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s <br />Flannelmouth sucker were consistently more prevalent than <br />_-- bluehead sucker in electrofishing collections. Channel catfish were <br />slightly more abundant than bluehead sucker in both spring and summer <br />~ (Table 6). The relative abundances of carp and unidentified suckers <br />were not significantly different (P=0.05) between spring and summer <br />(Table 6). The relative abundances of flannelmouth and bluehead <br />suckers, and channel catfish were significantly greater in summer than <br />in spring (P=0.05; Table 6). The increase in catch rates in summer <br />was probably due to greater effectiveness of electrofishing in <br />~ shallower depths and--lower water velocities. <br />Only one rare or endangered species was found during UDWR's <br />summer electrofishing -- Colorado squawfish. Flannelmouth X bluehead <br />sucker hybrid and striped bass were only occasionally encountered in <br />both spring and summer electrofishing. Two rainbow trout were <br />~ collected during spring high flows. <br />In addition to the seasonal differences in fish abundances noted <br />above, spatial differences were also observed. There was a trend of <br />increasing relative abundances of carp, flannelmouth, bluehead and <br />unidentified suckers with relative distance upstream (Figures 4, 5, 6 <br />and 7, respectively). Relative abundance of channel catfish tended to <br />decrease with relative distance upstream (Figure 8). There is a <br />- striking difference in geomorphology of the San Juan River above and <br />below RMI 78 (i.e., between Reach Code 16 and 17). From RMI 78 <br />downstream to Lake Powell, the river is confined to a single channel <br />- within a deep canyon. From RMI 78 upstream, the river meanders <br />~ through a relatively broad floodplain and forms braided channels. The <br />average relative abundances of carp, flannelmouth, bluehead and <br />unidentified suckers were significantly greater in the upstream <br />braided reaches of the river than in the lower non-braided canyon <br />reaches (Table 7). Channel catfish abundance, conversely, was <br />significantly greater in the lower canyon reaches versus the upper <br />~ braided reaches (Table 7). Electrofishing catches of BOR in the <br />river-lake transition zone were dominated by exotic species. Channel <br />catfish was the most prevalent species in BOR collections, followed by <br />carp (Table 4). <br /> <br /> <br /> <br />~ - 17 - <br />