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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Flannelmouth Sucker

       (Catostomus latipinnis)

Adult flannelmouth captured during annual surveys in Reach 3 - Photo by ReclamationYoung adult flannelmouth Sucker captured in Reach 3 - Photo by ReclamationJuvenile flannelmouth captured in a backwater near Laughlin, NV - Photo by Reclamation

General Description

The flannelmouth sucker, Catostomus latipinnis, is the most abundant native sucker in the Colorado River. Individuals can live up to 30 years of age and the largest can reach lengths of 700 mm (about 28 inches). Like most other Catostomids, flannelmouth exhibit distinct, fleshy lips ventrally located on the snout. Flannelmouth sucker are distinguished from other species of the genus by the thickened lower lip that is elongated, compared with other species, and completely divided by the median groove. Flannelmouth sucker are typically dark brownish-green dorsally, yellowish or orange laterally, and white ventrally. Scales located immediately above the lateral line tend to be bordered in dark pigment. Colorations become more prominent during the spawning season, with tubercles becoming highly evident on male fish. It is a river obligate species which is most often found in runs.

Legal Status

Flannelmouth suckers are currently listed as species of special concern in Arizona. They are included in the LCR MSCP due to potential of the species being listed under the ESA or CESA, or becoming protected under Nevada or Arizona law.


Flannelmouth sucker diet composition is described as being omnivorous, with a wide variety of consumption ranging from algae to detritus, including mud and invertebrates. More specifically, specimens from the Virgin River are described as consuming aquatic insect larvae, with portions of inorganic and organic material including quantities of filamentous algae. Seasonal and size-specific shifts in flannelmouth sucker food habits are also documented. For example, flannelmouth sucker <80 mm fed exclusively on copepods, while fish >200 mm did not consume copepods. Overall, the food habits of the flannelmouth sucker are highly dependent upon the availability of food items, with more common items becoming more predominant in diet composition at any given time. This strategy is typical of an omnivorous, opportunistic riverine obligate species.

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.

Updated January 7, 2020

The flannelmouth sucker was historically the most abundant large fish species in the UCRB but the population declined in the LCRB and was thought to be extirpated from the LCRB by the 1970s. For a period, it was largely restricted to the Colorado River above Lake Mead and a short segment of the Salt River. However, in 1976 the Arizona Game and Fish Department stocked 611 adult flannelmouth originating from the Paria River into the mainstem of the LCRB, near Bullhead City, Arizona, just below Davis Dam. Unlike the razorback sucker, flannelmouth seem unable to persist in large impoundments.  However, flannelmouth sucker remain relatively abundant in the UCRB in less-altered sections of river and the most abundant large-bodied fish species in some river sections.

Historically, flannelmouth sucker inhabited virtually all components of riverine habitat ranging from fast current, to riffle, eddy, and stagnant backwater areas. The flannelmouth sucker is described as being an inhabitant of the larger, swifter streams and rivers of the Colorado River Basin.

Flannelmouth sucker are commonly captured in water temperatures ranging from 10 to 35 degrees C. In laboratory test the final thermal preference of flannelmouth sucker was 25.9 degrees C (+/- 0.5 degrees C), but it was noted that flannelmouth have one of the highest temperature tolerances displayed by native fishes of the Colorado River. The upper elevation threshold for flannelmouth sucker inhabitance is 2,192 m based on studies conducted in southwestern Wyoming.

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

Flannelmouth Sucker
FLSU1—Create 85 acres of flannelmouth sucker habitat

Of the 360 acres of LCR MSCP–created backwaters, at least 85 acres will be created in Reach 3 with water depth, vegetation, and substrate characteristics that provide the elements of flannelmouth sucker habitat. Additional habitat could also be provided depending on the extent of connected backwaters that are created for the razorback sucker and bonytail in Reach 3. 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.

FLSU2—Provide funding to support existing flannelmouth sucker conservation programs

The LCR MSCP will provide $80,000 per year for 5 years ($400,000 total) to support flannelmouth sucker research efforts in Reach 3 below Davis Dam to determine habitat use, habitat preferences, and recruitment and to support decisions on habitat management activities for river channel and backwater habitats in Reach 3.

FLSU3—Assess flannelmouth sucker management needs and develop management strategies

The LCR MSCP will use results of research conducted by the LCR MSCP (see conservation measure FLSU2) and others, through the adaptive management process, to assess main channel and backwater management needs and develop management strategies to benefit the flannelmouth sucker.

MRM2—Monitor and adaptively manage created covered and evaluation species habitats

Created species habitats will be managed to maintain their functions as species habitat over the term of the LCR MSCP. Created habitat will be monitored and adaptively managed over time to determine the types and frequency of management activities that may be required to maintain created cottonwood-willow, honey mesquite, marsh, and backwater land cover as habitat for covered species. This conservation measure applies to those species for which comparable measures are not subsumed under species-specific conservation measures (Section 5.7 in the HCP). They are not applicable to species for which habitat would not be created under the LCR MSCP Conservation Plan, such as the desert tortoise, relict leopard frog, humpback chub, and threecorner milkvetch.

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.