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~ { <br />embayments (backwaters) and they occurred most frequently (80%, N = 5,043) in <br />backwaters that were relatively warm (x = 15.0°C upper; x = 19.0°C J2ower Green <br />River), deep (x = 42 cm lower; x = 34 cm upper), large (x = 1,158 m upper; x <br />= 494 m2, lower) and turbid. Abundance and size of young Colorado squawfish <br />in the Green River were inversely correlated with high releases from Flaming <br />Gorge Dam, which inundated backwater habitats. We were unable to detect <br />overwintering mortality by comparing seine catches of the fish in autumn and <br />the following spring (Preliminary Abstract). <br />Report 2- Diel Movements and Habitat Preferences of Young Colorado squawfish <br />(Tyus, in prep). <br />Young Colorado squawfish (N=1,127) were captured, fin-clipped, and <br />released in the Green River of Utah in April, October, and November, 1980-81. <br />Recaptures of 23% of the fish demonstrated extensive diel movements between <br />backwaters and other shoreline habitats. The young fish were most abundant in <br />backwater habitats in afternoon when water temperatures were highest (>l0oC), <br />and virtually absent in them at dawn when temperatures were lowest (<10°C). <br />The most abundant fish species collected with the young Colorado squawfish <br />were the red shiner Notropis lutrensis and fathead minnow Pimeahales promelas, <br />and numbers of these fishes also varied with temperatures and time of day <br />(Preliminary Abstract). <br />Study 2: Winter Habitat and Flows for Adult and Young Colorado squawfish, and <br />Adult Razorback Sucker. <br />Report 3- Winter Habitat Study of Endangered Fish-Green River. Wintertime <br />Movement and Habitat of Adult Colorado squawfish and Razorback Suckers <br />(Valdez and Masslich 1989). <br />Adult Colorado squawfish and razorback suckers in the Green River <br />overwintered in specific regions, generally less than 4.8 km long. Maximum net <br />movement by an adult radiotagged Colorado squawfish during year 1, (December <br />1, 1986 through March 31, 1987) was 35.52 km upstream. Seven of the ten <br />radiotagged Colorado squawfish remained within a 4.8 km reach of river. <br />Maximum net movement during year 2 (1987-88) was 41.44 km downstream. Eight <br />of the nine fish remained within a 3.2 km reach. We conclude from these <br />observations that the majority of overwintering adult Colorado squawfish <br />remained with a 3.2 to 4.8 km reach of the river. <br />Maximum net movement by an adult radiotagged razorback sucker during the <br />first winter period was 16.8 km downstream. Six of the eight radiotagged fish <br />remained within a 1.6 km reach of the river. Maximum net movement during the <br />second winter period was 11.68 km upstream. Six of the nine fish remained <br />within a 4.8 km reach. We conclude from these observations that the majority <br />of overwintering adult razorback suckers remained within a 1.6 to 4.8 km reach <br />of river. <br />Overwintering adult Colorado squawfish and razorback suckers exhibited <br />local diel movement ... the majority of overwintering adult Colorado squawfish <br />moved at rates of 15-23 m/h within an occupied habitat in ice-free water, and <br />about 29 m/h under stable ice. ...The majority of overwintering adult <br />razorback suckers moved at rates of 25-31 m/h within an occupied habitat. <br />Overwintering adult Colorado squawfish and razorback suckers selected <br />specific microhabitat within low velocity habitats. ...The areas used by the <br />fish (Colorado squawfish) were characterized by average water depth of 0.762 <br />7 <br />