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The Colorado Pikeminnow and the Razorback Sucker

Colorado Pikeminnow

The Colorado pikeminnow, formerly the Colorado squawfish, is the largest American minnow (up to 6 feet long and 80 pounds in size). It is an elongated pike-like fish with a dusky-greenish, slender body with gold flecks on the dorsal (upper) surface. Its head is long and slender with a large mouth and thickened lips and jaws that lack teeth. Pharyngeal teeth are located on its gills in the back of its throat to grasp and hold prey. It is the top native carnivore of the Colorado River system and a voracious predator. Its substantial size and migratory habits resulted in the use of common names such as "white salmon," and "Colorado salmon." It was listed as endangered by the U.S. Fish and Wildlife Service on March 11, 1967 (32 FR 4001).

  • The fish occurs in the warm, swift waters of the big rivers of the Colorado Basin. Adults are migratory and inhabit pools and eddies just outside the main current. Young can be found in backwater areas. Historically, the fish was found in the Colorado River and major tributaries in Arizona, New Mexico, Utah, Colorado, and Wyoming. Fossil evidence indicates that it may have used lakes as well as rivers. Populations also exist in the Colorado, Green, Yampa, Gunnison, and San Juan Rivers, tributaries of the Colorado River. Experimental, nonessential populations of Colorado pikeminnow have been introduced in the Verde and Salt River basins in Arizona (50 CFR Part 17.84b).

Colorado pikeminnow are adapted to rivers with seasonally variable flow, high silt loads, and turbulence. Young-of-the-year and juvenile Colorado pikeminnow live in shallow backwater areas, with little or no current over silt and sand bottoms. When they are about 8 inches in length, habitat preferences change with fish seeking deeper water with some velocity. Colorado pikeminnow can tolerate a broad range of temperatures from 35 degrees C in the summer to lower than 10 degrees C in winter. Food for young pikeminnow is mainly made up of zooplankton and insect larvae. The young become predatory at about 4 inches. Nearly 86 percent of the diet for juveniles is other fish.

Historically, the Colorado pikeminnow was an important food for human residents. American Indians caught them. In 1871, the Powell expedition reported capturing Colorado pikeminnow. In 1891, it was identified as the largest and best food fish on the lower Colorado River. The species was widely sought by anglers prior to its decline.

Stream alteration and habitat fragmentation caused by dam construction, irrigation dewatering, channelization, and the introduction of competitive and predatory nonnative fishes have led to a decline in the population. Other factors include changes in stream nutrients and lowered turbulence. Nutrients that once occurred in rivers are confined to reservoirs. Channelization below dams has reduced the number and size of backwaters and sloughs sought after by the Colorado pikeminnow and other native fishes for nursery and resting areas. The natural cycle of flood and drought has been replaced by stable discharges and water levels.

Razorback Sucker

The razorback sucker has a long, high, sharp-edged hump, or keel, behind the head from which its name is derived. The head and body are dark, especially on breeding males, and the sides brownish fading to a yellowish white abdomen. The dorsal fin is dark, the anal fins yellowish, and the caudal fins yellowish brown. The razorback sucker grows to a large size, reaching lengths of 36 to 39 inches and weights up to 12 pounds. It was listed as endangered by the U.S. Fish and Wildlife Service on October 23, 1991 (56 FR 54957).

The razorback sucker occurred in medium to large rivers with swift turbulent waters, as well as slow backwater areas where it feeds on benthic fauna and flora, detritus, and plankton. The razorback sucker historically was found throughout the Colorado River Basin of Wyoming, Colorado, Utah, Nevada, Arizona, and New Mexico. Most wild fish are now found in Lake Mohave, which represents the largest population within the lower basin. A few adults have also been found in Lake Mead and Lake Havasu. In the upper basin, they can be found in unimpounded waters of the Green, Yampa, and mainstem of the Colorado. Although adults reproduce in reservoirs, young do not survive due to a lack of suitable food items and predation by nonnative fishes.

This species has declined due to habitat alterations, primarily impoundments and competition with predation by nonnative fishes.


This webpage was last modified on: February 19, 2014

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