The Razorback Sucker: Back from the Brink

by Debbie Felker, Julie McIntyre, Tom Burke, and Tom Czapla

As far back as 3 to 5 million years ago, a unique-looking fish with an abrupt, sharp-edged hump behind its head swam the Colorado River and its tributaries. Once widespread and abundant, the razorback sucker (Xyrauchen texanus) is now extremely rare in the wild.

The razorback sucker is a large-river fish found only in the Colorado River Basin. Since the early 1900s, the widespread installation of dams, removal of water for human use, and introduction of non-native sport fish have significantly altered the character of the Colorado River. These changes contributed to the decline of the razorback sucker and three other fish species that exist nowhere else on earth: the humpback chub (Gila cypha), bonytail (Gila elegans), and Colorado pikeminnow (Ptychocheilus lucius).

Valued as food by Native Americans, early settlers, and miners, razorback suckers can live for over 40 years and grow to over 3 feet (0.9 meter) in length. Adults can reproduce at 3 to 4 years of age. Playing an important ecological role, razorback suckers eat insects (including fly and mosquito larvae), plankton, and decomposing plant matter on the bottom of the river.

Life history

The razorback sucker evolved in warm-water reaches of larger rivers of the Colorado River Basin from Wyoming to Mexico. These fish move around among adult, spawning, and nursery habitats to complete their life cycle. Spawning occurs during high spring flows when razorback suckers migrate to gravel 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 suckers can remain in floodplain wetlands where they grow to adult size. As they mature, razorback suckers leave the wetlands in search of deep eddies and backwaters where they remain relatively sedentary, staying mostly in quiet water near shore. In the spring, razorback suckers return to the spawning bar, often quite a long distance away, to begin the life cycle again.

Range and Habitat

The Colorado River Basin is divided into upper and lower basins at Lee’s Ferry, Arizona. The Upper Colorado River and San Juan River Basin Endangered Fish recovery programs span rivers in Colorado, Utah, Wyoming, and New Mexico, including Lake Powell. The Lower Colorado River Basin overlaps with Arizona, Nevada, and California, and includes Lake Mohave, Lake Mead, and Lake Havasu. The Lower Colorado River Basin is managed primarily by the Lower Colorado River Multi-Species Conservation Program and the Lake Mohave Native Fish Work Group.

Fish habitats throughout the Colorado River Basin are extremely varied, ranging from high mountain streams to red rock canyon walls in northern areas and to large reservoirs and warm, turbid, swift-flowing reaches with shifting sand and marshy borders in southern portions. Throughout the Colorado River Basin, partnerships of local, state, and federal agencies, American Indian tribes, water and power interests, and environmental groups are working to conserve and recover the endangered fishes. This major undertaking involves restoring and managing stream flows and habitat, boosting wild populations with hatcheryraised native fish, and reducing negative interactions with certain non-native fish species. The goal is to achieve natural, self-sustaining wild populations that no longer require protection by the Endangered Species Act.

Management and Recovery Actions

Managing water to provide adequate instream flows. Water resources are managed in accordance with state water laws, individual water rights, and interstate compacts. Within these frameworks, recovery actions include water leases and contracts, coordinated water releases from upstream reservoirs, efficiency improvements to irrigation systems, and reoperation of federal dams and reservoirs to provide flow and temperature regimes designed to benefit all four endangered fishes.

Construction projects. Fish passages at low-level diversion dams and fish screens to keep fish from becoming trapped in irrigation canals have been built at nearly all major diversion dams on the Upper Colorado, Gunnison, and San Juan rivers. The recovery programs are working to complete the remaining fish screens needed in the Upper Colorado River and San Juan River basins. During 2007, the Service also constructed six ponds on the Imperial National Wildlife Refuge about 50 river miles (80 kilometers) above Yuma, Arizona. The ponds, which total about 80 surface acres (32 hectares), are being stocked with razorback suckers and bonytail, and will be managed as native fish refugia.

Propagation and stocking. Ten hatchery facilities and multiple riverside ponds produce the fish used to stock wild razorback sucker populations. Since 1996, about 197,100 subadult razorback suckers have been stocked in the Upper Colorado River system, and since 1994, about 52,700 subadult or adult razorback suckers have been stocked in the San Juan River. From 1997 to the present, about 90,000 razorback suckers have been released into the Colorado River below Parker Dam, with 20,012 razorback suckers stocked throughout the Lower Colorado Basin in 2007 alone.

The stocking efforts are showing success:

• Stocked razorback suckers are moving among the Green, Colorado, and Gunnison rivers, suggesting that razorback suckers may eventually form a network of populations or subpopulations.
• Stocked razorback suckers are behaving as wild fish. They have been recaptured or observed in reproductive condition at spawning sites in the Green, Colorado, and San Juan rivers and, based on captures of larval fish, are reproducing in the wild in the Green, Gunnison, Colorado, and San Juan rivers.
• Razorback sucker larvae are surviving through the first year in the Green, Gunnison, and San Juan rivers, based on captures of juveniles. Numbers of larvae collected from the Green River in 2007 were the highest ever recorded.
• Along the Colorado River downstream of the Grand Canyon, Lake Mead is one of the most unique habitats in the entire Colorado River Basin because it has a self-sustaining population of razorback suckers. Over the last 12 years, Lake Mead has supported a population of 250 to 500 adults, with sustained recruitment for at least 30 years.
• South of Lake Mead is Lake Mohave, which contains the most genetically diverse adult populations of razorback suckers. There had been a very large population in the reservoir shortly after impoundment, but these fish were not recruiting and were projected to die-off due to old age around the turn of the century. Today, the old wild population is estimated to number fewer than 50 fish, but there now are roughly 1,500 repatriated adults on the spawning grounds providing thousands of larvae annually for rearing and stocking throughout the lower basin.
• Approximately 1,500 adult razorback suckers congregate in the river near Needles, California, to spawn. In 2008, razorback suckers stocked in the Colorado River at Laughlin, Nevada (30 miles, or 48 km, upstream of Needles), and in the Bill Williams River, Arizona (50 miles, 80 km, downstream of Needles), were found in the Colorado at the Needles spawning bar within 10 days of release.

Addressing non-native fish management challenges. Over the past 100 years, more than 70 non-native fish species have been introduced into the Colorado River Basin. We now know that predation and competition by these non-natives are serious threats to the listed native species. For example, research has found non-native fish prey upon razorback sucker eggs and juveniles up to 12 inches (30 centimeters) in length. The recovery programs are removing the most problematic non-native fishes from the rivers and preventing others from entering the river system in areas inhabited by endangered fish. These actions recognize the dual responsibilities of state and federal wildlife agencies to conserve native fish species while providing sportfishing opportunities.

Research and monitoring. The recovery programs monitor reproduction, growth, survival, and abundance of endangered fish in the wild. Studies of the roles of predators (birds and nonnative fish), improving physical conditioning of fish prior to stocking, maintaining genetic quality, and age structure continue. The results are used to track progress and adjust recovery efforts as needed through adaptive management.

Reaching out to local communities. Enhancing public awareness and support for endangered fish recovery is important to achieving success. Among our innovative educational programs are interpretive exhibits at visitor centers, annual water festivals, outreach at conferences, providing endangered fish for aquariums in local classrooms, and student tours of fish passage facilities.

Debbie Felker, information and education coordinator, and Tom Czapla, propagation coordinator, Upper Colorado River Endangered Fish Recovery Program, can be reached at debbie_felker@fws.gov or 303-969-7322, ext.227, and tom_czapla@fws.gov or 303-969-7322, ext. 228. Julie McIntyre, a fish and wildlife biologist in the Service’s Southwest Regional Office, can be reached at julie_mcintyre@fws.gov or 505-248-6507. Tom Burke, a fish and wildlife biologist with the Bureau of Reclamation, can be reached at the address and number below.

Programs Working to Recover the Razorback Sucker

• Upper Colorado River Endangered Fish Recovery Program
  Established in 1988. Working to recover humpback chub, bonytail, Colorado pikeminnow, and razorback sucker in the Colorado River and its tributaries in Colorado, Utah, and Wyoming.
  P.O. Box 25486, DFC
  Denver, CO 80225
  303-969-7322
  coloradoriverrecovery.fws.gov
• San Juan River Basin Recovery Implementation Program
  Established in 1992. Working to recover Colorado pikeminnow and razorback sucker in the San Juan River and its tributaries in Colorado, New Mexico, and Utah.
  2105 Osuna Road NE
  Albuquerque, NM 87113
  505-761-4745
  southwest.fws.gov/sjrip
• Lower Colorado River Multi-Species Conservation Program
  Finalized in 2005. Working with over 50 entities to restore habitat and address the needs of listed species in the Lower Colorado River. As a 50-year conservation project covering 26 aquatic and terrestrial species, this program represents the largest, longest-term federal/state partnership plan in the United States.
  Program Office: 702-293-8577
  http://www.lcrmscp.gov/
• Native Fish Work Group
  Established in 1991. A seven-agency team, spearheaded by the U.S. Bureau of Reclamation, to replenish Lake Mohave’s older razorback sucker population with young adults.
  Tom Burke
  U.S. Bureau of Reclamation
  Boulder City, Nevada
  702-293-8310