Stocking trout wild trout streams is extremely harmful because of the impact it has on genetic variation. There are three trout species native to Colorado; the Colorado River Cutthroat, the Greenback Cutthroat, and the Rio-Grande Cutthroat. All three of these species were a product of the Pleistocene epoch: a turbulent time when enormous glaciers covered the northern border and into the western and eastern borders of Colorado. During these glacial periods, the ice front advanced and retreated in pulses, each lasting many thousands of years. With each advance, the courses of rivers and streams were shifted from north to south. It was during these periods of retreat that our great rivers were formed. Ice would melt and the water would be carried
