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<br />.' <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />,. <br /> <br />:-; <br />'. <br /> <br />16 <br /> <br />Colorado Sauawfish Activitv in the IS-mile Reach <br /> <br />Migration <br /> <br />Radiotelemetry studies show upstream and dawnstream movement af adult Colorado <br />squawfish in the mainstem Colorado River. The most dramatic movement was <br />exhibited by a fish implanted with a radio transmitter at Gypsum Canyon in <br />upper lake Powell on AprilS, 1982. The fish was contacted next in the lower <br />Cataract Canyon area on July 9. The next contact was made above the <br />Blackrocks area of Ruby Canyon, some 160 miles upstream. The movement was <br />accomplished in 41 days and believed to be related to spawning. At the end of <br />September of 1982, this fish was located on the Colorado River in the vicinity <br />of Clifton, Colorado (RM 178), nearly 200 river miles from its farthest <br />documented downstream location. <br /> <br />Most radio-tagged fish in the Colorado River have not displayed such dramatic <br />migratory behavior. Radiotelemetry studies conducted by the Colorado River <br />Fishery Project (Project) from 1982-85 (Miller et al 1982, Archer et al. <br />1986a), which focused on upstream reaches of the Colorado River in and around <br />the Grand Valley, provide the best indication of use of the IS-mile reach by <br />Colorado squawfish. Of the 34 radio-tagged fish that were initially captured <br />upstream from Blackrocks, 15 (44 percent) occupied the IS-mile reach above the <br />confluence of the Gunnison River at one time or another during the field <br />season. Movement of these fish during a field season was generally limited to <br />25-30 mil es. <br /> <br />During 1986 the Project radiotelemetered three adult Colorado squawfish <br />collected from the IS-mile reach above the Gunnison River in June (Kaeding and <br />Osmundson 1987). The fish exhibited a diversity of localized movement but <br />spent a major part of the next 6 months in the reach upstream of the Gunnison <br />River. Two remained in the reach throughout the estimated spawning period. <br /> <br />Spawning Activity <br /> <br />A suspected prespawni ng aggregation of adult Colorado squawfi sh was observed <br />by the Project personnel at RM 178.3 in the IS-mile reach above the Gunnison <br />confluence in mid-July, 1982. In the first observation, three radio-tagged <br />fish were tracked to the same riverine pool area, and nine adults at or near <br />spawning condition were handled after limited net sampling efforts. The <br />aggregation occurred a few days after mean daily water temperature had reached <br />20 degrees C and during a time when runoff flows were dropping off sharply. A <br />second aggregation was noted at RM 175.3 12 days after the initial <br />observation. Drifting trammel nets through an area occupied by two fish <br />equipped with transmitters yielded an additional male Colorado squawfish in <br />spawning condition. During this same time period, an adult female was <br />captured near RM 175 that weighed nearly one pound more than when previously <br />captured a month earlier, suggesting the development of spawning (gravid) <br />cond it ion. <br /> <br />~ larval Occurrence <br /> <br />Project studies include the routine sampling of the larval-fish community both <br />within and downstream of the IS-mile reach. During 5 years of the Project <br />