7066 - Laserfiche WebLink

Home Browse Search

Colorado River Cutthroat Trout Salmo ctarki pleuriticus Status Threatened on Colorado state list. Rare through- out its original range. Distinguishing Features The cutthroat trout that is native to the upper Colorado River basin can be distinguished from non- native trout by its red or orange slash marks beneath the lower jaws and by the spotting pattern. Rela- tively large spots, rounded in outline and typically concentrated on the posterior part of the body, characterize the native cutthroat trout. The native trout has the hereditary basis to develop brilliant coloration, but the color pigments must be derived from its food. Thus, a native trout living in a lake with crustaceans (water fleas, "shrimps," etc.) ex- presses bright red, orange, and golden-yellow colora- tion when sexually mature, but the same fish living in a small stream with only insects in its diet is more dully colored. The cutthroat trout species is made up of about 15 subspecies or geographical races distributed widely throughout the western United States and western Canada. The Colorado River cutthroat is a geogra- phical race that has been isolated in the upper Colorado River basin. It is closely related to the greenback cutthroat trout native to the headwaters of the South Platte and Arkansas River basins, and to the Rio Grande cutthroat trout. There are no consis- tent differences that can separate all Colorado River cutthroat trout from all greenback cutthroat trout except for geographical distribution -- one is native to the Colorado River basin, the other to the South Platte and Arkansas basins. Hybrid populations between the native trout, rainbow trout and non-native subspecies of cutthroat trout are much more common than are pure populations of native trout. Life History There are no obvious ecological differences between the Colorado River cutthroat trout and other trout species in feeding, spawning, optimum habitat, etc. In tolerance of environmental disturbance, the cutthroat trout is like the canary in the mine -- it is usually the first species to go. Spawning occurs in the spring, when water tem- peratures reach about 450 F. The female digs out a nest in gravel in flowing water. After fertiliza- tion, the eggs are covered with gravel and left to hatch later in the summer. Like most trout species, the cutthroat is opportunistic in its feeding. A wide range of invertebrate animals are eaten and the larger cutthroat trout prey on fish if they are available. The largest size attained by this sub- species is not known but probably was about 15 pounds. In small streams, however, few cutthroat trout exceed a length of 10 inches. 27