Listing
Apr 24, 1978
Apr 24, 1978 Listing (Threatened)
Proposed Endangered Status for the Bonytail Chub and Threatened Status for the Razorback Sucker
- Publication type: Proposed
Item 1
FWS Focus
Overview
Characteristics
Overview
The razorback sucker is native only to the warm-water portions of the Colorado River basin of the southwestern United States. Razorback sucker are found throughout the basin in both lake and river habitats but are most common in backwaters, floodplains, flatwater river sections and reservoirs.
Dam construction in the basin reduced peak flows, changed temperature regimes, created reservoirs, and disconnected floodplains from the mainstem rivers. Altered environments provided opportunities for nonnative fish to flourish. Nonnative predators eat early life stages of razorback sucker, preventing reproduction in the river systems. In response to population declines, stocking programs were developed and implemented throughout the Colorado River basin.
The razorback sucker was listed as an endangered species in 1991. Because of conservation efforts and reestablishment of populations that are surviving, spawning, and showing rare signs of reproductive success, the species was proposed for reclassification in 2021. Survival of wild razorback sucker to the adult life stage still needs to occur on a broad scale to effectively complete the lifecycle of the species.
Scientific Name
Xyrauchen texanus
Common Name
Razorback Sucker
FWS Category
Fishes
Identification Numbers
Characteristics
Characteristic category
Habitat
Characteristics
Habitat
Razorback sucker are native only to large rivers in the Colorado River basin. They use a variety of habitat types, including mainstem river channels, reservoirs, turbid inflow areas, and floodplain wetlands. Historically, razorback sucker are thought to have been uncommon in turbulent, canyon-bound river sections, with robust populations typically found in calm, flatwater areas.
Characteristic category
Food
Characteristics
Food
Razorback sucker eat insects, plankton, and plant matter on the river bottom.
Characteristic category
Behavior
Characteristics
Behavior
Razorback spend most of their lives in deep water, but they move into the shallows for breeding. In the shallows, males stake out a breeding territory and hover near the riverbed. Razorback sucker males have been observed rolling their eyes, generating flashes of reflected sunlight. This behavior is believed to be territorial and intended to deter an intruder swimming above.
Characteristic category
Physical Characteristics
Characteristics
Size & Shape
One of the largest suckers in North America, the razorback sucker can grow to more than three feet (one meter) in length, though most are smaller. The razorback sucker is distinguished by its unique, bony, razor-like keel that rises abruptly behind the head. The keel is likely adapted to help the species swim in strong river currents.
Weight
Adult razorback sucker may weigh 10 pounds (five-to-six kilograms).
Color & Pattern
The species is olive in color, with darker brownish-black coloring above and lighter (often yellow) colors below.
Characteristic category
Life Cycle
Characteristics
Life Cycle
Razorback sucker can reproduce at three-to-four years of age. To complete its life cycle, the razorback sucker moves between adult, spawning, and nursery habitats.
Larvae drift from the spawning areas and enter backwaters or floodplain wetlands that provide a nursery environment with quiet, warm, and shallow water. Following the spawn, adults return to deeper environments.
Research shows that young razorback sucker can remain in floodplain wetlands, where they grow to adult size. As they continue to mature, they leave the wetlands in search of deep eddies and backwaters, where they are 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.
Life Span
Razorback sucker can live for more than 40 years.
Reproduction
Spawning typically occurs during high spring flows, when razorback sucker migrate to cobble bars to lay their eggs. Depending on water temperature, however, spawning can occur as early as November or as late as June.
Characteristic category
Similar Species
Characteristics
Similar Species
The razorback sucker is a catostomid, generally related to other sucker species. It is the only member of the Xyrauchen (razorback suckers) genus.
Geography
Characteristics
Range
The historical range of the species includes most of the Colorado River basin, from Wyoming to the delta in Mexico, including the states of Colorado, Utah, New Mexico, Arizona, Nevada, and California, and Mexican states of Baja and Sonora.
The species is now found in both the upper and lower Colorado River basins. The largest population has been re-established with stocked fish in the Green River basin and its tributaries in Utah and Colorado. Additional populations reside in the Colorado and San Juan rivers above Lake Powell. There are multiple populations separated by dams in the lower Colorado River, including in Lake Mead, Lake Mohave, and Lake Havasu. Substantial populations are not known to exist in the Gila basin.
Timeline
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