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<br /> <br />1 <br />1 <br />1 <br /> <br /> <br /> <br /> <br />I <br /> <br />t <br />1 <br />1 <br /> <br />t <br /> <br />t <br />Northern Hike observations (Winter 1) <br />During fall and winter of the first year of the study, seven northern <br />pike were radiotagged. observations were made on these fish only while we were <br />radiotracking squawfish. We did not search for pike until we located a <br />squawfish. Using this procedure we encountered four of the seven northern <br />pike in areas used by squawfish. Northern pike used similar habitat types as <br />squawfish during the winter months. However, northern pike and squawfish were <br />not observed to remain in close proximity (within 5 m) of each other although <br />they were in the same habitat type. Squawfish were observed to remain in very <br />close proximity to each other on several occasions. Like squawfish, northern <br />pike ramined in specific river segments during the winter and were locally <br />active (moving about within and between habitats in their preferred river <br />segments). Northern pike used backwater, embayment and shoreline habitat. <br />Mean total depths selected in backwater and embayment habitats were 3.7 and <br />3.5 feet respectively. This compared to 3.4 foot average total depth selected <br />by squawfish for these habitat types. Mean velocity utilized by northern pike <br />in these habitats was 0.05 ft/s .ranging between 0.0 and 0.4 ft/s. This <br />compared to a mean of 0.1 ft/s and a range of 0.0 to 0.2 ft/s. On occasions <br />when squawfish and pike were observed using the same backwater or embayment <br />habitat type, squawfish often used the shallower inside portions with gravel <br />substrates, while the pike remained out in slightly deeper areas with silt and <br />sand substrates. <br />Radiotradung of northern pike was conducted to add assurance that the <br />behavior and habitat observations made on Colorado squawfish were not being <br />influenced by the presence of northern pike. our observations indicated that <br />squawfish behaved in a similar manner regardless of the presence of <br />radiotagged northern pike. Ous requires the assumption that additicaial <br />northern pike were not present to influence behavior. Intensive fall sampling <br />of study areas made the presence of additional pike unlikely. More detailed <br />information on northern pike behavior and habitat use during the entire study <br />is available from the Colorado Division of Wildlife, Aquatic Research Group, <br />Fort Collins, Colorado. <br />Winter flow determinations and recoamnendations <br />State discha= relationships with ice cover <br />During Winter 2, the relationship between stage and discharge was <br />investigated by comparing water surface elevation change to changes in <br />discharge. Results of main channel measurements at NU 81.1 are presented in <br />Figures 1". The lowest discharge measured was 142 cfs on December 15, and <br />the highest was 340 cfs on March 3. As the winter progressed, flows tended to <br />increase, as did water surface elevations until March 15. Discharge decreased <br />only 10 cfs from the previous trip, but water surface elevation dropped 0.4 <br />feet. <br />Similar comparisons were made for an embayment adjacent to the cross <br />section at RMI 81.1 (Figures 19a-g). Ice thickness increased from 0.85 feet <br />December 15 to 2.12 feet March 15. Water surface elevations increased <br />throughout the winter compensating for the corresponding increase in ice <br />thickness, resulting in relatively stable effective depth. Effective depth <br />45 <br />