Difference between revisions of "Humpback Chub Page"

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*[https://cdnsciencepub.com/doi/10.1139/cjfas-2025-0169 Dzul et al., 2026, Integrating mark-recapture, catch, and expert habitat assessments to quantify recent increases in humpback chub abundance over a 200 km long river segment of the Colorado River in western Grand Canyon: Canadian Journal of Fisheries and Aquatic Sciences]
  
 
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Revision as of 12:33, 27 May 2026
Photo courtesy of Arizona Game and Fish Department

HBC distribution USFWS.jpg

Camp chub at the LCR

Description

The humpback chub (Gila cypha) is an endangered, native endemic of the Colorado River that evolved around 3-5 million years ago. The pronounced hump behind its head gives this fish a striking, unusual appearance. It has an olive-colored back, silver sides, a white belly, small eyes and a long snout that overhangs its jaw. Like the Colorado pikeminnow and bonytail, the humpback chub is a member of the minnow family.

The humpback chub is a relatively small fish by most standards – its maximum size is about 20 inches and 2.5 pounds. By minnow standards it is a big fish, though not like the giant of all minnows – the Colorado pikeminnow. Humpback chub can survive more than 30 years in the wild. It can spawn as young as 2 to 3 years of age during its March through July spawning season.

Although the humpback chub does not have the swimming speed or strength of the Colorado pikeminnow, its body is uniquely formed to help it survive in its whitewater habitat. The hump that gives this fish its name acts as a stabilizer and a hydrodynamic foil that helps it maintain position and also probably helped it escape predation by making it difficult to be swallowed by all but the largest pikeminnow. The humpback chub uses its large fins to “glide” in eddy complexes, feeding on insects that become trapped in pockets of slow-moving water. [1]

Status and distribution

The humpback chub was listed as endangered by U.S. Fish and Wildlife Service in 1967 and given full protection under the Endangered Species Act of 1973. Historically, humpback chub were probably limited to the eddy complexes of several canyon reaches of the Colorado River and three of its tributaries: the Green and Yampa rivers in Colorado and Utah, and the Little Colorado River in Arizona. The species was first described in 1946. Before that time, few people ventured into these treacherous canyons – including fishery biologists.

Today, five self-sustaining populations of humpback chub occur in the Upper Colorado River Basin. Two to three thousand adults can occur in the Black Rocks and Westwater Canyon core population in the Colorado River near the Colorado/Utah border. Several hundred to more than 1,000 adults may occur in the Desolation/Gray Canyon core population in the Green River. Populations in Yampa and Cataract canyons are small, each consisting of up to a few hundred adults. The largest population of humpback chub is found in the Grand Canyon -- primarily in the Little Colorado River (LCR) and its confluence with the main stem Colorado River. In 2009, the U.S. Geological Survey announced that this population increased by about 50 percent from 2001 to 2008 to between 6,000 and 10,000 adults. [2]

The 2018 5-Year Status Review concluded that the humpback chub is not in danger of extinction throughout all of its range, but is likely to become so in the foreseeable future; that is, it is a threatened species throughout all of its range. Therefore, the USFWS made a recommendation to downlist the humpback chub to threatened status. [[3]

LTEMP Resource Goal

Meet humpback chub recovery goals, including maintaining a self-sustaining population, spawning habitat, and aggregations in the Colorado River and its tributaries below the Glen Canyon Dam.

Desired Future Condition

• Achieve HBC recovery in accord with the Endangered Species Act (ESA), the HBC comprehensive management plan, and with the assistance of collaborators within and external to the AMP.
• A self-sustaining HBC population in its natural range in the CRE.
• An ecologically appropriate habitat for the HBC in the mainstem.
• Spawning habitat for HBC in the Lower Little Colorado.
• Establish additional HBC spawning habitat and spawning aggregations within the CRE, where feasible.
• Adequate survival of young-of-year or juvenile HBC that enter the mainstem to maintain reproductive potential of the population and achieve population sizes consistent with recovery goals.

Metrics

  • Current Biological Opinion tier of humpback chub in the Little Colorado River (LCR) Aggregation
  • Grand Canyon-wide abundance of adult humpback chub
  • Proportion of Grand Canyon Ecosystem with evidence of all three life stages of humpback chub

 Fish of the Colorado River below Glen Canyon Dam - GCDAMP training prepared by AZFGD

Updates

Humpback chub numbers at the Little Colorado River appear to be stable. Humpback chub numbers in Western Grand Canyon are at an all-time high and numbers are increasing in upstream reaches (up to RM 180-200).


How many humpback chub are there at the Little Colorado River and in Western Grand Canyon?

Hbc 2024lcr.png

There are between 10,000 and 15,000 adult humpback chub at the LCR (2025 Annual Reporting Meeting).

Hbc 2024WGC.png

There are between 50,000 and 120,000 adult humpback chub in Western Grand Canyon (2025 Annual Reporting Meeting).


How many humpback chub are there in all of the Colorado River?

HBCnumbers.png

Most humpback chub are found in Grand Canyon. Populations in the upper basin are considered stable with the exception of the Yampa River population which disappeared in the early 2000's.


What led to the decline and exterpation of the humpback chub population at the Green/Yampa River confluence?

Reintroducing Humpback Chub in Dinosaur National Monument

A White Paper
Approved by Biology Committee: July 14, 2021

Page 4: The need to restore the DNM population was identified in the Humpback Chub SSA (USFWS 2018), and was considered in the Federal Register proposed rule to reclassify the species (85 FR 3586, January 22, 2020): “By 1998, humpback chub were absent or rare in habitats where the species was likely common in the 1940s (Tyus 1998, p. 192), and the decline in the Dinosaur National Monument population likely was the result of the construction of the Flaming Gorge Dam. Humpback chub in the Green River portion of the Dinosaur National Monument population were negatively affected by the cold releases from the Flaming Gorge Dam starting in 1963, and the Yampa River portion was negatively affected by low river flows, especially in the early 2000s. Operational changes since 2006 at Flaming Gorge Dam have improved the water temperature and flow conditions in the Green River, and releases from Elkhead Reservoir since 2006 support improved flow conditions in the Yampa River. Furthermore, the rocky canyon habitats that the humpback chub rely on in Dinosaur National Monument are still present. Although management actions have improved resource conditions in Dinosaur National Monument, immigration from other humpback chub populations is too low for the species to recolonize naturally, and the population is considered extirpated. Because habitats could potentially support a population, the Upper Basin Recovery Program is considering translocation or stocking to restore humpback chub to Dinosaur National Monument. Dinosaur National Monument may now have suitable resource conditions to support a re-establishment effort.”

Page 7: The cause(s) for the decline and functional extirpation of the humpback chub in the Yampa River is unclear. The last few specimens were observed at a time when river discharge was exceedingly low, with a concurrent proliferation of smallmouth bass (Haines and Modde 2007). In August of 2002, the lowest daily flow in 100 years occurred for the Yampa River at 1.8 cfs near Maybell; a flow of 2 cfs had previously been recorded in 1934. It is believed that the low flow of 2002 was the stressor that eliminated an already declining population of humpback chub in the Yampa River. Possible reasons for decline are the compounded effects of low flow and nonnative predaceous and competing fishes, including channel catfish and smallmouth bass, although other native fish species have persisted, including the roundtail chub (Smith 2019).


Also read Ghosts of the Green River: Impacts of Green River Poisoning on Management of Native Fish on how the Green River was rotenoned prior to the closure of Flaming Gorge Dam.


ESA Reclassification

After Scientific Review, the U.S. Fish and Wildlife Service to Propose Reclassification of the Humpback Chub from Endangered to Threatened

Things are looking up for a rare Colorado River fish, the endangered humpback chub. The U.S. Fish and Wildlife Service (Service) recently completed a species status assessment (SSA) and a 5-year status review that concluded the current risk of extinction is low, such that the species is not in danger of extinction throughout all of its range. The SSA explained that the largest population of humpback chub, which is found in the Colorado and Little Colorado rivers in the Grand Canyon of Arizona, is a stable population of about 12,000 adults.

Our SSA also explained that four smaller populations in the Green and Colorado rivers of the upper Colorado River basin have persisted and do not appear to be in immediate danger of extinction. All five populations are wild, persisting without the need for hatchery stocking. These population-monitoring results, when coupled with ongoing flow management and nonnative predatory fish control, mean that the humpback chub will be considered for reclassification from endangered to threatened in the next year.

Although this unique fish is making a big step toward recovery it still needs help. Conservation work by a diverse group of stakeholders has been one of the key contributions in recovering this native fish. State, tribal, federal, and private stakeholders collaborate via the Upper Colorado River Endangered Fish Recovery Program (established in 1988) and the Glen Canyon Dam Adaptive Management Program (established in 1997) to continue the monitoring programs and to reduce threats to this species’ recovery. “Endangered species recovery in altered and heavily managed ecosystems like the Colorado River is a complicated endeavor,” said Service Mountain-Prairie Regional Director Noreen Walsh. “Our best chance for continued success rests in the power of these collaborative partnerships.”

The humpback chub, which was first described as a unique species from collections in the Grand Canyon in the 1940’s, was not discovered in the upper Colorado River basin until the 1970’s. It was placed on the original list of endangered species in 1967. Humpback chub prefer canyon-bound reaches of river where they complete their life cycle in swift, turbulent currents. The species gets its name from the fleshy hump behind its head. That adaptation coupled with large, curved fins allows the species to maintain position in the turbulent flows. Habitat alterations (from changes in river flows and inundation of canyon reaches), and competition and predation from invasive species are the greatest threats to the humpback chub.

In the 5-year review, the Service also recommends that the species recovery plan be revised to incorporate the best available scientific information on the species needs and actions that will be necessary to eventually delist humpback chub. Efforts to propose reclassification and to revise the recovery plan will be ongoing in the coming year. The proposed reclassification rule and the revised recovery plan will be made available for public comment in the future.

LTEMP BiOp Conservation Measures for Humpback Chub Conservation (2016)

Ongoing actions:

Reclamation would continue to support the NPS, FWS, GCMRC, and GCDAMP in funding and implementing translocations of humpback chub into tributaries of the Colorado River in Marble and Grand Canyons, and in monitoring the results of these translocations, consistent with agencies’ plans and guidance (e.g., NPS Comprehensive Fisheries Management Plan [CFMP], FWS Humpback Chub Genetics Management Plan and Translocation Framework, and GCMRC Triennial Work Plan). Translocations allow for opportunities to expand the area occupied by humpback chub and improve the overall status of the species. Specifically, the following would occur:

  • Humpback chub would be translocated from the lower reaches of the Little Colorado River to areas above Chute Falls in an effort to increase growth rates and survivorship.
  • Monitoring would be conducted annually, or as needed, depending on the data required, to determine survivability, population status, or genetic integrity of the Havasu Creek humpback chub population. Intermittent translocations of additional humpback chub in Havasu Creek would be conducted if the FWS and NPS determine it is necessary to maintain genetic integrity of the population.

Reclamation would continue to fund a spring and fall population estimate annually, or at a different frequency as deemed appropriate in consultation with FWS, using a mark recapture based model for the Little Colorado River or the most appropriate model developed for the current collecting techniques and data. Monitoring the chub population allows us to determine its status (whether it is stable, increasing, or decreasing).

Reclamation would continue to fund control or removal of nonnative fish in tributaries prior to chub translocations depending on the existing fish community in each tributary. Reclamation, NPS, and FWS would lead any investigation into the possibility of using a chemical piscicide, or other tools, as appropriate. Tributaries and the appropriate control methods would be identified by the FWS, NPS, Reclamation, and GCMRC, in consultation with the Arizona Game and Fish Department (AGFD). Depending on the removal methods identified, additional planning and compliance may be necessary. Removal of nonnative fishes improves the status of chub and other native fishes by reducing competition and predation. The regulation and control of nonnative fish is a management action identified in the Humpback Chub Recovery Goals (USFWS 2002a) and Razorback Sucker Recovery Goals (USFWS 2002b).

Reclamation would continue to fund the FWS in maintenance of a humpback chub refuge population at a federal hatchery (Reclamation has assisted the FWS in creating a humpback chub refuge at the Southwestern Native Aquatic Resources and Recovery Center [SNARRC]) or other appropriate facility by providing funding to assist in annual maintenance (including the collection of additional humpback chub from the Little Colorado River for this purpose). In the unlikely event of a catastrophic loss of the Grand Canyon population of humpback chub, the refuge would provide a permanent source of sufficient numbers of genetically representative stock for repatriating the species.

Reclamation would continue to assist the FWS, NPS and the GCDAMP to ensure that a stable or upward trend of humpback chub mainstem aggregations can be achieved by:

  • Continuing to conduct annual monitoring of the Little Colorado River humpback chub aggregation (e.g., juvenile chub monitoring parameters). Periodically, an open or multistate model should be run to estimate abundance of the entire Little Colorado River aggregation inclusive of mainstem fish.
  • Supporting annual monitoring in the mainstem Colorado River to determine status and trends of humpback chub and continuing to investigate sampling and analytical methods to estimate abundance of chub in the mainstem.
  • Conducting periodic surveys to identify additional aggregations and individual humpback chub.
  • Evaluating existing aggregations and determining drivers of these aggregations, for example, recruitment, natal origins, spawning locations, and spawning habitat (e.g., consider new and innovative methods such as telemetry or the Judas-fish approach) (Kegerries et al. 2015).
  • Exploring means of expanding humpback chub populations outside of the Little Colorado River Inflow aggregation. Evaluate the feasibility of mainstem augmentation of humpback chub that would include larval collection, rearing, and release into the mainstem at suitable areas outside of or within existing aggregations.

Reclamation would, through the GCDAMP, conduct disease and parasite monitoring in humpback chub and other fishes in the mainstem Colorado. The GCMRC is currently conducting parasite monitoring in the Little Colorado River. However, in order to better understand how/if disease and parasites (primarily Asian tapeworm) are affecting chub and how temperature differences may affect parasite occurrence, this work would be expanded to include investigations of parasites in humpback chub (and surrogate fish if necessary) in the mainstem. Ensuring adequate protection from diseases and parasites is an identified management action needed in the Humpback Chub Recovery Goals (USFWS 2002a) and Razorback Sucker Recovery Goals (USFWS 2002b).

New actions:

Reclamation would collaborate with the FWS, GCMRC, NPS, and the Havasupai Tribe to conduct preliminary surveys and a feasibility study for translocation of humpback chub into Upper Havasu Creek (above Beaver Falls). The implementation of surveys and translocations, following the feasibility study, would be dependent on interagency discussions, planning and compliance, and resulting outcomes of tribal consultation. As stated above, translocations of chub into currently unoccupied habitat aid in expanding the area occupied by the species. In addition, using a tributary to the Colorado River, such as Upper Havasu Creek, protects translocated fish from the effects of dam operations in the mainstem, but still allow for chub in Havasu Creek to contribute to the mainstem population.

Reclamation would, in cooperation with the FWS, NPS, GCMRC, and AGFD, explore and evaluate other tributaries for potential translocations.


LTEMP BiOp Triggers for Humpback Chub (LTEMP BA Appendix D)

Tier 1 Trigger – Early Intervention Through Conservation Actions:

  • 1a. If the combined point estimate for adult HBC (adults defined ≥200 mm) in the Colorado River mainstem LCR aggregation; RM 57-65.9) and Little Colorado River (LCR) falls below 9,000 as estimated by the currently accepted HBC population model (e.g., ASMR, multi-state).

-OR-

  • 1b. If recruitment of sub-adult HBC (150-199mm) does not equal or exceed estimated adult mortality such that:
  1. Sub-adult abundance falls below a three-year running average of 1,250 fish in the spring LCR population estimates, or
  2. Sub-adult abundance falls below a three-year running average of 810 fish in the mainstem Juvenile Chub Monitoring reach (JCM annual fall population estimate; RM 63.45-65.2).

Tier 1 Trigger Response:

  • Tier 1 conservation actions listed below will be immediately implemented either in the LCR or in the adjacent mainstem. Conservation actions will focus on increasing growth, survival and distribution of HBC in the LCR & LCR mainstem aggregation area.

It is expected that the conservation actions proposed below will assist in ameliorating HBC adult losses or recruitment failures from predation. First, ongoing translocations in the LCR above Chute Falls (~300 fish/year) as well as outside the LCR population (e.g., to Havasu Creek, etc.) will continue, regardless of Tier 1 triggers are met or not. New conservation actions will include expansion of existing activities coupled with experimental actions:

  • LCR - Expand translocation actions in the LCR by collecting an additional 300-600 young of the year (YOY) HBC and move to above Chute Falls in October.
  • LCR - Assess efficacy of transporting larval HBC (April/May) into Big Canyon and above Blue Springs in the LCR system. Evaluate growth and survival of these transplants;
  • Mainstem LCR Aggregation - Larval fish will be removed from LCR (April/May) and head-started at Southwest Native Aquatic Resources and Recovery Center (SNARRC). Once fish reach 150-200 mm they will be translocated to the mainstem LCR reach the following year (currently grow-out space at SNARRC is limited to 750 HBC, use of fish for this purpose would reduce numbers available for other actions, e.g. Havasu, Shinumo.);
  • Additional conservation actions as identified and evaluated.

Tier 2 Trigger - Reduce threat using mechanical removal if conservation actions in Tier 1 are insufficient to arrest a population decline:

Mechanical removal of nonnative aquatic predator will ensue:

  • If the point abundance estimate of adult HBC decline to <7,000, as estimated by the currently accepted HBC population model.

Mechanical removal will terminate if:

  • Predator index (described below) is depleted to less than 60 RBT/km for at least two years in the JCM reach (RM 60.0-64.5) and immigration rate is low (the long term feasibility of using immigration rates as a metric still needs to be assessed),

-OR-

  • Adult HBC population estimates exceed 7,500 and recruitment of sub-adult chub exceed adult mortality for at least two years.
PredatorIndexTable.jpg

If immigration rate of predators into JCM reach is high, mechanical removal may need to continue. These triggers are intended to be adaptive based on ongoing and future research (e.g., Lees Ferry recruitment and emigration dynamics, effects of trout suppression flows, effects of Paria River turbidity inputs on predator survival and immigration rates, interactions between humpback chub and rainbow trout, other predation studies).

Links and Information

Projects

Humpback Chub Documents

Presentations and Papers

2026

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

Humpback Chub Genetics

Humpback chub videos

Other Stuff


The interaction of fish, foodbase, and temperature

Fish occupying warmer water have higher metabolic demands than individuals in cooler water, and if these demands increase concurrently with a seasonal decline in prey availability, then growth rates may be reduced. [4]


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