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

Text Size Increase Font Size Decrease Font Size

Razorback Sucker

       (Xyrauchen texanus)

Razorback SuckerRazorback SuckerRazorback Sucker
  • DESCRIPTION
  • DISTRIBUTION
  • HABITAT
  • CONSERVATION
  • MULTIMEDIA

General Description

The razorback sucker, Xyrauchen texanus,is a member of the Catostomidae family.  The Catostomidae family includes suckers, chubsuckers, and redhorse and has representative native species spread throughout North America, China, and Siberia

The razorback sucker is distinguishable from all other catostomids by the abruptly rising, bony dorsal keel positioned behind the head that is the basis for its common name.  Their body shape is elongated and somewhat laterally compressed with a short and deep caudle peduncle.  The subterminal mouth of razorback suckers has a clefted lower lip, and lateral margins of the lips are continuous and rounded.

Adult razorback suckers can reach 1,000 mm (about 40 inches) in total length but more typically grow to between 400 and 700 mm (about 15 to 28 inches) and generally weigh less than 3 kg (about 7 pounds).  Body coloration transitions from dark brown to olivaceous on the upper surfaces into yellow to white on the lower surfaces.  During spawning season razorback suckers are sexually dimorphic, meaning that males and females do not look alike.  Breeding males display bright yellow and orange laterally and ventrally, dark dorsal surfaces, and tuberculation present, especially on the anal and caudle fins. Females tubercules are smaller in size and rarely extend on to the anal and caudle fins.

Legal Status

The razorback sucker is currently listed as “endangered” under the Endangered Species Act of 1973, as amended (ESA; 16 U.S.C. 1531 et. seq.), under a final rule published on October 23, 1991 (56 FR 54957).

Razorback sucker was listed as threatened in Arizona (Group II status) in 1976, and was later reclassified to threatened – Group III status in 1978.  Razorback sucker is currently classified as a “wildlife species of concern”

In California, they were listed as state rare (this designation was replaced with state threatened in January 1985) in 1971 and became state endangered in 1974.

Razorback sucker were first classified as protected in Nevada in 1981, and were later reclassified as endangered in 1998.

Diet

Razorback sucker diet composition is highly dependent upon life stage, habitat, and food availability.  Exogenous feeding begins at approximately 10 mm TL (approximately 8-19 days post hatching), after which larvae in lentic systems feed mainly on phytoplankton and small zooplankton, while riverine inhabiting larvae are assumed to feed largely on chironomids and other benthic insects.

Later, during the juvenile life stage, razorback suckers undergo an ontogenetic shift in mouth morphology, with the mouth becoming more inferior and allowing for more efficient access to benthic food sources. Thereafter, juvenile razorback suckers likely consume a variety of benthic-associated food items.

As adults, razorback sucker populations display unique diet compositions, depending upon whether the individual lives in a lake or riverine setting.  Riverine fish consume a mixture of benthic invertebrates, algae, detritus, and inorganic materials, with little evidence of zooplankton consumption.  Lake-inhabiting adult razorback sucker consumption is dominated by Cladoceran zooplankton, with some degree of algal and detrital material present in gut contents as well.

More Information

Additional information on this species, as well as source documentation, can be found in the species accounts located at this link (PDF). Technical Reports on this species can be found here.

U.S. Fish and Wildlife Service. 2008. Razorback Sucker (Xyrauchen texanus) Recovery Goals: amendment and supplement to the Razorback Sucker Recovery Plan. U.S. Fish and Wildlife Service, Mountain-Prairie Region (6), Denver, Colorado, located at this link (PDF).

Updated April 4, 2014

Razorback sucker were historically widespread and common throughout the larger rivers of the Colorado River Basin, from Sonora and Baja, California, into Arizona, Colorado, Nevada, New Mexico, and Wyoming. In 1898 a particularly high razorback sucker abundance was noted in Yuma, Arizona.  Other research, however, suggests razorback suckers may have been uncommon historically in the turbulent canyon reaches of the Lower Colorado River Basin.  For instance, razorback sucker in the Green River (the largest known riverine population) were typically found in calm, flat-water river reaches, not turbulent, fast-water canyon reaches. This trend is evident even within basins, as razorback sucker are typically collected in sand-bottomed, low gradient, flat-water reaches outside of the spawning period.  Razorback suckers have also persisted in several of the reservoirs that were constructed in the LCRB; however, these populations were comprised primarily of adult fish that apparently recruited during the first few years of reservoir formation. Residual lake populations of long-lived adults then disappeared 40 to 50 years following reservoir creation and the initial recruitment period following reservoir creation.

Click on the map below to see the distribution of the Razorback Sucker using the interactive GIS map.

Click here to see the Razorback Sucker Distribution area GIS map

 

Historically, adult razorback sucker inhabited virtually all components of riverine habitat.  In particular, low-velocity areas such as backwaters, sloughs, oxbow lakes, and other slackwater portions of the main channel were important for razorback sucker. Seasonally submerged off-river habitats, including bottomlands and other marsh-like, lowland habitats, may have also been important habitat prior to the construction of mainstream dams and the resultant changes in flow regimes, especially during spring-runoff periods.

Seasonal habitat preference has been documented in adult razorback sucker which do well in both lotic and lentic systems. During the spring adults utilized areas of river with deep runs, eddies, backwaters and flooded off-channel habitats, shallow waters with runs and pools typically associated with sandbars during summer months, and low-velocity runs, pools and eddies in the winter.

Spawning occurs in the river on cobble, gravel and sand bars as well as over rocky shoals and shorelines in the reservoirs. Larval razorback sucker require nursery environments, warmer water >14 degrees Celsius, shallow areas that may include backwaters, inundated floodplains, coves and shorelines.

 

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

Razorback Sucker
RASU1—Coordinate razorback sucker conservation efforts with USFWS and recovery programs for endangered fish species in the Lower Basin Implementation Program

The LCR MSCP is not a recovery implementation program for the razorback sucker in the Lower Basin. However, because the planning area overlies razorback 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 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 razorback sucker 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 razorback sucker augmentation (RASU3) and other razorback sucker 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 razorback sucker.

The LCR MSCP conservation measures are designed to be flexible and adaptable to allow for changing needs and priorities in razorback sucker 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 razorback sucker, 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.

RASU2—Create 360 acres of razorback sucker habitat

Create 360 acres of backwater with water depth, vegetation, and substrate characteristics that provide the elements of razorback sucker habitat. This created backwater will also provide habitat for the bonytail. Created backwaters will be designed and managed as described in Section 5.4.3.4 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.

RASU3—Augment razorback populations (Minor Modification)

Steering Committee Motion 11-001  10-27-10
Fish and Wildlife Service Approval Letter 1-4-11

The LCR MSCP will provide a level of funding to support implementation of a stocking/augmentation program for the razorback sucker, providing for the stocking of up to 660,000 subadult razorback suckers (at least 300 mm in length) into the designated critical habitat for the species in Reach 3, and in Reaches 4 and 5 of the LCR. The figure of 660,000 fish is not a target number for the LCR but represents an assumption (see RASU1) used to define the extent of funding that would be available, with the understanding that the adaptive management process (see Section 5.12.2.2 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. Implement an experimental augmentation, at a site(s) to be selected in cooperation with USFWS and state game and fish agencies, of 12,000 subadult razorback suckers each year for ten years (120,000 total augmentation), and conduct intensive follow-up monitoring. When razorback sucker production capacity allows, razorback sucker production will be ramped up, with a target production of 120,000 300-mm subadult fish over a 10-year period (i.e., about 12,000 subadult fish per year). Of the 120,000 subadult fish, 6,000 300-mm fish will be stocked annually above Parker Dam and 6,000 300-mm fish below Parker Dam to facilitate maintenance of current juvenile and adult abundance. The augmentation program will also support maintenance and protection of the genetic diversity of existing populations in Lake Mohave (conservation measure RASU4).
  2. Annually augment the existing population by stocking up to 6,000 subadult razorback sucker for 45 years in Lake Havasu (270,000 total augmentation).
  3. Annually augment the existing population by stocking up to 6,000 subadult razorback sucker for 45 years below Parker Dam (270,000 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 razorback sucker 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 razorback sucker 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 RASU1, the number of razorback sucker stocked could also be reduced if funding provided for stocking razorback sucker is reallocated to support implementation of other conservation measures.

RASU4—Develop additional razorback sucker rearing capacity

The LCR MSCP, in cooperation with AGFD, CDFG, NDOW, USFWS, and other LCR MSCP participants, will develop additional razorback sucker rearing capacity or will acquire the necessary numbers of fish from other sources. Methods to increase rearing capacity to accommodate fish augmentations will include testing the efficacy of raising fish or creating recruiting populations in disconnected backwaters that are predator free. In the context of the integrated landscape mosaic that will provide a variety of habitats and management opportunities (e.g., use of created disconnected backwaters), grow-out facilities will be developed for razorback sucker in the LCR MSCP planning area. Until rearing capacity can be increased sufficiently to produce the numbers of fish required for the augmentation strategy described in conservation measure RASU3, the LCR MSCP will monitor species' response to previous augmentations and will stock the numbers of fish that can be produced up to the amounts described in RASU3. Annual augmentation targets for the first years of the program, therefore, may need to be shifted until later in the program, when increased rearing capacity is at full capacity.

RASU5—Support ongoing razorback conservation efforts at Lake Mohave

Provide support to maintain the current Lake Mohave Program (Native Fish Work Group) goal of maintaining a population of 50,000 adult razorback sucker in Lake Mohave as a genetic refuge.

RASU6—Conduct monitoring and research, and adaptively manage razorback sucker augmentations and created habitat

Monitoring and research will be conducted to gather information necessary to adaptively manage razorback sucker conservation, including continued monitoring of fish response to previous augmentations, aggressive monitoring of fish response following LCR MSCP 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 razorback sucker based on the results of monitoring and research. Monitoring and focused research will be a component of the adaptive management process. In particular, the stocking of 24,000 subadult fish for 5 consecutive years (conservation measure RASU3, submeasure 1) will be conducted as an adaptive management experiment, elements of which will include focusing augmentations in locations that currently support large numbers of fish, 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 3–5. Razorback sucker released into Reaches 2–5 will be marked with wire-coded tags 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 and research 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 LCR MSCP funds allocated for razorback sucker augmentations on those management activities potentially contributing the most to achieving the recovery goals for razorback sucker. As appropriate, the management activities may include changes to the Applicants' proposed augmentation approach, rates, and augmentation sites. The monitoring and research information will also guide maintenance, enhancement, and creation of razorback sucker habitat (e.g., backwaters).

RASU7—Provide funding and support for continuation of the Reclamation/SNWA ongoing Lake Mead razorback sucker studies

The LCR MSCP will continue to fund and support the ongoing studies of razorback suckers in Lake Mead that were implemented under the ISC/SIA BO. The studies are anticipated to be completed within 5–10 years. The focus of the studies will be to resolve any remaining questions about the location of populations of razorback suckers in Lake Mead from the lower Grand Canyon (Separation Canyon) area downstream to Hoover Dam, documenting use and availability of spawning areas at various water elevations, clarifying substrate requirements, monitoring potential nursery areas, continuing ageing studies, and confirming recruitment events that may be tied to physical conditions in the lake. The LCR MSCP and USFWS will agree to the term and further define the scope of the studies. These studies may be followed by further research and monitoring within the adaptive management program of the LCR MSCP.

RASU8—Continue razorback conservation measures identified in the ISC/SIA BO

Reclamation will continue to implement, as part of the LCR MSCP, the following conservation measures identified in the ISC/SIA BO:

  1. Reclamation will continue existing operations on Lake Mohave that benefit native fish during the term of the LCR MSCP and will explore additional ways to provide benefits to native fish.
  2. Reclamation will, to the maximum extent practicable, provide rising spring (February–April) water surface elevations of 5–10 feet on Lake Mead, to the extent hydrologic conditions allow. This operation plan will be pursued through Beach Habitat Building Flows (BHBF) and/or equalization and achieved through the Adaptive Management and Annual Operating Plan processes, as determined for spawning razorback suckers.
  3. Reclamation will monitor water levels of Lake Mead from February to April of each year during the term of the LCR MSCP. The LCR MSCP will evaluate the impacts to razorback spawning at water levels below an elevation of 1,160 feet msl. The ISC/SIA BO includes a conservation measure to collect and rear larval razorbacks in Lake Mead if the lake elevation falls below this level, based on an assumption that razorback spawning would be reduced or eliminated at water elevations below that36 level. It should be noted, however, that the spawning population of razorback sucker found in Echo Bay moved to a lower elevation in 2002 and spawned because the spawning location they had previously used was dry. This change indicates that razorback sucker can successfully move their spawning location into progressively lower elevations as the lake recedes. Given this new information, the LCR MSCP and USFWS will evaluate the data developed in conservation measure RASU6 and determine whether larva collection is appropriate and, if so, at what water elevation it should be implemented.
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).


This gallery includes photos of this species. If you require larger photos, please contact our webmaster Michelle Reilly at mreilly@usbr.gov.