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two periods was not significant. Trout abundance declined rather rapidly downstream and by <br />reach LD4 trout were < 10% of the fish community. Salmonid abundance increased slightly in <br />WH2 because of fish moving from the abundant Jones Hole Creek population. <br />Brown trout population size structure in Lodore Canyon differed among the two periods <br />In 1994 to 1996, a wide variety of sizes were present and the most abundant size classes were <br />usually the intermediate 251 to 400-mm TL size classes (Fig. 25). In 2002 to 2004, we also <br />captured a wide variety of sizes of brown trout, but two size groups dominated samples. The <br />smaller size group was composed of size-classes that were 151 to 250 mm TL, and the second <br />was composed of fish in the 351 to 450-mm TL size classes; fish of intermediate size were <br />present but less common. Even the relatively small samples from reach WH2 showed a similar <br />bimodal pattern. <br />Red shiner expanded their distribution and were more abundant in the upper portions of <br />the study area in the 2002 to 2004 sampling period compared to 1994 to 1996 (Fig. 26). In 1994 <br />to 1996, red shiner was absent from Browns Park and Lodore Canyon reaches LD 1 to LD3, but <br />were common in LD4. Red shiners were not present in the upper extent of the study area in <br />2002, but invaded Browns Park in 2003, and increased in abundance in all Lodore Canyon <br />reaches. Relative abundance and density of red shiner was high in Whirlpool Canyon reaches <br />and in Island-Rainbow Park in 2002 to 2004. <br />In spring and summer 2003, red shiner was abundant in lower Lodore Canyon, rare or not <br />present in upper Lodore Canyon, and in low abundance in newly invaded Browns Parl, with two <br />specimens captured in spring and four in summer 2003. By autumn 2003, we documented red <br />shiner throughout Browns Park from just upstream of Swinging Bridge (RK 612.8) downstream <br />through Lodore Canyon. Red shiner was often the most abundant species in seine samples in <br />Browns Park in autumn 2003, particularly in backwater habitat. Adult and juvenile size classes <br />were present, which suggested successful reproduction by that species in that reach. In 2004, we <br />did not observe red shiners upstream of Lodore Canyon in spring, summer, or autumn, a pattern <br />similar to that observed in 2002 and from 1994 to 1996. <br />32