North Platte River Fish Survey Casper to the Nebraska State Line

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North Platte River Fish Survey - March 1999 Page 23 without difficulty. However, the drop of several meters and the velocity of the current caused a large number of walleye to "stack up" below the dam. It is unknown whether this is a passage barrier to walleye, or merely causes a delay before fish move upstream. A total of 499 individuals of 12 species was captured. This site had the highest CPUE of any of the raft sample sites at 5.45 fish/minute. Walleye - comprised 37 percent of the catch, with sizes ranging from 340 to 640 mm TL. Males were observed to be freely expressing milt, while females were observed with large bellies, but we were not able to express eggs. This was clearly a spawning run. Common carp comprised 25 percent of the catch, shorthead redhorse 18 percent, sand shiner 10 percent, and longnose sucker 5 percent. We also caught smaller numbers of white sucker (1.6 percent), red shiner (2 percent), emerald shiner (0.8 percent),-and longnose dace (0.4 percent). Three new species were encountered —creek chub (Semotilus atromaculatus) (0.2 percent), flathead chub (Platygobiogracilis) (0.8 percent), and yellow perch (Perca flavescens) (0.6 percent). Figure 15 is the study site map and Figures 16 and 17 show the habitat and sampling activities. Glendo Dam to Guernsey Inlet. —The river below Glendo Dam is largely dewatered (about 10 cfs) after the irrigation season. All three sites were sampled with the backpack electrofisher. The entire width of the river channel was sampled. During the irrigation season, water deliveries are made down the river channel resulting in unusually high flows. Three backpack samples were conducted in this reach. Glendo Dam Outlet at the Mouth of Sand Draw - Backpack.—= Of the 19 sites sampled, this had the largest variety of boulders and cobbles, which composed an estimated 90 percent of the substrate. Primary habitat is classed as main channel, with secondary habitat consisting of 60 percent run, 20 percent pool, and 20 percent rapids. Sampling began in the river channel at the mouth of Sand Draw immediately upstream of a deep pool, and continued upstream 100 m. A total of 188 individuals of 10 species was captured. The catch was dominated by longnose dace (59 percent), followed by juvenile and subadult longnose sucker (16 percent), juvenile and adult emerald shiner (14 percent), and subadult and adult white sucker (3 percent). We also captured four young rainbow trout (2 percent), a brown trout (0.5 percent), and a juvenile channel catfish (0.5 percent). The only plains killifish (Fundulus zebrinus) of the sampling effort was captured here, a 52 -mm TL individual, as well as a stonecat. Figure 18 is the study site map and Figures 19 and 20 show the habitat and sampling activities. Bull's Bend - Backpack. — Permission was obtained from the landowner to sample a 200 -m section of the river. About 70 percent of the substrate consisted of a mix of large and small cobbles intermixed with sand (10 percent), fine gravel (5 percent), and silt (5 percent). We observed and netted very few fish in this habitat and saw none in a 1 -m -deep pool. However, the substrate in the top 50 m of this site consisted of a 50 percent mix of large, medium, and small boulders lying adjacent to a deep pool (which we did not sample). Most of the fish captured in this location came from the boulders along the edge of the pool. A total of 68 individuals of Results