Colorado pikeminnow is a fish species endemic to warm-water, large rivers of the Colorado River basin and is the largest minnow native to North America. Historically, the Colorado pikeminnow was the apex, or top, predator in the upper basin, despite lacking jaw teeth. The species was protected under the Endangered Species Act in 1973 because large dams and human water use altered river flows and restricted the fish’s movement. Populations of Colorado pikeminnow in the Colorado and Green rivers are remnants of wild populations. The species has also been reintroduced into the San Juan River through the stocking of hatchery fish.
Colorado pikeminnow inhabit larger rivers in the Colorado River basin and occupy a variety of environments that change over the course of their life cycle. Larvae and juveniles are found in calm, warm backwaters and other low-velocity areas. As they grow, larger juveniles and adults establish home ranges that contain pools, deep runs, and eddies where they can forage. While Colorado pikeminnow can migrate long distances (more than 200 miles) to find suitable spawning bars comprised of loose, clean cobbles and gravel, they may spawn closer to their home range if suitable sites are nearby.
A natural body of running water.
Colorado pikeminnow adults primarily eat other fish; they are adapted to consume native species that lack spines in their fins. Now that nonnative fish are common in the system, adult pikeminnow have been captured with catfish lodged in their mouths, due to prey’s spines. Juveniles feed on aquatic insects and gradually transition to eating more fish as they grow.
Adult Colorado pikeminnow live in home ranges that may comprise several miles of river. They can migrate long distances between home ranges and spawning locations, returning to their original river sections after reproducing. Despite living in muddy water with limited visibility, Colorado pikeminnow can prey upon other fish one-third to one-half their body lengths.
The Colorado pikeminnow is a member of the minnow family that historically may have reached lengths up to 6 feet (1.8 meters). The longest individual captured in recent years was about four feet (1.24 meters). Colorado pikeminnow have long, streamlined bodies, with their heads comprising up to 25% of total length. Their heads are somewhat flattened, and their jaws have thick lips with no teeth.
Historical accounts of this species recorded weights to 88 pounds (40 kilograms)
Pikeminnow are silvery-white, with creamy-white bellies. In spawning condition, they develop tubercles--rough bumps that feel like sandpaper-- along their heads.
Colorado pikeminnow grow relatively slowly and reach sexual maturity at five-to-seven years of age and lengths greater than 1.5 feet (450 millimeters). Adults establish home ranges where they can move relatively short distances between feeding and resting areas. Juveniles typically occupy lower river sections for several years, gradually moving into more upstream areas with abundant prey to establish home ranges.
Researchers have estimated Colorado pikeminnow can live more than 50 years in the wild.
Colorado pikeminnow move to spawning areas in late spring and reproduce in the weeks around the summer solstice (mid- to late-June), depending on temperature and water flow. The adhesive eggs and newly hatched larvae remain in spaces between spawning cobbles, where oxygen-rich water flows between the rocks. After about a week, larvae swim up into river currents to be carried downstream into nursery habitats in slow-moving backwaters.
There are three other species of pikeminnows, all found outside the Colorado River basin. These are the northern, Sacramento, and Umpqua pikeminnows, which are found in western U.S. rivers along the Pacific coast. The other pikeminnows are not listed under the Endangered Species Act. As members of the family Cyprinidae, chub species in the Colorado River basin are relatives of the Colorado pikeminnow that can exhibit similar traits, but they do not attain the large sizes of the Colorado pikeminnow.
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