 The Colorado River had experienced natural flooding before the construction of the Hoover Dam . The dam eliminated the natural flooding , which threatened many species adapted to the flooding , including both plants and animals . The construction of the dam devastated the populations of native fish in the river downstream from the dam . Four species of fish native to the Colorado River , the <unk> <unk> , Colorado <unk> , <unk> <unk> , and Razorback <unk> , are listed as endangered . 
