Colorado Pikeminnow

Ptychocheilus lucius

Description

The Colorado pikeminnow, Ptychocheilus lucius, is the largest of the large Cyprinidae (minnow) family, sometimes attaining a length of 5 ft (1.5 m) and a weight of 80 lb (36 kg). It is long and slender, with a pointed snout and flattened head. Adults are dark olive above, whiter below. A voracious predator, it has a large mouth with long, fragile gill arch wells that are designed for grasping prey. This fish is also called the Colorado squawfish.

Behavior

Pikeminnows are predatory feeders. Newly hatched young feed on zooplankton and insect larvae. On reaching 4 in (10 cm), they begin to prey on other fish. A long-lived fish, spawning occurs in females at about 15 years of age during the months of July and August. The pikeminnow is migratory, undertaking long-distance spawning migrations of 250 mi (400 km), round trip; homing behavior has also been noted by researchers. Pikeminnows migrate either upstream or downstream for spawning in late spring, and eggs hatch in less than four days at water temperatures of about 70°F (21°C). Newly hatched larvae drift downstream immediately after hatching, and there is apparently a long-term upstream movement of juveniles that repopulates and maintains the upstream populations of adults.

Habitat

This species has adapted to a watershed known for its variable flow, high silt loads, and turbulence. Adults spend most of their time in eddies, pools, and protected pockets just outside of the main current. Young fish are found in quieter water, usually over silt or sand bottoms.

Distribution

The pikeminnow was once found in the Colorado River basin throughout the mainstream and major tributaries from Arizona to Wyoming. By states, its range included: the Gila River basin in Arizona; the Colorado River from the Mexican border to the Nevada state line in California; the Colorado River and lower reaches of the Gunnison, White, Yampa, Dolores, San Juan, Uncompahgre, and Animas Rivers in Colorado; the San Juan and Animas Rivers in New Mexico; the Colorado River mainstream in Nevada; the entire reach of the Colorado and Green Rivers, and the San Juan, White, and Dolores Rivers in Utah; and the Green River in Wyoming.

Remaining Colorado pikeminnow occur for the most part in the Green River in Utah, and in the Yampa and Colorado Rivers in Colorado and portions of Utah. The first Colorado pikeminnow reported from Wyoming in nearly 30 years was captured, identified, and released unharmed in August 1990 by a zoology professor from Arizona State University. The adult pikeminnow was found in the Little Snake River a few miles north of the Colorado-Wyoming border. Although this report was significant and prompted new sampling in the Wyoming section of the Upper Colorado River basin, biologists were only cautiously optimistic because adult pikeminnows have been known to migrate long distances during spawning periods; one theory was that the fish was a member of an unknown Wyoming population, but it also could have been far upstream from its normal range.

The fish is thought to be absent from the lower Colorado River and rare throughout the remainder of the range. It was probably extirpated from the Gila River basin in Arizona by 1990, but rein-troduction of the species is ongoing. The U. S. Fish and Wildlife Service lists the species as endangered in Arizona, California, Colorado, Utah, and Wyoming.

Threats

The Colorado River was once one of the world's most turbulent rivers. Fish thriving in its turbid and highly mineralized waters were specially adapted to these extreme conditions, and the pikeminnow was plentiful. Many early settlers preferred the "white, flaky, and sweet" flesh of the pikeminnow over any of the native trout.

Since the construction of Hoover Dam in the 1930s and subsequent massive water control projects on the Colorado, water flow has been greatly reduced, radically altering the riverine environment. The decline in pikeminnows has been especially pronounced in areas below reservoirs, which are characterized by extreme water temperature fluctuations, altered flow patterns, lower turbidity, higher salinity, and the presence of introduced fishes, such as the red shiner, redside shiner, and green sunfish.

Conservation and Recovery

As a part of the effort to recover the Colorado pikeminnow, the U. S. Fish and Wildlife Service (FWS) and the Arizona Game and Fish Department began a collaborative project to establish experimental populations in Arizona's Salt and Verde Rivers. In 1985 over 175,000 fingerlings from the Dexter National Fish Hatchery in New Mexico were introduced into those rivers. In 1987, 100,000 more were released.

Also in 1987, the FWS proposed that a third experimental population be established in the main Colorado channel between Imperial Dam and Parker Dam. Under this plan, 100,000 fingerlings would be released the first year, followed by annual restockings over the next 10 years. The FWS hopes to establish a sport fishery for the pike-minnow in the lower Colorado River. A special FWS regulation will allow anglers to take pikeminnows in this stretch of the river, as long as they comply with all other state regulations.

In March 1994, the FWS published the final rule designating critical habitat for the Colorado pikeminnow in portions of the upper basin of the Colorado, Green, Yampa, White, and San Juan Rivers; there is no critical habitat designated in the lower basin. The critical habitat designation will help to focus conservation activities by identifying areas that contain primary constituent elements. In determining which areas to designate as critical habitat for a species, the FWS considers physical and biological attributes that are essential to the Colorado pikeminnow.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

References

Stalnaker, C. B., and P. B. Holden. 1973. "Changes in Native Fish Distribution in the Green River System, Utah-Colorado." Utah Academy Proceedings 50 (1): 25-32.

U. S. Fish and Wildlife Service. 1978. "Colorado Squawfish Recovery Plan." U. S. Fish and Wildlife Service, Denver.

Vanicek, C. D., and R. H. Kramer. 1969. "Life History of the Colorado Squawfish and the Colorado Chub in the Green River in Dinosaur National Monument." Transactions of the American Fisheries Society 98 (2): 193-208.