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• range and is classified as endangered by FWS under the Endangered Species Act of 1973. The razorback sucker is rare but currently receives no Federal protection. It is, however, listed as endangered by the State of Colorado, ,protected by the State of Utah, and is a candidate for listing under the Endangered Species Act. 2. The Colorado squawfish is a predator and is the largest cyprinid fish native to North America. Historically, it reached weights of 80 pounds in the lower Colorado River basin. However, the largest adults captured in recent years weigh between 10 and 15 pounds and are about 3 feet long. Colorado squawfish now only occur in about 800 river miles in the upper Colorado River basin above Lake Powell, Utah. Subadult and adult squawfish sometimes exhibit long-distance movement to habitats essential to different life stages of the fish. Migration of over 200 miles has been documented. Most migration has occurred near or during the spawning period and included movement to and from spawning areas. 3. The largest razorback suckers reach lengths up to about 18 to 24 inches and weigh about 5 pounds. This catostomid species is in a tenuous position in the upper Colorado River basin, perhaps more so than the Colorado squawfish. Only adult razorbacks have been collected in recent time, and there is no evidence of successful natural recruitment to the population. The low population size and apparent lack of recruit- ment suggest razorbacks may be close to extinction. Razorback suckers also show tendencies to migrate, although little is known about the extent and range of their movements. 4. FWS is mandated by provisions of the Endangered Species Act to provide conservation measures to protect and perpetuate these fishes and enhance their habitat. An important goal of this effort is to restore their species to enough of their former range so that their popu- lation numbers are no longer declining. The ultimate goal is to increase the population to a level that allows their removal from the Endangered Species list. 5. Dams and irrigation diversions on main stem rivers and their tributaries constructed in conjunction with water projects are impediments to upstream movement of adult Colorado squawfish and razor- back sucker. Barriers that block stream passageways contribute to the loss of historic habitat for these fishes and possibly their decline, and may be one factor that led to loss of Colorado squawfish in the lower Colorado River basin below Glen Canyon Dam. 6. Fish passageways around such migration barriers have been • constructed for and used successfully by other species in other river systems. No passage facilities have been constructed in the upper 3