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<br />(~ 2.0 BACKGROUND <br />C) <br />~,,) <br />..~ The San Juan River sub-basin is the second largest in the Upper Colorado River <br />I\':'\ <br />~. Basin and drains approximately 38,000 square miles (See Figure 2-1). The San <br />Juan River originates in the San Juan Mountains in Southwestern Colorado. It <br />flows some 31 miles to the New Mexico stateline, 190 miles to the Four Corners <br />area and on to Lake Powell another 136 miles downstream in 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 also provides habitat for one listed endangered species, the Colorado <br />squawfish, and one species proposed for listing as endangered, the razorback <br />sucker. The bony tail chub, now listed as endangered, was historically present <br />in the San Juan but, now appears to be extirpated from the Basin (Platania, <br />1991) . <br /> <br />Despite sporadic reports of its presence in the San Juan. the Colorado <br />5quawfish was not confirmed in collections until July 4, 1936 when 3 specimens <br />were captured 32 miles upstream from the Colorado River confluence. Surveys <br />by State and Federal biologists in 1987-1990 added a total of 10 adult and 20 <br />young-of-year 5quawfi5h to historical observations. The range of collection <br />and therefore probable extent of distribution included the confluence area of <br />Lake Powell upstream to Shiprock. In 1991 four additional adult squawfish <br />were captured near and one observed above Shiprock, thereby expanding the <br />current range to the Hogback Diversion. <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 came in 1976 when two razorbacks were taken from an <br />irrigation pond near Bluff, Utah. Recent surveys resulted in only one <br />razorback being collected from the San Juan River near Bluff, but <br />comparatively large numbers (27) of reproductively mature adults were found in <br />the Upper San Juan Arm of Lake Powell near Piute Fa~$, <br /> <br />7 <br />