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104 <br />MODDE ET AL. <br />Gorge <br />Flaming <br />Gorge <br />WYOMING <br />UTAH \ <br />Y <br />Duelwane <br />River <br />COLORADO <br /> <br />1-11 Colorado <br /> River <br /> Gunnison River <br />Spawning <br />• <br />Sftes <br />Common <br />80 Kilometers <br />- Rare 80 Mlles <br />Lake <br />Powell <br /> San Juan <br /> River <br />ARIZONA <br />NEW MEXICO <br />FIGURE 1.-Map of the upper Colorado River basin showing the abundance and the known spawning locations of <br />razorback sucker. <br />and flannelmouth sucker Catostomus latipinnis. No <br />riverine razorback sucker spawning sites in the up- <br />per Colorado River have been identified recently <br />above Grand Junction. <br />Information on the historic distribution of the <br />razorback sucker in the San Juan River is sparse. <br />Anecdotal reports from as late as 1960 indicated <br />razorback sucker as far upstream as Farmington, <br />New Mexico. Earlier reports (1891) of "humpies" in <br />the Animas River near Durango, Colorado, sug- <br />gested that the razorback sucker may have occupied <br />this tributary of the San Juan River as well (Platania <br />1990). In 1961 preimpoundment rotenone applica- <br />tions in the Navajo Dam area killed fish 64 km <br />downriver to Farmington. However, no razorback <br />suckers were documented among those fish killed <br />(Olson 1962). The first verified collection of a ra- <br />zorback sucker in the San Juan River basin was in <br />1976 when two adult fish were seined from a pond <br />near Bluff, Utah. According to local residents, 100- <br />250 juvenile razorback suckers were stranded and <br />died when a nearby pond was drained in 1976. <br />These ponds were connected to the river via a canal <br />(Minckley et al. 1991). Between 1987 and 1989, 16 <br />adult razorback suckers were collected from the San <br />Juan River arm of Lake Powell. In 1988, one adult <br />razorback sucker was captured in the San Juan <br />River near Bluff, Utah, close to the 1976 pond <br />capture site (Platania 1990). No larval or juvenile <br />razorback suckers have ever been documented in <br />the San Juan River and no potential spawning sites <br />have been identified. Intensive riverwide sampling <br />of the river fish community for all life stages from <br />1991 to 1993 has failed to collect razorback sucker <br />(D. Ryden and F. Pfeifer, U.S. Fish and Wildlife <br />Service, unpublished data). <br />Razorback sucker adults are flexible in their hab- <br />itat use. Although these fish apparently evolved in