to 

warmwater non-native species

2018 - Reclamation’s TSC finalized a report

to examine options for reducing 

temperatures in the upper slough

2022 - Reclamation initiated a project with 

TSC to evaluate the options to modify 

considering current conditions.

• Site visit conducted in October 2022

• Update and report tentatively finished in

April 2023
Fish Assemblage in Forebay Update

• Sampling in March, June, 

August & October 2022

• October highlights for forebay

• Less fish (27 non-natives) 

because lake is starting to turn 

over

• Non-natives found down to a 

depth of 23 m (≈14 m in 

previous months)

• Smallmouth bass comprised 1/3 

of total catch (205-325 mm)
Ultrasonic Telemetry

• 20 smallmouth bass (335-482mm) & 10 channel catfish (432-545 mm) 

implanted with ultrasonic transmitters 

• 2 dead – 1 caught by an angler, 1 tag transmitting from bottom (dead)

• 10-station submersible ultrasonic receiver network

• Run through October 2023 – track movement & depth
2023 Sampling Plan 

• Sample shallow habitat closer to dam

• Deploy sensor fish through dam to measure

conditions of passage (March)

• Model probability of successful passage by 

species and season

• Next trip - late February/early March 2023
Questions?

Thanks to our partners for all the hard work and 

collecting the data to help us meet our 

conservation measures!