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<br />DRl\FT <br /> <br />a <br />c <br />(~~ <br />\.i.) <br /> <br />2,0 BACKGROUND <br /> <br />CJi <br />~ The San Juan River sub-basin is the second largest in the Upper Colorado River <br /> <br />Basin and drains approximately 38.000 square miles, (See Figure 2-A) <br /> <br />The San Juan River originates in the San Juan Mountains in Southwestern <br />Colorado. It flows some 31 miles to the New Mexico stateline, 190 miles to <br />the Four Corners area and on to Lake Powell another 136 miles downstream in <br />Utah. <br /> <br />2.1 NATIVE FISH FAUNA <br /> <br />Providing a home for nine native as well as numerous exotic fishes. the San <br />Juan continues to provide habitat for one listed endangered species. the <br />Colorado squawfish. and one species proposed for listing as endangered. the <br />razorback sucker. The bony tail chub, now listed as endangered. was <br />historically present in the San Juan but now appears to be extirpated from the <br />system (Platania, 1991). <br /> <br />Despite sporadic reports of its presence in the San Juan. the Colorado <br />squawfish was not confirmed in collections until July 4, 1936 when 3 specimens <br />were captured 32 miles upstream from the Colorado River confluence. Recent <br />surveys by State and Federal biologists (1988-1989) have added 10 adult and 19 <br />juvenile and young-of-year squawfish to historical collections. The range of <br />collection and therefore probable extent of distribution includes the <br />confluence area of Lake Powell upstream to Shiprock. <br /> <br />Second hand reports of razorback sucker in the San Juan can be traced back as <br />early as 1891 (Jordan). However, the first verified report of the species in <br />the San Juan River basin carne in 1976 when two razorbacks were taken from an <br />irrigation pond near Bluff. Utah. Recent surveys indicate only one razorback <br />collected from the San Juan River near Bluff. but comparatively large numbers <br />(27) of reproductively mature adults were found in the Upper San Juan Arm of <br />Lake Powell near Piute Farms. <br /> <br />6 <br />