Northern Prairie Wildlife Research Center
Colorado Squawfish(Ptychocheilus lucius)— Endangered
Humpback Chub (Gila cypha)—Endangered
Bonytail Chub (Gila elegans)—Endangered
Razorback Sucker (Xyrauchen texanus)— Endangered
Captive populations of Colorado squawfish, bonytail chub, and razorback sucker are maintained at the Dexter National Fish Hatchery and Technology Center. In the wild, Colorado squawfish occur in the Salt and Verde Rivers; both populations are small and designated as nonessential experimental populations. Humpback chub occur in the Little Colorado River and Colorado River mainstem upstream and downstream from the mouth of the Little Colorado River. The bonytail chub population is confined to Lake Mohave, and bonytails continue to be stocked there. Fish surveys conducted annually during late winter and early spring consistently yield a few bonytail chubs; the population is believed to be small, but continues to survive. Most of the "Arizona" razorback sucker population, some 60,000 fish, reside in Lake Mohave. These fish are more than 40 years old; as a result, the population could crash at any time. Several factors threaten all four species, including destruction of floodplain habitat, reduction of spring flows, alteration of natural hydrography, flow fluctuations for hydropower production, fish passage barriers, cold water temperatures below mainstem reservoirs, competition with and predation by nonnative fishes, and contaminants.
Implementation of a spawning and rearing program at Lake Mohave shows promise. In the spring of 1992, 90 adult razorback suckers were moved to a "predator free" pond on the banks of Lake Mohave. These fish were allowed to spawn naturally and the progeny survived on food that occurred naturally in the pond. By the end of the summer, 300 young razorbacks had been tagged and either placed into a protected cover for further growth or released directly into Lake Mohave. The facilities in the cove have now been expanded to include bonytail chub. Both species will be released into Lake Mohave soon after they reach 300 millimeters total length. Because recruitment is either very low or non-existent for these two species, the introduction of subadult fish is deemed necessary to maintain the existing population until steps can be taken to ensure that recruitment occurs naturally.
The multi-agency Glen Canyon Environmental Studies are evaluating impacts of Glen Canyon Dam operations on the environment of the Colorado River downstream of the dam, including impacts on endangered fishes. Additionally, the Native Fish Work Group was established as an advisory group for endangered fishes. The only significant section 7 consultations involve the proposed stocking of sport fishes (one is a Fish and Wildlife Service program and the other is a State program), which would use fish supplied by the Service. Biological evaluations of both proposals are under way.
Because of the many threats to these species, a variety of measures will be needed for their recovery, including extensive habitat restoration, control of nonnative fishes, improvements in water quality, and reintroductions of the native fishes to their historic habitats.
In FY 1991, Arizona received $64,000 for stocking and monitoring razorback suckers and Colorado squawfish, and $10,000 for monitoring humpback chubs. In FY 1992, Arizona received $39,000 for monitoring squawfish and razorbacks.
Two programs are being conducted to recover the river's endangered fishes in Arizona, the Glen Canyon Environmental Studies and the Native Fish Work Group:
Glen Canyon Environmental Studies: This program is being conducted to identify the impacts of Glen Canyon Dam operations on the environmental and recreational resources of the Colorado River downstream of the dam, including impacts on endangered Colorado River fishes. Federal agencies participating include the Fish and Wildlife Service, Bureau of Reclamation, Bureau of Indian Affairs, U.S. Geological Survey, National Park Service, and Western Area Power Administration. The Arizona Game and Fish Department is also participating, as are Arizona State University and various private consultants.
Native Fish Work Group: This group recommends studies and activities believed necessary to recover fishes of the lower Colorado River basin and participates to an extent in their implementation. Federal involvement in this program includes the Fish and Wildlife Bureau of Reclamation, and National Park Service. The Arizona Game and Fish Department and the Nevada Department of Wildlife Conservation also participate, along with Arizona State University and the University of Arizona.
Colorado squawfish—original plan approved 3/16/78; revised 8/6/91.
Humpback chub—original plan approved 8/22/79; revised 9/19/90.
Bonytail chub—original plan approved 5/16/84; revised 9/4/90.
Razorback sucker—plan under development.