The Colorado River and its tributaries are one of the world's most spectacular river systems. From its headwaters in the mountains of Colorado and Wyoming, the river drops more than two miles on a 1,700-mile journey to the Gulf of California. The water becomes thick with sediment as it passes through the red rock canyons of the Colorado Plateau, and seasonal flow varies greatly. Before dams were built, flows ranged from a few thousand cubic feet per second to nearly 400,000 cubic feet per second.Historically, only 14 species of fish inhabited the upper Colorado River basin, but over 40 non-native species have been added since the late 1800s. The native fish species in Canyonlands are primarily carp, minnows and suckers, and many are not found anywhere else. These include the Colorado pikeminnow (formerly squawfish), razorback and flannelmouth sucker, as well as humpback and bonytail chub.
There are several different niches within the underwater world of rivers. Razorback suckers and humpback chub prefer turbulent, swift water. Bonytail chub live in calm backwaters and eddies. Pikeminnows spawn in backwaters but roam throughout the river in search of food. Until recently, pikeminnows were the dominant fish. Growing up to six feet long and weighing over 100 pounds, they could eat almost anything. The pikeminnow was called "Colorado salmon" by early settlers, probably because it migrated up to 200 miles through extreme white water to find its spawning grounds each year. Today, non-native fish dominate the rivers. One study done at the Confluence in Canyonlands found 95 percent of the fish to be non-native. Carp and channel catfish are the most commonly seen. Carp are native to Asia and were hailed as the greatest food fish ever by the U.S. Bureau of Fisheries. Catfish are known to eat the young of several native species and have played a significant role in the decline of native fish populations.
In the past few decades, the Colorado pikeminnow, razorback sucker, humpback and bonytail chub have all been listed as endangered species.