Razorback sucker (Xyrauchen texanus)

Three to 5 million years ago, a unique-looking fish with a sharp-edged hump “razorback” behind its head swam the Colorado River and its tributaries. The razorback sucker is an endangered, native fish of the Colorado River and the only member of the genus Xyrauchen. It has a dark, brownish-green upper body with a yellow to white-colored belly and an abrupt, bony hump on its back shaped like an upside-down boat keel.

One of the largest suckers in North America, the razorback sucker can grow to 3 feet in length and can live for more than 40 years. Razorback sucker can reproduce at 3 to 4 years of age. Depending on water temperature, spawning can occur as early as November or as late as June. In the Upper Colorado River Basin razorback sucker typically spawn between mid-April and mid-June. Razorback sucker eat insects, plankton, and plant matter on the bottom of the river.

To complete its life cycle, the razorback sucker moves between adult, spawning, and nursery habitats. Spawning occurs during high spring flows when razorback sucker migrate to cobble bars to lay their eggs. Larvae drift from the spawning areas and enter backwaters or floodplain wetlands that provide a nursery environment with quiet, warm, and shallow water.

Research shows that young razorback sucker can remain in floodplain wetlands where they grow to adult size. As they mature, razorback sucker leave the wetlands in search of deep eddies and backwaters where they remain relatively sedentary, staying mostly in quiet water near the shore.

In the spring, razorback sucker return to the spawning bar, often quite a long distance away, to begin the life cycle again.

Status and distribution

  • Listed as endangered and given full protection under the Endangered Species Act in 1991.
  • Endangered under Colorado law since 1979.
  • Protected under Utah law since 1973

Historically, the razorback sucker was widespread and abundant in the Colorado River and its tributaries.

Tom Hastings of Green River, Utah, recalled a trapper with a penchant for razorback suckers.
“There was an old trapper here, well he was here after I come back from World War II,” Hastings said. “He’d catch those suckers and eat them. I don’t know how they fixed them, but they thought they were better than catfish.” (Also see: Historical perspective.)

Today all populations of razorback sucker are supplemented with stocked fish except for the Lake Mead population. Lakes Mead and Mohave are the only population with wild fish.

Working to recover the species

Actions being taken to recover the razorback sucker include:

  • Managing water to provide adequate instream flows to create beneficial water flow
  • Constructing fish passages and screens at major diversion dams to provide endangered fish with access to hundreds of miles of critical habitat
  • Restoring floodplain habitat
  • Monitoring fish population numbers
  • Managing nonnative fishes

In addition, the Recovery Program works to reestablish naturally self-sustaining populations of razorback sucker through propagation and stocking. The Recovery Program maximizes the genetic diversity of wild broodstock used to produce fish in hatcheries to increase the likelihood that stocked fish can cope with local habitats.

In the Upper Colorado River Basin, razorback sucker are raised at two units of the Ouray National Fish Hatchery: the Grand Valley Unit in Grand Junction, Colorado, and the Ouray Unit in Vernal, Utah.

Razorback sucker raised at these facilities are stocked in the Colorado, Green, and Gunnison rivers. Efforts to reestablish populations through stocking demonstrate success as stocked fish survive to sexual maturity and reproduce. Fish stocked in the Colorado and Green rivers have been recaptured in reproductive condition and often in spawning groups. Captures of larvae in the Green and Gunnison rivers document reproduction and their survival through the first year is evidenced by subsequent captures of juveniles.

Stocked fish are moving between the Green, Colorado, and Gunnison rivers. This exchange of individuals between rivers suggests that razorback sucker may eventually form a network of populations or subpopulations.

Recovery goals

Razorback sucker will be considered eligible for downlisting from “endangered” to “threatened” and for removal from Endangered Species Act protection (delisting) when all of the following conditions are met:

  • Self-sustaining fish populations reach the required numbers in areas of the Green River subbasin and EITHER the Colorado River subbasin or San Juan Rivers, and the Lower Colorado River Basin, and a genetic refuge is maintained in Lake Mojave as identified in the chart below.
  • The threat of significant “fragmentation” of the population has been removed. (Fragmentation refers to separation between fish populations caused by geographical distance or physical barriers.)
  • Essential habitats, including primary migration routes and required stream flows are legally protected.
  • Other identifiable threats that could significantly affect the population are removed.

DEMOGRAPHIC CRITERIA FOR RECOVERY
DOWNLISTINGDELISTING
RAZORBACK SUCKER
Over a 5-year monitoring period:
  • Maintain reestablished populations in Green River subbasin and EITHER in upper Colorado River subbasin or in San Juan River, each > 5,800 adults
  • Maintain established genetic refuge* of adults in Lake Mohave
  • Maintain two reestablished populations in lower basin, each > 5,800 adults
For 3 years beyond downlisting:
  • Maintain populations in Green River subbasin and EITHER in upper Colorado River subbasin or in San Juan River, each > 5,800 adults
  • Maintain genetic* refuge of adults in Lake Mohave
  • Maintain two populations in lower basin, each > 5,800 adults
*A “genetic refuge” is group of fish that, as a whole, represent a substantial portion of the genetic variability of the species.