Long-Term Experimental & Management Plan 

(LTEMP) Biological Opinion Conservation 

Measures Update 

Technical Work Group Meeting , January 25, 2024 

Matt O’Neill, Bureau of Reclamation, Upper Colorado Basin 
 

 

 

 

 

 

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 

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 
 

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. 
Incidental Take Parameters – Tier 1 Action Initiation Triggers

Tier 1 – Early Intervention Trigger 2021 2022 2023 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 12,000 15,000 14,000

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

971 2,277 1,004 1,417

OR

b) Sub-adult population estimates in 

mainstem in Juvenile Chub Monitoring (JCM) 

Reach** in fall

≤ 810 for 3 

years

700 100 737 512

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
 

 

 

 

 

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. 
 

 

 

 

 

Incidental Take Parameters – Tier 2 Action Triggers 

Tier 2 – Action Triggers TRIGGER 2021 2022 2023 

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 - - -
Trigger Response 

Close coordination with USFWS 

• Moved 174 fish above Chute Falls in fall 

2023 

• No translocations from LCR

• 600 larval fish collected in spring 2022 
 

 

 

 

 

 

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 

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 

2023 Updates 

Translocations 174 sub-adults translocated above Chute Falls

Monitoring 1 trip to Shinumo Inflow reach (76 humpback chub)

1 trip to CO river inflows around Bright Angel (13), Shinumo (76) & Havasu Creeks (93 humpback

chub) 

1 trip to Bright Angel Creek (1 humpback chub) 

1 trip to Havasu Creek (53 humpback chub) 

Bright Angel 

Creek non-native 

fish removal 

1,705 brown trout & 3,800 rainbow trout (electrofishing)

3 brown trout and 5 rainbow trout removed via weir 

Refuge Support 600 larval humpback chub collected from the LCR, transported to SNARRC

Disease & parasite 

monitoring 

174 humpback chub translocated within the LCR treated for Lernaea

No tapeworm detected in 40 HBC from JCM West (rm 211)
 

 

Razorback Sucker 

Conservation Measure 2023 Update 

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

larval, and small-bodied), September (telemetry and small-bodied) 

• 0 small-bodied razorback suckers 

• 0 larval razorback suckers 

Non-native Species # of Juveniles # of Larvae 

Bluegill 1 0 

Channel catfish 5 0 

Common carp 3 1 

Fathead minnow 902 289

Plains killifish 51 109 

Green sunfish 10 0 

Gizzard shad 2 0 

Western mosquitofish 329 46

Red shiner 99 10 

Rainbow trout 13 1 

Striped bass 1 0 

Walleye 3 5 

Native Species # of Juveniles # of Larvae 

Bluehead suckers 165 2,637

Flannelmouth suckers 2,328 4,151

Humpback chub 1,284 529 

Speckled dace 3,307 2,381

Unidentified Cyprinid 5 0 

Unidentified Sucker 1,205 1 
 

 

 

 

Avian Surveys 

Conservation Measure 2023 Updates 

Partially assist with funding monitoring 

of Southwestern Willow Flycatcher 

(SWFL) every 2 years.

Three surveys conducted (Diamond 

Creek to Pearce Ferry), 6 possible SWFL

detected. Next survey planned for 2025 

Partially assist with funding monitoring 

of Yuma Ridgway’s Rail (YRRA) every 3 

years. 

No surveys planned or conducted – next 

survey planned for 2025 
All Native Aquatic Species – Fish Passage 

Conservation Measure Recent Progress 

Evaluate means to prevent fish passage Hydroacoustics update 

through the dam 

Thermal curtain update 
 

 

 

Fish Assemblage in Forebay Update 

• August 2023 netting found 300 

bluegill and green sunfish

immediately adjacent to the 

dam down to 22m 

• Hydroacoustics appear to find

fish deep (nearly 80m) when

the lake is mixed 
All Native Aquatic Species –Backwater slough 

Conservation Measure Updates 

Complete planning and compliance of a 2023 – TSC report (August 2023), further

plan to alter the backwater slough to discussions at 11:15 

make it unsuitable or inaccessible to 

warmwater non-native species 
 

 

Questions? 

Thanks to our partners for all the hard work and 

collecting the data to help us meet our 

conservation measures! 
 

 

 

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 
 

 

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 
 

Possible Action Status 

-12mi Slough modification Conversations with NPS 

Disrupt bass spawning (short term) LTEMP SEIS in progress

Disrupt bass spawning (long term) Thermal curtain (feasibility) 

Low head power (extremely long term)

Post-2026 EIS in progress 

Mechanical removals Multi-agency GRCA and GLCA, in progress

Understanding and preventing entrainment Tucker trawl net and hydroacoustic studies 

in progress 

Identify new habitat for chub translocations FWS, NPS and others in progress

Understand status of western GC humpback 

chub 

Planning for 2024 field work

Where do we go from here? 
 

 

 

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
All Native Aquatic Species – Temperature Control 

Conservation Measure Updates 

Explore efficacy of temperature Temperature Control Device Update Provided in 2018:

control device 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 
 

Glen Canyon removals 

Glen Canyon Dam to Lee’s Ferry -12mi Slough 

Species Count 

Black crappie 1 

Bluegill 162 

Brown trout 1 

Common carp 17

Green sunfish 3,042

Largemouth bass 2 

Smallmouth bass 141

Striped bass 1 

Walleye 21 

Species Count 

Bluegill 137

Brown trout 162 

Common carp 11,140

Flannelmouth sucker 12 

Green sunfish 4,970

Lepomis sp. 5 

Other nn fish 18

Rainbow trout 114

Smallmouth bass 815
 

 

 

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