Welcome to the Lower Colorado River Multi-Species Conservation Program
Lower Colorado River Multi-Species Conservation Program Balancing Resource Use and Conservation

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      (Gila elegans)
Adult bonytail being stocked into the Imperial Ponds - Photo by ReclamationAdult bonytail recently harvested from Achii Hanyo rearing station - Photo by ReclamationJuvenile Bonytail in display tank - Photo by Reclamation

General Description

The Bonytail’s scientific name is Gila elegans. The vernacular bonytail was used to identify numerous other native chubs of the Colorado River, resulting in potential inaccuracy’s in historical literature. Bonytail were first scientifically described by by Baird and Girard in the Zuni River, New Mexico, in 1853 during early expeditions to the Colorado River Basin.

Bonytail are a streamlined fish, typified by its small head, slender body, and thin, pencil-like caudal peduncle. Individuals may reach lengths up to or greater than 550 mm (about 22 inches). These large individuals are believed to be up to 50 years old. The head is compressed and the snout overhangs the mouth. The streamlined body is characterized by a smooth hump (smaller than that of the humpback chub) located directly posterior to the head of adult fish, and a narrow caudal peduncle. Coloration is typically grey dorsally, fading to white ventrally, with yellowish pigmentation near the base of the pectoral and pelvic fins. Spawning fish (males and females) display tuberculation on the head and fins. Young bonytail are easily confused with roundtail chubs and humpback chubs, particularly at smaller size classes and in areas of known coexistence.

Legal Status

The bonytail is currently listed as federally “endangered” under the Endangered Species Act of 1973, as amended (ESA; 16 U.S.C. 1531 et. seq.), under a final rule published on April 23, 1980 (45 FR 27710).

Bonytail was listed as threatened in Arizona in 1978.  Bonytail is currently classified as a “wildlife species of concern” in Arizona.

Bonytail was listed by the state of California as “rare” in 1971, and later reclassified as “endangered” in 1974.

Bonytail were classified as endangered in Nevada by 1976.


The bonytail diet is omnivorous and comprised of a wide variety of aquatic and terrestrial insects, small fish worms, algae, plankton, and plant debris. During spawning, adults were observed consuming their own gametes, as well as young razorback sucker larvae.

More Information

Additional information on this species, as well as source documentation, can be found in the species accounts located at this link (PDF). The Conceptual Ecological Model (CEM) can be found here (PDF), and the latest update can be found here. Technical Reports on this species can be found here.

U.S. Fish and Wildlife Service. 2008. Bonytail (Gila elegans) Recovery Goals: amendment and supplement to the Bonytail Chub Recovery Plan. U.S. Fish and Wildlife Service, Mountain-Prairie Region (6), Denver, Colorado, located at this link (PDF).

Updated January 7, 2020

Bonytail were historically widespread and common throughout tributaries of the Colorado River and other larger rivers, with captures documented from Mexico to Wyoming. However, during the 1950s, bonytail population abundance began a drastic decline following numerous biotic and abiotic habitat modifications. During the period between 1976-1988, 34 bonytail were captured in Lake Mohave, and some of these fish were incorporated in the establishment of a broodstock; the progeny of which are presently stocked into Lakes Mohave and Havasu as well as a number of UCRB rivers. Very few wild bonytail captures have been documented in recent years and, therefore, little is known about the specific habitat requirements of this unique species.

Early surveys indicate that the bonytail were found in high-gradient, gravelly riverine sections. Bonytail are widely characterized as being adapted to the swifter sections of the Colorado River, with affinity for areas of high flow and rocky habitat. Available information suggests that adult bonytail used fast-water sections, as well as eddies and pool habitats. Pre-impoundment surveys in Flaming Gorge noted that bonytail were apparently fairly common in the Flaming Gorge area of the upper Green River, a canyon-bound, relatively fast water section of river.

More recent telemetry studies have revealed that adult bonytail prefer interstitial spaces associated with shoreline riprap during daylight hours in Cibola High Levee Pond, whereas open-water areas are more commonly utilized during the nighttime hours. Intensive telemetric surveillance suggests a high degree of site fidelity, with individually marked bonytail consistently returning to the same cavities formed within the riprap type shoreline. These areas may simulate the boulder fields of many of the UCRB canyon areas where bonytail were once common.

Interestingly, one study suggests that bonytail, when given the opportunity, tend to select water with high levels of total dissolved solids (TDS). Bonytail are able to persist in water with TDS of 4,700 mg/L, the highest tolerance reported for any species of Colorado River Gila species, suggesting an ability to persist despite anthropogenic water quality and habitat degradation.

The Habitat Conservation Plan provides conservation measures specific to each species. Listed below are the species specific conservation measures for the bonytail. Click on the arrows to expand the table.

BONY1—Coordinate bonytail conservation efforts with the USFWS and recovery programs for endangered fish species in the Lower Basin

The LCR MSCP is not a recovery implementation program for the bonytail in the Lower Basin. However, because the planning area overlies bonytail habitats that may be significant components of recovery, and the conservation measures included in the plan can provide resources to a separately organized recovery program, the LCR MSCP will be a contributor to recovery efforts. In that role, the LCR MSCP will interact with the USFWS or any formal recovery program developed in the future for the Lower Basin to ensure that conservation measures included in the conservation plan will be implemented in support of recovery efforts to meet recovery goals for the bonytail in the Lower Basin. This will allow coordination of stocking, research, monitoring, and the funding of other types of conservation efforts inside and outside the LCR MSCP planning area. The LCR MSCP may also use funding programmed for bonytail augmentation (BONY3) and other bonytail conservation measures to implement other recovery activities identified by the USFWS or a future formal recovery program if it is determined through the adaptive management process (Section 5.12 in the HCP) and with concurrence of the USFWS that providing such funding would more effectively contribute to recovery of the bonytail. The LCR MSCP conservation measures are designed to be flexible and adaptable to allow for changing needs and priorities in bonytail recovery efforts over the term of the permit. The LCR MSCP recognized that this flexibility would be extremely valuable as interim benchmarks to meeting the 2002 recovery goals and changes to recovery needs identified from research and monitoring were developed over time. In order to define the amount of conservation the LCR MSCP would contribute for the bonytail, some assumptions on how funds would be spent were made for the purposes of costing out the program. The adaptive management program, relying on research, monitoring, and other information, will guide the implementation of the conservation measures to mitigate incidental take and contribute to recovery.

BONY2—Create 360 acres of bonytail habitat

Create 360 acres of backwater with depth, vegetation, and substrate characteristics that provide the elements of bonytail habitat. This created backwater will also provide habitat for the razorback sucker. Created backwaters will be designed and managed as described in Section in the HCP.   At a minimum, created backwaters will contain the physical, chemical, and biological conditions suitable for the establishment and maintenance of healthy fish populations in the LCR.

BONY3—Augment bonytail populations (Minor Modification)

Steering Committee Motion 11-003  10-27-10
Fish and Wildlife Service Approval  1-4-11

The LCR MSCP will provide a level of funding to support implementation of a stocking/augmentation program for the bonytail providing for the stocking of up to 620,000 subadult bonytail (at least 300 mm in length) into the designated critical habitat for the species in Reaches 2–3, and in Reaches 4 and 5 of the LCR. The figure of 620,000 fish is not a target number for the LCR but represents an assumption (see BONY1) used to define the extent of funding that would be available, with the understanding that the adaptive management process (see Section in the HCP) would guide the actual stocking program. The elements of the augmentation program divide the conservation effort into the three reaches with numbers of fish per year per reach:

  1. Annually augment 4,000–6,000 subadult fish for 40 years in Lake Mohave to maintain the population (LCR MSCP stocking would follow completion of USFWS's augmentation commitment; estimate 10,000 subadult fish augmented per year for 10 years; consequently, the LCR MSCP commitment is estimated at a mean annual average of 5,000 subadult fish per year for 40 years, for a total of 200,000 fish augmented).
  2. Annually augment 4,000 subadult fish for 50 years in Lake Havasu to maintain the population (200,000 total augmentation).
  3. When technology permits, implement an experimental augmentation of 4,000 subadult fish annually in the Parker-Imperial river reach (Reaches 4 and 5) for ten consecutive years within the 50-year program (40,000 total augmentation) and conduct intensive follow-up monitoring.  These fish are additional to the annual augmentation listed in BONY 3.4.
  4. Annually augment 4,000 subadult fish to establish and maintain populations in the Parker-Imperial river reach (Reaches 4 and 5) for 45 years (180,000 total augmentation).

The number of fish that would be stocked in each reach would be based on the results of monitoring and research. Factors to be evaluated include the survival of stocked fish (including examination of rearing methods, stocking methods, and size of fish stocked), habitat usage, quality and availability, and other information. Stocking of bonytail in any reach would cease, even if the numbers described herein had not been stocked, if monitoring and research demonstrate: (1) no need for additional stockings to provide adults for genetic refuge or for evaluation of management activities related to creating a self-sustaining population (i.e., species recovery goals have been achieved); (2) results of monitoring and research indicate that management activities other than stocking would be more effective in contributing to recovery of the species; (3) there are factors in the reach that are not conducive to the survival of stocked fish to become adults or to be managed toward a self-sustaining population; or (4) that other biological or other factors warrant cessation of stocking. Funds not expended for growing and stocking subadult bonytail would continue to be available to fund other management measures that would minimize and mitigate incidental take and contribute to recovery. Other such management measures would be identified and implemented through the adaptive management process (Section 5.12.1 in the HCP), which requires that any proposed changes in the conservation measures be approved by the USFWS prior to adoption and implementation. As described in conservation measure BONY1, the number of bonytail stocked could also be reduced if funding provided for stocking bonytail is reallocated to support implementation of other conservation measures.

The proposed augmentation program assumes that the USFWS will complete its obligation to stock 125,000 subadult fish in Lake Mohave (an estimated 100,000 subadult fish remain to be stocked) and that the LCR MSCP will incorporate annual augmentations to maintain the Lake Mohave population that becomes established as a result of USFWS's augmentations. All fish stocked under the LCR MSCP augmentation program would meet applicable disease and parasite control protocols established for fish health.
BONY4—Evaluate and develop, if necessary, additional bonytail rearing capacity

Additional rearing capacity, if needed, would be developed through cooperation between AGFD, CDFG, NDOW, USFWS, and other LCR MSCP participants, or fish may be acquired from other sources. During the initial years of implementation, the LCR MSCP will evaluate the efficacy of existing or proposed bonytail production programs and facilities and develop the methods required to produce and rear the fish. Given the minimal information on the biology and ecology of the species, the success of large-scale production is uncertain. Also, the target size for subadults is 300 mm total length. Existing information indicates that hatchery and pond rearing of bonytail to 300 mm is difficult, requiring specific nutritional and spatial conditions. Opportunities to increase bonytail production could include defining feeding regimes, raceway and pond densities, and other factors that affect growth and testing the efficacy of raising fish in disconnected backwaters that are predator free. In the context of the integrated landscape mosaic (e.g., use of created disconnected backwaters), a “pilot project” grow-out facility will be developed for bonytail within the LCR MSCP planning area.

Until rearing capacity and aquaculture techniques can be increased sufficiently to produce the numbers of fish required for the augmentation strategy described in conservation measures BONY3, the LCR MSCP will stock the numbers of fish that can be produced up to the amounts described above. Annual augmentation targets for the first years of the program, therefore, may need to be shifted to later in the program, when increased rearing capacity is at full capacity. The LCR MSCP augmentation strategy assumes that fish production technology can be developed sufficiently to produce the numbers of subadult fish required for augmentation. If production of sufficient numbers of fish for the augmentation program is not possible, however, in addition to augmenting the numbers of fish that can be produced, the LCR MSCP will focus the expenditure of remaining augmentation funds on other types of management activities that will benefit the species (e.g., additional research, habitat improvements).
BONY5—Conduct monitoring and research, and adaptively manage bonytail augmentations and created habitat Humpback

Monitoring and research will be conducted to gather information necessary to adaptively manage bonytail conservation, including aggressive monitoring of fish response following augmentations to gather information regarding habitat use and fish movement, to increase the success of subsequent management of the species.

The LCR MSCP will implement an adaptive management process to reevaluate the augmentation strategy for bonytail, based on the results of monitoring and research. Monitoring and focused research will be a component of the adaptive management process. For example, the stocking of 8,000 subadult fish for 5 consecutive years below Parker Dam (conservation measure BONY3, submeasure 3) will be conducted as an adaptive management experiment, elements of which will include focusing augmentations in locations that currently support the species, followed by intensive monitoring and research for an estimated 7–8 years. Release of fish into the LCR will target a mix of riverine and lacustrine habitat types in Reaches 2 and 3. Augmented bonytail released will be marked with an appropriate batch-marking methodology and a statistically valid subset of released fish may also be PIT tagged or identified with other appropriate technology providing a similar level of individual fish identification. Monitoring will focus on determining key environmental correlates affecting survival, growth, movement, and reproduction (e.g., key habitat [e.g., depth, velocity, channel form, cover, substrate], continuity, water temperature, food, predation).

Following the 7–8-year intensive monitoring and research period, the information and insights gained will focus expenditure of the remaining funds on those management activities potentially contributing the most to achieving the recovery goals for bonytail. As appropriate, the management activities may include changes to the LCR MSCP participant's proposed augmentation approach, rates, and targeted areas. The monitoring and research information will also guide maintenance, enhancement, and creation of bonytail habitat (e.g., backwaters).

MRM5—Monitor selenium levels in created backwater and marsh land cover types, and study the effect of selenium released as a result of dredging activities

Conduct monitoring of selenium levels in sediment, water, and/or biota present in LCR MSCP created backwater and marsh land cover types. If monitoring results indicate that management of the LCR MSCP conservation areas increases levels of selenium in created backwaters and marshes or in covered species that use them, the LCR MSCP will undertake research to develop feasible methods to manage the conservation areas in a manner that will eliminate or compensate for the effects of increased selenium levels. If feasible management methods are identified, they will be implemented. This conservation measure will include monitoring the effects of dredging and dredge spoil disposal associated with creating and maintaining backwaters and marshes. If monitoring results indicate that current or future dredging and dredge spoil disposal methods increase selenium levels, the LCR MSCP will only implement methods that will have the least effect on selenium levels. A study will also be conducted to look at the effects of potential releases of selenium from dredging in general.

AMM1—To the extent practicable, avoid and minimize impacts of implementing the LCR MSCP on existing covered species habitats

To the extent practicable, establishment and management of LCR MSCP–created habitats will avoid removal of existing cottonwood-willow stands, honey mesquite bosques, marsh, and backwaters to avoid and minimize impacts on habitat they provide for covered species. Temporary disturbance of covered species habitats, however, may be associated with habitat creation and subsequent maintenance activities (e.g., controlled burning in marshes and removal of trees to maintain succession objectives). LCR MSCP conservation measures that could result in such temporary disturbances will, to the extent practicable, be designed and implemented to avoid or minimize the potential for disturbance. In addition to implementing AMM3 and AMM4 below, these measures could include conducting preconstruction surveys to determine if covered species are present and, if present, implementing habitat establishment and management activities during periods when the species would be least sensitive to those activities; or redesigning the activities to avoid the need to disturb sensitive habitat use areas; staging construction activities away from sensitive habitat use areas; and implementing BMPs to control erosion when implementing ground disturbing activities.

AMM4—Minimize contaminant loads in runoff and return irrigation flows from LCR MSCP created habitats to the LCR

LCR MSCP–created habitats that require irrigation to establish and maintain vegetation to provide habitat will be designed and managed to minimize contaminant loads that could return to the LCR as runoff or return flow. Measures will include vegetation establishment methods that minimize the need for application of herbicides, pesticides, and fertilizers and designing irrigation methods and new irrigation infrastructure to reduce runoff and return-flows to the extent practicable. Use of pesticides is not a covered activity. Pesticides used to establish and maintain LCR MSCP habitats, however, will be applied in accordance with EPA restrictions and, as needed, authorization for their use will be sought under separate permits.

AMM5—Avoid impacts of operation, maintenance, and replacement of hydroelectric generation and transmission facilities on covered species in the LCR MSCP planning area

To the extent practicable, before implementing activities associated with OM&R of hydroelectric generation and transmission facilities, measures will be identified and implemented that are necessary to avoid take of covered species where such activities could otherwise result in take. These measures could include conducting surveys to determine if covered species are present and, if so, deferring the implementation of activities to avoid disturbance during the breeding season; redesigning the activities to avoid the need to disturb covered species habitat use areas; staging of equipment outside of covered species habitats; delineating the limits of vegetation control activities to ensure that only the vegetation that needs to be removed to maintain infrastructure is removed; stockpiling and disposing of removed vegetation in a manner that minimizes the risk of fire; and implementing BMPs to control erosion when implementing ground disturbing activities.

AMM6—Avoid or minimize impacts on covered species habitats during dredging, bank stabilization activities and other river management activities

To the extent practicable, before initiating activities involved with river maintenance projects, measures will be identified and implemented that avoid or minimize take of covered species where such activities could otherwise result in take. Such measures could include alternative methods to achieve project goals, timing of activities, pre-activity surveys, and minimizing the area of effect, including offsite direct and indirect effects (e.g., avoiding or minimizing the need to place dredge spoil and discharge lines in covered species habitats; placing dredge spoils in a manner that will not affect covered species habitats).

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