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<br /> i <br />h <br /> n s <br />arp contrast to the more widely used technique of surgically implanting radio <br /> transmitters. This method can lead to substantial fish mortality due to chronic infection <br /> of the abdominal dermis surrounding the exit hole created by the trailing whip antenna. <br /> However, some of the new transmitters employ an internal, coiled antenna that eliminates <br /> the exit hole but also decreases the detection distance. Implanted transmitters will remain <br /> inside fish for the remainder of their lives, while externally attached transmitters will <br /> likely be shed soon after the research project is complete. <br />~' <br /> Immediately following transmitter attachment, fish were alternately assigned to be either <br /> control or experimental treatment. A block net was placed at the mouth of Millard <br />Bottom backwater, and experimental fish were released behind the blocking net and <br /> confined to the backwater while control fish were placed adjacent to the blocking net on <br /> the river side. Due to time and boat limitations, transmitters were only attached to 15 <br />suckers (7 experimental, 8 control) and released on the evening (1815 to 2003 hrs) of <br /> June 16, while the remaining fish (8 experimental, 7 control) were released the next <br /> morning (0900 to1047 hrs). The block net was removed at 0640 hrs on June 19. Thus <br /> the period of time that the first seven experimental fish spent in the backwater (~ 2.5 <br /> days) was greater than the second group of eight fish (~1.9 days). <br />Tracking Design and Effort <br />Razorback sucker positions were recorded using a 40-MHZ ATS© receiver, a whip <br />antenna, and ahand-held directional loop antenna. The previously mentioned National <br />Pazk Service 5.5-m Achilles inflatable boat with a 60-hp jet outboard was used <br />throughout the summer for surveys. For each fish located, the RK was recorded and <br />habitat was described (see next section). <br />The study site was in Canyonlands National Park, Utah, and extended into the Colorado <br />and Green Rivers outside of the park (Figures 1). Twenty-two field surveys were <br />conducted between June 24 and August 13 (Table 1). Thirteen of the 22 surveys <br />repeatedly surveyed 3 reaches of river that were observed to contain radio-tagged <br />razorback sucker. The first of these reaches was Mineral Bottom (RK 81.7) to Spanish <br />Bottom on the Green and Colorado Rivers. Spanish Bottom is located 6.4 km below the <br />confluence of the Green and Colorado Rivers and lies 0.75 km upstream from the start of <br />Cataract Canyon rapids. The Mineral Bottom to Spanish Bottom section was surveyed <br />five times (June 24 and 30, July 9, and August 5 and 7). The second reach was Potash <br />boat dock (RK 77.1) to Spanish Bottom on the Colorado River. Potash to Spanish <br />Bottom was also surveyed five times (July 1, 8, 13, and 30, and August 13). The third <br />reach was on Lake Powell from Hite Marina (RK 270.6) to the base of the Cataract <br />Rapids at Imperial Canyon (RK 322). The river kilometer "zero point" below the <br />confluence of the Green and Colorado Rivers is at Lee's Ferry; the confluence is <br />~. considered to be RK zero if you are upstream in either the Green or Colorado Rivers, or <br />5 <br /> <br />