Distribution of Fishes in the Dolores and Yampa River Systems of the Upper Colorado Basin

Abstract

Fish sampling was conducted in the Dolores River, Colorado, in 1971 and the Yampa River system of Colorado, 1968-71 with emphasis placed on iare and endangered species. Eleven species were found in the Dolores River, but no rare and endangered forms were collected. Twenty-two species were collected in the Yampa River system, including four rare and endangered forms: Colorado squawfish (Ptychocheilus lucius), humpback chub (Gila cypha) bonytail chub (Gila elegans) and humpback sucker (Xyrauchen texanus). The Yampa system appeared important to reproduction and preservation of Colorado squawfish. The native fish fauna of the Colorado River basin represents one of the least understood groups of fishes native to a major North American river basin. Reasons for this are the rugged terrain surrounding the Colorado River and the low economic and sport value placed on these species. The Colorado River has in the last 50 years been greatly desecrated, with much of the system either dry or ponded into great reservoirs. These factors have greatly limited the available habitat for native fishes. Several species are now rare and endangered. Colorado squawfish (Ptychocheilus lucius) and humpback chub (Gila cypha) are presently considered rare and endangered by the U. S. Department of the Interior (1968). The humpback sucker (Xyrauchen texanus) and bonytail chub (Gila elegans) are very rare also (Miller 1972). The native fish of the Colorado River system can be separated into two groups: (1) large river forms found in main channels of the Colorado River, Green River and larger tributaries, and (2) small stream forms found primarily in the lower basin (Nevada, Arizona) in small streams and springs. Minckley and Deacon (1968) reviewed the status of native fishes in the lower Colorado basin (below Grand Canyon). They concluded that large forms are virtually extinct in the lower basin. Therefore, the upper Colorado basin remains th2 only refuge for these unique fishes. This paper is concerned with the Yampa and 1 Portion of a doctoral dissertation written at Utah State University.