Book excerpt: The Colorado River had one of the most unique fish communities in the world. Seventy-five percent of those species were found nowhere else in the world. Settlement of the lower basin brought dramatic change to both the river and its native fish. Those changes began more than 120 years ago as settlers began stocking nonnative fishes. By 1930, nonnative fish had spread throughout the lower basin and replaced native communities. All resemblance of historic river conditions faded with the construction of Hoover Dam in 1935 and other large water development projects. Today, few remember what the Colorado River was really like. Seven of the nine mainstream fishes are now Federally-protected as endangered. Federal and state agencies are attempting to recover these fish. However, progress has been frustrated due to the severity of human impact. This report represents testimony, old descriptions, and photographs describing the changes that have taken place in hopes that it will provide managers, biologists, and the interested public a better appreciation of the environment that shaped these unique fish.