Endangered Fish

Looking into an aquarium with fish exhibiting small hump on back
Razorback suckers


The Colorado River and its tributaries make up one of the world’s most colorful river basins. From the high mountains of Wyoming and Colorado, the river drops more than two miles in elevation on its 1,700- mile journey to the Gulf of California. For long stretches, the river is bounded by red canyon walls. Historically, river flows fluctuated widely from season to season and from year to year, reaching peaks of nearly 400,000 cubic feet per second. It took tough, adaptable creatures to survive in this river system.


The Colorado River Basin

The Colorado River basin is composed of the Colorado River and its tributaries. The San Juan, Escalante, Dirty Devil and Paria Rivers all enter the Colorado River within Glen Canyon NRA. They are home to 14 native fish species, four of which are now endangered or threatened. The endangered Colorado pikeminnow, razorback sucker, and bonytail, along with the threatened humpback chub, evolved in the Colorado River basin and exist nowhere else on earth.

Change in Habitat

There are two main contributors to the decline of these four native fish species: water development and the introduction of nonnative fish. Dams, diversions, and other barriers, which provide recreation, flood control, critical water storage, and power generation for the rapidly growing Southwest, also change the dynamics and environment of the river. In many areas, the river is no longer the warm, silt-laden, and sometimes turbulent home these species require. In addition, as the demands of tourism and sport fishing have increased, more than 40 species of nonnative fish, many of which are predatory, have been introduced into the Colorado Basin.

Fish with large humb on its back behind its head
Humpback chub

Arizona Game & Fish Department

Native Fish

Colorado pikeminnow (Ptychocheilus lucius)

  • The largest native minnow in North America, with a torpedo-shaped body and large mouth

  • Young fish eat insects and plankton. Adults feed mostly on other fish

  • Historically reached 6 feet in length, may live over 40 years

  • Once widespread and abundant, today wild populations occur only in rivers above Glen Canyon Dam

  • Migrates up to 590 miles round trip to and from spawning sites in late spring and early summer

  • Hatchery-raised fish are being reintroduced through stocking to re-establish populations in the San Juan River Basin

Razorback sucker (Xyrauchen texanus)

  • A large-river fish with a sharp-edged hump “razorback” behind the head

  • Eat insects, plankton, and plant matter

  • May reach 3 feet (91 cm) in length and live over 40 years

  • Once widespread and abundant, extremely rare today

  • Species dates back 3-5 million years

Bonytail (Gila elegans)

  • A large-river minnow with a streamlined body that is pencil-thin near its tail

  • Eat insects, plankton, and plant matter

  • May reach 22 inches (55 cm) in length and live up to 50 years

  • Once widespread and abundant, extremely rare today

  • Hatchery-raised fish are being introduced through stocking into the Colorado River system above Glen Canyon Dam and into Lake Havasu and Lake Mojave

Humpback chub (Gila cypha)

  • A large-river minnow with an abrupt hump behind the head and large, fan-like fins

  • Eat insects, plankton, and plant matter

  • May reach 20 inches (50 cm) in length and live up to 30 years

  • Six known populations, each ranging from a few hundred to a few thousand fish

  • Found primarily in canyon sections of the Colorado River Basin, including the Grand Canyon


Fish recovery in Glen Canyon National Recreation Area

Throughout the Colorado River Basin, partnerships of local, state, and federal groups are working to conserve and recover endangered and threatened fishes.

Steps underway to re-establish these fish species

  • The National Park Service works with the Bureau of Reclamation, the U.S. Fish & Wildlife Service, and many other partners to help educate the public about the need to save these historic native fish.

  • The Utah Department of Natural Resources operates a hatchery at Big Water, UT, raising some of these endangered species to be restocked in suitable habitat along the river.

  • The Bureau of Reclamation, as part of the Adaptive Management Program, monitors and controls releases from Glen Canyon Dam in order to reduce the impacts of these releases on plant and animal species below the dam.

  • Biologists from many agencies continue to study and monitor these endangered species so we may learn more about them and help ensure their survival.

Although they are rare, due to monumental efforts upriver by a host of agencies and interest groups, Colorado pikeminnow, razorback sucker, bonytail, and humpback chub can occasionally be caught in the upper reaches of Lake Powell near the inflows of the Colorado and San Juan Rivers. Please carefully handle and quickly return these fish to the water if you chance to catch one.


For more information about the Upper Colorado Endangered Fish Recovery Program, visit their website at www.ColoradoRiverRecovery.org

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    Last updated: March 14, 2023

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    Contact Info

    Mailing Address:

    PO Box 1507
    Page, AZ 86040


    928 608-6200
    Receptionist available at Glen Canyon Headquarters from 7 am to 4 pm MST, Monday through Friday. The phone is not monitored when the building is closed. If you are having an emergency, call 911 or hail National Park Service on Marine Band 16.

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