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<br />METHODS <br /> <br />Trips and Participating Personnel <br /> <br />Four fish monitoring trips were carried out in the LCR during 2004. The trip <br />dates were: (1) 29 March to 9 April (referred to as the April trip henceforth), (2) <br />26 April to 7 May (referred to as the May trip henceforth), (3) 15 to 26 <br />September, and (4) 20 October to 31 October. Participating field crew included <br />personnel from USFWS, Arizona Game and Fish Department (AGFD), SWCA <br />Inc., and volunteers (Table 1). <br /> <br />Study Site <br /> <br />All work was conducted in the lower 13.6 km of the LCR, below a large <br />travertine structure known as "Atomizer Falls". Note this year an updated <br />photographic map provided by GCMRC was used which slightly modifies river <br />kilometers. For example, previous USFWS reports since 2001 have defined the <br />sampling reach for mark recapture studies as occurring in the lower 14.2 rkm of <br />the LCR (e.g., Coggins and Van Haverbeke 2001, Van Haverbeke and Coggins <br />2002, Van Haverbeke 2003). The new maps define the sampling reach as <br />occurring in the lower 13.6 rkm of the LCR. <br /> <br />During the course of each trip, the LCR was divided into three reaches by river <br />kilometer (rkm) with base camps located within each reach. Rkm within the LCR <br />began with zero at the confluence with the Colorado River. Base camps were <br />established for the Salt reach, Coyote reach and Boulders reach at 10.4 rkm, 5.0 <br />rkm, and 1.9 rkm, respectively (Figure 1). Each reach was divided into three <br />sub-reaches. Salt reach was divided into three sub-reaches as follows: 13.6 to <br />12.3 rkm (Lower Atomizer Falls to Triple Drop), 12.3 to 11.2 rkm (Triple Drop to <br />Hell Hole), and 11.2 to 9.6 rkm (Hell Hole to above House Rock). Coyote reach <br />was divided into three sub-reaches: 9.6 to 8.0 rkm (above House Rock to <br />Redbud Canyon), 8.0 to 6.5 rkm (Redbud Canyon to above White Spot), and 6.5 <br />to 5.0 rkm (above White Spot to 5.0 rkm). Boulders reach was divided into three <br />sub-reaches: 5.0 to 3.0 rkm (5.0 rkm to above Powell Canyon), 3.0 to 1.8 rkm <br />(above Powell Canyon to above Jump Off Rock), and 1.8 to 0.0 rkm (above <br />Jump Off Rock to Confluence). <br /> <br />Gear <br /> <br />Unbaited hoopnets were deployed to sample fishes (0.5 - 0.6 m diameter, 1.0 <br />m length, 6 mm [1/4"] mesh, with a single 0.1 m throat). Sixty hoop nets were <br />fished throughout each of the three reaches during each trip. Nets were <br />distributed throughout each reach by fishing equal numbers of nets within each <br />sub-reach (i.e., 20 nets were fished within each sub-reach). Each sub-reach was <br />fished for three consecutive 24 hour periods (i.e., three days each). Some very <br />minor exceptions to this rule were made to accommodate logistics. In addition, <br />each hoop net was positioned in favorable habitat suspected of yielding catches <br /> <br />13 <br />