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The Endangered Fish of the Colorado River Basin

January 01, 2009
by John Weisheit

Razorback sucker drawing by Gloria Brown
Razorback sucker drawing by Gloria Brown

By improving the quality of life for wild creatures, we improve the quality of life for people. This is the intent of the Endangered Species Act (ESA). It is a legislative act of hope to preserve our heritage and a marker that society has a responsibility toward community and stewardship.

Aldo Leopold recognized in 1949 what the distraction is against the preservation ethic, "the land-relation is still strictly economic, entailing privileges but not the obligations."

President Eisenhower might have said it best, "A people that values its privileges above its principles soon loses both."

Since Congress passed the ESA in 1973, recovery programs on the Colorado River have yet to stabilize a single imperiled species. Because there is no honest enforcement from federal and state agencies, the ESA has become a legislative embarrassment to the nation and lawsuits abound.

The Department of Interior currently boasts that the endangered humpback chub population in Grand Canyon is improving under their tuteluge, but fails to mention that the razorback sucker and other species were simultaneously lost.

The dialogue of the privileged to reform the ESA is more about their greed, inconvenience, and zookeeping remedies. The hope is turning into despair.

Besides throwing blame on the government, we need to look at the whole of society, as Leopold observed. Specifically our acute consumption of natural resources to fuel the growth economy theory, which is impossible to sustain in perpetuity despite the cheerleading.

Achieving a steady-state population and economy for humans is indeed desirable, if not absolutely essential to reverse the struggle toward extinction, because it otherwise mirrors the inclusion of the human race.

Our society must face the fact that for too long, we have consumed too much, and this carelessness does not offer a final reward.

Read: Prosperity without growth.

The native fish of the Colorado River

The native fish populations in the southwestern United States have the highest rate of jeopardy toward extinction in the nation.

If not for the undeveloped tributary streams of the Colorado River basin, where natural habitat still exists, these fish would have become extinct long ago. 2001 - Tyus and Saunders.

Click here to watch a movie clip of native fish (either humpback chub or bluehead sucker) spawning at the mouth of Havasu Creek, a spring-fed tributary of the Colorado River in Grand Canyon National Park.

Historically, the native fish fauna of the Colorado River Basin was dominated by the minnow (cyprinids) and sucker (catostomids) families. Of the 34 known native species to the Colorado River basin, 74% are found nowhere else in the world, or endemic.

Threats to these species include streamflow regulation and habitat modification (dams and diversions), altered food web, predation (eaten as prey) by nonnative fish species, parasitism (Asian tapeworm), hybridization with other native fish species, and pesticides, toxins and pollutants. These changes to the river environment have occurred so quickly that the species have been unable to a adapt, so pro-active human intervention is the only hope they have. Since the river is truncated by 83 dams in the upper basin and 10 dams in the lower basin (reference), this loss of genetic diversity will also impede their recovery.

Fish ladders have been constructed at small diversion dams in the upper basin river reaches, which increase the range of habitat for a few dozen miles. Fish ladders at high dams, such as Glen Canyon and Hoover dams, are probably impossible to construct. Whereas removing Glen Canyon Dam, which is not essential water infrastructure, would increase river habitat by 500 miles on the Colorado, San Juan, and all the convergent tributaries of Canyon Country.

Glen Canyon Dam exists solely for reasons of delaying the downstream movement of water at a fixed geographical location (Lee's Ferry, Arizona), a function that Hoover Dam is able to perform. Also, of course, to provide hydropower revenue (a federal subsidy) to pay for the dams and water projects of the basin, a function that farmers and cities are able to perform.

In other words, bureaucratic bean counting is essentially why these fish suffer.

The four species of greatest concern

  1. Colorado squawfish (Ptychocheilus lucius) (photo)
  2. humpback chub (Gila cypha) (photo) (close-up)
  3. bonytail chub (Gila elegans)  (photo)
  4. razorback sucker (Xyrauchen texanus) (photo)

Photos for identification

  1. Bluehead sucker
  2. Flannelmouth sucker
  3. Colorado Pikeminnow
  4. Razorback sucker
  5. Rondtail chub

Listing in the Federal Register

  1. Colorado squawfish - March 11, 1967 (32 FR 4001)
  2. humpback chub - March 11, 1967 (32 FR 4001)
  3. bonytail chub - April 23, 1980 (45 FR 27713)
  4. razorback sucker - October 23, 1991 (56 FR 54957)

River sections of extirpation

Extirpation means a self-reproducing plant or animal species has become locally extinct (definition). Protection under the ESA includes preserving critical habitat and implementing recovery programs to reverse the trend toward extinction.

  1. Above Lake Powell, all endangered species are present, but populations have yet to be stabilized sufficient enough for delisting, especially the bonytail chub and razorback sucker.
  2. In the Grand Canyon, three of the four endangered fish (Colorado pikeminnow, bonytail chub, razorback sucker) are extirpated. Additionally, a threatened species, the roundtail chub, is extirpated in the Grand Canyon.
  3. Below Hoover Dam all endangered fish are extirpated, but hatchery-born fish have been introduced in various river sections and reservoirs, such as Lake Mohave. The natural breeding and rearing of endangered fish in the lower reaches of the Colorado River have not been successful, so far.

Designated critical habitats

  1. Green River from Gates of Lodore (Dinosaur National Monument) to the Colorado River confluence, Colorado and Utah.
  2. Yampa River in Dinosaur National Monument, Colorado.
  3. White River from Rio Blanco Lake Dam to the Green River confluence, Colorado and Utah.
  4. Duchesne River from river mile 2.5 to Green River Confluence, Utah.
  5. Colorado River from Colorado River Bridge (I-70, exit 90 in Rifle) to North Wash (Lake Powell), Colorado and Utah.
  6. Gunnison River from the confluence of the Uncompahgre River to the Colorado River confluence, Colorado.
  7. San Juan River from State Route 371 Bridge (Farmington) to Neskahai Canyon (Lake Powell), New Mexico, Colorado and Utah.
  8. Colorado River from confluence of Paria River to Imperial Dam, Arizona, Nevada and California.
  9. Little Colorado River from river mile 8 to Colorado River confluence.
  10. Gila River from New Mexico border to Coolidge Dam, Arizona.
  11. Salt River from Highway 60 Bridge to Roosevelt Diversion Dam.
  12. Verde River from boundary of Prescott National Forest to Horseshoe Dam.

Note: Includes 100-year river floodplain and full pool elevation of reservoirs. Lake Powell is not critical habitat except for the uppermost arms of San Juan and Colorado rivers. Total river mileage is 1,980.

Minimum streamflow requirements

Flow Recomendation web page

Recovery plans (currently being revised by US Fish and Wildlife Service)

  1. Colorado pikeminnow
  2. humpback chub
  3. bonytail chub
  4. razorback sucker


Upper Colorado River

Lower Colorado River

Gila River Basin

Five-year Reviews

Recovery and adaptive management programs

  1. Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin
  2. San Juan River Basin Recovery Implementation Program
  3. Glen Canyon Dam Adaptive Management Program
  4. Lower Colorado Multiple-Species Conservation Program

2001 - Comments on the recovery goals for endangered fish. Coggins and Gloss; GCMRC.

Program action plans

  1. Upper Colorado River. April, 2007.
  2. San Juan River. August 2006
  3. Glen Canyon Dam. August, 2001
  4. Lower Colorado. June, 2004.


Colorado pikeminnow description

  1. Average total length (TL) - 1.8 m (71 inches)
  2. Average weight - 36 kg (79 lbs)
  3. Average lifespan - 40+ years
  4. River temperature to spawn - 18 and 23°C (64 -73° F)
  5. Adult populations - Green River, 6,000-8,000; upper Colorado River, 600-900; San Juan River, 19-50.

The Colorado pikeminnow is a long-distance migrator and historically ranged from Wyoming to Mexico; moving hundreds of miles to and from spawning areas. Adults require pools, deep runs, and eddy habitats maintained by high spring flows. These high spring flows maintain channel and habitat diversity, flush sediments from spawning areas, rejuvenate food production, form gravel and cobble deposits used for spawning, and rejuvenate backwater nursery habitats. Spawning occurs after spring runoff when the temperature reaches 64 -73° F. After hatching and emerging from spawning substrate, larvae drift downstream to nursery backwaters that are restructured by high spring flows and maintained by relatively stable base flows (non-fluctuating).

Humpback chub description

  1. Average total length (TL) - 480 mm (19 inches)
  2. Average weight - 1.2 kg (2.6 lbs)
  3. Average lifespan - 20 to 30 years
  4. River temperature to spawn - 16 and 22°C (61-72° F)
  5. Adult populations - Black Rocks, Colorado River in Colorado, 900-1,500; Westwater Canyon, Colorado River in Utah, 2,000-5,000; Yampa Canyon, Yampa River in  Colorado, 400-600; Desolation/Gray Canyons, Green River in Utah, 1,500; Cataract Canyon, Colorado River in Utah, 500; Grand Canyon and Little Colorado River in Arizona, 2,000-4,700.

Historically ranged from below present-day Hoover Dam in the Colorado River upstream into Colorado, and in the larger portions of Colorado River tributaries in Arizona, Utah, Colorado, and Wyoming. The humpback chub is restricted to deep, swift, canyon-bound regions of the mainstem and large tributaries of the Colorado River. This specialized habitat, as it were, is probably why the species was unknown to the world until 1946. Adults require eddies and sheltered shoreline habitats maintained by high spring flows for spawning. High spring flows maintain channel and habitat diversity, flush sediments from spawning areas, rejuvenate food production, and form gravel and cobble deposits used for spawning. Eggs are dispersed when the water temperature reaches 61-72° F. The young require low-velocity shoreline habitats, including eddies and backwaters, that are more prevalent under base-flow (non-fluctuating) conditions.  

Bonytail chub description

  • Average total length (TL) - 550 mm (22 inches)
  • Average weight - 1.2 kg (2.4 lbs)
  • Average lifespan - 40+ years
  • River temperature to spawn - unknown; probably same as humpback.
  • Adult populations - Currently no self-sustaining populations of bonytail exist in the wild and recovery is dependent on the success of brood stock from hatcheries. Click here to see photo by Robin Silver of the last wild bonytail captured in Lake Mohave by Paul Marsh.

Razorback sucker description

  1. Average total length (TL) - 1m (39 inches)
  2. Average weight - 5-6 kg (11-13 lbs)
  3. Average lifespan - 40+ years
  4. River temperature to spawn - >14°C  (>57°F)
  5. Adult populations - Middle Green River in Utah, 100; scant population in Colorado River, Colorado; scant population in San Juan River, Utah. Recovery of this fish, like the bonytail chub, is dependent on brood stock from hatcheries. In the Grand Canyon, razorback sucker has not been captured since the early 1990s; a hybridized razorback was observed in the Grand Canyon at the mouth of Kanab Creek, May 2008. It is generally assumed the razorback requires floodplain habitat to spawn. Floodplain inundation has not occurred on the Colorado river basin since 1984.

Historically, razorback sucker were widely distributed in warm-water reaches of larger rivers of the Colorado River Basin from Mexico to Wyoming. Habitats required by adults in rivers include deep runs, eddies, backwaters, and flooded off-channel environments in spring; runs and pools often in shallow water associated with submerged sandbars in summer; and low-velocity runs, pools, and eddies in winter. Spring migrations of adult razorback sucker were associated with spawning in historic accounts, and a variety of local and long-distance movements and habitat-use patterns have been documented. Spawning in rivers occurs over bars of cobble, gravel, and sand substrates during spring runoff at widely ranging flows and water temperatures (typically greater than 57°F). Spawning also occurs in reservoirs over rocky shoals and shorelines. Young require nursery environments with quiet, warm, shallow water such as tributary mouths, backwaters, or inundated floodplain habitats in rivers, and coves or shorelines in reservoirs.

Additional reading



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